Self Steering

[jyow]

I was sailing my CS17#102 "Lady Blue" yesterday afternoon in Galveston Bay in winds 7 to 10 knots. I decided to see how she would self steer. I trimmed to the course I wanted and then let go of the tiller. She did wonderfully! If I wanted to change course, I just re-trimmed the sails and she stayed perfectly on new course. I sailed on various courses from a close reach to a near run and always had good results.

Every time I sail this boat, I am more impressed with its qualities! I may never own a sloop again!

John

[JeffM]

I've had the best luck at a close reach. It's amazing if you can get self-steering at a run. I sometimes have to wrestle just to keep on course in a following sea.

[Howard]

On a run, if there is any loading on the main sheet at all....a sheet to tiller setup might work.

Basic idea is to bend a line to a fall of the mainsheet, the line then runs to a block on the weather side, about even with the tiller, then to the tiller. An offsetting bit of elastic tubing balances the pull. If the main were to get blanketed by the mizzen, it goes slack and the elastic pulls the tiller over. If turning to weather, the main tensions up, pulling the tiller back to weather. On a sloop, when it's all working right, it sets up in an equalibrium and it's like riding a rail. But it does take some tension in the sheets to power it up.

Going to weather, you would use the mizzen sheet to do the same thing, although it sounds like you can trim the sails to hold a pretty good course. That is hard to get any sloop to do well. They will wallow along in a general direction....but seldom do they track straight.

[jyow]

Jeff, I was not really on a run, rather a broad reach and the boat steered well.

By the way, thank you for the information on your dodger. If I decide to put one on, I will probably go with Graham's design.

John

[JeffM]

Howard, someday I'm going to have to try that just for fun. My guess, though, it that with the following waves common here the response would be too weak and too slow to hold anything resembling a course. On other points of sail, I'm guessing the line from the mizzen sheet would go to the lee side of the tiller, and the mizzen would be sheeted a little loosely?

John, I'm still impressed. You're welcome for the info. I'm still messing around with ways to keep kids, etc. dry, but don't think any dodger that doesn't have some kind of walk-through will work for me.

[Howard]

Jeff:

Don't know how it would work on a cat ketch, but on a sloop, the general principles are:

Wind forward of the beam, use the aft sail (mainsheet on a sloop...mizzen on the cat ketch). Wind aft of the beam (sail operating in drag mode...as opposed to a lifting foil), use the forward sail (jib sheets on a sloop.....main on a cat ketch). Rather than bending to a fall of the sheet, you might be able to run the windward sheet through blocks and tie it directly to the tiller. That might get you the most power, if power is what you are lacking. Elastic balances what power is generated. All the way from a very puny little bungy cord all the way up to one or more pieces of rubber surgical tubing. Getting the power from the sheet balanced with the right about of elastic is the key to getting it to work right.

In both cases, the elastic goes to the lee side. Getting that wroing will mess things up in a hurry. :shock:

[JeffM]

Howard, I'm still not getting it. I'm trying to understand this as a feedback system in equilibrium. For example, my boat will self-steer pretty fairly (though not be especially fast) at a close reach by the simple act of bungeeing the tiller just to windward of the centerline: weather helm tends to pull the tiller a trifle to lee, the boat gradually rounds up until pressure on the rudder is reduced and the bungee pulls the tiller back over to head the boat back down again, pulling the tiller back to lee, and so on. The net result is a slightly scallop-edge boat track as the boat gradually rounds up, heads down, rounds up, etc.

I can't see how running either sheet to pull the tiller to windward (opposed by elastic to lee) would work. Seems to me that full sail pressure would continually turn the boat further away from the wind.

All this is pretty academic, since I don't expect ever to need to self-steer for any long period in the Bay, but I've been curious about how it was managed ever since reading Joshua Slocum.

[JeffM]

Thanks, Brad! I've added that book to my (voluminous) wish list.