HPA

This is my winter project. I started it weeks ago - months, maybe: about the time that Bruce's HPA went dark.

I have now finished 'Phase 1' - the construction of a crude proof-of-concept model, and flight thereof. It's the last bit that's taken ages - mostly just one flight before wind, rain, dark or cattle stopped me, then many days before the next chance. The model could appear to want to fly, then next flight, days later, would collapse in a heap and look like it could never fly. I got a couple of approx 20 second flights, but wanted another one or two, preferably on camera, to convince me to proceed to 'Phase 2' - a properly-constructed and finished scale model. At last I have achieved several flights over the last 3-4 days, and I'm now [almost] convinced to go ahead.

The actual build of this test model was surprisingly quick, especially given the huge amount of research needed to get the shape right. More of that later.

The video,  https://youtu.be/nBDo7I6QxFM

shows seven flights over the last 3-4 days. Well - most of them are not flights, really, just crashes. I've just glued them end-to-end with no text on screen, so I'll describe them here.

1) Oops - I noticed a broken strand in the right motor while winding, but thought I might get away with it . . . err, no. You might spot the right nacelle breaking away on 'landing': that's normal.

2) The model has almost zero 'decalage' and it doesn't care whether it keeps going up . . . or keeps coming down. Perplexingly it also demonstrates good stall recovery at other times.

3)Worried by the proximity of cattle and wanting to keep 'em in sight, I didn't gauge the breeze carefully enough and launched downwind. The model didn't achieve climb-speed.

The remaining flights are all from today.

4) What was that? It's way too pitch-sensitive. I need to add noseweight but I'm too miserly.

5) See? That's what adding a tiny bit of down-elevator gets you . . .

6) Hey - it flies! (Sort of.)

7) Hey - it flies for more than twenty seconds! (Sort of.)

The still images attached are 1) A screenshot taken from video flight 6, when it happens to be straight-and-level for an unusually long time . . .about 0.14 seconds . . .:D

2;3) The model after the last flight. The last picture is an art-study, entitled 'Picture of Mossie with Moo-Cows'.

Those cattle have been really annoying. They're young, bored, and hungry. Any activity on the field gets them ready for a stampede. I could only fly today because the farmer had just spread hay on the field and they're too busy eating to worry about destroying model aeroplanes.

Stephen.

Wow what a great project Stephen. Looks like it's making good progress too from the video

That looks like a challenge to get flying, Stephen. I would imagine that twin rubber powered models would be a hand full. Two motors of slightly different power deliveries with two large props upsetting stability - definitely fun.

Young hungry cows - hope they are friendly.

John

That first picture brought me up short - I rather like it.

Very impressed that you're having a go at a Mossie; I had a NoCal Mosquito that I managed to get exactly (numbering from the left) one good, circling flight out of. All the others were all over the place, it had a mind of its own. I eventually came to the conclusion that it had not enough tail area and too much camber. I still have the props and motor sticks somewhere, your efforts are inspiring me to have another go at it.

Andy

Hullo fellows - good to see the familiar names convening again.

I have to say I don't have a clue regarding the trim of the model - like John says, I believe the power output of the motors will be slightly different, and what's more continuously varying as clumps of rubber break up, or brush the nacelle structure. The whole tail is completely blanketed by the slipstream. The sharply-tapered wingtips will want to stall (no washout). To my mind the CG looks adequately forward - but with the couple of degrees of down-elevator indicated, the wing and tail have almost the same incidence.

The reason I'm prepared to push things further is that I made a Westland Whirlwind years ago that behaved in a sedate manner. It occurs to me though that the Whirlwind had a high-set tailplane . . . might make a big difference if it's out of the propwash . . .

Yes the heifers are very friendly - but boisterous, and they'll test anything new by snuffling and licking and nibbling it - including model aeroplanes.

Andy, since I had no part in the composition of that photo - it just came about by pure happenstance - I think I can say that I like it too, without sounding conceited. The winter sun, the silhouette, the stark winter trees . . .  I hope you resurrect your NoCal model.

Stephen.

Great project Stephen, look forward to reading about the construction techniques you've used on this one.  Are the ailerons pendulum-controlled or simply adjustable?

Mike

Yes, pendulum ailerons, Mike. I think they're responsible for the wing-rocking when the model is hovering on the stall. There's probably a tip-stall and the ailerons correct, then maybe some hysteresis-type overcorrection. I have a non-scale pendulum model I made for an article in Aeromodeller Magazine, and after adjusting the pendulum setup (can't remember what I did), it flew whole flights with the wings rocking, even tho' nowhere near stalling. Kind of cute, but not very scale-looking. Pilots waggle their wings to say hullo or goodbye or whatever, but not for the whole flight! (Well, except me when I was a student, probably.)

FWIW here's a   video  (https://youtu.be/oSazIxF6pns)  from 10yrs ago (can't believe it :o ) of my Whirlwind, flying like wot a lady oughter. It was bigger than this Mosquito.

I opted to make a Mosquito test model because for me, a Mosquito was just too speculative a venture to merit a detailed, finished model from the outset. Those sharply-tapered wings; almost no dihedral; all that mass hung out on the wings creating loads of roll inertia . . . for the same reason I didn't intend to start a Mosquito thread on HPA unless and until it had flown more than say, 15 seconds, and looked capable of more.

But apart from proving basic viability, a huge advantage of a test model is that it can be flown over hard and rough ground even when untrimmed. Who cares?. All the flights of this model have been over hard-frozen or just slightly thawing ground. I'm pleased that my initial concerns over the design's ruggedness have been amply dismissed, with the cavorting model hitting hard, including one treestrike: a very low branch from which the model fell to ground. Sometimes a nacelle detaches on landing - the means of pinning them in place being very clumsy and 'afterthought' on this model. Another big worry was whether the prop blades would withstand landings. Again, yes - to my mild surprise and great relief. There has been one broken blade - in fact on flight no.3 in the video, when I launched downwind and the model accelerated onto the ground. The broken blade was the first thing to contact the ground. Luckily it snapped in a way leaving a large surface area for re-gluing and the repair took a minute or two with thin CA. See the blade lying on the worktop in the attached image.

Stephen.

DeHavilland Mosquito

Sun Jan 11 2026  10:00 AM  local time here in Windsor, Ontario, Canada.

    Hi Prosper Stephen!  Thanks so much for those videos -  it was great action there.  It is good to see those FF rubber trimming videos.    :)

    In Pic #1,  I also see about 30 blackbirds,  maybe  European "Rooks"  or  Crows (?),  content to witness those entertaining flights,  whilst sitting atop those leafless trees.

    Yes,  those cows do look menacing ....

Lastwoodsman
Richard

I think you are correct about the more efficient high mounted tail of the Whirlwind. A larger tail would certainly help but would possibly need to be much larger than scale.

A thought though - what if the tail is enlarged slightly and set at a positive angle to the fuse centre line with the wing slightly more positive - the idea being to have the tail flying a little higher above the wing wake with it's nacelles etc.

A quick test with a profile model may prove whether this is worthwhile attempting in more detail.

By the way that's a nifty freewheel setup on your prop!

Good luck.

John

Having still got my 40" span Mosquito, I can confirm that a larger tail does indeed help them to fly, but they still remain knife edge.

I added some very crude additions to increase the tailplane and tail fin area, to prove it was worthwhile perusing. That was around May 2025. It was a great success, so I made new larger tail surfaces, and even managed to make them lighter than the originals! It was so close to finally being trimmed last year, but it ended up sustaining damage (again!), got repaired and it's been sat waiting for trimming again because the weather in 2025 just wasn't in free flights favour.

Funny thing though, I've seen my Mosquito display the same characteristics in the air as your 1/24 version, despite mine not having working ailerons!

Got some better propeller blades as well for 2026, but they can wait until it's trimmed. Assume you're running counter rotating props as well?

Hi Richard, good to hear from you. Those birds - had they been birds - could well have been rooks, though more likely jackdaws. However in fact the shapes are the remains of the flowers or seed pods of the ash tree. They cling on all winter, it seems. I will keep an eye out to see when they drop - Spring, I expect.

John's and Mark's talk of enlarged tailplanes has got me scared. I'm not sure I could face that. First of all when weather and cattle allow I'm going right thru the repertoire of downthrust v. elevator; noseweight, and prop-pitch changes too, perhaps. On the face of it the tailplane is a good size - nearly 19% of wing area, which is what Monty Python would have called "lookshury". It's decently thin (about 10% thickness to root chord) and looks a decent shape in terms of efficiency.

Quote from: OZPAFset at a positive angle to the fuse centre line with the wing slightly more positive - the idea being to have the tail flying a little higher above the wing wake with it's nacelles etc.

I see what you mean John. I'm not sure that the tail could be raised a worthwhile amount without the fus. taking on a ludicrous flight attitude (and adding lots of drag). However, I don't know - perhaps only a small adjustment would 'make the difference'.

Quote from: MarkI've seen my Mosquito display the same characteristics in the air as your 1/24 version, despite mine not having working ailerons!

That's interesting Mark. Maybe it's just the inertia of the heavy nacelles then. Even absent dihedral, there is a roll-damping effect - the downgoing wing has a greater effective angle of attack, and so more lift, and obviously the reverse for the upgoing wing.

No, both props rotate clockwise. There is lots of torque, which thus far I've controlled by a fair bit of downthrust in the right prop. This trick I remember learning from Tom Arnold - he mentioned it donkey-years ago on HPA and I didn't forget despite not ever using it. As I recall the Whirlwind needed no thrustline adjustments.

Stephen.

    Hi Stephen,
                Another Beautifully made model as expected. Just to add to your list I've always found 50 or so extra winds on the outboard motor gives a twin a positive path to fly, Just a thought.
                       Dave

Thanks Dave, that's a good tip. Now that the model seems to be behaving, to some extent (see below), I'll try that.

I've made some progress :). First, lots of downthrust on both props. Second, noseweight - an arbitrary 4.5g, which happens to be the weight of a little slab of lead I found, and stuck under the nose with carpet tape. A couple of short flights indicated an improvement, tho' it was too breezy to be sure. So this morning in dead air I wound about half turns and the model climbed well and made its first steady orbit. Then with nearly full turns and with camera, the model made a much wider left-hand tour, thankfully just staying within the field boundary.

Vexingly, the video didn't 'come out'. It's really hard to hold the camera and the model in one hand - much harder than for a single-engine, because there are two props being blocked by one's fingers and constantly trying to escape - fingers that are needed for the camera too. I must have moved the zoom lever, because the vid. was not zoomed and the model was a little scrap in the distance most of the time - and what's more blurred almost totally. At this wide angle, the autofocus didn't know whether it was meant to focus on trees, clouds, model or what.

There were just 3-4 frames with the model in focus so I've attached a pic cut from one of these frames. I guess the wider angle at least gives an idea of the height reached. In both flights the model began to stall a lot towards the end, suggesting less downthrust but more down elevator.

The second flight was 27sec. The model always lands with plenty of turns still available so I'll be trying 1/4" motors instead of the current 7/32". But for now I'm at last fully convinced that it's worth going ahead with a detailed and finished model. Man, I've got to make the tail lighter! This model doesn't even have a tailcone or tailwheel and it still needs noseweight.

Stephen.

Great flight pics.  I use a gopro copy on a headband then once adjusted properly all I have to do is watch the model in flight and it pretty much stays in the focal frame.  It might look a bit ridiculous, but it seems to work.

It's good to hear that you have tamed the Mossie Stephen. It looks very atmospheric in that photo.

John

Hi pedwards - I've often thought of a gopro copy - not just for modelling - but I can't figure out how they handle data storage. I mean my portable camera can generate .mov files of multiple gigs in less than a minute at high resolution - so what happens when you gopro a 1/2hr walk in the countryside, even at medium res.?

Hi John -

Quote from: OZPAFBy the way that's a nifty freewheel setup on your prop!

top marks for noticing, but I wonder if you can divine how it works from the photo? I invented this early in my aeromodelling days, probably about the time I joined HPA. It's very unobtrusive IMO but does involve a tricky mechanical solder which I don't look forward to.

Flight Report

Yesterday had almost zero wind all day, and the cattle weren't around much. The motors had been 20" 7/32" Tan SS - 2 loops of 1/16th and one of 3/32. I replaced them with 4 16" loops of 1/16". I made some adjustment to the rudder to anticipate the extra torque but it wasn't nearly enough. On about half of the motors' safe turns the model took 2-3 seconds to rear into a barrel roll to the left, over the vertical and dive almost vertically onto the frozen ground. It bounced backward. I did that pained, wincing "oh well . . . there goes that, then" thing, but amazingly the model was hardly damaged :o. I had to repair a tailplane spar, a bit at the back of a nacelle, some cracked sheeting at the front of same nacelle, and the pendulum arm had snapped under the momentum of the 1 gram bobweight. I even had time for another try before dark - just 350 turns per motor, with the downthrust on the left motor halved, and a bit more right rudder and down elev.

That worked well. The power increase has transformed the model. It did rock its wings a bit at one point, but okay. The flight ended with a tightening right spiral though. Against the torque there's plenty of right aileron and some right rudder - so no surprise it spirals right as turns run out. I'll have to play with thrustlines to manage torque if poss. It was fairly pitch-stable, and flew at a believable speed too, so I can almost forgive the need for noseweight.

Today I gave it 400 turns and it sailed off - lovely! Except that it sailed off towards a 'built up area'. Thankfully captured by a shrub, not smashed into a wall. No damage except the right aileron needs to be hooked up to its link to the bellcrank. And the ever-increasing potential danger of me teetering at the top of a wobbly stepladder. The model was 10-12ft up.

Stephen.

Over the years I sometimes considered a Mosquito model. I would dig out my Plans Service drawing and peruse it. Nope. Not nearly enough wing for that fat fuselage and those fat nacelles. Too damn curvy. Then recently I thought what the hell, and started looking online for information and images. I noticed right away that the Mosquito 'bodies' (fuselage and nacelles) didn't look very curvy or fat. Well it turns out that yet again I was fooled by believing drawings. Surely I'd abundantly proved to myself aaayges ago that nearly every drawing out there is rubbish?

Actually arriving at a believable shape involves much much poring over many many images. The three examples attached below were very useful, and actual measurements from a NACA Report, and videos, and 'walkaround' image collections including inside views showing fuselage frames. I can't claim my conclusion is correct but it's a durn sight better than my Plans Service drawing, which I bought as a teenager, and '3-views' in books like Squadron/Signal monographs.

Stephen.

I only know of one accurate drawing for the Mosquito. I was fortunate enough to be allowed to measure certain areas of a Mosquito at the DH Museum, which were then converted to the scale that my drawings are in - perfect.

