ORIGINAL: Woketman
What about the flexible, floppy large aspect ratio outer wing panels? True, a proper spar will stiffen them a bit, but I was awfully concerned that those babies were gonna turn out to be an in-flight flutter laboratory in action! If you limit Vmax to 100 mph, it might be OK. But don't try to go faster! Now if you put some span-wise carbon fiber in the top & bottom: problem solved.
Mark,
I just went in a got the wing you are talking about and put it on my lap, with the root edge over my right leg, and the 1/3 point over my left leg, and pushed as hard as I could downward on the tip (wing upside down). The wing is 30 inches long, not including the protrubing tubes. With a metal yardstick over the surface, pushing as hard as I could, the outer tip deflected between 1/4 and 3/8 inch. I tried to twist the wing and it is VERY stiff, maybe offsetting the trailing edge at the tip about 1/16 inch, and it was as hard as I could try to twist. Keep in mind that this is the OUTER wing. At least HALF of the lift is accomplished by the wing center area (between the booms). So from the centerline of the airplane to the wing tip is about 45 inches. When a 737 flies you can see a considerable amount of flex to the wing. Granted this is not an aluminum structure, but stiffer composite, but 3/8 flex over 45 inches from center to tip is not bad at all. I suppose with more carbon fiber you could get it to 1/16 flex, but I don't think that this wing, with 50% lift accomplished by the center, and each wing panel contributing about 25-30% of lift would fail at all. Improvements can almost always be made, so I will make the future wings more bulletproof, and there has to be a certain amount of "overkill", but it can also get ridiculous.