Head wing cantilever.

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stanislavz

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advantage at all to orienting the skin plies like this X29?
Could you draw it better ? I will reopen my composide account and will run some numbers.

Also - i would like to try tri surface in open vsp. Like cessna with wren mod. Any suggestion on overall geometry ? For starter i will use 10% 85% and 15% of surfaces. All this will put spar of main wing in same place as my original design with rearward spar.
 

stanislavz

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One more - looks like wren conversion, have canard with span of 80" max - close to propeller diameter and kind of small chord. 1/3-1/5 of spanthat maximum. So it is more like 5-7% of total wing area, or 2/3 of it if central section is not accounted for.

Avanti with pusher configuration have more canard..
 

stanislavz

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And continuing this monologue.. In metric 1m chord. CP at 25% , cg at 0%. With 3m of tail cp distance, we could level it 1/12 of mtow downforce by tail. In a range of 40 kg in our ul category of parasite downforce. With normal cg it would add 20kg max..

So if canard would move that virtual CP of both wing to similar region it would shed only that 20kg from parasite lift, and will not make wing smaller - we have to ensure stall canard first.

No freebie here, just extra surface to make more vortex drag.
 

stanislavz

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And another think different approach. Gazzaile / mcr 01both in ulm category have wing with ~8m2 area with bigger (35% of chord, and 3/4 of span) slotted flaps, and are able to provide less than 65 kmh landing speed. Airfoil for gasaille is an ga 37316 as i was able to find..

Soo.. will this kind of wing will work similar in high wing configuration ?

And, yes i was able to find fully composite build gasaille too.
 

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stanislavz

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Some more informationon gasaille from designer itself. There are more than one set of molds circulating in France, composite version is not yet documented or official. From received photos - at least three different aproach on wing building. That minimum skin is a minimum skin of 200gsm cf / soric infusion mat / 200 gsm cf...

And that mat is heavy.

Will open another thread and post more photos, if allowed by designer.

And absolutelly love diesel solution with mechanical pump and non flamable fuel. And that 32 litres of fuel will give you a lot of distance at 7l/h consumption and 200 kmh speed.
 

trimtab

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The X-29 did some fiber orientation to get favorable bending-torsional coupling from the wing skins. When I talked with two different professors knowledgeable on the topic (while in grad school) they said that you can not do enough with skins alone - mostly the X-29 avoided excess divergence with a lot of bending and torsional stiffness aided by favorable bending-torsional coupling.

Could you do this on the spar? The same problem as the with the X-29: The spar set by its mission is much stronger and stiffer than the skin set in shear and spanwise bending, but not usually much for torsion. Wing skins are way capable in torsion, to the point where spar torsional stiffness in most airplanes can be just about forgotten about. The light way is to react torsion near the leading and trailing edges.

To make the spar work, you would need to put on a lot of plies oriented for bending-torsion coupling. You could probably make the caps this way, but by the time they are stout enough to carry all the bending with what is an unfavorable orientation for that purpose, the weight would be way high. And you would still need to do all of this with the skins too.

Anyone really interested needs to get a copy of Tsai and Hahn or Jones, learn the math, and start playing with wing skins and spars in it. They might discover a part of the design space that let's you get good coupling and light weight.

Billski
The X-29 did some fiber orientation to get favorable bending-torsional coupling from the wing skins. When I talked with two different professors knowledgeable on the topic (while in grad school) they said that you can not do enough with skins alone - mostly the X-29 avoided excess divergence with a lot of bending and torsional stiffness aided by favorable bending-torsional coupling.
I was under the impression that the wash-in angle vs load factor for the X-29 was negative. Was that not the case? I cannot find a direct statement or graphic that answers that question, and it's bothered me since the 80's in high school. Some papers claimed the torsional stiffness simply pushed divergence up sufficiently high, and other papers vaguely alluded to the bending torsion coupling voodoo that was responsible for the entire advancement.

I'd love to read a better source than I've been able to dredge up on the issue over the decades.

It seems to me that a sufficiently anisotropic material with a sufficiently weird Poisson ratio could be the basis for a design that would make the bending torsion coupling trick work completely. And although the idea is inelegant, an active system could modulate lift for low frequency instability.

Advantages? Carry through location, visibility, CLmax, and potentially reduced induced drag.

The estimates for the last one are difficult to get from the literature. The estimates range from a few percent (similar to winglets) to 20% (from a planning doc for the X-29, and only plausible for the glue sniffers). The X-29 saw only comparable L/D performance compared to other "comparable" operational aircraft except at high speed and high load factors it seems.
 
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