Our cruising plans include two months this summer on the West Coast of Vancouver Island and four months in the summer of 2005 up to Glacier Bay in Alaska. Both areas are well known for feisty winds. Forecasts being what they are, I figure we have a fairly high probability in getting caught out in some 35 plus knot winds at least for a few hours on more than one occasion. This has me looking at alternative sail configurations for getting shorter when the winds start to blow. My preliminary conclusions which include purchase of a Gale Sail and having a very deep third reef put in my main are as follows: 1. The nominal sail area of our H37.5 is 704 square feet with a 100% foretriangle. With our 130% genoa, I figure this comes out to 804 square feet which I'll call the base case. 2. A single reef in the main cuts this back to 742 or 92%. 3. Rolling the genoa down to 100% gets us down further to 642 or 80% 4. A second reef in the main further shrinks the sail area to 571 or 71% 5. Rolling up the genoa and replacing it with a 100 square foot Gale Sail drops us down to 341 or 42%. (There's certainly an intermediate position here, but I don't think much of the sail shape of a genoa furled down very far, particularly for upwind work.) 6. Puting a deep third reef in the main (25 foot luff, 10 foot foot ((that's not the same as a square foot!)) gets us down to 225 square feet or 28%. 7. Sailing with only a Gale Sail would take us down to 100 square feet or 12.5% Assuming that makes sense as an orderly regression in sail area, the next question becomes, just how much wind does that allow you to handle comfortably and still have enough power and control to claw off a lee shore and/or steer into and around waves? In his book Surviving the Storm, Steve Dashew suggests a model which he credits to yacht designer Angelo Lavaranos. Dashew says that for any given wind, the heeling force is a function of the square footage of sail up multiplied by the leverage arm which he defines as the height of the center of effort of the sails above the waterline plus 40% of the boat's draft. Assuming that's true, if you know the sail square footage and leverage arm that's comfortable for you at a lower wind speed, you can project how much (or little) sail you need up at higher wind speeds. On our boat we can handle 15 knots apparent comfortably with our full sail plan without dropping the traveller or easing the mainsheet. Beyond that the inclinometer reads more than 20 degrees and the Admiral begins to complain. Let's assume that the wind's force is one pound per square foot at 15 knots. (The absolute force number is unimportant, but the relative numbers are very important.) I calculate the height of the center of effort of our full sail plan at 23.5 feet above the water line to which we need to add 40% of our draft or two feet for a total of a 25.5 foot leverage arm. Multiplying this by the 804 square foot sail area and a wind force of one pound per square foot yields a heeling torque of 20512 foot pounds--a number with which we're comfortable. If the apparent wind doubles from 15 to 30 knots, the force of the wind increases as the square of the velocity increase from one pound per square foot to four pounds per square foot. To maintain the same heeling torque, the product of the sail area in square feet and the heeling arm have to be reduced by 75%. Sail configuration 5 above which is the double reefed main with a Gale Sail has a square footage of 341 with a lowered center of effort and reduced heeling arm of 18 feet. At four pounds per square foot wind force, this results in a heeling torque of 24552 or about 20% more than desired. If the model is right, we'd be easing the traveller and mainsheet at this sail configuration and wind speed or looking to scale down still further. At 45 knots the apparent wind has tripled compared to our base case so the wind's force has increased nine times to nine pounds per square foot. Our smallest sail configuration is the Gale Sail only with a sail area of one hundred square feet and a heeling arm of 13 feet. Total foot pounds of heeling torque with just the Gale Sail would be 11700 pounds well within our tolerance--we might even want to look at sailing with the triple reefed main, though that would involve dousing a hanked on jib on the foredeck in 45 knots of wind. In theory the gale sail configuration alone should handle 60 knots--I don't want to try it in practice. I'll freely admit to being "over the top" in analyzing this. Sorry, that's just me. Would like some input on a couple of issues: 1. Do you think the Dashew model has validity? 2. From a pragmatic standpoint do the sail reduction options make sense up to apparent wind velocities of 45 knots or so? Gary Wyngarden S/V Wanderlust H37.5
