Q&A: Which Autopilot Drive?

Question: I am planning a long trip in June (Sardinia to Canaries) and then the ARC in November. A working autopilot would be nice. I’m looking at Simrad autopilots. What drive would you recommend for a Swan 44 (displaces about 30,000lbs)?

Answer: Your Swan is a big powerful boat and you are planning a downwind trip in big trade wind seas that will challenge your autopilot. (Autopilots are much more heavily stressed downwind than going to windward.) So I would recommend putting some time, effort and money into a really bomb proof installation of the new drive.

Here are some thoughts to keep in mind when selecting a drive:

  • I think that, in general, hydraulic drives are more reliable than electrical (that is, an electric hydraulic pump driving an hydraulic cylinder).
  • When selecting the pump/cylinder set, go big. I think autopilot companies often underestimate the loads on a voyaging sailboat.
  • Vendors sometimes specifies two rams to get the power they need on bigger boats. Except for the largest boats, I don’t like this approach since it adds another level of complexity and more seals and hoses to leak and blow.
  • Make sure that you, or whoever is installing the drive, uses the correct sealants properly applied on all hydraulic joints. It is amazing to me how many experienced technicians that should know better will use ordinary pipe dope on the joints. This is the reason that many users of hydraulic autopilot drives complain of leaks.
  • The mounting points for the ram must be truly massive to take the load and there must be NO play or slackness anywhere.
    • Here is a test:
      • After installation, engage the autopilot and then have someone try to turn the wheel back and forth against the ram using the same amount of force as you would steering in big seas broad reaching.
      • While they are doing that, look at the complete installation. If there is ANY play, flexing, or other movement, it is not strong enough.
      • By the way, if the boat’s steering can’t stand this test, it should be beefed up too.
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