Wing Types

[TSOlympian]

Hey guys,
So I noticed that there are different ways of building the wings and stabilizers for WS. I saw some models that use a flat sheet of balsa or styrofoam as the wing, kind of like Elastic Launch Glider B, but a lot of other models use a balsa frame covered by tissue paper or plastic bag material. Is there an advantage one has over the other?
Thanks!

[jander14indoor]

I suspect the solid wing is stronger, but much harder to build to weight.
Framed and covered wings are the conventional building technique. Much easier to build to weight.
Either can work fine aerodynamically, though I expect a built up wing with camber will beat a flat plate wing most times. Chose the one that gets you to minimum weight as first priority.

Jeff Anderson
Livonia, MI

[Less_Incidence]

I agree with Jeff above and I highly recommend building a built-up wing (as in framed/covered). Built-up wings are also much easier to construct and require zero sanding unless you feel like rounding off your leading and trailing edges.

Flat-plate wings can be strong, but a built-up wing like I am using with spars (leading edge and trailing edge) made of small carbon fiber tubes is even stronger than a flat plate and better able to survive collisions.

[_deltaV]

The best way my team has found of building wings is by using water to form the camber of the wings. We take flat strips of 1/32" balsa wood, 1/8" wide and 6cm. long and glue them to each spar as the ribs, so it resembles sort of a ladder looking thing looking down the side of the wing, and the wet the ribs and tape the whole wing to a 6" diameter cardboard tube to form the camber. Leave this 24 hours to let all the water evaporate and when you take the tape off the wings will have a permanent camber and can now be covered with tissue paper/ultrafilm.

[bernard]

The best way my team has found of building wings is by using water to form the camber of the wings. We take flat strips of 1/32" balsa wood, 1/8" wide and 6cm. long and glue them to each spar as the ribs, so it resembles sort of a ladder looking thing looking down the side of the wing, and the wet the ribs and tape the whole wing to a 6" diameter cardboard tube to form the camber. Leave this 24 hours to let all the water evaporate and when you take the tape off the wings will have a permanent camber and can now be covered with tissue paper/ultrafilm.

How consistent is the camber along the length of the wing? I'd imagine that variation in wood density could result in varied amounts of camber particular locations on a wing. Which is why I'd imagine a lot of fliers curve some ribs the same way, make the frame of the wing, and then cover with film or tissue paper.

[jander14indoor]

There are two typical ways of forming light weight ribs for indoor free flight.

The first, strongest, and generally stable, but longer, is to mold them. See:
https://freeflight.org/DigestOnline/Tec ... inated.pdf
https://freeflight.org/DigestOnline/Tec ... bsMore.pdf
for articles on how.

The second, fast, stable, slightly weaker is to cut them. See:
https://freeflight.org/DigestOnline/Tec ... Sliced.pdf
See slide 17 of this: http://www.vanheckescience.com/.../9/0/ ... tation.ppt
for articles on this method.

Then assemble wing from the curved ribs and straight spars.

PS, I suspect a 6 inch tube to form wing camber will provide excessive curve for these planes. You really don't need or want a lot. You might have better lift with a larger tube.

Jeff Anderson
Livonia, MI

[_deltaV]

Bernard, the wood we used was really light, flexible balsa wood so the camber was surprisingly consistent along the length and there was very little springback. The cardboard tube method also allowed us to put shims under the ends of the spars to mold in the wash-in and wash-out. jander14indoor, 6" was for last year's 8cm. wing chord so it wasn't too extreme, ~.3" of camber at its highest point relative to the two spars. You're correct in saying that a larger tube would have to be used this year so the camber wouldn't be so aggressive.

[DoctaDave]

Bernard, the wood we used was really light, flexible balsa wood so the camber was surprisingly consistent along the length and there was very little springback. The cardboard tube method also allowed us to put shims under the ends of the spars to mold in the wash-in and wash-out. jander14indoor, 6" was for last year's 8cm. wing chord so it wasn't too extreme, ~.3" of camber at its highest point relative to the two spars. You're correct in saying that a larger tube would have to be used this year so the camber wouldn't be so aggressive.

.3" of camber is roughly 12% for a 6 cm wing or 9% for an 8 cm wing. It would seem that would create too much drag, but perhaps you would want to build a second wing with a smaller camber of around 5% and see if it makes a difference. Also, using 1/32" light balsa wood seems to be way too fragile for wright stuff models. I would be surprised if they would survive a rough collision. The usual method used for Wright Stuff models would be to cut the ribs from a sheet of 1/16" balsa using a balsa wood or cardboard template. Or if you want, you can also bend 1/16" wood in the same method as you described above and it should still hold its camber very well. The extra weight should not be significant at all.

Keep in mind that if you get any pieces of balsa that you have shaped around a form wet with water or acetone it may begin to return to its original shape.