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Old 25-09-2018, 05:43   #1
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Redundant autopilot, best option?

I am preparing for an Atlantic crossing in the spring and I’m considering options for a backup to my current Raymarine auto pilot. The boat is a Lagoon 450. Options I’ve seen suggested for a backup or alternate auto steering system are:

1) A second complete autopilot system on standby that is the same as the existing one. In my case that would mean a Raymarine system.
Pros: Shared parts
Cons: Second system may be prone to the same failure as the first.

2) A wind vane steering system.
Pros: Less prone to electrical or mechanical breakdown.
Cons: Wind steering may not work well on a catamaran in some wind/sea conditions.

3) An attachable autopilot system like a CPT (CPT Autopilot Inc.)
Pros: Self contained and completely separate from existing system.
Con: You either have to mount it ahead of time and deal with being it at your helm unused, or take the risk of having to mount it after the primary has failed.

Are there other other options I’m not considering? I would appreciate any input on the topic.
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Old 25-09-2018, 08:00   #2
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Re: Redundant autopilot, best option?

A fourth option is to source some used AP gear. There are a fair amount of Ray linear drives and AP computers with control heads that are a generation old.
You could mount and test it. Then remove the electronic portion, cpu and control head, and place them in a makeshift Faraday cage to protect from lightning. Lightning is one of the main killers of A ps once in the tropics.
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Old 25-09-2018, 08:10   #3
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Re: Redundant autopilot, best option?

I've seen Cats with a 2nd system like you described in option one however, they went with a different manufacture (Garmin). Not sure if that was because it was easier to set up that way or what but having a 2nd system is a smart idea.
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Old 25-09-2018, 08:26   #4
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Re: Redundant autopilot, best option?

I think your CPT option is the best one. You can install it before you leave or not. That's the option we went with when we crossed the Atlantic and initially it was for back up only but it worked so damn good, was super quiet and barely used any power that we ended using it for almost the whole trip. It's very 3asy to install and remove plus these have an excellent following so its easy to sell them when you wish. Cheers, R
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Old 25-09-2018, 08:50   #5
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Re: Redundant autopilot, best option?

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I think your CPT option is the best one. You can install it before you leave or not. That's the option we went with when we crossed the Atlantic and initially it was for back up only but it worked so damn good, was super quiet and barely used any power that we ended using it for almost the whole trip. It's very 3asy to install and remove plus these have an excellent following so its easy to sell them when you wish. Cheers, R


Go for a dual Raymarine system. Try to use the same model of course computer. That gives you redundancy with “spare parts”

Raymarine is the most common autopilot. Easy to find spare parts if needed. Check out Ebay if you have an older system. Have made 3 Transatlantic with Raymarine pilots. No problem what so ever. Soon time for the fourth.

Most autopilot problems are caused by poor installations. Check steering system and installation.
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Old 25-09-2018, 10:30   #6
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Re: Redundant autopilot, best option?

Thanks for all the great input.
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Old 25-09-2018, 12:20   #7
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Redundant autopilot, best option?

On my Mono I have the CPT with the plan of having a second in a plastic box as a spare.
They will sell you one with just the two boxes as a spare, cause you don’t need all the other stuff and it saves a few bucks.

However if I had a Cat with two rudders, I feel that I would want one autopilot on each rudder, that way no matter what broke, I’d likely still have one rudder that could steer.
I love my CPT and with my rack and pinion steering, I don’t see how a break can occur between the wheel and the rudder but cables and or hydraulic systems, I can easily see how a break can occur between the wheel and the rudder. I’d want a direct connection to the rudder to steer.
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Old 25-09-2018, 12:42   #8
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Re: Redundant autopilot, best option?

[QUOTE=a64pilot;.
I love my CPT and with my rack and pinion steering, I don’t see how a break can occur between the wheel and the rudder but cables and or hydraulic systems, I can easily see how a break can occur between the wheel and the rudder. I’d want a direct connection to the rudder to steer.[/QUOTE]

What kind of planes did you fly?
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Old 25-09-2018, 13:56   #9
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Re: Redundant autopilot, best option?

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...with my rack and pinion steering, I don’t see how a break can occur between the wheel and the rudder
You can have wear on the system and/or broken teeth are a potential failure mode.

Our Amel had a dual rack and pinion arrangement driving redundant push pull cables to the rudder. Great system, but we did have a tooth break on one of the racks. The system was 'sticky' but still worked as the one rack with a broken tooth would sometimes get jammed temporarily.

Luckily we had dual autopilots (one a rotary drive connected to the wheel and one a linear drive connected directly to the rudder arm). I could still steer with the wheel, but it was much easier on the steering system to use the linear drive. So I spent the next few weeks mainly driving around the reefs of Fiji with the linear autopilot drive to reduce further damage. It definitely sold me on the concept of redundancy and having a direct connection from at least one of the autopilot drives to the rudder!

On as side note: By the time I got to Savusavu, there was a new rack and pinion assembly (for about 1/3 the cost I was expecting - that rarely seems to happen with boat equipement!) from Amel waiting for me. Not bad support from a manufacturer for a 20+ year old boat ;-)
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Old 26-09-2018, 08:49   #10
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Re: Redundant autopilot, best option?

