Steering: mechanical rod/gearbox vs. hydraulic

[JerryHawkins]

Currently have a Whitlock mamba-type steering system using bevel gearboxes and link rods and am considering switching to hydraulic.

Reason for this is I want to fit a "below decks" autopilot system and hydraulic makes this easy. Although the existing system can be back-driven, it would use up a large part of the ram's force to overcome it before the force required to turn the rudder in any given situation.

I am looking at 3 options:

1. Fit electric mechanical linear ram to existing rudder arm.
- backdrive load is a problem here plus fitting hassles
2. Replace one of the bevel boxes with a Whitlock mamba bevel box and mamba drive motor.
- most expensive, but simplest to fit
3. Replace with hydraulic steering system and use electric hydraulic pump.
- would lose "feel" through the steering plus hassle to change to this system.

Does anyone have any comments on the pros and cons of mechanical versus hydraulic or any ideas on which autopilot drive system would be best? I am currently leaning towards option 2.

The boat in question is a Colvic Watson 34'6" motor sailer displacing some 15tons.

Thanks all!

Jerry

 

[claymore]

I don't think you need worry too much about the loss of feel - Claymore is slightly shorter an lighter than the Watson but there is plenty of feel in the hydraulic steering system. There is a reduction valve/box thingy which means that we have around 4 full turns lock to lock.
I have a vetus autopilot which works OK - it wanders around a bit but I think that is more to do with propwalk and keel configuration - and sail plan of course.

 

[srm]

I have hydraulic steering on my Prout cat. Two rudders feel odd with a mechanical linkage to a wheel anyway as they kick at different times so the fact that the rudders can not push the wheel is a benefit. I like the fact that the wheel and rudders stay exactly where I place them without having to lock the wheel - useful when manouvering single handed as the boat will continue its turn or run straight while I attend to something else.
Have not had any problems with the system and provided it is properly sized to the boat / rudder combination and you avoid oil leaks there is very little to go wrong. Contrast this with the gears, links, chain, blocks and wire in a mechanical sytem.

My boat came with a wheel drive Autohelm plus rudder sensor to allow for hydraulic slippage between wheel and rudders. That also works well but is heavy on power when sailing so I fitted a tiller and Monitor wind vane gear. When using the vane gear the hydraulic ram is disconected from the quadrant, although in strong conditions the wind vane servo will push the hydraulic ram if the bypass valve is open.