autopilots and systems

[drk]

I have a ten year old 'system' autohelm st80 with st7000 autopilot. Raymarine no longer 'supports' this nor does it do anything to keep the customer happy - every year another part of the system fails and has long expensive repair process. now my gps and autopilot don't work. I have always had poor performance in quartering seas and have always thought the pilot should have heel angle input as the boat rolls or heels over with wave or wind puff and then heads up - so I can steer verry straight by hand - anticipating and avoiding the heading change by turning the wheel in response to the heel angle change before the boat heads up -and weave wildly under pilot.

Now the pilot is quite caput in total. I could send it off for repair again or I could tell them #$%!!! and go buy a 'different system' in toto. Whose? at what cost? get all new instruments, radar, plotter?

 

[Guest]

I think that the autopilot to be expected to "anticipate" seas as you do by hand is unfair. An autopilot learns by the boats motion and if the motion changes it has to learn again.

1/4'ing seas are particularly bad for most autopilots / helms and easing of the boat is often advised ...
When seas come more aft - even downwind tacking can be used to improve.
Reefing a little earlier than you would if hand-steering is common need .. autopilots / helms really do not like unbalanced boats ... you on other hand - when helming can live with it and compensate .... again as you say anticipating. The Auto cannot - it is purely a reaction machine.

 

[andy01842]

I don’t know how big your boat is but sounds as though your system is working to hard and a bigger more robust system would be cheaper to run in repair cost. So I would suggest you do your homework before you buy so as to not end up with the same problem. Hope this helps.

 

[Sea Devil]

because I could no longer get parts I have replaced my old Cetrek autopilot - with a Raytheon hydraulic system... onto my hydraulic steering - just waiting for a quiet day to go out and 'calibrate' it... During the installation the one thing that struck me was how small and compact all the replacement items are... I have the feeling (yet to be proved) that its going to work pretty well...

My guess is that electronics over around 10-12 years are about finished... If they are still working OK then I live with them but when they break down, like old washing machines, it is probably not worth paying to get them repaired and if the parts are not available and easily installed as a DIY job then definitely they need replacing.......

I totally agree with the last post - I think your present autopilot is underpowered and perhaps not sufficiently responsive... Needs some research before buying again..

 

[Talbot]

Your details dont say what size boat, so it is hard to respond accurately. The size of the existing system indicates that you have a 36 ft + boat. Again, there is no indication if your steering is hydraulic or cable, or even if the existing autopilot is hydraulic or linear drive. Again from the size of boat, I suspect that you are hydraulic.

There have been big advancements in autopilots over the last few years, specifically to aid response in poor weather conditions. This is primarily achieved by the addition of rate gyros to the system, although you can still get the systems without these gyros cause they do add a financial penalty!

Basically you gets what you pays for! If you can afford a new gyro system (and appropriate spares) then that is the best solution.

 

[gardenshed]

An inboard autopilot with a gyro will most likely give you the result that you are looking for.

 

[Slow_boat]

I don't know much about auto pilots (the one I got with my boat last year is the first time I've used one) but surely the first thing to do is ensure the sail plan is balanced to give the lightest helm possible? That was always the way when lashing the helm or connecting up the old wind vane.

Or am I an old fart talking complete tosh?

 

[gardenshed]

not quite tosh but kinda missing the point.
Broad reaching in a quartering sea is where a badly set autopilot will work its guts out reacting to the boat moving around. If you have a fin & Skeg, then there isn't the directional stability of a long keel and even with a balanced sailplan, it is amazing just how much corkscrewing around the boat can do. If the pilot is only taking input from a compass, it is trying to keep you exactly on the set course and using the pre set parameters to decide how to react to course changes e.g.
Response: How far from course it allows the boat to move before responding
Ratio (gain): how far the rudder moves to respond to a course change
Trim: compensation for a consistent off course movement
Counter rudder: consistent offset needed to hold a steady course:
If these parameters are set up so that a small movement triggers a large, quick rudder deflection there is a possibility that the system will go beserk in a quartering sea.
Including a gyro to measure rate of turn and not just the angle that the boat has turned through, and with clever programming, the more sophisticated autopilots change the parameters (if they have an adaptive mode) to allow a reaosnable movement of the boat and to minimise the movement of the drive ram.
Its a bit like having a very eager inexperienced helm thying desperately to hold a precise course where as a more experienced helm will feel the movement and greatly reduce the helming inputs.
On my pilot, you can create different settings for different sea conditions or allow the computer (in adaptive mode) to work out settings for itself.
With a wind vane there is a natural damping and conmpensation built into the system through the mechanical linkage so in some ways, the old mechanical systems are quite clever and do some of this "control theory" stuff without any silicone chips.

 

[Guest]

Why need expensive ? The post you've just given could apply to just about most AH / TP's on the market .... Even the cheapo Tiller-pilot like my AH1000 "learns" the boats motion so that it does not get into a "see-saw" effect. I can even reset it or remove the dampneing / learning factor and have raw autohelm - gets crazy then.

Of course go up to Gyro's etc. and get even better sea-state facility - but if boat is unbalanced then all your doing is cheating to beat it.
The original post mentions corrections for heel - that to me is a give-away as it indicates that boat is heeled and maybe hard pressed anyway - so autohelm is going to be lucky to handle it.

I know mine was near impossible until I bit the bullet and reefed / reduced load on system - then wonders of wonders ... it worked and loss of speed (only small) was made up by the comfort of the AH doing the work.

 

[jff]

I was amazed at the difference adding the gyro to my autopilot made. Before I couldnt trust the ap with any sort of developed wave, particularly a following sea. Now I can leave it on for days, only disengaging it to make sure the loads havent built up. I've also noticed that the overall power consumption has reduced, I suspect that this is due to a smaller amount of helm being applied earlier to keep on course

 

[tome]

Agree with you. Our old st6000 struggled in any following seas to the point where we had to take over with hand steering. This made short-handed sailing tedious when you couldn't leave the helm to make a hot drink

Just replaced it with Raymarine S2G which has the rate gyro - the difference is quite astounding, especially downwind. It also has an autolearn mode which carries out a series of course alterations to learn the steering characteristics of the boat

The new autopilot gives the option of steering a course, following a waypoint, or sailing at an angle to the wind so much more versatile. We didn't need to change the drive unit