Cantilever Internal Braced Fabric Covered Wing

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proppastie

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Do we have examples of aircraft with Cantilever Internal Braced Fabric Covered wings......I see lots of internal braced fabric wings with struts and twin spars like the Piet. I am looking for examples of double drag wire system for torsional stiffness.....I think it is the a set of drag and anti-drag wires attached at the middle of the spars at the compression ribs.....I can see how that would stop the assembly for "racking" but am sketchy about torsion unless there are 4 wires attaching the tops of the spars together and the bottoms together, but I have not seen that.....so I must be missing something.....This would be a wing with no D-nose just spars ribs small about of aluminum at the LE to form the fabric and internal bracing wires. Am thinking the outer portion past the strut attach of maybe the Kolb or some such........throw out some names,,,,, thanks in advance.
 

TFF

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Spacewalker 1&2. Fokker Dr1, DVII. All those have beefy spars. The biplane triplane had been flown without the outer struts before the production planes added them. Not sure if space walker use wires inside. The others did not.

Open with no D leading edge or box spar, not that I can think of. Wires are not for twist control just drag/ anti.
 

ragflyer

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The best example is the French Jodel family of airplanes that use a single box spar that is designed to take all the bending and torsion loads. There are also a few airplanes that use geodesic frameworks to take the torsion load rather than a stressed skin. Also IIRC the skypup has a single spar that takes all bending and twisting loads, though it’s been a while since I looked at the plans and I may have misremembered.
 

proppastie

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Sort of thinking internally wire braced for torsion drag anti drag
Spar handle bending.
 
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wsimpso1

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With single struts or none at all and the entire wing has to be torsionally stiff enough by itself. Four ways I can think of are:
  • Torsionally stiff main spar - box structure spar makes sense, but you may have to run diagonal elements both ahead and behind the spar to prevent racking;
  • Two torsionally stiff spars - box structures and diagonal elements;
  • Plain spars and ribs, skin it with plywood and skip the internal bracing. Plywoods can go 0.070" thick, so weight is really not too bad. 0.070" plywood is 0.19 to 0.22 lb/ft^2;
  • Go Warren truss style with diagonal ribs like the Ercoupe uses between forward and aft spars. no reason it could not also be used ahead of the forward spar too.
 
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proppastie

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The Dyneema is very strong/light. 15x stronger steel for the same weight 350k psi

Less expensive than CF
 

Vigilant1

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The Dyneema is very strong/light. 15x stronger steel for the same weight 350k psi

Less expensive than CF
Does Dyneema creep? We've had some very strident posts in the past claiming UHMWPP and UHMWPE creep a lot, and other posts disputing that. If it does, expect continual adjustments if it is kept under tension.
 
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jedi

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Does Dyneema creep? We've had some very stridentsvposts in the past claiming UHMWPP and UHMWPE p creep a lot, and other posts disputing that. If it does, expect continual adjustments if it is kept under tension.
I believe dyneema does creep but kevlar does not. Paraglider dyneema lines need to be stretched on occation but that is because the outer protective covering shrinks. Stretching a paraglider line can sometimes and several inches in length.
 

Vigilant1

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The Remos G3 wing has a carbon fiber D-Cell, ribs, and fabric covering.

ETA: Oops--I forgot it has a strut. Oh, well, the same idea would work without a strut, too.
 

Richard Roller

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Do we have examples of aircraft with Cantilever Internal Braced Fabric Covered wings......I see lots of internal braced fabric wings with struts and twin spars like the Piet. I am looking for examples of double drag wire system for torsional stiffness.....I think it is the a set of drag and anti-drag wires attached at the middle of the spars at the compression ribs.....I can see how that would stop the assembly for "racking" but am sketchy about torsion unless there are 4 wires attaching the tops of the spars together and the bottoms together, but I have not seen that.....so I must be missing something.....This would be a wing with no D-nose just spars ribs small about of aluminum at the LE to form the fabric and internal bracing wires. Am thinking the outer portion past the strut attach of maybe the Kolb or some such........throw out some names,,,,, thanks in advance.
Cessna Airmaster.
 

BoKu

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Hall Cherokee II sailplane: Two relatively deep spruce spars, with wooden lath X bracing along the top and bottom of the spars at each rib bay. Spoiler alert: Not all that stiff. When I encountered one a few years ago, I could grab the tip and crank in a couple degrees of washout or wash-in with relatively little effort, and no audible distress. It kind of gave me the willies.
 

wsimpso1

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The Dyneema is very strong/light. 15x stronger steel for the same weight 350k psi

Less expensive than CF
What are you using Dyneema for? It creeps under load, should be stored unloaded, and must be retensioned regularly.

Once you have a beefy enough spar set for cantilever wings, torsion can be handled at low additional weight by either structural skins or modest beefup of the spars. Maybe even use diagonal ribs with it. Run numbers each way and do the lightest one that meets strength and stiffness.

Billski
 

proppastie

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What are you using Dyneema for?
was thinking of saving a little weight on the drag-anti drag wires (double drag wire system). Talking to Piet builder today ..... the compression ribs on it are top and bottom 1x1 wood......because of the geometry of my design which is the same as the one that failed .....any D-nose style torque prevention is lots of skin and weight .... Were the wing location and geometry different from the start it might make sense but this is the last piece of the puzzle and I am locked into certain geometry........ though is to have total internally design/braced for all loads and fabric cover. I currently have a preliminary designed cantilever spar of 15 lb.....5.33+ G limit.... one issue is there is only so many thickness of material .....another argument for composites as one can tailor the thickness.
 

Riggerrob

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But, Ref Post 7, Kevlar is more expensive than CF (and has lower tensile strength).
Because Kevlar degrades rapidly when exposed to ultra-violet light, it needs to be bonded inside any composite structure and the structure protected by multiple layers of UV-resistant paint (e.g. dope impregnated with aluminum powder.
 

TFF

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The D section is a good way to get a decent start of the airfoil. Even if it wasn’t for strength, it is helpful for aero.
 
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