Can someone give me guidelines on the servo requirements for a 2M pattern plane?

I'd like to know what Torque/Speed/ and weight ranges are appropriate for Rudder/ Elevator/Aileron servos. I'll probably be using 1 servo on both elevator halves.

Look at the specs for the JR8411SA for el, ail, rud. Its adequate for all. For split elevators look at JR3421sa. For faster servos the 8417 is nice. Futabas work also. Use plastic gears they seem to stay tight longer.

I am thinking of a 2m widebody type plane here.

Brian

For Futaba servos. 9252's are great for elevators with one servo. 9650's seem to be the standard for a servo in each stab. 9154s or 9150's on the ailerons. I personally like the 9154's they are faster. A 9151 on the rudder is a great choice. I'm now running the 9351 with more torque, but unless you are flying FAI you probably wouldn't notice much of a difference. My personal setup is as follows.

9254 elevator, only 50oz torque, but lightning fast (.06). I've flown the new sequences without any problems, and CPLR won the worlds with this servo last year, so 50oz is obviously enough.
9154's on ailerons, 64oz, .14
9351 on rudder 192oz, .13
9650 throttle .14/.11, 50oz/62.5 oz I always run digitals on the throttle. Nothing like repeatability for being able to fly precision.

Arch Stafford

I'd like to understand the math behind any 'servo requirement'. Given some side area of a fuselage - let's look at the rudder, the plane is traveling forward in KE flight (I assume this requires the most rudder torque?) , the air is pushing up on the fuselage around some lateral CG location, as the fuse is being yaw'ed to hold the KE flight. Does a 20oz-in servo work in this case, holding up a 11lb plane? Depends on the speed of the plane, the side area,… other factors. All the servo has to do is yaw the fuselage around a CG point - not lift 11lb. On the elevator, all the elevator servo has to do is hold the plane at some angle of attack. Perhaps the worst case here is a Snap? Anyone care to guess what the min requirements might be for a servo? I have been using 4031's from JR for a long time, working fine.. this was a pattern servo way back when. Now we have servos with 3X the torque, are they better? I'm sure they center better, but that a different discussion.

sc

Following Scotts lead in re-thinking the 'servo requirement' I have gone to smaller lower torque digitals.

My set up:
Genesis ARF AXI powered
Ail- 9650s @ 62.5 oz/in
Rudder - 9550 @ 83 oz/in
Elevator - 9550

For 3D or IMAC style flying I can understand the higher torque requirements... but I have used this last set up in my last two airplanes and it works pretty well. My orginal reason for using them was to cut down on the weight and by doing so I saved 2-3 ounces. It wasn't too long ago that we were using 50 oz/in servos as the standard and had no problems... and those were ANALOG! Digitals are a whole new ball game.

Thanks for the replies.

So, it seems faster is better, of course, but .12-.14 is adequate speed.

50+ oz-in for elevator and Ailerons,
and perhaps ~150 oz-in for Rudder.

Does that sound about right?

I would have thought Ailerons would require less torque than elevator?

The only point of my post was to challenge the necessity for such lofty requirements for torque and speed. 150 ounces for rudder is a minimum for a similar sized 3D plane, but about twice what you need for pattern. But that's my opinion, I could be wrong.

The World Champ, CPLR, after all is using a high speed but low in torque servo for rudder as stated above. I am using 80 oz/in and it's plenty. With the higher torque and higher speed servos the centering will be better than the average standard servo. Definitely go with a coreless dual BB servo... high torque is not a necessity in pattern at all, but it won't hurt you either. The goal is a smooooooth servo that always comes back to neutral.

CPLR used a low torque high speed on elevator not rudder, he ran the 9351 (as did most) on the rudder, which is a 200 in-oz .13 servo. Most have gone to this over the 9151 (130/.18 ish) as the higher torque servo improves the rolling circle and rolling loop common in the F schedules.

I dont think this is required unless you are doing those manuvers...100 inoz on rudder should be plenty for most...60-80 on ailerons and 50 on elevators (or dual 50's if you run dual elevators).

Personally I went 9351's on rudder and ailerons to minimize the number of different servos I have....this way I only need a single spare that will work in 3 spots....I use dual elevators so 9650's go on them.

I stand corrected. Thanks Chad as always [8D]. Must learn to proof read!

Use the best servos you can afford, but remember at least for pattern, torque is not the most restrictive requirement.

if you are thinking in non-digital , , i suggest you the JR 4131 , it has an icredible speed , and 90oz of torque.
I have using this and the precision its very HIGH.

Sergio .

Hi all,

My setup is as follows:

Oxalys, 140RX, 9252 on ail and elev, 9151 on Rudder and 9650 on Thr.

i am struggling also in servo requirements, im thinking of buying a 2m pattern aircraft such as the ca models fantasy, i have previously used hitec 475 servos in a great planes christen eagle II and they worked perfectly, so these servos should be enough with 76 oz torque? except for rudder which i shall have to get a bigger servo?