W ind  Wind Figure 10-24.  One technique for catching a thermal from ridge lift. Figure 10-26.  Analyze sloping ground for collectors and dividers  of wind. Figure 10-25.  Catching a thermal by flying upwind away from  the slope lift. Tips and Techniques Observe the ridges slope for collectors or dividers of the wind  flow. Plan to determine which of the slopes is gathering wind  flow.  [Figure 10-26]  Due to the changes in wind directions  and or sun angles, any portion on the ridge can change in  only a few minutes. The downwind side of any ridge or hill produces turbulence  and sink. The larger or higher the ridge and the greater the  wind velocity, the wider the turbulence may be. During  these conditions, remember to ensure that seat and shoulder  harnesses are tight. Sink calls for speed. Turbulence and  speed are very hard on the glider airframe and pilot comfort.  Pilots must obey glider limitations set forth in the GFM/ POH. Also, do not exceed the design speed for maximum  gust intensity (V$_{b}$ ).  [Figure 10-27] The ridge crest is where all airflow starts down. Steep ridges  with narrow ridge tops can collect thermal action from both  sides of the crest. The best lift could be directly above the  crest. However, this terrain can be very hazardous as a pilot  cannot see it or may not have visual cues. If wind is the only  source of lift, the crest can be very dangerous. Always stay  upwind of the crest.  [Figure 10-28] Areas along the ridge that are in deep shade is where the air  goes down and sink can be found. If there is strong lift on  the sunny side of the ridge, then chances are that strong sink  be able to provide useful information on any problems with  the local ridge. •  Collectors are mountain/ridge bowls and canyon ends  that can offer extreme areas of lift when the wind is  blowing into them. Remember to have a way out. •  Dividers are ridges parallel with the wind and tend  to have airflow separation. A collector that may be  downwind from a divider may receive more airflow,  making better lift possible. 10-15