I AM GETTING READY TO FLY A EXTRA 300 WITH A SERVO ON EACH SIDE FOR THE ELEVATOR. THE QUESTION I HAVE IS WITH THE TRIM. I HAVE AN ECLIPES 7 RADIO AND WIRED ONE SREVO IN THE #2 SLOT AND THE OTHER IN THE #5 SLOT AND MIXED IT TO GET THE PROPER THROWS. NOW IF I TRIM THE ELEVATOR ONLY ONE SIDE MOVES. SO MY QUESTION IS WILL THIS MAKE THE PLANE ROLL WHEN I ADJUST THE TRIM FOR LEVEL FLIGHT OR WILL IT ONLY (MOSTLY) EFFECT THE PITCH.

It'll have a very small roll effect but it'll likely be hidden by normal flying actions.

Why not run the two servos off a Y cord instead of the separate channels? That way you get your trim action out of both servos and can keep that other channel for a separate function of some form.

I TRIED IT WITH A Y-HARNESS BUT I COULD NOT GET IT DIALED IN CORRECTLY, IN THAT ONE WOULD GO FURTHER IN ONE DIRECTION OR THE OTHER. I TRIED TO BUY MATCHED SERVOS, MEASURED THE LINKAGE AND ADJUSTED EVERYTING IMAGINABLE. ANY ADVISE WOULD BE APPRICIATED.

Your mixing could be a bit off. I had a similar problem with a Futaba set up I had on a plane with elevons. I had to change the percentages in different sections to get the throw to be exactly the same. If i remember right, I had set one of the throws using the chanel output percentage and the other using the mixing percentages and for some resason it affect the throws slightly. When i set the channel percentages to be equal and then adjusted in the mixing section I was eventually able to get the throws identical.

Simple way around that is to use the threaded rod style of control horns. Then what you do is on the side that moves more than the other you just wind the connector tab out a turn or two and try again. At some point the motion will be so close to identical that it'll be fine.

But I must admit that I had not thought about the fact that there is tolerances and differences in servos like you found.

To start:
Both elevators must be hinged at exact same centerlines
Both control horns must be at same height from hingeline
Both must be at same vertical from hinge line
both servo arms -same angle on output arm
both servo set for same travel.
with power on radio , move both elevators to center position .
adjust only push rod length to obtain center .
move with power to desired full up /down.
write down difference noted.
If one side moves further both ways , lengthen that side control horn (threaded type best )
if one side moves further in only one direction-- move control horn forward or back (bend slightly) OR move servo arm one spline forward or back (this makes big difference!)
Once you have established that the mechanical setup is as close as possible ,make minor adjustment on Tx throw/sub trim/center
Note that any change in Tx is always interrelated --that is --each adjustment affects other adjustments
change of center affects relative throws.
Please use lower case on your postings -It makes them easier to read .

With a GWS (or similar) V-tail-Elevon mixer you can plug both elevator servos into the mixer outputs.
One of the mixer inputs is plugged into channel 2 on your receiver for elevator.
The other mixer input must also be plugged into the receiver.. for this example I use channel 6 which is unused in this application..
Both elevator servos will then trim identically from the trim button, and respond to dual-rate changes and EPA adjustments.
.
But a Y-harness accomplishes the same thing.

If your transmitter cannot mix two channels and apply the proper trim to both, buy a "Miracle Y" from Max Products. The "Miracle Y" will reverse the direction of one servo and also provide a travel adjustment for one servo. I've used them in Sport, Pattern and Turbine airplanes. They work great.

corsair0307,

I am not familiar with the Hitec. Usually P mixers have additional settings to that need to be activated to eliminate your problems. The first on is usually called "include trim" or simply "trim." When this is on, the P mix accepts the trim input as part of the master input also. Yours is currently not doing that? Futaba has another feature called "include." This has to be on to allow other mixes to the elevator function to be included in with the mixing of your second elevator. Might be needed for dual rates too? Check that when you change elevator rates, the slaved second elevator throw changes too. Jr P mixes have a feature called "origin" which must be off to allow this. These are examples of additional P mix features to find out about for your Hitec.

Multiflyer

Hello,
I think Dick stated a good list of things to check! It is not simple to do each of these right, and only one off can give different throws!

Another very good explaination, especially how to use subtrims is that one:

http://www.rcaerobats.net/DualElev.htm

As Bob says, subtrims must be used only to center servo arm, in order to make it parallel to the hinge line. Then they must not be used anymore, concentrate on mechanical linkages in order to make them as equal as you can. Two things, as Dick said, are easily overlooked:

1) Control horn clevis hole, often this is not on hinge line.
2) Control horn clevis height, the two horns should be identical!

I spent hours trying to figure out howw to get 2 servos on seperate channels to work with the Eclipse 7. Finally sold that and bought a JR9303. Took me about 10 min to set up my plane.

I don't think that set-up will work with the Eclipse.

Anytime you use split control surfaces you leave a HUGE chance of a very small error.
Reason I had found was the near perfect requirement of getting BOTH elevator horns in perfect vertical and horozontial alignment.
Plus the slots in ALL 4 areas had to be perfect also.
The jigs that I built ONE time convinced me it was not worth it.
Do the electronic. Unless you are a Competition Nut.