1/4 scale cub - do I need 1/4 size servos? - RC Groups
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Feb 18, 2004, 04:11 PM
Registered User

1/4 scale cub - do I need 1/4 size servos?

Hi all

I've just about managed to get my hands on a 1/4 scale Bud Nosen J3 kit.

Apart from throwing out the heavy wood and lightening where possible I really wanted to know what size servos I could use?

The wing span is 108" and all up weight I have no idea but guess anywhere from 16lb to 18lb's or lighter if possible.

So should I use standard size or even bigger? I thought about using the hitech or JR wing servos for the ailerons, but really unsure.

Any help or advice would be appreciated.


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Feb 18, 2004, 04:30 PM
Registered User
pda4you's Avatar
On my 1/4 Sig I used standards for each aileron. I used a 1/4 scale for the elevator and a standard for the rudder.

This was a few years ago. Todays high touque standard servos would suffice.....

But the 1/4 scale servos are not nearly as expensive as they used to be. Hitecs are under $40 here in the states.

Feb 18, 2004, 07:13 PM
Out of Time
Here's the thing about a 1/4 scale Cub:
Even though the aircraft is big, it's still a non-airbatic plane so for scale type flying, standard servos would "technically" be OK.

But here's the BUT: All of the control surfaces on that aircraft are large and on a typical landing, the weight, momentum and intertia of, say, an elevator half, can easily cause it to whip downward when the tail drops and strip out standard duty gears. THAT'S the kind of abuse that a standard size servo won't stand up to.

I'd highly recommend that you use at LEAST 85oz servos for each aileron and elevator half, and a 150oz for the rudder by itself, and it wouldn't hurt if you exceeded those specs.

Here's the trick if you're getting into giant scale; save all your standard servos for the throttle and bomb release mechanisms.
Since you're getting into giant scale, just bite the bullet and start "supersizing" your servos too.

Feb 18, 2004, 11:44 PM
most exalted one
I would probably go with Highflight on it, but.... I'm flying a 13lb. 1/4 scale Balsa USA Cub with standard servos except for 700bb on the elevator. The way I fly it and the way it touches down I'll probably be OK. I was told by a very long-time very large scale flyer that the combo would work fine and it would be all I need. He could have sold me more expensive servos.
Feb 19, 2004, 01:30 PM
Registered User
Hi all

Thanks for the replies. I should have mentioned it will be an electric setup but I guess that doesn't really matter. I will use standard servos (ball bearings) on aileron, rudder and something bigger for the elevator.

Thank you for your help.

Feb 21, 2004, 11:43 AM
Supersonic Engineering
GordonTarling's Avatar
Madkiwi - My recently completed 1/4 scale Tiger Moth uses Hitec HS77 BB MG servos on all surfaces except rudder. One per aileron and one per elevator half - they have plenty of torque and accuracy for a slow flying model and the 'MG' bit ensures the gears won't easily strip in a heavy landing or during transportation. The rudder on the Moth uses two smaller Hitec servos, but I can't remember which ones right now and can't see the lable on them either. I strongly suggest that you split the elevator for both safety and reliability reasons.