Wednesday, December 20, 2006

Layout and Cutting (Measure twice, cut once)

The hull is drawn in scale on one sheet of the plans and it is necessary to transfer the measurements from the plans to the plywood. This is what is referred to as 'layout'. Working from plans with the exact dimensions indicated as 'offsets' is much easier and faster than just working with line drawings that would require lofting to get the offset measurements.

The bottom of the Jimmy Skiff ™ hull is drawn on the plans with offset dimensions, which are indicated at right angles to a center line. I started by using a chalk line to mark the center line about 20 inches in from one side of the 9mm panel. Next was marking off the stations or intervals for each offset. On the Jimmy Skiff ™, there are six, 24 inch sections beginning from the bow, and then a four-and-a-half inch section at the stern. I marked off the the stations along the center line, then used a large carpenters square to mark the offsets out from the center line. The square ensures that the offsets are all at right angles to the center line. After the offset points are marked out, I used a 14' long, 1/2" pine quarter-round as a batten. I temporarily drove 2" finish nails in where the offset marks where, then used the spring clamps to hold the batten with the flat side against the nails. Then simply drew a line along the flat side of the batten. The side panels were done in a similar manner, except that the offsets are measured from a baseline rather than a center line.

I used my cordless jigsaw to cut out the panels, bulkhead, seats and stern. I cut about 1/8 to 1/4 inch outside the line, and then used a sharp block plane to plane to the line. This makes a very clean and 'fair' edge. The seat supports have inside curves, so I used a spokeshave to plane this to the final line. The CLC plans for the Jimmy Skiff ™ have full size templates for most of the parts other than the hull itself.

I used an awl to poke through the template lines about every half-inch, then 'connect-the-dots' with a pencil prior to cutting. Cut out all of the panels and parts before moving on to assembly. Note in the photo that the seats are wider than the bottom. The bottom is about 40" wide at the widest point, whereas the beam (overall widest point on a boat) is 50". This is because the sides will flare out from the bottom.

I built a couple of very stable saw horses for the boat construction. Then I padded them with some egg crate foam I had left over from when I 'sound proofed' my dust collection closet. The foam will keep the hull from getting scratched and dented during construction. Next post will show the stitching of the hull...

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