Otto Died, Need a New Autopilot

[capngeo]

My 30 year old autopilot died, and I need a new one.....

I only need something that will maintain a heading; doesn't need to follow waypoints, doesn't need to compensate for wind changes.. just follow the last heading I gave it.

The current linear actuator works fine, as does the rudder angle indicator; the brain box and user interfaces are finished. (Raymarine)

What is the general consensus of the forum as to brand reliability, and ease of use (less is more... keep it simple, etc)

[colemj]

You will most likely need to replace the rudder indicator as the old ones were pretty much dedicated to specific units. Unless the current Raymarine ones still read your old output. Your linear drive should be OK with any new AP, although at 30 years age, you may want to reconsider that.

First thing you will learn as you delve into this is that "less is more…keep it simple" is more of a function of how you use it than of how it comes. You really can't find many single function ones anymore, but you don't have to use all of the functionality of the new ones or connect them to everything either. I doubt your old one was that limited.

You can, of course, still get those units that only allow you to turn a manual compass dial on a WWII Heathkit control box and have it roughly keep that heading. However, you will miss the most important advance in autopilots - a rate compass and advanced adaptive steering software.

You will not believe the difference that makes. I can't state it enough, so I will leave it there. Ignore this and you have made a big mistake.

All of them work well and are similarly reliable. Since you are only interested in pressing the "Auto" and "Off" buttons, they all are equally easy to use. If you decide to venture further into their functionality, they are all equally easy. And they all cost about the same.

Personally (from going through deciding on a new AP), I think the Simrad offers more functionality and performance than the others in this range. However, for your requirements, none of those functions would be apparent, and the performance of only following a compass course would be like anyone else's.

Just curious - why are you limiting yourself so much when using an AP? Wouldn't it be to your advantage if it automatically corrected for current set? Or sailed to a specific wind angle if you wanted to do some experiments with sail set or tweeking things?

Here is where the CPT, WH and Alpha people jump in. Maybe these are the systems you are looking for after all.

Mark

[skipmac]

For a basic, no frills, no interface, proven AP I think the Alpha and the WH both have a good reputation.

[skipmac]

Originally Posted by colemj

You will most likely need to replace the rudder indicator as the old ones were pretty much dedicated to specific units. Unless the current Raymarine ones still read your old output. Your linear drive should be OK with any new AP, although at 30 years age, you may want to reconsider that.

First thing you will learn as you delve into this is that "less is more…keep it simple" is more of a function of how you use it than of how it comes. You really can't find many single function ones anymore, but you don't have to use all of the functionality of the new ones or connect them to everything either. I doubt your old one was that limited.

You can, of course, still get those units that only allow you to turn a manual compass dial on a WWII Heathkit control box and have it roughly keep that heading. However, you will miss the most important advance in autopilots - a rate compass and advanced adaptive steering software.

You will not believe the difference that makes. I can't state it enough, so I will leave it there. Ignore this and you have made a big mistake.

All of them work well and are similarly reliable. Since you are only interested in pressing the "Auto" and "Off" buttons, they all are equally easy to use. If you decide to venture further into their functionality, they are all equally easy. And they all cost about the same.

Personally (from going through deciding on a new AP), I think the Simrad offers more functionality and performance than the others in this range. However, for your requirements, none of those functions would be apparent, and the performance of only following a compass course would be like anyone else's.

Just curious - why are you limiting yourself so much when using an AP? Wouldn't it be to your advantage if it automatically corrected for current set? Or sailed to a specific wind angle if you wanted to do some experiments with sail set or tweeking things?

Here is where the CPT, WH and Alpha people jump in. Maybe these are the systems you are looking for after all.

Mark

Second all this. I'm leaning towards a Simrad when I replace. One thing I have not been able to find is relative power draw from one brand to another. Years ago I read a comparison and the Alpha used significantly less than other models at the time. One reason if I recall, the Alpha didn't use power to engage the clutch when activated.

[DeepFrz]

Check out W-H Autopilots and AutoNav. They may have something you are looking for.