The Mosquito plan I used for my build also had the scale sized fin, wing and tailplane area.

When I remade the fin and tailplane, I also increased the depth of the airfoil section as well on the tailplane. It's a lifting tail, and oh my word did it have a massive effect. It caught us off guard and the Mossie came down heavy. Good job I've got well practiced at the repair work! Ha!

Regarding your propellers, how have you set the pitch of the blades? Are they x amount of degrees at x distance?

They use the mini sd cards so you can get a pretty large 64 gig card.  Mine came with multiple batteries so you can change out if you need more power.  The only issues I have with them is you can digitally zoom when you edit the mov but the camera itself won't zoom.  I also had one that held my phone which really looked ridiculous but took pretty good movies.  With phone you can use verbal commands. "Shoot" will take a picture.  "Start video" will take a movie.

Ah, I see. If you've got a lifting tail, then presumably it needs to have lots of area, and it also adds to the total lift, which should make for a very buoyant model. Measurements from a real Mosquito - can't beat that!

The blades are currently 26°at 75% diameter. The blades are set simply by the slots they mount into - the slots cut into the hub/spinner. Pitch can be varied by heating the blade at the root until it can be twisted, or by removal from the slot and re-working the slot to a different angle.

I hope your model finds some long grass this year.

Thanks for the info pedwards.

Stephen.

I'm making the wings first.

The wing section is RAF 34, with the 'Piercy Mod' according to NACA - but they don't tell us what that mod is. The true RAF 34 has some reflex towards the T.E. but in no Mosquito photo can I see any reflex, so I'm taking that to be the mod.

The wing section retains the same thickness/chord ratio from root to tip rib.

I used to be shy of tapered S&T wings because I couldn't get my graphics program and/or printer to scale the ribs properly. I start with one rib drawing, photograph it then upload the .jpg to my PC and open it with the graphics program. Then I duplicate the rib image and rescale it to the correct chord and thickness for its position along the wing - and so on for all the ribs. The printer would print out a page of ribs all innocent-like, but on checking them the original one in the series would be dimensionally correct but the others would all diverge from the correct taper and thickness. I've tried several times over the years.

I thought I'd give it one more go, and it worked! I use GIMP, and the scaling operation works in pixels by default. This time I chose the millimetres option, and that's what made the difference. I'd never thought to try this before because why would a computer program care what measurement units it works in? Mystery.

This time then, I printed out the rib shapes on thin paper, sprayed the back of the paper lightly with 3M Spraymount, cut each rib from the paper with scissors, then stuck each paper rib onto balsa, to be cut out with a scalpel. Then this rib was placed over more balsa to cut out its opposite-wing counterpart.*

The root rib of each wing is 1.6mm thick; 4 ribs are of 0.8mm and the rest are 0.5mm. The wood is medium/hard C-grain.

*I wrote this in a past tense as if I've done all this - but no. I'm referring to the process I used to make the test model. I've only just started this new model and cut the root ribs as per pics attached. I'll probably spend much of tomorrow cutting out the other ribs.

Stephen.

Cutting the ribs was not nearly so onerous a job as I'd feared - maybe an hour, if that. However I haven't yet cut the 657,343,556 little slots or notches to accept the multiple spars.

But first I've hit a snag. This is down to the leading-edge radiators between fuselage and engine nacelle. The long thin rectangular intakes in the leading edge have a small but characteristic cant to them, relative to the LE of the wing itself. They tilt up from fuselage to nacelle. In the test model I wasn't interested as this was one of many things not worth wasting time on, on a crude test model. Now I'm faced with trying to get it right. There are four ribs along this stretch of the wing, each one slightly smaller than the one inboard from it, but identical in shape. They have a forward extension to house the radiator. And because the radiator is canted, the curves of these forward extensions don't fair with the lines of the RAF 34 aerofoil.

Clear as gin, eh? Maybe some photos or sketches will make this clear. Will report back.

Stephen.

Stephen, keep the Mossie away from the cows.  They love balsa and doped tissue.  Something in the dope attracts them.  Lived on a farm as a kid.  My dad had a friend who flew models on our farm. Some of the cows snuck up to his car and ate one of his models that was still in the car trunk!

Gary

Thanks Gary, good story - well not so good for the aeromodeller, I suppose . . . I've noticed that the fast-growing young cattle have been extra-restive the last week or so - they charge round, head-butt each other, perform strange leaping stunts like they're trying to throw a rider, and have mass mooo-ing choruses. I think they must be reaching adolescence, in cow-years. Flying is off, what with them and the weather.

I've been kept from modelling for several days - still have a few wing ribs to finish.

Stephen.

Sun Jan 25 2026     Mosquito Build

Hi Stephen.    Here is a new video about the Mosquito. 
We have one almost restored,   in out local Canadian Aviation Museum here in Windsor,  Ontario Canada.
https://www.canadianaviationmuseum.ca/museum/aircraft/


Here is the new video:
How A Canadian "Wooden" Plane Became The Allies' Most Feared Aircraft    Jan 16 2026      23:06
https://www.youtube.com/watch?v=Nnq8pQDX5eY

Lastwoodsman
Richard

Thanks for the links, Richard.

Brrr! My workplace is around 10° lately - that's hampering my progress (Centigrade, BTW).

I feel I have to confess that my number of 657,343,556 rib notches to be cut was in fact a slight overestimate. In fact the number was about 170 - and as the ribs are cut in L/R pairs, that's 85 cuts. Huh - serves me right for using Governement Accounting software to calculate the intitial estimate.

The photos are self-explanatory, I guess. Pic 2 is staged to give an impression of how quick the notch-cutting is. Pinch the rib pair between finger and thumb, close to the cut for max. support, and stroke the razor saw backward - next!

Stephen.

Hi folks, a little progress here. I hope the work speeds up soon but things get in the way. The pic is of the 'working drawing' I made to figure out the wing for the test model. It uses rock-solid information - I have the fuselage width, the root and tip chord lengths, and the L.E. sweepback. There's lots of erasures and additions as I figured out a design. A couple of erasures and scribblings-out came because I used some info from the original Plans Service drawing I showed in post #16. Principally the trailing-edge extension of the engine nacelles (shape wrong; size wrong), and the outboard aileron rib (it's parallel to the a/c centreline, not perpendicular to the aileron L.E. as the Plans Service drawing has it).

While I think of it, the Plans Service drawing is labelled "Drawn by: XXXXX" and "Traced by: XX XXX". What's the difference between drawing and tracing?

The mainspars are of hard 0.8mm, tapering in width towards the wingtip. Pic 2 shows an assortment of tools for cutting rib slots in the trailing edge (medium 3.2mm balsa). The implement that's arrowed is a piece of thin plastic card with squares of abrasive paper stuck to either side. The last two photos show the importance of getting the ribs to fit properly in their T.E. slots. Not only can one encounter wavy-rib, but mal-positioned ribs can cause the mainspar to go wavy too - it's infectious!

Stephen.

Hi Prosper, fantastic to see your process, plese keep posting!

Pre 1980's, before the age of CAD, drawings were all done on paper by the designer in pencil. These drawings were often revised and changed through the design process, leading to what could be (depending on the fastidiousness of the designer) a pretty 'tired' looking piece of paper. Also paper is not a good archive material for a drawing that may be handled a lot and not necessarily treated very well!

When the drawing was approved by the chief designer for release, it would go to be traced, in ink on tough tracing paper, this work was often done by women. You could tell where they worked as the floor would be peppered by their heel marks where they stood at their drawing boards. (Where I worked as the floor was orange painted cork tiles). They would then 'spike' the paper drawing, which means tearing off the bottom RH corner and putting it on a spike, so everyone could tell what had been been traced. The inked tracing would be then submitted to the drawing stores. The original paper copies were destroyed.

One designer always made lots of graphite smudges on his paper drawings, so the others used a rubber to draw mushrooms in the smudges....

Malc.

Thanks malc for that thorough explanation - very interesting picture you paint.

Because work on this model has been so bitty, I haven't taken photos. I've reached the stage of glueing things together. The wing is in a simple jig that does nothing but hold the front spar (top and bottom spars in this case). I think I made this jig for a Martin-Baker MB.5 model, but it works for the Mosquito wing too.

There's a stiff strip of 0.8mm balsa fixed to a piece of white card. The strip has vertical strips alternating along its length - one behind; one in front; one behind . . . (green arrows). The spar/s are slotted into this arrangment, thus guaranteeing straightness in plan. The metal rule is just checking straightness in front elevation, and the card template is checking the angle of the ribs to the spar.

Stephen.

Today I did lots of 'spot welding' (dots of thin CA on each of the many joints in the wing); made the aileron shroud seen in pic 2, and a leading edge tip member - this is a bit of a burden at 0.2g, but has served very well in the test model, which has taken some thumping wingtip landngs without either tip breaking.

I used a long sanding block to give final shape to the ribs at the leading edge before it's sheeted, see pic 1 - actually the long sanding block is the dark thing at the bottom, propping the wing up.

Stephen.

Pic 1. shows the leading-edge sheeting bound to a mould. The sheeting is 0.6mm. I used light 0.8 or 1.0mm sheeting for the test model, to save time - but now I hope to save weight by taking the time to thin various parts. Also visible in the picture are the moulds or forms for the wingtips, along with the 0.6mm sheet blanks ready to be wetted and bound to the moulds.

Pic 2 shows the leading edge sheeting released from their binding, and 3) shows one of the wingtip sheets bound to its mould before drying. The curved ouline of the mould makes binding very difficult and it ends up as a mess of wrinkles and sticky tape.

Last picture is of the leading-edge sheet in place on the wing. Some judicious trimming will be needed until it fits snugly enough to be glued down for good.

Stephen.

Stephen,

Really enjoying following this build and flights of the testbed. The Mosquito is a favorite airplane and it's nice to see it done with your precision and craftsmanship.

Many thanks Oliver.

Yesterday I made the sub-spar that runs where the radiator face is - and forgot to take photos. I also did the coarse part of sanding the trailing edge to shape. Then today I've spent ages tying myself in knots over the radiator intake. I took the best measurements I could from suitable Mosquito photos but I'm not confident that it'll look right when finished. That's the difference between a quick test model and a properly-finished job - it takes twice as long bcause of piddly details!

Next, because the radiator intake is narrower that the radiator face itself, I cut a piece of card the same size as the radiator face, to check that I could insert it thru the intake then erect it and press it against the sub-spar where the radiator face is. That's so's I know I'll be able to paint or draw (or something) a representation of the radiator and smuggle it into place after the tissue covering's done. Fine! It went in and sat vertical with a bit of prodding, snug against the spar. Duuuuh . . . how to get it out again? Hmmmm, hadn't anticipated that. The answer is that you have to destroy it in the process - see last pic.

Stephen.

Nice work Stephen

Quote from: Prosper on Feb 09, 2026, 06:23 PM...so's I know I'll be able to paint or draw (or something) a representation of the radiator...

.
May I draw your attention to my favourite trick for a radiator grille/mesh? Surprisingly convincing even when seen close up.  A very thin film of (spray on) varnish is needed to stop the pencil lead smudging.

That's ingenious, Genius! Kudos, as they say. It won't work for this project but I'll remember your wheeze for future use. The radiator here has only vertical elements and no grille as such except for the inmost little part. I'll probably try to render it pretty dark, as it looks in most pictures. Talking of which, looking out a picture to illustrate the radiator, I found this (pic 1), which I'd only glanced at during research . . . and now I'm really angry:

  After gawping at every image and every video from every angle I could find, I'd satisfied myself that the wing section of the portion of the wing housing the radiator is completely smooth - a continuous curve. Yet this drawing shows a distinct bulge on the lower surface. My belief that there was no bulge led me to make an intake slot which looks too narrow, to my eye

Quote"but I'm not confident that it'll look right when finished."

. Now, this is only a drawing - a sketch, so to speak - but it looks pretty authoritative. The bulge would explain how to make room for a wider slot. Too late now, unless I take a step back and rebuild this area of the wing.

Stephen.

Apart from the radiator business, I sheeted the leading edge. This was with 0.6mm soft wood, and I expect it will be thinned slightly more by the final sanding fair, prior to covering.

Pic 2) shows this sheeting from behind. I normally choose a mainspar position further back, say 1/3 of wing chord, and sheet ahead of this. That means the sheeting is glued to the mainspar. In this case the mainspar position is dictated by the way the engine nacelle mounts to the wing. It's further forward. So the L.E. sheeting extends behind the spar, and is glued to very thin spanwise strips (I think they're just too flimsy to be called 'sub-spars). I think this will be strong enough, and the spanwise strips should support the sheeting well enough that it doesn't sag between ribs due to tissue shrinkage. It worked OK on the test model.

When I first started contemplating the design I presumed that I'd have to cut away the mainspar where it crosses the nacelle, in order to give room for the rubber motor. When it came down to detailed design I was pleased to find that this wasn't necessary. Left of pic 2) shows where I've partially filled the gap between the mainspar strips, and added cross-pieces behind the spar. These will have holes in them to accept pins on the detachable nacelle.

Pic 3) is the inside of a wingtip skin. This is nominally 0.6mm too, but it's been somewhat crushed round the edge by the tissue that bound it to the mould or form. I hope it'll be strong enough. I don't remember edges this thin on the test model. Mind you, I won't be flying this model over entirely unsuitable ground as I have the test model. That has suffered both tips hitting hard and rutted ground multiple times with no breakage (final pic).

Stephen.

I've been unable to work on this since my last post, other than in bits of time here and there - which I've used to get the left wing to the same stage as the right - nearly done. There's now a switch of focus. I don't want to install the wingtips until all the multiple spanwise strips are in place. I don't want to install those until the pendulum aileron pushrods and bellcranks are in place. I don't want to install those until the engine nacelles are made and fitted. So next I'll be tackling the nacelles.

QuoteThe bulge would explain how to make room for a wider slot. Too late now, unless I take a step back and rebuild this area of the wing.

Regarding the radiator intake slot, I've decided not to modify it, though I'm not too happy with what I've got. After seeking through my picture collection again for useful evidence, I couldn't find any photo suggestive of a noticeable bulge under the wing . . .  but could find to the contrary, as the 'screengrab' attached seems - to my eyes - to indicate. With the cowlings off, the line of the underwing is cearly seen.

The ghostly hand swimming into the picture isn't in fact an apparition but belongs to one K. Weeks. The Mosquito is one of the 'new-builds' - a brand-new Mossie made from scratch. This does raise the question of what concessions and compromises the builders might make, and what gaps might exist in their knowledge. Maybe they have every de Havilland drawing and only use the original specs. Either way, the area concerned isn't one that 'comes out well' in period photos - at least at the perspective angles I'm looking for. So I'm going with the 'new-build' evidence.

