Dual Pilot Design?

[capitangiorg]

On my previous boat I found a chain rotary drive autopilot. It was very old but it worked flawlessly.
We use to cross the Atlantic twice por year and I felt uncomfortable knowing that a "simple" steering cable failure will lead to no steering wheel and no autopilot! A dangerous situation especially when you are very close to shore and at least uncomfortable when you have to sail 1500 NM to the closest harbour. So I installed a second and more powerful idraulic unit with a ram attached to the rudder quadrant. I used most of the time the older unit cause it drained less energy and it was quiter than the idraulic one. When things were rough I used the newer one cause it was more powerful and had quicker response.
I had no foolproof way to exclude the use of both autopilot at the same time. During five years it happened a couple of time that I swithced on the two autopilots togheter, they figheted each other for a couple of seconds and I turned one off, that's it.

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[estarzinger]

I'v been aboard a couple 'open 60's' with dual autopilots - and there was nothing sophisticated or complex - just two autopilots installed seperately (on separate breakers), but with nothing to prevent the skipper from accidentally running both at once - except that you would have to flip both breakers on and then engage both control heads - so need a 'double accident'.

But I honestly don't usually consider these Open boats to necessarily be best practice with it comes to long term durability and wear issues - because remember, their longest race (the vendee) is now only 80-90 days and then the boats tend to get pretty much stripped down and rebuilt.

The real trade-off here is between ease and speed of getting going after something fails vs preserving the spare parts from wear and corrosion. The racers will of course lean heavily toward the first, while it is (arguably) rather less important for cruisers.

I cruised with Steve Dashew when he was shaking down his power boat, and I could be wrong, but I think he had only one fully installed autopilot. He had had tremendous reliability from his WH units. And I do not remember seeing dual pilot systems (but it was some time ago). We do know a NZ built aluminum dashew design with dual pilots and they had the 1 -2 switch and were one of the boats that alternated between the two systems (they figured they were wearing their 'spare' hydraulic seals anyway, so might as well run the system)

[capitangiorg]

I agree with estarzinger not all the racer's choice are the most suitable for cruisers.
IMHO a good autopilot well installed and maintained on a regular basis could last many years.
If the boat is dry as it should be in the rudder bay, a cylinder properly built doesn't corrode. If your pump/drive and CPU are in a dry places don't corrode either. Find a dry place for controll unit/display it is not so easy, but it can be done.
I choose to install the second unit instead of keep it as a spare cause the first one was a rotary drive type, so as i said in the previous post, if one steering cable went borke I lost steerage for autopilot as weel steering wheel. Furthermore, due to the poor accessibility of the rudder area, I frighten only at the idea to find myself in a gale working around the rudder quadrant. But if you can install easily the autopilot, even under sail, it can be a wise idea to keep it as a spare in a sesled bag!
Andrea

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[UNCIVILIZED]

Originally Posted by capitangiorg

On my previous boat I found a chain rotary drive autopilot. It was very old but it worked flawlessly.
We use to cross the Atlantic twice por year and I felt uncomfortable knowing that a "simple" steering cable failure will lead to no steering wheel and no autopilot! A dangerous situation especially when you are very close to shore and at least uncomfortable when you have to sail 1500 NM to the closest harbour. So I installed a second and more powerful idraulic unit with a ram attached to the rudder quadrant.

Did you not have a setup for an emergency tiller? Most boats do, & typically at most, there's a small plate covering the top of the rudder post. Which, after the plate's removed, you simply put the tiller into a socket in the rudder post's head.
And on better designed boats, the emergency tiller is actually a full sized tiller. So that there's far less strain on the helmsman.

Also, if you don't mind the cost. It's possible to set up a pedestal, so that there are 2 sets of chain/cables, going to 2 seperate quadrants on the rudder.

That, & on some systems there are other options besides metal chains, & cables. Like belt drives in lieu of chains. And Vectran or Spectra instead of cables.
Many of the latter can be retrofitted to boats which have cables, after a thorough deburring of all metal components. Something which should be done with some regularity, regardless of what materials comprise one's steering system..

