Which Way is That Thermal?

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

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

The vario also should indicate that. If one wing is being pushed down,
you won't stop to circle. If you do stop, it is because there is lift
at the wing that is going up.

It would be interesting to know which way the top competition pilots turn.


wrote:
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

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

"Frank Whiteley" wrote in message
oups.com...
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

Or, as I've seen in OLC .igc files by top pilots, fly straight through the
thermal to evaluate it, then turn 270 degrees AWAY from the side where they
think the thermal is and then reverse turn direction thus placing the final
circle two turn diameters back on track offset to the side where the
strongest lift was. The emphasis seems to be good thermal selection vs.
fast centering.

Alternatively, at least one pilot will sometimes perform what must be a
modified Immelmann since the course reversal, as seen on SeeYou's map view,
is a zero-radius turn while gaining 800 feet in the pull-up. This entry
showed an 80 knot IAS reduction in 12 seconds.

However, it's more likely these guys don't use any specific maneuver - they
just KNOW where the lift is and they're not shy about going for it.

Bill Daniels