Stephen.

Nacelle wrassling.

The nacelles are less curvy than drawings like to show. All in all when making the balsa plug for the test model, I had to spend a lot of time working out the shape, leaning heavily on photos with panel lines evident and on u/c doors. It came to light that the aft end is 'hollowed out' - see pic 2, and 3 shows this quite well. Drawing u/c doors on the plug, then sanding the plug and re-drawing, until the ink lines looked like the real thing in photos, was my method. Same for panel lines (Mosquito nacelles were of  metal, not wood).

To save effort with the test model I made a plug that was symmetrical and it had to serve for both left and right nacelles. This made working out the blending of nacelle and wing difficult. The wing taper in thickness, the extended inboard wing leading edge, and the dihedral, mean that the L and R nacelles are somewhat different in order to fit their respective wings. This time I'm hacking away part of the plug and will attach an extra piece specific to the L or R body.

Now see pic 4 which shows the balsa plug in the foreground and one of the test model's nacelles behind it. Look at the curves of the plug, then see how the model nacelle has failed to keep the curvature it had when initially moulded. It can't be down to tissue shrinkage because the fore part is flattened even though it has no tissue covering. I wonder if the exceptionally humid weather for weeks on end is a factor, and the model repeatedly landing on soaking ground. I suppose I need to provide more supporting structure - AKA more weight and more time.

Stephen.

it's a pity that you can't get away with just one nacelle,Stephen ;)  That's an interesting way of judging curvature  - using the shape of surface lines - undercarriage doors and panel lines.

I'm a lousy 3d carver/shaper- I usually resort to 3d dwgs and the use of the old "bread and Butter" approach. Your system is far more accurate as it doesn't depend on the accuracy of the drawings.

I think you should leave your work partly uncovered and displayed in a transparent box. :)

John

Quote from: OZPAF on Feb 23, 2026, 02:44 AMit's a pity that you can't get away with just one nacelle,Stephen

In the event, I saw that this wasn't necessary.

Quote from: OZPAF on Feb 23, 2026, 02:44 AMYour system is far more accurate as it doesn't depend on the accuracy of the drawings.

Yes, I think so, but it does need some basic 'solid' information, say nacelle length and width for example. All the rest can be discovered by study of many photos and getting ratios. A really good side-photo (good in the sense of not being distorted by the camera lens) can yield the basic shape and then the study of photos at different angles can show up 3D aspects like cross-sections. 
 

The picture shows the nacelle plug (which I made for the test model) with a razor saw in it - I made several cuts on the right side of the plug. Thin card can be pushed into the cuts and a pen can be run round the card where it meets the balsa. This yields a true cross-section as seen in the picture. These card cross-sections not only help in attaining an acceptably symmetrical plug, but also make the templates needed to shape formers for the nacelle internal structure.

Now I've gone further and sawn the nacelle plug right in half. Am I mad? Well probably. But that's not important right now. In fact as I hope to show in coming posts, this will make joining the moulded balsa sheet parts of the nacelle quicker and more accurate. It happens that the original saw-cut wasn't at all perpendicular to the plug's centreline, so when I completed the cut I had to add some balsa and sand it square - this can be seen as a thin balsa wedge in one or two pics. On top of that goes another 'endplate' of thick wood. This is just to stop all the handling and tissue-binding etc. from rounding off the edges of the plug.

Also see the 3mm 3-ply balsa slabs which were shaped to be the nose formers. Hard balsa, glued with aliphatic.

Now, binding balsa skins to the form. Each nacelle has three main panels - front, rear, and top cowling. At least that's the idea. It worked for the test model. However I'm already on my second attempt of a front skin. It's got to conform to some pretty heavy-duty double-curvature. The test model skins managed this with just a couple of wrinkles which had to be cut out. I think it all depends on the individual piece of balsa sheet used, and practice. That's the second attempt in the pictures, and it's drying in my hotbox as I write this - along with a rear panel. See that there are some wrinkles right at the nose (they're just visible as corrugations). These may well be acceptable - the wood shrinks and flattens out somewhat as it dries. We'll see.

Stephen.

This is a fascinating approach Stephen - courageous as well. Cutting into a carefully shaped form!

John

Thanks John! I've done the cutting-halfway-thru-the-form a good few times before. It doesn't seem to be a problem.

Where was I? Oh yes. I found that when the bindings were unwrapped, the wrinkles at the front of the nacelle panel were still present, so I resorted to brute force. I rewetted the local area and used a hot piece of metal to iron the wrinkles. Hot enough to hiss at it brushes the wet balsa. The now barely-discernible wrinkles can be sanded out - see before and after pictures.

I moulded four of the six nacelle panels yesterday and the remaining two today. It's a slow business because of the depth of windings and sticky tape required - this slows evaporation so the 'mummies' need to spend a couple of hours in the hotbox. In most cases 45 min seeems enough.

I'm learning. Initially, and also with the test model nacelles, I bound the centre of the wet balsa panel to the plug first, then on to the front and back ends. I changed to binding first the ends, then the middle. Hey presto, no wrinkles or puckered lips at either end - but a couple of folds at the middle. To deal with these I turned to what I should have done all along: cutting relief slits, as I do with balsa/aliphatic double-curved panels. These need filling, but the overall result is better - no touch-and-go brute force.

The rear nacelle panels have concavities at the back, as mentioned previously. I used folded wads of kitchen paper* held to the wet balsa panels and bound tight with tissue, to force the panels into the concave areas.

*I'm guessing the term is understood across the English-speaking world - but if not, I'm referring to rolls of pulp paper, perforated to be torn off as squares, often coloured and embossed with patterns, utilised for numerous household (and modelmaking) tasks.

Stephen.

Each shell now has to be rebound to the form, and the relief wedges can be filled in. A sliver of polythene is slid and wiggled between the shell and the mould to allow gluing without sticking the shell to the mould. Then (the rear edge of the shell (top cowling in this example) is trimmed and sanded flush with the mould* - carefully so's not to erode the mould itself. At this point all datum lines are re-marked as necessary according to the marks on the mould. This is because the initial act of binding the wet balsa tightly to the mould almost invariably causes the wood to shift around a bit, and when the dry shell is unwrapped, datum marks will be misaligned.

*edit - the 'endcap' has been removed from the mould at this stage-it was stuck on with double sided tape - yukky but it works

There's a photo showing my Hole-O-Matic™  hole cutter - oh okay, it's just al.tube with the end bevelled to a sharp edge, which is twizzled between finger and thumb to cut thru the wood. Also a photo showing what the result is if a hole isn't cut at the top of a relief wedge: the wet balsa sheet can be all scrunched-up by the tight tissue binding to the mould. In this case I'll just have to use filler to level the craters.

More fotos from yesterday and earlier this morning. I forgot to mention that the last pic in post #46 where a shell is re-bound to the form temporarily, and the back edge is carefully sanded flush with the face of the form - that that illustrates the reason for chopping the form in half. Unsupported, each shell is as floppy as you like, and sanding the back edge evenly and squarely to make a strong all-round join with the front edge of the rear part of the nacelle is really difficult.

Anyway, the front shells are joined up (the joints are along a straight line so relatively easy to achieve) and now the 3-ply disc can be unpinned from the front of the form ready to assume its grave duty as the nose former in one or other nacelle. In the pic it's not glued in place yet: just showing off for the camera. The other 3-ply slab can now be pinned to the form, to be shaped.

Then I cut a template from thick card and lifted the perimeter slightly. This is pinned to a slab of balsa which has adhesive-backed plastic film on it (non-stick). I cut strips from soft 0.3mm balsa. Four strips, put under the water tap, stick together and can be coaxed into the template. This normally works without the strips kinking but there are kinks evident in the photo. In this case I don't care that much. When the strips have dried they are wetted out with thin CA.

Stephen.

Today's work:

I have a habit of cutting formers on top of the drawing of the former, and holding two pieces in together on the drawing and putting a dot of thin CA on the joint. Occasionally slicing a piece to size with a razor can damage the paper, and occasionally the CA can get onto the paper. It sure is quick though.

One of the laminated formers pushed into place inside the nacelle. It appears to be detached from the nacelle at the bottom but this is just due to the slope of the nacelle - it's in contact at the front. I'm too lazy to chamfer the laminated hoop to fit properly.

Making a laminated hoop on a socket. I used a single strip of soft 0.3mm balsa, and glued it to the 7/16" socket with a tiny dot of CA. I wound it round the socket under slight tension - this prevents the strip from kinking. Then another bit of CA to secure the end. Then break the tiny bond between the strip and the socket by pressuring it with a fingeranil, and the whole hoop can slowly be worked off the socket. When it's ju-ust in contact with the socket (necessary for it to keep its circularity), some CA is dotted around the hoop - enough to secure its shape without gluing it to the metal. Then it's removed entirely and dosed with CA. These aren't very neat examples, but should be good enough.

Stephen.

The circle thing is a trick I am definitely going to nick.

What a master class of alternative Modelling! I feel ashamed to say that I've tinkered in a similar hobby! 😅

Good to hear from you Mr Speedy. The truth is, all this is predicated on whether I can succesfully cover the model. Apart from the test model immediately preceding this one, I've never tried tissue covering over double-curved sheet surfaces, and I've never shown anything but basic aptitude in straightforward tissue covering. I might send the uncovered airframe to a recognised tissue guru, someone like Mike 'MKelly', along with a begging letter :D.

Lurk, I hope you try this. As you can see the difficulty is in holding one end of the balsa strip to your chosen cylinder until you've wound one revolution of the strip - whereupon the end is trapped. I think I've managed to do this without resort to glueing the end in the past - but anyway the whole thing needs practice and a stoical acceptance of a few failures.

Today I taped the fore/aft mould halves together again, to shape some longitudinal strips which are in effect, the longerons. This is hard 0.8mm wood but it still responds to wetting and modest heating (my hotbox seems to attain about 60° in typical ambient conditions) - see the twisted and curved item in front of the nacelle. I joined the shells of the port nacelle and cut one of the strips to fit between formers as seen in the picture through the snout of the nacelle - the strips aren't glued in place yet.

The nacelle as yet seems to have retained its curviness - no flattening out as has happened to the test model nacelles . . . The thing that's been bugging me is how to clip the nacelle to the wing. I did this in a basic model Westland Whirlwind - there was a sprung latch which made a lovely 'snick' when the nacelle was pushed home, and which was released by pushing a wire into a very small hole in the wing. But that was a larger and more roomy job than thissy Mosquito. For the test model I used a crude and very visible pin, which turned out to need three hands to install (one for the model, one for the nacelle and one for the pin). I want something less visible  . . . and less annoying.

Stephen.

QuoteThe thing that's been bugging me is how to clip the nacelle to the wing

Have you considered small magnets to the rear of the nacelles to complement forward locating pegs in the holes in the former near the wing LE?

John

Hi John, I must admit I hadn't considered magnets - at least not consciously. The thing is, I've had trouble using them to fix the cowling of a Sopwith Camel model. They're strong enough (2 off 3mm, clapping onto little steel plates) to secure the cowling (which houses the motor/gears/prop/capacitor) But, when it comes to taking the cowl unit off, I've found it's hard to grasp the airframe securely enough to pull the cowl off. All the struts, wires, details, what have you . . . there's nowhere to hold it firmly. Then again, if the magnets are held away from their steel plates by a fraction of a millimetre, their attractive force becomes insufficient.

So I think I dismissed them unconsciously, so to speak. I might reconsider, but at the mo I'm leaning towards a piano wire spring-latch.

I've got some work done today, but no photos.

Stephen.

I've hit a rather frustrating bit - making the rear part of the nacelle which remains fixed to the wing. The horizontal part let in to the trailing edge of the wing - that's fine. Easy. It's the sides that are the problem. On the test model these proved difficult but it didn't matter that they ended up looking horrible and botched, whereas it does matter om this model! This is taking more time than it deserves. Other than that I've been catching the right nacelle up to the left one - it's not far behind now. When I've got these jobs done I'll be all nacelled-out, and glad to get on with other parts of the model.

Stephen.

This is some next level building! 8)

Thanks Gravitywell - undeserved praise I suspect, but welcome all the same!

Finally  got the rear nacelle fairing thingy finished. And still the other one to do. It's not very satisfactory but it'll have to do. There are now two strips at the rear of the nacelle which engage with the fairing thingy, and a hooky-thing that slides into the rear spar when the nacelle is slid into place, ensuring that the nacelle can't drop down at the back. I've still the motor peg (or maybe hook) to sort out, and the latch to stop the nacelle flying off the wing . . . oh and of course some details . . .but subject to a final clean-up it's pretty much done.

Stephen.

After getting nothing done yesterday, this morning I decided to forget the nacelle rear fairings - sick of it - and start on the pendulum ailerons.

I have an oak block - once a sanding block - into which numerous small holes of different diameters are drilled. A 0.5mm piano wire pin is stuck into a suitable hole, and a long piece of 0.4mm wire has its end bent over. This bent end is inserted into another hole, and is taped down with masking tape. The long piece of wire can then be wound around the pin, as many turns as needed; released; ends clipped and turned up, and there you have yer bellcrank. Another one is wound the opposite way, for the other wing. The one pictured was wound clockwise, for the stbd wing.

Four more of these coils are made - this time of 0.34mm wire wound round 0.4mm pin, and with one end cropped off right at the coil, and filed smooth, so that there's just a coil with wire sticking out at one end. Two clockwise and two anti.

Since the cranks were wound round a 0.5mm pin, that's the diameter used for the pivot pins*. A pin is seen fixed firmly into a hard piece of 1.6mm balsa - this will be mounted to the relevant wingrib.

The pushrods, extending out from the pendulum in the fuselage, to the long arm of the cranks, are of stiff 0.8mm balsa - a broad vertical bar and a thinner strip glued to it to make a T-section. The edges painted with yellow Sharpie pen are the edges to be glued: I found by happenstance once that yellow Sharpie ink goes bright red when CA'd. This can be used as an indicator of successful CA bonding.

This installation needs four bearings for which I use thin aluminium - from one of those disposable food trays - in this case snipped and chopped rounghly circular. A 0.5mm hole is 'twizzled' through it, then it's punched into a cup made in a thick slab of plastic card, to make a dome. The dome is lightly CA'd to the base of the pivot pin.

I got some more done than this but will post pix tomorrow.

* I don't know the correct or formal names for all of these things so kind of make 'em up.

Stephen.