Plus, if chafe on parts of the steering system is a true worry, you can making inspecting things daily (or more often), part of ship's routine. Especially both during, & after periods of heavy weather. Much as one does at least daily to the rig, especially on long passages. Given that things can wear pretty quickly when underway.

And on racing boats at least, it's also common to send crew aloft once or twice a day, in order to give everything a good inspection. A practice that would be wise on any fully crewed boat, in order to head off any rigging problems, when they're still fixable.

[capitangiorg]

Yes we did have an emergency tiller and I checked all the steerings before any serious sail. The system was well engineered infact in more than 100000 miles I didn't have any issue.
Cause we sailed a lot of miles just me and my wife and the boat was 65', we use to leave all the steering corvee to the autopilot. For that reason I choose to have a backup ready to use.

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[Dockhead]

Originally Posted by estarzinger

I suppose if you wanted to do this . . . the simple way would be just to put a 1 - 2 switch with no 'dual' position (like one of these https://www.bluesea.com/products/110...witch_with_AFD) to power both autopilots. That way, only one can be on at a time and they could never 'fight' even accidentally. You would still be wearing the seals on both rams and double 'drag' on the steering feel, and exposing the spare electronics to corrosion, but it is there mounted for immediate use. We only know two boats that did this and I believe both use an 'alternating schedule' for the autopilots - pilot A this week and pilot B next week, rather than holding one in complete reserve. They did this (I guess) so they 'know' both work.

That sounds reasonable.

I guess if you're sure that without power, the bypass valve will always be open -- and I think that's how they work -- then there's no problem other than a bit of extra drag, which I don't think would be noticeable. In fact, might even give a bit of beneficial extra damping in the steering.

I would be inclined to install it that way just because I would trust a fully commissioned and operational unit, regularly used, more than one stored as spares. I've had a few cases of spares which didn't work when needed, either because it was the wrong part despite the label, or because they deteriorated in storage. Based on several disappointing incidents with stored spares, I am still working on spares storage techniques. I now have a vacuum packing device on board. I will start inserting desiccant packets or maybe even try to find some dry nitrogen (since vacuum packing does not get all the air out of the package).


I would not use an "alternating schedule"; I would make one of the pilots the main one and put the wear and tear on that, and make the other one the reserve one, using it only enough to prevent deterioration and be sure that it's working.

In my experience, the rams are the last thing to wear out, so I don't think I'd be all that worried about wear and tear on the ram seals. Plus you could keep seals on board -- they're not that hard to rebuild yourself and I suppose it could be done at sea. In fact, the seals might actually hold up better, being "worked", rather than sitting around immobile.

In my experience, most problems with pilots are bad wiring, bad fixings either of the rams or at the quadrant, and bad hydraulic pumps. I guess hydraulic leaks must be not uncommon, but I've never had one; nor have I ever had a ram failure. The pumps -- all of them made by HyPro AFAIK, for pleasure vessels -- are not really marine hardware, and corrode, and die eventually. I seem to get about 10 years out of them, but with lots of miles on an extended cruise I guess that could turn out to be less.

Everything connected with steering will be massively overbuilt on the new boat. I particularly admire Dashew's rudders; I'll probably have the NA imitate one of those. By the way, I am not entirely dissatisfied with the steering on my present boat, actually. The rudder bearings are enormous; look like something stolen off a tugboat, and are supported in a massive webbed structure tied in to the main boat structure. Great attention to structure seems to be characteristic of Bill Dixon's work, and I appreciate this more and more. Lacking is a cofferdam and watertight bulkhead aft, however, which I will definitely have on the new boat.

[monte]

I don't think it was mentioned earlier in this thread, but the CPT wheel pilot may be a good option for most ap failure situations. Some benefits over an installed pilot include ease of installation, price, resale value, option to remove when vessel sold, low power consumption and low noise.
http://www.cptautopilot.com

[Sandero]

If one is going for back up. I kinda like Dockhead's approach... Install, use, prove and them remove and properly stow... then install the second and go with that until failure then install the original proven rig.

