1/24 scale DH Mosquito for rubber power.

[Prosper]

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.

[Prosper]

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

[Prosper]

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.

[Prosper]

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.

[Prosper]

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.

[Prosper]

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.

[Prosper]

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.

[TheLurker]

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

[Mr Speedy]

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

[Prosper]

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 .

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.

[OZPAF]

The 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

[Prosper]

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.

[Prosper]

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.

[gravitywell]

This is some next level building!

[Prosper]

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.