Sharing a thermal

Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift? I seem to have the biggest problem at the top of the thermal
when the other glider has flattened out the bank angle and seems to
stay in better lift.

"Hal" wrote in message
om...
Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift?

Use the other glider as a "zero time constant vario". When you are opposite
the other glider and his climb is at the greatest, reduce your bank to swing
wide on the opposite side of the thermal then tighten up again. Learn to
control airspeed by sound and use an audio vario so you can keep your eyes
on the other glider.

Reducing bank angle from 45 deg to 30 degree will double your turn diameter.
If you resume a 45 degree bank after 180 degrees of turn, you will have
moved the circle center one diameter toward the stronger lift. This gentle
correction will let you keep the other glider in sight.

He should follow your move to stay opposite.

I seem to have the biggest problem at the top of the thermal
when the other glider has flattened out the bank angle and seems to
stay in better lift.

I have the same problem. I think they are just better than I am. I avoid
the problem by leaving the thermal before reaching the top pretending I am
using the stronger lift band.

Bill Daniels

Bill Daniels wrote:

"Hal" wrote in message
om...
Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift?

Use the other glider as a "zero time constant vario". When you are opposite
the other glider and his climb is at the greatest, reduce your bank to swing
wide on the opposite side of the thermal then tighten up again. Learn to
control airspeed by sound and use an audio vario so you can keep your eyes
on the other glider.

Reducing bank angle from 45 deg to 30 degree will double your turn diameter.
If you resume a 45 degree bank after 180 degrees of turn, you will have
moved the circle center one diameter toward the stronger lift. This gentle
correction will let you keep the other glider in sight.

He should follow your move to stay opposite.

The way I was taught and I am now teaching my students for moving your circle
in a given dicrection is rather to revert to zero bank angle when your heading
is just the direction to which you want to move the circle, keeping wings
level the amount of time suited to the intended move and then resuming circling
at the previous bank angle.

Your method of reducing bank angle for half a turn assumes you start that a
quarter turn (90 degrees) before your heading is in the direction you want
to move. You are then in the worse part of your initial circle, maybe sinking.
If you needed 45 degree bank, that means that the thermal was narrow. Lowering
the bank angle at the worse part of the thermal will make most of the part of this
manoeuver in the worse part of the thermal or outside of it.

Anyway the main problem is to have the other glider follow your move. Regarding
this, this is also a pro for the method above, at least in my country, as
everybody having learnt here should have learnt in the same way and so the intent
should be obvious. However going straight ahead maybe misiniterpreted at the
begining of the manoeuver as leaving the thermal, although the dive associated
with this last thing is missing. If the other glider is known to have a radio on
the same frequency, using it may help.

"Bill Daniels" wrote in message news:
Reducing bank angle from 45 deg to 30 degree will double your turn diameter.

Not a big deal and I did it wrong the first time, so won't vouch for
this one either, but think the diameter increases by 73%, not 100%.
The pertinent equations seem to be

Fh = m v^2/r

where Fh is the horizontal component of lift

and

Fh/mg = tan(theta)

where theta is the angle of bank, yielding

r = v^2 / [g * tan(theta)]

so

r(30) / r(45) = tan(45) / tan(30) = 1.73...

Any corrections are welcome.

Martin

"Bill Daniels" wrote in message news:
Reducing bank angle from 45 deg to 30 degree will double your turn diameter.

Not a big deal and I did it wrong the first time, so won't vouch for
this one either, but think the diameter increases by 73%, not 100%.
The pertinent equations seem to be

Fh = m v^2/r

where Fh is the horizontal component of lift

and

Fh/mg = tan(theta)

where theta is the angle of bank, yielding

r = v^2 / [g * tan(theta)]

so

r(30) / r(45) = tan(45) / tan(30) = 1.73...

Any corrections are welcome.

Martin

(Hal) wrote in message . com...
Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift? I seem to have the biggest problem at the top of the thermal
when the other glider has flattened out the bank angle and seems to
stay in better lift.

He may just have a lower sink rate than you. Differences is glider
sink rate are insignificant when both gliders are racked up tight in a
strong core, but they are very significant when trying to milk the
last 100ft out of a thermal.

If the gliders don't have different performance, and you are being
outclimbed, then go where his is and do what he is doing. It does
require all the pilots in the thermal to be aware of each other and to
continuously adapt. Keep everyone in your scan and position yourself
where you can be seen by everybody else.

Don't fixate so much on the one other glider that you miss the other 3
that are joining you, or the other one that is half a mile away
climbing far better than both of you.


Andy

Hel,

Great question. Let me give you the simple answer. If you are opposite
(180) a glider and it's climbing better, steepen your bank through 90
degrees of turn, then shallow out for several seconds to shift your
circle to the side of the thermal where you saw the better lift.

Let me take you around the points of the compass.

You see better lift on the south side of the circle. Your are on the
north side (facing West - turning left) Steepen up (60 degress)
through 90 degrees of turn, until you are facing south, then shallow
(not level - about 20 degrees) for a count of three. If you feel a
surge, stick with it for as long as you dare. In either case, you next
adjustment should be to steepen you turn to 60 degrees again. Stay
steep for one full turn, noting differences around the circle, then
adjust accordingly to center on the core at about 40 degrees of bank.
Be sure to watch out for your marker. If he didn't see your
adjustment, you will probably conflict with him as you come around
facing west.

