Hi, Im building a GP extra 300s .60. I am putting an os .91 fx on it and am just wondering if anyone has tips on what size servos to use. I will probably use two for elevators with a non revrsing y-harness. Not sure whether to go with a pull pull for rudder yet. And ailerons im just not sure. Any advice would be great advice.

Here is a link to a calculator that should provide the answers for you.

http://www.csd.net/~cgadd/eflight/calcs_servo.htm

Thank you for the link only the first question it asks is max speed. I dont know that, dont have the plane built yet.

The speed is something you will have to estimate. Figure this way, a trainer flies at about 40 - 50 mph (normal top speed ), a warbird is going to fly at about 70 mph. MANY aerobatic planes similar to the 300 are PROBABLY not going to be flown at much over 70 mph.

To be safe, I would put in 70 mph and see what the calculator suggests, then redo it using 90 mph. The difference in cost between a 75 oz servo and a 100 oz servo is minimal. The big difference is normally the weight difference (unless you are talking digital $$$ ).

Hopefully someone with that plane or a similar one will chime in with a more accurate top speed.

I have never clocked it, but I would guess 75 is about the top speed for this plane. I am using standard futaba s3004 servos in mine with a 6v NIMH receiver pack. Works fine.

I have been flying the 60 size GP Extra (that I built last winter) this spring using nothing more than 5 standard Hitec 425 servo's. That's one on elevator, one on rudder, one per aileron and one for throttle. Works great, although my engine is an older 60. I don't think you need any more servo torque than standards. P.S. I'll be visiting family in Calgary in July during the Stampede...I'd like to visit a flying field when I'm there...my sister lives in the SW. Any club fields around there?

Here's a little freeware thing that calculates static thrust and estimated speeds based on prop size and rpm - which is info you can get before finishing the plane.

http://freespace.virgin.net/barry.ho.../thrusthp.html

That torque calculator told me I'd need 5.xx oz/in on a Goldberg Super Chipmunk with a max speed of 100mph at normal throws. For some reason I just don't think 5 oz/in of torque will be enough.

Ok. Thanks for the info everyone.
Chevelle, There is a flying field in the S.E. of Calgary called C.R.A.M.S. Its on 68th st. south of 17th ave. S.E. Im sure your family that you are visiting could direct you there or better yet take you. Also, are you using a pull pull system on your rudder?

I think the Hitec 475BB's (Karbonite gears) are about the best servo for the $ for a 60 size plane. Not being digital, the price is down, but still will give 67 lb. torque on 4.8 volts. I am running those in my Ultra Stick 60 and they are plenty.

Ernie