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Old 14-01-2023, 07:13   #1
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Below Decks Autopilot selection - Input Requested

Hello CF:
We've just purchased a new to us Shannon 38 cutter and are planning our systems & upgrades. She has typical Edson pedestal cable and chain steering and a full keel with attached rudder and has been seasonally used with a "light" electronics package that does not include an autopilot. So, a fresh start and we don't have to undo any subpar installations.
The use profile is just the wife and I (some occasional guests) for weekends and, for the next couple of years, one to two week vacations around southern New England and Eastern Long Island. After that, maybe more extended trips.

The boat is listed at 18,500 lbs. So, with a cruising allowance of 20%, that puts displacement at 22,200 lbs. For one instance that puts us within, but at the upper limit of, the Raymarine EV200 package actuator's stated limit of 24,000lbs. I have no particular preference for one manufacturer or another at this point and don't mind sourcing an actuator separately from the control and sensor package (some call it a "corepack", right?)

This question goes specifically to selection of a below-decks autopilot actuator unit. I'd like the input and experiences of any regarding sizing, reliability, noise, ease of operation and maintenance & service.
I've found several types: linear electric, electro-hydraulic, etc, by a few manufacturers. Raymarine, Octopus, Pelagic, Simrad Robertson, etc.

Might it be worthwhile (several more thousand "boat units") to upgrade to the next level? If so, what, in your experience, would be a best in class actuator and why?
Input from other Shannon 38 owners (or similar boats) especially sought.
I'll be designing and executing the installation as well. Experience here also would be valuable.
Thanks in advance to all and Happy New Year CF!
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Old 14-01-2023, 07:35   #2
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Re: Below Decks Autopilot selection - Input Requested

There are many things to consider, and I'll start this by saying I am not a fan of Raymarine electronics, so this recommendation does not come from any kind of brand loyalty. BUT the Raymarine linear drive is an awesome piece of kit. In operation it is as close to silent as I can imagine. Our is mounted under the berth my partner uses when we are underway, and she sleeps without noticing it.

With a large "barndoor" rudder you are going to need a bit more torque to move it around that the typical boat with a balanced spade rudder, but...

Our boat is larger than yours, but we are about as close to the size limit of a Type 2 drive as you are to a Type 1, (about 10% less than max specified) and we also have a barndoor rudder on a skeg. Our Raymarine Type 2 linear Drive has served our boat very well for many 10's of thousands of ocean miles. I very much doubt you would find value in upsizing from the recommended unit. If the install works for you, I am pretty sure you'd be very happy with the performance.

I have used hydraulic systems by Octopus, and found them to be functional and reliable, but very loud. Tolerable around a sleeping berth only if the pump is mounted remotely in an isolated engine room.
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Old 14-01-2023, 07:44   #3
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Re: Below Decks Autopilot selection - Input Requested

Congrats on your Shannon, Captain.

As she has a "barn door" rudder, loads on the AP drive unit will tend to be higher than on a more balanced rudder. I would go up a size if you have room.

Also, the most reliable appear to be the hydraulic pump & ram units, while the electric drives draw a little less power. Given your rudder, I would get a hydraulic drive, Lecomble & Schmidt makes excellent ones.

Don't leave off the rudder angle indicator.

Most any electronic controller will work, though some are better than others.

Don't underestimate the loads involved when you design the mounting arrangement.

Probably none of this is what you want to hear as it is more money and time.

Finally, you might think about the size of your battery bank and charging systems.
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Old 14-01-2023, 09:07   #4
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Re: Below Decks Autopilot selection - Input Requested

Beautiful boat that should be an offshore pleasure with a reliable autopilot.
Definitely go with a Type 2 drive unit and appropriate core pack to control it. Your boat is at the edge with a type 1 drive unit which of course won't make any difference until you are in a tough spot and absolutely need it to work.
I have used a Type 2 rotary drive for 30+ years and many thousands of offshore miles. I recommend it for a couple of reasons:
1) It can be a more compact installation. We looked at a linear drive but could not make it fit.
2) The Raymarine Type 2 Rotary drive is significantly stronger than the Raymarine Type 2 linear drive. Not sure why but I'm sure one of the forum engineers can explain it. There is table on the Raymarine tech site ( if you can find it ) that compares the types of drive units by strength and power draw.

If you decide to go with a rotary drive unit it will likely be a Raymarine Type 2 even if the corepak is a Garmin since they don't make one.

