Fred wrote:
Just got asked this question, didn't have a quick and easy answer.
How
do you explain it?
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I'll stick my neck out on this.

In gliding flight, the horizontal component of lift is our "thrust"
that enables an airspeed, while the vertical component is equal to the
weight of the glider.

Once the thermal is entered, there is an increase in the total lift
vector equal to strength of the thermal. This results in an imbalance
of forces which causes the glider to accelerate to the new steady
state.

I flew for years on the east coast of the US and never noticed this
effect until moving out west. Estrella has some strong days were this
effect is very noticable, especially in clean ships. The lowly 233
exhibits the same effect, just not as noticable.

Terry Claussen
Master CFI