Which Way is That Thermal?

ContestID67 wrote:
I was sent a link to a gadget some college engineers-in-the-making
built. http://engenius.sece.rmit.edu.au/Abstracts/Page601.htm. It
tries to detect which way a thermal is based on temperature differences
between wing tips. Bright boys.

I have two questions;

1) Have there been other gadgets created to do the same thing? How
well did they work?

2) What do you use to determine if the thermal is on the left or the
right? This is the wing up or down when its near the thermal debate.

Thanks, John

Nothing new there, That system has been tried at least 25 years ago.
It intrigued me, as an electronics engineer just beginning to fly,
but the consensus of the "big boys" at the time was it wouldn't
be sufficiently accurate or too sensitive to random variations
or some other problems.
...lew...

Lew Hartswick wrote:
ContestID67 wrote:
I was sent a link to a gadget some college engineers-in-the-making
built. http://engenius.sece.rmit.edu.au/Abstracts/Page601.htm. It
tries to detect which way a thermal is based on temperature differences
between wing tips. Bright boys.

I have two questions;

1) Have there been other gadgets created to do the same thing? How
well did they work?

2) What do you use to determine if the thermal is on the left or the
right? This is the wing up or down when its near the thermal debate.

Thanks, John

Nothing new there, That system has been tried at least 25 years ago.
It intrigued me, as an electronics engineer just beginning to fly,
but the consensus of the "big boys" at the time was it wouldn't
be sufficiently accurate or too sensitive to random variations
or some other problems.

It might be more practical with today's sensors, far greater computing
power, and electronic attitude indicators that might let you remove
temperature changes caused by bank angle. Or maybe there is a cheap
lidar unit that can detect nearby air motion: mount 3 of them in the
cockpit, pointed in different directions, and maybe get a clue about
where the air is going up and down.

--
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

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

Lew Hartswick wrote:
ContestID67 wrote:
I was sent a link to a gadget some college engineers-in-the-making
built. http://engenius.sece.rmit.edu.au/Abstracts/Page601.htm. It
tries to detect which way a thermal is based on temperature differences
between wing tips. Bright boys.

I have two questions;

1) Have there been other gadgets created to do the same thing? How
well did they work?

2) What do you use to determine if the thermal is on the left or the
right? This is the wing up or down when its near the thermal debate.

Thanks, John

Nothing new there, That system has been tried at least 25 years ago.
It intrigued me, as an electronics engineer just beginning to fly,
but the consensus of the "big boys" at the time was it wouldn't
be sufficiently accurate or too sensitive to random variations
or some other problems.
...lew...

This measurement technique has never been shown to even work, let alone
be supperior to existing variometers (which it would have to be by a
large margin to justify running wiring thru our wings, although that
might be done by the manufacturer; but they won't do it unless there is
a demand for the device). Personally, I think there are other methods
that will work significantly better than present technology that don't
require you to run wiring in your wings (which would have to be
connected and disconnected every time you assemble/disassemble, which,
in turn, requires an additional preflight inspection).

On the direction to turn: at the last convention I listened to Tom
Knauff declare that most glider pilots don't know which way to turn
into a thermal; the correct direction, according to Knauff, is towards
the down wing because sinking air surrounds a thermal. I am like Eric -
I turn towards the up wing. If Knauff is correct, I should be missing
the thermal (on the 1st turn) well over half of the time, and I am not.
Most of the time I do not immediately commit to the turn (of course,
there is occassionally those 10 kt monsters where there is question),
and actually like to turn slightly away from the direction that I think
the thermal is. The concept here is to find the boundary of the thermal
and to stay inside of it; if you search for the center of the thermal I
think you will end up flying thru it and turning too late, forcing the
glider into the sinking air around the thermal. Once I know where the
boundary is I turn into the thermal, gradually tightening the turn
until I am getting optimum climb. Ideally with this technique you will
seldom fly thru the center of the thermal, making it easier to center
the glider in the thermal. This is also helpful in identifying
streeting, since you turn only once you detect that the lift is
definitely falling off.

Tom Seim
Richland, WA

At 18:36 06 September 2006, Eric Greenwell wrote:
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.


OK I'll bite. What good reasons do you have?

Gary Evans wrote:
At 18:36 06 September 2006, Eric Greenwell wrote:
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.


OK I'll bite. What good reasons do you have?

I thought you'd never ask! Part of it is some of the thermals will be
entered close enough to center that both wings will rise (20% of them?);
in that case, I circle in my favorite direction. So, if I just flew
randomly about, I'd be circling 40% to the left and 60% to the right.

But, I don't fly randomly: I often have a good idea of where the lift is
(cloud, bird, ridge, dust devil), so I fly slightly to the left of it.
That ups the percentage of thermals on the right (or center) to about
80% overall.


--
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