My old Autohelm 4000 died and couldn’t be repaired, so be careful if you’re considering used gear. It might not be fixable due to parts unavailability, obsolete boards, etc. I replaced the 4000 with a Raymarine, but seriously considered the CPT. But it was something about the exposed drive belt and gearing that finally turned me off (with my luck something would get stuck in the gears or the belt at absolutely the wrong time).
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Old 26-09-2018, 10:25   #11
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Re: Redundant autopilot, best option?

I have mounted, fixed or upgraded, AP systems on at least a dozen of boats (I think likely about 20 boats or so). Some of them sailed their rtw by now. Some of them racing boats that rely on AP while the boat sails under kite and her skipper is sound asleep in her bunk.



IMHO the best & safest attitude is to have two, identical, fitted, in-field switchable, AP units. This includes e.g. two mast wind sensors.



Second best is having a second identical unit, complete, new, sealed, boxed, onboard.


Get spares for things that are known to fail at regular intervals. Like those flimsy reference arms or those silly outdated Ray compass pucks. Old technology but many boats still have them.



A well sized (='"oversized") well fitted and tested AP is not something that fails all that often. Where I did see horror things happen were mostly boats with factory fitted units .... (good for a short stunt in the Med ...). Not bad stuff, just sized as per expected average use.



Test your unit out and out & make sure you can adjust it well. Avoid overpowering the boat. Make sure your batteries are sound and full ...


I hope this helps a bit.


Do try to get all jobs and tests done before you hit offshore. Some places along the route have very good shops BUT they may suffer from technicians mostly able / willing to swap things rather than pinpoint the problem and find a working and reliable solution.


Cheers,
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Old 26-09-2018, 10:37   #12
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Re: Redundant autopilot, best option?

Here's another option. Pypilot, using a raspberry pi, OpenCPN and the correct HATs and controllers.

I have a modern Raymarine system, and I'm considering a Pypilot as a backup to replace an old Cetrek system.

IMO the most likely method of failure in a modern pilot will be overheating the hydraulic pump, so carry a back up of that too (if your steering is hydraulic).
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Old 26-09-2018, 10:49   #13
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Re: Redundant autopilot, best option?

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Originally Posted by mikedefieslife View Post
Here's another option. Pypilot, using a raspberry pi, OpenCPN and the correct HATs and controllers.

I have a modern Raymarine system, and I'm considering a Pypilot as a backup to replace an old Cetrek system.

IMO the most likely method of failure in a modern pilot will be overheating the hydraulic pump, so carry a back up of that too (if your steering is hydraulic).
We carried a CPT as a spare to our linear drive Raymarine on the last boat, but fitted a windvane as back-up to the new boats B&G hydraulic system. The windvane is a fine back-up, but I still want a second autopilot option and will this time try the Pypilot. Why not? The cost is so low and with a larger H-bridge can drive the largest drives available. So it's $200 for the Pypilot with H-bridge and a few hundred for a used linear drive..... very good deal!

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Old 26-09-2018, 11:01   #14
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Re: Redundant autopilot, best option?

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What kind of planes did you fly?


Helicopters and Crop dusters, and of course a personal airplane, a Maule and I kept the little Cessna 140 that is airworthy but about 95% restored, I just have interior to do.
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Old 26-09-2018, 11:07   #15
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Redundant autopilot, best option?

Quote:
Originally Posted by Hobie_ind View Post
You can have wear on the system and/or broken teeth are a potential failure mode.

Our Amel had a dual rack and pinion arrangement driving redundant push pull cables to the rudder. Great system, but we did have a tooth break on one of the racks. The system was 'sticky' but still worked as the one rack with a broken tooth would sometimes get jammed temporarily.

Luckily we had dual autopilots (one a rotary drive connected to the wheel and one a linear drive connected directly to the rudder arm). I could still steer with the wheel, but it was much easier on the steering system to use the linear drive. So I spent the next few weeks mainly driving around the reefs of Fiji with the linear autopilot drive to reduce further damage. It definitely sold me on the concept of redundancy and having a direct connection from at least one of the autopilot drives to the rudder!

On as side note: By the time I got to Savusavu, there was a new rack and pinion assembly (for about 1/3 the cost I was expecting - that rarely seems to happen with boat equipement!) from Amel waiting for me. Not bad support from a manufacturer for a 20+ year old boat ;-)


It could happen, anything is possible, but the size of the rack and pinion are such that a human can’t come close to generate the forces it would require to bust it, and I’m pretty sure say that if I backed into a rock or something, the rudder would break long before either the rack or the pinion.
There is always a weak link in anything. In an IP I feel certain it’s the rudder itself, the framework inside of the rudder that is welded to the shaft that if it breaks, the rudder can slip on the shaft, is I think the weak link in an older IP like mine that is 31 yrs old.
There is a hole in the upper aft section of the rudder above waterline that you can run a line through and steer the rudder if that happens, or that is the theory anyway, I don’t know if it’s actually ever been used.

I carry a gale rider for emergency steering if I lose the rudder, not sure it would work with a rudder jammed hard over though, not sure anything would.
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