Wind and Thermals?

[ammo]

Hi guys, i'm pretty new to sailplanes and stuff. after reading thru the threads in this forum, i've got some very good information on thermal hunting and stuff. However one thing that confuses me is,
we watch for wing dips and tips as hints for thermals but crosswind might do the same thing and turning into the wind might kill the momenteum of the plane, so can anyone kindly explain how i can differentiate between actual lift and wind. Advices are welcome too.
i'm flying a small electric glider but looking at the spirit elite soon.
http://www.okmodel.co.jp/shincyaku/saffron.htm

[RCFlybry]

If it's just wind you're not going to get any lift out of it where as you will on a thermal (assuming you're not on a slope). Two or three circuits in the questionable area will usually tell you whether it is or not. Also keep an eye not only on the wingtips, but also on the tail. When in lift the tail will often times kick up on you, pushing the nose down for a second or two. Sometimes the whole plane will suddenly come alive dancing wildly and then settle back down while coming out of the lift. If in doubt, do what I do.. Stick a wingtip on it and feel it out. If you're having trouble penetrating into the wind you might want to stick to calmer days with the particular sailplane that you're flying. The spirit elite would help in this situation.

Bryan

[T. Lyttle]

Thermal hunting on windy days remains an art form, and the aforementioned tips are fine, but practice is the real answer. Know your model! it will eventually tell you what air you are in, and remember every model reacts differently.

I watched some guys flying in a f/f contest, it must have been blowing 30mph, and about half (the experienced half) the guys were getting maxes. Any idea how far a model can travel in wind like that? Then they have to be back on the field for the next round. How did they fiind lift? Yup, practice...

[SoaringDragon]

One thing to keep in mind is that because you're sinking while the thermal is climbing, you'll tend to fall out of the back of them. Stretch out the upwind portion of your circles, and tighten the downwind portion when the wind is blowing.

[fprintf]

Wow is flying in a stiff breeze hard! It takes commitment to fly what looks like a thermal downwind at 25 mph. One thing that seems to happen is, if left alone in a trimmed circle, the the plane will stand on a wingtip at the upwind portion of the circle and lazily come around on the downwind portion. If I am understanding SoaringDragon correctly here, it takes active thumbs to smooth out the thermal circle rather than letting the plane do its thing.

Stuart

[schrederman]

I have to disagree with SoaringDragon on this one. The thermal moves with the airmass. Keeping the glider in it's circle moving with the airmass is exactly what Stuart describes as though it were a bad thing. It does indeed appear that the glider stops in it's tracks on the upwind and falls off on the downwind. The glider's momentum bleeds off on the upwind side and it's momentum has to be accelerated on the downwind turn. That's done by gravity, inertia, etc. and has been thoroughly thrashed out over the years. The heavier the glider and the faster it flies, the less noticeable this phenomenon is. If you continually tighten the downwind side of the circle, and loosen the upwind side, you move your circle upwind, and therefore out of the thermal, into the sink. This is how full scale pilots and R/C pilots move their circles to core the thermal. Any good glider school teaches this to it's student pilots. Some think full scale and RC have nothing in common, but I've scratched out from 400 feet in a full scale and the turns are exactly what you describe.

You should move your circle to get the best lift on all sides and easing off the bank and tightening it are the best way to do that. In wind, this is usually a constant battle. However, the practice of constantly trying to make your circle look round from the ground will fly you right out the upwind side of the thermal, every time.

Go downwind and go up, or stay upwind and fall out. It's just one of many tradeoffs in soaring.

Jack Womack

[nuevo]

I also have to disagree with SoaringDragon and fprintf.

Once you find lift, set your bank angle and maintain that same bank angle as you circle. Your plane (and the thermal) will then drift with the wind. It appears as if your plane is accelerating on the downwind side and decelerating on the upwind side, but this is an optical illusion becuase the plane is circling in a moving airmass and the pilot is standing still on the ground.

I won a contest this past weekend with winds in the 12-15 mph range for several rounds. I did this by finding any lift I could and circling, climbing and letting the circle drift with the thermal till almost 1/2 mile downwind. The only trick is making sure you have the altitude to get back. :D

( If you doubt the 1/2 mile, lets just say my 130" span plane completely disappeared for about 1/2 of every circle for both me and my timer. )

Best regards in your quest for knowledge.

Jon

[leverick]

Soaring Dragons advice is actually right depending on the conditions. If the thermal is drifting as a result of strong surface winds then you have to drift with it, that is, elongate your downwind leg of the the 360. The surface wind alone will do some of this but you may need to add some downwind leg as well.

HOWEVER, as SoaringDragon suggests, sometimes it's prudent to move more upwind to find the core. I discovered this many times with cross country hang gliding. Thermals can be strong enough to punch vertically threw a strong surface component and drift less downwind then you would expect. Depends on the day (conditions), depends on the thermal. Thats what keeps us coming back for more.

CHEERS,

Leverick

[nuevo]

leverick,

of course, you are expected to re-center as you climb. I am constantly evaluating which part of the circle gives me the best climb, and extending my circle to that direction. In less than boomer conditions, I am doing this evaluate and correct on every circle.