Sunday, September 13, 2009

Lofting Ravn

Lofting a boat sounds simple: You plot coordinates from a table of offsets onto a sheet of plywood and connect the dots. Any fifth grader can do it, right? I should have hired a fifth grader. Without going into a lot of detail let me just say that I got through it, but it wasn't easy.

I love maritime traditions. One of them is that the table of offsets are done in feet, inches and eighths -- the first number is feet, the next number is inches and the last number is eighths, sometimes with a plus or minus which means add or subtract a 16th of an inch. I was pleased with myself that when I first looked at Valgerda's table of offsets and understood it. But when I actually started trying to plot points on the sheet of plywood I used as a lofting floor, feet, inches and eighths made my head hurt. I finally went into the computer, made a table and re-entered all of the table of offsets numbers translating them from the traditional into the practical, which, for me, was the number in the box looked exactly like the number on the tape measure. After I did that things went smoothly.

The only lofting error I made was when I actually drew the frames for station zero and station 12, which make up the first and last frames of the boat, they didn't look right to me so I changed them. I discovered the error before I installed the frames and fixed it. More about that later.

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