For the new glider pilots, it is best to become proficient using  one of the above methods first, and then experiment with  other methods. As an additional note, thermals often deviate  markedly from the conceptual model of concentric gradients  of lift increasing evenly toward the center. For instance, it  sometimes feels as if two (or more) nearby thermal centers  exist, making centering difficult. Glider pilots must be willing  to constantly adjust, and recenter the thermal to maintain the  best climb. In addition to helping pilots locate lift, other gliders can help  pilots center a thermal as well. If a nearby glider seems to be  climbing better, adjust the turn to fly within the same circle.  Similarly, if a bird is soaring close by, it is usually worth  turning toward the soaring bird. Along with the thrill of  soaring with a hawk or eagle, it usually leads to a better climb. Collision avoidance is of primary importance when  thermaling with other gliders. The first rule calls for all gliders  in a particular thermal to circle in the same direction. The  first glider in a thermal establishes the direction of turn and  all other gliders joining the thermal should turn in the same  direction. Ideally, two gliders in a thermal at the same height  or nearly so should position themselves across from each  other so they can maintain best visual contact.  [Figure 10-12] When entering a thermal, strive to do so in a way that does  not interfere with gliders already in the thermal, and above  all, in a manner that does not cause a hazard to other gliders.  An example of a dangerous entry is pulling up to bleed off  excess speed in the middle of a crowded thermal. A far safer  technique is to bleed off speed before reaching the thermal  and joining the thermal at a “normal” thermaling speed.  Collision avoidance, not optimum aerodynamic efficiency, is  the priority when thermaling with other gliders. Announcing  to the other glider(s) on the radio that you are entering the  thermal enhances collision avoidance.  [Figure 10-12] air collisions can sometimes be survived, but only with a  great deal of luck. Unsafe thermaling practices endanger  everyone.  [Figure 10-13] Different types of gliders in the same thermal may have  different minimum sink speeds, and it may be difficult to  remain directly across from another glider in a thermal.  Avoid a situation where the other glider cannot be seen or  the other glider cannot see you. Radio communication is  helpful. Too much talking clogs the frequency, and may make  it impossible for a pilot to broadcast an important message.  Do not fly directly above or below another glider in a thermal  since differences in performance, or even minor changes in  speed can lead to larger than expected altitude changes. If  sight of another glider is lost in a thermal and position cannot  be established via a radio call, leave the thermal. After 10 or  20 seconds, come back around to rejoin the thermal, hopefully  with better traffic positioning. It cannot be stressed enough  that collision avoidance when thermaling is a priority! Mid- Leaving a thermal properly can also save some altitude. While  circling, scan the full 360° of sky with each thermaling turn.  This first allows the pilot to continually check for other traffic  in the vicinity. Second, it helps the pilot analyze the sky in all  directions to decide where to go for the next climb. It is better  to decide where to go next while still in lift rather than losing  altitude in sink after leaving a thermal. Exactly when to leave  depends on the goals for the climb—whether the desire is to  maximize altitude for a long glide or leave when lift weakens  in order to maximize time on a cross-country flight. In either  case, be ready to increase speed to penetrate the sink often  found on the edge of the thermal, and leave the thermal in a  manner that does not hinder or endanger other gliders. 10-9 Exiting a Thermal Figure 10-12.  Proper positioning with two gliders at the same  altitude. Numbers represent each glider’s position at that time. Collision Avoidance  A B 1 2 3 4 5 1 2 3 4 5