Amazingly neat work!! Well out of my league!!👍

Ta Mr Speedy :)

I reluctantly had to take up the nacelle rear fairing of the stbd wing. Oh boy. Another day wasted, with moulded sheet after moulded sheet provong inadequate. Today I reverted to a fix I'd been resisting all along - simply carving the shape out of soft block balsa. Only it's not simple. I'm creeping towards a result. The reason I disliked this way of doing things is the weight. My hunch is that it will weigh at least twice the sheet version.

The reason I could no longer ignore this fairing is that I made a pair of ailerons - but couldn't finish them until the wingtips are in place and finished. Can't do that until the many spanwise strips (pseudospars?) are in place. Can't do that until the nacelle fairing and pendulum setup is in place . . .

When I say 'can't', I mean 'shouldn't', really. Once those strips are in place working on the wing becomes much more awkward.

More soon I hope.

Stephen.

I meant to add these pics when I last posted, but didnt have time. The first shows the link or hinge between the pendulum bar extending from the fuselage along the wing, and the bellcrank. By using  wire coils wound in opposite directions for opposite wings, I find that the coiled wire rides on the bent wire of the crank - a simple and v. low-friction result.

Next is a closeup of another coiled wire and some thin al. from a baking tray. This al. is folded around the wire and crimped, and a hole is made thru the end. This then becomes the link between crank and aileron. The point is that the coiled-end wire can be slid in or out of the folded al. tab. This is useful because of the huge leverage at this end of the pendulum system. Whereas the pendulum might swing several centimetres either side of vertical, at the aileron end, a millimetre of movement of the link seen here will rotate the aileron considerably. The ability to slide the coiled wire in or out of the tab changes the link's length, which allows fine-tuning of the aileron's neutral (pendulum centred) position. When done, a drop of CA run into the al. tab will lock the wire. Thereafter, flight trimming of the ailerons will come from adjusting the system at the pendulum itself.

This is probably clear just the same as mud is clear . . . I hope to take some photos that explain things better.

Now back to the present. A picture showing the shaping of soft block rear nacelle fairing. The picture utterly fails to convey the exasperating nature of this job. I could make a whole new %***££ nacelle in the time it's taken to do this %**&& fairing. And it's not finished yet. Below the wing are two of the many failed moulded-sheet attempts.

Incidentally, the join between the removeable nacelle and fixed rear fairing copies a panel line on the ackshual Mosquito.

Finally, I meant to take a 'before and after' photo of the ailerons but this job advanced so smartly that I overshot, so one aileron is not fully 'before'. But then the other isn't fully 'after', come to that.

Stephen.

Yesterday I finished the stupid rear nacelle fairing. It transpired that I could thin the block balsa more than I'd anticipated. I thought that the very curvy shape, cutting across the grain of the blockwood, would make the part brittle and ready to snap. In fact not. It's still heavier than the moulded sheetwood though.

Clear of that ghastly trap, I've been able to get on with the pendulum system today. To mount an aileron, the wingtip needs to be finished - but I'm not ready for that yet. So I've temporarily glued a strip of scrap wood with a hole drilled in it, to the wing. The outer aileron hingepin can slip into that. There's a picture of the inboard part of the stbd aileron with piano wire hingepin, and also the wire hook which the crank-to-aileron link hooks onto.

Stop.

I do have a problem with nomenclature here. I'm okay with 'pendulum' and 'aileron': it's the bits in between, that join the pendulum and aileron, that I have trouble with. F'rinstance, the bar running along the wing from the pendulum to the 'bellcrank': I want to call that a pushrod . . . except that it's a pullrod too. The bellcrank isn't bell-shaped and it doesn't ring. Anyway, here's a clearer picture of the 'pushy-inny-outy coiled-end thing'. This component proved too long, and I've pushed the wire further into the crimped aluminium, to the length seen here.

A picture of the bellcrank pivot pin, lightly fixed to a wingrib. Now I've had the setup working, the position of this item seems good so I'll fix it well with CA.

The next picture is of that same part of the wing seen from underneath. It's hard to see what's going on, I admit. First, the aileron has to be removeable. Just in case. A slim plastic card rectangle with a hole in it is slipped onto the inboard aileron hingepin. The outboard aileron hingepin is slid into a hole at the wingtip, and then the plastic rectangle is spushed into the slot. The plastic rectangle projects out a long way for convenience: once the setup is tested and passed, I'll cut off the projection to a minimum.

Then a picture of the whole setup from above. With the crank neutral, the aileron's neutral. At this first fitting and testing stage there's still work to do - some bushings and washers, and endcaps.

Stephen.

That's a nifty hinge arrangement Stephen - light and practical.

As for a name for the pendulum transfer beam - how about "crank arm".

John

Thanks John! Crank Arm it is.

As well as working on the right wing pendulum aileron assembly, today I made a spring catch for the right nacelle.

This little catch relies on the springiness of two 0.5mm lengths of piano wire. The wires are mounted strongly behind the mainspar; they take a sharp 90° turn, go through the spar at the top, and extend forward, ending in the pawl or whatever it's called - the wedgy thing that makes the catch. Inside the nacelle at the top, I glued a balsa ramp (arrowed). This takes advantage of the laminated former making a natural strongpoint. When the nacelle is pushed into place under the wing, the pawl rides down the ramp under spring pressure, and clicks up when it travels past the ramp. This is pretty neat given that it's an afterthought. To release it I can stick a fingertip into the nacelle from the front, but intend to make a small hole in the top of the cowling, through which I can use a prodder to push the pawl down.

The last photo is rather indistinct, but shows the catch in place, doin' it's job.

Stephen.

Stephen,

I immediately thought of you and smiled this morning as I read this sentence in an article accompanying G.E Whitehead's 24" Nieuport 11 plans from the December 1972 issue of Aeromodeller.

"The sweepback of the wings combined with the small amount of (non-scale) dihedral provides plenty of stability without without recourse to such 'artificial aids' as pendulum control."

The cheek! What utter blasphemy, tacitly endorsing non-scale dihedral as canonical while condemning pendulum ailerons as artificial aids in the same sentence. Heretic! ;-)   

Keep fighting the good fight.

Quote. . .tacitly endorsing non-scale dihedral as canonical while condemning pendulum ailerons as artificial aids in the same sentence.

Har har :D

Yes orthodoxies can be very puzzling, in whatever facet of life. Artificial? Last time I looked, aeroplanes had ailerons which move up and down l. Most scale free flight model aeroplanes don't - isn't that more artificial than having them? My pendulum systems are made of balsa and bent wire - why would this be artificial as applied to ailerons, but apparently acceptable in all other areas of modelling?

Anyway, I must stop before I go into a rant and nurse forces me to take another of her 'little tablets'. Mind you, I'm tempted to make a basic Nieuport 11 with scale dihedral - it looks the same as a Camel dihedral-wise, and the lesser dihedral stability of the lower, dihedralled, wings of the Nieuport (because of their smaller area) might be well compensated by the sweepback. The Camel is very stable.

First, I must correct my last post - I said my nacelle latch was installed on the right wing whereas the photo clearly shows it's the left. I get muddled.

Photos show the pendulum components fully installed in the - uuh left? right? Left wing. Just about visible are the little plastic card endcaps on the pivots. With this done I could fit the 1,459 thin balsa spanwise strips (we-ell, five on top, three on the bottom in fact). In fact the whole, conjoined arrangement of crank arm, crank and aileron linkage can be smuggled into the wing after the cage of mini-spars is fitted. I did this on the test model. But it's a murderous job.

Note how the mini-spars wave somewhat from rib to rib - that's from my inaccuracy in cutting the slots in each rib. The 0.4mm balsa strips are pushed into a slot in a rib by pinching the strip either side of the rib and gently coaxing the strip into place - finished by tamping it down with some square-ended object.

Now I can get the other wing to the same stage and fix the wingtips.

Stephen.

Stephen,

If you do a Nieuport 11 I'll be tuned in. There is just something I love about that airplane.

Your work looks wonderful as always.

Quote from: bcarterIf you do a Nieuport 11 . . .

But when I think of it, I've got so many models to attend to - 3 or 4 unfinished projects and a couple of finished-but-untrimmed models, and a couple of experimental bulds i want to tackle . . . Aaiiiy - not enough time!

The wingtips. I trimmed the prawn cracker-style wingtip halves. Note how thin the wood is at the very tip (arrowed). The other arrow in the picture: see the billet of timber forming the leading edge - see how the leading edge continues a straight line well past the last rib. However, in front elevation the taper does begin from the last rib outboard.

Well, at some point I noticed that the billet of timber wasn't sanded very fair, and blithely gave it a few sweeps with a fine-grade sanding block. Then I glued the bottom skin in place. I saw that there was a slight gap between timber billet and skin, but cheerfully went ahead and stuck it down anyway. Then I went to peruse photos to see the position of the wingtip navlite transparency, and got an uneasy feeling. Back with the model I could see that I'd sanded away the correct wingtip curve. Hence the gap between billet and skin. It's much too rounded.

Great steaming idiot. I now have to remedy matters (time and faff) - I haven't decided how yet.

Stephen.

{quote]I now have to remedy matters (time and faff) [/quote]  I made the other wingtip for practice, then repaired the faulty one with an almighty bodge, as ugly as they come. But it's under the skin, so who knows? I certainly don't :).

There's quite a bit still to do on the wings/nacelles, but now I'm turning to the tail surfaces.

Stephen.

Quotemade the other wingtip for practice, then repaired the faulty one with an almighty bodge, as ugly as they come. But it's under the skin, so who knows? I certainly don't :).

I'm actually amazed that you can match preformed panels with the shaped LE, full stop.

Where is your English wheel to modify the curvature of the panels. :D ?

I remember reading an article quoting DeBolt stating that the Curtis P40 wings were built from the outside inwards. The Skin was laid up in jigs and the ribs attached to the skin. I wonder how many gaps there were between the ribs and the skin.

John

Stunning!

Thanks Australia :).

John, shaping that billet of wood isn't so hard - after all the plan taper and curve are known and can be inked onto the initial blank; likewise the front elev. taper and curves. The cross-section of the inboard end of the piece is also known, coz it's the same as the nose-shape of the rib it butts against. That same shape is used to make the balsa tip mould that the skins are bound to for shaping. So with a bit of careful sanding the billet should have the same curves as the moulded skins. Close enough for this kind of a job anyway. That's why I ws so cross when I ruined the shape of the stbd billet by some brain-in-neutral last minute sanding.

Yesterday I just had time to make the tail surface skins/shells/prawn crackers. They're all from nominal 0.5mm soft C-grain. I find crossgrain generally better at adopting and holding moulded curves. Pic 2 shows the balsa moulds (foreground). The Mossie's tailplane had a symmetrical section so only one mould is needed for left and right surfaces. Note that the lines of the fin and tailplane are inked on the moulds. I dose the L.E.s of moulds like this with CA to strengthen them. Tissue binding needs to be firm, and sometimes can squash mould L.E.s, if of soft wood.

Pic 3 shows a freshly-bound stbd fin skin and a wet blank applied to the tailplane mould. The skin is glistening wet. This wet, there's the advantage of it sticking to the balsa mould - which helps placement while it's bound - but the disadvantage that such a wet article weakens the 'wet strength' tissue and it can easliy tear under the stress of binding. This is not precious Esaki of course but craft tissue used by lamp-makers: about twice the weight of Esaki.

After a sojourn in the hotbox, when the parts are unwrapped, I ink the correct finished outline of the skin on the skin, using the aforementioned markings on the mould, while the skin is still in intimate contact with the mould. It's hard to ink a freehand line along the leading edge, so I rub the side of a pencil lead gently along the L.E., which leaves a faint grey mark to guide the ink pen.

Stephen.

Onto the control surfaces. The first picture is an X-ray image of the test model's fin and rudder. I took this because I have no drawings of the rudder, and needed to see it in order to 'reverse engineer' it for this model.

I do have a drawing of the tailplane/elevator, which is slightly modified because of the way the elevator meets the fairing on the Mosquito tailcone - more on that later. The series of photos is the best I can do - without a headcam - to illustrate the construction method.

Broadly speaking this involves cutting strips of wood (in this case quite hard, straight-grain 0.8mm (1/32"). A strip is laid on the drawing and sliced with a razor - used in the guillotine sense. The cut end is squared off with a brush or two of sanding block, the strip is pushed against another strip and CA'd. That's probably a poor explanation but I hope the piccies help. Note that the photos were taken scant minutes apart - this is a Supa-Kwik method. I anticipate that the rudder will follow as quickly.

Really eagle-eyed viewers might just notice that the elevators somehow don't quite have the full streamlined, curved elegance that is the Mosquito's essence. Yes, I suppose they could do with a going-over with trimming knife and sanding block :D.

Stephen.

I've added some thin balsa sheet to the 'balance horn' area of the rudder - this should hold the tissue to a nice convex curve. Also three hinges, made of baking-tray aluminium folded in two. The slits thru the spar, to hold these hinges, are made with a piece of razor stuck into the end of a bamboo stick. The fin spar is only 0.8mm thick so has doubler blocks stuck onto it to anchor the hinges.

The join of the two fin skins, along the leading edge, is just about visible.

There are two additional little blocks of balsa glued inside the fin leading edge - one is to anchor the pitot probe, and one to anchor the aerial wire - if I ever fit one.

I had hoped to get further than this today, but there it is. The construction of the tailplane/elevators is so similar to what's shown here that I'll just crack on and not take photos.

Stephen.

I glued the tailplane skins along the leading edges, but got no further because I decided that I really ought to have the fuselage - or at least the rear fuselage - ready before finishing the tailplane. This so that I can achieve the best fit between the two. So for the last couple of days I've been modifying the fuselage mould. I've split it into three main parts, for the same reason that I split the nacelle mould: exact joins between different skins are much easier to make. I hope to show this in photographs.

The fuselage mould was carved from many bits of odd block balsa stuck together. I used to make big moulds like this from expanded polystyrene, but never liked it - neither the hot-wire cutting nor the sanding. I found that packs of irregular block balsa offcuts were cheaply available, so took to balsa instead. But I looked at balsa block prices recently - blimey! Costs a fortune! I presume this is the wind turbine effect  https://eia.org/press-releases/ill-wind/ 

I made a separate mould for the bomb bay doors. That's because the subject I want to represent had the 'pregnant cat' bomb bay. From all my photos there's no really good indication of the curve of these doors. The pesky engine nacelles always obscure that area in photos. I think my first iteration might be a bit too curvy - but I'll see how it looks when matched up to the rest of the fuselage. What's seen in the photo is that first attempt, moulded in two halves and joined along the centreline. Note the red line - this comes from drawing a yellow Sharpie pen along the edge of the balsa skin before joining - whereupon it turns red when touched by cyano. This then gives a clear indication of the completeness of the joint. Mostly I use cyano in a sort of 'spot weld' fashion, but sometimes a totally glued joint is needed. The bomb bay skin is then loosely bound to the mould to encourage it to keep its shape until the time it's fixed to the rest of the fuselage.