[onestepcsy37]

i've been using a cpt autopilot for ten years now and am delighted with it. it's very simple and rugged. you can't interface your gps to it but i wouldn't want to anyway. and if you decide to change boats it's easy to move it from boat to boat. if you check around you'll find many happy users. their website is -

www.cptautopilot.com

[donradcliffe]

The Alpha brain sucks, and the CPT is not strong enough to drive the boat in heavy weather--I've had them both. If you want to keep your drive, you can choose between Simrad, Raymarine, or Garmin brains. Ten years ago I would have picked Simrad/Robertson, but now that they are Simrad/Navico/B&G, I might lean towards Garmin--Raymarine still spends more on advertising than engineering.

[colemj]

Originally Posted by skipmac

One thing I have not been able to find is relative power draw from one brand to another. Years ago I read a comparison and the Alpha used significantly less than other models at the time. One reason if I recall, the Alpha didn't use power to engage the clutch when activated.

Power draw is dependent on the type and size of actuator used, the type of steering system the boat has, the inherent steering properties of the boat and the sea state. So it is almost impossible to compare power draw across boats, but given a single boat in the same sea state, the power draw will be proportional to that needed to work the actuator. This will be pretty close for most actuators, but probably in the order of electromechanical<integral hydraulic pump (non-continuous)<hydraulic ram.

Yes, the Alpha does not use an electrical clutch, so it saves 0.5-1A on that. It uses a mechanical lock that one engages by turning the wheel until a slot lines up with a locking pin and pulling a string to slide the pin in the lock. To disengage, one pulls the string so that the pin pulls out of the slot. A real PITA in my opinion, but others seem to prefer this for some reason over simply pushing "auto" and having it just work.

Mark

[skipmac]

Originally Posted by colemj

Power draw is dependent on the type and size of actuator used, the type of steering system the boat has, the inherent steering properties of the boat and the sea state. So it is almost impossible to compare power draw across boats, but given a single boat in the same sea state, the power draw will be proportional to that needed to work the actuator. This will be pretty close for most actuators, but probably in the order of electromechanical<integral hydraulic pump (non-continuous)<hydraulic ram.

Well yes, that's exactly the point. With so many variables it is very difficult to get any valid comparison between units. You could take several identical boats, install different APs in each and send them out sailing together. Or you could take one boat and install several APs on one boat and switch from one to the other. Or take data from dozens and dozens of boats so you have a large enough data sample to give statistically significant results. Bottom line I don't see any of these happening so the best I can do is ask for subjective opinions from knowledgeable boaters based on experience with different APs and boats over time.

Originally Posted by colemj

Yes, the Alpha does not use an electrical clutch, so it saves 0.5-1A on that. It uses a mechanical lock that one engages by turning the wheel until a slot lines up with a locking pin and pulling a string to slide the pin in the lock. To disengage, one pulls the string so that the pin pulls out of the slot. A real PITA in my opinion, but others seem to prefer this for some reason over simply pushing "auto" and having it just work.

Yes I am familiar with the Alpha lock system but never had any hands on experience with it. Saving 0.5-1.0 amps on a long passage would be pretty significant but I have also heard that getting the slot lined up to engage the AP can be a pain. To save +/- 20 amp hours/day might be worth the occasional PITA.

The Alpha seems to be very well liked by most (not all) owners, generally reported to be very reliable and a power miser BUT

- I have seen complaints from a couple of owners that had a lot of trouble with repairs and support. The maker seemed very reluctant to support owners in remote locations that wanted to trouble shoot and repair the AP on site and not ship it back to the states at high cost and long, long wait time. I have seen a couple of reports of multiple back and fourth shipments of a component trying to get a proper repair.
- It is a small company, more or less a one man band and I have to wonder what will happen when he decides to retire.
- Definitely unsophisticated and a few owners complain that in their installation the Alpha did not hold a very straight course, basically s-curved across the ocean. Others praise the course holding so hard to say on this.

[skipmac]

Originally Posted by donradcliffe

The Alpha brain sucks, and the CPT is not strong enough to drive the boat in heavy weather--I've had them both. If you want to keep your drive, you can choose between Simrad, Raymarine, or Garmin brains. Ten years ago I would have picked Simrad/Robertson, but now that they are Simrad/Navico/B&G, I might lean towards Garmin--Raymarine still spends more on advertising than engineering.

