I was wondering if anyone can put my mind to rest. i have been running templates through my head for next boards and one thing i am struggling with is that a template on cad is 2d and then when i transfer that to mdf still 2d. then if i lay that template on the bottom of the blank then the rocker is introduced into the line that i mark on the blank.
do other peoples templates take this into account, ie, have they been produced from a board therefore allow for the rocker? or is the change in curve/length negligible?
There is a difference in the length of the bottom template if you take into account the curvature of the rocker. I have been playing around with creating my own templates, and attached an example of a design for a 6’ 8" board (see attachment). You can see the stringer template on the right. On the left is a template of the bottom skin of an unshaped blank. Notice that the length of the bottom skin is slightly longer than the length of the stringer.
I’m dealing with same problem right now. On the last project with mucho bottom rocker I laid the template midway on the board then moved it foward to get the nose, then back from center to get the tail, I figured the big average would solve the issue. That method left a straight section on rail in the center of board, not so great, the whole rest of the shaping job had that imperfection in it, trying to work it out by unpracticed, amature eye wasn’t so great either. I’m making top view templates for the next project now and am still wondering how to get the paper drafted flat top view onto the mucho rockered blank?? The boatbuilders must have a simple way to do it, they wrangle with these kind of problems always.
Don’t template on the bottom…draw your outline on the deck. This has mixed reviews, but as Jim Phillips says on his vid…shortest distance between two points is a straight line. And drawing your outline on the deck gets the bottom rocker out of the equation. That way your 6’0 template yeilds a 6’0 board.