The best information I have found on mast rake from Pearson is from the paper written by Bill Shaw:
Tuning the Rig. First he recommends using the figure on the Sail Plan drawing, which I cannot discern from my copy. But Bill does go on to say that for a cruising boat 6"-12" rake is a good rule of thumb. And he is the man for Pearson cruising boats.
Typically you want enough rake to get 3-4 degrees of weather helm in close-hauled sailing under moderate conditions and flat water. But
it depends on the luff curve of your current mainsail (kind of a catch-22). The rule of thumb is to put in 1-3 inches of pre-bend and establish base settings for the rig tension. Then you will want to fine-tune your rig to sailing conditions with rig tension and mast rake. This is when you can establish the slight weather-helm you are looking for.
My experience with my P323 (not much sailing time, I have been working on it as a project boat since I got it), is that the boat does not have any weather helm as it is currently set up, which indicates that I should add more rake. I am an absent owner so I can't measure the mast rake right now. Keep us posted on the progress of your new sail design. (who is the sailmaker?)
