What size rudder servo for .21 powered boat?

[dannyual767]

I'm going to power my old school Dumas SK Daddle with an OS21 RG-M engine. The hull is 36" long which is probably a little big for a 21 but this hull wasn't designed for much power or speed. Here is the link to the thread with pictures: Dumas SK Daddle thread

I was originally going to use a much bigger engine and a 1/4 scale servo. With the smaller engine and the slower speeds, would you recommend that I use the same 1/4 scale servo or could I use a standard servo h34r: ? I'm thinking I should go safe and use the big boy but what do you say?

Danny

 

[Mike Larson]

Dan... I use futaba 3305 100 + oz torque @ 6 volts, Futaba 3010, Jr 590 Z or hitec 625 mg, all are high torque in a standard size case, give or take...... 21 and 45 hydros.... your LHS should have a servo torque chart, and choice is yours.... I wouldnt carry the weight of a 1/4 scale servo around if I didnt deem it a necessity...... good luck.... Mike

 

[crrcboatz]

80 oz or so will handle that hull fine in my view.

Curt

 

[John Palica]

Contrary to common belief, I don't think you need a "large" servo to move the rudder on a .21 size boat. I run a Wild Thing with a MAC.21 engine and use a standard size servo. The boat is very responsive at full speed. As I recall, I have HiTec HS 303 standard servos on the rudder and mixture control (Mixture control was rather stiff) and an HS 81 on the throttle.

 

[Josh Stollfuss]

I use the Std. servos in my .21 mono. 48oz of torque I think. The servos have always worked fine, a .21 mono is light.

Josh-

 

[Bob Finn]

Hitec 645MG works great for me

 

[rcBPman]

The Futaba S3003 and the S3004 are great for that.

 

[dannyual767]

Okay, it sounds like my big servo will be overkill for this boat. This boat is pretty large (36") for a .21 powered boat but I don't expect it to be a speed demon. Maybe these std servos will be just fine.

Mike, those Futaba servos seem great; lots of torque in a std package. I've spent so much money on all these boats already and I'd like to use what I've already got.

 

[TomMoorehouse]

A HiTEC HS-225 mini servo works well for .21 riggers

 

[dannyual767]

I think that I'm just going to use one of my brand new Hitec std servos. I don't think that this boat will really be fast enough to need anything more. I'll figure it out during it's first outing and I'll make sure that I've got plenty of room to turn when it's at speed.

I just scanned a pair of pictures from the original Dumas instructions. Check it out.......too much excitement :

I'm sure my Irwin piped, OS .21RG-M will push this hull way faster than that !