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Old September 6th 06, 06:50 PM posted to rec.aviation.soaring
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Default Which Way is That Thermal?

Perhaps I'm fooling myself, but I believe in most cases that the
sensors in my butt can distinguish between a wing being pushed up and a
wing being pushed down.


Frank Whiteley wrote:
While cruising, one wing raises and the other lowers, left or right?
For discussion's sake, let's say the right wing's up and left wing
down. This can be caused by lift at the right wing, or sink at the
left wing.

When we have good thermal indicators in clouds, most of the time while
heading for that marker we encounter sink upon entering the thermal,
and sink again on exiting it on the next cruise.

So a down wing may well indicate that the thermal is just a bit further
in that direction. If you turn towards the raised wing, you may, as
Bill points out, also find the thermal about half the time, but the
thinking is that you've already flown past the core and will take two
or three turns to center. Or, you won't find the thermal, as it was
toward the down wing. By turning toward the down wing, you'll find the
thermal, or not. If not, you continue the turn through 270 degrees and
fly back to the raised wing indication which should be nearer the core
than if you'd originally turned that direction.

The concept is that you will reduce uncertainty in locating the thermal
initially and core more quickly at least half the time and that the
strategy saves 15-30 seconds or more per climb, or quite a lot during a
XC event. Perhaps a winning strategy.

Frank Whiteley
flying_monkey wrote:
Yes, Frank, please explain this to us. I never heard that that there
was any other theory than turn toward the uplifted wing. Sure, there's
lots of theories about what to do after that. Bob Wander's "book" has
the 4-circle search method, and it seems like I read something in
Knauff's stuff somewhere, maybe in "Breaking the Apron Strings." I'm
still early in the learning process, and seem to have the best results
with "tighten the turn in decreasing lift, loosen the turn in
increasing lift. This works so well that I'm frequently seeing people
in roughly equal gliders climbing past me, so I'm always looking for a
better way. Enlighten us.

Thanks,
Ed

wrote:
Really? I had never heard of the "turn away from the thermal" school
of thought.



Frank Whiteley wrote:
Regarding apparent rising wings, that may not indicate anything
regarding the direction of the core of the thermal, other than a turn
may indicated.

That is, there is another school of thought on which way to turn,
especially if the goal is to center as quickly as possible in a
thermal.

Frank Whiteley