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Old 07-03-2014, 11:42   #1
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Request advice on Autopilot spares

I have a Raymarine S2G autopilot. This has a 7000 control head and a type 2 linear drive.

I am preparing for long time cruising and blue water, I have a spare linear drive, but am not sure what else \I should have.

Any suggestions (preferably backed up by experience!)
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Old 07-03-2014, 12:25   #2
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Re: Request advice on Autopilot spares

I've never had to replace my drive. But had to replace my computer, which required a new control head. But I knew the computer was going bad for 1.5 years before I replaced it and even then it was still mostly working so it wasn't exactly an emergency.

Modern APs are pretty proven and I'm not sure it is worth it to carry a spare.
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Old 07-03-2014, 12:40   #3
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Re: Request advice on Autopilot spares

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Originally Posted by sailorboy1 View Post
I've never had to replace my drive. But .............
Linear drive was starting to fail, so I bought a new one, and then had Raymarine repair the old one as a spare. It is the only part that has a real mechanical task, so I was happy to have a spare.
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Old 07-03-2014, 13:00   #4
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Re: Request advice on Autopilot spares

We've had a Autohelm/Raymarine autopilot system since early spring 1995. The parts that have failed in the last 20 years and over 3500 hours of usage are:

- Original Type 1 Linear Drive plastic sun gear - that failure was due to operator error when we had to suddenly bail out of a very dangerous Western Baja California anchorage - we set the autopilot to take us to safety while we raised the main. We forgot to release the manual wheel lock and the clutch on the Linear Drive did not release as it should when too much torque is applied. I replaced the plastic gears with newer bronze gears in Nov 2001 and have put another 2500 hours on them.

I installed a new Type II 30 amp motor in the Drive unit in spring 2013 at which time the gears, clutch, belt, and Type I motor all looked to be in perfect condition with about 3300 hours on them.

- Internal wire connection in bulkhead mounted fluxgate compass. This was an easy repair made in a beautiful and very remote tropical anchorage. At that time the compass was over 9-years old and had about 2000 hours on it.

- External wire connection for bulkhead fluxgate compass. This was a 12V connection I had made when installing the compass.

- Diode D-19 on the Type 100 course computer failed after 19 years and 3200 hours. This was a known problem with the course computer and was an easy repair IF you can repair component level stuff on a printed circuit board.

We carried NO spares for the Autohelm while cruising but we do have a Sailomat windvane that works like a dream and a Autohelm Type 1 tiller pilot that can connect to the windvane and steer the boat when there is no wind.
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Old 07-03-2014, 13:12   #5
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Re: Request advice on Autopilot spares

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Originally Posted by TacomaSailor View Post
We've had a Autohelm/Raymarine autopilot system since early spring 1995. ...............We carried NO spares for the Autohelm while cruising ..........
I do not have a wind vane. So recognise that there is more wear on my system. Thanks for telling me your experience.
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Old 07-03-2014, 14:28   #6
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Re: Request advice on Autopilot spares

my 7000 series control head failed in the Caribbean and needed a new cable as well. The Raymarine tech in St. Maarten who troubleshot it said to me that it is very rare for the computers to go bad. Far more common for the drives to fail or the control heads. Also (as in my case) cables and connections can go bad after a while in a salt environment
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Old 07-03-2014, 18:03   #7
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Request advice on Autopilot spares

Quote:
Originally Posted by TacomaSailor View Post
?......



We carried NO spares for the Autohelm while cruising but we do have a Sailomat windvane that works like a dream and a Autohelm Type 1 tiller pilot that can connect to the windvane and steer the boat when there is no wind.


I guffawed at that , it's like saying you only have one backhoe, and no spare except for two tracked excavators.

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Old 07-03-2014, 18:41   #8
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Re: Request advice on Autopilot spares

Quote:
Originally Posted by TacomaSailor View Post
We forgot to release the manual wheel lock and the clutch on the Linear Drive did not release as it should when too much torque is applied.
AFAIK, there is no clutch overload disengage on that drive. My manual specifically mentions damage to the unit or steering gear if the AP is engaged and the steering system is not free or someone tries to work against the AP.

To the OP:
Your #1 concern in heading out should be the strength and robustness of your drive mount. This is probably the biggest problem people face when using their AP full time in heavy conditions. A lot of people underestimate the forces on the drive mounting.

Your #2 concern should be having sufficient power and regeneration for operating an electronic AP 24/7.

#3 would be lightning. Now we are into low probability territory, but lightning taking out the electronics is probably more common than the electronics simply "failing". This one is hard to plan for or accommodate. You could install a separate AP on your other rudder and keep it totally unwired and offline until it is necessary.

Last is failure of the AP itself. If you have a newish AP, have installed it using good practices and have a strong mount and connections for it, the actual failure rate of these is pretty low. Much, much lower than that which all the windvane people are going to chime in here with their stories of people they know with AP's instead of vanes coming to grief.

