Rudders

Don Case · Post by **Don Case** » 03 Oct 2008, 19:35

I have been surfing old posts and notice a few that seem to indicate that maybe rudders and rudder servos should stronger than I thought. Are CF rudders and high torgue servos really necessary or is it just a bigger is better thing? What kind of torque would be about right?
Thanks
Don

Hiljoball · Post by **Hiljoball** » 04 Oct 2008, 06:02

Hi Don,

I don't know how low you could go with torque.

I have used a standard analog servo
Hitec HS-425BB DELUXE rated at 46oz

and a high speed digital servo (as opposed to a high torque)
Hitec HS-5625MG - DIGITAL rated at 110oz

in my IOMs they both worked fine. They never showed any sign of being under powered.

Bruce Andersen · Post by **Bruce Andersen** » 04 Oct 2008, 09:24

most all of the available servos produce enough torque - the important points are how well they return to dead center and weight (if your boat's heavy). The digital servos are more expensive but claim more accurate return to dead center.

Don Case · Post by **Don Case** » 04 Oct 2008, 17:58

Bruce Andersen wrote:most all of the available servos produce enough torque - the important points are how well they return to dead center and weight (if your boat's heavy). The digital servos are more expensive but claim more accurate return to dead center.

It never occurred to me that this might be an issue. I guess a person should build a foot long servo arm to test it. I know how much hassle a loose rudder arm joint can be and this would be the same. Is it possible that a dirty pot in the servo would affect the accuracy of the return?
Thanks
Don

Barry Fox CAN262 · Post by **Barry Fox CAN262** » 04 Oct 2008, 18:54

Either of John's choices are just fine. And Bruce's advice is spot on.

With analog servos you can see that they don't always (seldom) return to zero so you get into having to do a little bit of trimming sometimes from tack to tack.

The digital ones are generally much more powerful (not that big of a deal), more expensive (pretty much a one time expense so in the end not a big deal) and remove a variable.

On the other hand, I get beat all the time by folks with analog servos on their rudders so it is a sailing skills thing again in teh end.

Don Case · Post by **Don Case** » 09 Oct 2008, 20:37

Would a Hitec HS85mg mini servo be suitable for a rudder servo? It has metal gears and roughly the same torque as a standard servo. I would have to check the return to center. I am trying to crowd everything into a 4.5 in jar lid and any room would be welcome. I have heard that metal gears have some slop which might affect the return to center. Any thoughts?
Thanks
Don

RoyL · Post by **RoyL** » 09 Oct 2008, 21:05

Rather than try and cram everything together, why not put the rudder servo by itself, centered behind the main sheet post? What is done, you cut an opening in the deck for the installation and removal of this servo, mount the servo, and then cover the hole with a piece of sticky back plastic. You can take the cover off to replace the servo, otherwise it stays in place, and you have easy access whenever necessary and doesn't cram everything in under a pot lid.

Bruce Andersen · Post by **Bruce Andersen** » 10 Oct 2008, 07:14

Agree with Roy: no sense in mounting the servo in the radio pot. Just mount it up under the deck (away from bilge water) and it will be fine, barring a major disaster. Servos occasionally fail, so don't mount it where major surgery is necessary to swap it out between heats. I've had no problems with metal gear servos and they usually have ball bearing races inasmuch as they are designed for high force applications.

Don Case · Post by **Don Case** » 10 Oct 2008, 17:04

Thanks for the thoughts
I have a phobia about deck patches. On one of my first trips to watch some model boats I watched a brand new IOM disappear in about a second when a deck patch peeled off. I can still hear the skipper swearing. I have not trusted them since. Maybe a second, smaller lid for either the battery or rudder servo would be the way to go even though it would clutter the deck a bit. Meanwhile, I guess the lack of responses means that no one has tried one of these mini servos?
Don

Barry Fox CAN262 · Post by **Barry Fox CAN262** » 10 Oct 2008, 19:32

I know that by specs they should be fine. One boat here has one in it for the rudder and it sometimes acts like it doesn't have enough oomph to make the boat tack. I can't think of one good reason why but that is how it acts.

I have used the digital aileron, in wing servos for the rudder and not had ony real problems with them but they have the same torque and are only a couple of grams lighter so that doesn't help.

I have never seen properly applied patches just come off. The sign vinyl is a bit fragile as I have seen another boat's jib boom counter weight poke through one and rip it open. I have also managed to drip a small pair of pliers from about spreader height and they went right on through.

But the good dacron stuff is awfully darn bullet proof if it is stuck down properly. None of them stick well to a wet deck so you have to be careful if you have to peel one on a wet day.

Bruce Andersen · Post by **Bruce Andersen** » 11 Oct 2008, 08:39

I've used the JR mini servos in a heavy boat to make minimum weight, but in a boat that needs corrector weights anyhow, what's the point?

Don Case · Post by **Don Case** » 11 Oct 2008, 15:54

Bruce Andersen wrote:I've used the JR mini servos in a heavy boat to make minimum weight, but in a boat that needs corrector weights anyhow, what's the point?

Room, I'm using a 4.5in jar lid for a hatch and I want to get at everything through it. If I could find a 5in lid it would be golden.
Thanks
Don