Fins

Rusty cuts through the science of finding the right fin.

"When I'm designing a board I always contemplate the fins -- the number of fins, the shape of the fins, the size of the fins, the relationship of the fins, where they are positioned with respect to each other, the rail, the nose vector. They are not always the same size or template. In fact, I've always been a firm believer in mixing sizes, foils and flex to get a desired effect."

World Champ Mick Fanning, tuning up with his trusty thruster. Photo: Jeremiah Klein

FLEX

"Flex is so crucial. Not just the amount of flex, but the quality of the flex. Where is the fin bending? Base-to-tip flex? Torsional flex? How quick does it rebound?

Small mushy day: Try fins with softer flex. Try front fins with some base and extra area. A more pivoty, triangular outline, a heavily cambered foil, and a back fin with a little less area and depth, and move it up if your system allows.

The surf is cranking: Run smaller fins up front, preferably with a little more rake, and stiffer flex. It would be good if they had a slight radius to the leading edge. Place a larger, more dominant fin farther back on the tail for control and holding power.

Lighter surfers in smaller weaker surf will usually benefit from a fin with softer flex. Softer fins will help the board feel looser. It will help to initiate turns but isn't necessarily a dynamic solution. Soft, as in "bendy" plastic, helps start a turn but there isn't a lot of return. You may find yourself double-pumping to try and keep your rail set or struggling to project where you want to go.

Another symptom of a fin that is too soft is that it will wash out on turns, especially on a cutback or coming off the top. Coming off the top you should be able to accelerate. A soft fin will slip a little and throw your timing off. A quality glass or composite fin may have a firm base but a "softer tip" and what you should be looking for is a crisp rebound on that flex. A fin that is soft, generally speaking, spills a lot of the power you put into a turn and slows reaction time out of the turn."

Dave Wassel is no small dude. Bigger guys tend to favor a more rigid fin. Photo: Jeremiah Klein.

"Conversely, larger surfers in more powerful surf will be happier with a more rigid fin. Too rigid is no good. A turn is a complex thing that takes everything working in harmony to maximize the return on effort. A good hull will have certain flex attributes and it should be married to a fin with complementary qualities. As you load the board in a turn, so too should the fins be storing energy. As you follow through on your arc and start to unweight, the power of the wave and your energy being returned should flow together. You should feel a launch out of the board and the fins should contribute to that launch.

A lot of companies offered up carbon fins over the last few years. In some cases this was primarily to overcome the shortcomings of the method of attachment or inadequate plastic. There are some composite fins that combine a lightweight, cor-mat filler, fiberglass cloth and carbon to create a light, strong fin, with a variety of flex patterns. Carbon has "Tech Appeal" but needs to be used carefully and sparingly so as not to overcorrect the flex shortcomings of other materials involved in the construction.

Fins in the past were cut out of panels of fiberglass laid up in many layers. A finished fin is in the range of .22 to .35 of an inch thick. Personally, I lean towards a thinner fin, as I believe they go through the water faster. As long as flex and foil are not compromised by going thinner, it is usually a good thing.

Panels are laid up usually with six-to eight-ounce cloth, and possibly some glass mat as filler. Think of the finished panel as something similar to plywood. The more layers, the finer the cloth, the more control you have over foiling detail, less resin (resin is rigid), more strength, and more control over the flex, and to a certain extent, a lighter fin. This is why in most cases I like four-ounce panels."

GLASS-ONS VS FIN SYSTEMS

"How a glass-on fin is attached can have a lot of bearing on its performance. The amount of cloth used and where it is applied has an impact on the final product along with how the sander finishes it off. The sander as well as the overall foil and taper of the fin impact the leading and trailing edges."

Standard glass-on fins. Photo: Jeremiah Klein

"I think when a fin is glassed on it creates a very subtle "vector" contour on the inside of the fin. Technique varies from glass shop to glass shop but usually a few cloth ovals are run up both sides of the fins when they are glassed on. If you were to run a straight edge across the inside of the finished fins, you would probably see a slight convex to concave change on the inner part of the fin.

Fin system box failure can be devastating and difficult to repair, especially on the road. Glass-ons, on the other hand, are usually not that difficult to reinforce or re-attach. A lot of pros simply feel that glass-ons add something, however difficult to articulate, to the board's performance.

There is an on-going dialogue about the effect of having rovings or a filet at the base of the fins. Many competitive surfers feel that the radius at the base of a glass on fin adds some intangible element of flow, or that the fins being glassed on creates a "oneness" in terms of how the sum of the parts is greater than the whole.

Personally, I think a lot is lost in the inability to fine-tune performance by changing out fins. Years ago, a visiting pro who was in town for a major tour event got a new board and could tell he really liked the hull but the fins weren't quite right. We cut those fins off and glassed them back on four different times in four days before he finally declared they were right...he did end up getting a good result in the contest.

If you really think the transition at the base makes a difference, run a bit of silicone or something similar along the base of the fin if you are worried about the feel of a transition curve. But the ability to change out fins based on conditions is invaluable."

WHAT WORKS FOR YOU

"Fins for most people have always been an afterthought. Even a lot of experienced surfers trust their shapers to guide them. There are a lot of shapers that simply don't have the experience to give their customers a good overview.

We do demo days from time-to-time and some of the fin companies will participate. These events are real eye openers for most of the people who show up but it's very difficult to reach many surfers this way."

Freddy P, putting his fins to the ultimate test. Photo: Jeremiah Klein

"A surfboard may cost you $500 to $900. You may get fins included with the board. In most cases, these will be molded plastic fins. They may be OK but chances are you can do better. A good set of glass or composite fins will be an extra $70 to $100 more.

Don't be afraid to try something new. Take a few sets of fins to the beach and switch out during a session. You can get many different feels running different fins on one hull. There is no better basis than actual experience."

Parts of the above are excepted from the Surfer's Journal vol. 15 #6

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