Top of the thermal... lift gets much more difficult to center at the
top of a thermal. I can't offer much help here.

Cheers,

OC


(Hal) wrote in message . com...
Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift? I seem to have the biggest problem at the top of the thermal
when the other glider has flattened out the bank angle and seems to
stay in better lift.

How do you guys figure all this out? Count to 60 seconds, bank at 45,
then etc, etc, etc.

I watch the other glider. If he or she's doing better than me (almost
always), I try to proscribe the same path. If I'm the one doing
better,then I just keep on trying to do it. Mostly I follow my own
mediocre thermaling instincts while trying not to interfere with
others. Safety is always first, and I'll always avoid the too close
encounter or leave the thermal if things aren't working out.

Maybe it's just me, but when I overthink my flying, I never do as
well. Still learning, always...

Carl
Discus B, Warner Springs


(Chris OCallaghan) wrote in message . com...
Hel,

Great question. Let me give you the simple answer. If you are opposite
(180) a glider and it's climbing better, steepen your bank through 90
degrees of turn, then shallow out for several seconds to shift your
circle to the side of the thermal where you saw the better lift.

Let me take you around the points of the compass.

You see better lift on the south side of the circle. Your are on the
north side (facing West - turning left) Steepen up (60 degress)
through 90 degrees of turn, until you are facing south, then shallow
(not level - about 20 degrees) for a count of three. If you feel a
surge, stick with it for as long as you dare. In either case, you next
adjustment should be to steepen you turn to 60 degrees again. Stay
steep for one full turn, noting differences around the circle, then
adjust accordingly to center on the core at about 40 degrees of bank.
Be sure to watch out for your marker. If he didn't see your
adjustment, you will probably conflict with him as you come around
facing west.

Top of the thermal... lift gets much more difficult to center at the
top of a thermal. I can't offer much help here.

Cheers,

OC


(Hal) wrote in message . com...
Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift? I seem to have the biggest problem at the top of the thermal
when the other glider has flattened out the bank angle and seems to
stay in better lift.

In practice the increase could be even less than 73%
because 'v' is not constant, you can thermal slower
with a lesser bank angle.

At 02:24 14 October 2004, Martin Hellman wrote:
'Bill Daniels' wrote in message news:
Reducing bank angle from 45 deg to 30 degree will
double your turn diameter.

Not a big deal and I did it wrong the first time,
so won't vouch for
this one either, but think the diameter increases by
73%, not 100%.
The pertinent equations seem to be

Fh = m v^2/r

where Fh is the horizontal component of lift

and

Fh/mg = tan(theta)

where theta is the angle of bank, yielding

r = v^2 / [g * tan(theta)]

so

r(30) / r(45) = tan(45) / tan(30) = 1.73...

Any corrections are welcome.

Martin

At 14:36 14 October 2004, Todd Pattist wrote:
(Chris OCallaghan) wrote:

If you are opposite
(180) a glider and it's climbing better, steepen your
bank through 90
degrees of turn, then shallow out for several seconds
to shift your
circle to the side of the thermal where you saw the
better lift.

I wouldn't do this.

When I'm sharing a thermal with another glider at the
same
altitude I'm trying to figure out two things - 1) 'where
is
the best lift?' and 2) 'what is the other glider going
to
do?' The first question is answered by watching the
other
glider's relative climb rate. The second is usually
signaled by the changes he makes in bank angle.

I have to recognize that the other pilot may not agree
with
me where the lift is strongest. I also keep in mind
that
he's trying to answer the same two questions I'm trying
to
answer, so my actions signal to him my intentions,
just as
his actions signal his to me. The first pilot to
adjust
his bank is signaling where he wants to move the center.

I think it works better for each glider to flatten
towards
the core to move the center. I'm not against tightening
in
the core, a bit, but that method should be used with
more
caution as it tends to put the gliders closer. I'm
against
tightening in the sink first, then flattening as it's
likely
to confuse the other pilot and delay the cooperative
process
of moving to the center of the lift.

If I see a pilot steepen in sink, I'm immediately concerned
he thinks the lift is stronger there. However, if
he waits
90 and flattens on the heading towards the core, I'm
reassured that he's either leaving and not a problem,
or
more likely, he agrees with my conclusion on where
the core
is.



If a pilot is alone and thinks he's found the core,
he'll
typically steepen his bank. It keeps him turning in
the
core and it moves the center of the circle closer to
the
core before the pilot opens up a bit. If he doesn't
steepen
in the core, but recognizes the sink side first he'll
typically open up the bank first and fly towards the
core.
Thus, with two pilots in the same circle negotiating
as to
where to move the core, it's the first to change his
bank
that signals where he thinks the core is.

If I'm coming into the strong core, I desperately want
to
tighten, so I'm closely watching the glider on the
weak
side. If I see the pilot steepen there, I'm immediately
concerned he thinks the lift is stronger there. However,
if
he waits 90 and flattens on the heading towards the
core,
I'm reassured that he's either leaving and not a problem,
or
more likely, he agrees with my conclusion on where
the core
is, and I'll expect him to tighten as he reaches the
core.

Bottom line,
Todd Pattist - 'WH' Ventus C

Let's hope you two guys don't meet up in the same thermal!
I believe we have the makings here of a two-party
system on thermalling. Let's hope it doesn't get vicious.

Some of us don't even have a theory; we just blunder
around.