ST3000 autohelm

[mireland]

My ST3000 was working just fine then off the Lizard it steered a course 50 degrees off the one selected. Despite swithching off and on it persisted with this interesting trick. What might be going on?

The control unit has a wire going to the wheel drive unit which I understand but what is the other cable coming into the control unit? Could it be from the GPS and if so what does it do with the info from the GPS?

Sorry if these are the wrong questions but this is all very new to me and the boat comes with loads of old electronics and lots of wires that are too much for me!

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[johna]

Hi
I have a ST3000 autohelm system and it has in effect three sets of connections
Head unit to Motor (as identified by you), 12v Power supply and data out/in to the HSB system providing information to plotter/radar etc and also will accept information for course steering from the plotter. Although the HSB system has a power supply the ST3000 does require its own separate supply.

As to what has changed to cause your problem I do not know but let me give you the benefit of my experience. When I purchased the boat the ST3000 Head unit was located to the extreme right and forward end of the instrument array and was most difficult to get at for those hurried course changes to miss pots. I moved it to the inboard end of the array making it easier to get to. All units moved and re-fitted when I noticed that the heading on the berth was about 60 deg different from what it is. Penny dropped I had moved the head unit to the other side of the windscreen wiper motor located forward of the instruments. No problem go and motor round in circles and re calibrate. Good and back to the right heading until I use the wiper and then the changing field just sends it bananas.

So the moral is have you put something the otherside of a bulkhead that is affecting the heading? If not them may be the compass in the Head unit needs attention. Try Raymarine I have found them to be very helpful.

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[philip_stevens]

My brand new (this year) ST3000 would not display any compass bearing other than (trying to remember) 160 or something like that. We could not steer by autohelm as the boat was going to starboard at all times.

As it was brand new, I contacted Raymarine who advised me to send it to my nearest repair agent, SM Group at Plymouth. It came back two days later working properly. I asked what the fault was, and was told that a wire to the fluxgate compass had broken. (Possibly a solder joint). It has worked perfectly ever since.

It may be worth your while opening the unit to check if all the wires to the fluxgate compass are still made or if one has broken/come adrift.

It has already been explained what the different wires are for, but my ST3000 is connected to an Interface box to convert the NMEA from the GPS to Seatalk for the ST3000. With this connection, we can steer by GPS Plotter on a route or by Autohelm fluxgate compass alone.

Steering by GPS on a route is a bit more assuring during thick (misty/foggy) weather, as you stay right on track and are not affected by (cross) tidal flow. You cover more distance through the water this way, but you are more re-assured that you are where you want to be - and not being pushed over rocks or shallows. I use the GPS Plotter in "Autohelm route mode" when motoring or in thick weather, and the Autohelm fluxgate compass in "Auto" when sailing in good weather.


<hr width=100% size=1>regards,
Philip

 

[johna]

You state<Steering by GPS on a route is a bit more assuring during thick (misty/foggy) weather, as you stay right on track and are not affected by (cross) tidal flow.>

I believe you are affected by cross tides unless you have a system that predicts and compensates for the tidal flow. I agree that the system may continue heading for the way point but the course steered will change. I believe there is a X track error setting to warn you of this.

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[philip_stevens]

When the Autohelm is switched to "track" mode, the GPS input steers the helm, and keeps the boat on the track by showing bearing degrees and steering degrees. If there is a cross tide, the bearing and steering are different. The boat can be shown on the display as "crabbing" along the course line.

I motored from Looe to Falmouth a few weeks ago, as the wind was dead on the nose, and I didn't want to sail halfway to France to be a purist. We used the track mode on the Autohelm to steer us on a route that was basically one long leg to Zone Point (Falmouth) after rounding Looe Island.

We didn't meet any other boats until off the Dodman, when other yachts from Fowey to Falmouth came on the scene. During this part of the leg, some of these yachts (motoring) went south of our course line, but then came up to similar waypoints off Saint Anthony. They were being set south by the tide and then had to compensate. We, on the other hand, stayed right on the line all the way.

Cross track error was minimal, even though there was a SSW setting tide flow over most of the route with a noticeable S setting tide off the Dodman.


<hr width=100% size=1>regards,
Philip

 

[johna]

With respect Looe to Falmouth is hardley a cross tide situation as the tide is virtually the same as the route line and less than 1 knot at springs.

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[philip_stevens]

But that was just an example. I have also gone across Channel, Falmouth to Camaret, in a power-boat using the track facility in a poor horizon situation.

What I was trying to say when using the GPS to Autohelm "Track", is that the boat will stay right on the course line with virtually no XTE.

<hr width=100% size=1>regards,
Philip