by Ed Anderson
aeajr on the forums
A thermal is a column of warm rising air that occurs when one section of
the ground warms faster then other sections. As the air raises it draws in
more air. Think of a very slow moving tornado. Not exactly correct but
close enough for first approximation.
TIPS ON FINDING THERMALS
The best conditions are calm air, hot sun and low humidity. Some big dark
areas surrounded by lighter areas will help to create thermals, so look to
see if there is anything like that on or around your field. A freshly
plowed field is good. A parking lot works great! A large building
with a black roof is awesome.
However I have caught thermals at 35 degrees F in 15 mph winds. They can be
weak and they move fast, but the are there!
What do thermals look like?
Here are some thoughts on the hunt!
LISTEN WITH YOUR EYES
Get your plane up high, the higher the better. A long hi-start can get you
400-600 feet up which will give you several minutes of glide if you don't
find any lift.
If you have a motor, cut the motor and trim the plane for nice level flight.
Now, focus on watching the plane and keeping it on a nice steady glide.
Steady as she goes. Try to keep your hands off the sticks as much as
Let the plane ride with and across the river of air, giving it only
occasional input to keep it going in the general direction you want to go,
but don't be a stickler about it. Let it drift like a fly on the surface of
the river, waiting for a trout.
If you listen with your eyes, it will speak to you, but you have to listen
Glide across the wind, not directly into it and not with it as it can be
hard to see what the plane is doing when it is going directly away from
you or coming directly at you. Sort of a 45 -60 degree angle left for a
while then a 45 to 60 degrees to the right. Nice and slow and easy.
You want to cover the sky and search the moving river of air, like a
bird looking for food.
As you are flying, watch the wing tips the nose and the tail. If a wing
seems to bump up, or if the plane seems to become buoyant, floating up for a
moment, it could be a gust, or you might have just brushed a thermal. Go
gently into a slow turn in the direction of the wing that rose. Thermals
will try to push you away. If you see the nose come up for a little while,
then drop a few seconds later, you may have gone right through the middle
of the thermal. Turn gently to circle back into it. It will be moving with
the wind, so
don't try to keep the plane in one place in relation to the ground. As you
thermals it is natural for your plane to travel down wind as you circle.
Try to make a circle, but not too tight or you will lose too much altitude.
Try for about a 100 foot diameter at first. Complete a couple of turns
and see if the plane seems to be rising at some point in the circle. If it
is, just stay with the turn and try to find that area where it rose, the
focus the plane into that area. If you find the rising air you are trying
keep the plane in that air column. If it is rising you can apply a little up
elevator in your turns, but not much. You don't want to stall and you don't
want to scare the thermal, you want to bond with it.
Try to observe if the plane is rising steadily, or if it seems to rise and
fall. That could mean you are not centered in the thermal, so work your way
more toward the side of the circle where the plane rises.
Remember that thermals move with the wind, so you are not trying to stay in
one place in relation to the ground. The air is like a river and you are
trying to stay in a little whirlpool that is moving with the river.
If you go into the turn and make a couple of turns with no success, then
just resume the search pattern I mentioned. Angles across the wind. Not
into it and not with it.
A sailplane in lift - This is an AVA 3 M sailplane
notice he is hunting, then he hits!
As you watch the video, notice the light poles and how the plane tends to
drift from right to left. He is circling more than usual as he feels he has
lift in the area and is trying to find the center. That is the direction of
the wind. Using the
tops of the trees as reference you can see that he is rising.
If you are getting out too far, work your way back the same way, angles to
the wind. Remember it will take longer to go up wind than down wind and
you will be losing altitude all the time, if you don't find lift.
Finding elusive thermals
Unless you hit a boomer, you are not going to immediately know you are in
lift, so you have to watch the plane. Sometimes it becomes apparent because
you realize that your not sinking but appear to be holding altitude. The
only way to do that is to be in lift.
Remember also that thermal can vary in size and intensity. Some are fairly
narrow and some are so large that it seems a whole region of the sky is
in lift. I rode one area recently for 58 minutes where it seemed about 1/4
of the field was in lift. In this case, I didn't really have to circle. I
just flew back and forth and the plane rose beautifully. Those are really
nice, when you find them.
If you are flying an electric glider, or even an electric parkflyer, if you get down
below 100 feet or so, it can become hard to catch a thermal so power back up
to 400-500 feet and begin the hunt again, working new areas of the sky.
It is a hunter's game, if you are up for it.
Good luck pilot! May your hunt go well!
Welcome to the Novice Lounge - A resource for new thermaling nuts!