[LASS Soaring] Read this, you might find it helps, themal hunting article

[GordySoar at aol.com]

Thermal Tips  
by Mark Howard 
 
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When someone asks to fly one of my sailplanes, I am always flattered. I 
want the  experience to be a positive one, as I pride myself on the performance 
of my  ships. Often, however, others experience difficulty controlling my 
planes,  particularly pitch - usually in unstable air. I believe this is 
caused by a  marginally stable setup on the plane and over-correction by the 
pilot. A rock  stable setup is very easy to fly - but is just no good for 
signalling lift. An  unstable setup is great for signaling lift - provided that 
the pilot flys with  "kid gloves". A marginally stable setup is an excellent 
compromise for most  advanced pilots. Such a setup signals lift quickly, but 
inattention can put the  plane in an uncomfortable attitude very quickly.  
I am a believer in the CG dive test, but I never set the CG so far back as 
to  preclude a slow but positive dive recovery. Such a setup will tend to 
pitch the  nose up when flying into lift, and nose down when leaving lift. A 
sharp turn on  thermal entry may result in a dramatic loss of altitude after 
an initial rise.  The instinctive reaction on entering a thermal is to 
immediately roll into a  turn and pull back stick which may be the wrong thing to 
do. This  over-anticipation usually results in a turn away from the core of 
the thermal -  into the sink. It also makes reading the thermals' size and 
strength difficult.  It is better to wait until the rate of climb just 
starts to decrease - or even  until slight sink is encountered before initiating 
any turns. The thermals' size  and strength become more obvious. After 
turning back into the general vicinity  of the lift, establish a circular 
pattern. Adjust the circle towards the "high"  side and away from the "sinky" side. 
When the plane is rising, and there is no  "high" or "low" side - then the 
circle is centered around the core. If the lift  is strong with a small 
core, a steeper bank and smaller turning radius is  necessary. Weaker thermals 
require a flatter turn. Experiment to find the  flattest turn which results 
in a similar rate of climb.  
Sometimes the core is "where it's at". You must work these thermals tight 
and  adjust quickly, or risk losing the thermal entirely. These are the kind 
of  themals that "spit out" hand launch gliders. They sometimes do the same 
to  unlimiteds. Use camber to slow the stall speed , and try using more 
rudder to  hold the turn. If the nose pitches up wildly - PUSH a bit and flatten 
the turn  to prevent a "wingover". If a pitch cycle results in a dive, use 
the energy to  advanatge: let the speed carry you back farther into the 
sweet spot. The air  close to the core is the most turbulent - and flying 
smoothly in the core is  much harder than on the core perimiter - and smooth is 
what it's all about.  Thermals tend to spread out as they rise. Flying the 
perimeter makes it easier  to gage subtle shifts in the thermals' direction.  
New pilots often can't tell the difference between a workable thermal and a 
 teaser. A teaser thermal is one that is not of sufficient diameter AND 
strength  to work within the performance envelope of the sailplane. I've seen 
pilots work  these "thermals" losing several hundred feet until it is rather 
obvious that  they are not going up. DA! Remember, if you're not going up - 
LEAVE. Put your  plane on a straight course towards greener pastures and 
watch! Now is a good  time to think as well! Feel the temperature. A rise in 
temperature means lift is  nearby. A drop means nearby air is sinky. If the 
wind has calmed and the  temperature is rising, there is probably lift to be 
found in the upwind  direction of what was the prevailing wind. If the wind 
is suddenly stronger,  then there's probably a thermal blowing thru - and the 
lift is downwind. Try to  approach thermals from the downwind direction. 
For some reason, you'll encounter  less sink approaching from downwind rather 
than upwind - the sink band seems to  be narrower and weaker. If you are 
flying upwind, and feel a thermal push thru,  think twice before chasing 
downwind to catch it. You may lose all your altitude  in the effort. Surely, 
you'll have to fly through a good bit of sink to find it.  Use the information to 
your advantage. If you know a thermal just pushed thru -  and the cycle 
rate, you can predict the upwind run needed to catch the next  upwind thermal.  
Watch for debris in the air - dust, cobwebs, etc. Feeding birds are a sure  
sign - they swarm in thermals that contain bugs. Remember that a thermals' 
top  is almost always downwind of the bottom. Tune in to conditions: wind 
speed, wind  direction, and temperature. Try to visualize where the lift is - 
especially  before launch. When sport flying - make a conscious guess as to 
where lift can  be found. Fly over to that area and see if you were right. 
If you fly with your  thumbs, make a concerted effort to fly with the 
index-finger/thumb method. When  I first started flying f3b, I realized that this 
method provides much more fine  control. It also improves smoothness. 
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