Autopilot failure on long passage

[ak5609]

Hello folks,

just had a discussion with a friend about the importance of our autopilot on our catamaran, and the question occurred, what to do on a transatlantic trip, singlehanded, when the autopilot stops working.

[pjShap]

At a minimum, carry a spare drive unit since that's the most common failure.

[donradcliffe]

you switch to your backup, and then use your spares to repair your primary.

[BobHorn]

When we were cruising we had two complete units. One was very basic, heading only, no interface to the chartplotter. The other was integrated with the chartplotter. The main thing was, that there were two independent actuators.

[goboatingnow]

Originally Posted by ak5609

Hello folks,



just had a discussion with a friend about the importance of our autopilot on our catamaran, and the question occurred, what to do on a transatlantic trip, singlehanded, when the autopilot stops working.

Did two trans Atlantic with Ray marine electric linear drives. Zero failures despite bringing a complete spare drive arm.

Good kit

[goboatingnow]

Originally Posted by goboatingnow

Did two trans Atlantic with Ray marine electric linear drives. Zero failures despite bringing a complete spare drive arm.

Good kit

Now I think a linear drive gearbox set might be sufficient

[ItDepends]

Our system has served the boat well for two circumnavigations, and much more general cruising, probably pushing 200K miles now. It is just that, a system. Designed for redundancy, and efficiency.

• We have a modern autopilot computer integrated into out N2K network.
• We have an older, none networked, computer with independent heading and rudder data.
• We have a Raymarine linear drive connected to the rudder post
• We have a Raymarine chain drive connected at the helm.
• Either computer can control the boat using either drive.
• We have a full spare linear drive that can be swapped out in less than 30 minutes.

In the last 50k miles we have had to swap out the linear drive twice. Raymarine rebuilt one for a reasonable charge, the other I redid myself. The ONLY complaint I have about these linear drives is that you can not buy parts for them from Raymarine. If you are remote, and you need this thing repaired, you have a real logistical challenge if sending it to an "authorized repair center" is not a viable option.

We regularly exercise all the pieces of the system in all combinations to ensure they are all functional as backup if ever needed.

On my old boat, we had a failure of a windvane that left us stranded 600 miles from shore. That boat was a monohull ketch (as is our current boat) and we get home simply by careful sailtrim that allowed us to hold a constant course to the apparent wind with any course above a broad reach. Basically we did a week with the boat literally steering herself home. My experience with catamarans is that that is a much less likely to be a viable option.

[Rustic Charm]

I’ve had this problem occur to me on two different over night solo passages of four days. Thankfully on both trips the sea state was calm enough that I could just hold up and rest. But with my large tiller it was painful after 20 or so hours.

Once I rectified the mechanism on the tiller arm, I from then on carried three electrical linier autopilots as back ups.

The idea that I could just balance the sails was a rarity and never successful in. Heavy sea state.

[SV Confianza]

Had a failure on a trip from Florida to NJ. Had to hand steer for 700 or so miles. Had to just steer to the compass.

The linear drive failed because of carbon buildup and worn motor brushes. We keep spare brushes now but haven’t sprung for redundancy.

[Emmalina]

Mine failed mid Indian ocean ! Found out a small ball in a non return valve had distorted due to heat. Took about 4 hours to make a new one from nylon. Didn't make much headway that day LOL

[RaymondR]

On my previous boat I had a Raytheon ST4000 wheelpilot. The wheel drive portion was a toy and not really suitable for serious cruising, the head a fantastic piece of gear and using it with a number of DIY wheel drivers I used it to do about 40,000 nm of coastal cruising.

The original wheel drive unit had a little 7 mm wide toothed belt which would shed teeth if overloaded, usually if I let the sails get untrimmed. It had tiny nylon gears in a planetary gearbox which wore out and were obsolete and consequently no longer available as spares.

I salvaged a gearbox from a Chinese battery screw driver and since one could buy a new tool for about $30 used up quiet a few of them. However the arrangement still had the problem with the little fragile belt so designed a replacement from an electric bike drive motor, a chain sprocket made from a piece of aluminium, a toothed belt sprocket I machined up myself, a 25 mm wide auto timing belt and a Regal Cookware frypan my wife had lumbered me with (It had a warped up bottom to which the bacon would stick and sis a hell of a better job of driving the wheel than it ever had as a cooking implement)

This was a great piece of gear, I could buy another motor for about $100, a spare belt for about $40 and nothing else ever wore out on it. The only problem I ever had with the head was a blown output transistor which I replaced for a few dollars. I still have it and intend to build another wheel drive unit for the boat I have now which is fitted with a hybrid unit.

During this years winter cruise I replaced the instrument panel at the helm position and in a silly old bugger moment dropped the Simrad AP16 head. The curse of obsolescense struck again and replacement parts are hard to find and expensive. The problem with 20-30 year old equipment is one does not know whether other failure prone parts are ready to fail so I replaced the Simrad instrument parts with parts from Coursemaster. I wanted to retain the Simrad hydraulic linear drive part because it is a serious industrial unit, readily repairable and other than the motor is probably good for another 40 years.

Having been obliged to a few days of hand steering my intention is to lay in a spare motor and a full set of seals for the Simrad hydraulic linear drive and build a 50 amp H bridge to buffer the old ST4000 head and another Raymarine computer and head that I have and I'll consider myself pretty well hand steering proof.

[Baby tug]

Somebody needs to develop an app that will run a Bluetooth switch , reversible switch that will run whatever drive that you come up with , iPad has all the electronics in it , I know it would work I heard somewhere that There is an app for an airplane auto pilot and Will fly the airplane from home don’t know if it’s true

[Jeannius]

Originally Posted by Baby tug

Somebody needs to develop an app that will run a Bluetooth switch , reversible switch that will run whatever drive that you come up with , iPad has all the electronics in it , I know it would work I heard somewhere that There is an app for an airplane auto pilot and Will fly the airplane from home don’t know if it’s true

Cheap autohelm project already exists... https://pypilot.org

[goboatingnow]

I had two wheel pilots. They suffer two big issues. Firstly resolves is slow and secondly if there is resistance they slip. They are also noisy When in operation

Ive now replaced two with conventional belowdecks linear drive using jefa linear actuators and the original ST4000 wheel pilot control heads.

[Baby tug]

Originally Posted by goboatingnow

I had two wheel pilots. They suffer two big issues. Firstly resolves is slow and secondly if there is resistance they slip. They are also noisy When in operation

Ive now replaced two with conventional belowdecks linear drive using jefa linear actuators and the original ST4000 wheel pilot control heads.

I used a Ray Marine tiller pilot to run a wheel pilot , it worked fine how many amps will it handle , I don’t think it’ll handle enough amps to run a reversing pump , I thought about using Relays , somebody might know how to wire that , I think it would work pretty good