Originally posted by patternjockey
Hi Craig
First off I do not have a 9Z yet but most dual rudder planes (with two servos) can be set up with a simple c-mix. Activate a C-mix and assign the master as "Rud1" or "rud" and then assign the slave (other rudder servo) as "AUX2". Activate it so it's on all the time at 100%. Make sure your extra rudder servo is plugged into the "Aux2" slot. By making expo & dual rate adjustment to "Rud1" the other rudder "servo" should follow exactly.
I use "Aux2" as an example only..not sure what the zapper calls them.
Perhaps I have misunderstood and have oversimplified this.
Not sure.
Basically you are right. A channel mix is all that is needed. And it can be any available channel except channel 9. Here are some additional notes;
When you are mixing the rudder servos with the P-Mix, use a multi-meter in line between the receiver and the servo. You will use that to check for binding, and when setting up the ATV's and neutral position. You will check each servo, and adjust the mixing at neutral and each end point to get the lowest current draw at those position.
Make VERY sure that you have the trim linked in the mix, so that when you adjust the rudder trim, each servo reacts to the trim adjustment. If not, when you trim your rudder, one servo will offset the neutral position, and the other won't. You will introduce binding into the setup, and cause a high current drain on your packs.
Make sure you are using the right type of mixing. Using the mix mode that will track the slave from the master, and ignore external influences that do not affect the master channel. There are mix modes that use the stick input only, the master without other linked mixes, or the master will all linked mixes, etc. I forget what Futaba calls them, so I wont guess in case I am wrong. I'll look it up later for you if someone else doesn't add that imput.
Once you think you have it setup. Leave the multimeter in-line, and run through all your switches, mixes, rates, trims, etc, and verify that none of these cause the tracking to change. I flew a nice 40% airplane for quite a while that had ganged rudder servos, and didn't notice that my trim changes introduced binding on the rudder setup. The previous owner either forgot, or didn't know, that he didn't have the trims linked. Luckily, I caught it during a routine maintenance check before it did any damage.
I'm sure the servos were very unhappy for a while there.