Re: Which Autopilot drive Rotary or Linear?


Ian Park
 

I don't have any technical knowledge, just my personal experience. My previous boat had a Raymarine linear drive on the quadrant. It performed well, but after 10 years needed refurbishment of the heavily worn gears. The boat weighed 7 tons on a semi balanced rudder.
Our Santorin, same as the SM, does not have a balanced rudder and weighs in at just over 15 tons. The steering is very light (quite a high gearing and consequently not much 'feel' to the wheel), so is very easy to turn in heavy seas etc.
I only have the Raymarine rotary drive, plus a spare drive unit which I can swap in 10 minutes (and a Hydrovane).
The chain drive can be noisy, but on off wind sailing in a small sea we can put the response level down to 1 or 2 (on a 9 point scale). Otherwise it tends to stay on 3, sometimes 4. In heavy seas going downwind we have to turn the response rate up to 6 or 7.
I know people find the chain drive noisy and have a switched linear drive to a linear one on the quadrant (which can be noisy fir someone off watch I the aft cabin.
I am guessing from my comments that there is less pressure on the linear drive system because of the easy steering gearing. So it may come down more to the noise factor on extended passages whether you choose just one or both versions. The backup, however, is very reassuring.
I don't mind being kept awake at the wheel on night watch and on our Santorin we always sleep in the calm of the aft cabin!!

Others will have better technical advice. Good luck!

Ian

Ocean Hobo. SN96

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