Sounds terribly expensive... and very prudent... if you are heading off into the wild blue yonder.

Then again... worst case is you are forced to hand steer until you can get to some place and order and wait for the replacements...

[Dockhead]

Originally Posted by Sandero

. . .
Then again... worst case is you are forced to hand steer until you can get to some place and order and wait for the replacements...

Losing automatic steering can be a very serious and possibly fatal emergency offshore and short handed, depending on the circumstances.

The pilot is like another crewman, or a couple of extra crewmen, in terms of the work load which it takes. In a storm with crew resources stretched to the max, the pilot can literally save your life.

I consider automatic steering to be a critical life safety issue, offshore and short handed. Different if you are within a day of a port or well crewed.

But I expect to be as little as double handed and far from civilization, so risk of loss of automatic steering is not acceptable. I will go to some great lengths to ensure that this does not happen.


Thanks to all the helpful input in this thread (thanks a lot, everyone!), I think I have a pretty good vision now of how to do it now. I think the design brief looks like this:


Two very robustly mounted and oversized hydraulic rams. The mounting is critically important -- I've seen a lot of pilot failures caused by failure of the mounting either at the boat end or at the quadrant. I don't know why some boat designers don't pay attention to this.

Each ram driven by its own separate hydraulic pump, also oversized (and I'm looking for more rugged and corrosion-resistant alternatives to the ubiquitous Hypro ones). Hydraulic pumps mounted in a dry and protected place, not just in the bottom of the lazarette. I think there should be a small compartment for them just below deck level.

One pilot designated as primary, and networked, with the pilot electronics powered from the main 12v electronics and radios power supply (two 6 volt golf cart batteries as buffer and backup, supplied from the main DC system via a 24v to 12v DC-DC charger, with separate AC charger). So probably a Simrad or Furuno (depending on main electronics).

The other pilot non-networked and totally freestanding, also with its own rudder reference and heading sensor. Maybe a WH pilot like Dashew uses, but using identical hydraulic pump and ram to primary pilot in the interests of spares interchangeability. The backup pilot will have computer enclosed in a Faraday cage with switches to allow storing it completely disconnected from rest of the boat's ground and electrical systems. I reckon the control head will be reasonably survivable if completely disconnected too, right?

Concerning power supply: The 12v electronics battery bank will be mounted just below deck level together with the engine and generator starting batteries in a special compartment designed to resist flooding in case of some disaster. In case of some emergency which kills the house batteries/main power supply, possibly to power electronics and radios from either main engine or generator start battery using jumper cables. Main engine will have have optional heavy duty primary alternator in addition to secondary school bus alternator. Engine and generator start batteries can be combined and tapped for emergency 24v supply.


Single switchover for the 24v power supply to the bypass valves and hydraulic pumps, which will prevent both pilots from being powered simultaneously.


In spares: One complete hydraulic pump, one complete bypass valve, miscellaneous hydraulic lines and fittings, one rebuild kit for a hydraulic ram, one complete pilot computer for primary pilot, one spare rudder reference for each pilot, one spare NMEA0183 heading sensor, all vacuum packed and stored in a metal box.



Yes, I realize this will be expensive. How expensive? Maybe $10,000 more than a standard pilot setup? I am willing to spend that much on a few crucial systems like these.

An alternative would be a wind vane, but AFAIK they don't work on vessels this size (about 65' LOA and 25 tonnes), unfortunately.

[estarzinger]

Originally Posted by Dockhead

In my experience, most problems with pilots are bad wiring, bad fixings either of the rams or at the quadrant, and bad hydraulic pumps.

I am sure it is brand and boat/installation dependent.

On Hawk we had two fluxgate compass failures, one control head failure, one main black box board failure (all B&G). We had ram (robertson) seals leak but that unit was superbly designed and easy to top up in place until you could get to changing it or its seals. On Silk we had repeated control head and black box failures - Silk was a much 'wetter' boat than hawk (autohelm and then Robertson)

We never had a wiring failure. No mounting issues, And we never had an outright ram failure (just leaking).

