I am kind of winging it, but I kind of think I have it. I draw a horizontal line and a vertical line with a 90 degree angle.
Then I set up a compass, one of those things the draw circles, or in Spanish it's called Compas, and I set the distance of the circle radius to the height of the crown. Then I put the sharp part of the compass right in the corner of the lines above, and make a circle. The distance from the corner to the place the circle intersects the lines should be the same height of the crown I want. So i have something like this:
I usually don't draw the full circle, but sense I'm using paint it's hard to do just the top part of the circle.
Then I measure from the top part where the circle hits the line to the right part where the circle hits the line. I divide that number by 6, and then I know how far to mark each line ??? Here's a picture:
Pretend that is a circle. Paint sucks.
Then I draw lines from the center of the right angle through the points that I marked and all the way out to the circle:
Now using a straight edge, I measure the intersections for the lines that I made with the circle, from the base line. But I don't measure them starting at the center of the right angle, I measure them straight up from the base line. If you come out with the all same numbers, you are measuring from the original intersection of the lines. The way you measure it is in RED. The heights of the red lines are the numbers you are looking for:
So if the crown I want is 5 inches, I will have 7 numbers. The first one is 5 which is the center, and then I will have 5 more measurements which are the red lines and then the last number is 0 which is the edge.
So then I measure the width of the boat. I divide that by 12, and then make a chart. The top number is 0, shortest red line, next red line etc...5, longest red line, next longest red line...0. The bottom line starts with 0 and then you add 1/12 of the width for each number on top. Here is one of the charts, I think this makes sense? Its all the numbers:
I convert everything to centimeters because then I don't have to deal with fractions. So 7.7 is my overall height, and that's like 3 inches I think ??? So that bottom chart is my 3 inch chart.
And then you draw a line using string across the top of the boat, and mark the 0 line on the plywood which is the outside height, and then you measure across 1/12th of the width of the boat, and start with the shortest red line and mark that height. Then after you have twelve heights (0, 5 red line heights, total crown, 5 red line heights in descending order, and 0) at 12 different equal intervals (by dividing width of boat by 12) you mark it and connect the dots
I am terrible at explaining this...
Any Questions ?