Advanced Thermalling Part 1
Next week we will talk about centering and what I do to make the glider climb quickly.
This week we need to find thermals and consistently find them. There are some really good books out there that explain why a thermal rises in terrain. G Dale's book is one of my new favorites.
Start by studying the terrain, think about where the warm air source will be. What is going to heat better than the surrounding terrain? If I walked barefoot where is it going to be hotter? Where is the sun in relation to the slope? You can be as detailed as getting soil maps like the ones we used in Finland at the WGC. After a rain sand vs clay will make a difference.
What is the trigger for kicking off the envelope of warm air? Something has to break the warm bubble of air off the ground. At the SGP in Ionia the most reliable trigger I found was the windward side of lakes. A tree line on the downwind side of your source. A tractor working the field. I landed in a field in Slovakia at the JWGC and it kicked off a thermal allowing 2 guys to climb out (enter a string of expletives here).
Where is the thermal drifting? Remember the wind is not constant so the thermal may snake its way up as it drifts. That thermal being triggered from the lake edge might actually be found over the middle of the lake.
On days with clouds, I use the 50/50 rule. In the top 50% of the sky (sometimes working band) I spend more energy looking at the clouds. In the unfortunate event I get in the lower 50% I spend more energy looking at the terrain to find the next thermal.
At every thermal determine the source and trigger. You can then use that knowledge to find future thermals. Remember there are 'house thermals' everywhere.
When entering a thermal, you must stay relaxed, feel the glider. I have a tendency to turn into the wind if I cannot decide which way to turn, more on that next week.
Banner Photo: Jakub Swist
THE SOARING ENGINE series explains how the sun, wind, and terrain combine to produce rising air for the soaring pilot to exploit. In this volume, you will see how the wind flows over and around hills, ridges, and mountains, how thermals form and evolve, the patterns that ridge and thermal activity create in the air and how to use the lift produced both in flat terrain and in mountains. Illustrated with clear simple diagrams, this book is a primer for soaring pilots flying anything from a paraglider to high-performance sailplanes.
Garret Willat holds a flight instructor rating with over 8000 hours in sailplanes. His parents have owned Sky Sailing Inc. since 1979. He started instructing the day after his 18th birthday. Since then, Garret has represented the US Junior team in 2003 and 2005. He graduated from Embry-Riddle with a bachelor's degree in Professional Aeronautics. Garret represented the US Open Class team in 2008 and 2010 and the Club Class team in 2014. Garret has won 3 US National Championships.