I think we all agree on this. I wanted to make sure that no one thinks that
a heavier glider has more "climbing power" as stated in "climb power = 5000
N (500 kgf) * 2.5 m/s = 12500 W = 16.75 HP". Our problem was stated in still
air, and we should keep it this way. We all know that we are going down when
themalling, it's just that the air around is climbing faster, and we are
pumping fuel in the glider (PE). May we add that the energy spent in a
rising bubble of air is tremendous!!.(air density is around 2.5 #/ cubic
yard or 1.2kg/m3).
At this point in our debate, I suggest that both parties agree on the
following:

-ignoring drag, and for equal initial and final speed, it is a tie
-we deduct that drag is the force holding the" lower" glider (wow!!!!how
smart!! ;-)
-any results less than 15 m (50 feet) of difference declares a tie (what we
can read on the alti.)......less than that is not worth debating!!!
-from now on, we set entry speed at 55m/s (110 knts)and final speed at 25
m/s(50knts) (more room to set proof, pro-ballasted say around 100 feet
(30m) higher)

So far, Kevin gave us the best "math proof" declaring a tie (perhaps a hair
to the light glider). Theese results are very close to simulations done by
Udo Rumpf (what sofware???).
Last week-end, David and Chris (we salute them) flew their Ventus wings
abreast to run a reality check (one wet and one dry) for ten pull-ups.
Apparently, they were dolphining in cloud street (positive varios) and one
pull-up was estimated at 50 feet in favour of the wet. we have no mention of
average height achieved ( delta V: 100 knts-60knts).

So here we are, still debating and learning from it, I believe.

Todd's theory is based on the fact that, while coasting nose-up, gliders
will fly accordingly to their gliding polar, i.e. less form drag up to best
L/D speed =more height.

We have difficulty resolving induced drag in the vertically eccelarated
pull-up phase. I am sure that the ballasted will suffer more there (F=Ma)
BQ

"Todd Pattist" a écrit dans le message de
...
"szd41a" wrote:

An empty motorless 500 kg boat is drifting on a river. Current is moving
at
2.5 m/s, so is the boat. How many H.P has the boat?

I think you want to ask how much HP it takes to move the
boat. The answer would be "None." The boat is not rising
against gravity, and not storing potential energy. It is
not moving relative to the water and not dissipating energy
in the form of fluid drag. It's the same as a drifting
balloon at constant altitude.
Todd Pattist - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)