Giant scale Cub servos and servo power

[hornant]

I am thinking about doing a conversion on the world models 1/3 cub. 28lbs flying weight. The motor ESC batt side of things is no problem but I need some help with what type of bec and the size and power of the servos for this thing.

I have done about 20 conversion, many of which can be found on this forum but the biggest to date is only 13.2 lbs.....28lbs is a bit of a jump.

Looking forward to some words of wisdom

[staggerwing]

All depends on how you intend to fly the plane---scale like or aerobatic ?
Scale, I would trust min 70 in/oz servos using short throw , (1) per ail, rd, & elev; Aerobatic, min 90 ea surface &/or (2) 60-70 for ea elev half.
Personally I would not use a bec as a plane of this size & type will easily handle an adequately sized RX batt w/ no weight detriment.

[Ercoupe Ed]

Dymond Model Sports in San Diego California has a good deal right now on servos, and has one that puts out 80 in lb of torque.
I think if you buy 10, they give you the 11th servo free.A buddy of mine just bout a bunch of them, and the price is very reasonable.
You can order online, just put Dymond Model Sports in your browser to pull them up.

Good luck on your project!
I myself am considering electric power for a Hanger 9 Taylorcraft and a 90 inch Piper Cub kit I have.

[GordonTarling]

In a model of that size and weight, you should really be considering using a dual power supply of some sort. Maybe a BEC of some kind, plus a receiver pack. Either that, or just two receiver packs.

[staggerwing]

Ed,
Re your Taylor Craft--do a search in the "power systems" forum for my H9 Taylor Craft ---it's under C6362 .
At the time, this forum didn't exist.

Bob

[GWRIGHT]

I'd go much larger than mentioned here on servos. On my 15~16 pound conversions I use 192 oz/in servos on most things, then either two of those on rudder, or on one occassion a single 270 oz/in on rudder. All digital of course. Yes I have used lower torque servos,..and on one 12 lb plane (just a little 80-incher) the 132 oz digitals I originally installed could be stalled with at anything above 1/3 throttle.

[flattop]

I agree with Gary. There are several "servo" programs that calculate the torque and I am always very surprised at the amount of force that is needed to move a control surface. Also remember that you need a safety factor. I recently saw a 33% Pitts go in because he could not pull out of a dive, the increased airspeed overpowered the servo and he went in on a perfect 45 degree line .......splat!!
Charles

[Ercoupe Ed]

Ed,
Re your Taylor Craft--do a search in the "power systems" forum for my H9 Taylor Craft ---it's under C6362 .
At the time, this forum didn't exist.

Bob

Staggerwing,
I looked up the post about the C6362 and your T-Craft.Very interesting.
Thx,
Ed