This bomb bay has considerable double-curvature and I used reasonably stiff balsa, which led to three wrinkles in the skins from the initial wetting/binding/drying process. I cut these out and inserted balsa patches, circa 4x4mm. One of these is just visible (arrowed) in the picture.

Stephen.

Today I reshaped the nose mould to make it suit a bomber Mosquito. I had to revert to holding the nose mould up against pictures on my PC screen to see how good (or bad) the match was. Hardly ideal but the best way available. It's not just about comparing the outline, but also comparing shape, by drawing lines on the mould (the little side windows are a good example) to see if they match the same lines on the photo. In the end the nose needed quite a bit of reshaping and is now about 6mm shorter than it was, which means a slab of balsa added to the back of the mould to restore the correct length. I then plunged a test of the Perspex nose. It looks like the side windows can be obtained from the same plunge as the nose bowl.

I then made a bomber canopy mould, and likewise tested a plunge of this. It clearly needs a good bit more shaping yet. It doesn't look right.

Stephen.

It takes a good eye to see those differences Stephen - and a fair bit of artistic capability.

It's a fascinating journey.

John

Quote from: OZPAF. . .a fair bit of artistic capability.

S'funny you say that, John. About 18yrs back, I started to teach myself painting (aeroplanes of course :) ), and thought that the best way of seeing how light bounces off an object would be to make a model of said object and place it in the same relation re. sun, sky, clouds, whatever, as the subject I wanted to represent in oils. That's what went and gone an' got me into this daft hobby :). I ended up dropping painting. Mainly due to eyesight troubles, but partly because this daft aeromodelling thing sucked up all my hobby time.

 Adding a plate at the rear of the nose mould means that it doesn't match the fuselage main section behind it - see the photo. Luckily I dodge a bullet here, because the sides are parallel, so they do meet each other properly, and the main discontinuity is at the top - where the cockpit is, so there won't be any wood there anyway. The discontinuity at the bottom is slight and I sanded it fair.

After reshaping the canopy mould somewhat I tried another plunge. Better but not quite there yet.

Meanwhile . . . what has the farmer done to my flyng field? It's been sprayed with pesticide, sprayed with slurry ('muckspreading'), and yet still has cattle on it, fed with hay. It's a churned-up, dead, smelly mess. Normally at this time of year it's lush green. I have a nasty feeling that it's going to be ploughed up - maybe soon - and planted with maize.

Stephen.

That doesn't bode well for your flying field Stephen! Whatever is planted there will just become a new challenge to miss :) 


John

Moulding these nose skins was something. 3+ hands required to do the binding. It meant that the top and bottom skins had to be done individually - on less curvy moulds I would bind a left+right or top+bottom in pairs, to save time in the hotbox. That's approx 1hr for stuff like this, whether it's just one skin or two. I did manage to bind the left and right as a pair, so saved 1hr. Incidentally I measured the temp in the box - something I haven't done in years. 82°! That's going some. No wonder these parts are holding their curves nicely after unbinding.

The top and bottom skins had to have slim 'relief wedges' cut out at the front in order to bend to the curvature of the mould.

Today came the tricky job of shaping the edges so that they fit accurately. This is one of those 'sand a fraction off just here; check the fit; repeat' type ops that takes time. I stuck a thin strip of Sellotape to the mould to stop the skins from sticking to the mould, and commenced to join the skins until only one seam remained. I thought I had shaped the edge of this so that the skins fitted to the mould tightly at the front. I glued this seam 'in the air' - off the mould: easier to manipulate the join. But when I put the finished nose onto the mould it was loose at the front. I had to cut out additional relief wedges in each side panel and glue them closed, in order to get the right circumference at the nose. Those relief wedges have to have slightly curved sides.

The balsa skins and the PETG nose transparency are formed on the same mould. But the balsa skins are much thicker than the plastic. Approx 0.4mm thicker. So there'll be a step between the two when the transparency is fixed in place. Hmmm. Heck, I don't even know how I'll fix it yet. One of the things i wanted to find out from the test model is the vulnerability of the nose with regard to landing. As I'd hoped, the nose turns out to be well protected by the nacelles and props. So I hope the light structure of the nose will suffice in this model too.

Stephen.

QuoteI had to cut out additional relief wedges in each side panel and glue them closed, in order to get the right circumference at the nose. Those relief wedges have to have slightly curved sides.

Good grief Charlie Brown!! :)  The final result result looks very neat!

QuoteThe balsa skins and the PETG nose transparency are formed on the same mould. But the balsa skins are much thicker than the plastic. Approx 0.4mm thicker. So there'll be a step between the two when the transparency is fixed in place. Hmmm. Heck, I don't even know how I'll fix it yet.

A balsa hoop ring under the end of the fuse may allow it to be sanded gently down to the line of the transparency without it being too obvious?

John

Quote from: OZPAFA balsa hoop ring . . .

Yes. That was the kind of thought I was having before turning to the rest of the fuselage (got to keep the whole thing moving roughly in concert). I did use the balsa form to plunge mould a 1mm plastic card 'nosebowl' - that might come in handy - and also I stuck one of the existing test plunges back on the balsa form, and then plunge moulded another transparency over it, which of course has a larger radius . . . that was fun - I didn't know what would happen - would the hot PET melt the PET stuck to the form, and generally make a complete mess? No, it worked fine. So there are 'options on the table', as we jet-setting business magnates like to say.

Also yesterday I made the other fuselage panels - Two forming the main section and two the rear fuselage. These were a doddle compared to the nose  - there's very little double-curvature involved. Today I wielded the long sanding block to get the long edges ready to meet, whereupon the top seam is glued with thin CA. The end-caps of the moulds are unscrewed so that the skins can be clamped back on the mould (fingers being the clamps) and each end of the skins is sanded carefully flush with the mould (pic 3). That's why I cut the original one-piece fuselage mould into three: by allowing the ends of each fuselage section to be sanded exactly flat, the butt-joints between one and the next are easy. The skins at this stage are springy/ floppy - trying to sand the ends flat and square freehand is difficult and time-consuming.

There's work to do on the internal structure, which I've started but no pix yet. Mostly careful measurements, and dealing with the difference from the test model caused by the bulging bomb bay of this Mosquito variant. The picture with the long sanding block shows some thin card slotted into a razor-saw cut in the main fus. mould. The cross-section this provides is for the critical main former (the one that bears the wings and also the pendulum).

Stephen.

Starting on the internal structure: making various templates for the four fuselage formers. I may choose or need at least one in the nose, but I hope not. Of the rear formers, one is light but has a stiff crossbrace, and the tail former is fancy. The fin spar slots into its forward face, and the tailplane spar presses into its rear face. All the flying the test model has done is with the fin/rudder not fixed to the airframe: the fin can be drawn from its slot. Positioning these formers for fitting involves skewering the former on a bamboo stick, in the case of the tail former, and pushing the crossbrace into a split end of the same stick, in the case of the mid-section former. Then lots of tamping and hooking (bent piano wire) to align the former. The weight of the little tail former worried me - it's stiff 1/32  0.8mm. The test model is irritatingly tail heavy . . . but the former turns out to weigh only 0.15g, so no grounds for complaint I suppose.

Stephen.

.

Your multipurpose rear former( 0.15g - getting a bit heavy there Guv.) is clever Stephen and I like your skewer assembly approach.

Will the elevators be hinged as well as the rudder?

John

Oops - I'm back after an unscheduled absence. I hope to get on with this model now. I've started on the main formers. The one on the left has a strong crossbrace because it's located where I will hold the model for launching. I learned from the test model that this was the natural spot for a balanced launch (as much as I can ever achieve a balanced launch that is . . .). The former I'm assembling on the right is The main former - the one that holds the wings and the pendulum.

John, yes the elevators are articulated and yes the tail former/slot/spar arrangement could be lighter ;).

Stephen.

Here's the construction of the main former from a long strip of 1.6 x 6mm balsa. Once the bits are glued, the same templates used to produce the drawing of the former in the first place, are used to draw an ink outline on the actual balsa former, and the razor is used to chop close to that outline, and a sanding block to finish.

This former bears the wings, the mainspars of which will slide into brackets glued onto the former. The last picture shows the idea, but without the bits fixed and the former sanded fair.

Stephen.

.

Righty-o. This is the finished main former with the wing spar sockets added. The lateral cross-pieces are of the hardest balsa I could find because the leverage the wing spars exert on them is great in the case of heavy landings, cartwheeling tip-strikes etc. The wing mainspars themselves are simply two strips of 0.8mm, but here, inboard of the root rib, they have been strengthened with webbing between the two strips and a doubler, making them 1.6mm thick. Also these and the sockets are given a liberal drink of CA to toughen them further. The fit of spar into socket is tight (except for one spot where I'll  have to add a shim). The test model had less tough components and the wings have developed some play after repeated abuse (crash landings on hard ground), so I hope these tougher ones will survive better. Also the pendulum is part-finished here.

Stephen.

.

Your building skills are simply.....WOW!

    Hi Stephen.   Great to see you back.   And thanks for the detailed close up pics of your Mosquito.    8)

Lastwoodsman
Richard

Many thanks Richard and gravitywell.

I moulded two side strips to stiffen the interior of the fuselage main section where the wings are mounted. These are of 0.8mm balsa, with the usual wetting, binding to the mould, and hotbox to dry. With limited access to clamp them in place inside the fuselage while glue dried, I found I had to apply glue ('Superphatic' in this case), quickly locate a strip inside the fuselage, then clamp it along its length using fingers and thumbs. With both hands occupied, I had to wander around aimlessly for 10-15 min (each side) until the bond was sure. Never mind - some say that Sunday mornings are made for wandering around aimlessly. The first fixed strip is arrowed in the photo.

Later in the afternoon I finished the pendulum. This has a lead bobweight of 1.0g. I think the test model's bob is 1.4g, but although I seemed to recall writing this down somewhere, I couldn't find where. This pendulum is longer though. I think longer and lighter is better . . . based on vague observations not on good science or measurement.

I hoped to make the hanger too this p.m. - the hanger is the the part that joins the two crank arms running along the wings, and which the pin of the pendulum (halfway along the balsa pendulum) goes through. This hanger needs a slot in it, and the 0.6mm pin must be able to run freely up and down the slot but with absolutely minimal play. Any significant play in any part of the pendulum setup robs efficiency, and since there must inevitably be some play in each of the 14 moving joints of the whole system it pays to really go for minimal play in each. The two slots I cut in the 20 thou (about 0.5mm) plastic card in the photo both were too wide. Perhaps it'll be third time lucky tomorrow.

Stephen.

Quote from: ProsperPerhaps it'll be third time lucky tomorrow.

In fact I managed a good slot on the third attempt, yesterday evening. Today I finished the hanger.

Stephen.

Thanks for those detail pics Stephen!   So that is how it works!   8)

Lastwoodsman
Richard

My pleasure Richard. Yes, as the pendulum swings, the crank arms are pushed from side to side by the pin sticking out of the pendulum, but the arms don't move up or down: the pin rides up and down in the slot in that little piece of 0.5mm plastic card. The crank arm ends slide stiffly into sockets in the hanger; they can be slid in or out individually to change the aileron trim. In the second pic below you can just about see the pendulum pin end-on*. The hanger is absent and the crank arm ends are flopping about freely.

*actually, squinting at it, it seems to be the dished washer on the pin, not the pin itself, which is the bright speck on the pendulum.

To describe the whole system in step-by-step detail would need a 'dedicated' thread, but I guess you've got the idea.

Today I fixed the formers into the main fuselage shell. A rather dicey business - it's not difficult to fit things so that the fuselage ends up misaligned, but I seem to have got away with it. Won't know for sure until the rear fuselage and nose shells are fitted.

Stephen.

I haven't advanced things much today. I fixed flanges to the front and rear of the main section, to provide location and gluing area for the nose and tail sections. The separate bomb bay has made this part of the work slower and more vague than I'd hoped. Now for the first time I can see how the bulging bomb bay looks in relation to the whole fuselage. When I made the bay I thought it was too 'bulgy' - but now I think maybe its not proud enough. I'll go thru the (inadequate) photos I have of this feature - see if there's some sneaky way I can actually derive a measurement, rather than just relying on 'how it looks'. As for the fairings front and rear that blend it with the fuselage, I'm still not sure how those might be made.

Stephen.

I'm marking time here - working but no forward movement. It's to do with the bulging bomb bay, BBB, which is causing more trouble than I could have guessed. I re-shaped the mould, but I think I've got it wrong again; playing with paper patterns . . . sketching . . .

As for obtaining sound measurements from the few relevant photos I have - no luck except that I did notice an angle which I could measure (hadn't thought in terms of angles) - but when applied to my drawings and moulds it appears impossible. Come to think of it I only have one real clue: a book I have says that the 4,000lb bomb was "a tight fit", and the internet tells me that this bomb was 3ft in diameter. The internal width of my balsa fuselage shell at the bomb bay is 42 mm, and this scales up to 39" on the full-size aeroplane. 1 1/2" to spare either side, when the bomb is winched in by armourers off a trolley, in the field. I think that counts as a tight fit :).

Stephen.

Yesterday I was still on the BBB. The extra curvature makes for a more difficult shape for balsa sheet to conform to, so I cut two long relief slits along the wood, and when bound to the mould these overlapped a good deal - the overlapping is where the dashed lines are. I also tackled the rear fairing. This has slight double curvature, but I made what I think will be a usable moulding. It seems to me that I won't be able to fix either the BBB or the front/rear fairings, until the basic fuselage has its tissue covering in place.

I also finished the fusealge tail section by fixing the two frfomers in place. This allows me to assemble and fit the tail surfaces. I hope to take some photos tomorrow. The photos here show various bits of tailplane/elevators. There is balsa sheet added to the elevator balance horn, top and bottom. This is intended to stop tissue sag. The sheet started as 0.8mm but was glued in such a way that most of it is sanded away.

At last some foreward movement. It looks as if this bomb bay doors pair will work. The balsa is very light tho', and given that this is what the model will land on, I think some internal reinforcement is indicated. Note that the bomb bay trespasses into the nose section. That's where I'm going next - the nose section can't be glued to the main section until I've got the nose glazing sorted out, and some kind of instrument panel, internal detail sort of stuff.

The tail surfaces are done, subject to some final finishing. Unlike the nose, I think I can now fix the tail section to the main fuselage section.

Stephen.

Stephen,
I really like this kind of detailed build! Thank you for taking the time to annotate and post such detailed photos of your builds.

