IOMICA Forum

I know nothing of boat design, but I was curious why parallel keel fins are preferred (with the exception of Bantock's double taper design) over nearly any other design? Is there a performance advantage to be gained, ie ability to make the fin narrower (6% fins seem to be the rage)?

Thanks.

Brig North

My opinion.... they're simly easier to manufacture, and there's not enough difference in performance between the types to mess with the hassle. if one was absolutely better than the other, the slower ones would become obsolete, and that's not happening. There are many good fins of various shapes and sizes out there doing the job. The scientific numbers would say that a double tapered fin would have less drag, but actual race results do not seem to make one faster than the other. My limited testing has shown that the airfoil shape is much more important than whether it's tapered or not.

Steve Landeau wrote:The scientific numbers would say that a double tapered fin would have less drag, but actual race results do not seem to make one faster than the other

In theory, the tapered fin should show slightly less drag because it sheds a slightly smaller vortex at the tip. Perhaps the bulb makes a sufficient end plate to a parallel fin so that the difference in tip vorticity no longer makes a practical difference.