As I’m the only shaper posting on here who has actually designed blanks for the big PU companies, I guess I should put in my two cents to help out.
To be successful and sell well, blanks need to accept rocker changes well and have a little versatility built into them. Minus rocker changes can lead to big distortions on deck; so most blanks are designed with about the flattest rocker the shaper would want. That way most of the custom rockers applied will be additions, which won’t make lumps in the deck. Making the blank a little thicker (proportionally) at the tips gives some versatility, and makes indexing on machines easier as well.
Clark worked off of a deck rocker standard, I would imagine US Blanks still does. What this means is that if you submit a bottom rocker, they are going to transpose it to a deck template to glue it up. See the comment above about tip thickness to understand one of the reasons for this; you’re almost always going to be foiling tips to finish, it’s much better to take this off of bottom. Many shapers never understood all the reasons for the deck rocker standard so it would be hard to explain it all here:)
There are some good horror stories about guys submitting “finish” bottom rockers and getting back really ugly blanks because of distortions they didn’t account for.
The easiest way to submit a custom rocker is on paper, full size with a reference line. The reference line (a straight line on the paper near your rocker curve) allows them to make sure they get it right.
