rodbailey

When to leave a thermal?
by Kelly Farina ( http://www.austrianarena.com )
Recently was discussing some interesting techniques with Adrian Thomas(long time British Team member), mostly about when does it become necessary to push on to the next thermal if you want to fly fast. It opened my eyes to what other pilots are doing when racing.

In the past I�ve always tried to work out an average for the time of day and if there is a good visible clue to lift closeby when the thermal averager dropped below this I�d move on. I often say to myself “ok, if this drops to below 2m/s average I�ll crack on”, but this has nothing to do with what the climb has been and only if I�m in a good position for finding lift on the next glide. A little too conservative really if you want to crack on and push average speeds.

This works but can be a little too theoretical due to conditions and terrain ahead. If there are inversions and a long valley crossing where arriving high is crucial it�s important to milk the climb as much as possible, as is the case if it�s completely blue out front. The following theory relies on the fact that you know where the next climb is likely to be, either there is a huge cloud forming, birds circling or other glides climbing.

Adrian�s theory also relies on the assumption that if you enter a thermal low down it could be weak, then it normally gets stronger with altitude and then once it loses it�s strength will start to drop off again. So the idea would be to once you are established in a thermal low down you should check you average climb(set it to 30seconds), maybe 1.5m/s. As the climbs strengthens remember this figure as if the climb starts to drop and you have altitude enough to push on that would be the most theoretically efficient time to go, assuming you see your next climb. Then repeat this process along the route.

I�ve been working with my own way of pushing on in weaker lift but it�s different to Adrian�s way of thinking. I�m going to experiement the next chances I get and will report on the results whilst� flying with my friends whilst flying around the Zillertal tour or up to the Ahorn Spitz.

One other thing to note also is that if the climb doesn�t drop off from entering to base then leaving whenever you have enough to cross next obstacle should be the way to go. This is more like alpine flying with strong climbs from source to base. Perhaps this is more for flatland flying or especially places like Piedrahita, where I had a terrible time. Mainly because I was pushing on too hard, failing to top up in extremely weak climbs and not mincing around a base. Some of the tasks were flown at extremely slow speeds, one task was 18kmh for the winner around 107km, slooooooow. Austrian Open task 2 97km, average speed 44kmh for winner. Very different types of flying and I gotta say my slow mincing style needs some work!!

When I have some results I�ll post them on this site.

Thanks for reading and hope that you get to experiment with this too with your mates.

KF