Kayak - Construction journal - Drawing the forms

Preparations

Nick's book contains tables with numerical measures (in inches) that describe vertical 'slice' cuts of the kayak, at regular intervals (each foot - 30.5 cm). They are generated taking into account the use of wooden strips of 1/4" thickness (6.35 mm). If you can afford it, and want to skip the tedious job of drawing the forms yourself, Nick sells a set of high-quality printed plans ready for use.

The table contains a lot of numbers, but if we apply them all, we'll obtain a nicely defined curve.

There are two main types of points, and a few additional reference points, for each of the forms. The main points are:

The upper part of the tables contains height values, separated in one inch intervals from the center of the kayak. (Deck and hull)
The next part has 'reversed data', i.e. now they contain widths, for different heights (also each inch).

Near the cockpit area, some extra points are included for better definition of that zone.

Finally, a rather weird construction: a line has to be drawn starting 1.44 inch above the water line, and running downwards at an angle of 70 degrees from vertical. The number in the table indicates the distance from the start to the reference point. These points are supposed to help define the rather closed curves.

After some frustration at trying to plot inches on millimeter graph paper, I wrote a program that takes all the values of the table, converts them into metric, and also generates an input file to a graphic program (Skencil). I then used the graphic program to unite the points with bezier curves, and to correct small irregularities possibly due to rounding errors in the table.

This is form 2, showing the extra external form (gray)

Advice: Both if you buy the plans or draw them yourself, consider the following trick:

At least in the first and last 4 forms (1 to 4, and 15 to 18), trace a new curve around the original one, at 6.5 mm. This will be the inner border of our external form. At about 2.5 to 3 cm outside that curve, draw another one.

This 'ring' around the actual (inner) form will serve to press the strips onto the inner form, which I found an invaluable tool (check stripping the hull) The ring won't fit exactly at the same spot as the internal form, because the strips may be slightly thicker than 6.35 mm, and they're not lying flat.

Having the foresight to cut both at the same time, saves a lot of material! Of course, cutting in between (with a jigsaw) is a little more complicated. In the images below, you won't find the external forms. This idea ocurred to me after cutting the original forms!

Pictures

	An example of a drawing of one of the forms. Note the horizontal line representing the waterline, the rectangle for the strongback cutout, and the 70 degree line for the extra reference. The smaller marks at the side are the sheer line.

The forms, freshly printed and glued together, as they don't fit on the A4 pages of my printer! Still missing are the plans for the bow and stern.

	After a rough cut, these are the forms. Thinking green, I then cut them more precisely, leaving only about 3-4 mm outside the lines.

It hurts to see the amount of paper to be discarted after so much cutting!

Continues with glueing and cutting the wood.

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