Finology

In spring of 2006 I was a teacher’s assistant for freshman biology at William and Mary.


It was fun, but commuting from VIMS to the W&M main campus sucked time out of my schedule. I was having to work later at VIMS and become more opportunistic with my windsurfing sessions. Fortunately I found a launch on the James River near the Jamestown Ferry (somehow I felt I belonged there :P) where I could grab a quickie on the way home from TA’ing. I was cruising along there one spring afternoon when, “WHAM!” I hit something underwater and the board immediately skidded out sideways. I knew I had lost the fin. Retracing my steps in the muddy chest-deep water I found the culprit- a barely-submerged piling. Unfortunately I couldn’t find the fin- it was gone forever. Sailing back to shore was nearly impossible, because the board kept sliding around uncontrollably.

The whole point of that story was to illustrate why you need a fin; you need it to be able to go in a straight line. When the wind blows in your sail it wants to push the board sideways, but resistance from the fin balances out the sideways force so the board goes forward instead. Aside from that basic function, the fin also helps with planing, sailing upwind, and carving into a turn. With big sails you need a big fin to keep from side-slipping, and with small sails you need a small fin to go fast and stay in control. In addition to fin size, there are a lot of nuances of fin shape that also affect performance. I’m going to talk about some of them in the context of the fin “quivers” I have for each of my three boards.

Fins for the big “Kona”:



The Kona came with the white and blue fin on the right. It’s tall and relatively straight for power and efficiency, but it’s a little curved at the tip to help with turns. I really like it, but you can’t use it when there is eelgrass drifting in the water. The eelgrass gets wrapped around the fin and disrupts the water flow, making you skid out. That’s why you need a slanted “weed fin” like the one on the left, which lets the eelgrass slide off the tip. A weed fin is less efficient for its size than a regular fin, but it’s like... uhh... a totally mellow ride, dude.

Fins for the medium “Skate”:


The fins for my mid-sized shortboard are basically the same as the fins for the Kona, but scaled down a bit in size. I have two non-weed fins because I got one for free from UNC professor John Bruno when he switched from windsurfing to Kiteboarding.

Fins for the small “Banana Board”:


All these fins are much smaller than the ones for the Kona and the Skate, because they are meant to be used with small sails in high winds. The one on the left is a weed fin, with a little extra curviness, which is supposed to make it turn nicely in waves. The one in the middle is a basic wave fin that is made for sharp turns, and the one on the right is a combo of a go-fast fin and a sharp-turn fin.

If you're a windsurfer wondering what kind of board, sail or fin would be best for you, check out this automatic windsurfing equipment calculator.