Hi...

I am building a 'D' tube type wing using 1 mm sheeting. I am happy with the stiffness this has created across the whole wing, however with little pressure the sheeting is soft and sags a little between ribs. Is there any benefit from applying dope or anything else not too heavy to stiffen/strengthen the sheeting in between ribs?

Could appying dope end up actually warping the wing if applied to the sheeting? I would greatly appreciate words of wisdom and experience

Dope is used to apply fabric. It works great. But dope, by itself will offer no strength.

D-tube construction is generally quite strong. Some shear webs would offer a lot more strength for very little weight - you can likely use the same 1mm balsa. Put them on the back of the main spars, running the grain vertically. Double up with shear webs on both sides of the spars if you're really concerned.

Next time you build sand the 1mm balsa to a finish before applying it, you'll get a much more even finish that way.

Good luck,

Joel

I have got sheer webs and they are placed between the main spars. I don't know if I've quite been understood. The wing is strong! I just want to stiffen the sheeting between the ribs cause when I squeeze the leading edge with my finger and thumb it dosen't feel as firm as I'd like.... Being only 1 mm sheeting in all

Thanks for the reply about the dope not being of any benefit with stiffening the sheeting. Maybe next time I'll just have to add leading edge ribs closer together

Cheers

What plane did you build? Scratch or kit?

Anything that you would add to strengthen would also add weight.

I figure it you built a plane that needs 1mm sheeting for the LE, then it has to be a small, lightweight plane.

You really shouldn't pick the plane up or carry it by the wing anyway. Stick to surfaces that have a bit more 'built in' strength, like the fuselage just in front of the wing, or just behind the wing. Keep a mental note in your brain not to touch the wing (hard, I know, but you have to disipline yourslfe to it )

You could also do sub-ribs that are under the LE sheeting, but do not extend aft behind the spar. It adds support to the sheeting, but not the weight of full ribs.

I disagree with one of the above answers. Dope will add a bit of strength but very little. Also, saturating any soft areas with CA will strengthen it with very little weight gain but rather expensive way to do it. Any thing that will attached the fibers of the wood together will strengthen the structure, just how much is debatable.