Bruce Greeff wrote:

Stewart Kissel wrote:

SNIP

I suppose it relates to how flat the polar curve is
above 100 kph

SNIP

Okay, I'll bite. If glider penetration describes the
ability of a ship to make progress into the wind without
falling out of the sky, is it soley a matter of looking
at the polar at the indicated airspeed? Intuition
tells me that is it, but an aeronautical engineer type
might make be look like a big dummy here.



I don't think it is that simple.

Polars are still air measures. By definition, if you are wanting to know
about penetration into wind the air is not still. Presumably a number of
factors like stability, control authority, drag caused by control
movements, rotational inertia etc. will affect how efficiently the
aircraft flies in turbulent conditions.

This has me wondering how you would quantify the difference in real
world ability to progress cross country for different gliders with
similar polar curves.

Let's take an example - Chose two aircraft with similar polars, but
radically different physical characteristics.
Say a Sparrowhawk and a Cirrus. Guess is the Cirrus will penetrate
better and hence be able to achieve longer flights in windy and / or
turbulent conditions?


Your example is hardly an example. Its a guess. Data please.
My "guess" is that you have a bias against US built gliders. However,
thats only a guess. ;-)

Shawn