Bottom Curves Part 1
In the latest instalment of Boarding School, Cory Russell flips your board upside down to check the engine room. Bottom curves effect how the board interacts with the water surface making them one of the most important aspects of design. So, what are they and how do they work?
The bottom contours of a surfboard are designed to control the way a surfboard influences the water flowing underneath it. It’s a simple concept made complicated because surfboards constantly change speed and direction in a multitude of wave conditions. Also, while the water will generally travel from nose to tail it can also move at varying degrees of diagonal as a board turns.
Back in the day, a lot of surfboard shapers had experience building boats or at least a basic understanding of boat design. These days, however, surfboards stand alone for design principles specific to how we use them and the materials they are constructed with.
Over the years various designs have been experimented with but I've tried to identify the most significant and/or those commonly found on surfboards. The bottom contours of a surfboard are a complicated design element so I've had to break this topic up into two instalments. This week we'll decipher flat bottoms and vee bottoms.
The second instalment, coming next week, will cover concaves and channels.
Flat bottom surfboards are, as the name suggests, flat from rail to rail. Viewed side on there’s no difference between the centre rocker and rail rocker. Flat bottoms are completely neutral with no increase or decrease in lift and they rely on only the one rocker curve. This means there’s equal water pressure across the bottom of the board and of all the various bottom contours flat bottoms make rail to rail transitions the most difficult.
Flat bottom boards can bog at low speed and they lack control in choppy conditions or at high speed as they skim across the water surface.
A vee bottom is a convex shape which means the centre rocker is higher than the rail rocker. When the bottom of the board is facing up it looks similar to a single peak roof top. Vee bottoms allow the board to sit deeper in the water. Any weight that is applied to the top of the surfboard will first push the centre of the board deeper into the water and the resulting water pressure will make its way to the rail along the incline. A vee bottom won't create lift as the water pressure, or up thrust, is not captured by the surfboard.
Depending upon who you ask, and what mood they're in, the first vee bottom surfboard was shaped by either Bob McTavish or Midget Farelly. McTavish's board featured a deep panel vee along the rear section that, according to the Encyclopedia of Surfing, "more or less forced the board to tip over into a turning position".
McTavish was a key player in the Shortboard Revolution and vee bottoms were integral to the changes that followed. Surfers wanted to turn harder so vee bottoms became the bottom curve of choice because they transition from rail to rail easily.
Vee bottoms remained a popular choice for shapers for many years, particularly pre-1990 when boards were wider, thicker and flatter. Vee bottoms come in a variety of styles including panel, rolled, reverse, spiral, and inverse.
Panel vee is the name given to the most simplistic and common form of vee. The incline on the bottom of the board is a flat surface from the centre of the board to the rail. This type of vee is usually found in the back third of a surfboard and provides some directional stability. Also, the increased rail rocker provides more manoeuvrability.
Panel vee is a common choice for big wave boards as the vee allows the board to sit lower in the water at high speeds and it adds control.
Midget Farrelly in 1967 with a first generation vee bottom (Photo Dick Graham)
Rolled vee is when the incline on the bottom of the board is curved from the centre of the board to the rail. The roll softens the peak of the vee and provides more forgiveness. This type of vee is common in classic malibu designs and is often combined with a soft bottom rail which adds drag as well as lateral drift.
Directional change using a rolled vee bottom is slower but somewhat smoother than panel vee.
Rob Walters with a rolled vee Wilderness almost certainly shaped by Chris Brock (Photo Jeremy Walters)
The name spiral vee is a little misleading as it is not just vee but a mix of concave as well. A spiral vee bottom begins as a subtle vee under the front foot which increases in depth as it moves toward the tail. A double concave is placed within the vee and also increases in depth as it moves toward the tail.
The double concave provides the board with lift as the increased curve in the rail rocker provides release. Like many subtle design breakthroughs it's unclear who first came up with spiral vee, though Dick Brewer and Terry Fitzgerald both used it with dramatic results on their pintail pocket rockets from the early-70s. Either could lay claim to being the inventor.
Back in 1991 Maurice Cole received a container of pre-shapes that had been incorrectly packed and had ¾” more rocker in the nose and tail than expected. Trying to rectify the problem, Maurice inadvertently placed vee under the front foot and flat between the fins - the opposite of what was then considered normal.
The success of Reverse Vee or EEV (VEE spelt backwards) is due to the increased centre rocker balanced with a straighter rail rocker. This combination creates a highly manoeuvrable and responsive board down the line whilst the straighter rail rocker provides speed and drive through turns. The vee under the front foot allows the surfer to go from rail to rail with ease and the flat bottom between the fins provided a stable surface to push against as the water released off the increased tail rocker of the board.
Maurice Cole and Tom Curren with an original reverse vee from 1991
Vee bottoms on surfboards were a great addition to early surfboard designs due to the considerable width of surfboards then used. A vee bottom can make a board feel slightly narrower due to its effortless transition from rail to rail and would allow a surfer to fly down the line.
As surfers demanded more of their equipment the vee bottom became a limiting factor. Vee bottoms lose speed through and they also tend to drift in turns rather than bite like a concave does.
By the end of the 80’s surfboard designers would begin to push the limits of design as surfers demanded to turn sharper and generate more speed on smaller, thinner equipment. There have been many shapers explore various forms of concave in surfboards going back to Bob Simmons in the late 40’s, however they did not become standard until the early nineties.
In the next instalment we will discuss concaves and channels.
Cory Surfboards / Stretch Boards Australia