Sopwith Pup - Scale 20", rubber-powered.

Oh, yes, I see what you mean. I hadn't thought that one through... Well, I'll just have to rise to the challenge and do as the plan says. Double-cambered it is...!

Personally, I'd go for a flat plate tailplane....after all, that's what on the full-size aicraft. It'll be easier to built, too.....

Following your build, nice choice. Boz

Pup flat tail plane?
Not according to this cut away but it is so 'thin' anyway I doubt it would make any difference.

ps This picture rather confirms its 'built up' nature. The steel tube elevator is of course flat.

I would have been made to redecorate if I did that.I ran my engines on an old wooden meat safe which held all my fuel etc as well. DC engine test stand which I still have. Klip has got my last engine to be used in it and it flew out when my dad hit the safe top with a lump of wood cos the Atom was running so fast it hurt his ears. The shaft didn't break then but did later on pushing my Vampie about. I found the prop and shaft half but lost the two pieces later some where in one of our house moves.Hence Klip going to turn me a new one using it's twin as the template. When he is able of course . I do have a Merlin but never ran it YET. Sorry to go off topic mods

One thing puzzling me is the ref to 1/32nd sheet in the camber .Are they saying Sheet the wings instead of built up wing ?

Quorneng wrote: Pup flat tail plane?
Not according to this cut away but it is so 'thin' anyway I doubt it would make any difference.

ps This picture rather confirms its 'built up' nature. The steel tube elevator is of course flat.

Fair comment Q. However, aerodynamically, and certainly at small model sizes, it can be considered as a flat plate.

I'm loving making this, it's like my A-level biology dissection classes, however, rather than dissecting to deconstruct, I'm dissecting to construct. The tailplane has the desired double-camber. Now for the tips...





The problem I have now hit, is how to bend 1/32 balsa to make the end of the wings. I've tried wetting and then heating it in a microwave, I've tried rolling it, dry, wet, hot, and with a heated round iron. I've had the balsa dipped in water overnight, but nothing seems to stop it snapping - see photo... The only thing I haven't tried is going through my selection of balsa to find the floppiest piece and try that - which I will do tonight. Till then, any suggestions will be most welcome.



Crashrr.

Crashrr
How thin can you cut the balsa?
Practice until it is so thin it will bend round the required radius and then laminate it.

or cheat! - which is what I did on my 24" one.

Grain is the answer - you must use straight grain balsa. Suitable wood, 1/32" By 3X36 can be bent in a circle dry with no treatment. Stripped to 1/8 or whatever by 1/32 and soaked in water, such wood will bend round a 1" radius no problem. You are, however, totally in the hands of the quality of wood that you can obtain.
Mike

You need some pretty soft 'A' grain balsa Crashrr, you'll find a good description of the different types of balsa on this thread:

www.aeromodellers.co.uk/forum/free-fligh...need-per-application

I described the making of laminated outlines in my Westland Woodpigeon thread, here:

www.aeromodellers.co.uk/forum/free-fligh...and-woodpigeon#59414

Soaking the wood in warm water helps, as does smearing it with white glue, putting the laminations together, then pulling them round the form. If you still find the wood breaks then either:

- the wood used is too hard,
- the wood is not thin enough, or
- the wood has not been soaked for long enough.

soaking the wood in a concentrated mixture of very hot water and household ammonia helps make the wood 'bendy', but obvious precautions need to be taken with the mixture and the wood should be washed before use.

If it still don't work, use thinner laminations (sand them down to the required thickness) with more of them to make up the size.

If it 'still' don't work, PM me your address and I'll send you some suitable balsa!

One thing about soaking in an ammonia solution (I've never found it necessary myself) - I read in an American mag a long while back that the ammonia gets absorbed and then some brands of PVA won't adhere properly. OTOH, never come across a mention of such in the UK, but Sod's law.....
Mike

I know the feeling crashrr, I've spent many times snapping bits of wood trying to get them to go round a former.

smearing it with white glue, putting the laminations together, then pulling them round the form.

this has worked for me, I've not yet resorted to ammonia.

Great links Andy , I might print out the wood selection one. It's the kind of information easily forgotten but very useful

Well, despite being shot down in flames by flu this week (and probably next week, too) I have managed to do a little aeromodelling. I finally succeeded in bending balsa! I can't be sure what made the difference but I suspect the secret was simply my choice of wood. I picked out some soft wood, cut it into 1/32x1/16 strips, left it in water overnight, then using the round shaft of a big old chisel bit (about ½" diameter) which I heated with a blow torch, I rolled it over the strips till they curled to more or less the correct shape. Having applied glue, I pinned them to the depron former. I didn't realize that the balsa grain would open up again as they dried, so I used three, however, two would have been enough.



I'm just glad I've added another useful skill to my arsenal, and can now crack on with the main wings. I did, however, discover that I've made a mistake... The ribs and riblets on the tailplane are supposed to be made of 1/32 square balsa, I did one correctly, then, for some unknown reason, did the rest with 1/32x1/16. I have no idea how I came to do this and, having been so elated at building this tailplane, which is definitely the most delicate structure I've ever made, am now feeling rather deflated... The main plane of the stabilizer should look like the elevators, and the more I look at those ribs, the heavier and clunkier they look...

Nice bit of bending and laminating crashrr. I may give the heated cold chisel after soaking overnight method a try