One of the hazards of the exercise that Nigel_M and I have been through of scanning and uploading the early AeroModellers that Nigel was able to borrow from Paul Briggs is seeing a whole lot of interesting models that we would like to build!
There's only one thing I can't resist, and that's starting a new project before entirely finishing another. So my current new project is to make a version of The Black Arrow which appeared in the May 1938 issue.
Here's the plan and article (but you can find the whole magazine (https://hpa.aeromodelling.gr/plans/details.php?image_id=1976) in the Plans Gallery.
Black Arrow article.pdfBlack Arrow Plan.pdfBA photo 1.jpg
I've added a photo of the plan on the building board. You can see that I've already been unable to resist making a few changes - the wing tips and fins are being turned into laminated outlines.
One question - the original was powered by a "Paulownia-style" prop. I know Paulownia timber and I could easily make a suitable 8" prop from that and I've seen ads for Paulownia props in early AeroModellers, but does anyone know if these had any particular characteristics that distinguish them from props of the time carved from balsa?
I was also intrigued with that plan which is also available on OZ https://outerzone.co.uk/plan_details.asp?ID=1116 (https://outerzone.co.uk/plan_details.asp?ID=1116)
The construction looks great. The laminations are a nice addition. The Pawlonia prop was likely to keep prop breakage to a minimum.
ian
Maybe you already know this, but Paulownia is supposed to be heavier and stronger than balsa, though still very light. The figures quoted in the Wood Database were 18 and 9 lbs average density. I don't know if Paulownia is quite as variable, but I've encountered balsa densities between 3 and 24 lbs per cubic foot. The lightest usable balsa I've seen was 3.5 lbs per cubic foot.
Presumably, a prop from average Paulownia could be a bit thinner than one from average balsa, though not thin enough to be of equal strength. Also, if I'm not mistaken, a Paulownia prop on a model treed in a very damp location would rot more slowly than a balsa one. ;-) They use it for boats. If I was to build another boat, I might try to locate some.
If I lived on a larger plot of land, I might try to grow some and wouid have a lifetime supply in several years. (It grows VERY quickly.) At least if it can grow this far north. Apparently, there are places in the US where it can be a pest, and other places, further north, where it can grow, but not necessarily spread.
https://www.wood-database.com/paulownia/ (https://www.wood-database.com/paulownia/)
Hi Jeremy Well they say you should learn something new each day, I certainly did. When I was 8 or 9 (alooong time ago I heard my father and older brother talk about Paulownia props on rubber models. Now I thought that Paulownia a brand of prop and it wasn't until your post the other day that I learnt it was a wood (some 65 years later). Now I need to carve a prop for my 48" Avia after it broke the balsa one, I had carved for it. So I thought I will just Google Paulownia and see if I can buy some wood in Australia. Imagine my surprise when it came up Bunnings. Known as Craft Wood, I managed to buy 2 sheets of 6.5mm so I will be able to laminate my prop blank. Thanks for that! ;D
Hi Dave
If you'd like a bit of Paulownia large enough to carve a one piece prop, I'm happy to cut you a bit and post it to you (you may pay the postage, if that's ok)
Cheers
Hi Jeremy, that's a very kind offer and I'm in two minds whether to accept it. I like the idea of the laminated prop for appearance, but the one piece would be easier. I'm not in any hurry as I have a long list of things to do before I get to that also the prop is 16"dia. which is a fair lump of wood. Can I let you know later?
Dave
Quote from: dputt7 on May 25, 2026, 04:19 AMCan I let you know later?
Dave
Of course. I have a slab which is about 1800mm x 300mm x 50mm, so I doubt that I'll have got through it by the time you make a decision!
Thanks Mate! ;D
Some progress has been made:
The wing has been constructed - some variations from the original plan:
1. The top spar touches the top surface - as Dave Hipperson points out in his articles in AM recently on the Senator, this is a turbulator for free. It's also much easier than back-filling the gap with little bits of balsa.
2. The whole wing was made in one piece (leaving out the rib that needs to be sloped to generate the dihedral and then split up to insert those two ribs and then join together to make one wing.
The fuselage sides are made in the usual way - only variation is that I stuck the parasol struts to the inside of the relevant spacers and then used shorter spacers between them rather than notching out parts of the struts to fit around the horizontal spacers.
Good progress looks neat.
Ready for a motor and test glide.
