ORIGINAL: Slo-V Flyer
And yes I was hoping to do some "thermaling" whenever I figure that out.
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.
What do thermals look like?
http://www.flyaboveall.com/mountainp...rmalclinic.htm
If you have an electric plane and your ESC has a brake, set the break to
work. This will stop the prop from spinning. When you are gliding, a
spinning prop is like dragging an anchor. It really increases the drag.
Almost any plane can thermal, but the lighter the wing loading the better.
Under 12 ounces/sq ft is really good and under 8 is great! The typical
small electric plane has wing loadings in this area so they often thermal
well.
Flat bottom or under cambered wings tend to do better than symmetrical or
semi-symmetrical wings but if the lift is strong, you can thermal anything.
In fact we sometimes have to pull out of thermals because the lift is so
strong that the plane can be pulled into the sky and out of sight. I have
seen it happen.
For some people this may sound boring, but I relate it to fishing. You may
cast out many times with no bites. Still, the process is relaxing and
pleasurable. Then, you get a nibble and the fun begins. Where is he?
Finally you get a strike and the fight begins.
You go on each fishing trip looking forward to the catch, but knowing that
you will enjoy the process even if you come home with nothing. To
nonfishermen this sounds odd. They just don't understand. Likewise with
thermaling.
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!
Here are some thoughts on the hunt!
Get your plane up high, the higher the better. Get it well up wind from you
as we are going to glide and drift with the river of air.
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
possible.
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
patiently.
Glide across the wind, not into it and not with it. Sort of a 45 -60 degree
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 immediately
into a slow turn in the direction of the wing that rose. If you think you
went
right through it, fly on for a moment then turn to circle back into it. It
will be moving toward you.
Try to make a circle, but not too tight or you will lose too much altitude.
Try for about a 75-100 foot diameter at first. Complete a couple of turns
and see if the plane seems to be rising. If it is, just stay with the turn
but give it a little up (back) stick. Not a lot, just a little. Maybe two
to four clicks on the up trim. Just a little. We don't want to scare the
thermal, we want to bond with it.
Try to observe if the plane is rising steadily, or if it seems to rise and
fall that means 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 now with it.
A sailplane in lift
[url]http://www.rcgroups.com/articles/liftzonemag/2004/mar/ava/Ava2.wmv[/url
]
If you are getting out too far, work your way back the same way, angles to
the wind.
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 45 minutes where it seemed about 1/4 of
the field was in lift. You didn't really have to circle. You could just fly
back and forth and the plane would rise beautifully. Those are really nice,
when you find them.
It is a hunter's game, if you are up for it.
Good luck pilot! May your hunt go well!
Resources
Get the Old Buzzard's Soaring Book (A11560) Thornburg from:
http://www.carstens-publications.com/
What do Thermals Look Like
http://kohlin.com/air/soar-faq.htm#589882
http://www.rc-soar.com/tech/thermals.htm
http://www.apogeerockets.com/educati...g_thermals.asp
Thermaling on a windy day
http://www.moneysmith.net/Soaring/soaring9.html#ref97
Video on thermaling
http://radiocarbonart.com/Pages/asecthermalmain.html
The Soaring Methods of Birds
http://www.apogeerockets.com/educati...ng_methods.asp
Search Patterns
[url]http://www.quicktechhobby.com/articles/thermal_surfing%20part%202.htm[/
url]