Autopilot Recommendations

[delatbabel]

Hi,

I currently have a Raymarine S2 autopilot which I'm not very happy with for a wide range of reasons. In particular its performance (ability to hold a course) at low boat speed is next to zero.

Does anyone have any experience with this and/or other types of autopilot? Which ones have you used, which ones work for you and don't work for you, and which ones can be set up or modified to work reliably on a cruising yacht?

I have been looking at specifications for the coursemaster and simrad units, but I'd like some real world experience to help me decide.

Del

[alan]

I inherited a Coursemaster 850 on my current boat and I have struggled to understand it right from the word go. However I eventually worked out, with the help of Coursemaster (Sydney) that a control wire for the gyro was not connected!! It now seems to be working better, I think it takes time for the computer to learn its new cofiguration. However I have not experienced huge following seas with the new config yet so the jury is still out. Sailing down wind with big seas was a nightmare before so I hope it will be improved now.

It's no easy decision to re autopilot primarily for the cost involved but also redoing all the setup, wiring etc!

Delve deeper into the reasons why your pilot may not be performing, it could be as simple as magnetic influences or wiring. Contact customer support for ideas.

[MMNETSEA]

The Choice of which Auto Pilot may depend greatly on how the boat steers without an Auto pilot, in different sea conditions. Other factors to be taken into consideration are the size, design and placement of the rudder relative to the transom - the depth of the rudder below the surface another major factor.

Knowing the boat's brand, model and design would help.

[Yttrill]

Hah, well I am having fun getting Coursemaster to talk to me... they don't like my autopilot rudder and they won't tell me when they're going to release their NMEA 2000 based pilot (and I will not spend $5000 on an out of date NMEA 0183 based system).

I'm using a Raymarine ST1000 (tiny weenie) tiller pilot to drive my boat at the moment (using a trim tab).

Frankly, I don't believe ANY of the autopilots around are very good; given the ridiculous prices for what amounts to a $100 computer with a simple servo algorithm. Most of these pilots only have the input from the heading sensor (and rudder angle) and that simply isn't enough to steer a boat properly. At least with N2K there's some chance other variables like pitch, roll, boat speed, and course (vs heading) might help to steer a bit intelligently.

Also note standalone autopilots cannot steer to a waypoint. Most should steer to wind instead of compass though.

Take a lesson from Jessica vs Abbey: Jessica made it around the world with only a wind vane. Abbey abandoned her attempt due to both autopilots failing to operate correctly (the first time due to lack of power).

[delatbabel]

Yeah, I hear what you're saying. I also have an Aries windvane which I'm very fond of. On the wind it holds a course beautifully, for days. Running downwind in light winds it tends to be less accurate.

I think that the Raymarine guys need to program in one simple algorithm if it doesn't have its speed sensor data, which is:

* Is the boat on course?

* If too low, steer up. If too high, steer down.

* Repeat.

At the moment what my S2 does is this:

* Is the boat on course?

* Don't care. Steer in a randomly chosen direction.

* Is the boat off course by more than what the off-course alarm is set for?

* If so, sound off course alarm. Give up and start steering in circles.

Basically, it's an expensive off-course alarm. I could have built that myself with an electronic compass and $20 worth of parts from Jaycar.

[Yttrill]

Originally Posted by delatbabel' date='23 May 2010 - 04:15 PM

Yeah, I hear what you're saying. I also have an Aries windvane which I'm very fond of. On the wind it holds a course beautifully, for days. Running downwind in light winds it tends to be less accurate. I think that the Raymarine guys need to program in one simple algorithm if it doesn't have its speed sensor data, which is:

At the moment what my S2 does is this:

* Is the boat on course? Don't care. Steer in a randomly chosen direction.

* Is the boat off course by more than what the off-course alarm is set for? If so, sound off course alarm. Give up and start steering in circles.

Well, it's hard to know what the problem is here: I have a Raymarine ST1000 which does roughly keep course, though I have only tested it with my steering system downwind. Observing it zig-zagging I seem to perceive that the fault is not with the control head but the fluxgate compass: the boat yaws and the off-course indication on the instrument takes a while to respond. The actual drive and rudder system respond very fast once the heading is seen to be wrong.

What my system does is: if the boat is off course, it applies some rudder. If that doesn't bring the boat back on course, apply some more. Unfortunately, since there is no rudder angle indicator, it is just guessing. When the boat is back on course it should recentre the rudder, but it doesn't know where the centre is, so it is always basically zig-zagging.

However my tiller drive is turning a trim tab which turns the trailing edge of a massive transom mounted rudder, and this brings the boat back on course even when it is 60 degress off course, since that rudder is actually bigger than my main rudder

The algorithm is supposed to learn how to control the boat according to the manual. It's probably a bit tricky on my boat because it isn't controlling the rudder directly, but via a trim tab, so there is delay while the trim tab adjustment move the tiller, especially in light winds.

I found the system had enough lag in it that I turned the dead-band off completely. That's the error tolerance which is ignored completely, by default I think it is +/- 10 degrees. That makes the drive work continuously, but it also speeds up the response. The actual sensitivity (gain: the amount of correction to apply) didn't seem to make any difference.

So I guess the question is: what kind of heading sensor do you have? Is there a rudder angle sensor? I guess you're driving a wheel which drives the main rudder?

[delatbabel]

The heading sensor I have is a fluxgate. It works fine, and I even take a NMEA lead out of the autopilot to the TackTick wireless box so I can have a wireless compass display mounted on the bimini. The rudder sensor works fine, I can see the sensor readout on the display of the autopilot.

No, it's just the autopilot software, it's basically stuffed. It makes very little attempt to keep the boat on course, and doesn't seem to care if it is on course or off course. When the off course alarm goes, the autopilot gives up, and I've been told by Raymarine this is normal (but stupid).

The autopilot drives the tiller directly via the hydraulic ram.

I have an older ST4000 which can be connected to the same rudder sensor and fluxgate. It works fine, although the belt driving the wheel snapped and now I can't get a replacement.

[Silver Raven]

Hi y'all. Big print's cause I can't see the small print easily. Old(er) sucks - in my case. The ST4000 "wheel snapped". What is the 'wheel' made of - please? I've just rebuilt 'a sump', a whole engine side & several other 'bits' that were not 'gettable' at all. Now 1 1/2 years later - they are still 'working just fine' thank-you. Hope this topic is not 'done with yet' & I might be able to be of some assistance. My charges are very expensive though - like - a drink or 4 - sometime in the future - if we ever get to meet. 'In other words - FOC - so if you wish - get back to me via this message board or direct at jamesaviculture@hotmail.com I'm just 'up-the-road' as they say in Auzzie terms. Am ex 'plastics person & a yachty still.

Ciao, james aka jj aka Silver Raven.