Looks great Stephen!   Long live the  "core" ... 8)

Lastwoodsman
Richard

We are so used to seeing your extremely detailed build descriptions that it is easy to forget how much time you must spend documenting it. So thanks Stephen - interesting techniques and tools really make your posts. The tail assembly looks very Mossiesh!

John

QuoteThe tail assembly looks very Mossiesh!

Reminds me of a photo of a Mosquito that downed a V-1. The aircraft flew through the fireball, singeing the aircraft and burning off the control surfaces' fabric. No idea how the pilot managed a safe landing.

Fantastic work as usual John!

This one?
Prosper, your Mossie is looking fantastic, always enjoy seeing your progress!
(Following the full size rebuild in the UK too).
Malc.

  Stephen, beautiful work as usual! Thanks for sharing.

Fanx muchly for the kind comments fellas. Yes, the write-up does take time, and could probably take more time if I really tried to explain myself properly (I often think that my explanations of how I've done something must read as baffling gobbledegook). However, time is something I fairly often have, to dispose of as I wish - something I'm very thankful for.

The nose glazing has eaten lots of it - time, that is. The first picture shows a collection of plunge-mouldings which are failures. Now, my plunge-moulding failure rate is nowhere near that bad as a rule - I would hope for a useable item on the 1st, 2nd or 3rd attempt. Here though the subsequent mouldings were about getting the shape right. Most of these in the pic go back to the time circa posts #83-88.

Yesterday I decided to  get serious. I cut the nose off the balsa nose-section mould, and make a seperate plug to plunge the nose glazing. I think it was the 3rd try I got something useable.

I also reinforced the nose using a circle of plastic card, cut from a plunge-moulded nosebowl like the one to the right of the fuselage nose in pic 2). That plunge-moulded item is a reject - I've kept it just in case a use for it emerges. The reinforcing ring projects slightly from the balsa, making a step. The rim of the nose glazing dome has paper, wetted out with CA, fixed inside it. These aids to location/stiffness have finally allowed a decent fit (he said :o ). Before these additions the very thin transparent PET and the light balsa nose were impossible to match up - they wouldn't keep their shape.

The final picture shows: (1) My attempt to use one of the reject nose mouldings to fashion the external frame around the bombardier's flat panel. Very fiddly. The inside rim of this frame has been cut out, shaved with a scalpel, and finally shaped with (2) a very sophisticated machine tool. Oh okay, some abrasive paper wound round a bamboo skewer. I made this to shape/enlarge holes in wing ribs after the wing has been assembled. 3) Ouch! Blisters. 4) Thin paper strips, cut to a specific curve, were held inside the rim of the nose glazing bowl and wetted out with thin CA. Two layers. The CA bonds well to PET.

Some while back I thought about the side blisters on the cockpit canopy. Oh no - another fiddly little plug to be shaped. Then it struck me that ju-ust maybe the plug I made for a 1/18th scale Spitfire XI (reconnaisance: side blisters), might be adapted. In fact it needed no adaptation. The PET for all this transparency work comes from Tesco - cinnamon swirls, if you have to know :D. For these blisters I should have made a female mould to plunge thru, but was too lazy and used a pre-existing shape - it was the hole immediately behind/below the moulded blister, and was cut for a Gipsy engine nose cowling (¿Leopard Moth?). The material is hardboard.

Stephen.

Stephen, in the most affectionate way possible, I have to call you out as a modeling maniac. I should know I am also a modeling maniac. During post romantic interludes my loving wife will often murmur into my ear " lover, of what are you dreaming?" If she only knew it was how was I ever gonna mount that wing into my new Jet Hustler. All my stuff would be expressed directly to the curb, and I would be on the corner forever warming the hands over the 55 gallon drum. Oh woe is me the modeling maniac lover with the sticky fingers!

Quote from: CrabbyI have to call you out as a modeling maniac . . .

No, not at all, not at all. That's where you're dead wrong. Y'see, I can handle it. I'm in control. Y'see, I can stop modelling any time I want - it's just that I've already opened this kit and it would be dumb to waste it, wouldn't it? After this one kit I'm going to stop. Easy enough. Or . . . maybe just stick with the simple stuff - chuck-gliders can't be any harm, can they . . .

Right, enough of that nonsense. Addicted - Ha! Today I reshaped the Mosquito canopy plug to get it closer to what I perceive the correct shape to be. Once again, lots of photos in my research collection, but few of any use in showing the canopy. I have a Squadron/Signal 'Walkaround' monograph, but the closeups involving the bomber-type canopy are of an American (I think) recce model, which was quite different with large lumps and bumps all over it. My modified plug is a bit asymmetric because I went too far in one spot - but I think I'll use the canopy I plunged from it, because the canopy is removeable, and I can just replace it later on, if I feel the need. I'll take some pics tomorrow if I can.

Stephen.

Hi Stephen I can appreciate the care you are taking with the canopy. For me it's a critical part of the plane's look. Did I ask if whether or not you're gonna use your pendulum control?

Fantastic work as usual JohnStephen!

Sorry about that.

No need to apologise Mike - at least to me . . . John might be offended though, being mistaken for me :).

Quote from: Crabby. . . For me it's a critical part of the plane's look.

Definitely. That's what I've always thought too.

I've just glued the fuselage sections together, for better or for worse. What is seen here weighs 9.3g - that would be 8g without the pendulum.

Stephen.

QuoteNo need to apologise Mike - at least to me . . . John might be offended though, being mistaken for me :).

No worries  :) Just feeling a little crossed out :)  :)

John

Now there are many odd jobs to be done.

Fairing the nacelles and the wing: I made soft balsa fairings stuck to the nacelle. Big misgivings, because these may make it impossible for me to tissue-cover the nacelle. I'm doubtful enough that I've only done this fairing on one nacelle, and I've used UHU glue for easy removal of the fairings if necessary. There is a list of things which I'm sure I'll have to add after covering; these are the bomb bay fairings front and rear; the carb air intakes under the nacelles; the wing-top fairings behind the firewalls, and sundry little lumps and bumps.

Fairing wing/fuselage: the fus. sides are curved and the wing root ribs are flat - hence a gap. More soft balsa padding I expect.

I got the angle of the nacelle front formers wrong. I've added wedges to the top half and sanded away the three-ply below this, to provide a new face at the correct angle. Thankfully the 3-ply is thick and strong so can take some reduction. I think what I did was to install the formers perpendicular to the nacelle datum - but the nacelles are canted up a good bit relative to the fuselage datum. I must have known this, having built the test model, after all . . . Old age, I expect.

The ailerons. Long fiddly job of final instalment. As of now there's a very narrow gap (arrowed) between the aileron and the wing. One wants this, to look scale, but even the slightest binding is not tolerable (and with gaps this narrow even the thickness of tissue covering may be relevant). So, much fine-tuning is called for. The Frise ailerons have their rigidity provided by an 'L' section spar/leading edge of quite hard 0.8mm balsa. I've had problems in the past with ailerons warping fractionally - enough to cause binding - and these are the longest I've ever made, so need special consideration.

Stephen.

Incredible amount of thought and care you put into your projects. I find it to motivate me back to my own projects whether they be at my modeling environment or about the house. I ask myself how would Prosper handle this? Not that  my Crabbifications haven't taken me far.Reading your posts are like taking supplemental vitamins. I am in great hands here. We have had some great craftsmen on this site. "Modeling Maniac" is a term of endearment not a criticism.

Crabby, just in case it wasn't clear, my 'ranting' about not being a modelling maniac in post #118 was a joke. Of course I am one - albeit one who doesn't very often use 'emoticons' to make things clear - because he selfishly assumes everyone will understand that here he's being sarcastic . . . there mischievous . . .  there snarky . . . sincere, whatever. This is where 'emoticons' are useful, because there's lots lost in translation even between English-speaking nations. Not that Americans can speak English of course . . . Oh no! there I go again! ;D ;D ;D ;D ;D [quick edit] ;D ;D ;D

Yesterday I finished fitting the ailerons. Today I turned to the 'front ends': the props, freewheels and associated ironmongery.

Pic 1) shows making brass bushes, just over 4mm long. After years of anguish where I had to drill and ream brass tube to fit 1.2mm propshafts (such a sloo-oow and messy process), some kind soul (sorry - forgotten who) on HPA2 pointed me to a model shop selling 1.2mm I.D. brass tube. I approached with caution, because in the past I had tried different tubes which vendors claimed were a match, only to find jamming or rattling around loosely. All this comes from S.W.G vs. Imperial vs. metric, I think. Anyway the tubes from that shop (Leeds Model Shop IIRC) fit my 1.2mm piano wire perfectly - no binding but undetectable play.

What I do is to use a length of 'sacrificial' piano wire as a handle, and use a hacksaw blade to part the lengths of brass (with a thumbnail as a guide for the blade). The hacksaw blade gets thru to the wire, then I rotate the tube slightly and continue; the  sawblade is now guided by its own cut, until it meets its original cut having gone round 360°. The brass isn't fully cut through usually - the tube is slid off the wire, the bush is snapped off the longer tube, and the ends filed and sanded square. I wish I could find a saw - rigid, with loads of teeth-per-inch, somewhere halfway between a razor saw and hacksaw. I call the wire sacrificial because this work leaves it scored and scraped by the saw - not much good for anything after that.

Pic 2) bending 1.2mm piano wire round a wire post to create a radius. When I started modelling I bent hooks with needle-nose pliers. Occasionally I'd get catastrophic failures where all strands of a motor snapped at the hook. I saw that people use various plastic sleevings. This didn't seem to make much sense to me - I'd already established that rubber can stretch round small radiuses to ridiculous lengths before failing. I had inherited a simple hobby microscope. I looked at one of my diamond hooks, bent using pliers - and at about only 10x magnification, I could see that the inside of the bend was fractured with several tiny splits and slivers of metal - all with extremely sharp edges. Since then I always bend hooks round a generous radius: never had a break at the hook since.

Pic 3) the four bits of wire in the previous pic are filed half-through for part of their length: I'm afraid the pic doesn't show this at all well but perhaps the filed flats are visible.

Pic 4) shows the finished result. Two bent bits of wire are pressed together where the flats are; a collar of brass tube is run up them keeping them snugged together; the whole lot is brushed with solvent for degreasing; some solder flux paste, and bingo they're soldered together into a T-hook.

N.B. This sounds easy, but any of these steps can be a bit hit-or-miss. Take the filing half-through the wire - if not enough the brass collar or collet won't fit, or if the flat isn't perpendicular to the cross of the 'T' the hook will be wonky, etc. etc.. In fact the examples shown are far from the best I've made. I think they're good enough to serve, though. To finish, the ends of the 'T's are filed round to remove sharp edges from their having been clipped.

Pic 5) oh no - more bent wire using my trusty oak block. These hoops are 0.8mm wire.

Pic 6) oh no more  bent wire using my trusty oak block. These coils are of 0.6mm wire wound around a 0.8m post.

Next comes the spinners and nosecones. Thru all of this build there has been the temptation to nick items from my test model - mostly metalwork like this, and pendulum parts. But that model hasn't done its work yet. With flying suspended because no field to fly on, it still has to pave the way trimming-wise before I fly this model. Also the 'front ends' especially are rather shoddy because it's only a rough test model.

Stephen.

Ok Professor I am back to sitting in the peanut gallery watching this contraption of yours un-fold. Every little piece seems to be a model. This plane is a hundred models in one.

Love the master class in wire work, particularly the fixturing used.

These details are often the Ahha moments I'm often missing when trying to figure out how folks make better components than I.

I'm glad you're interested fellas. Really, I just 'muddle through', as we Brits are supposed to do.

I'm aware of having posted about making spinners, prop blades etc. fairly recently - but I think it must have been in HPA2, so I'll carry on regardless.

When turning things in my super-hi accuracy lathe busted old electric drill (the bearings are shot; the chuck is worn and clumsy), I use laminations of 0.8mm balsa, because I saw when doing this for the first times, that the thinner the laminations, the more concentric the result was. Boy, these spinners need lots of laminations. I draw a grid of different-sized squares on 0.8mm sheet (in this case, 12 off 38mm, 8 off 34mm . . . so on to the small squares that make the front of the turnings. Then I draw diagonals across the squares to mark the centre spot . . . doing this en bloc is reasonably quick: the squares can be cut out with long cuts too - not each square independently. I didn't photograph this, but the pisture attached - of a few remaining squares - gives the idea. The two spinners use nearly a whole sheet of 36" x 4" balsa!

Then I selected a suitable spindle from my little collection - the long bolt on the right, with its nuts and washers. But keep an eye on that one that's arrowed, skulking in the crowd. I offset all the squares, so their grain direction varies. I probably ought to set each square at 90°to its neighbour, but my random method seems to work and is easier. At this point I discovered how hard the wood I'd chosen is. V. hard. Normally I start turning in the drill, but the wood is so hard that in this case I sawed off some of the corners and used 60 grit sanding block to attack the work and reduce it somewhat before putting it in the drill.

The turning in the drill went fairly quickly. There's only a fraction of the total dust produced in the attached pic. I use the drill on a low rpm setting, in reverse (to prevent the spindle nut from unscrewing itself).

Once the spinner seemed acceptable in terms of shape, I gave it a generous drink of thin CA - the end-grain balsa really soaks the CA up). Then back in the drill for more sanding (outdoors - the CA dust isn't good to breathe). Repeat; and there's the spinner, except for the tip.

The inside has to be hollowed out. The spindle is turned round so that it extends from the front of the workpiece. I use a specific diamond file as the tool to do this job - only in this case the wood is so hard that it bent the tip of the file. It's bad enough, all the snatching and jerking of the tool, which could gore the spinner, or my hand - but now it breaks. (The bent tip is just visible, bottom of picture.) I resorted to removing the spinner from the drill and carving the wood out using a scalpel.

The thickness of the spinner forward of that blue-coloured lamination is only 4mm. The unthreaded shank of the long bolt is longer than that, and that's where the short bolt comes in handy - it has the same diameter and thread as the long one.

This last pic shows where I got to today. Another session is required: when finished, the rim of the spinner should be only 1mm or so wide. I may have time for another go later.

Stephen.

Great finding on the thin laminations. I failed several times on my spinners for my Piper Chieftain twin. Still wobbly but I insisted on using block. Next time no excuse.

" we must muddley do
What we doodley do
til we bodily bust" Kurt V.
It's a diddy I hum or whistle as I work

I hope you get use of it. Thanks professor!

I'm amazed at how you're building this!  :)

Please, a little more on the lathe. Does the wife just hold the drill motor firmly to the table (on a towel for a bit more contact with the bench). What are you using as a gouge rest (tool rest)?