Sailing Harmonie suggests that Raymarine can be hard to love and I agree but their Type 2 Rotary drive is very robust.
good luck
Tom
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Old 14-01-2023, 09:30   #5
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Re: Below Decks Autopilot selection - Input Requested

As others have said loads on a sailboat rudder are substantial. Particularly when sailing with a weather helm. Another consideration for selecting vendor is integration with your chart plotter and displays. When I upgraded my system several years ago, a chart plotter that included autopilot control was not much more $ than an autopilot control head. And display modules also included autopilot control as backup. New autopilot will be NMEA 2000. So a new backbone is required.
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Old 14-01-2023, 10:00   #6
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Re: Below Decks Autopilot selection - Input Requested

The up thread recommendation for a rotary drive dictates using the boat's chain and cable steering mechanism so there's no safety redundancy. Nice drive unit but wouldn't be my choice.

The Raymarine linear drives are very reliable and quiet (which I highly value) and can be driven by most other brands of control units.

I also like and prefer the Jefa drive units and the linear unit would satisfy your requirements.

Without a balanced rudder I'd lean toward a Type 2 but you could confirm that this season before buying and installing any unit by seeing how well she balances her sail plan in snotty weather.

Good luck with the new boat!
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Old 14-01-2023, 18:33   #7
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Re: Below Decks Autopilot selection - Input Requested

Thanks to you who took the time to share your experiences and opinions. I know there are no hard and fasts here, but some comparable experiences do help the decision process.
I like this, Kenbo:
"Without a balanced rudder I'd lean toward a Type 2 but you could confirm that this season before buying and installing any unit by seeing how well she balances her sail plan in snotty weather."


And this, Harmonie:
"BUT the Raymarine linear drive is an awesome piece of kit. In operation it is as close to silent as I can imagine. Our is mounted under the berth my partner uses when we are underway, and she sleeps without noticing it."
The Raymarine linear drive appears to be a purpose built proprietary Raymarine unit - meaning that it doesn't seem to be offered by other manufacturers. A bit unique and I'm glad you reported good experience with it.
How is the backdrive effort? Is it noticeable while hand steering when on standby?


Another question for the forum:
Have you used the Edson tiller arm (the drive slots inside the tiller) or a more conventional tiller arm i.e. like the Buck-Alqonquin (we'll call it B/A) "flat" style?
It appears that the Edson arm applies the force via double shear through the pin/bolt rather than the single shear of the B/A style.
I suspect that I'm going to end up doing the calculation, but.....
Which did you select and why? Is it working satisfactorily?


Thanks to all for the good wishes on our new adventure. We've been hunting for a while and finally found her. First things first, though. New cabin cushions!
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Old 14-01-2023, 18:44   #8
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Re: Below Decks Autopilot selection - Input Requested

The Jefa autopilot drives are also worth looking at. They are available in much more powerful models than typical electric drives, without the drawbacks of hydraulic drives.

Unfortunately, I have found the warranty support appalling even with a brand new unit, but they are usually well made so the chance of needing help is not high.
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Old 14-01-2023, 18:46   #9
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Re: Below Decks Autopilot selection - Input Requested

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Originally Posted by noelex 77 View Post
The Jefa autopilot drives are also worth looking at. They are available in much more powerful models than typical electric drives, without the drawbacks of hydraulic drives.

Unfortunately, I have found the warranty support appalling even with a brand new unit, but they are usually well made so the chance of needing help is not high.

Well, that's an interesting looking bit of machinery. Guessing planetary gear drive...
Off to do some more research.
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Old 14-01-2023, 18:59   #10
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Re: Below Decks Autopilot selection - Input Requested

Quote:
Originally Posted by Mariner84 View Post
And this, Harmonie:
"BUT the Raymarine linear drive is an awesome piece of kit. In operation it is as close to silent as I can imagine. Our is mounted under the berth my partner uses when we are underway, and she sleeps without noticing it."
The Raymarine linear drive appears to be a purpose built proprietary Raymarine unit - meaning that it doesn't seem to be offered by other manufacturers. A bit unique and I'm glad you reported good experience with it.
How is the backdrive effort? Is it noticeable while hand steering when on standby?
The Raymarine is (of course) proprietary to Raymarine, but it is easily connected to other companies drive computers, simple wiring. (With a caveat, for 24V systems, see below...)

The backdrive resistance is close to zero. With the clutch deactivated, the resistance to movement is essentially zero.

