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How do I calculate Side Cut Radius?


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This should be an easy one for the long-timers on this forum. I tried a search using various strings, and didn't find anything. If you could provide the formula and dimensions necessary, I'd appreciate it. I'm trying to calculate the sidecut of my current board so I know what to base a future board purchase on.

thanks in advance.

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R = l<SUP>2</SUP>/8d + d/2

R = sidecut radius

l = running length

d = sidecut depth

you can omit the d/2 term if you want because it is pretty much insignificant.

(Excuse the math geek....)

Jack -

is 'l' a straight-line measurement, or cord-length measurement?

is 'd' count one side of the board or both? (example - if waist width is 18 and tip/tail width are 24, is the sidecut depth 3 or 6?)

and finally - how does one measure sidecut depth on a tapered board?

Example: nose width = 24, wasit = 18, tail = 23 - what's the sidecut depth?

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If you want to see the math that makes my page work:


Measure the sidecut depth on one side only (3 not 6 in your example).

For a tapered board, I just average the tip and tail widths. I'm actually not 100% sure that's correct, but even if it's wrong, I bet it's off by a negligible amount.

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Jack, thanks for reminding me of that formula - I used it when I worked for an engineering company, long ago, and I couldn't remember it any more...

However, there's another way, for CAD users:

1) Draw a line, same length as the running length of your board.

2) Draw a perpendicular line, long as SC depth, from the centre of the first line.

3) Use the 3 end points as the definition points for an arc (or circle)

4) Use the auto-dimensioning to read the radius.


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I usually just make up a number that sounds reasonable.

It's not like there is much variation among boards of a given length anyway.

Gotta agree with Daneille!

Coiler FC 178 = 10.5 m sidecut

Burton FP 178 = 14.2 m sidecut

Shred's Donek Zie scalpal 177 = 15 m sidecut

16m <= Madd 180 sidecut <= 22m depending on who you ask

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