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.

Couldn't you use this same tactic when you turn towards the raised wing,
and do the 270 to head back towards where the down wing was? It seems
like that's what I do, but much more than half the time, I'm satisfied
with the results of turning towards the raised wing.

Now, I don't immediately bank into a thermalling turn, but may bank only
10-30 degrees, based on how hard the wing went up - more bank the harder
it went up.

I could look through my flight traces, list the number of climbs and the
amount of centering needed in the first few turns, and get a % for how
well my technique seems to work, but I'm not an impartial data
inspector. I hope someone will look at my flights (and other pilots') on
the OLC and make this determination for me!

Generally, I say "aw shucks" only a few times each flight, so my
subjective belief is I'm getting it right most of the time. I also turn
right most of the time, suggesting most thermals occur on the right side
of my glider, and I think there are good reasons for that.

--
Note: email address new as of 9/4/2006
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org