Thermal Surfing part 2


	Thermal Surfing (Part Two)

Picking the Perfect Search Pattern

Before launch it's a good idea to pre-plan an efficient flight path that gives you the most chance of finding a thermal. One of the most effective search patterns that we've found is the S-Turn flight path (see illustration). Get the highest launch possible, as more altitude will give you more time and distance to hunt, and plan on coming off the high start directly into the wind. Once off the chute, we recommend making a 30º turn to the left (or right) planning a course 30º from directly upwind. 1

THE S-TURN FLIGHT PATH

Start your successful thermal search with three simple maneuvers.

The reason you'll want to make this turn is that it's easier to see the sailplane from an angle than looking at it from directly behind. Since you'll have to depend on how the sailplane reacts to determine when it's in lift, the better you can see it, the more likely you'll recognize when a thermal is present.

You're going to let the sailplane fly on that 30º from-upwind course, hands-off with as few stick inputs as possible. It's important to very carefully watch the sailplane at all times and evaluate how fast it's falling or rising, and especially watch for small bounces, bumps or twitches. If the sailplane turns on its own, that's your sign that a thermal is likely near. Stay on this coarse and fly upwind until the sailplane begins to become uncomfortably far away. At this point, smoothly turn into the wind (if you're heading to the left, turn right) until you're flying perpendicular to the wind.2 Let the sailplane fly on it's own on this new course, again looking for tell-tale bounces, bumps, twitches or turns. You'll be looking at the side of the sailplane, so despite being far away, it's easy to see what it's doing. When the sailplane begins to become uncomfortably far away in this direction, make a smooth 180º upwind turn and fly back on that same course.3 Remember, thermals drift downwind and while you'll be covering the same ground, you'll be flying through new air. The key to finding a thermal is to probe as much new air a possible with each flight. Unless you find a thermal, you don't want to turn downwind because the air downwind is the air you've already tested and probed. You already know what this air is doing. You'll want to continue this upwind S-Turn pattern until you find a thermal or run out of altitude, in which case turn downwind and land.

Bounces Bumps Twitches Turns

Now that we have a good idea on how to hunt thermals, let's look at how to recognize and stay in them. During the search pattern, carefully watch your sailplane to see how fast it's sinking or rising, and look for bouncing, bumps, twitches or an unexpected turn. Thermals are a source of turbulent air and when your sailplane flys near one it's likely to be effected by this turbulence. Don't do anything just yet. Fly through the turbulent area until the sailplane settles back down then make a smooth turn back into the thermal. Start making a fairly large, 100 ft. diameter circle and watch to see if any part of the circle is in lift (the sailplane will actually rise or cease to fall). On subsequent circles scoot the circle in the direction of lift with rudder and elevator by oblonging the turn. Keep working the circle in the direction of lift, then tighten up the circle until the entire diameter is within the boundaries of lift.

CIRCLING INTO THE LEFT

Use increasingly elongated circles to hook into the thermal, then tighter circles to stay in it.

If you saw the signs, made your initial turn, and the first circle didn't show signs of lift, make the circle bigger and probe more area around the spot where you thought the thermal was. Be patient. It's there, you just have to find it. Continue circling, monitoring which parts of the circle are in lift and which are in sink and move the circle in the direction of the lift. Remember, thermals drift downwind so you need to let the sailplane drift with it if you're going to stay in lift.

Pretty soon you'll find a strong thermal that carries you thousands of feet in the air and very far down wind. It's important to bail out and head upwind before you get to high or too far downwind. Sink (downdrafts of air) are around thermals and usually one of the strongest areas of sink is just upwind of a thermal. You'll need to pass through this sink to get back up wind. It's a good idea to add several clicks of down trim to quickly penetrate this sink zone, plus the extra speed will get you up wind quicker with less altitude loss, so you'll be ready to find that next thermal.

One of our favorite things is to challenge one or more friends to a soar-off. Each pilot has his own high start and on the word go, everyone launches. The last one down wins. The key strategy is to carefully watch your competitors and if they find lift, immediately fly over to there thermal and thermal hop with them. I've been thermals with as many as 17 sailplanes at once. Talk about crowded! (But it sure is fun.)

Soaring: 10 Steps to Success

Trim your sailplane so that it flies perfectly straight "hands-off." Then, when hunting thermals, let the sailplane "do it's own thing" flying hands-off. This will allow you to see how the sailplane reacts to the air around it more accurately.
When hunting thermals, always fly in unexplored new air. Remember that air is constantly moving downwind. Always make turns upwind and remember the more new air you cover, the more likely you'll find a thermal. Unless a thermal is detected, making down wind turns and flying through the same air is unproductive. (Been their done that.)
Remember thermals drift with the wind and if you're going to stay with a thermal, you'll need to drift downwind too. Many beginners have a hard time staying with the thermal as it drifts. Just establish a bank angle and maintain a constant turn allowing your sailplane to go with the flow.
When in a thermal, carefully watch the sailplane throughout the circle. Notice which parts of the circle are in lift and what parts if any are in sink. Scoot the circle in the direction of lift (away from sink) on successive turns. This will give maxium altitude gain and help you stay with the thermal.
If you do lose the thermal, open up your circle and probe the air around where you thought it was. Likely it's still there, you just flew out of it. It's probably down wind from where you think it is!
When bailing out of a thermal to go upwind to find the next one, remember that there is normally sink just upwind of the thermal. You need to fly through this sink quickly or you may want to fly off to the side then fly upwind to avoid loosing excessive altitude. Flying downwind may be necessary to get back upwind without losing too much altitude.
Thermal activity varies tremendously from day to day and even throughout the day. When learning, pick a day that's calm and sunny. Mid-day is best as the most and strongest thermals occur when the sun is directly overhead. Thermals are easier to learn to find and use when there's lots of 'em!
Usually, but not always, thermals are larger in diameter the higher you go. Knowing this can be handy. If you're hunting thermals down low, you'll probably need to make tighter turns to stay in the lift zone. Up high you can open up the circles and be more efficient.
Many times you'll find yourself in a weak thermal without much altitude, struggling to stay aloft. You'll be tempted to bail out and look for better air, but if you do, 9 times out of 10 you'll be on the ground within minutes. Sink surrounds a thermal and leaving even a weak one has it's price. It pays to stick with what you've got and hope it gets stronger- lots of times it will.
If your new to sailplaning it may seem impossible that you'd find a thermal that takes your plane so high that it flies out of sight and is lost. But it can happen! Usually a pilot is so excited about catching good lift that he neglects to keep track of it's height. The next thing you know the sailplane is gone! Don't panic. Yell for everyone in the area to look skyward and smoothly apply full up and full right or left rudder. This will induce a gentle spin and the sailplane will descend. The spinning motion will make the sailplane easier to spot as the sun reflects off the covering.