Electric or Hydraulic for Backup autopilot?

[Muaddib1116]

I'm still hoping to get more answers to my question about which type of drive unit will do better with long periods of inactivity.

That being said, I have some time before I would start this project, and I might spend some time this summer playing around with what I have on the stern of my boat, and mocking up some options for a Hydrovane.

[Windpilot]

Can't help with a second drive unit, I would keep a spare of my rotary drive if that was the case.
My solar is above my servo pendulum windvane, no problem at all, keep the dinghy on deck any way unless you're harbor hoping.

[Madehn]

i have heard of a lot of people adding a CPT autopilot to have as a backup, then finding that it was so capable, quiet, and low power intensive that they began using it as their primary. I have done this and have a hydraulic unit down below to be the backup-- my thought was that if the steering cables ever had an issue, then i could steer with the hydraulic auto pilot which is attached via the RAM directly to the quuadrant of the rudder. The CPT is super simple to install and very cost effective.

[Muaddib1116]

Thanks, but I don't think I will pursue a wheel pilot. Aside from the aesthetics, and the space requirements, it doesn't give me any redundancy if the steering system fails. With a backup drive unit attached to the rudder stock directly in the lazarette, I would have a way of steering the boat if the primary steering system fails or locks up.

As far as noise, it would have to be worlds different than the raymarine wheel pilot system I grew up using, which was incredibly loud. My current autopilot makes no discernable noise, and the linear drive we installed on my family boat growing up makes almost no noise compared to a wheel pilot.

[CliveCollett]

Hi. My Hunter has a similar arrangement with the Mamba gearboxes. My AP has a Raymarine type 3 rotary unit bolted under the gearbox. This was installed by the OP when the boat was new in 2009. Prior to our purchase, the boat sat ashore for 3 years. The AP has worked flawlessly for us so far.
We are going to upgrade the electronics but the drive seems bullet proof. I have 2 wheels and could install a redundant unit under the second quadrant but will probably just carry a spare.

[Hasbeen]

I had a simple windvane system on my boat, with a very effective vane driving a separate rudder hung in a stainless bumpkin. The rudder was a close to fully balanced foil similar in shape to an Aussie 18Ft skiff center board. It could be dropped out of or reinstalled in the bumpkin in a couple of minutes. See my album for photos.



This gave me a back up rudder if ever required. It steered me for 52,000 miles of the 53,000 miles I cruised my boat. I never needed this, nor was I ever threatened by lightning. Perhaps I am lucky.

[Brendan]

Originally Posted by Muaddib1116

I have given this a lot of thought too. It would be nice to have a Hydrovane that is obviously a windvane, but also can act as a backup/emergency rudder, and the tillerpilot option is nice. The big problem is that there's a good chance that I'll add a large solar panel over my dinghy davits, so even if the dinghy is on the foredeck, it might not allow a Hydrovane.

I installed a Hydrovane on my Taswell 49 and now I'm going to have an arch with davits built, so as to be above the hydrovane with the dink behind the hydrovane. I've seen pictures of two other T-49s with both, so should be possible.

[Muaddib1116]

I've given it some thought, an I've decided not to go the Hydrovane route. While it does sort of offer a lot of things in one package (self steering, backup autopilot, emergency rudder), I feel that on a boat my size, with where I would have to install it, it will sort of do a mediocre job at all of those things, meanwhile being more expensive than a dedicated full size backup autopilot, and being a permanent fixture on the back of my already busy transom.

I will continue to pursue a full size backup autopilot, either electric or hydraulic drive in my lazarette. And in the future, I will design and have a more appropriately sized emergency rudder system built.

[SailingHarmonie]

We have exactly what you want on our boat. The system has been in place with some upgrades since the boat was built more than 25 years ago, and has over 150,000 miles in two circumnavigations.

Two autopilot computers with independent heading and rudder sensors, and two different autopilot drives.

The primary drive is a Raymarine Type 2 linear drive connected to a tiller arm. Backup drive is a Raymarine Type 2 chain drive connected to the helm. The system is set up so either computer can use either drive, and only one drive can be active at a time.

While it is true that theoretically you need to recalibrate the computer’s response to a new type of drive unit, switching the drive does not result in any noticeable change in performance for me.

We keep an additional linear drive stored off line. They are very easy to swap out underway.

With as much as we use the boat and autopilot, failures do sometimes happen. Never have we been more that a flip of a switch from being back on line.

[Muaddib1116]

Originally Posted by SailingHarmonie

We have exactly what you want on our boat. The system has been in place with some upgrades since the boat was built more than 25 years ago, and has over 150,000 miles in two circumnavigations.

Two autopilot computers with independent heading and rudder sensors, and two different autopilot drives.

The primary drive is a Raymarine Type 2 linear drive connected to a tiller arm. Backup drive is a Raymarine Type 2 chain drive connected to the helm. The system is set up so either computer can use either drive, and only one drive can be active at a time.

While it is true that theoretically you need to recalibrate the computer’s response to a new type of drive unit, switching the drive does not result in any noticeable change in performance for me.

We keep an additional linear drive stored off line. They are very easy to swap out underway.

With as much as we use the boat and autopilot, failures do sometimes happen. Never have we been more that a flip of a switch from being back on line.

Thanks! That's really close to what I have in mind. How do you manage to have both drive units attached to both ACU's and then have only one drive be able to be activated at a time? Is there some sort of 3rd party switching system?

Is your linear drive electric or hydraulic? Why did you choose that type? What type of boat do you have? Size, displacement?

Why do you use the linear drive as primary over the rotary chain drive? Have you noticed any issues with leaving one of them inactive for extended periods? for instance the spare linear drive you keep? or do you periodically switch to the other unit to exercise it?

[noelex 77]

I think electric will be better for long periods of inactivity. There are no seals to dry out and leak.

[Muaddib1116]

Originally Posted by noelex 77

I think electric will be better for long periods of inactivity. There are no seals to dry out and leak.

Thanks! I assume that the electric drives still have some sort of seals for water resistance? just not as critical/vulnerable as the seals for a hydraulic ram?

Are the electric linear drives essentially a rack and pinion setup?

[Muaddib1116]

Oh, I guess it's probably a screw, like a bench vise.

[noelex 77]

Originally Posted by Muaddib1116

Oh, I guess it's probably a screw, like a bench vise.

They vary. My old boat we had Raymarine linear drives that had a belt driven reduction followed by a screw mechanism (I think). On my new boat the Jefa drive uses a planetary gearbox.

They are not particularly well sealed against water ingress, but probably no worse than an electric anchor windlass that lives in a much wetter environment.

Periodic use helps all machinery, but the hydraulic units rely on rubber seals to contain the fluid. In theory I would expect these would be more prone to drying out and deteriorating with long periods of inactivity, but whether this theory translates to a practical difference depends on the quality of the unit, design etc.

[Muaddib1116]

Ah, thanks.

I've looked into the direct drives, by Jefa and Lewmar, and they seem to be very expensive compared to the electric and hydraulic linear drives.

As far as the linear drives, it seems like they each have their pros and cons, but probably are both perfectly suitable for what I have in mind. I'll probably go with whatever I can get the best deal on when the time comes.