You also need to allow room for waves crashing over your bow to pass easily under the foot of the sail, and you need the clew low enough so that you can adjust the leech line without hanging over the lifelines. My ideal sail is one that has the clew high enough so that there is good visibility under the sail but low enough that the sail retains some of its performance ability. The problem is that high-clewed sails are fairly inefficient for windward work, although they are fine for reaching and work well with a staysail. With a high-clewed sail, on the other hand, you can reef the sail and even without much adjustment to the lead position you will end up with a decent sheeting point. On the down side, the moment you reef the sail, your sheeting position changes (Figure 7.8) and unless you have a way of adjusting the sheet lead, you quickly lose all performance. A low clew, for example, provides the best upwind performance since the shape is more consistent throughout the sail, the center of effort is lower and you have a short, sure sheeting point. For most cruisers the clew height should fall somewhere between the two extremes, since there are benefits to be gained from each. In the end it really depends on your sailing plans and the kind of boat you are sailing. Those with a racing bent like it low, whereas classic cruisers, for example, those with traditional-looking schooners or cutters, like it high. Each sailmaker has his own idea of where to place the clew. Start with a sail that has the correct clew height and then modify your deck layout so that you can move the sheet lead position to accommodate clew location as the sail is reefed. You cannot do much about this, but you can modify your deck layout to ensure that your genoa is trimmed properly and performing effectively. Furthermore, as the clew rises the center of effort gets higher as well, precisely at a time when you would prefer to have it lowered to reduce heeling moment. Therefore, as soon as you roll the sail up, even a little, you roll away the ideal shape and end up with a compromise. An average headsail has the maximum draft located at a point about 33 to 38 percent aft from the luff. The moment you reef a headsail you lose some of its design attributes, and if you view sail efficiency as part of overall seamanship - which you should - then finding ways to improve the performance of your headsail is important.
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