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wood single surface wings

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Taylor.S

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just a stupid question but is the a reason you cant make a single surface wing out of wood using full size ribs and such.
 

Victor Bravo

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We had something in old model airplanes called the "Jedelsky airfoil", which was almost single surface, solid balsa. But it would weigh a ton in Spruce, and cost a ton of money.

There were plenty of single surface wooden wings in early pre-WW1 aircraft, using steamed or laminated wood strips as ribs.

If distant foggy memory serves, the "Sky Baby" ultralight by Paul Rokowski was a high wing derivative of the Whing Ding, but used wood strips for ribs. It's a distant memory and I'm not 100% sure...

With all that said, it is not clear what the advantage would be???
 

Tiger Tim

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just a stupid question but is the a reason you cant make a single surface wing out of wood using full size ribs and such.
Do you mean something like a plywood sheet bent to a single surface airfoil shape, or do you mean a frame made of wood but only covered on one side?
 

wsimpso1

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No reason why you can not do it. Lots of good practical reasons why it makes a lousy airplane. By the time it has a enough lift and enough strength, it is:

Heavy
Expensive
Draggy
Lousy Stall Behaviour
Then as airspeed goes up, it gets heavier and heavier to keep flutter away too.

All the reasons that hang gliders and wind surfers and others have gone to two surface foils.
 

sming

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I'm pretty sure that windsurfers and kitesurfers use single surface foils ;) It's been tried (two surface foils) but it's always not worth it apparently (weight vs drag). Event racing sail boats don't use two surface foils.
 
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Hi , and why not going to the extreme: Here is the last paraglider, a single skin , paraglider that really and safely flies , with nice performanceshttps://www.alpwind.fr/en/school/the-single-skins-paragliders
 

Taylor.S

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I just was thinking of all the old ultralights with single surface wings but i never have seen a wooden fabric covered single surface wing.
 

Tiger Tim

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I just was thinking of all the old ultralights with single surface wings but i never have seen a wooden fabric covered single surface wing.
When you look back farther to Lilienthal and the Wright Brothers you see wood framed wings with covering on a single side. Because wood structures are different from metal ones to take best advantage of the material’s properties it was found pretty early on (about 1902) that covering both top and bottom was better to the point of being almost necessary.
 

Protech Racing

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It would be easier to use the wood as the bottom surface of the wing , run the spar down it ,and cover the top side with cloth over a few ribs.
 

rtfm

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I was thinking the opposite. Ply on the top, cloth on the bottom. The top is what produces most of the lift, so make it true. Cloth for the bottom. But top and bottom need to be covered.
 

Aesquire

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Single surface wings are used in paragliders and kite/board snow/kite today. The additional drag of the triangular bridle mounts is balanced by the lighter weight of single vs. double surface parafoils. A cross between sleds & parafoils.



The emphasis on weight is for 2 main reasons, hiking with minimal effort up mountains ( including hiking/flying races across the Alps ) & lowering wing inertia. ( to reduce the wing overflying the rider when they "park" it overhead in power kite use, & more complex issues with paraglider use )

All the LEI ( leading edge inflatable ) power/traction kites are single surface, but without the triangular bridle points, as the more rigid leading edge changes the dynamics, the bridle lines aren't needed to shape the airfoil the same as a parafoil.

The current America's Cup racing yachts use double surface fabric sails. Vertical wings, really. The aerodynamic features deserve their own thread. Performance is amazing, and designs are incredibly complex. Everything is run by pneumatic/hydraulic actuators powered by humans turning cranks. While flying on 3 foils during turns, & lift off, and 2 in "cruise" in an asymmetric balancing act. Golly!

Hang gliders, are mostly single surface fabric wings. The leading edge structure is inside a teardrop shaped sleeve, of various chord percentage. Double surface higher performance wings basically expand that leading edge pocket rearward to enclose the cross spar. ( oversimplification ) & are double surface to various % up to 100%.

The OP question? Yes. You can. But the exposed ribs are draggy. I'm assuming you want to cover the upper surface with wood, and save the weight of the lower surface. That works, but poorly. You have the drag of the ribs, and how about the spar? Undercambered airfoils have steep drag rise with speed increase. The camber tends to give high pitch moment, wants to pitch nose down, so you end up with a bigger tail. See early WW1 airplanes, & how airfoils got "fatter" yet made less parasitic & overall drag.

So you're FAR better off covering the bottom, too. Fabric is light, but won't contribute strength the same as plywood or rigid composite. So a plywood upper/fabric lower will require a heavier structure than plywood top & bottom. Which combination is heavier? That's a question in itself.
 
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Aesquire

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If your requirements are dominated by regulations, as in pt 103 ultralights in the USA, then compromise can lead to choices all wrong for other craft.

Since you have a low top speed, and a low maximum weight need, often pt 103 craft have features like wire wing bracing, light, but draggy. Wire bracing, especially with round cables, is parasitic drag that rises steeply with speed. But doesn't normally change induced drag created by lift.

So a hypothetical single surface plywood wing with wife bracing and ribs as curved strips bonded on to shape & also reinforce the plywood to take the wire attach points ( simple bolt through with tangs ) could be made with good effect.

I suspect ground handling, pushing the craft around, banging your head, etc. would give you the same kind of minimum thickness needs as modern composites. You can make it strong enough for flight loads but still be to fragile to practically use. This factor often makes the advantage of a material's theoretical strength to weight ratio not as good in real world use.
 

Aesquire

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I'm sure others here are far better at listing/defining/explaining wooden wing structures.

I'll point out 3.

Sopwith Camel ( search Sopwith Camel airfoil & look at images ) which is a Eiffel truss wire braced wing, fabric top and bottom.

Fokker D.VII which is a cantilever wing, plywood top & bottom. ( And an airfoil that is very "modern" )

The "D tube" leading edge with spar & curved leading edge skin forming a D shaped box spar, typically with ribs covered top & bottom with fabric.

Partial list, pictures that make sense.


Note on fabric covered wings WW1.



Simplicity vs. Performance. Plywood surface list...

A simple flat plywood lower surface no ribs. Hard to get simpler & worse.

Flat plywood lower surface, & ribs, no upper surface. Yep, harder & worse. Why bother with ribs?

Curved plywood upper surface, ribs to help hold shape, no bottom surface. In shape and drag much like extreme light paraglider ( see Xlite link above ) airfoil. Better by far for lift/drag but far from optimum.

Note that all 3 don't have spars, unless they're just horrid drag making spoilers.

Plywood bottom, ribs, fabric top. Easy to make, a place to hide a spar, and decent performance. Downside is the only advantage over fabric top & bottom is strength in fore and aft drag forces, which internal wire or strut triangulation can probably do lighter. Not so great in twisting.

Plywood top, ribs, spar, lower fabric. Harder to build, highest performance yet, some twisting & anti-drag strength improvement, over fabric top and bottom.

Fabric top & bottom, ribs, spar.

Plywood top & bottom.

Carved from tree solid wood. ;) Actually fairly simple in several senses. Really hard in others, too heavy for my taste. ( And every other successful designers )

Etc.
 
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