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Sail Seminar - by Don Campbell

Our Sail seminar last month was slanted a bit to racing. The principles that make sails operative for making boats move were discussed.

 I used the chapter on Sails from Stuart Walker’s (ed) book The Techniques of Small Boat Racing, written by Colin Ratsey as the basis of the discussion. Ratsey was a well known sail maker from New York City of sails for I 14s and America’s Cup boats. He also made sails for Alberg 30’s as I have a suit of those sails on #469.  The interesting thing about I 14’s is that while they are just 14 feet long,  they can attain velocities of 25 knots, so sails  and balance do matter a fair bit on these boats.

Theory of balance and sail design were discussed  so the idea of design and power were linked and how to get the most out of sails when one needs it  as well as how to get rid of some of that power if you don’t need it. Vector resolution is important for good power. Since there are more than 10 sail controls for each of the main and foresail and more for the mainsail, there are very few instances when any two boats will be exactly the same for sail trim. Thus, the possibilities for sail trim for your boat and how she reacts to trim differences are important to understand and some controls are better or faster than others. Changes from top to bottom also matter depending upon wind and boundary layer conditions but that is a decision that cannot be made anywhere but on the water with sails up. And how to trim for that was covered in the discussion. Markers that indicate how the air is moving were also emphasized so that you can get an understanding of what is being developed from watching telltales. Have you enough on your sails and are they correctly placed to indicate to you the air conditions that you have?

Following the norms of many sail makers, the starting position for a mainsail is to have the leech fairly tight and the top batten level and parallel to the boom. With a fore sail, the normal starting position is to have the angle at the clew bisected by the sheet and to have both halyards just tight enough to take out any wrinkles.  The fullness and draft positions are then determined by outhaul and track position coupled with backstay/forestay tension. Since most sail makers design sails for the normal sailing conditions of an area, this often amounts to wind speeds of 10-14 knots and so sail sets in those conditions match the design. Below and above those wind speeds for which the sail was designed, adjustments are required to develop more power or less, while maintaining sail balance with the boat and wind conditions. It helps if you know what sail trim adjustments make those changes and have the tools on the boat to make those adjustments at the time they are needed.

Going fast is not only for racers, but also for cruisers and pleasurable days when you need to beat a sudden weather event that crops up in a shorter time than you were expecting. Being able to get the most out of the old girl when you need it is a comforting situation to be in under  those conditions which we all face and have all been in at one time or another.
This seminar will be continued on the water at the Whitby Weekend July 4, so you can see how things move on a sail and if you cannot get there by boat but want to experience some sail trim observations, make sure you just get there.

Many of Stuart Walker’s books are now out of print but occasionally come up for sale on used book
websites for very reasonable prices.

His Manual of Sail Trim is still published by Norton of NYC and I find it to be a very good primer for any sail boat sail trim. Those of you who read Sailing World with any regularity will probably have seen some of Stuart Walker’s writing.