I have heard another CPT owner also say it doesn't have enough power. Worked OK in mild conditions but when the wind and seas picked up the CPT couldn't do the job. To be fair he has a fairly heavy boat with a large, unbalanced rudder that does take a bit of work.

I would be very interested in finding out more about the Garmin. I do like their gear in general. However the Garmin AP is relatively new on the market and I have not seen any reports from serious, long term cruisers on how it does. Maybe you can be the guinea pig and tell the rest of us how it goes.

[colemj]

Originally Posted by skipmac

Well yes, that's exactly the point. With so many variables it is very difficult to get any valid comparison between units. You could take several identical boats, install different APs in each and send them out sailing together. Or you could take one boat and install several APs on one boat and switch from one to the other. Or take data from dozens and dozens of boats so you have a large enough data sample to give statistically significant results. Bottom line I don't see any of these happening so the best I can do is ask for subjective opinions from knowledgeable boaters based on experience with different APs and boats over time.

I wasn't very clear on that. What I meant to get across was that the basic brains of all of the autopilots are just computers that all use nominally the same amount of power. If there is a difference, it is very small - for example, our Simrad computer and control head together draws only 0.5A. So the only real power difference (leaving out the actual boat and its characteristics) is due to the drive unit itself.

Therefore, you can pretty much rank the relative power usage of all autopilots by ranking the average power consumption data published for whatever drive unit you choose.

For example, the Raymarine electromechanical linear drives draw on average 1.5-3A for the small one and 4-6A for the large one. The Simrad hydraulic linear drives draw on average 3.5-10A for the small one and 5-16A for the large one. The Raymarine reversing hydraulic pump draws 9A for the small one and up to 34A for the largest one (there are several sizes in this series).

We have owned the electromechanical and hydraulic linear drives above on the same boat, and I can state that those power consumption figures are accurate. In average conditions, the large electromechanical used 3-5A and the large hydraulic linear used 7-13A.

Other manufacturer's electromechanical, hydraulic linear and hydraulic pump drives draw pretty close to the same power to operate. So you can rank any system by the drive you choose to put on it.

Note that I got the ranking of the hydraulic drive types backward in my previous post.

Mark

[colemj]

Originally Posted by skipmac

I would be very interested in finding out more about the Garmin. I do like their gear in general. However the Garmin AP is relatively new on the market and I have not seen any reports from serious, long term cruisers on how it does. Maybe you can be the guinea pig and tell the rest of us how it goes.

Garmin uses a JEFA electromechanical drive. This drive uses an interesting motor design that is quite frugal with power consumption. However, I think they only manufacture one size if it, and your boat may be pushing that.

Mark

[River Cruiser]

A a/p is also on my list of additions in the near future. Si-Tex is at the top my short list, I have their MDS radar and a couple of displays that are durable, work very well are simple enough that a very low tech person like myself can mount, wire and use. I like the OP only need a system that will keep a heading that I set, not a unit that will follow waypoints from a plotter or do fishing patterns the Si-Tex units hit these requirements at a modest price and have great customer support to boot. I will never buy Garmin gear because after having a perfectly good plotter they no longer supported with maps, that's when I went to Si-Tex and Standard Horizon electronics who use Jeppenson c-map nt chart cards and have for several years as far as I can tell. I just bought a new SH cp590 plotter for the lower helm because it will support my Si-tex radar and Jeppenson charts that I have.

[skipmac]

Originally Posted by colemj

I wasn't very clear on that. What I meant to get across was that the basic brains of all of the autopilots are just computers that all use nominally the same amount of power. If there is a difference, it is very small - for example, our Simrad computer and control head together draws only 0.5A. So the only real power difference (leaving out the actual boat and its characteristics) is due to the drive unit itself.

The power use of the brain part had not occurred to me but assuming more or less equal power draw by different brains would make sense. Some minor variations but considering the overall power draw of an AP a small difference.

