So let's begin

Where to begin?

 In the last post I talked about deciding on a design ethic and the importance of doodling and I showed a picture of one of my early doodles. Before beginning a doodle or cartoon first decide what will you be doing with this boat you're drawing. In the case of the cartoon I showed in the last post I was very much into salmon fishing and so I was looking for a fishing boat, an ocean capable fishing boat for the Pacific Northwest above the 49th parallel. Where it rains, a lot.  So the design had to be a certain size, at least 12 feet if not longer, it had to have cover and a place to get out of the wet but also an open cockpit. It had to be ocean capable. Most importantly, for my design ethic, it had to be cheap and easy to build.

The easiest boat to build and also the cheapest is a single hard chine hull. The cheapest to operate, if not the fastest boat in the world is an inboard of low horsepower.

So there we have it  but what size. Jim Michalak, as I understand it, likes to start with a simple calculation based upon expected gross weight and the prismatic coefficient (pc). He likes a pc of about .66, that is an underwater shape of 66% of a prism of the same waterline length and below waterline beam area. So you want a boat that can carry at least three adults, 700 lbs, gear, 200 lbs, beer 12 lbs, engine 250 lbs, various odd and sundry things like propellers fuel and water tankage and pretty soon you're up to a ton total. So 2000 lbs divided by 62.5, the weight of a cubic foot of fresh water, gives a displacement volume of 32 cubic feet. Let's say we want the boat to be 16' because it fits in the garage, 32/16 gives us a midships area of 2 sqft so if the pc is 1 then an underwater area of 2 ft wide by 1ft deep would do it. However that would be a canoe not an ocean going fishing boat. Four feet wide would be better, with a draft of 6 inches.

A pc of .66 gives us an area of 1.32 sq. ft , 1.32/4 gives a draft of 4" but that is still with square sides. Now square is OK, Phil Bolger, one of my favourite designers now sadly no longer with us, designed many square boats  but in this instance we want some flare in the sides, not much but some and we want to keep the draft at 6". So we need to lose .68 sqft (2-1.32). It turns out that if we do some complicated math we need to make the bottom about 16" narrower that the beam. 16" = 1.33 ft, notice a coincidence there?

Any way that's Jim's way but he was a rocket scientist. Me , I'm more of a "if it looks good it is good" kind of guy. My way  is to decide max length, max moulded draft, and max beam at the gunwale and fly at it.

I start with the waterline in profile and decide on a waterline length let's say 14' and max draft 6" amidships, Green is the water line.

Then I sketch in the bow and transom profile and add a sheer pleasing to the eye

That sheer could be a little  higher at the transom.

 Then I sketch a midships shape that I think will give what I want, red is the centerline and blue the midships shape

From there we can play around with the cartoon some more or take it to the drawing board to refine the lines and see if it makes the grade as far as displacement.

Next week the drawing board or computer screen, take your pick. I've tried both and computer is the way to go for me. You may feel differently and we'll talk about both.