DX9 throttle and elevator Mixing

[Loneflier]

Hey Guys-I have a new 71" ARF Piper Cub that I am finishing up, and did the maiden flight this last weekend. Even though I set up the CG per the instructions, it still felt a bit tail heavy, especially during banking turns or under full throttle where it wanted to climb almost to a stall. I had to correct with down elevator each time. Currently, the CG is at 84mm from the LE and the wing chord is 250mm. I am thinking I will move the CG forward to somewhere between 25 and 30% which means the back edge of my CG range will now stop at 75mm. I am hoping this will correct the issues I am having with climbing.

However, and this is where I need some help; a friend of mine suggested setting up a mix in my DX9 so that when I go past 50% throttle, I can mix in some down elevator to counter the climbing tendency.  I have already gone to mix1 and set throttle>elevator, but there are 3 different parameters and I can't tell for sure which goes with which channel, and why there are three entries to be made when I am only using 2 channels.

If anyone has done this, please give me some detailed instructions on how to set this up.

Thanks

Rich

[PappaBear]

RE: DX9 throttle and elevator Mixing

Hi Rich,

I may be able to offer you some help with your problem. Does the model climb in straight and level flight under full power, or does it only climb when its in a turn. Does it climb when turning both left and right.

If it climbs in straight and level flight, you might try adding some down thrust to the motor. This shouldn't be to difficult to do with an electric model. You may find this will cure the problem.

If it climbs only in a turn to the left or right. Try coordinating the ailerons and rudder in the turn. Some people mix the ailerons and the rudder, but personally I prefer to use the sticks on the TX. Also try making a turn using just the rudder, no aileron at all. Some models will turn better using the rudder, especially high wing models like the cub.

Let us know how you get on with it.

Martin.

[Loneflier]

RE: DX9 throttle and elevator Mixing

Hi Rich,

I may be able to offer you some help  with your problem. Does the model climb in straight and level flight under full power, or does it only climb when its in a turn. Does it climb when turning both left and right.

If it climbs in straight and level flight, you might try adding some down thrust to the motor. This shouldn't be to difficult to do with an electric model. You may find this will cure the problem.

If it climbs only in a turn to the left or right. Try coordinating the ailerons and rudder in the turn. Some people mix the ailerons and the rudder, but personally I prefer to use the sticks on the TX. Also try making a turn using just the rudder, no aileron at all. Some models will turn better using the rudder, especially high wing models like the cub.

Let us know how you get on with it.

Martin.

Thanks Martin,

To answer your question-Yes, it climbs straight and level under full power, and also wants to climb out of the turn. I had thought it probably needed some downthrust, but from reading reviews on the kit, they said it was already dialed into the firewall. I do know they did add the right thrust to the firewall. I was hoping to counter the need for adding shims since I already have the cowl mounted, and adding downthrust to the motor box will likely make me change the positioning of the cowl and possibly have to drill new holes to accommodate the change. That was why I was hoping to be able to program in a bit of downthrust into my radio using the throttle and elevator mix function. However, I may try to add about 1/16th inch shim to the mount and see how much it affects the alignment of the cowl.

As for the turns, I do use both rudder and aileron when flying most any plane, I have made that a habit, but possibly, this Cub needs more rudder than the others I have flown. I will try that next time I go out flying-hopefully this weekend if the weather cooperates.

I am hoping with moving the CG a bit forward, adding a bit of downthrust, either by shims or programming, that this Cub will begin flying more like the others I have. Thanks again for the help.

If you do know how to do the mix program I am describing, please let me know that too. It would be helpful to have that in my back pocket if I still need it!

Rich

[Loneflier]

RE: DX9 throttle and elevator Mixing

Hi Rich,

I may be able to offer you some help  with your problem. Does the model climb in straight and level flight under full power, or does it only climb when its in a turn. Does it climb when turning both left and right.

If it climbs in straight and level flight, you might try adding some down thrust to the motor. This shouldn't be to difficult to do with an electric model. You may find this will cure the problem.

If it climbs only in a turn to the left or right. Try coordinating the ailerons and rudder in the turn. Some people mix the ailerons and the rudder, but personally I prefer to use the sticks on the TX. Also try making a turn using just the rudder, no aileron at all. Some models will turn better using the rudder, especially high wing models like the cub.

Let us know how you get on with it.

Martin.

Hi Martin,

Well, I made some adjustments to my Cub, mainly moving the CG forward to about the 30% mark on the wing chord, and went out flying again this weekend. My first "take off" didn't quite make it up. The grass on the field is pretty tall, and with the extra weight up front, I couldn't get it to lift off. I brought it back to me, (at least I got some taxi time with it), and moved the battery a little more to the back, found some shorter grass, and managed to take off on the second try. The climbing issue seems to have been corrected with the slightly forward CG, but I found I had to run at nearly full power all the time to fly it well, and when I looped it, it just barely had enough juice to get to the top. I am flying with a 12x6 prop and a 32 size electric motor, which according to the specs should fly up to a 6 pound plane. I did finish with the trimming, and overall, she flies pretty well, just needs more power.

After I came home, I decided to head to the LHS for some help. I ended up getting another prop, this time a 13x6.5, and after getting it installed, I can really tell there is a lot more thrust available. I am hoping this will fix my lack of power issues. Also bought a larger tailwheel since the little one that came with the plane was really dragging along in the grass. With the extra thrust now, and less drag from the wheels, I am hoping my next flight will be much better. Slowly, I am getting her dialed in. This has been my first foray into the ARF world where I had to choose my own motor, servos, and such, and it really has been fun, but frustrating at times too. Once I get everything working right, I think this will be a great plane. Landings are pretty easy with it, she really floats pretty nicely, and has a very controllable descent rate.

Too rainy here to fly again today, but next weekend should be better!

BTW-you were right about using more rudder. I tried that yesterday, and it turned much nicer. Interesting, this Cub likes more rudder than aileron for turns, my others are opposite.