On Friday, February 3, 2017 at 11:15:04 AM UTC+3, Tom Claffey wrote:
At 23:39 02 February 2017, Jim wrote:
I have had a similar question, with a small difference, for many years.

My question is:

"Using only s single glider and changing only the max flying weight -
addin=
g ballast shot bags, whatever - will that glider give its pilot a greater
p=
otential thermal climb rate when heavier or lighter?"

I am aware that higher weight will alter airspeeds but that is not my
curio=
sity - other than a higher weight will raise stall speed some - which may
a=
dd difficulties for the heavier glider using very narrow thermals - turn
ra=
dius varies as the square of true airspeed, etc.



For any glider increasing the weight will reduce it's climb rate.

The concept is pretty simple :-)

If you double the weight of a glider you increase all the speeds, including the sink rate, by 40%. So maybe you go from 100 fpm sink to 140 fpm.

If the lift is strong enough that an unballasted glider climbs at 10 knots then the ballasted one will climb at 9.5 knots or so. Maybe worse. Maybe 9 knots. So 5% or 10% slower climb.

But then it gets to run 40% faster at the same glide angle.