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Old 11-03-2013, 13:48   #16
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Re: Autopilot recommendations?

What is over loaded?
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Old 11-03-2013, 13:53   #17
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Re: Autopilot recommendations?

Thank you guys for all the feedback!
The boat I am talking about is a 30 foot S2, fin keel, 9800pbs (so not really on the heavy side)
So it should be well within the limits of the wheel pilots as well, even though I like the idea of having gear out of the weather. It will be used cruising and not just for daysailing, so maybe it will be worth going for the under deck option...
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Old 11-03-2013, 14:54   #18
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Re: Autopilot recommendations?

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What is over loaded?
The arm. They are sized for max load by each manufacturer. I mean not the boat load, I mean the force load on the arm.

IMHO if you are regularly over 50% of the marketed max load the arm will die prematurely.

b.
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Old 11-03-2013, 15:08   #19
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My CPT has taken care of me for over 15 years on a 18 ton boat yeaj
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Old 11-03-2013, 15:38   #20
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Re: Autopilot recommendations?

The Raymarine SPX-5 has garnered criticism for overload failures but otherwise is an OK system. I have had several such failures, with the tiller model, on an admittedly heavy (20k#+) boat. I don't feel this should be carried over to the below-deck models, with properly chosen drives. That said, I dislike that RM is still using mechanically-gimballed fluxgate compasses - the standard these days is solid state. The 5 doesn't provide compass updates fast enough for some chartplotters (5Hz vs 10Hz); The SPX-10 does support the higher rate.

I would avoid all in-cockpit drives, whether wheel or tiller. They aren't nearly as robust as below-deck drives.

It seems to me that there is a fundamental choice between the simple, independent autopilots and the latest high-tech pilots with lots of interfacing. Either can work very well if properly selected and installed. It is more a matter of personal preference. It can be useful to have the AP follow a track to a waypoint, correcting for cross-track error (XTE), which requires a connection between the GPS/chartplotter and the AP with some smarts. OTOH much of the cool-sounding high-tech features are of minimal value. Your choice.

There is the possibility of mixing the drive (servo) from an outside supplier with the marine AP. I am looking at one of these to replace the RM drive, at 1/4 the price, 2X the thrust, and a reference transducer: 560 lbs. Thrust Linear Actuator This won't work for you, as it doesn't have a clutch. Personally I hate the solenoid-actuated clutches as they continuously draw 1A or so in unnecessary power while the AP is engaged.

BTW I assume you have a mechanical linkage of some sort. If hydraulic then that changes your options.

Greg
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Old 11-03-2013, 19:36   #21
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Re: Autopilot recommendations?

Thank you for the answer Carina,
My steering is wheel with cable, so no hydraulics involved. And Autopilot vise there is nothing on board yet. I have a Garmin GPS Map though and until yesterday thought to interface it with an AP it has to be Garmin as well, but that is apparently wrong (via NMEA etc.)
There are good points for both, wheel drive and below deck pilots, the only thing being, that below deck seems to be at least 1000 extra and being a sailor (for living, not only pleasure) I am not so very much on the wealthy side.
I also started looking for used systems but couldn't find a lot of gear that would actually work for me...
Or maybe there is some website for used sailing gear that I didn't come across yet... ideas?
Thank you all already for the support!
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Old 11-03-2013, 19:53   #22
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Re: Autopilot recommendations?

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Originally Posted by barnakiel View Post
The arm. They are sized for max load by each manufacturer. I mean not the boat load, I mean the force load on the arm.

IMHO if you are regularly over 50% of the marketed max load the arm will die prematurely.

b.
My experience is that the pilt usually makes very minor rudder motions unless you are driving through messy seas.... or perhaps tacking which pushes the rudder hard over.

I can adjust the amount of work the AP does... limiting minor corrections, electricity, heat, wear and tear and so forth. When conditions are to rough for the AP, I have to drive but I don't feel much pressure on the wheel because I trim the boat to not drag the rudder.
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Old 11-03-2013, 20:05   #23
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Under deck drives are far better for cruising. I keep my control units out of the weather too as they don't have a great record of staying dry.

The position transducer greatly improves pilot stability. It is not only to provide an indication to the helmsman. Servo design without proper feedback is foolish.
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Old 11-03-2013, 20:58   #24
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Re: Autopilot recommendations?

Saving $1000 by buying a cockpit AP is a false economy; they don't hold up nearly as well as drives attached to the quadrant. In fact, good drives below decks rarely fail - and that is certainly not the case with cockpit drives. If you were only going to do some local cruising then it might make sense; for blue water it doesn't. That simple.

As you have discovered, any AP that takes NMEA signals (0183 or 2000) can receive bearing-to-waypoint and cross-track error from any GPS with a matching interface. That said, some multi-function displays (MFDs) can be used to control the autopilot if the mating AP is found, probably restricted to the same vendor. Personally I am happy with a dedicated AP controller, separate from the MFD.

