Delta Wing Mixing 101
As a lot of newbies to delta wings often ask the question "Why is the mission planner not doing the necessary mixing for my servos to just work?" well for the stabilize the mission planner will work but not for manual and that is where the problem comes in because you need to lift of in manual and if your remote is not configured correctly your plane will just crash.
Lesson 1 : Never think inverting channels will fix anything.
If you mix your channels correctly life will brighten up, for delta wing mixing you have the following:
You will notice that you have CH1 and CH2 and there is 100%'s and +'s and -'s and its all very confusing and it gets more confusing once you notice that each channel has elevator and aileron defined.
ok lets start
- You have channel 1 and 2 because you insert your servos into channel 1 and 2.
- You have aileron and elevator because these 2 servos does both its called elevon.
- The % defines how much the servo goes forward and backwards (in most cases you do not want 100% for that will strip the gears of cheap servos)
- The 2 plus signs defines that there are two or more additional functionality to the channel
- And the minus well both % can go positive or negative
Scenario 1 : Elevator and aileron moves up and down together no matter how I move the sticks
Solution : This because all of the % is either negative or positive only the elevator must be the same.
Scenario 2 :When I move the aileron stick left and right the elevons move independently up and down and when I move the elevator stick up and down the elevons move together up and down, but the when I move the elevator stick down the elevons move down where it should go up.
Solution : If both elevators is in a positive percentage move both elevators to a negative percentage and vise versa.
Scenario 3 : When I move the aileron stick to the left the left elevon down and the right elevon moves up.
Solution : Change the aileron % to the opposite polarity so if CH1 was negative %, change it to positive % and vise versa.
The following 2 points is very IMPORTANT.
- The elevons needs reinforcement if it is made from epo foam but not too much it needs to be really flexible.
- When you move the aileron and elevator to their max and the piano wire starts bending, your % on the mix is to much, tune it down till the piano wire does not bend any more.
Hopes this helps a lot of people.
Comments
This is a great article.
I would strongly consider replacing the control surfaces with cloth hinges and balsa aileron stock if you have an issue with control surface flex, flutter, or loose hinges. Mechanically adjusting control surfaces on aircraft seems to be a lost art. I would adjust the control surfaces so you have maximum deflection at 100% throw to prevent you from destroying servos. Some transmitters will also allow you to set either the maximum travel (ATV) on the channel or from the mixing menu to 140%. Using a shorter arm on the servo its self also gives the servo more torque. Mechanically zering the control surfaces to bring the trim back to zero makes it easier to set up another transmitter or replacing hardware.
The other thing I noticed with delta/elevon mixing is when you get into the extreme corners of the transmitter range, some radios have the ability to limit the maximum throw in these regions, some do not. If they do not, you have to lose take out throw in the middle which is a problem on planes like the Skyfun or Radjet that use all the elevator control you can put into it.