[estarzinger]

Originally Posted by Dockhead

In my experience, most problems with pilots are bad wiring, bad fixings either of the rams or at the quadrant, and bad hydraulic pumps.

I am sure it is brand and boat/installation dependent.

On Hawk we had two fluxgate compass failures, one control head failure, one main black box board failure (all B&G). We had ram (robertson) seals leak but that unit was superbly designed and easy to top up in place until you could get to changing it or its seals. On Silk we had repeated control head and black box failures - (autohelm and then Robertson) but silk was so long ago it is probably not as relevant.

We never had a wiring failure. No mounting issues, And we never had an outright ram failure (just leaking).

Edit: scratch that - I did have one 'wiring failure' on my very last trip to greenland - an original 16 year old wire connection had either corroded or come very slightly loose. I disconnected the wire to trouble shoot the components, found nothing wrong, put the wires back together, and it was all working again - so I went back and snipped a cm off the wires to get clean(er) wire, stripped them, cleaned the terminal block and reattached the wires and called it good.

I never liked the 'pro' installs - where the wires were so prettily installed and cut to just exactly the right length. I liked to have about 50cm loops of 'extra wire on both ends - so you can pull the wire and equipment out to access/work on it, and can move it around if you need to later when installing other gear, and you can shorten to get clean when you need to.

[Dockhead]

Originally Posted by estarzinger

I am sure it is brand and boat/installation dependent.

On Hawk we had two fluxgate compass failures, one control head failure, one main black box board failure (all B&G). We had ram (robertson) seals leak but that unit was superbly designed and easy to top up in place until you could get to changing it or its seals. On Silk we had repeated control head and black box failures - (autohelm and then Robertson) but silk was so long ago it is probably not as relevant.

We never had a wiring failure. No mounting issues, And we never had an outright ram failure (just leaking).

Edit: scratch that - I did have one 'wiring failure' on my very last trip to greenland - an original 16 year old wire connection had either corroded or come very slightly loose. I disconnected the wire to trouble shoot the components, found nothing wrong, put the wires back together, and it was all working again - so I went back and snipped a cm off the wires to get clean(er) wire, stripped them, cleaned the terminal block and reattached the wires and called it good.

Thanks - very useful.

A networked pilot which can be controlled by any MFD will be more robust as it doesn't depend on any single control device. But black box failure? That's alarming. So I guess having a spare is a good idea. Was your black box getting exposed to spray or moisture?

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[svadagio]

I have 2 pilots complete with drives etc. The rams connect to the tiller one on each side. Two pumps. Two complete electronics packages including compass, rudder feed back and control heads. I have solenoid valves in each to connect or disconnect the hydraulics as needed. No manuel valves. I have a switch box with all the switches needed to change from one pilot to the other or run either electronics package with either hydraulic drive. The positive power goes through the box so you can not run both pilots at once. The switch box is easy to make and eliminates a mistake at a time that you may not be making the best decisions.
Bob

[estarzinger]

Originally Posted by Dockhead

Thanks - very useful.

A networked pilot which can be controlled by any MFD will be more robust as it doesn't depend on any single control device. But black box failure? That's alarming. So I guess having a spare is a good idea. Was your black box getting exposed to spray or moisture?

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I had a handheld remote in addition to control head, which could continue to control the autopilot after the control head quit, but with less functionality (compass steering only, not wind or NEMA, for instance). When single handing I used the handheld 95% of the time. When Beth was on board we used the control head more.

The Robertson black box on Silk was mounted in a 'moist' place - not ideal. The B&G box on Hawk was in a very dry location (I do learn ) - but we did cruise to places where the 'environment' cycled quite hard - in chile the air would be cold and damp one moment and then we fire up the diesel heater and it would be warm and dry.

BTW on compasses - today - I would try to get two different solid state devices - a solid state inertial compass and a (3 antenna) gps compass - rather than the typical mechanical fluxgate.

[Paul L]

Dockhead
I don't think putting switches on the wires on the backup controller inside the Faraday cage is going to accomplish protection. You would need to disconnect the wires and not have them hanging out of the cage.