Autopilots

[Woodpile]

I have a 50-something ft displacement wooden motorboat. It is wheel steered with a hydraulic system that is finger-light in all conditions. I'm looking at cheap wheel-mounted autopilots designed for sailing boats - like the ST4000 - and wondering why one wouldn't work on my boat. Unfortunately the bumf always says suitable for 30ft and 10 tonnes max (or something similar). Does anyone know why - or is this limitation simply for boats with direct steering linkages where wave action could overpower the drive unit? (My top speed is around 11 -12 knots, if that's relevant.)



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[Rohorn]

Hi...I have an st4000 on a 5.5 ton sailing cat. The steering wheel is 75 cms in diametre and in the worst conditions the force one has to exert at the wheel rim is around 6 kgs. The st 4000 gives up before that, but for 90 percent of the time it's adequate. In your case I'd expect the same to apply, although check your wheel diametre and applied force in worst conditions to see if they compare to my figures. Just means that when the going gets rough, you have to take over, which you'd probably do anyway. Hope that helps.
Cheers....R

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[andyball]

one thing raymarine mention is the lack of a definite centre position of the wheel on many hydraulic systems....esp if two helms.

I know why you're looking though, follow the raymarine selection chart & the price gets really scary for twin helms & large'ish rams.

Navman autopilot seems much more affordable at £1100 inc. pump, but haven't found much feedback for them.

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[insider]

Ok wheel pilots are merant for light displacement boats, which it is assumed do not have hydraulic steering, the concern is that if the boat is pressed to hard the steering will become so heavy that the moter will stall/burn out or the belt will slip [or in the case of the early wheel pilots the whole thing fall apart!!

however if the steering is light at all points of sail you can ignore the mfg recomendations, just be aware that a warranty claim might be rejected.
if you have hyd steering you will need to order a rudder feed back unit either type will do so thepilot knows where the rudder is.

re navman pilots excellent kit, free motor for up to 500cc capacity rams at this time,
giro type unit so vary good course holding etc. equal to raymarine type two spec.
down side is that it need the pump installing in the system so you need to brake and bleed the hyd lines.
better bet than awheel pilot given your size and weight[the boat]

<hr width=100% size=1>Logical progression is fault finding tool in every tool box.
Regards,
Insider

 

[dralex]

The rated loads are for sailing boats which load up on the helm as wind and heel increase. The increased forces needed to steer are a result of weather helm generated by the boat trying to turn up into the wind. This is not really gong to happen on a motor boat, so logically I can see few problems with using a wheel pilot on the hydraulic steering of a Mobo; if anything, the autohelm will have a pretty easy time.
Regards

Alex

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[MainlySteam]

Just to help the point I saw a Raymarine wheelpilot on a 100 foot tug a couple of weeks ago (hydraulic steering of course) and while I did not take much notice, if I recall correctly it was an ST4000. I think the main reason it was fitted was for a recent trans Atlantic repositioning voyage in which case an expensive fit would not have been warranted.

John

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[Rohorn]

Hi...Back to the ST 4000 I have on my cat, it responds to it's internal fluxgate compass heading, nothin' to do with knowing the wheel position. I don't know what sort of hydraulic steering you have. I've been looking at the VETUS systems for smaller boats and the steering wheel sits on the pump shaft and the oil goes one way or t'other depending which way you turn the wheel. Clearly there could be some slippage so if you marked the wheel it may not come back to the original absolute position, after a while, but so what? The autopilot drives to a compass heading, and will turn the wheel till it gets it.
I'm sure you could arrange a marker, or some indicator for a straight ahead mechanical position of the rudders, but I don't see the point. The boat's going to get blown around anyway, and the autohelm will correct according to the selected heading.
Correct me if I'm wrong, please.
Cheers...R

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[dick_james]

I've an st4000 on my 7.5t motor sailor. Bought it cheapish on e-bay, easy to fit, added rudder reference (essential with hydraulics) and remote control and it's truly wonderful. As others have said if your steering is always light you should have no probs.

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