I have built a 17 ft 6 inches Whitehall broadly to Gardner's lines, but strip built overlaid with epoxy, and the deadrise at 10 degrees rather than his 15, since my boat will be around 75 lbs lighter than the traditional Boston one (i.e. less than 200 lbs all up). I propose to row if I have to go dead up wind, and sail across and down (effective beating not needed). I have given the boat a 2" keel strip, which over an effective 16 ft gives say 2.5 sq ft, about the same as a small dagger board. The rudder adds another square foot. I will add a lee board later if it turns out to be needed. My sail is a high peaked loose foot lug, re-cut from an old 80 sq ft dinghy sail - it comes to about 60 sq ft. The mast is 13 ft overall, and I would like it to be free standing held in a gate 20 inches from the base.
Here's my question. Other than by guess and by God, or cut and try to be more accurate, how does a person settle on the mast dimensions? What I am proposing to do is to epoxy two spruce 2x4x13 ft together, leave them "as is" the first three ft, then taper evenly up to the head, where it will be 1.5" by 3". The whole thing above the lower 3' will be nicely (I hope) rounded, becoming oval at the head.
Given that the total cost of materials is $50 (Canadian), there does not seem to be too much to gain by intensive theoretical calculations, but does anyone have some good practical experience to suggest if anything in this approach is not likely to work? Additionally, is this mast overbuilt for the job? I would very much like to get it to a reasonable minimum weight.
Thanks for any interest!