Now, the one catch...

All drive computers (other than Raymarine) assume that whatever voltage you are using for the autopilot drive motor it is the same as the autopilot clutch. Except Raymarine. In the Raymarine world, even if the DRIVE motor is 24v the clutch is 12V. If you have a 24V boat, this is an easy fix, as long as you know it is there.
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Old 14-01-2023, 19:04   #11
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Re: Below Decks Autopilot selection - Input Requested

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Originally Posted by Mariner84 View Post
Well, that's an interesting looking bit of machinery. Guessing planetary gear drive...
Yes, the larger units such as the one pictured (which is suitable for boats up to 70 feet) use a planetary gearbox.

It is worthwhile over specifying the drive unit for offshore conditions.
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Old 14-01-2023, 19:26   #12
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Re: Below Decks Autopilot selection - Input Requested

Another vote for Lecomble and Schmidt as the drive pack.

I did a lot of research on this when I was looking for my 42,000lb steel cutter. At the time, the vast majority of the ‘Around Alone’ fleet were using L&S actuator sets (pump and cylinder). For those guys, a failure is usually catastrophic and always race ending.

I spoke with the excellent folks at PYI Inc who are the NA dealers, and have a wonderfully reliable system installed now. It takes a feed from any black box brain, so you can mix and match whatever electronics you like with it. I’ve been running a Garmin GHP system that has been pretty good.

But I really love my L&S. extremely solid piece of kit. And the support when selecting and installing was superb.
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Old 15-01-2023, 22:48   #13
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Re: Below Decks Autopilot selection - Input Requested

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Originally Posted by noelex 77 View Post
Yes, the larger units such as the one pictured (which is suitable for boats up to 70 feet) use a planetary gearbox.

It is worthwhile over specifying the drive unit for offshore conditions.
I installed an Simrad DD15 a couple of years ago, which is a smaller version of this. Uses a planetary drive system with an electromagnetic clutch. When it is not engaged, I don't notice any drag on the tiller. Nice piece of kit. I was seriously constrained on the available space, and a linear drive unit would have required a lot more work to fit.
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Old 15-01-2023, 23:12   #14
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Re: Below Decks Autopilot selection - Input Requested

Octopus Electro-Hydraulic Linear Drives... I have two of these. Try to find how many people have issues with them on Forums or YouTube-- it will be long time hunting...

Not to poo-poo Brands-- but Simrad & Raymarine unit failures at sea are plentiful-- YouTube's back this as fact. Granted -- their pricepiint is cheaper than Octopus-- but you get what you pay for-- and Octopus has rebuild kits for sale at reasonable prices-- ram rebuilds, as well as other components. Eg. One thing fails-- its not a whole throw baby out with the bath water...

Fair winds and gather facts-- not only opinions...
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Old 16-01-2023, 00:59   #15
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Re: Below Decks Autopilot selection - Input Requested

M84

"We learn by doing" , A very painful and expensive way to go with Raymarine Autopilots. We are in year 8 with our highly modified blue water cruiser.

Linear vs rotary drive - Rotary drives live a charmed life due to the fact they have an approx 12 to 1 gear ratio between the internal belt drive AND the diameter of the radius of the rudder post mounted sector. Bad news is most failures of chain/wire rope wheel steer systems occur on this load path.

Linear drives do have much higher working loads. In our installation, the Type 2s acts upon a separate arm attached to the rudder stock in the vicinity of the upper bearing. It's length approximates the radius of the sector. This configuration allows the autopilot to function as an emergency tiller in the event of the loss of the wheel steering mechanisms.

The 2019 refit replaced the ancient fluxgate compass and CCU with the Garmin Airmar 9 axis heading transducer and a G-wind electric chicken.

So 2022, sees us heading southwest to Hawaii utilizing the wind hold feature in 5 meter following seas, steady 25 kn AWS.........36 hours and the 2s lost the PLASTIC planetary gears. Game over. Arriving back at the mainland we found Raymarine has an upgrade kit with brass/metallic gear assemblies.

For parts support, Low power consumption, and noise, we are staying with the 2S. Consider seriously using the mounting location separated from chain/wire rope wheel assembly. The Airmar heading transducer comes from Garmin's Avionics unit so processor speeds handle 200 knots, 8 knots needs to be on power saving mode. BTW, Odyssey weighs in at 30,000 with a fin keel and skeg hung rudder.Click image for larger version

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