Bruce Abell has submitted and article he wrote on thermals. This is a good introduction to the subject but if you think that you will meet the classic thermal described in his article very often you will be sadly mistaken. I recently read an article based on radar imaging of thermals which confirms Bruce's description of the classic vortex view of thermal structures but these observations were made at a height greater than where we model flyers first contact thermals. At ground level to 400 feet the picture is less clear. His experience of getting better results turning one way rather than the other also parallels my experiences in full sized and model gliders, it is always worth trying to reverse the turn to see if you get better results - so long as you don't loose the lift altogether!
The "green air" that Bruce refers to is a reference to the old Cosim variometer (tells you when you are going up and down) The Cosim had two verical tubes, the one showing that the glider was climbing had a greeen plastic pellet, the sink tube pellet colour was red!
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