Excuse the dumb question. When i look at aircraft tailfins, yacht rudders and keels ect. they are all square tipped and relatively straight. Surfboard fins are virtually all raked and curved. (sharks, whales, dolphins ect. all like surfboard fins) Can anyone give an explanation? With thanks Alex
I have some “hooked” rectangular (sort of) side fins that will be put to use soon on a recycled paipo. I’ll be using 'em as twin fins.
Hey Alex, This is a big question and a guy could spend a chapter in a book trying to answer it. I’ll try and boil it down to something simple. Though I doubt if it’s possible. The fins under a surfboard are the there to maintain trim and affect turning facility. The straight lines on aircraft fins are very neutral in the water. They may let you good pretty fast but the don’t serve well when it comes to maneuvering. Drive the one of the key elements we strive for in surf fins. The arcs that are on the cetation’s and fish’s fins are there so direction changes can be better facilitated and deliver a better drive coefficient than aircraft wings are able to. The combination of the shapes that deliver hydrodynamic and aerodynamic efficiency is one the has the possibility of yielding something that may deliver a new cutting edge to surf-craft performance, however Nature’s been evolving the lines she uses in the water of this planet for a while and what she’s come up with must have some merit. She may have come up with some other ideas on some distant one but personally I think the form and function must very similar there as it is here. Mahalo, Rich
Thanks Halcyon That’s what I thought about the shark, dolphins etc. I was ready to experiment but i didn’t put a fin box in so with permanent fin I thought I had better stick to tradition. I suppose your point is that aircraft have movable tabs for direction change and yacht rudders pivot also, where as our fins have to perform the dual function of stability and turning. thanks for your reply.
dewey weber hatchet fins look like tail wings.