How to Install Spare Autopilot in Parallel

[Paul L]

Originally Posted by Dockhead

Thanks. And do I really need to keep a spare course computer? Does it happen that these die underway?

I have a spare hydraulic pump (will have, after my old one gets overhauled, and the active one is only 1 1/2 years old), which seems to me the most failure-prone element.

I've had 3 Raymarine course computers flake out over 10 years. I think they are a weak link. No longer use Ray in the AP. I do have a complete Ray below deck AP wrapped in AL foil as a backup. The wiring and mounts are still in place. But I figure it would be a long, seasick 1/2 day to install offshore.

[NahanniV]

Originally Posted by Paul L

I've had 3 Raymarine course computers flake out over 10 years. I think they are a weak link. No longer use Ray in the AP. I do have a complete Ray below deck AP wrapped in AL foil as a backup. The wiring and mounts are still in place. But I figure it would be a long, seasick 1/2 day to install offshore.

I would be curious to know what model of course computer ?

I have 2 S3G units for my boat.

Thanks,
JM.

[brianb00]

Hi,

In a recent 5000 mile transpacific voyage I had a RM type 1 hydraulic pump fail 100 miles after I got back to San Francisco. The pump had driven a total of about 6000 NM, with pre event trips. The pump motor brushes wore out, the actual pump is still quite functional. I also had along the RM tiller pilot unit that comes with the X5, the linear drive. It packed it in after steering for some small fraction of the 5000 miles. A stop clip on the end for the screw drive fell off and then the steering arm came unscrewed.

My preference is similar to BOb's approach, that is independent systems in which some time is required to connect the backup.

Another approach I saw on a schumacher 52 I recently delivered, the boat had totally redundant pumps that drove a single cylinder, which was massive. The AP designer indicated that he has installed 100's of this setup on fishing boats in the Washington area and has never seen a failure. The motors and motor drive electrionics are redundant. The computer is not backed up.

An aside on ram failures: I know of 3 local boats here that have bent their RAM drive shafts due to one abuse or another while underway. Essentially in all cases, including 1 52 footer, the wheel or tiller was manually steered to the point of bending the RAM drive shaft.

[Paul L]

Originally Posted by NahanniV

I would be curious to know what model of course computer ?

I have 2 S3G units for my boat.

Thanks,
JM.

The first 2 were I believe S100s, the third an S1.
My backup now is an S3G. Primary is Furuno 700.

[twistedtree]

Has anyone tried this with a Simrad autopilot wired up with Simnet/N2K? I'm contemplating the following:

- Dual RF25 rudder indicators

- Dual AC12 computers, each driving its own steering pump

- Dual AP28 control heads, one in the pilot house and one on the fly bridge

- One satellite compass (because it's much more accurate than the RC42)

- One RC42 compass (as backup)

- Everything interconnected over N2K

- AC12s would be on lockout breakers - the kind where you can only have one on at a time - so only the active AC12 and pump would be powered on.

In theory it will all work, but I don't know how well the AP28 will handle control of two different AC12s, and how it will handle the switch from one to the other.

Also, in theory, the active autopilot should automatically switch from one RF25 to the other if the active one fails, and it should switch from the sat compass to the RC42 if that fails.

But we all know there is often a big different between theory and practice.

Has anyone tried this or anything close to it?