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How strong a servo do I need for 1/4 scale? - 12/10/2012 7:57 PM   
Kmot



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Status: offline 		Howdy,

I have a 28% Fly Baby model that I will be assembling. I have never owned a plane this large before. I am curious to know how strong the servos should be for this size. The rudder is designed for pull-pull. Aileron's, elevators, are direct linkage.

Thanks!

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RE: How strong a servo do I need for 1/4 scale? - 12/10/2012 8:03 PM   
jetmech05


 

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Status: offline 		I'd think something like a 5646 from hitec would be good on everything

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RE: How strong a servo do I need for 1/4 scale? - 12/10/2012 10:46 PM   
dignlivn


 

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quote:

ORIGINAL: jetmech05

I'd think something like a 5646 from hitec would be good on everything





My thoughts too,+1

Bob

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RE: How strong a servo do I need for 1/4 scale? - 12/10/2012 10:50 PM   
Kmot



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Status: offline 		Thanks guys. 180 oz-in or better. Got it.

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RE: How strong a servo do I need for 1/4 scale? - 12/10/2012 11:29 PM   
Lone Star Charles


 

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Status: offline 		Try this site - http://www.mnbigbirds.com/Servo%20Torque%20Caculator.htm

I've never tried it, but kept it around just in case I ever needed it.

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 12:02 AM   
ckreef


 

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quote:

ORIGINAL: Lone Star Charles

Try this site - http://www.mnbigbirds.com/Servo%20Torque%20Caculator.htm

I've never tried it, but kept it around just in case I ever needed it.




Thats a kewl calculator. Not sure how accurate or usefull but I did bookmark that link for further use/study.



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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 12:04 AM  1 votes
j.duncker



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Status: offline 		Unless you overpowered it std servos would fly this just fine if the model was flown in a scale like manner Futaba 3003 or similar maybe run on 6 volts but even on 4.8 they will do the job.

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 12:09 PM   
jetmech05


 

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Status: offline 		Typo I meant 5645...look at it this way we usually go up in suze with the next airplane...you can't have too big a servo so the bigger now the less you gotta buy later

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 12:45 PM   
sensei



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Status: offline 		When I was at the last TOC in 2002 many of the 40% competition aircraft were running servos like JR 8411s and I think they have something like 155 ozs. of torque in memory serves me. Anyway you be the judge.

Bob

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 1:55 PM   
TFF


 

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Status: offline 		It cant hurt to have some powerful servos in a big plane. Needed in a 3D plane, nice in a floater. The real Flybaby is not a big plane or fast ; it could fly on some of the servos we put in models. Probably anything over 70 oz per surface would do the job in that kind of plane. I would say 100+ oz for peace of mind. To put it in perspective, when the BUSA 1/3 FlyBaby came out, the industry best was 50 oz.

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 4:57 PM   
OldScaleGuy



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Status: offline 		The old rule of thumb is one ounce of torque for every square inch of surface area. That is still a good rule for this type of plane.

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 6:21 PM   
Kmot



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Status: offline 		Thanks everyone, for your input.

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RE: How strong a servo do I need for 1/4 scale? - 12/11/2012 7:31 PM   
Rodney



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Status: offline 		Many years back I flew very large planes with the standard servo of the day, around 30 in.oz. You do this by using boost tabs on the surfaces ( I used them on all three, rudder, elevator and ailerons) with no problems. You can also use aerodynamic balanced surfaces to great effect. If rumour has it correct, Burt Rutan flew an experiment where he used the 30 in.oz servo to fly the full scale VariEzz just to prove it could be done. He did this by having the servo drive the boost tab on free floating ailerons. Sure, powerfull servos are a solution but it can be done without them.

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RE: How strong a servo do I need for 1/4 scale? - 12/12/2012 2:36 AM   
sensei



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Status: offline 		Boost tabs are indeed very effective, there are actually two types. The first is servo driven; the servo drives the hinged boost tab and the boost tab drives the control surface, the faster the aircraft goes the more effective the boost tab is. The second type is the servo drives the control surface while the hinged boost tab on the control surface is tied to the wing through the use of a link and control horn, as you deflect lets say an aileron up the boost tab deflects down, as the the aircraft moves forward the tab is now assisting in lowering the amount of torque needed to deflect and sustain the control surface through the forces generated by airspeed. It does work very good but most wouldn't try this on a bet...

Bob

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