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Rusty's New Take on Volume

Posted by Rusty on

That beer mug illustrates how negligible of a volume amount can completely consume a rider's perspective.


Nearly 20 years ago when I was first introduced to CAD software for surfboards, I was in a new wonderworld of design control. There is a lot of back and forth these days…handshape vs. computer. The fact is, as a shaper, once the demand for your boards reaches around a thousand boards a year, you need to consider options or your customers will be faced with a long wait. The options are “ghost shaper” or computer, or a combination of both. One of the features of the software is that it calculates volume. Almost 20 years ago, Luciano Leao, the developer of SurfCad, told me that I must pay attention to the volume. It took me a little while but I soon understood what he meant. Move forward into the last 4 or 5 years, most customers have become obsessed with volume. Virtually all programs calculate in liters, fractions of liters, or in some cases, beers. Most surfboard websites have charts or apps that help your to calculate what your volume should be. The good ones take into consideration, not only your weight, but your ability level, age, and the type of surf you want your board designed for. At the end of the day, these charts/apps really only help you to understand what kind of volume you might want on your shortboard. You have to make a decision on thickness or volume. You cannot have both. Sometimes recommended dimension tables are spot on. Other times they are not. Designs evolve over time. Not dramatically, but they change.

"If you are getting a custom, trust your shaper’s judgment."


The equation for performance shortboards is fairly simple.

Take your weight in pounds example; 160

Convert to kilos; divide by 2.2 equals 72.73

Multiply by .35

Equals 25.45 liters

The multiple comes from thousands of shortboards for average to advanced surfers.

As the ability level decreases, the multiple increases.

With age, the multiple increases.


5’11 19.5 2.38 30 L

make it a half inch longer (yes I get asked to do that)

5’11.5 19.5 2.38 30.2

make it an inch longer

6’0 19.5 2.38 30.4

make it .5 wider

5’11 20.0 2.38 30.8

make it .125 thicker 1/8”

5’11 19.5 2.5 31.5

thickness affects volume the most


7’0 21.5 2.85 47.2

make it an inch longer

7’1 21.5 2.85 47.7

make it .5 wider

7’0 22 2.85 48.3

make it .125 1/8” thicker

7’0 21.5 2.98 49.3

My point? The thing that affects the volume the most is thickness.

The charts and tables are guidelines, not gospel. The shaper has to find a balance between the two. Unless you are a pro you shouldn’t let a variance of less than a liter bother you. You won’t feel it. You need to choose between volume and thickness; which number do you want your shaper to focus on. Once again, TRUST YOUR SHAPER. There are other things to also consider such as width, rocker, bottom contours, and thickness flow, fin position, fin templates, fin construction. And weight.

The weight of your board: Is it 6 lbs? or 6.6 lbs? That’s 10%. That’s significant.

7lbs that’s 16%.

Not to mention the type of cloth and resin. That affects the flex and springback.

EPS? Roughly 10% I generally program EPS boards thinner to compensate.

.5 liters on 27…that’s 1.8 % on 160 lbs 2.88 lbs

1 liter on 27 = 3.7 % on 160 that’s 5.9lbs

Does the computer program calculate the volume on the cut blank? Or the finished blank? It's the cut blank. When the blank gets finished it looses .3? .4? .5 liters?

"Trust your shaper's judgement." 

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