Concave is the term given to the curve shaped into the bottom of the board, the depth of the concave varies on the board model, waves to be ridden and the shaper:

for a sucky wave like pipeline - a  deep single concave going to a vee out of the tail for bottom turns

for a more rolling wave like sunset - a shallow concave is used with a vee going out of the tail

 

Single Concave

 This  reduces the rocker curve of the board giving it directional speed whilst maintaining manouvrebility because the concave pushes the water down the middle of the board along the concave which acts as a very subtle channel.  The concave is used on most shortboards and some fish.  If the concave is too deep the board gets a bit twitchy although some surfers request a deep concave .

 

Double Concave

Two concaves are shaped into the bottom of the board between the middle of the fins this loosens up the board making it easier to surf the board from rail to rail, jetting the water between the fins.

 

                                                  Triple Concave

The single concave is shaped into the bottom of the board through to a double concave between the fins.

 

The  choice of concave depends upon surfer ability , intermediate surfers normally like a double concave because it makes the board easier to ride, a triple concave is more often requested by experienced surfers.  Team riders like single concave out through the tail with more under the back foot (between the fins)  giving it more control in the curl of the wave and making it more responsive.

But the main thing to remember is that many ingredients need to be right before you put the concave in.  Rocker and rail line have a lot to do with how much concave is put into a board but this will be talked about later.

Surfboard Blanks

The raw material for most of the boards I shape is made from the polyeurothane foam (PU).

The first blanks were made at the end of the 1950’s by a couple of famous Californian surfboard shapers but the man credited with perfecting the common blank as we know it today was Gordon “Grubby” Clark.

This changed surfboards overnight from the bolsa wood cores that they were before to lighter more high performance boards also this was the start of true production surfboards.  Today Clark Foam is no more but there are many different companies in the market making  large quantities of blanks in Australia, South Africa, Europe and California.  There are many different qualities of blanks but the best quality seem to come from places that have a stable climate - the Gold Coast ,California and South Africa.  This is because the constant temperature of  around 80 degrees gives a consistency for the blowing process minimising the air bubbles ( I am not sure exactly why this occurs as I am not a chemist ) but blanks blown in colder climates never seem to keep the quality consistent. Also a lot of the better blank companies still pour their mix, to blow their blanks by hand and this is a very fine art which gives better results than blowing the blanks with a machine.

 

Blanks come in many variations from hand shaping blank moulds to machine plug moulds most companies have at least 10 - 20 moulds on offer at all times with others that can be ordered.  Many of the top shapers have at one time designed plugs for the larger companies giving the product closer tolerance ie the starting rocker curve and thickness and rail line.  The original blanks were just lumps of foam.  Blanks can also be ordered with a shaper’s specific rocker curves this is achieved when the glueing up process of the stringer is done.  I only use US Blanks in the UK this company seems to have taken over from where Clark left off, they probably have the most diverse catalogue on the market today.  The foam is hard but very easy to shape and the stringer glue ups are excellent.  In Spain as there is no outlet for US Blanks I use Extra Foam which is made by Rod Mcdonald, in South Africa the foam is different to the US Blanks ie the chemical mix used,  it is very hard still and is easy to shape but has a different texture to the US Blanks also the wood used for the stringers is different to the US Blanks.

For Epoxy Blanks (EPS) see  - E - Epoxy  coming soon

Fin Angle

If you imagine a line drawn perpendicularly to the bottom of the board the central fin is always set at 90 degrees to the board but the two side  fins are tilted off this line by a certain amount, outwards.  On my boards I use four different fin angle settings depending on the board model.

#1. Three Degrees

Used for Twin fins and Vee Bottoms.

A twin fin surfs  loosley as it doesn’t have the third fin so the fins need to be set fairly straight to give the board drive.  Similarly with a vee bottomed board will give the fins more splay so you don’t want much angle on the fins otherwise you wouldn’t be able to control the board.

#2 Five degrees

For all boards shaped from 1995 - 2000- now used on custom boards when it is a particular surfer’s preference

I used to use five degrees for all my boards as it was a good general angle for boards with subtle contours it was also the industry standard. However with the greater control preshaping machines allow the shaper over the combination  of rocker, concaves etc, designs have become more specific and the five degree setting  is not so common. Now most shapers change their fin angles to suit the bottom contours of their designs.

#3 Six Degrees

Most Models

Six degrees is now my preferred default fin setting, I’ve moved it on one degree as my designs have more rocker curve and concave through the tail where the  fins go.  This extra concave through the tail acts to straighten the fins up therefore I have added an degree to splay the fins out more because if the fins were straighter the boards would become stiffer and less manouevrable.

#4 Eight Degrees

I use eight degrees for team boards with deep concaves from the team feedback, the eight degree setting compliments high performance boards perfectly balancing speed and directional  manouvrebility.

 

Four fins

The best place for more information on four fins is the master of the Quattro system Bruce Mckee everything I know about four fins I learnt from him. www.mckeesurf.com

N.B. A lot depends on where the fins are positioned on the boards aswell as the angle - most shapers fin positions are a closely guarded secret and are different depending on the size and model.