Thermaling  


Entering The Thermal

After feeling a bump up, verified by 4 seconds of up vario, turn toward uplifted wing. If two bump ups are felt, turn toward uplifted wing on second bump, which may be different direction from the first bump. If lift is smooth and gentle – gently roll into 30 degree bank turn. If lift is strong and turbulent – briskly roll into turn of probably more than 30 degree bank. After turning about 90 degrees, check vario.  If vario moves to sink, you probably turned away from lift.

Continue same direction of turn to just short of 270 degrees.  Then roll out and fly straight for 3 seconds.  Now continue same direction turn, even if at first no lift is encountered. During each circle determine which side of circle has best lift.  Shallow the bank a little before reaching best lift in order to move further into the thermal. If sink is encountered (vario show minus), quickly steepen bank ( at least 45 degrees) for about 180 degrees of turn, then shallow (15 degrees – 20 degrees) bank until vario improves, then back to normal 30 degree bank.

Staying In Thermal

The Thermal want to spit you out! Do not let bank change. If turbulence rocks wings (and it will) immediately correct bank (possibly over correct) to keep the same shape circle. Do not let bank change.

If you let yourself get knocked out of a thermal, you will move into sink! If you get “spit out,” use steep bank to move away from sink, then shallow (15 degree – 20 degree) bank until vario improves (1 – 2 seconds) then back to 30 degree bank. Remember:  shallow bank in improving lift, steeper bank in sink.

You know you are centered when vario shows equal lift around the turn.

Centering Thermal Core

When trying to center on improved lift, start with shallow bank.  Do not increase to normal bank until you feel a surge on the inboard wing (the inboard wing rises.)  Then increase bank to 30 degrees or greater. This works well on non-round thermals found in mountains. Glider is in strong core if aileron pressure is needed toward direction of turn to stay centered.

References:

            Bob Wander -                     “The Art of Thermaling”
            Derek Piggott -                    “Gliding” 
           
Helmut Reichmann -             “Cross Country Gliding”