boat

Published on June 2017 | Categories: Documents | Downloads: 102 | Comments: 0 | Views: 988
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outrigger thick hull

Height about 18 feet Flat bottom

This analysis shows that for a hull of uniform cross section floating in still water, the ellipse has by far the least amount of wetted surface for a given displacement/weight. It also shows that the triangular hull shape is by far the worst. The rest of the shapes are comparable. However, minimizing wetted surface area is not the only consideration when designing a hull. Since in reality the hull will be traveling through waves, a sharp hull shape will offer less wave resistance and a smoother ride. Based on these results I decided that the nacra hull shape (closest to the ellipse) was indeed the best shape and so I stuck with it. However, it does seem that the curved triangle shape, while it does possess an 80% increase in wetted surface area, could produce a very smoothly riding hull that would not require a skeg or dagger board and the extra drag associated with such foils (see the G-cat design). This shape seems to have a lot of potential for a cruising cat and after seeing how hard it can be to bend plywood around tight radii, I can appreciate how much easier it would be to build using plywood. Here is a Pugh chart weighing each shapes pros & cons with my own weighting system, looking back now, I think I would go with the curved triangular hull if I build another cat.

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