Accelerometer
    All of us come equipped with remarkably sensitive accelerometers which are perfect for thermaling once we recognise both their power and limitations. We can sense very small accelerations but feel nothing once the acceleration ceases and we are moving at a constant velocity. Our experience in our cars or in a lift shows us this. We feel the initial acceleration but while travelling at constant velocity we feel nothing until we feel the deceleration as we slow down. Our accelerometer is excellent for thermaling.

    Our second key ability is our power of visualisation. Just as we can build up a mental picture of a dark room by wandering around bumping into the furniture we can build a similar picture of the invisible currents of air by flying around and bumping into them.

    Here's how its done. Consider our pilot again. The instant he enters the thermal he senses the acceleration. The instant he hits the core he uses all his senses to note the strong surge of lift causing a strong acceleration which combines with a tendency for the gliders nose to pitch up to signal to his brain CORE! The one second processing lag means he is still in the core when the message arrives. Two seconds later he exits the core which he notes as a deceleration (like falling) and the nose of the glider pitching down. One second for processing lag and he initiates his turn. Two seconds later after response lag the glider turns, but this time is still in the thermal.

    OK so far so good but we are still going to be plagued by the dual problems of processor and glider response lag. Here is where visualisation takes over. The pilot now constructs a mental picture of the thermal, where he is in it, where he is going, and finally what he needs to do to centre his circle on the core. With each circle more information is added to this mental map until coring becomes as easy as driving round a round about. In simple terms say you are flying south when you feel yourself fall out of the core. OK you think the core is nore to the north so after a 180 you flatten out your turn for a couple of seconds then resume your circle, you are now circling further to the north and should be closer to the core.

    Now we come to refinements. The first improvement is this. Pilot hits core and processes it 1 second later. Knowing that the glider response will lag 2 seconds he initiates an immediate turn - presto he is turning in the core, admittedly perhaps not yet centred but still streets ahead.

    The second improvement is to recognise the glider as the extension of your body that it really is. Just as you can feel if I come up and push you so you can feel if a thermal pushes your glider. But how do you tell if a wing is being lifted and differentiate this from a wing which is sinking on the other side, after all they will both result in a roll in the same direction? Lift will be associated with an upward acceleration, cause the gliders nose to pitch up, and if off to one side cause a wing to rise. Sink or less lift (relative sink) will be associated with a downwards acceleration (falling feeling), the gliders nose pitching down, and if off to one side a cause a wing to drop. The bottom line is that differentiating wing lift or drop doesn't actually make that much difference. Why?

    Because in either case the glider is heading AWAY from where you want it to go! Be your own boss. Don't let yourself be sucked into sink and spat out of lift.

    The next refinement is speed control. Linger in lift, speed through sink. This goes for thermals to. Sometimes the core may be too small to circle in. Sometimes the air is so bubbly there are no long lasting cores. We can maximise the time spent in the lift by slowing down as much as possible as soon as we sense lift. Our gliders make this easy for us as the nose pitches up automatically. Don't fight it relax and let it, depending on your speed and altitude (not at 50' please) slow some more. Stall? Oh well slow a little less next time. You will be surprised just how far you can push the bar out when banked up in a strong core. Make sure you have enough height to recover from an unintentional stall before experimenting.

    So what is the role of the vario. Well once we are centred it will happily chirp a continuous tone which is good because now we will get limited feedback from other sources. It also remind us we are not centred by showing oscillating lift strength.

    There is no substitute for practice and the best way to see how you're going is to go to competitions. You don't need a high performance glider to have fun. I flew 185km (~115miles) in a Moyes XT intermediate glider in my first comp. Ask questions. Read all you can. Buy a copy of Cross Country Soaring by the late sailplane world champion Helmet Reichmann from Amazon.com or the Soaring Society of America - it covers all of this plus speed to fly in great detail. Check out this web site, it contains classic papers on soaring.