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DLG Newb Problem (altitude loss while turning)

#1
Hello. So recently I purchased my first Discus Launch Glider; a dream flight libelle. After much practice I was finally able to launch it high enough in the air to catch thermals. However, I seem to be encountering a problem when I fly. Even though the Libelle is very nice and floaty, I always tend to loose altitude very fast whenever I turn. Now I already know that airplanes naturally loose altitude when they turn, but when I turn with the Libelle, I loose like 7 feet. I think I may be stalling when I turn which leads to the altitude loss but I seem to be loosing way too much. I turn, stall, and fall. I was wondering if anyone has any suggestions for this problem. Could I have the CG to far backward? Do I need to mix in some differential with the ailerons or something? One time, I flew straight into a nice thermal and then fell about ten feet after encountering the sink. I know that it is normal to loose altitude when in sink but my plane just stalled and basically dove down ten feet. BTW. the Libelle is a 3 channel glider (ailerons, elevator, rudder) and I think the reason why I loose altitude so fast is do to pilot error, not the actual glider. The glider is really floaty when flying straight.
 

ztoon

Gone with the Mistral
#2
Hi,
I think you're on the right path... assuming cg is ok (not perfect is not a problem).
Personnaly I don't use ailerons and rudder mixing because I want to adjust the exact amount myself, even if it is harder to apply.
Seems you're stalling when starting your turn, keep some more airspeed and use both rudder and ailerons to turn. The tighter is the turn the more energy you will loose, so you need more airspeed when entering it (being in a strong thermal works too :D). When a thermal is weak and "wide" you almost turn "flat" with rudder to keep wings as horizontal as possible, maximizing lift. But too much sliding or sliping is not good so it really depends what uplift you found. When you found sink air, push forward, gain some airspeed and get out of there, you're just sinking, so the less time you stay is better.
Use low rate on your Tx in a thermal, you need just small and precise inputs movements.
 

kwak

New member
#3
Sailplanes cause the pilot to become much more aware of how the air effects the aircraft than in power planes. And flying a DLG means it is all happening right in front of your eyes. I personally love it.

Stalling is typically when the nose drops because of a sudden loss of lift on the wings. Simply flying straight and experiencing a sharp altitude loss when encountering sink is normal to sailplanes. It helps to point the nose down slightly to pick up some speed to get away from the worst areas of sink.

If the CG is way forward in a sailplane the plane will cover a lot of ground easily but will not turn as slowly and easily as when the CG is not forward. If the CG is too far to the rear the plane becomes unstable. It was many years of flying gliders before I eventually played with this.

Here is a general rule of thumb for sailplanes. Keep the fuselage (nose to tail) level. In a straight line when you encounter lift the tail goes up, and in sink the tail goes down. In a turn you typically have to feed in up elevator to keep the nose from dropping on its own. You can tell you have too much up elevator in a turn when the wing stalls and drops the nose. Another factor of stalling in a turn is trying to fly too slow. You want to fly slow enough that your turn stays in the thermal but not so slow that the wing stalls.

When you are circling in a thermal, if half of your circle is outside of the thermal it will look like the plane is not climbing in that part of the turn.

Something which can effect up and down air currents is if you are flying downwind of buildings or trees. They give off rotors which are sharp, closely spaced, up and down currents.
 
#4
As you bank, your stall speed increases, so you need a little more airspeed. If its not stalling, make sure you make coordinated turns, that means "the nose points forwards", not to the outside or inside of the turn. You need both aileron and a fair amount of rudder when you initiate the turn, but once you are banked, to maintain the turn, on most gliders you need a bit of rudder in the direction of the turn, and a little bit of aileron in the opposite direction.

Last point; you may just be banking far too steeply. When I put a mobius on my DLG I was surprised when I saw the result; I was banking far more sharply than I thought.

If in doubt, try recording and posting a video.