Bottom roll and rail profile

General Discussion
1

I’ve been drawing out bottom roll and rail profiles on graph paper trying to get an idea of what I want with my next board, and I’ve come realize that your rail profile will always determine your depth of the roll. This seems obvious to me now, but a 3" board with bottom roll, and 50/50 rails will always have 1 1/2 roll. This all goes off the presumption that everyone is measuring roll depth at the apex of the belly to the apex of the rail.

How the roll progresses to the final depth is what I think counts. Knowing what rail profile you want and finding the curve that gets you to that point is what I think people are talking about when they say a board has so and so roll. The ol’ Swaylock’s saying rings true, “Don’t look at numbers look at curves”. Slight, medium, or deep belly is more about the curve between the points, and thus far measuring these as radius curves seems more reliable to me at this point.

I’ve got a board 3 1/4 thick with 1 1/2 belly (measured from belly apex to rail apex). Rail profile looked to be 50/50, but based off this they are 60/40ish.
How are other’s measuring bottom belly/convex?

Start talking about them bellies gentlemen!

2

Another point you didn’t mention is width of the board; The wider the board (with the same thickness), the “softer” the roll curve will be.

3

A dash and a smidgeon!

4

The roll doesn’t have to be even all the way to the rails. A 50/50 rail or a pinched rail can be started about 2 or 3 inches from the edge. I’ve found the best rolled bottom is one that is very subtle, hardly noticeable. Add slightly pinched rails and you can have a fast and fun board. I don’t ride nose riders, so if your intention is to make a nose rider, more roll will slow the board down and help keep it in the pocket when you’re on the tip.

5

The rail apex thing can get confusing, much like ‘raw’ rocker measurements taken at the ends of the board. There are a lot of ways to connect the dots… extreme underside rail or bottom roll out near the edges or more of a rounded off vee closer to the stringer… or any combination of the above. Here is a diagram I posted several years back in an attempt to illustrate how rocker ‘dimensions’ can be interpreted. Or misinterpreted.

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