Ignoring aberrations like the no clutch design of the Alpha and the differences between hydraulic vs direct drive I think there can be a big difference based on duty cycle. A smarter AP (or a properly adjusted and tuned manual AP) in my experience can run the motor much less than a dumber or poorly tuned unit. I have had APs that off the wind steered much like a good helmsman, almost anticipating the stern slewing around and compensating less but earlier as a wave passed under the stern. Others reacted much more slowly and had to work harder as the boat had already yawed and picked up speed, increasing the load on the rudder AND had to turn the helm much further to get the boat back on course.

No hard data but I think this can make a very big difference in daily power use.

Originally Posted by colemj

For example, the Raymarine electromechanical linear drives draw on average 1.5-3A for the small one and 4-6A for the large one. The Simrad hydraulic linear drives draw on average 3.5-10A for the small one and 5-16A for the large one. The Raymarine reversing hydraulic pump draws 9A for the small one and up to 34A for the largest one (there are several sizes in this series).

We have owned the electromechanical and hydraulic linear drives above on the same boat, and I can state that those power consumption figures are accurate. In average conditions, the large electromechanical used 3-5A and the large hydraulic linear used 7-13A.

This brings up a very interesting point. I have seen recommendations from some that hydraulic is the only way to because it is much more reliable than mechanical drives. My question, since either unit would have to do the same amount of work plus the hydraulic has additional moving parts plus hoses and fittings I would think a good quality mechanical would be as reliable as a hydraulic drive if not more so. Add lower power use for mechanical is another plus. I have also seen comments that hydraulic can be noisy.

Unless I can understand if and why hydraulic is that much more reliable I think mechanical is the way to go.

[colemj]

Originally Posted by skipmac

Ignoring aberrations like the no clutch design of the Alpha and the differences between hydraulic vs direct drive I think there can be a big difference based on duty cycle. A smarter AP (or a properly adjusted and tuned manual AP) in my experience can run the motor much less than a dumber or poorly tuned unit. I have had APs that off the wind steered much like a good helmsman, almost anticipating the stern slewing around and compensating less but earlier as a wave passed under the stern. Others reacted much more slowly and had to work harder as the boat had already yawed and picked up speed, increasing the load on the rudder AND had to turn the helm much further to get the boat back on course.

No hard data but I think this can make a very big difference in daily power use.

Yes, duty cycle is definitely a large part of power draw. In an earlier post, I said ignoring rate compass and advanced algorithms would be a mistake. It is these two components that determine duty cycle (boat and sea state being constant).

Frankly, I think the rate compass is probably 80% of it or more - it is dramatic what a difference that makes, and lack of experience with them is probably why there are still people out there who think it is silly to step up into these "complicated" (read "newer") systems. It really is that dramatic of a difference.

As for the steering algorithms, there are certainly differences - and at the high end of racing, those differences are dramatic and hard fought after - but for most cruising boats, there isn't really that much of a difference anymore. At least none that I have been able to pick up on.

Originally Posted by skipmac

This brings up a very interesting point. I have seen recommendations from some that hydraulic is the only way to because it is much more reliable than mechanical drives. My question, since either unit would have to do the same amount of work plus the hydraulic has additional moving parts plus hoses and fittings I would think a good quality mechanical would be as reliable as a hydraulic drive if not more so. Add lower power use for mechanical is another plus. I have also seen comments that hydraulic can be noisy.

Unless I can understand if and why hydraulic is that much more reliable I think mechanical is the way to go.

At some point of vessel size/weight/characteristics, the electromechanical linear and rotary drives run out of steam and hydraulic linear drives go further in size. For hydraulically steered boats, the reversing hydraulic pumps are the most reasonable solution.

Hydraulic drives have fewer moving parts than electromechanical, and some of them are compact units with no hoses, fittings or reservoirs.

I won't debate the ruggedness or longevity of the two types. We have both on board. The hydraulic linear is 12yrs old and it has needed during that time a new solenoid, new seals and bleeding. It needed these only after 12yrs of use, during which it never failed to handle things, so I don't consider that not rugged or high maintenance. We have been using the electromechanical for the past 4 years and it hasn't needed anything yet and has never failed to handle things.

Comparing the two, there is no doubt the electromechanical uses half the power of the hydraulic. And it is virtually silent even when laying on the berth directly above it, where the hydraulic was audible in the cockpit and we would not sleep on that berth when it was running.

Mark