Chronister
Aug 31, 2003, 04:13 PM
Here's a photo of a recent project of mine. It's a Kinkade Park Hawk ornithopter fitted with EPP foam wings. The wings use the Selig S1020 airfoil developed for James DeLaurier's ornithopter studies. Everything else is standard equipment.
Initially the wing was too stiff. By making cuts in the foam I was able to increase the torsional flexibility to the point where climbing flight was achieved.
While I was able to demonstrate the successful use of foam, thick-airfoil wings on an ornithopter, I found several problems which are equally informative. First, this wing results in decreased stability. It was very hard to control the ornithopter, because it oversteered easily and it tended to lose altitude when turning. I suspect it would fly much better with conventional airplane control surfaces, because the vertical fin should restore its stability. Perhaps DeLaurier and Kempf used vertical fins on their ornithopters because the wing type requires it. I should mention that I had some wash-in cut into the wing cores. Though it was intended to improve gliding performance, it may have lessened the stability of the ornithopter.
Another problem with this design was the extreme difficulty of attaching the foam wings. Nothing sticks to EPP foam. The rear wing attachment used cable ties stuck through the foam!
Nathan Chronister
Initially the wing was too stiff. By making cuts in the foam I was able to increase the torsional flexibility to the point where climbing flight was achieved.
While I was able to demonstrate the successful use of foam, thick-airfoil wings on an ornithopter, I found several problems which are equally informative. First, this wing results in decreased stability. It was very hard to control the ornithopter, because it oversteered easily and it tended to lose altitude when turning. I suspect it would fly much better with conventional airplane control surfaces, because the vertical fin should restore its stability. Perhaps DeLaurier and Kempf used vertical fins on their ornithopters because the wing type requires it. I should mention that I had some wash-in cut into the wing cores. Though it was intended to improve gliding performance, it may have lessened the stability of the ornithopter.
Another problem with this design was the extreme difficulty of attaching the foam wings. Nothing sticks to EPP foam. The rear wing attachment used cable ties stuck through the foam!
Nathan Chronister