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Another technique involves simply timing the altitude gained over 30 seconds or 1 minute. 

Theoretically, the optimum average speed is attained if the MacCready ring is set for the achieved rate of climb within the height band. To do this, rotate the ring so that the index mark is at the achieved rate of climb (for instance, 400 fpm) rather than at zero (the setting used for maximum distance). A series of climbs and glides gives the optimum balance between spending time climbing and gliding. The logic is that, on stronger days, the extra altitude lost by flying faster between thermals is more than made up in the strong lift during climbs. Flying slower than the MacCready setting does not make the best use of available climbs. Flying faster than the MacCready setting uses too much altitude between thermals; it then takes more than the optimum amount of time to regain the altitude. 

Strict use of the MacCready ring assumes that the next thermal is at least as strong as that set on the ring and can be reached with the available altitude. Efforts to fly faster must be tempered with judgment when conditions are not ideal. Factors that may require departure from the MacCready ring theory include terrain (extra height needed ahead to clear a ridge), distance to the next landable spot, or deteriorating soaring conditions ahead. If the next thermal appears to be out of reach before dropping below the height band, either climb higher, glide more slowly, or both. 

To illustrate the use of speed-to-fly theory, assume there are four gliders at the same height. Ahead are three weak cumulus 

clouds, each produced by 200-fpm thermals, then a larger cumulus with 600 fpm thermals under it, as in Figure 11-13. 

• Pilot 1 sets the ring to 6 knots for the anticipated strong climb under the large cumulus, but the aggressive approach has the glider on the ground before reaching the cloud. 

• Pilot 2 sets the ring for 2 knots and climbs under each cloud until resetting the ring to 6 knots after climbing under the third weak cumulus, in accordance with strict speed-to-fly theory. 

• Pilot 3 is conservative and sets the ring to zero for the maximum glide. 

• Pilot 4 calculates the altitude needed to glide to the large cumulus using an intermediate setting of 3 knots, and finds the glider can glide to the cloud and still be within the height band. 

By the time pilot 4 has climbed under the large cumulus, the pilot is well ahead of the other two pilots and is relaying retrieve instructions for pilot 1. This example illustrates the science and art of faster cross-country soaring. The science is provided by speed-to-fly theory, while the art involves interpreting and modifying the theory for the actual conditions. Knowledge of speed-to-fly theory is important as a foundation. How to apply the art of cross-country soaring stems from practice and experience. 

## Tips and Techniques 

The height band changes during the day. On a typical soaring day, thermal height and strength often increases rapidly 

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