ST4000+ calibration?

Rob_Webb

Rob_Webb

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Still not happy with my ST4000+ performance. Got an average 35ft yacht, perfectly standard sailing characteristics but even in light to moderate conditions the autopilot yaws around the desired course too much. In heavy conditions I really can't rely on it for any period of time. Given the spec says up to 8.5 tons and I'm only 5 tons I should be well within capacity. And this is after I've balanced everything fine and steering manually only requires light & minor adjustments to the wheel - but in a short time the ST4000+ is yawing around (easily 20-30 degrees either side of course).

I've tried playing with various settings but there are almost too many different factors to calibrate e.g. reponse type, rugger gain, rudder damping, turn rate, auto trim, auto adapt etc.

I've tried resetting to factory defaults and starting again, trying to change one factor at a time gradually over several months but still haven't found the right combination to give satisfactory performance.

Any ideas?
 
The performance should definately be much better than that. I have one on my 31-foot, 16,000 lb power cruiser and it really holds a steady course, even at a slow cruise of say 7 knots. Have you done the circular calibration that calibrates the flux-gate compass?

The big difference between your boat and mine is probably the much greater effectiveness of the rudder on your boat. I do notice that if I were to cruise at only 5 knots that there is a some tendency to wander a bit. The only thing I can think of in your case is that the rudder gain is too high. But, I guess you've tried adjusting that.

I even have mine connected to the GPS so it will follow a course from the GPS. That works great also; very steady.
 
Yes I've done the calibration of the fluxgate (about 2 circles it took) and set the typical cruise speed to 6kts (as opposed to your 20kts I imagine).

I'm also connected to the wind instrument (via NMEA) and can ask it to follow an apparent wind angle but that also wanders about too much.

How much customisation did you have to do of the varioud settings to get it right? Or did your work fine out of the box?
 
Very happy with my ST4000+.

Sounds like it could be a FG compass problem to me - not keeping on course.

Have you performed the "Automatic Compass Deviation Correction"? See page 69(?) of the installation manual. (edit - just saw your post above forget that idea then /forums/images/graemlins/confused.gif)

Failing that see if you can borrow another compass head and try that one.

Is the compass correctly mounted and away from sources of magnetic interference?
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hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
 
[ QUOTE ]

Is the compass correctly mounted and away from sources of magnetic interference?
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Ehhr, You don't hang your jacket with cell phone inside in the locker just above the compass, now don't You??
 
the one encouraging bit about your travails is that when these things lose the plot they just drop out of auto and yours doesn't; so at least it thinks its still in control ...

as far as you know, does the displayed compass heading broadly agree with the boat's compass when she wonders off by 20 degrees?
 
[ QUOTE ]
Ehhr, You don't hang your jacket with cell phone inside in the locker just above the compass, now don't You??

[/ QUOTE ] 'Tis not me with the problem. My 4000 works just fine. /forums/images/graemlins/cool.gif
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hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
 
Where is your fluxgate? You want it as near to the centre of motion as possible - i.e. midships along the lubber line, ideally. If the fluxgate is too high then every time the boat heels you get heeling error which results in a false error signal being sent to the autopilot, which alters course, causing healing as a result of the correction.
 
We had a ST4000 on our last boat and it steered brilliantly, so there must be something wrong with the settings as you surmise.

Will it steer a steady course under motor in a flat sea?

If it is yawing about in a flat sea, then the rudder gain is too high.

It should be high enough that it will follow course alterations without a huge 'overshoot' and then settle on the new course almost instantly.

Try talking to Raymarine. They are usually very very helpful. You will need to describe the exact conditions and what actually happens. ie does it constantly wonder off course, or just occasionally have a wobble and find it hard to return?

The Gyro that we have on our Raymarine system is very good at sorting the autopilot out in following seas and if its any consolation, I could never get our old or new system to steer to wind very well.... I think the electronics can probably do it quite well, but I got bored with fiddling with the settings to make it all happen.
 
I would start with the Rudder Reference unit. It's a very simple device but worth looking at. My 9 ton long keeler uses a 4000+ Tiller and not surprisingly the autopilot had all the characteristics which you describe. But when I fitted a Rudder Ref Unit it transformed the boat. She is steady on all points of sail, even downwind and in rough seas. Perhaps your unit has a fault.
 
Is the physical set up correct (ie 460mm from pivot etc from memory - don't quote!)? Too close to the rudder will increase the sensitivity.

Otherwise I would agree that it sounds like a fault if you have already de-sensitised the rudder gain etc. - looking at the actual heading whilst it is trying to come off the heading is a good idea. If the compass if jumping around then the physical siting of the compass, checking compass leads etc. worth looking at.

Can't see why fitting a rudder reference unit would help - although if others have experienced a benefit in using one then it must help in some way.
 
I don't remember having to make any changes other than to put in the average cruise speed. While my boat will do almost 20 knots full throttle, I am doing most of by cruising at around 7 knots (for fuel ecconomy). Although, if I didn't care about the price of fuel, I would probably do most of my cruising at 14 knots. The boat really rides nice at that speed. Around here though, we really have to watch out for logs at that speed.

Also, I didn't need to put in the rudder position sensor. My helm is a wheel driving a push-pull cable to about a 12-inch a tiller arm. And, of course, my rudder is much smaller than on a sailing yacht. The push-pull mechanism has about 1/8th of a turn freeplay. I don't know just how much this affects the overall rudder gain, but I suppose it may tend to reduce the gain.
 
Update

Update and replies to some of your Qs:

Yes motoring in flat water is see-saws around the desired course too much. I have already tried reducing rudder gain to minimum but still does it.

Boat is cedar core glassed over. Fluxgate is mounted down in the bilges, on the centreline and as close to amidships as poss without being close to keel bolts (not sure if they are ferrous).

I have Whitlock direct wheel linkage i.e. no quadrant as such. And not hydraulic. Hence I did not fit the rudder position sensor, as manual says only mandatory for hydraulic systems.

Spoke to Raymarine agent who suggested I fit the sensor. Also when I calibrated the compass (motoring in circles) it gave answer of deviation around 15 degrees if I recall. I thought that as long as system now knows it's maximum deviation then it can handle it. But he said that was too high and I should resite compass to get reduce it to 5 degrees or less.

So I guess I've got some more mucking arouhnd to do with the physical installation before I worry about calibration settings. Maybe I'll then find the factory defaults are virtually adequate.

Will spend time on it this w/e and report back.

Cheers
 
Re: Update

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I have Whitlock direct wheel linkage i.e. no quadrant as such. And not hydraulic. Hence I did not fit the rudder position sensor, as manual says only mandatory for hydraulic systems.



[/ QUOTE ]

I was going to suggest the rudder feedback had failed but you dont have one. The symtoms are the same I had years ago when my feedback failed. They can be a problem if water leaks onto them from the steering "tiller" . Mine actually has a piece of SS forming a roof over the sensor to prevent this.
 
I had a similar problem on my boat after delivering it to Scotland from the South Coast. Check the latitude setting. It seems to have a significant effect on the fluxgate compass sensitivity - all to do with the horizontal strength of the earth's magnetic field.
 
Yeah spotted that already, thanks, have it set to 36 degrees south. Still steering a drunken course.

How well does your handle gusts?
 
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