440: Back-up Auto Pilot for Lagoon 440

[coldar1]

I have a 2006-built Lagoon 440 and am about to cross the Atlantic. Our Raymarine Autopilot has worked without a problem for the two years we have been cruising in the Med but I'm interested to hear if anyone has any experience or ideas for a simple back-up for the auto-pilot we can install in case a component of our existing auto-pilot system fails. I have conducted several test under motor and sail, and have determined we only need about 7 to 9kg of force at 1.0M from the rudder post to comfortably steer the boat. While well within the power of a Raymarine ST2000 tiller pilot that would be easy to install in the space between the engine sound-proofing cover and the engine room hatch attached to a .75M extension of the rudder head, Raymarine techs in Spain and Gibraltar tell me the ST2000 would burn out in a short time - but they don't say what a "short time" might be.
Looking for any ideas or comments that might assist. Col www.finallymydarling.com

[monte]

Col, take a look at the CPT Autopilot Inc.

[coldar1]

Thanks Monte. That will certainly do the job and is about the same price as the Raymarine tiller pilot (ST2000) that I have been told by Raymarine will NOT do the job - it might for a short period they say, but then burn out.

I just need to convince myself now that I want to spend A$2,200 plus shipping to the Canaries, and most likely have it sit in a box and never get used? It certainly is the best option I have seen and would fit easily to my helm up top on the Lagoon. Many thanks.

[Paul L]

That is a really large boat to consider using a wheel pilot. If you consider the failure modes of the first one, say 2am of day 2 of an Atlantic gale, the wheel pilot would be pretty stressed. Why not setup a second below decks pilot? You have plenty of room.

[a64pilot]

Size of the boat is irrelevant, what does matter is wheel size and force required to move the wheel.
example if you have a four ft wheel, I doubt the wheel pilot will work as it's pulley is the same size regardless of wheel size, and you have that big wheel for leverage, but the CPT wheel pilot has no increase in leverage as it's the same pulley
If you have a 2000 ton ship with a two ft wheel, the CPT can steer it easily.

If you want to know how much pressure the CPT can exert, it's close to 90 ft lbs, that is of course 90 lbs one ft out from the center of the wheel, which is 45 lbs at the rim of a two ft wheel, and 22.5 lbs at the rim of a four ft wheel.

[a64pilot]

Although as pointed out earlier, a completely identical and redundant auto pilot mounted in the other hull provides more back-up that a wheel pilot, you could break off a rudder and tear up the whole steering system, yet still have some autopilot control on the remaining rudder, CPT only covers you in the event of an autopilot failure.

I have a CPT on my mono, and so far are real happy, but the seperate, redundant autopilot in the other hull makes sense to me in a Cat, but I'm no Cat owner so may be things I don't understand

[Oliver L.]

Col,

our boat is of 2004 and we have already crossed the Atlantic with the old Raymarine. But we have heard the warnings, too, and therefore, before entering the Pacific, I am installing a new Autopilot and I will leave the old one as cold standby in case of the (unlikely) failure of the new one.

I am not doubling up the actuator - you have to draw the line somewhere, and I have not heard anything bad about failing Lecomble & Schmitt hydraulics.

Fair sailing...

Oliver

[Paul L]

Originally Posted by a64pilot

Size of the boat is irrelevant, what does matter is wheel size and force required to move the wheel.
example if you have a four ft wheel, I doubt the wheel pilot will work as it's pulley is the same size regardless of wheel size, and you have that big wheel for leverage, but the CPT wheel pilot has no increase in leverage as it's the same pulley
If you have a 2000 ton ship with a two ft wheel, the CPT can steer it easily.

If you want to know how much pressure the CPT can exert, it's close to 90 ft lbs, that is of course 90 lbs one ft out from the center of the wheel, which is 45 lbs at the rim of a two ft wheel, and 22.5 lbs at the rim of a four ft wheel.

There is no doubt that a wheel pilot can supply enough force to drive the wheel on most any reasonably sized boat. That is not what is at issue. In practice wheel pilots have had a very poor record of having long term reliability on large boats that travel extensively offshore. The OP's Lagoon 440 is a large boat. It is large in length, windage and weight at 13 tons.

[robert sailor]

I have a very good friend that sailed around the world in his 50 footer with a CPT as his one and only pilot, not something I would do but he did it.

[Paul L]

Originally Posted by robert sailor

I have a very good friend that sailed around the world in his 50 footer with a CPT as his one and only pilot, not something I would do but he did it.

There you go, proof that it can be done. How large a boat? I bet he was pretty good at CPT repair and maintenance. As you say, not something I'd do. 24/7 for a weeks in a row is pretty tough on any autopilot.

[robert sailor]

He had a little kit of spares, not sure exactly what he had. They are very simple machines, I think the drive motor is off a BMW power window and it has more than enough torque. Now with his new electronics he has about the best wheel pilot made in my opinion but it is a wheel plot.

[robert sailor]

I meant to add that when he is at boat shows his pilot is working underwater so its certainly way more than splash proof.

[a64pilot]

I thought we were talking about a back up here?
I think the CPT as a back up has a lot going for it, leave the drive bracket mounted and the wheel pulley and I can install and have operational faster than you can make a cup of coffee.
As far as having spares, thats a couple of shear pins and a belt, but if I were to use if for my primary and was doing long passages, I'd have a second CPT in a box stored in the boat, and to replace it completly, no tools and less than 5 min.
Not the best answer for everything of course, but so far I may not go to a built in autopilot, reason is the CPT works, makes no noise and pulls less energy than any other. Reason is it's rotary mechanical motion, very simple, very little mechanical losses.
Plus I can carry a complete duplicate and replace the entire thing, all electrical components is less than 5 min with no tools, no crawling in small spaces etc.

Drive motor I believe is actually a 24V Bosch truck windshield wiper motor, I don't understand how or why running a 24V motor on 12V increases the torque, but believe thats claimed.

I've built, designed and maintained rather complex machines all my life, everybody knows what KISS is, I say it differently.
"if it's simple and works, it's not stupid" and the CPT is simple and works

[Paul L]

We are talking a backup. But a backup for crossing oceans, so the passages are fairly long an dthe days are still 24 hours. The L440 is a over 2 of your boats. I would think the CPT would work pretty well on the IP 38.

[a64pilot]

I don't think you can compare the Raymarine wheel pilot to the CPT.
The Raymarine is meant to be an entry level unit for day and coastal sailing boats with little wheel effort, max tq I believe is under 30 ft lbs?
For what it's built for as long as it's used as intended, it's excelllent, especially when you consider the price.
The CPT is not an entry level autopilot, it's the one autopilot offered by I assume a small US privately owned company, it's way more powerful and hopefully more rugged than the Raymarine, and the price reflects that.

Near as I can tell my CPT only draws an amp or two when it's turning the wheel and it's draw when it's not isn't measurable unless I cut into the power wire and tie in the Fluke directly, I believe it's milliamps. I believe the hydraulic pilots draw way more than that?