Bottom Contours

As with most things on a surfboard the bottom of your board can come with a lot of different variations of contours. Each gives the board a different feeling and characteristics that will provide lift, speed, and control in turns by the way that it directs water across the bottom of the board. The simplest way to break bottom contours into categories is to think of them as either convex, concave, or flat. Within each of these categories there are tons of different variations and ways to blend them together to help you find that exact feeling in a board that you are looking for.

While there are countless variations on how bottom contours can be blended together, below I will go over a few of the more common contours, and how they should effect the way your board rides. As with everything else on surfboards there is no one right answer in bottom contours and personal preference plays a lot into it. Surfboards are a constant give and take. What works ideal in some conditions won’t excel in others. The best thing that you can do is get out there and try a lot of different boards to find what works best for you.

 

Flat Bottom

Flat bottom surfboards are pretty much how they sound and do not have a noticeable contour to them. They were the original surfboard design but are not that widely used today. A flat bottom surfboard will cause the board to skim across the surface as opposed to creating lift or parting the water as other contours do. Flat bottoms do well on slower and mushier waves and will respond well to those conditions. When you put a flat bottom board in better more powerful waves they become hard to control and will have a tendency to start to slide out when a lot of pressure is put into a turn. You will also find at higher speeds it is harder to initiate turns. In most modern boards with a flat bottom the flat section will not run the full length of the board and is often blended with another concave to help relieve some of those issues.

flat concave

Single concave

A single concave is a concave that runs usually from about 12 inches from the nose all the way through the tail. The concave will get deeper as it goes back with the max depth usually just before the front fins and then progressively getting less as it goes out of the tail. This set up really starts to funnel the water along the bottom of the board, therefore building up water pressure and increasing speed and lift. Try to imagine how a catamaran boat is designed and a single concave board works similarly. When water flows beneath the board lift is created and you are really riding primarily on the rails of the board. This design works well to create a very fast surfboard with tight turning radius, and excels in larger clean surf so is a popular choice. As with all designs though it does have its drawbacks. In bumpier surf these boards seem to have trouble channeling the water through smoothly causing them to loose their forward drive. Another issue that can happen with single concaves is because the water is flowing so strongly through the center they can have a tendency to track in one direction and become hard to turn, feeling like they are stuck to the wave face. Many shapers will counteract this by blending a subtle v into the tail as is discussed later. Another thing to consider is the depth of the concave. For smaller wave boards look for a deeper concave, as this will create more of a funneling effect and give you more speed in weaker surf. For larger surf a shallower concave is more effective as the wave already has enough power to generate speed and by having less pressure build up from the shallow concave the board will not feel as if it is stuck to the wave.

single concave

 

Double concave

If you were to cut a cross section of a board with a double concave and look down it as the water would flow you will see that it looks similar to a single concave with the exception that the middle is raised up slightly. This bump will cause there to be two low points on both sides of the middle. This type of bottom is very commonly found blended together with other concaves, while there are some alternative crafts such as some mini simmons type boards that will have a double concave all the way through the board. This design is used on small wave boards as it will create a lot of lift for a board in slower surf and a very low rocker can be used to add speed in weak conditions. Because the water is split a board with a double concave will give a much looser ride and flowing maneuvers.

double concave

 

Single to double

This is probably the most common contour that you will find on modern day performance boards. It is a blend of the two previous concaves on the bottom. The beginning of the board is usually a single concave running to just about where the back fins start. Here it will subtly blend into a double concave through the fin section. The advantages of a single to double concave is that as the water flows beneath the board and builds up pressure in the single part while the double concave separates that flow and directs it off towards the edge of the board. This is one way of stopping the tracking feeling of a single concave and also loosens the board up so that it is easier to roll from rail to rail. This is also one of the more user-friendly concave blends and works well in a variety of conditions.

 

Channel bottoms

This type of bottom uses cut out grooves, usually between 2 and 8, to propel and guide water flow creating more speed. Channels can be very tricky as there are a lot of different ways to do them ranging from the angle that they are cut in at to the length of the board that they cover. Boards with channels excel in clean surf and do not perform very well when there is texture on the water surface. A board with proper channels put in will likely be one of the fastest board you ever ride when conditions are good for it. Channel bottom boards are not that common because as said before they are not that effective unless conditions are very good for it. They are also very time consuming to produce both for the shaper and for the glasser so there is usually a pretty high price tag attached to a board with channel bottoms.

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V Bottom/displacement hull

On a V bottom or displacement hull type of board the lowest point of the board in the water will be the stringer. These types of bottoms would be considered a convex bottom contour. The difference between a V and the displacement hull would be how much roll there is in the blending from the stringer to the rail. On a V bottom it is more of a sharp angle towards the rail as a displacement hull is more of a rolled smooth belly out towards the rail. A displacement hull is found on many longboards and is usually found up towards the front or in the middle of the board where as V is usually used towards the tail end. The advantages of having this type of bottom is that it will roll rail to rail much easier then other types of concaves making the board easy to turn from one side to the other. In many modern day shortboards you will find V added into the tail to really split the water flow and make turning them much more user friendly. These types of bottoms are traditionally not used on smaller wave boards because the parting of the water to create lift will actually cause them to be slower. That being said you can find them on many big wave boards as speed is not as much as a factor as trying to control a larger board. This type of bottom will also excel in choppy or unclean surf as it will part the water and break through any bump that may be on the surface.

v bottomdisplacement hull

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