33 Years later...

This article was shared by Stu (UK). Interesting 33 years later to see how the promise of flex has gone largely unfulfilled, and how rumors of the death of foam were greatly exaggerated.

Knee-riding is part of the new surfing revolution. It is not just an easier, more portable way of surfing--like some of the old paipo boarders claim. And it's not just a way of "reducing the medium" to get more involved with the wave.

Knee-riding is a highly intricate and sophisticated aspect of surfing. It is changing every day because of the great number of knee-riders who aren't satisfied with what has happened in the past. They are individuals who have separated themselves from traditional knee-boarders and are seeking a new direction in knee-riding.

Within the last year and a half, there has been a change from two small fins to one large fin. Soft, egg rails have been replaced by thin, hard rails. The bottoms have become very flat to increase speed potential. Fin boxes have been added to the tails, and signature models have crept into the now commercialized knee-board scene.

In spite of all the improvements, the conventional foam knee-board seems to be dying a slow death because of the increased interest and speculation concerning the flexible knee-board. Some say the flex-board is too specialized to make it on a wide-sell basis. Others say the knee-riders are demanding a flexible board whether they know how to use it or not. The general consensus seems to be that foam kneeboards will be around for a while because of their appeal to the novice and average knee-rider, while the flexboard will be more popular with the experienced knee-riders.

There are many types of flexible knee-boards, all seeking the same pot of gold at the end of the rainbow--increased speed and maneuverability. Flex-boards are designed to allow the bottom of the board to stay flush against the face of the wave. This is accomplished by allowing the part of the board that is most involved with water contact to flex (bend) with the curvature of the wave. By flexing with the wave, the board eliminates most of the speed-reducing drag that occurs on conventional foam knee-boards.

 It is said that when a board flexes in the water, a variable rocker (changing bottom) effect takes place on the bottom of the board. It is important to remember that the amount of flex designed into knee-boards is not the only thing that will determine their speed and maneuverability. Others factors such a rail line, bottom contour, length, width, etc., also play a tremendous part in the way a knee-board will handle.

As a result of extensive experimentation, three major flex-board designs have gained prominence. The first is called "flex-tail." The second is the "rigid center spoon." The third is the "shell" or "spoon" flex-board, which is probably the most popular flex-board in use today.

FLEX-TAIL

Of the three most common flex-boards, the flex-tail is probably the simplest to manufacture and easiest to understand. The biggest assets of the flex-tail are its ability to maintain sufficient flotation and still flex in the wave. The board is designed so only a small section of the tail area (less than 1/5 of the board) will actually flex. The flexing tail section is about 1/16 of an inch thick, and is made of cloth and resin only. No part of the flexing tail section contains any foam. The remainder of the board is exactly like a normal foam knee-board and affords great flotation, unlike spoon knee-boards.
I asked Steve Lis (winner of the 1969 Newport and Huntington Beach knee-board contests) why he preferred a flex-tail to a spoon-type knee-board. Steve responded by saying he felt a flex-tail enabled him to make quicker, tighter turns than a spoon. Steve also feels that a flex-tail is a better all-around board and doesn't limit his riding to big, fast waves.

RIGID CENTER SPOON

The rigid center spoon is one of the most controversial flex-boards in use today. It is designed to allow the rails and tail section to flex while turning, yet still keep the bottom flat for speed. Dr. Terry Hendricks (author of "Surfboard Hydrodynamics" articles) is the leading manufacturer of the rigid center spoon. Terry is constantly testing theories dealing with pressure, foam-to-flex ratios, super-flexible resin, knee-board molds, unidirectional cloth, and other precise methods of improving current knee-board designs. Hendricks is a prime example of the movement among knee-riders to find a different direction in knee-riding.

To find out how the rigid center spoon reacts in the water, I talked with Tom Pfeifer, considered by many to be the best big-wave knee-rider in California. Pfeifer contends that the rigid center piece up the middle prevents the board from overflexing in the bottom, which may create drag. With the bottom flat, the flexing pontoons and tail section will assume the shape of the wave face in the form of a variable rocker.

The rigid center spoon is by no means a simple knee-board to understand, and is still in the early stages of development. Some claim the center piece defeats the whole purpose of the flex theory. Others say it could revolutionize flex-spoons. But whatever happens, the important thing to consider is that the rigid center spoon represents another step in a new direction of knee-board development.

FLEX-SPOON

The flex-spoon is a very complicated knee-board to understand. No one really knows what design is best, as everyone seems to be testing a multitude of design theories. Of the four major manufacturers I talked with, none of them were in agreement on materials of construction, foam-to-flex ratio, flotation, manufacturing process, wave-riding potential, or even the basic function of a flex-spoon.

As we've stated previously, a flex-board is designed to allow the bottom of the board to stay flush against the wave to increase speed and maneuverability. There are several current spoon designs that allow for these qualities.

One way to build a more flexible spoon is by leaving the pontoons thin. The thinner the pontoons, the more the board will flex. Another method of increasing flexibility is to shorten the length of the pontoons, leaving a few inches of pure flex in the tail section.

Now if we took these two basic designs and applied different foam-to-flex ratios, what would happen? Increased foam width in the longer pontoons would tend to decrease flexibility. But if we increased foam width and shortened pontoon length, we would increase flexibility because of the added pure flex area in the tail. We again must realize that other design factors will play a big role in determining the overall performance of the board.

One of the most important changes in spoon design has been in the rail flow pattern. The rail design has gone from the soft, egg-type to a constant low flowing rail from nose to tail. Some said it would never work until Bob Bolen designed a pontoon that made it feasible.

Bolen shaped a tall (2 inch), narrow (3 inches at widest point), tubular pontoon. This type of pontoon increases strength, flexible body area and torsional (corner to corner) as well as longitudinal (nose to tail) flex by eliminating flex-deterring foam. In the past, spoons tended to release poorly on bottom turns if the rail was too hard. The design of the tall, narrow, tubular pontoon allows for increased speed, due to the constant low rail line, and better release for recovery maneuvers because of the softness on the top of the pontoon.

Probably the biggest advantage a flex-spoon has over knee-boards with solid foam centers or rigid center pieces is its ability to flex longitudinally as well as torsionally. Stiff-centered boards may eliminate longitudinal and torsional flex because of their extreme rigidity. Some claim it is necessary to the basic function of a flex-spoon for it to flex longitudinally and torsionally. This enables the board to plane on the face of the wave, rather than drag through the water.

MOVIN' ON

As knee-riding continues to develop, it is evident that there is no longer one person who dominates all thoughts on design theory. George Greenough is a fantastic knee-rider and profound contributor to the surfing world--to whom we should all be deeply grateful. But we must now acknowledge the hundreds of knee-riders who are trying to improve on Greenough's technical genius. The once misunderstood and stereotyped sport has blossomed into a highly individual and creative experience. Knee-riding is truly advancing in a new direction.