Here are a couple of other uses for vector diagrams beyond the issue of sail twist in my previous post. I leave this an exercise for the Type-Anals like me. Vectors are defined as having both magnitude and direction, and magically work for both velocity and force. Vector diagrams can be used: 1) to show why when sailing to windward and you are hit with a gust of wind, the apparent wind suddenly appears to swing aft. To compensate, you head up or drop the traveler or ease the mainsheet. I suggest that the affect of this compensation is to get back to the angle of attack that you had set before the gust hit you, and perhaps even less angle of attack to further reduce the power of the sail during the gust. 2) to show how much of the force of a boom vang is pulling down on the boom and how much is pulling the boom into the mast, potentially bending the mast and flatting the main. These components vary with the angle of the vang (determined by where it attaches to the boom). A rigger told me it should be in the range of 30 to 45 degrees to the boom. At 45 degrees, the two force vectors are equal. 3) to show why forestay tension is greater than backstay tension. Assuming a masthead rig: Hint #1: because the mast is closer to the forestay, the forestay is more vertical than the backstay. Hint #2: the fore and aft horizontal force on the masthead are equal. 4) to show why it takes a tack of 90 degrees to move the masthead windex only 60 degrees. When close-hauled and the windex showing about 30 degrees off the wind, the true wind is more like 45 degrees (using my numbers of 6knots boat speed with 10 knots true wind at the deck). When tacking, it takes a turn of 45 degrees to be head to true wind, and another 45 degrees to get the same close-hauled setup on the other tack. A beam-reach to beam-rach tack in this case could be a turn of 220 degrees, not 180! Hmm, maybe a 140 degree gybe would be faster... May the Vector Force be with you. ...RickM...
