Tunnel Hull Steering Servo Question

[Josh Stollfuss]

What size servo is recommended for a tunnel hull running either a 7.5cc or 11cc Motor? Would a standard size, digital, high torque, metal gear Servo hold up? Or am I kidding myself? Should I just put in a single 1/4 scale or double 1/4 scale. I'm sure there is many different views on this question, but I appreciate any and all input..

Thanks again for the great site, and all the help!

Josh-

 

[Jerry Dunlap]

Josh,

I have installed the Hobbico CS-80 Giant Scale 2BB servo in 7.5/11cc tunnel with good results. The Tower Hobbies price is $29.99 and on a 6.0v battery pack it puts out 334 oz. in. of torque. It's a little larger than a standard 1/4 scale, but will fit in most radio boxes for 7.5/11cc tunnels.

JD

 

[Duck899]

Josh.....I have used the 1/4 scale futaba and Hitecs in the past but with the technology available today, I think you can get away with the standard size high output torque servos like the futaba S9405. It will do 100 oz/in and should do the job. There are alot of standard size servos that should do the trick....although the standard size servos will be more expensive....

 

[Eddy de Vries]

On my modified glassfiber DPI F1 with home made Zenoah outboard I use a single Volz Alu-Star digital 220 with good results (so far).

This servo has 220 N.cm = 311 oz.in of torque and has the standard servo dimensions (see: www.volz-servos.com).

It is pretty expensive (approx EUR 220), but I think it is worth the money.

To prove the above see my boat in action: http://p086.ezboard.com/fjimsrcboatdockfrm...tart=21&stop=30

Mr. Dunlap,

Since you seem to be the leading model boat tunnel guru, I would like to get in touch with you. This because the DPI was only meant for testing and I would like to discuss about the new (maybe final) boat I would like to design in the near future.

I you are interrested I think shortest communication lines would be through my e-m@il acount: [email protected]

Hope to hear from you.

Best regards,

Eddy de Vries

 

[Josh Stollfuss]

I have a Hi-Tech 5645MG digital servo which has 168oz torque at 6v. Would this work?

josh-

 

[Tunnelbill]

I run 2 1/4 scale servos in my 7.5 mod boats. You can run smaller servos and you can run only 1 but you will get Good at changing Gear Sets..... If you blow a 7.5 off and it lands on the motor and it will, the gears are GONE....

 

[lohring]

The only reason to use larger (1/4 scale) servos is that the gears are larger. As was pointed out, it's not about the servo torque, it's about gear strength. When a boat flips and the engine gets slammed around, you want the servo arm to break before the gears. Use a plastic arm and the spline will strip before the gears. I've found the Hitec 705MG to hold up well, but I'm sure there are others that will work as well.

Lohring Miller

 

[[email protected]]

TunnelBill is right, two 1/4 scale servos is the way to go. The Hi-Tec one's work great and are cheap. Plus if your running and one strips out the other will work by itself and you don't run the risk of trashing your boat.

 

[Bob Kensill]

If money is no object,try the new Hitec HSR-5995TG servo. It is standard size with 333oz/in torque and .15 sec/60 degrees. It has ball bearings and titanium gears. The street price is about $115.00.

 

[[email protected]]

Krpnova,

That's not a digital servo, right?

 

[Bob Kensill]

It is a digital servo.

 

[Rudy Formanek]

I've been running the Hitec 5735 digital big servo(metal output gear). Glad to be rid of the dual servo hassles of "Y" servo wire connector and trying to keep the two servos from fighting each other. I've used a heavy plastic horn and haven't stripped or broken an arm yet. I feel the boat drives better than it did before, but that is pretty subjective. I will not go back to two high power standard size servos. Rudy

 

[Bob Kensill]

I use a heavy duty,metal gear servo for steering. If I flip real bad,the worse that happens is a stripped servo horn. They are cheap and easy to replace. A 75mph dump with a 7.5 tunnel is hard on everything.

 

[duc]

I use the Robbe Futaba 3101. It was the first servo I ever bought and I'm still using it. So that is about 9 years of very bad treatment. Including setting the Dutch record for ' parking your tunnel on the beach as far from the water as possible (26 metres h34r: ), 3 times totally destroy the hull accidents, soaked it with water, etc. Did not need to change parts or serviced it ever.

 

[Lake S.P.O.R.T.]

You guys that have switched to using the single big servo, are you having to run another battery just to power that servo? Or, are you running a big mah pack to run everything?

Mark

 

[Rudy Formanek]

You guys that have switched to using the single big servo, are you having to run another battery just to power that servo? Or, are you running a big mah pack to run everything?
  Mark

91045[/snapback]

​

I'm running a 5 cell 2300 MAN NIMH AA pack. Get cheap cells at Fry's at a $10.00 for 10 cells on sale.

 

[Jerry Dunlap]

I run 5 cell packs in almost all my tunnel boats.

JD

 

[Josh Stollfuss]

Well It sounds like I can run a standard size servo, but I will expect to replace either the servo horns or the gears if I flip it.. I'll give it a try, if I need to move up to a 1/4 scale servo I will, I have pleanty of room in the radio box..

Thanks for all the input!

Josh-