22 DEC 2009:The weather was supposed to be overcast, so I decided to do a short sail in Hillsborough Bay rather than a longer sail in Tampa Bay out to Edgemont Channel. There was also the indication that the wind would be a steady 10 knots from the east, which meant that I could sail north up Hillsborough Bay on a long beam reach to Davis Island and back. Two goals would be accomplished; a) I would get a chance to look at the approach to the Davis Island boat ramp from seaward and b) I would get a chance to try a self-steering idea that I'd read about.
Anyone who has sailed a small boat single-handed will understand the need for some way to let the boat sail it's self. Whether its to fix something or just sit back and enjoy the sail without constant adjustment of the helm, the ability to just let go of the tiller without bad things happening is really nice. During the summer I had tried lashing the tiller with some success. In steady winds the boat holds course. But the slightest gust will have her turn up into the wind. Lashing the helm can only give you a short amounbt of time to deal with problems forward or to provide your arm some relief during a long sail.
I decided an auto-helm or a wind vane would be overkill on a small 20' sloop, so I looked into sheet to helm steering. Essencially, this means attaching the main sheet to the tiller and off-setting the pull with elastic of some sort. I learned about how to do this mainly from John Letcher's book, "Self-Steering for Sailing Craft". It's a great book and goes more in depth than I really needed, but he actually sailed across the Pacific using this meathod, so I thought he'd be a good guy to listen to.
The set-up is different based on the wind, but basically the elastic is tied off on the leeward side of the boat opposite the helm and then lashed to the tiller. A 1/4" line is then made off to the main sheet with a rolling hitch (or using a snatch block), then through a block opposite the helm on the windward side, then lashed to the tiller. The helm is balanced through trial and error until in a steady breeze, the boat will hold her course. If a gust comes up, the force of the wind on the sail will tighten the main sheet, pulling the helm opposite to and counteracting the force of the wind. If the wind lessons, the elastic will pull the helm back. The boat stays on course because of the two forces acting against each other. 
John Letcher suggests surgical tubing makes the best elastic for the purposes of self-steering. He indicated that surgical tubing, though it degraded in the sun, did have the right amount of elasticity. I didn't have any surgical tubing. However, I did have a bungee cord and tarred seine twine. I figured if you have a bungee cord and seine twine you can do just about anything. I was wrong in this instance, but it usually is true.On the way north toward Tampa, I didn't try to use the self-steering, I just enjoyed the sail. The sun was out, the wind was a steady ten knots and I sat back and enjoyed holding the tiller and getting used to the feel of the boat again. However, on the way back I decided to try the system.
I let out the mainsheet, so the main sail leuffed a little. Then I hooked the bungee cord to the leeward aft cleat and looped it around the tiller. Then, while trying to hold the boat more or less on course, I tied a rolling hitch with the 1/4" nylon line around the standing mainsheet, put it through a block attached to the windward aft cleat, pulled in the main sheet until it filled and then wrapped the tail line around the tiller. Unfortunately, it didn't work, though I saw why it should and probably will with different materials.
I tried for the better part of an hour to balance the pull of the elastic against the pull of the wind on the main sheet. The bungee cord was too strong though. Maybe in high winds 20 knots or better, the bungee would have worked, but I need something just as elastic, but not as strong.
Surgical tubing ....
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