Another thing which I had referred to earlier is that the MFD will benefit from access to fast compass updates - necessary for mini-ARPA funtionality (very useful) and north-up display (not so useful IMHO). You should check the MFD's requirements and make sure that the AP can deliver. My RM SP-X 5 does not update fast enough for my Furuno MFD, so I had to buy a separate solid state compass; in the end I removed the old RM compass and am using the Maretron compass for the AP as well. If you buy a Class B AIS the compass info (heading, rate-of-turn) will be transmitted if available. If you also have the knotmeter connected, the speed-through-water will also be transmitted (in addition to the GPS COG and SOG info). Probably not a big deal, but it will alert other vessels to a course change sooner.

Greg
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Old 12-03-2013, 03:31   #25
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Re: Autopilot recommendations?

Hello again and thank you for all the different input from all sides!
As things look I am pretty convinced about the Garmin GHP 12 Autopilot but not necessarily with the Class A drive unit. for that I am looking into the Simrad HLD 350 (any experiences with that one?) and I was also wondering if the Simrad SD10 would work. It seems like it is attached directly to the steering cable. Therefore the redundancy would be lost (in case the cable breaks?) so that would be a plus for the Class A or the HLD 350 I guess?
What are you people out there using for your little (30 foot) cruising boats?
Thanks a lot another time!
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Old 12-03-2013, 07:55   #26
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Re: Autopilot recommendations?

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Originally Posted by defjef View Post
(...) I don't feel much pressure on the wheel because I trim the boat to not drag the rudder.
Yes. You are in the right boat.

Some boats that have 'barn door' rudders will require plenty of power to steer in some conditions. They are in fact AP killers.

To me, if a boat under 50 cannot be comfortably controlled with a tiller then well, eh, I say there is a design issue there. Wheel is a nice device but too often used as a cover up (for excessive rudder loads) by the designer ...

It is great if the boat required less force and if she can be trimmed to fit the conditions, but not all boats are that good.

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Old 12-03-2013, 08:14   #27
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Re: Autopilot recommendations?

Quote:
The Raymarine SPX-5 has garnered criticism for overload failures but otherwise is an OK system. I have had several such failures, with the tiller model, on an admittedly heavy (20k#+) boat. I don't feel this should be carried over to the below-deck models, with properly chosen drives. That said, I dislike that RM is still using mechanically-gimballed fluxgate compasses - the standard these days is solid state. The 5 doesn't provide compass updates fast enough for some chartplotters (5Hz vs 10Hz); The SPX-10 does support the higher rate.

The raymarine heading compass has been a fluxgate compass for many years and can be optionally aided by a gyro module ( smartheading sensor) ( or that is in the autopilot controller ), which can do 10Hz updates over 0183 ( not sea talk).

all heading fluxgates have to be mechanically gimballed, Rays is a bit clunky, most now are gimballed silently inside a sealed mount. ( See Autonics Research http://www.autonnic.com/floating-core-magnetometer.html OEM range for example)

The major failure model on X5 wheel motor is exceeding the 16,000lbs displacement limit and Ray suggest you have it 25% lower to allow for conditions.

Dave
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Old 12-03-2013, 09:09   #28
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Re: Autopilot recommendations?

How much precision is required for a heading? Gyro compasses and all sound wonderful.... but really... what is gained of tangible value?

My boat is quite balanced and so typical forces to steer are not all that much... That isn't to say that there are times when forces on the rudder get up there... but for most conditions no...
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Old 12-03-2013, 09:14   #29
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Re: Autopilot recommendations?

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Originally Posted by defjef View Post
How much precision is required for a heading? Gyro compasses and all sound wonderful.... but really... what is gained of tangible value?

My boat is quite balanced and so typical forces to steer are not all that much... That isn't to say that there are times when forces on the rudder get up there... but for most conditions no...
It helps, particularly in quartering seas, running downwind.

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Old 12-03-2013, 13:25   #30
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Re: Autopilot recommendations?

Agree with above comments: barn doors as I have are AP killers. Selecting an AP based on displacement is very crude; the real issue is the required steering forces. These are small for balanced rudders - even for large, heavy boats. Barn door - i.e. unbalanced - rudders can require very large steering forces on a small boat.

It is a requirement for any autopilot or self-steering system for the boat to be trimmed to neutral helm, or nearly so. The problem is as noted above: off the wind with a quartering sea creates potentially huge steering loads, as overtaking waves cause sudden yawing. Virtually all of my AP failures have occurred in this situation.

The advantage to modern solid-state compasses is that the AP can detect, and start countering, sudden course changes (as above) sooner. Of course most of this is a result of the solid state accelerometers. But the lack of inertia (mass of sensor in the gimbal) gives faster reactions in critical situations; admittedly 99+% of the time this is makes little difference but it can - or at least should - improve performance in rough conditions. I think that the change in compass has improved my AP performance, but have to admit that it could be all in my head...

Greg
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