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Surfboard Bottom Contours

Concave’s, Flats and Vee’s and how they affect your surfboard

mark gnech with one of his vampirate surfboards creations
Mark Gnech working on a hand-shaped Vampirate Surfboards bottom.

Much of a surfboard's performance is related to it's bottom contours and how they blend together. Bottom contours (when used correctly) are intended to produce controlled drag and lift. There are some basic principles and, like all other areas of surfboard design, tried and true methods that have held the test of time.

In the interest in keeping things simple for now, we can talk about three main categories that surfboard bottoms can fall into; flat, concave and convex.

Most boards, if not all, have a blend of at least two of these categories and rarely utilize just one. It is the blending of these contours that help dictate how your board will perform. Once you establish what kind of bottom you are looking for, you can use the Board Engine to then compare similar surfboards to find the one that suits you best.

surfboard bottom contours
Different bottom contours. Any part of the bottom that lifts above the rail line is a concave. Any part that dips below the rail line is a vee or belly convex and flats stay around the same level as the rails.


Flats are simply flat sections of the board. Simple right?

As a general rule, flat is fast, but flats don’t contribute much of anything to performance. They don’t provide lift, they don’t help direct water flow, or leverage when maneuvering the board. They are usually blended together with either concave or convex bottoms, and strategically placed (usually somewhere around or leading into the middle of your board) to help give you a fast section of your board.
They can help get you through mushy or soft sections, or just to haul ass down the line.

dms carbon wraps ready to go
Some Dan McDonald DMS Surfboards with carbon wrap technology ready to go out.


Concave's are essentially any part of the bottom that lift above the rail line of your board (towards the deck).

Concave's help produce lift and laminar flow, and also help to increase the overall surface area of the bottom compared to a flat bottom. The laminar flow is the direction in which the water is funneled along the bottom of your board.

water flow by bottom contour
The direct front to back flow of water in a Hammo Surfboards single concave model the Speed R1 increases your speed. Next to the controlled release of water flow out the sides you get in a Peri Peri with single to double concave.

There are many variations of concave’s, like single concave, double, concave under the nose of a Longboard, etc., which all produced some sort of lift under the surfers feet.

It's the balance of the lift and the drag that a concave produces that impacts on your boards performance.

The concave, like those found in a shortboard, also help keep a tight down rail that will bite into the waves face a little better, adding to your control in higher performance surf.

Asher Pacey on his DHD sweet spot 2.0
Asher Pacey on his DHD Sweet Spot, right where it wants to be.

Convex Contours

Convex contours are really any part of the board that sits lower in the water than your rail line.

These are commonly found on Longboard, hybrids and displacement hulls. They help with the transition from rail to rail as you can roll from one to the other with little effort, they also help provide lateral stability and can be fairly forgiving depending on the board and how they are used.

Depending on the shape of the convex, you can have a smooth rolling "belly" bottom, or a harder angled Vee bottom which you may find on the very back end of shortboards, hybrids and Longboard, helping with stability in the tail and transitioning from rail to rail.

Convex bottom contours can be used along any portion of the surfboards (nose, middle, tail) and when blended correctly with flats and concave, can be a really useful tool.

Blending your bottom contours:

The most important part about the performance of your board is not the use of any one of these bottom contours, but how they are used an blended together.

Lets look at three examples of boards and what bottom contours you may find. (note: there are endless combinations and this is not set in stone, just examples).

some bottom contours
Some single concave transitions into doubles and vees.

Performance Shortboards

In many high performance shortboards, you may find a slight flat section just behind the nose, blending into a single concave through the middle of the board, which then blends into a double concave just before the fins, combined with a little Vee out the tail.

The flat front section is going to help when paddling into the wave as it gives you a nice even surface to help plane on when lying prone on your board and trying to paddle as fast as you can.

The single concave is going to come into play when you get to your feet and start driving down the line. This helps set your rail in the face of the wave as well as provides lift and speed, keeping your board on top of the water and channeling the water through the mid section of your board.

The double concave starting in front of the fins, helps redirect the flow of water under your tail and around your fins, also helping to create lift under your back foot. The Vee right in the end of your tail helps with control and from transitioning from rail to rail in the back third of the board.

hammo surfboards inspection
Checking out how the quality of rails and bottom contours on a fresh set of Hammo Surfboards.


In a hybrid shape, you may find that you have a little “belly” in the nose, blending into a single concave running through the mid section then going flat to Vee out the tail.

The convex "belly" in the nose is going to help displace water while paddling into a wave or when re-entering when coming off a turn. This displacement helps keep the nose from pearling (going under the water) and is especially useful on flatter rocker boards.

Again the single concave will produce the lift and speed needed when up and flying down the line. We then blend into the flat to Vee out the tail, which helps keep your speed up and makes it easier to quickly transfer from rail to rail which is essential when surfing smaller waves.

tom carroll on the eye symmetry cali quad
Tom Carroll on a 5'4" Eye Symmetry Cali Quad with Magic Fibre construction showing how the single to double concave with vee off the tail works for him.


And our last example would be a traditional nose riding log. Here you may find some concave in the nose area of the board, blending to rolled “belly” through the mid section, and then Vee out the tail.

The concave in the nose is purely for creating lift when you are perched up at the nose all ten piggy over the edge, as well as helping with control as you can use your rail a little easier when surfing the from this part of the board.

The rolled “belly” through the middle of the board gives you some stability as well as helps to provide smooth transitions from rail to rail. The Vee coming out the tail helps to pivot from rail to rail when trying to turn a little harder and re-direct the board.


As with every aspect of surfboard shaping, there is no right or wrong way when approaching bottoms, and endless possibilities and combinations that can be played with.

Some become common place while others are suited to more specific designs.

How they play into your board's rail, tail and nose is also important to understand. There are also many other types of bottom contours such as channels, panels, chines, etc. These are all functional in their own way by helping to direct water flow under the board, around the fins and give you some controlled drag depending on how the shaper intends the board to perform.

By understanding more about surfboard design, you can make a more informed decision about your next board.

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24/03/2020 4:42 pm

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