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Next I duplicated the wing prototype
in aluminum. The center plate was replaced by a lighter hollow frame made from
1-1/2" wide x 1/8" strips. Standard door hinges (with nylon bushings) gave
the wings the ability to fold back. The nylon shoulder straps are a standard set I
found at the hardware store. The next strips out from center (the lifting members) were cut from 1" wide x 1/8" aluminum to give them greater strength. The outer limbs, which need to be the lightest, were cut from 3/4" wide x 1/8" aluminum. (click on the pictures for more detail) |
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1/4" nylon bushings and wide
flat nylon washers were all that were needed for the pivot joints in the moving parts of
the armature. I used #8-32 bolts and stop nuts (with nylon inserts) to let the
joints rotate freely but not loosen. Note that the large bolts in the center frame are countersunk. This is because that side of the frame goes against my back. I put the barrels of the door hinges were on the inside too, so they wouldn't pinch. This also causes them to stop at the right angle when the wings come together in back. |
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The finished wing armature, being
test modeled after a full day of construction. It took longer to find all the
materials than it took to cut, drill and put them together. Total cost, about $100
including the shoulder straps. Total weight, 6 pounds, not including the wing
fabric. At nearly a 16 foot wingspan, it's more awkward than heavy. Now I know
why birds get nervous indoors. After looking at this picture, I decided the outer limbs of the armature weren't long enough, so I extended them about a foot. |