A surfboard rocker analysis

A question on rocker from GDaddy on surfermag.com:



"I don't understand the reasoning for using so much rocker on a board that gets used in small waves. I know I prefer less rocker on the boards I use in small waves because I feel like they're faster and smoother. On all the heavily rockered boards I've ever surfed, they seemed slower to me than the flatter rockers that I normally prefer for those conditions.

Input?"





Hello Gdaddy.

You will probably be surprised to learn how the rates of curvature ( as measured by the radius of the curve at any point or the average radius over a given distance ) used on Roy's boards compare with other boards.



All is not what it seems regarding the rocker on Roy's boards.



There are also many different rockers used on his boards.



For example Roy has a favourite 9'1" design which has only an inch and a half of rocker overall.



We could start the discussion with one of the boards which might seem extreme in their rocker to you, for example the FP12, FP13 or 17 foot olo designs.



For the discussion to be productive we need to agree that it is the rate of curvature rather than the overall rocker measurement at nose or tail which is most relevant when comparing boards of different length.



To that end I suggest that you visualise a simple circle.If we take segments of this circle of different lengths we get all sorts of different overall rocker numbers, even though the curve is the same in all cases. Thus it can be seen that in a simple case where a rocker curve is extrapolated to a longer surfboard, the overall rocker measurement ( and the rocker visually when seen from nose or tail ) is misleading as a guide to the actual rate of curvature of the rocker.



It might also be helpful to quote the nose and tail rocker measurements and length for one of the flatter boards which you have. Of course this will ignore subtelties of rocker but it if I am correct it is overall rocker rather than the subtleties which you are talking about, and in any case we need a place to start for comparison.