new scratch built sailplane

[rcsoar4fun]

I had a set of 2m sagitta wings laying around and decided it was time for a fuse. In the name of experimentation I decided to make an EPP forward fuse, with carbon tail boom. The V-tail is shaped fan-fold-foam sheeted with contest 1/32 balsa. I like to let friends fly a sailplane now and then, I figure the EPP fuse should survive those early attempts. So far all up weight is 14.3 oz. RTF should be in the low 20s.

Kristopher

[xtc]

is that a balsa sheeted sagitta wing or is it brown covering??

BTW looks very cool,,great project

xtc

[ivo]

Yah, looks fine! And what is it on the wing? I mean that white thing on the right. It looks like some kind of breaks, isn't it?And how exactly have you made the fuselage? I also wanted to make something like this, but I was afraid of geometry by just holding and cutting it in my hand...

[rcsoar4fun]

The wing is fully sheeted with 1/16" balsa. The white rectangle is a spoiler.

The fuse is a piece of solid EPP. I made a slit down the middle of the rear, inserted the carbon rod, and glued it back together. It extends about 1/2 way in the fuse. Each side has a piece of 1/8" lite ply on each side as a mount for the wing. It is about 3/4" wider than the root rib.

I will try to get some better pics tonight.

Kristopher

[dephela]

Nice looking plane!

Dennis

[ferincr]

After seeing those wings I have a question to anyone more exrerienced than me, actually that would be to anyone...
I'm about to reconstruct an Aquila Grande and I can't get spruce here, only regular pine or bamboo that I'll give a try to make some spars to see how they feel (after Ejett mentioned in another post I placed some time ago).
Now the question is... If I sheet the whole wings like the ones rcsoar4fun has here, would that make them stronger or just heavier????
Thanks for all the input,
Fernando

[Thermalin]

Believe that white thing on the right is a lowered spoiler.. while the one on left is open
Mike

[fly1milehi]

My thought is that a fully top sheeted wing will always be stronger and a bit heavier. The Sheeting should add quite a bit of compression strength. If a builder does nothing else to the spar or sheer webs I would say the gain in strength is well worth the weight gain. An added benefit is that the upper surface of the airfoil will gain accuracy since the film covering will not 'sag' between ribs. The strength gained however will not make the wing "winch proof" for that you will need a spar structure similar to the Dr. Drela designs used in the Bubble Dancer and Allegro.
greg

[rcsoar4fun]

Here are some more pics, thanks to everyone that emailed me with comments. Hopefully these pictures will answer some questions, if not feel free to ask.

One person asked why I was using an EPP/carbon fuse instead of balsa but balsa wings. Simply because I am lazy and I think it will work. The fuse is extremely quick to build. For this type of application the wood wings are going to be nicer to look at and more efficient than an EPP wing. However, a wood fuse is a lot more fragile than EPP. An epp tailboom would be too flexible and heavier than a carbon one. The two pieces of wood along side the fuse give the wings something to mount onto and also help stiffen the tailboom mount. The carbon tailboom is sandwiched in EPP between the wood, which will give a bit in a crash, preventing it from breaking. It extends into the epp about 1" forward of the wing rod. The fuse will be covered with oracover when it is finished. And no, its not as crooked as the photos would make one think. The plywood was attached with polyurethane glue and is camfered at the edges.

The tail cores were cut from blue fan fold foam. After the outline was cut the plastic was removed they were sanded to smooth out the ripples. The trailing edge was tapered. They were sheeted with balsa attached with polyurethane glued in a vacuum bag. The leading edge will be of laminated balsa. It is very light and strong.

Kristopher