sousap

Hi all,
For my next model I want to build my own foam wing.
I will be one piece with about 50in and ailerons. Trainer kind electric model.
I'll use foam boards from construction materials.

My questions are:
should I reinforce with pine spars and balsa starboard/port?
should I cover it with thin balsa sheet?
If I want to cover with balsa how to glue the sheets on the foam?

regards,
Sousap

GalenB

My Feedback: (18)

Sousap,

I think for a 50 inch trainer wing you can get away without using spars. However, I think that I would use a carbon fiber shaft of 24 to 30 inches across the middle. I would also skin the wing with 1/16 inch balsa. You can use epoxy, white glue, carpenters glue, polyurethan glue, etc. to attach the balsa to the foam. The most important thing is to ensure that the wings are flat and don't warp or twist. The most common method for preventing warping and twisting is to cure the wings in the shucks on a flat suface with enough weight to hold it all down...

I am sure that if you do a search here on RCU for info about skinning foam wings you will find lots of answers...

Al Stein

I'm pretty close to GalenB on this one... I'd recommend either sheeting OR spars... really don't need both for this plane.
Putting in spars is a bit less work and should be noticeably lighter. Just be sure you glue them in well (wood glue is good, epoxy will do the trick too, but with more weight) and I'd use a joiner in the middle. Sheeting can be put on with white glue as well -- paint the foam cores and the inner side of the sheet wioth thinned glue, let it dry, then iron the sheeting on.

A side note: in stuff like foam, a bigger plane doesn't cost much more than a small one, so if this is for basic training use, I'd consider going a little bigger... a 54 to 56" plane will often behave noticeably better than a 50" plane, it's is easier to see what it's doing, and it's systems are more reusable. Just a thought.

sousap

I'm already working on !QUOT!blue foam!QUOT! from roof thermal isolation.

I looks hard and doesn't bend easily until it completely breaks apart...

Easy to work with sand paper!

1st I've decided to add a middle pine spar. I'll cut the wing in 2, front and rear part (transversal cut I think) and glue it to the spar (4x20mm).
2nd I'll use balsa for the ailerons and to some reinforcements on the wing ends
3rd so far me tests with withe wood glue are not OK, I'll test epoxy and polyurethane glue next evening
thanks for the inputs
Sousap

planebuilder66

My Feedback: (8)

If your going to rubber band the wing in place you'll have to sheet the top center or glass cloth the center section so the rubber bands will not dig into the foam and if your using wing bolts you'll have to make the required reinforcments to the wing for the pins and the bolt-down area, a plywood bolt plate works great. Use polyurathane glue on the blue stuf and weight it down on a flat surface to prevent warping, the weights can be made by using sand, lead shot or B.B.'s in medium plastic bags, they form to the surface that they are applied to.[:-]

DBCherry

My Feedback: (4)

Sousap,
Go to EZone and look at the Foamie Forum. (I think it's still called that.)

There are a lot of people building electric planes out of "Fan Fold Foam", as it's come to be called. (Or F3) They're even building scale type aircraft, and some of them look pretty amazing. They can tell you how to fold the foam so it makes a rounded leading edge. They also make a spar, or ribs, out of the foam. No need to cover it with sheeting or anything else.

http://www.ezonemag.com/

Good luck,
Dennis-