Thanks blokes. I'm following your Barracuda Andy - good project.
Konrad, yes, that's it (except for the wife, and I do the turning on the floor - not the best for my creaking frame, but at least the floor is solid and stable). The staged photo (I needed my left hand to hold the camera) indicates approximately the areas of drill in contact with the ground - I press down hard. Tool hand also pressed hard against the floor. The tool, as I mentioned before, can snatch and jerk, but never like in this case. I've never used balsa this hard before.

I thought I'd look at my records to see when I started making spinners this way - I think the two photos show my first . . . 2012 . . . jeez how time races along. I must've made more than a dozen over the years. Of course they're only good for model subjects with bulbous spinners; typically late-piston era - but then that's a big area of interest for me. The whole notion is to get the prop hook as far forward as possible. In the case of this Mosquito I measure the hook at 6mm ahead of the nacelle. Because of the worryingly heavy weight of the spinner, the setup balances well forward of the wing L.E., approx the radiator L.E. It takes the whole wing to balance it! In the pic I'm pinching the nacelle very lightly: it's free to rock back and forth.

More pix on the way.

Stephen. P.S. it occurs to me to mention that this 'homemade' turning method doesn't (unless by happy accident) produce truly round, concentric, symmetrical results in the engineering sense - but for this application I find it good.

QuoteThe whole notion is to get the prop hook as far forward as possible. In the case of this Mosquito I measure the hook at 6mm ahead of the nacelle.

This is interesting and nicely done - is this to maximise the rubber motor length Stephen? The rubber motor would be almost captured on the hook inside the spinner but may be a bit harder to put on and remove.

John

Yup, that's it, John. I've learned over the years  that the T-hook need have its arms at only a small acute angle to the shaft to keep the rubber on the hook. About 10° seems to do it. Mind you I do tie a loop of thin rubber round the motor, tightly, and push it up to the hook after installation and lubing. Yes, the motor can writhe into a coil inside the cone (depending on motor length V. hook-to-peg length), but I put a loose sleeve over the motor right behind the hook, and this stops any jamming. I mentioned before that I file the ends of the T-hook arms - that's to stop the rubber being 'scratched' by the ends as the motor is installed. Yes, it's less easy to put on with a pre-lubed motor - say you have 4 loops - you get 2 loops on one arm of the T, collect the other 2 loops and press them  over the other arm, by which time the first two have slithered off their arm. That happens sometimes, but I've learned to mitigate such irritations. I'll try to take some photos of this.

It's not so much to do with the length of the motor, but getting the weight forward.

Stephen.

From yesterday:

These pictures are a bit muddled, some of them relate to one of the spinners or cones; some to the other. I had intended to make the two concurrently, but it didn't work out.

The second of the plastic cones is plunge-moulded from 1mm plastic card. Unfortunately the balsa form is very out of true. I can't remember its provenance - it wasn't made for the test model. From 0.5mm (20 thou) plastic card, a narrow flange is cut using my version of a compass cutter. Here are the cone, the flange with central disc not yet removed, and the second spinner.

I have an offcut of thick ply with a length of 1.2mm piano wire fixed into it and projecting exactly vertically relative to the surface. This has several uses, but here it's ensuring the true fitting of the 1.2mm I.D., 4mm long, brass bush into the top of the cone. The thin card underneath has a circle drawn on it. The fact that in one place the rim of the cone departs from the circle isn't because I've mucked up - it's that the rim isn't circular, due to the inaccurate balsa form that moulded it. There's a similar gap on the other side - the rim is an oval. Funnily enough, I don't think this matters. So long as the bush is perpendicular to the plane of the cone's base, and at the centre of the oval, all should be well.

Now then; the other brass bush has to be fitted into the spinner. Trouble is, the hole in the spinner made by the spindle/bolt used for turning it, has a diameter greater than the 2mm O.D. brass tube. The quickest, most convenient solution I've come across is to use rolled paper. The very end of a long narrow strip of paper is fixed to the brass bush with thin CA. Then the bush has the tip of a cocktail stick jammed into it, and by turning the stick between fingers and thumb, whilst keeping the paper strip under some tension with the other hand, a nice tight roll builds up around the brass. Then thin CA is soaked into the paper roll. The result is easily a match for hard balsa in terms of strength/stiffness.

The paper-clad brass bush is then pushed home into the spinner and the jig is used to check trueness. There is a circle on the white card (pencil lead from my schoolboy compass) - but the spinner matches it so closely that it's hard to spot. The bush/paper is fixed by dosing around it with thin CA, inside and out, which penetrates the balsa well.

Back to the cone. Light shining through the cone shows that at the tip there's a balsa spacer inside, capped off with another 1mm plastic card disc, so the brass bush is fitted into a plastic/balsa/plastic sandwich. It's a tight fit, and thin CA doesn't penetrate a plastic/brass interface well. So I drilled a very small hole right thru the sandwich, abutting the brass, and ran CA into it. It flows all around. It's funny to watch a sizeable drop of CA quickly vanish into the tiny (c. 0.4mm) hole.

Light from the other side of the cone shows the last part - a ring of 0.5mm plastic card that is what locates the assembly into the front of the nacelle. This ring of card has one edge chamfered to fit the slope of the cone, so it's CA'd both to the inner edge of the flange, and to the sloping wall of the cone.

Finally, the correct diameter hole is carefully shaved then sanded into the nose former of the nacelle. A socket set provides all sorts of useful diameters around which to wrap abrasive paper, for jobs like this.

Stephen.

Six propeller blades? I wish someone had told me - I'd never have started this caper.

First, another use for the 'lump of thick ply with a post sticking out' jig. This card has radial lines inked at 120° to mark the spinner for the blade sockets, complete with a nifty tab that folds up, allowing me to draw vertical lines at the relevant spacing. Then there's another card template giving the outline of the socket. I've increased the socket angle - requiring a new template - from around 40° to around 50°. I had a sense from the test model that some more (coarser; higher) pitch might work. The 'steeper' blade sockets should give a blade pitch at 75% radius of about 30°. That's not unreasonable - but now I see the result, it looks pretty radical. We'll see.

Cutting the sockets in these extra-hard spinners was an extra-hard job.

Blade blanks cut from 0.8mm hard balsa . . . except that this particular sheet is 1mm thick. I bound the blanks three at a time to the former. Usually I use cold water for balsa-forming but given the thicker (1mm), hard wood, I poured boiling water over them and soaked up the excess with a cloth before binding. I suppose in theory I could have done the six blanks in one go, but three at a time seems safer. Because of the thickness of the stack I gave 'em two hours in the hotbox.

A blade former I made. Previously I've used twisted aluminium strip to give blades the twist they need, or I've done it by freehand manipulation - 'in the air'. But for mass-production I thought a proper helical former would be good. It's shaped with a small amount of chordwise curvature - away from the root - to impart some concave undercamber.


Next came the root reinforcements. Balsa is sanded to a wedge, so that the outer, straight edge of the  root stiffener is thin. Then carbon tow (from some carbon cloth) is chivvied into a fan and wetted out with thin CA. The picture shows this perfectly . . . only thing is, I'd glued the carbon to the wrong side of the balsa. I get days like that . . .

A root stiffener is tacked to the back of a blade blank with CA, then the blade is shaped, freehand. The shaping is all on the top of the blade.

Then the blade is painted with CA. This job is too big for the various metal CA applicators I use, so I turned to cocktail sticks. Before long these build up a jagged crust of dried CA on them, which can scratch or gouge balsa, so they need to be replaced. I think I used two, at both ends, for this job. Also I tend to do this at arm's length, coz the CA can be in a fuming mood. It's okay with older CA but I've just opened a new bottle and it 'goes off' with a puff of smoke. Then a blade is sanded with 120 grit (European grading method) followed by 320 or similar.



I meant to take a shot showing the sharp blade trailing edges but forgot. Last is another turned former, this time for plunge-moulding the spinner caps. Small formers like this can be turned freehand - the drill in one hand and the sanding block in the other. Standing up, thankfully not hunched down on the floor.

These pictures are mostly from Tue 12th and yesterday.

Stephen.

What an amazing build.

Thanks Gravitywell :).

This morning I tackled the awkward part of my 'front end' setup - I was going to write 'weak point of . . .' but that's misleading since it's not weak. It's just (for me) nerve-racking to do. I'm talking about soldering the freewheel in place.

First I shortened the propshafts to their correct lengths, and filed flats on either side at their ends (arrowed). I also shortened one arm of the piano wire coils, and roughed-up the inside of the hoops a bit with coarse abrasive paper. Also in the picture is a cocktail stick with which I reamed out the 1.2mm I.D. brass bushes - sometimes this can bring out quite a bit of crud, but in this case not much.

Now the scary bit. The hoop has to be soldered to the propshaft. First I put a slip of card over the propshaft, snugged down to the flat surface of the spinner. This is deliberately a tight seal - it's to stop the possibility of melted flux paste running down into the brass bush. This would gum up the works. I've had this happen in the past. I tried various solvents to budge it - annoyingly, I found that solvents liquefy the flux, and everything seems freed up and 'good to go' . . . except that when the solvent evaporates, the flux reverts to being sticky.

Then, a bit of flux paste on the relevant area, and I pressed the hoop onto the propshaft so it sits against the flats filed on the shaft. This is a weak contact - a light touch can cause the hoop to ping off, or more likely just tilt to one side. The problem is, One's got to touch it - with the soldering iron. What's more the iron seems to expand the horseshoe with its heat, leading to the thing tilting or even falling off.

I have to hold the work in one hand, and collect a blob of solder with the iron and deliver it into place.

In this case I was doubtful of a good job - the blob of solder sitting on the metal isn't a good sign - looks like it hasn't flowed. However, as the pictures show, on inspecting the reverse of the freewheel, the solder had flowed around the joint, and a good old test of its strength confirmed that the joint is sound.

Now I have to do the other one . . .

Stephen.

This p.m. I soldered the other freewheel (success 1st time also) and made the two posts that complete the freewheel catch. These posts can often simply be straight wires, glued into a hole in the spinner - but in this case the depth they have to be bedded in is only 4mm - not enough perhaps for the rubber motors that may be installed in this model. So some more wire-bending was required - this gives more area to bed the post, for a stronger result. It's glued into a slot cut into the spinner.

I forgot a crucial measurement - would the height of the freewheel above the spinner fit into the spinner cap? Normally my freewheels are 6mm high but this is a generous 8mm. That makes life easier. As it turns out the spinner cap just clears the freewheel. Now I have to make some arrangement to fit the cap onto the spinner.

Stephen.

Whew!! :D Just as well it's not a trimotor or B17!

John

Quote from: OZPAF on May 17, 2026, 03:50 AMWhew!! :D Just as well it's not a trimotor or B17!

John

;D  ;D  ;D

Yeah I leave all that stuff to Dave Dputt7 and his ilk! Actually making the blades three at a time was no drag. In theory one could stack the blanks six high on the blade former, but my instinct was that that might cause problems. As it was I found that three blades took 2+ hours to dry in my electric incandescent bulb hotbox.

Nothing done over the weekend - but later yest. and early today I finished the other freewheel by adding the vertical post, and made the locating tabs for the spinner caps.

It's starting to look like an aeroplane :).

Stephen.

What a beautiful Mossie, Stephen!!
I very much like your building technique.
Seems very light too!
Following with great interest,

Cheers, Ramses

Fantastic workmanship and innovative approach. I am really enjoying this build thread.

   A real credit to you Stephen, it looks fantastic!

Stunning!

Stuart

Ta chaps - I just hope that I can get over the main hurdle - tissue covering . . .

Quote from: ramsesSeems very light too!

I forgot to mention that the model as seen in the photo weighs 43g. Hmmmm . . . I just hope the covering is light!

Now, about that covering. One of the jobs of the test model was to discover whether I could cover relatively complex curved surfaces with tissue. That's not really my thing. In fact from memory it's a first - for curvy fuselages and nacelles I use balsa/aliphatic sheet as a rule.

Well, yes, I could cover relatively comp. . .dah dah dah . . . but, I was using Asuka tissue.

I don't like Asuka tissue. Unless I've used Asuka from a dodgy batch or something, there's no remote way I consider it to be a like-for-like replacement for Esaki. It's rough (no shiny side, and even Esaki's rough side is smoother than Asuka); it's more porous than Esaki. However, it's sloppier than Esaki, and it occurs to me that my ability to cover compound curves could be down to that sloppiness.

I don't want to cover this Mosquito with Asuka. I have a few Esaki sheets left but certainly won't be uusing them for experimentation. Much (most) of the airframe is single-curvature. So, I'm pondering how to do this job - Esaki and Asuka for different parts? Meantime, it so happens that I've nearly run through the few Asuka sheets I bought, so I need new tissue good or bad. There's an online shop offering 'lightweight Japanese tissue'. I guess that will turn out to be Asuka, or perhaps the twice-as-heavy type tissue, that people who don't specialise in small FF modells consider to be 'light'. But I'm ordering some anyway.

Stephen.

Have you tried Dilly tissue?
Richard Crossley gave me a tip about Dilly tissue.
It has a dull and a shiny side like Esaki.
I myself  haven`t worked with Esaki, but Richard says Dilly tissue is a very good alternative.
I recently tried the Dilly tissue and liked it so much i ordered some extra sheets.

Cheers, Ramses

Hello Stephen

Have you tried the Dilly Jap tissue perchance ? I have some in my loft somewhere but haven't used it since my stroke ! If you look at the back pages of the New Clarion ( see the SAM 1066 website) you'll find it advertised and from what I recall it isn't expensive. It also featured in HPA (Mk 1) about 3 or 4 years ago.



Peter

ps Ramses beat me to it !!

Okay fellas, thanks for the tip. I'll get some Dilly tissue too.

Stephen.

I'm not sure you should consider covering compound curves with Esaki "experimental". It works fine if you put it on wet. I admit I haven't done it much.

If you are going to paint, would it work to use really thin mylar over the sheeted parts?

Quote from: lincolnI'm not sure you should consider covering compound curves with Esaki "experimental". It works fine if you put it on wet. I admit I haven't done it much.

If you are going to paint, would it work to use really thin mylar over the sheeted parts?

Thanks for the advice Lincoln. I meant that it's experimental for me. I know others can cover pool balls with tissue and without a wrinkle or a seam - but I ain't one of 'em. My test model showed me that I can cover a Mosquito nose with Asuka, but my feeling is that Esaki might be less accommodating. Mylar - hadn't thought of that. It's so far outside my knowledge that I'll probably leave it for this model.

I looked into Dilly tissue a bit last evening. Two sources - Mike Stuart's site and a thread on RC Groups - mention that Dilly tissue has little wet strength. I think that puts it out for me as my whole covering system is predicated on water-soluble glue and damp or sometimes wet tissue.

