jsm77777

My Feedback: (4)

What is the verdict on the use of 2 or 4 elevator servo's in the Composite ARF SuperExtra 3.1. I have heard people using 2 and 4 with sucess, but would like to know what IS truly needed. I am most worried with weight in the tail, and would like to keep it light back there, if possible. I am using a 3W-150 QS on cannisters, and 8611 servo's all around, and lipo batteries. Any help would be great. Thank's, Scott

Richo

Hi Scott,

I was like yourself, unsure. I ended up using 4 8611's on the elevators. I didn't want to have the rear end fail due to flutter. I know guy's are getting away with 2, but maybe that's just it, they are getting away with it, "for now". Probabilities are if you manage the throttle well and dont get into any high speed dives etc, you may never experience a problem with 2 servo's. I also considered mass balancing the elevators, instead of adding 2 more servo's, but the weight difference between the 2 options is so close that 4 servo's was the only option. In the end I didn't think it was worth the risk. I got mine to balance without any added weight. (wing in rear position). You will need to put the batteries up front in the engine dome. I also used crossover headers, which will bring the canisters closer to the engine, and putting a little weight futher forward.

Cheers,

Richo

Hammbone

My Feedback: (309)

I don't have this plane, but have admired it and may get it some day.
If I remember correctly, the servos on the elevator are ganged with one attachment point on each elevator, corrrect?
If this is the case, I think I might use one Hitec 5955 servo on each elevator half. The Hitec 5955 has 333 oz-in of torque (on 6V).
This should be plenty.
With the availabilty of these higher torque servos recently, we shouldn't have to gang servos as much anymore. Here's an oportunity for us to keep it light and keep it simple.

Jim

Richo

The elevator servo's are not ganged together on the Superxtra. The aileron servo's are. Perhaps you were thinking of the 3.3 Yak.

Cheers,

Richo

Hammbone

My Feedback: (309)

Yeah, I must have been thinking about the Yak. Sorry about that.

If there were just one attachment point on each elevator, then it would just be a matter of getting enough torque to that attachment point. Since there are 2 attachment points, I'm sure it's for a reason.

I bet there are some guys using one servo on each elevator on this plane, but I would agree with Richo and use two per elevator.
I'm sure the designers of this plane have put a lot of thought and testing into their design. I'm not going to second guess their recommendations. I'm sure they thought about balance also, and it should balance fine with 4 elevator servos.


Jim

2.6mrod

hi scott

use 4 servos jr 8511 in the tail of the 3.1m, i thought long and hard about this, i flew the plane with 2 servos for 6 months with no problem but noticed a bit of slop in the servo when you lift the elevator up and down by hand,
the advice i was given by our c arf dealer was the more you fly this plane the more you will put it through its paces,and that is when the 2 servo set up will fail.
now i have the 4 servo set up my mind is at ease when throwing the plane about.
regards rod

schroedm

My Feedback: (1)

Hi Guys,

PLEASE USE 4 SERVOS!!!!

Can I draw your attention to the "Announcements" page at www.composite-arf.co.uk

This is an official Composite-arf.com announcement that needs to be followed in order to maintain continued factory support.

Has the rep you purchased Your SXs from contacted you regarding this issue?

Kind Regards,
Mark

jsm77777

My Feedback: (4)

I have heard from my rep about using four servo's in the stabs. I just wanted to see what others are doing, as I know a few using 1 servo with no problems (yet???). I first decided to fully balance the elevators, but found it would take about 6 ounces in each counterbalace to fully balance it. That's 12 more ounces in the tail, and for half of that I can put 2 more 8611 servo's, and matchboxes in there, with tons of extra power, even though it may not need that much power. I am just concerned about cg balance, and I will see soon, as I am almost finished. Thank's for the help to all. Scott

2.6mrod

hi scott,
with 2 servos and the batteries up the front of the plane the cg was at the recommended front position,the plane flew well but was nose heavy,which is a good place to start anyway.
i was ready to move the cg back when this 4 servo issue came up,so with 4 servos and 2 matchboxes mounted beside the fuel tank the cg came out right on the rear cg recommendation with the wings in the rear position with no added weight,
at this cg setting the plane still flies like a *****cat i should have started here first up.
even if you have to add some weight no big deal you wont notice any difference in the way it flies.

regards rod

2.6mrod

forgot to mention it is a much better set up with alloy swb arms and titainium rods make sure you have these rods screwed in all the way on mine you cannot see any exposed thread because the next size down rod does not allow enough thread to screw all the way in, as i found out the hard way by landing the 3.1m with one aileron , as the rod had pulled out of the threaded ball link.(wondered why the roll rate had slowed up ??) anyway hope this helps this is an awesome plane
rod

jsm77777

My Feedback: (4)

I already got the SWB arms, and will use them on elevator and ailerons. Using the set-up in the kit for rudder, as I'm using 4 8611 servo's there. I don't think I will have any problems there with stripping arms, since all the load is spread out over 4 servo's, and the set up allows for perfect alignment without needing matboxes there. I also make my own rods out of 1/8" material, and can cut the threads to be a very snug fit. Thank's again for all the tips, Scott