thermal turning

[rpavich]

Hi,
I have a question about the proper stick use during turning.

I've had my rudder coupled with ailerons so far but I had a friend say that I should learn total two stick flying; rudder seperate from ailerons.

Can someone give me the whole enchilada on flying this way for thermaling or otherwise? I've even read that sometimes you need opposite aileron during a turn????

thanks,
bob

[Frank S]

Here's an article on the subject written by Mark Drela: http://www.polecataero.com/articles/rudder/index.html

[rpavich]

Thanks very much..I'm off to read!

bob

[rcbrust]

Bob,

I'm just wrapping up my first season flying HLG so I'm no expert by any means. After upgrading earlier in the year from a R/E Sidewinder to an aileron XP-3, I decided to uncouple the rudder and ailerons and teach myself to fly with both sticks. I figured I better make the switch before I got too used to thermaling with just the right hand.

Well, the bottom line is I'm very happy I made this choice. I think you end up with much better control of the glider during thermaling. I tend to use the rudder to adjust the turning radius and the ailerons to adjust the bank angle. With a glider such as the XP-3, which seems to have very good spiral stability, I find that I need very little input during thermaling, unless the thermal is turbulent. I tend to have to work the rudder more than the ailerons which I like because it holds the wing's airfoil in proper position.

Also, like you mentioned, I've found that most of the aileron adjustments I make tend to be opposite aileron. This obviously goes against flying with standard rudder/aileron coupling. Give it a try. I takes a while to get used to but in the end, I think you'll be better off.

Randy

[schrederman]

The flat winged models we fly these days are no different than the full scale sailplanes. When the turn is initiated, rudder is required to keep the turn coordinated. For most models or full scale ships with little dihedral, a little rudder held into the turn, countered by opposite aileron the keep the bank angle constant, is what is required for a smooth constant climb. This is of course helped by up elevator input to continue the climb, by keeping the whole circle performed at minimum sink speed, generally just above stall. I tried this on a friend's aileron ship Sunday afternoon, and it works quite nicely. I used the rudder trim to keep the circle where I wanted it, and the elevator trim full back, and moderated the bank angle with the right stick as needed...climb was very nice and I enjoyed it very much. I have a Sapphire ordered...wish it was here!!!!!!!

Jack Womack

[rpavich]

Thanks for the tips...

I'm gonna get out there and keep at it...

I tried uncoupling the rudder and boy it was hairy to say the least..my turns without a little rudder mixed in suck....


bob

[rcbrust]

Bob,

Jack brought up a very important point that I neglected to mention. During thermaling, I basically use elevator input as a speed control. Like he said, you want to keep it just above stall.

I also wanted to mention one other thing. It will take some time flying two handed before you start to react instinctively with your left hand. This will show up if you're landing with flaperons down. In this condition, aileron response is very low and you're much better off using the rudder to steer with. After flying this way for a few months, I'm just starting to get to the point where if a gust hits me during approach, I naturally hit the rudder to correct.

Jack is also correct with his comparison to full scale sailplanes. There is one major difference however. I used to soar full scale and let me tell ya, it's a lot easier when you're IN the plane! :p

Randy

[rpavich]

Thanks for the info....
So...you're saying that turning is mostly about rudder and just a little aileron for roll control? I've been backwards...I've just been using the right stick mostly and using the rudder for pointing in the right direction mostly....


bob

[rcbrust]

With the XP-3 I'd say I average a little rudder and a little up elevator and pulses of opposite aileron while thermaling. How little I use greatly depends on how "smooth" the thermal is. There are some thermals that are very violent and all this goes right out the window. I'm all over the place with the sticks just to keep from getting spit out of the thermal. I've also been in thermals that were nice and large and gentle where I could almost sit the transmitter on the ground and have the glider thermal on up. :)

Randy

[BMatthews]

So far all this has been about how to fly when already IN the turn and what has been said is the way I found it to be also. But rpavich, you should know that you want to use the rudder and ailerons together in the same direction during the entry to the turn and only once into the turn neutralize or hold a little "top" aileron. Using the rudder during the entry combats the adverse yaw that many sailplanes get thanks to their aspect ratio.

Also I found the amount of "top" aileron was dependent on the bank angle. Shallow turns needed little or no top stick while steep turns needed quite a lot of top stick on one model and much less but still more than just a gentle squeeze on the second one I had a chance to fly.

[rpavich]

thanks bmatthews,
I'll keep that in mind. I appreciate the way everyones is unloading their knowledge on me!


bob

[Daemon]

I'm somewhat of a sloper at heart, but have managed to speck out almost everything I fly (including the lead sleds) in thermals, so I've finally started flying more left stick. I think I always sorta knew it was the right way to do it, but seldom cared because the thermal lift was "good enough", and because I'm flying recreationally, not competitively. I think someone flying right stick alone to the very best of their abilities will often out perform someone who hasn't mastered left stick fully but is trying, because every extraneous input adds drag, and flying one stick smoothly instead of two less smoothly is still better.

Where I originally started to see the usefulness was during some "saves", flying my handlaunch in mixed slope/thermal lift and having the wind just completely die on me and having to work hard to find a thermal and bring it back up for 2 or 3 hundred feet below me. I remember one late afternoon the wind just *shut off* for the day, and I'd just hit some nasty sink before that so ended up with no lift way down slope. My Omega HLG was getting small, but in the wrong direction.

I cruised around for several minutes sinking ever lower and finally caught a last gasp thermal of the day just hugging the hill and only about 12 feet across (that's a challenge with a 14oz HLG). I had a long time to work it, and remember observing how keeping the wings as level as possible was buying me a lot more climb rate than trying to core it tightly, so I threw the rudder over to an extreme and held the bank only a few degrees into the turn. I know it was slipping to the outside some but it worked better, and I recovered it from several hundred feet down and the lift finally shut off about the time it dropped at my feet.

I so seldom ever have to work that hard, that I didn't really focus on it until after I got my DLG and started working more flatland thermals and seeing Mark's discussion of it the Handlaunch forum. I'm still not convinced that the glider slips inward as much as he lets on when you fly aileron only, but it's obvious that the default aileron->rudder mix is working against, and it makes sense that if you're counteracting that slip with increased bank angle to pull the nose down into the turn, then you're losing efficiency because you'll be flying faster and using up more lift to combat centripedal acceleration. It should be flying slow and rotating around the inboard wing. Applying opposite aileron also effectively gives the inside wing more camber so it can fly slower, and the outside a little reflex so it can fly faster with less drag.

It occurs to me that my Stylus has a 3 position switch bound by default to the aileron -> rudder coupling. I'm contemplating putting a reverse mix in the third position I've never used before, that mixes opposite rudder to the aileron and give it a shot in a minimal sink thermal turn. It'd pretty much only be good for one speed and bank angle, but might work. Optimally I should set up a mix that mixes rudder back to slight reverse aileron and then try to fly mostly left stick (I think Joe Wurts does that), but I'm not quite ready for that yet.

ian

[Bierlein]

I don't know if all transmitters are the same but with the Hitec I have, when I couple the ailerons with the rudder, the rudder can still be operated independantly. Depending upon the percentage of coupling, the rudder can be set up for full throws.

This seems to give me the best of two worlds where I can input more or less rudder when I'm in a thermal.

AL B

[Daemon]

Ya, most radios that have that mix work that way.
It just means that you have to apply *more* rudder because you typically hold a little opposite aileron while maintining a thermal turn, and the aileron->rudder mix is the wrong direction for that, so you have to apply enough rudder to cancel that, and then enough more to actually point the nose into the turn to coordinate it.

But yes, that's pretty much how I fly.

ian