Ken: Any listers who have my book and chart could answer this question by going to page 11 in the book and page 1 in the chart. Draft depth is described as a percentage of the sails (main or jib)width or depth at its widest point, which is the deepest part of the sail. Using a percentage may appear complicated but it works. Say your chord line is 10' long and the distance from the chord line to the deepest part of the sail is 1' then your draft depth would be stated at 10%. If the distance was 3' then the draft depth would be described as 30%. Lets say you don't want to mess with the chord line, which is ever changing, what can you use to get into the ball park? The answer is use the length of the foot of the sail. Ken, using the above example of 10'chord or boom length, 6" of draft depth would equate to a draft depth depth of 5%. If you were sailing in very light wind then that position would be right. If they actually ment to tell you that 6'(60%) would be the max draft depth they would be off by about 30%!! In general, 25% to 30% is the max you would ever need. Here's how draft depth works. In very light air you want the flatest sail you can get because the wind does not have enough power to get around the sail and it stalls. That is why sailors who put belly into their sails don't go anywhere in very light air. They think bellying out the sail will develop speed and it does not happen. Next time your out sailing try it and see what happens. As the wind starts to pipe up you gradually want to induce more belly (equates to more power) into the sail. At about 10 knots you want to start reducing the power of the sail by starting to flatten it. After about 15 knots or so you want to really flatten the sail to reduce power. So you go from flat to belly and then back to flat. That's how it works. The outhaul is not the only draft depth control. Mast bend is the other. I don't know what kind of a boat you have and you may not be able to bend the mast. You may only be able to rake it back, which has nothing to do with draft depth. So know you know how to work the outhaul and all you have to do is experiment to get the proper setting for each point of sail and wind condition. The problem is that there are 3 other elements that you have to mess with in addition to draft depth and they are draft position, twist and angle of attack. They have their settings for each point of sail and wind condition. You can't just mess with draft depth and expect to get 100% efficiency from your sails. Those of us that remember cars that had carbs with adjustable jets are aware of how important it was to adjust ALL the jets. Younger folks don't know about that. In other words, all the sail trim controls for the main and jib are there for a reason and you have to use all of them to get top performance out of your boat. Hope this helps. If you have any other questions just fire away.
