Foil

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A surfboard's foil relates to how its thickness is distributed lengthwise from nose to tail. This term can also be used to describe the cross section of a board or fin, but most shapers use it to express the tapering volume of a given board.

Foils have changed dramatically over the past 15 or 20 years, perhaps more so than rockers or outlines. Few people realize that the advent of the three-fin Thruster design, which moved the rider from a central trim position toward the tail where he was to remain planted so as to exploit a built-in sweet spot, served to reverse the foil of the standard short boards of the '70s and early '80s completely. Prior to the three-fin, most boards were foiled so the thickness was placed in front of the wide point; often, the nose was much thicker than the tail (another cyclical reverse: most of the longboards in the modern surfing era had the thickness pooled well behind the wide-point). By the late '80s, the high-performance three-fin design had the bulk of the volume shifted behind the wide point, under the rider's stance, and the tails were appreciably thicker than the noses.

Where the thickness is placed on a surfboard is incredibly important. It is getting harder and harder to create original foils with today's foam blanks, as they are increasingly specialized toward contemporary design and have little in the way of excess foam (keeping with the trend toward stronger close tolerance blanks). As with most of the major components of a good surfboard, the foil should flow evenly and complement both the deck and the bottom rocker. Most thickness is pooled around the chest area to help paddling and flotation, and also because the bottom rocker has its apex or peak there. Ultra-thin, high-performance designs may often have a fairly uniform foil from nose to tail with little in the way of noticeable foiling. Thicker boards or specialized designs such as big-wave guns will often have to be intelligently foiled if they are to perform well.

A simple rule of thumb or two concerning foils: small-wave hotdog boards will often have the thickness placed aft, both to take advantage of the three-fin array and also to provide more buoyancy or lift in slower surf where the rider is trying to generate planing speed. Big-wave guns, on the other hand, require the opposite. The tail has to be thinner so it can bite and penetrate at high speeds; the bulk of the thickness is placed in front of the wide point so as to provide paddle power and a sort of centrifugal inertia as the nose carries through long, driving turns. This type of gun foil also better suits the rocker profile on most big-wave boards, which are traditionally straighter toward the tail and pushed up at the nose.

Try and spend a little time noticing the different way surfboards are foiled. The balance of the board and angle of attack at which it skims over the wave face has as much to do with its foil as anything. Look at the board from a side-on view, perhaps from a few yards away, and notice how the thickness flows from nose to tail. A proper foil should look as if there were a natural almost organic taper. Check out the lines described by the deck and bottom rocker and, with an artist's eye, appraise whether or not the foil tapers in harmony with them.

This is a good way to practice your eye, as most experienced shapers will usually look at a surfboard held side-on and appraise how nicely the rocker, rails and thickness blend together. This is how a surfboard's true pedigree is judged. -- Dave Parmenter, March 2001