Tools of the trade

Tools of the trade

Before launching into a discussion of how to go about transforming your cartoon to something resembling an actual design, we should talk about what you need to begin.

There are two ways to approach this question. The first is the traditional way with pencil, splines, french curves, triangles, a drawing board and lead ducks and the second is a computer and appropriate drafting programme.

How to proceed is a personal decision. Jim Michalak prefers the pencil and drawing board, others prefer the computer. I do most of my work on computer and some with pencil and drawing board but less and less all the time.

Lets start with the basics, a drawing board. A perfectly serviceable drawing board can be made out of a 2x3piece of half inch ply to which you can glue a similar sized piece of masonite or similar smooth material. On the edge of the board which will be closest to you fasten a yardstick. On the back of the piece of plywood, on the edge furthest from you, fasten a 3' 1x1 piece of any wood from your scrap bin, if you have a scrap bin. You now have a drawing board that can be placed on any table,with a slight tilt to make drawing comfortable.

You can get a basic beginner's drafting kit from Staples for $55.99, it does not contain T-squares but it does contain two triangles and with these triangles and the yardstick you can start to build the basic grid on which your design comes to life.

You will recall that first cartoon,

This is the basic grid, that one was drawn using grid paper. However we are going to draw one from scratch.

From the cartoon determine the scale, 1/2”=1ft, the water line length, in this case 13', and you're ready to start. Stick a piece of paper on to your drawing board, securing the corners with drafting tape, or painters tape, it works just as well and is cheaper. Don't use regular tape it tears the paper, what paper you might ask. I used to use paper banquet tablecloth, it comes in rolls 40”x300' and cost. between $25 and $55. That's a lot of drawings.

Using the ruler provided in the drafting kit measure up 6” from the yard stick at either end of the paper and join the two points.

This is your waterline (WL), I like to use a different color for the waterline , green, and centreline (CL), red, on the computer to avoid erasing them by mistake. However on the drawing board it doesn't matter all that much.

The WL needs to be divided into 10 equal parts, for this use the architects rule provided in the drafting kit. You can start at either end of the WL. But what length are the parts? We're going to draw 11 parallel lines, numbered from 0 to 10 so there are 10 spaces and 10 into 13' equals 1.3' which gives us a space of 15.6” (this is all way easier in metric), .6 of an inch is 9.6 sixteenths all of which is going to be headache making doing the measuring so now we need to make some changes to our cartoon design. If we round up the space would be 1-3-5 which is short for 1 foot, 3 inches and 5 eights which would give us a WL length of 13' 1/4”, on the other hand rounding down the space would be 1-3-4+ (the plus indicates add a sixteenth) and that would reduce the WL by a 1/4”, not much to choose between the two of them but 1-3-5 is easier to mark so we'll go with that. You can change the scale at this juncture so the drawing is larger and easier to work with.

Once the marks are made put your triangle on the yardstick and move it to the first mark. Draw a line, you can extend the line to the top of the paper by using the second triangle. Do this for all 11 marks.

 

Then number the vertical lines from 0 to 10, I like to work from right to left with the zero or bow end to the right, you might want to work the other way. Now draw another line 1' up from the yardstick and parallel to the WL, that will be your centreline.

You will end up with a grid something like this,

And there we will end for today.

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.

Experience starts when you begin - Pete Culler

Kuai Le

This is Kuai Le, a chinese like junk of my design and which I built over three years, it shouldn't have taken that long but life happens. My purpose here at Small Boat Design for Beginners is to take you through the steps that led me to this place and to show you that you too can design your own boat and build it if that is your desire.

Pete Culler said that experience starts when you begin so we will begin at the beginning.

In the beginning

Aspiring beginning small boat designers should start by studying the successful designers, those with following and fans, Phil Bolger comes to mind, no longer with us sadly, but his small boat designs are classics and sometimes whimsical but the majority of his small boats followed a particular credo. It is this sort of focus that a beginning designer needs to develop.

When I started designing I was in the Navy and designing small boats began as a way of filling time. Mostly they were doodles, ideas for boats rather than fully developed design concepts. This is the beginning.

A small pencil cartoon of a dory type boat but laid out in the classic way on a grid of waterlines, stations and buttocks, (really not needed in this type of boat but good practice). Barely visible at the top left is the scale 1"=2'. After I fully developed this concept, several years later, I built two of them for the Royal Canadian Sea Cadets in Prince Rupert.

Doodling boats is a great way to begin, you get feel for the type of boat you want to design and what looks good and what is down right ugly no matter what you do with it. As we go along we'll go from doodling to the bones and all the practical things that you need to consider and learn. But don't start with the big "How to design a yacht" books, you'll go crazy. Begin small and if you are satisfied stay small, some of the best small boat designers do only that and they're very very good at it.

So start studying other designers, start doodling and if you can do it, do some every day.

So endeth the lesson for today, more next week on setting up the grid and deciding where to go in small boat design.