I often get posed the question, “Do your plans come full sized or do you need to loft them?” I have to truthfully answer, neither, which often confuses people because they believe home built wooden boat plans are one or the other. In these days of computer aided design (CAD) drafting, no longer is it necessary to loft boat plans, because the computer actually does this for the boat designer. What this means to the boat builder, is that all they need to do is measure and mark, not loft.
Lofting is a process whereby the boat is actually drawn full sized to determine the exact sizes of the frames and components. Back when boat plans were drawn by hand in smaller scale, it was impossible to draw them accurately enough to ensure the finished boat had “fair” curves, that is to say, curves that smoothly transitioned from one part of the hull to the other. In the old days, a table of offsets or a half hull model was used to lay out several key points on the hull, and a long flexible piece of wood, called a spline was used to create a fair curve. From this full-sized drawing, measurements were taken to determine the exact sizes of the framing elements.
Enter the computer and Computer Aided Drafting (CAD.) This revolution in the boat designer’s world allowed the naval architect to use an infinitely large piece of paper on which to design his boat full-size. Some of the early versions of AutoCAD came with a full scale drawing of the solar system with all of the planets and moons. It was 93 million miles from the earth to the sun! It gave you an appreciation of how huge the solar system actually is. On the other hand, I have offset likes one millionth of an inch and was able to zoom in until the two lines appeared on opposite sides of the computer screen.
So, no, you don’t need to loft designs properly designed on CAD, and no there is no reason to need full sized plans or patterns, so long as you select modern plans by designers who use modern technology to design their boats. All plans from Spira International are computer generated for accuracy and pre-lofted in the computer. If you have selected plans from another designer, ask before you buy, “Are these pre-lofted or do they come full sized?” If neither, then you have a big job ahead of you and you better check a few books out of the library so that you can learn to loft.
Jeff Spira is a naval architect, marine engineer, writer and historian offering custom design easy to build boat plans at the Spira International website at: http://www.spirainternational.com. Learn about boat building including stitch and glue, download a free pdf ebook boat plan with illustrations, or watch Jeff’s boat building video as featured on YouTube.
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