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Re: Carbon Dragon structural limits 10 Dec 2013 21:54 #511

I sought about the concept of an ultralight glider for years, I believe this is the most practical most adaptable configuration

curedcomposites.com/glider.html

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--- In This email address is being protected from spambots. You need JavaScript enabled to view it., Kenny Andersen wrote:
>
> Well to answer the structural question, After further reflection, it might be more difficult than I was first thinking to clip the inboard skin. The skin isn't part of the spar structure, which carries the bulk of the wing bending, but it is part of the D-tube which carries the wing torsion loads. You might be able to clip it a bit, but enough would have to remain to carry the torsion loads (whatever those are).
> I think, as suggested earlier, that it might make more sense to sit the pilot more upright so that his head was just above the wing, or at least far enough that the visibility is increased like the Woodstock. This will also move the CG desirably aft.
> You are limited by the spar with regard to how far aft you can move the pilot. The only other way to change the relative aircraft/pilot CG (without adding ballast) is to sweep the wing forward a bit. My guess is that it wouldn't be such a big deal. The airfoil is the same (stall characteristics) but you move he lift CG forward a few inches. I'm a structural analyst, not a aerodynamist, so I don't know for sure, but as long as it wasn't radically changed I would expect too much behavior difference. Anyone actually knowledgeable about that?
> The other super-tempting thing is to consider something with self-launching capability. With an engine, and ballistic chute, you would be allowed 254 + 25 = 279 Lb rather than 155 Lb; plus, you'd get self-lanching capability. In that case, I would definitely want to push the wings out and add one more rib inboard. I worked it out that it was around 47 ft wingspan (I think I also allowed 24 inches for the cockpit width. In the case of self-launching, you wouldn't have to sweep the wings forward since you'd have significant weight aft of the lift CG. to balance the pilot weight, and in fact you could pretty much make a 'standard cockpit
> I REALLY like the small jet engines, but they want both nads in exchange -- not sure I can make that sacrifice...
> Thoughts?
> Kenny
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>
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> I too struggled with ways to improve visibility. Before deciding to build something else, I settled on making the Carbon Dragon seat more recumbent so that the head was below the wing. I built a plans accurate mockup of the pilot pod using scrap lumber. The recumbent position required extending nose 3-inches. This change moved the pilot's center of gravity forward making a nose-heavy glider even more nose heavy.
> > >
> > > As for visibility when circling in thermals. I shared a thermal at Harris Hill, NY with Gary Osoba. He was in the prototype Carbon Dragon built by Jim Maupin (and team) and I was in a Schweizer 2-33. I was in a medium bank turn attempting to "core" the thermal. Gary was circling with hardly any bank at all (Note: in a regular glider, Gary will bank almost vertical if needed to core the thermal); thus, Gary's circle was much larger than my circle. Gary easily out climbed me in the weaker lift ... left the thermal headed north towards Elmira and was circling in the next thermal by the time I reached the top of the thermal we had shared. I gave up trying to follow Gary.
> > >
> > > Phil's idea was interesting ... but does the wing strength depend on a nose skin extending all the way to the root of the wing? I have seen this type of solution to visibility in a few high wing powered craft but they all had wing struts which greatly reduces the need for strength at the wing root as compared to a cantilevered wing.
> > >
> > > Steve

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