I think Kevin's right. (at least to the first order).
In a pullup you trade kinetic energy for potential
energy, so (neglecting friction effects) the physics
are (mV^2)/2=mgh -- kinetic equals potential energy.

Or (solving for h): h=(V^2)/2g (the mass cancels out).

You can try to add the drag parts back in, but the
time is so short, I don't think it will not add up
to much.

I think maybe ther reason people associate ballast
with taller zoomies is because the cruise speeds with
ballast are higher. For my ship a McCready 10 pullup
yields 700 feet with full ballast, 530 feet dry, but
the speed is 15 knots higher.



At 21:00 08 September 2003, Kirk Stant wrote:
Kevin Neave wrote in message news:...
The difference in height will be negligible.

Not true. A full load of water makes a HUGE difference
in pullup
altitude gained

The glider's energy, both potential & kinetic is proportional
to Mass so the height gain for a given loss of velocity
will be the same.

Again, wrong - check your basic physics. You even
say that the energy
is proportional to mass. Therefore, more mass, more
energy, more
altitude gained. You appear to be confusing velocity
with mass.

However the ballasted glider will have a better sink
rate at 100kts than the unballasted one so during
the
few seconds of the pull-up it will 'lose' less height.

True, but the crossover point is quickly reached so
this effect is
probably negligable.

On the other side of the equation the un-ballasted
glider will be able to pull up to a lower speed, so
it's change in velocity will be greater so the resulting
height gain may be more.

If you pull up below the ballasted sink rate crossover
speed, sure a
heavy glider will gain less. But at those speeds neither
glider will
gain much anyway. The real test is what you can gain
at redline.

(My money - if I had any - would be on the un-ballasted
one)

Too bad, I love a sure thing!

Kirk Stant
LS6-b (which loves ballasted pullups!)