Sharing a thermal

"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