Boarding School: Volume
By Cory Russell
In the last few years I've watched the popularity and importance of volume measurements for a surfboard reach extreme heights. While I agree that volume has a place in surfboard design its importance has been oversimplified and misused by many surf shops.
In its simplest form the volume measurement of a surfboard merely explains how much of the board is underwater when you lay on it. There's no reference to where the volume is situated, such as the nose, middle, tail or rail. Volume measurement can be used as a guideline but the other elements of the board are more important.
I've even had people try to order boards by their volume. To these people I explain that I can achieve that volume in many different ways - some will work for them and some won’t.
The take home message is simple: Don't get obsessed with a volume measurement!
In years gone by volume measurement didn't exist for surfboards and a surfer would rely on the advice of a shaper. The introduction of computer aided design allowed the calculation of volume and if used correctly it can be a valuable new dimension.
The truth is, many, if not most, shapers couldn't calculate a surfer’s ideal volume by relying on previous board volumes. The ideal volume for a surfer can be a difficult thing to specifically calculate and on top of usual factors such as weight, age, etc., you must take into consideration the climate where they surf and the types of waves ridden. In its most simplistic form each 2.75kgs of bodyweight requires 1 litre of volume.
In scientific terms, buoyancy - also known as up thrust - is an upward force exerted by a fluid that opposes the weight of an immersed object. If the object’s density is greater than that of the fluid in which it is submerged, it will tend to sink.
There are two main types of foam currently used to build surfboards: Polyurethane (PU) and Expanded Polystyrene (EPS). Within these two types of foam there are various densities available but I will concentrate on PU, which is the industry standard.
The weight of standard PU foam is approximately 36.86kgs per cubic metre. The weight of standard EPS foam is approximately 33.65kgs per cubic metre. According to Archimedes principle the weight of an object directly affects its buoyancy even if the volume is the same. This means that the 9.5% difference in weight between PU and EPS does affect the buoyancy of a surfboard.
Volume calculators are a dime a dozen. I'm sure many of you have entered your details into various calculators only to arrive at very different results. Often the reason for this is the ambiguous terms they use: Beginner; Beginner/Intermediate; Intermediate; Intermediate/Advanced; Advanced
Can anyone decipher the difference between these levels of surfing? For instance, when does a surfer go from a beginner/intermediate to intermediate? I suspect everyone’s description would be different and unfortunately it will affect the result a person will get.
Another flaw of many volume calculators is the five year increments for age or five kilogram increments for weight. What happens if you are in the middle and forced to choose? One volume calculator tried to take it to the next level and added a ‘Guild Factor’…what the hell is a guild factor and how do I accurately determine mine? Further investigation found more vague descriptions ensued followed by large paragraphs of jibber jabber.
The surfer’s weight.
The average number of times they surf per week.
And how many years have they been surfing.
I calculate a specific volume amount and establish a range which is ‘+’ and ‘-‘ 1.5 litres. After this is done I then discuss the climate where they live and waves they surf to get a more accurate result. I don’t claim to have the perfect volume calculator but at least my customers can answer the questions easily and accurately.
For those surfers that have identified their ideal volume you need to understand that this amount changes depending on the type of board you have. For example, the volume you would ride in a shortboard is different to the volume you would ride in a step up. I have developed the following guide for those obsessed with volume:
Groveller - add 9% volume
Step down - add 3% volume
Step up - add 5% volume
Semi gun - add 15% volume
Keep this in mind when you are ordering a new board and it will allow for the necessary increases in a board’s dimensions.
Cory Surfboards / Stretch Boards Australia