1. Speed to Fly and Thermals

2. Wing Polar

3. Compare two Wings

4. Travel Speed for downwind XC

5. South Africa Thermals
Highest temperature can be expected between and in a day. Means thermals are highest late in the afternoon
 Thermals start off in the day narrow and strong and become wide and weak in the late afternoon

6. Chance of finding a Thermal
Thermal probability
1.5 km
8 km
15 km
0.5 m/s
20%
90%
99%
1.0 m/s
10%
60%
84%
2.0 m/s 5%
30%
52%
3.0  m/s 2%
18%
Thermal probability
1.5 km
8 km
15 km
0.5 m/s
20%
90%
99%
1.0 m/s
10%
60%
84%
2.0 m/s 5%
30%
52%
3.0  m/s 2%
18%

7. Distance to next Thermal
Rule of thumb is that one needs 2.5 times the height of a thermal to find another one.
For Dunnottar, low cloudbase days work best.
700 meters and a glide ratio of 6-7 = 4-5 km
700 meters x 2.5 = 1.8 km to the next thermal 1500 meters x 2.5 = 3.8 km, just possible
3000 meters x 2.5 = 7.5 km, fly Welkom

8. Where to find the lift under a cloud
 On a weak wind day on the sunny side
Or up wind and towards the sun.
For Gauteng area, wind is predominant NW. Sun in the afternoon is shining from the NW, so look for the lift in the NW corner of a cloud

9. That’s all for today
Mort recommends that you got your recovery organized
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