- Nov 28, 2003
- Grand Junction, Colorado
What part drives wing weight the most depends on materials and aspect ratio. If you're building a wooden wing of AR greater than AR=8 the spar is the main source of weight. If AR is less than 4:1 the skin will drive the weight. Aluminum weight proportions will be similar to wood unless you use a piece of pipe for your spar then the spar will always be too heavy. If you use carbon fiber for the spar it doesn't become the main weight driver until you get to AR much higher than 10:1. Carbon is cheaper than aircraft grade spruce so there's no good reason not to use it unless your budget only allows aluminum. E-glass is inexpensive but the weight will be pretty close to wood. S-glass costs more than E-glass but is strong enough that a well designed spar will be a bit lighter than wood.The downs sides to me are that structural weight of that type of lightly loaded wing are often driven by weight of skins and glue and preventing buckling as much as spar cap weights and bending moments..it might be hard to realize the savings.
As for skins and ribs: At the speeds you're likely to see in an ultralight styrofoam is adequate for ribs and you can hot wire cut sheets for skin core material. I've had waste material that I could see through and know of one guy who's making styrofoam sheet less than 1mm. Many people will tell you that foam absorbs a lot of epoxy but hot wire cutting seals most of the pores that soak it up and a skim coat of dry micro reduces the density of the layer in contact with the foam.
I'm not visualizing the problem here. Many high wing airplanes have a transparent wing panel above the cockpit. It should be high so the fuselage doesn't mess up the working side of the wing. It's also a plus to let the leading edge stick out a few inches in front of the cockpit. In fact the cleanest configuration would be a pylon of length about equal to the fuselage diameter but that's impractical.Also a big taper ratio means a big root rib that can potentially be hard to cleanly attach to a fuselage or pod.
That's only true if the planform is elliptical and not twisted but that wing would also have a wicked stall.in the case with a conventional tail it wouldn't be messed with by pitch control surfaces. but even so the distribution appears to change with alpha. (unlike the elliptical)