Jim wrote:

On 28 Jul 2003 20:43:34 GMT, (B2431) wrote:

A U-2 constructed of lead would have the same glide ratio as one
constructed of balsa wood. It would glide faster, but just as far.
vince norris

Say what?
Dave

Um, I think there's be a slight difference in wing loading which just might
have a minor affect on glide ratio. Translation: the lead U-2 would glide like
a bowling ball.

Dan, U. S. Air Force, retired

What a wonderful question. Glider pilots often add water ballast, 200
- 300 lbs I think, to their gliders to increase airspeed at a GIVEN
glide angle, thus improving the glider's penetration through the air
at that glide angle. The extra weight does not alter the glide angle
(except for very small improvements due to higher Reynolds numbers at
the higher airspeed). The glider's descent rate is increased by the
extra weight, but the airspeed is also equivalently increased so the
glide angle remains (pretty nearly) constant, glide angle being a
factor of only lift and drag, weight not even being in the
calculation.

As for a lead U-2 vs a balsa wood U-2, the lead U-2 would certainly
glide as long as its wing loading was such that its wing could supply
sufficient lift to sustain equilibrium in steady flight. The "catch"
here is probably the inclination to picture the lead U-2 and the balsa
U-2 as the same size. In such a case, if the lead U-2 were the same
size as the gliding balsa U-2 I expect the lead one would do as you
so delightfully describe, and glide "like a bowling ball".

But why would you go changing things?...if you're gonna do that
then you could have bigger wings, you could fit leading edge
slats, you could do lots to give one or the other the advantage.

I think that the only way to do these comparisons is to have big
ballast tanks fitted over the CG then play with weight.

Perhaps I'm getting old and slow but I'm having trouble seeing
how a glider (or an aircraft) can glide ...better?...
(farther/faster) when it's heavier.

I really don't follow your description about adding ballast
(above) at all...?

--

-Gord.