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Today I did some volunteer work, screening potential entries into a
high school science fair. Lots of interesting experiments, but one in
particular caught my eye:

The student had created an RC plane out of styrofoam, balsa wood and an
electrical pusher prop. Now the experiment consisted of clocking the
time it takes for said plane to cover a distance of 100 yards, but with
two different sets of wings. Both wing sets are planar triangles (no
camber) and have the same surface area. One however had a wider
wingspan than the other. Thus one configuration looked more like a
delta wing than the other.

Interestingly enough the result was that the delta wing with shorter
wingspan travelled more slowly than the other wing. I thought D-wings
are generally less stable but faster, no !?

Shorter span would typically have more induced drag so, for the same power
would fly slower. Another difference would be exactly where the Mean
Aerodynamic Chord and Center of Gravity aligned with each wing - one might
be trimmed up a little different which will change the speed at which it
flys. A little warp or flex in the wings (I would expect the two sets to
flex differently) would also affect the speed that it will fly with no other
trim. If the chord of one wing is significantly shorter than the other, then
there are Reynolds number effects.

I'd say with a little effort, you could make either fly faster.

--
Geoff
the sea hawk at wow way d0t com
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