On the other hand, what "spares" are you expecting to not have known in advance about? These systems consist of a computer, a compass, a control head, a drive unit and a rudder reference unit. I guess you could count random wires and cables in there, but those pretty much cover all the parts you could possibly consider having spares for.

The compass is kind of the odd spare out here. Most do not carry another one, but most AP's can be set to wind angle or GPS COG as an alternative to a compass bearing if something goes wrong with that. However, if you currently only have a basic fluxgate, adding a good rate compass to your system not only gives you a backup (that would be your original fluxgate), it also improves your chartplotter, radar and other equipment.

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Old 07-03-2014, 18:49   #9
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Request advice on Autopilot spares

I'd offer a slightly different perspective

Drive mounts need to be well built, but not massive, especially if the autopilot arm is driving the steering quadrant directly , which is now very common. If the drive jams and the mount doesn't fail, you can burst up the quadrant, that is NOT something you want to fix at sea. ( don't ask me how I know )

I would say you will have electronic failures long before lightening strikes. In the past with Raymarine it was always the course computer output transistors that failed but that seems to be fixed on later models.

My advice , whatever spare parts you bring , you'll never need. !!! , I had the same raymarine linear drive on two altantic crossings, I had a spare drive, it was still in the wrapping three years later, everything else of course failed !!!!

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Old 07-03-2014, 19:11   #10
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Re: Request advice on Autopilot spares

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Originally Posted by goboatingnow View Post
Drive mounts need to be well built, but not massive, especially if the autopilot arm is driving the steering quadrant directly , which is now very common. If the drive jams and the mount doesn't fail, you can burst up the quadrant, that is NOT something you want to fix at sea. ( don't ask me how I know )
Well, yes, but how do you propose filleting that very fine line between the mount failing and the quadrant failing? Personally, I would favor the lower probability of the quadrant somehow jamming over the higher probability of the mount breaking. But then we use a tiller arm to connect our pilot to the rudder, which I think is a better method than directly to the quadrant.

Quote:
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I would say you will have electronic failures long before lightening strikes. In the past with Raymarine it was always the course computer output transistors that failed but that seems to be fixed on later models.
Well, uhhh, ummm, errr, ahem (hint, I bolded the problem for you)…

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Old 07-03-2014, 19:33   #11
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Re: Request advice on Autopilot spares

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Originally Posted by colemj View Post
........ most AP's can be set to wind angle or GPS COG as an alternative to a compass bearing if something goes wrong with that. ...........
Mark
This is not true for the autopilots I have used (Raymarine S3G and Comnav). Those autopilots are always steering to the compass; In wind or GPS mode the course to seer is being updated based on wind or GPS input. I think this is probably the normal implementation.

A spare fluxgate compass could possibly wear out even in storage on a moving boat since the internal gimbaled part is connected to the stationary part by flexible wires that can eventually fail. A solid state compass might be better.
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Old 07-03-2014, 19:35   #12
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Re: Request advice on Autopilot spares

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This is not true for the autopilots I have used (Raymarine S3G and Comnav). Those autopilots are always steering to the compass; In wind or GPS mode the course to seer is being updated based on wind or GPS input. I think this is probably the normal implementation.



A spare fluxgate compass could possibly wear out even in storage on a moving boat since the internal gimbaled part is connected to the stationary part by flexible wires that can eventually fail. A solid state compass might be better.

A flux gate compass is solid state. It may be gimballed or not. Good ones usually are.

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Old 07-03-2014, 19:43   #13
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Re: Request advice on Autopilot spares

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This is not true for the autopilots I have used (Raymarine S3G and Comnav).
Well, uhhh, ummm, errr, ahem (hint, I bolded the problem for you)…

BTW, I'm pretty sure the RM S3G can steer to COG and wind. If it doesn't, well, I bolded the problem for you…

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Old 07-03-2014, 19:45   #14
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Re: Request advice on Autopilot spares

Quote:
Originally Posted by colemj View Post
Well, uhhh, ummm, errr, ahem (hint, I bolded the problem for you)…



BTW, I'm pretty sure the RM S3G can steer to COG and wind. If it doesn't, well, I bolded the problem for you…



Mark

No autopilot can function without a compass. It cannot use cog without a compass feed some can steer to wind without a compass, but less and less or the newer mideks can operate without a rate stabilised compass.

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Old 07-03-2014, 19:49   #15
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Re: Request advice on Autopilot spares

Quote:
Originally Posted by goboatingnow View Post
...whatever spare parts you bring , you'll never need...
You really nailed it with this! And I honor it by quoting.

Another thing to think about is to provide a completely redundant system that will do the same thing, a backup, like carrying a tiller or wheel auto pilot, to be used if/when the main system cannot be repaired.

Terra Nova came to me with a wheel pilot. While I'd love to one day have a modern, sophisticated, built-in a/p, I instead chose an auxiliary-rudder wind vane. This will give me an entirely independent steering system, should any part of the keel-hung rudder/wheel steering system fail catastrophically.
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