In which a canoe is built, its progress described and photographed.

Saturday, December 1, 2007

2. Drawing the Forms

Nymph is a strip-built canoe. This means that thin wooden strips will be laid over temporary forms. The strips will run the length of the canoe. When all the strips are in place, they will be covered in fiberglass and epoxy, for strength, and the temporary forms will be removed.

Historically, before fiberglass and epoxy became standard, wooden ribs, perpendicular to the strips, provided the strength. (see below)

Sairy Gamp 1883 by J. Henry Rushton
(technically lapstrake, not strip-built? but shows ribs)

The first step I will take is to build the temporary forms. The forms are cross-sections of the canoe. Taking the table of offsets from the Wooden Boat article, I draw a grid, like graph paper, onto 3/4" MDF fiberboard. Then I carefully plot the "data points" from the table of offsets onto the grid. Finally, I play connect the dots. It's like drawing a graph back in high school (middle school?)

The horizontal lines of the grid are called waterlines, and the vertical lines are called buttock lines.

This process is a simplified form of lofting.

The form I am drawing in the picture is form #0, the middle form.
Nymph is symmetrical, so I will make one copy of form #0, but I will make two copies of every other form, saving a lot of drawing. That's good, because the drawing is pretty slow.

My roomate had an aluminum T-square, which is very useful for drawing the grid.

Next: Cutting out the forms
Then: Building the strongback

Update: 3 of 7 forms drawn (12/3)
Update: 5 of 7 forms drawn (12/4)

1 comment:

eric said...

How did you get your curves to come out?