Stephen.

Also available direct from Martin...
Publication2.png

Finally - I've ordered the 'lightweight Japanese Tissue' I mentioned up the thread. It took me so long because of umm-ing and aaah-ing about what to do, and then it takes me days to get the padlock and chains off my wallet (anyone remember The Goon Show?).

It occurs to me that I haven't mentioned why I'm making this model's fuselage and nacelles from moulded balsa sheet with tissue covering, as opposed to my usual wheeze of using balsa/aliphatic sheet. Largely it's because making sufficient BA sheet for a model this size is choresome. I can't remember how I felt turning out the sheet for the 24.5" Spitfire I made a few yrs back, but I didn't relish the idea regarding this 27" model, with its two big  nacelles as well as fuselage. I think the weight of the two different methods ends up about the same for 'bodies' (fuselages, nacelles), but wings made from BA sheet are typically about half as heavy again as S&T wings. BA sheet looks better for imitating stressed-skin subjects as it can be scribed, embossed, and have holes cut in it. But for the super-smooth Mosquito that doesn't apply.

Stephen.

The 'Japanese lightweight tissue' arrived  today - no good. Gift wrapping only. It has a distinct wrinkly finish, and in seeing whether this might flatten out with wetting-stretching-drying, I found that it has little or no wet strength, depending on how you'd define 'strength'. It weighs just under 18gsm, by my measure. I did buy a new razor saw and some larger-bore al. tubes though, along with the tissue, so my order wasn't completely wasted.

So . . . looks like I'll have to love Asuka. I will also experiment with the heavier tissue I use for binding balsa to forms/plugs/moulds - this has shiny side; crisp texture; wet strength, and weighs 20gsm as opposed to Asuka's 14gsm (my measurements). This heavier tissue might disqualify itself by soaking up more paint than the thinner Asuka, thus compounding the weight penalty. But then maybe not - it appears less porous. Then the question of how powerfully it shrinks . . .

Stephen.

My normal practice is to pre-stretch tissue by laying it on glass, wetting it so that the tissue is pretty much floating on a film of water, and - using a wide brush, along with fingers and thumbs - to stroke all wrinkles out of the tissue. At this point the tissue has stretched a good deal above its original, dry, dimensions. Then the edges are clamped down so that the tissue can't shrink back to its original dimensions as it dries.

Then I airbrush or hand-paint the tissue on the glass, and use it for covering.

The sheet of Asuka on the glass in the pics is from last summer - intended to cover a Piper Pacer. I dug it out to photograph - and remembered that a) it's a coarse, matt finish - and b) that when using the wide brush the brush scuffs up the tissue (worsening the coarseness and presumably weakening the tissue). This doesn't happen with Esaki. The last pic, shot at a shallow angle to the surface, shows the gritty texture.

What to do? I could go back to using a frame like the one in the photo - tissue is taped to the edges of the frame, wetted thoroughly, and then those wooden battens can be pressed downwards, which stretches the tissue. This works, but is clumsy. And this frame is too small to produce the Mosquito's wing panels. I'm just drifting around half-heartedly mucking around with Asuka and the heavier-but-smoother tissue, trying to come up with a new idea.

Stephen.

Quote from: Prosper on Jun 08, 2026, 01:34 PM...this frame is too small to produce the Mosquito's wing panels...

Evening matey.

Dunno if it's any help, but Hobbycraft sell pre-stretched artists' canvases for not many of your Eeengleesh pounds.  They're cheap enough* that you can bin the canvas and keep the stretcher.  I use an A2 one, but they do larger sizes.

I fix the tissue to the frame with glue stick, teasing out as if I were covering a wing or similar.  Let the glue dry for several hours before spraying with water and then set it to one side for however long it needs to dry out properly.  The pic. is from the Chiribiri build.

*And cheaper than buying the wood and making your own.

ETA - Spray bottles. Those sold in Boots' hairdressing section have a very, very fine spray and are under a fiver.  Recommended.

Hullo Lurk, I must get one of those atomiser spray things.

But regarding the canvas stretcher, I have a problem. When I joined HPA I read of 'pre-shrunk' tissue; but people always described what you have - attaching tissue tautly to a frame of some sort then spraying water. The tissue sags, then regains its tautness as it dries. What has changed? I tried this, and found that it didn't make a distinct difference over using 'un-pre-shrunk' Esaki. Maybe I was misunderstanding something.

Anyway, I wanted to tame the fierce shrinking tendency of Esaki so attached it to a frame that can be stretched whilst the tissue is wet (see the crude frame pictured in my above post - it was only intended to try the idea but I kept on using it). The tissue is then demonstrably stretched, and can indeed be stretched to the point of lifelessness (as in no potential shrinkage left: about to split . . . this is not good generally). Another way of stretching tissue is to make it really wet, lay it on a slippery surface like glass and tease it out with a brush, then clamp the edges so that it can't shrink back to its original dimensions. This is where I find that the brush scuffs up Asuka.

The basic idea then, is to pre-stretch the tissue but leaving some spring in it; painting it as req. whilst it's still on the frame, and then applying it damp so that it still has some shrinking ability to beat the worst of my wrinkle-inducing maladroitness - and damp also to increase the working time of the glue I use before it 'grabs'.

I guess this all describes a specific start-to-finish technique. Others have the whole practice nailed, whether based on glue-stick, dope, PVA or whatever. But however people do the job  I've never understood the 'pre-shrinking-on-a-frame' initial stage.

Regarding the sandpaper-look of white-airbrushed Asuka, I dug out this photo of the 16" span Piper Pacer I made back in 2013 - see the nice shine on the wings - not the sticky wet-look gloss that comes from varnish - just Esaki and acrylic paint. I will not be covering my new, larger,  Pacer in sandpaper.

Stephen.

Quote from: ProsperHullo Lurk, I must get one of those atomiser spray things.

As sold at Boots the Chemist (https://www.boots.com/boots-water-spray-bottle-10363635)

You'll probably have to toddle off to your nearest shop to get one.  MrsL wanted one for the ironing but couldn't order one on-line and had to borrow mine until our local shop had some in stock.

Quote from: ProsperBut regarding the canvas stretcher, I have a problem...tissue sags, then regains its tautness....

I am a bear of very little brain and what follows may be utter tosh, but my understanding is that by shrinking on a robust frame rather than your delicate flying surface you are carrying the most warp inducing stage of the tissue application process with no risk of buckling that component.  There will still be some "shrink" left in the tissue afterwards, but most of it will be "used up" so when you apply it to your component you can still get a little bit of shrinkage with (gentle) steaming to take up any slack, but it won't be pringled.

After (pre)shrinking the tissue is tauter than before, honestly. You can hear this if you strike the frame with your fingertips.  Before the spray/dry cycle you'll get a dead sound and maybe a very slight rustle from the tissue even if it's not obviously slack. Afterwards it sounds like a drum head and you'll get a definite "boom" when you strike the frame.  The shrink is really obvious if you use corrugated cardboard frames - which I do, see the Chiribiri thread.  If you don't pin the frame down while the tissue is drying it will curl under the tension.

Quote from: Prosper...tease it out with a brush, then clamp the edges so that it can't shrink back to its original dimensions. This is where I find that the brush scuffs up Asuka....

Have you tried gluing long strips of (say) 80gsm paper to each edge and using those as anchors/tenterhooks to pull the tissue out?

Thanks for taking the time to explain, Lurk.

I might find myself in the vicinity of a Boots the Chemist sometime in the next ten years . . .

Your percussion testing has convinced me, and the corrugated cardboard evidence. I shall experiment. Shrinkage mostly 'used up' is what I'm after. I haven't tried gluing paper to the edges of the tissue panel as handgrips/anchors, but have tried masking tape for same. Masking tape doesn't do the job very well - get the tissue panel taut across one axis, then tugging the tissue crosswise induces waves or wrinkles in the first axis.

I obviously need to review this whole matter - will report in due course.

Another option for the Mosquito is to use my largely vanished stock of coloured Esaki. The model will be mainly dark shades and I can airbrush white where there are to be national insignia and squadron markings etc. The trouble is, I'm saving the Esaki for 'that special model' (or models).

But, 1) What makes me think that this isn't that special model? 2) How will I know when what is that special model comes along?

Now I know how teenage girls in lo-ove feel :D :D

Stephen.

I suppose, adapting the words of the old advertisement, if it's worth building, it's worth Esaki

Quote from: Jmk89. . .if it's worth building, it's worth Esaki

Yeah, but does that mean that without Esaki, it's not worth building? This is the dilemma . . .:)

Here's a series of pictures to show my tentative experiment inspired by The Lurker's comments on pre-shrinking tissue. I used white Asuka for this.

I found an ancient picture frame that was a useful size. I can't remember what was in it - I think it might have been that photogravure portrait of great aunt Eglandina - the portrait that used to scare me so much as a small child. It was that hooked nose and that fierce scowl, mostly, I think . . . what? . . .sorry. Drifted off a bit there. Yes, a picture frame, and absent a Boots spray I resorted to my old spray diffuser - you blow thru it and the venturi effect lifts water up and sprays it. it's a coarse spray but OK for this I think. I attached the tissue to the frame using sellotape. The grain is parallel to the shorter sides of the frame. A few wrinkles, but not too bad. Later, after a good soaking with the spray diffuser, I was disappointed to see that the tissue split upon drying. It wasn't that taut to start with - another indicator of the inferiority of Asuka if you ask me. The picture showing the split tissue was taken with an outside door open and pouring rain outside - it must've been near 100% humid and that's why the tissue looks floppy.

I hand-painted a white rectangle on the shrunk tissue. This was to be opaque, and needed a lot of paint. Then I masked this white patch with a rectangle of draughting film, which had been sprayed with 3M Spray Mount.

After a couple of days I blasted the whole sheet with black acrylic. My camera doesn't seem able to cope with the expanse of black, but yes, it's black. The final pic taken after removing the tissue from the frame shows that there is a sheen of sorts on the tissue. I suspect from this that it was my scuffing of the tissue with a brush that led to the sandpaper finish of earlier experiments. It's not as even or silky as Esaki IMO but will be okay for a WWII RAF bomber camo finish. Note the wrinkles persisting around the border of the white rectangle - If those don't disappear on covering, that'll be a problem.

Stephen.

Evening Stephen,

That didn't look especially successful.

As for fixing the tissue to the frame; I've tried <BluePeterVoice>sticky tape</BPV> in the past and it did not work, the tension was uneven.  If you can afford to waste another sheet of tissue try a <BPV>glue stick</BPV>. You might have to sand the varnish or paint off your frame first though.

If this approach works, Lurk, I'll buy a canvas stretching frame. I need to understand why the tissue split so easily first, though - and whether it covers the model in a satisfactory manner. All this was supposed to have been discovered by making the test model, but I guess the result was inconclusive.

I found a copy of the Mosquito 'Camouflage & Markings' publication, and in it was another picture of a Mosquito that flew through a fireball (see Malc's Post #113). Also another picture which frankly amazed me - I wouldn't have believed that control could be maintained with the whole wingtip missing.

Mixed results here: the wrinkling evident around the white rectangle largely vanished overnight, but not entirely (see top left corner of the rectangle). I airbrushed the fin flash colours this morning and the masks lifted some of the black paint off when I removed them, so there was some touching-up to do. I had thought this might happen - it's that incompatible match between a mask that sticks firmly enough to prevent underspray, and one that isn't so sticky as to lift paint when it's removed. I have yellow Frog tape, but that's way too sticky for work like this.

After letting the paint settle down for a day or so I'll see whether what I've made can be used to cover the fin.

Stephen.

Hi Stephen
              I use Yellow Frog Tape as well. But I lay the sticky side on a piece of Plastic or similar and rub the back with a finger then remove the tape.  Repeat several times until it becomes less sticky. I find it is still good enough to give a fine edge to a masked surface but prevents paint removal.

Thanks Dave. I've tried various things - mostly based on dust - like pressing the tape onto a surface dusted with cornflour - but never got a consistent, repeatable result. I'll try your method.

Stephen.

As it turned out, I made another Asuka panel for the fin. I didn't like the fin flash colours of my first effort - that despite taking some pains with mixing the colours: they just turned out too - er - colourful. The RAF WWII 'dull red' and 'dull roundel blue' were indeed dull and washed out, according to colour photos, so I took some more pains today to remix my colours. Frankly I think I could have gone further yet - the red in some WWII photos looks almost brown - but of course this is all highly subjective and debatable.

I reverted to my usual method which I call painting on glass - tho' in this case it's painting on MDF. A small panel of tissue stuck onto an MDF board with masking tape and soaked with water spray for pre-shrinking. The MDF board itself has a sheet of 'plastic covering film' stuck to it. This time there was no issue of the tissue splitting as it dried, despite being tugged reasonably taut by the masking tape prior to wetting/shrinking.

Question: doesn't the tissue stick to the backing when sprayed with paint? Answer: no. It can do - it would do if sprayed with a rattlecan, I should think. Work like this, small-scale, using airbrushes in a restrained fashion, causes no attachment.

Stephen.

After some days elsewhere, I found it difficult to get back to this model. the main reason is illustrated in the attached picture . . . my flying field. Yes, I knew that this was the way that things were headed, right from the end of March this year, but I guess I had some momentum back then that carried the build on. The fact is that it's highly unlikely I'll be able to fly this model before next Spring - the earliest time I could expect a cushioning growth of grass on the field. I flew the test model on hard ground and it survived well but I won't be subjecting this model to such abuse. I have a clutch of models ready for trimming or nearly finished - Sopwith Camel, Leopard Moth, Piper Pacer . . . The corn will be harvested in Sept-Oct I should think, after which the surface will be dirt over the winter, most likely. Perhaps the Camel and Pacer could handle that. But in the meantime my thoughts have veered towards making a model/s which can fly on my own small patch of ground, and that means v. small models or test models of one sort or another.

The last time I flew any model was in March or maybe even Feb - it was the Mosquito test model.

Anyway, I hope to keep the Mosquito covering and detailing at least ticking over. I've started the tissue covering with the easiest bits - tail surfaces. Note to self . . .  don't cover black tissue in low-light conditions . . .:o The result isn't entirely 'fintastic', but it'll do. I used my usual method of applying the tissue slightly damp (the individual pieces of tissue are lightly pressed between sheets of damp kitchen paper as in the photo), using UHU 'glue pen', which is a wallpaper paste type of glue.

I was alarmed to find how easily the tissue ruptures when using my usual gentle tugging, and stroking with the balls of my thumbs, to smooth out the tissue. See also how the oversize white squares of paint I applied as a base for spraying the blue and red, show up (in some lights) because they have a different sheen to them than the black-only area.

Stephen.