I think that I will have to rebuild the tailplane with a top spar to stop the upward warp!
Here's the picture
Except it isn't there - I see it in the draft and it is within the parameters, but it just doesn't show on my 'puter.... Help!
Resize it smaller and try again
Still nothing there :-X
Try from another computer
Black Arrow 160626 small.jpg
The prop blades were carved from Paulownia which were slotted into a celery top pine hub. The freewheel is a Garami clutch.
There was no CG shown on the plan nor was it mentioned in the AM article. So I will start it off at about 1/3 of wing chord, even though there is a lifting tail.
Very smart Jeremy, could we have a few more photos please.
Here are a couple of the prop
I have built a new TP .
Exactly as per the plan but with a top spar at about 30% chord. Hopefully this will resist the tendency for the TP to generate curved dihedral as the covering (Mylar covered tissue) shrinks, which I think resulted from the unbalanced structure with only a lower surface spar.
Also, last time I covered the TP almost as soon as it came off the building board and I think the joints were still a bit too flexible when the stresses of covering were applied. So this time I'm waiting a day or two for the glue (Ickysticky aliphatic) to harden a bit more. I want the structure to be quite stable before covering this time.
Hi Jeremy. More pics please. And what is a "TP" ? I thought you just figured out how to post pics properly .... :-\ A picture is worth a thousand words .... Seriously now ....
Lastwoodsman
Richard
Sorry, Richard - TP is short for tailplane, the UK (and Australian) for horizontal stabilizer in North American.
I didn't think that pictures (or even 50 words) were needed for the point of my post. Sorry.
Here's a pair of photos that show:
1 the curved dihedral of the TP (or stab)
2 the new TP with the extra spar on the upper surface (bottom spar in the picture).
As someone who is much more verbal than visual in the way I think, and communicate, pictures often don't help me - they usually don't tell me what I'm supposed to be seeing and I often have to ask the person who shared the picture what it is supposed to be showing. In fact, I'm so strange that it is often better to show me a formula than a graph or a picture. All a case of "we're all different, pet", as my late mother would say! :)
Hi Jeremy. Have you used Icky Sticky Aliphatic much before
I got some to try and it seemed to be "rubbery" when dry, is that the problem you have or am I doing something wrong?
Now could I order 1 a photo from the side
2 a photo from the top
3 a photo from the rear 3/4
all of the complete model
No Fries to go though Thank You!
The Ickysticky aliphatic seems okay to me but it does take a day or so of extra drying to get to a sandable state.
I will take and post some more photos once the TP is covered, the fins mounted and the whole plane is ready for having its picture taken ;D
Thanks Jeremy.
The Black Arrow
Tuesday June 23 2026
Hi Jeremy. "Sorry, Richard - TP is short for tailplane, the UK (and Australian) for horizontal stabilizer in North American." - North American what?
The words Tail Plane are not too hard to spell out. How come 'TP' only includes just the Stabilizer? Does it not include the Fin and Rudder? Spell out your acronyms first, instead of assuming people know what they mean, then use the acronym, thereafter, all you want. It is a drag and a real waste of time, to have to actually ask you to explain it in this Forum - I'm sure you know what I mean ....
Well, Jeremy, you are only half way there with the pics - you just found out how to do it now after all this time ?? Thanks for actually going to the time and effort to post a couple. Try posting the max number of pics, which is four pics in one reply. I'll be looking forward to that, and watching with hopeful anticipation. You have 9 pics in 23 posts, and I see you already know how to post four pics in one reply. You don't have to wait for the whole plane to be completed to take pics of it - some people feel pressured to not post a bones pic (same vein).
And please try posting some pics of your build which show the features of your build, not just a final pic and a bones shot. You can post a haphazard pic (ie - not a scan), of the plan, without violating any copyrights, I think .... so that we can follow along ....
