Regarding the nose down turns, it is sustained throughout the turn, and gets progressivly worse!

It is noticable in wide gentle turns (20'+ radius), but not as much as in a tighter turn. I have been tossing the plane into the wind at an angle so that the plane turns downwind very near the top of the throw, I then have lots of air speed to make the upwind turn, and I see the nose down behavior then also, so it would appear to me that in this case I'm not flying too close to stall speed. Although at other times it was quite obvious that I WAS!!

From : Don Stackhouse

There's another possibility here, it's probably something you already know about, but I'll mention it anyway.

You don't steer an airplane the way you do a car. You roll the airplane to the desired bank angle, CENTER THE RUDDER/AILERONS (whichever applies to your aircraft, rudder in this case), then feed in enough "up" elevator to hold the pitch attitude constant. You may need to apply a TINY BIT of rudder to hold the bank angle constant, and depending on the design it could be towards the turn or away from it. Each design is different, and you might have to hold it one way for some bank angles and the other way for other angles. Just use whatever you need to keep the bank angle constant.

When you're approaching the end of your turn, give it opposite rudder/aileron to roll the wings level.

In a "coordinated" turn, the centrifugal force of the turn combines with the force of gravity on the model to make a total force that is perpendicular to the wings. THE MODEL THINKS IT IS IN LEVEL FLIGHT! If you continue to hold the same rudder deflection into the turn that you used to initiate it, the model will continue rolling to steeper and steeper bank angles, eventually completely upside down and then back upright again. On a no-ailerons model like the Chrysalis, the nose-down effect of the yawing caused by the rudder will push the nose down into a spiral dive as you get to steeper bank angles, so it's tough to do a roll unless you pull the nose up before entering the roll, and give it some "down" elevator during the inverted portion of the roll.

During a thermal turn, two other factors come into play. The wing on the inside of the turn is moving slower than the wing on the outside of the turn, so it naturally wants to make less lift. This will try to make the model roll into a steeper bank angle, something we call "overbanking effect". On the other hand, the curvature of the airflow around the model due to the turn will result in the airflow at the tail being inward relative to the airflow at the wing. This will tend to yaw the model towards the outside of the turn. If you have enough dihedral, this yaw will increase the angle of attack of the inside wingtip, offsetting some or all of the overbanking effect. The combination of these two factors will determine whether you need to hold a little rudder into or away from the turn.

Every time you think you have this flying stuff all figured out, somebody brings up yet another factor to consider. I know, it's not fair!

Regarding upwind/downwind turns, there is no such thing, at least from the model's point of view. It's flying around inside a giant chunk of air, and has no way of knowing, and couldn't care less, that this chunk of air is moving across the ground. If your model seems to behave differently for turns one way or the other, it probably means either it isn't built perfectly straight (and all models, no matter how well built, have some amount of asymmetry), or you are flying it differently one way vs. the other because of your ground-based point of view. For example, R/C pilots often tend to fly slower going downwind than upwind simply because the model "looks" like it's going faster.

The infamous "downwind turn" myth has similar origins. You're flying upwind, start turning towards downwind, the model appears to be speeding up, so you instictively give it more "up" elevator. The model stalls, because you gave it too much up, due to the speed illusion. The opposite happens turning into the wind. Even though its airspeed is constant, its groundspeed decreases due to the wind. It doesn't know or care anything about groundspeed, but the pilot standing on the ground (or in the case of a full-scale aircraft, the pilot in the aircraft looking out the window at the ground) sees the apparent speed decrease, and shoves the nose down. Voila! A nose-down tendency during "upwind" turns!

In this situation, it's all in your mind. v Watch the attitude of the fuselage, and try to hold that exactly steady, that will help keep you out of trouble with these speed illusions. It generally works better to fly models by watching angles rather than speeds. On the Chrysalis, if you concentrate on keeping the fuselage exactly level with the ground in cruising and turning flight, your airspeed will be close to optimum all the time.

Speaking of optimum speed, on a modern hand-launch sailplane the optimum thermalling speed is usually fairly high, well above stall. This is because of Reynolds number, or "scale effect". This is the effect that explains why our models don't fly the same as full-scale aircraft, and why full-scale airfoils are often lousy on models. Reynolds number is the product of size (usually wing chord in most calculations) times airspeed times air density, divided by air viscosity. At sea level, it's 778 times chord in inches times speed in mph. As Reynolds number ("Re") goes down, drag goes up. At Re's typical of a thermalling R/C HLG, the drag increases get pretty dramatic. As you slow down, long before you reach stall, the drag increase from the reduced Re has already brutally murdered you glide ratio, and taken the sink rate with it. The model falls out of the sky like a parachute. This is one of the most common mistakes of beginning HLG fliers, flying too slow in the mistaken notion that it will reduce their sink rate or help them glide farther.

I don't think that it is nose heavy, but it might be. It seems to be worse in a left hand turn than a right hand turn, and coincidentally that is the ch 1 servo which isn't allowing me to adjust the up / down end points. I can correct for the nose down with some up elevator, but then get some nose up as I exit the turn, and kind of flounder. I need to Practice..... I have to figure out how to reduce the up elevator just prior to exiting the turn...

Yup, that's the secret, the "P" word! Roll into the turn, center the rudder and simultaneously pull just the right amount of "up", then center the elevator and roll out of the turn with opposite rudder. It's like figure skating in the air, you need to learn how to coordinate several different movements at the same time. If it was easy, it wouldn't be as rewarding when you finally get it right!

If it's behaving noticeably different in one direction than the other, that's a good indication of a warp somewhere. Check the fuselage, but also check the wing. It doesn't take much asymmetry in the wing to create all sorts of problems!

I WILL try the level flight - quick turn input, to see how the plane reacts tho! I will re-check the CG location carefullly also. I'll recheck the servo arm setup too!! I think that with the information you have provided I can get it figured out.

Oh yeah.. just thought of something... I marked my centerline on the bottom sheeting with a wooden yard stick, so my centerline isn't quite 100% straight. The fuse has a slight curve to the right (as viewed from behind). The rear of the fuse is off center by about an 1/8". I am aligning the wing with the tail though.

That amount of warp in the fuselage shouldn't make too much difference, as long as the tail is square with the wing, and the wing is square with the tail.

BTW, if you're not sure about the straightness of your straightedge, just draw the centerline, then flip the straightedge over and draw the centerline again uysing the same two reference marks. You'll get a double centerline, with the true centerline lying exactly halfway between them.

Would it be ok to forward your reply to rec.models.soaring ? There isn't any specific question there now that this relates to, but maybe it would be helpful to others.

Certainly, just mention where you got it. You might also suggest a visit to the "Ask Joe and Don" section of our website at http://www.bright.net/~djwerks/

Don Stackhouse
DJ Aerotech