Lastwoodsman
Richard
PS: What the heck does this mean? ::) (sorry - looooong overdue question ....) Quote from Jeremy - "Better drowned than duffers, if not duffers won't drown " I think we are all probably waiting for an explanation on this one .... :-\ LOL LOL
Ok let's have some fun with this - let me guess.... You were a 'Hacker' duffer golfer, who almost drowned in the lake, while hawking golf balls, and you were then too embarrassed to play the game again ... Just a wild guess .... ;D
Quote from: Lastwoodsman on Jun 23, 2026, 04:19 PMPS: What the heck does this mean? ::) (sorry - looooong overdue question ....) Quote from Jeremy - "Better drowned than duffers, if not duffers won't drown " I think we are all probably waiting for an explanation on this one .... :-\ LOL LOL
Ok let's have some fun with this - let me guess.... You were a 'Hacker' duffer golfer, who almost drowned in the lake, while hawking golf balls, and you were then too embarrassed to play the game again ... Just a wild guess .... ;D
Richard, it's a quote from 'Swallows and Amazons'. If I remember rightly, it's the telegram response the children get from their father meaning they are allowed to go sailing on their own, on the grounds that if they're not good enough to handle the boat then they're better off drowned anyway.
Absolutely correct, Pete
Further progress on the new tailplane:
Photo 1 - BA TP 3.jpg
New tailplane covered in Mylar and tissue with the two original fins. The fins were removed from the original tailplane by putting the whole structure in a Ziploc bag with a teaspoon of thinners and leaving overnight. The covering has got a bit looser but the fins came away quite easily after the thinners dissolved the adhesive. It was lucky that I used balsa cement to stick the fins to the original tailplane! The points of the drawing pins showing in the middle of the left hand fin are to help locate the tailplane to the fin.
Photo 2- BA TP 4.jpg
One fin being glued to the tailplane. The drawing pins which are underneath the fin are holding the fin and tailplane perpendicular, helped by the right angle blocks (the fin is held up on a couple of spacers of balsa to allow for the heads of the drawing pins).
Photo 3 - BA TP 5.jpg
Beginning of construction of the end tail casing.
Photo 4 - BA TP 6.jpg
The original tail case casing which I am remaking for the new tail plane. It plugs into the fuselage just rear of the rubber peg and is held on by rubber bands. It would be pretty easy to turn that into a dethermaliser joint (like the one that Dave Hipperson talked about in his recent Aeromodeller articles on the Senator).
The first part of the tailplane casing has been glued to the bottom of the new tailplane on top (bottom?) of one of the centre ribs (which mirror the taper of the fuselage.
BA TP 7.jpg
Once that joint has dried, the second part (identical to the first) will be glued to the other sloped centre rib. Balsa cement (UHU Hart) is used because of the use of dope and banana oil on the tailplane covering and also because it has good grab and dries quickly.
The next steps are:
1. glue the plug piece between the two vertical spacers
2. shape two upper side pieces from 2.5mm balsa
3. glue the upper side pieces onto the top of the sloped centre ribs of the tailplane
4. sand the plug piece so it fits into the hole in the front of the fuselage.
Stay tuned for more Black Arrow excitement!
A beginning made on the next steps:
1. second part of the tailplane casing glued in place
BA TP 8.jpg
2. the plug piece glued between the two vertical spacers
BA TP 9.jpg
3. two upper side pieces shaped from 2.5mm balsa using the tail rib template to guide the scalpel blade
BA TP 10.jpg
4. the upper side pieces glued onto the top of the sloped centre ribs of the tailplane
BA TP 11.jpg
Just need to:
1. sand the plug so it fits the front fuselage
2. sand the top side pieces so they flow neatly down to the tail
3. cover the tail casing
4. add hooks and tail skid to the tail casing.
Now the following have been done:
1. The plug is cut and sanded down so that it fits in the rear hole in the fuselage
BA TP12.jpg
2. The upper side pieces are sanded down to follow the line of the upper longerons
BA TP 13.jpg
3. The tailplane is plugged into the end of the fuselage.
BA TP 14.jpg
Covered the tail covering and put the thing together to do a bit of test gliding in the back yard. No photos yet.
CG was at about 50% of wing chord (no CG marked on the plan) and without adjustment there was a straight dive. Added tail weight - needed 5.5 gms before we got a decent glide. So I added 3mm increase to wing incidence (it was set with 0 ° according to the plan) and she only needed 3 gms of clay.
Decided to put 2 or 3 coats of banana oil on the tail structure. We will see what the weight of tail plane is in the morning when that dries.
I hope to go and test out at the paddock with the KeilKraft grass tomorrow - rain permitting. Photos will be supplied!
Current weights:
tail - 7.5g
wing - 11g
fuselage - 41g (including 4 strands x 400mm x 6mm rubber)
prop and noseblock - 10.5g
Hope the weather is fine and you have a successful trial.
Too damp today. The forecast for tomorrow is better. So fingers crossed!