Hull

Building the hull – Summer of 2018

Six sheets of 1/4″ and one sheet of 1/2″ Okoume marine plywood. With careful cutting, I ended up with half a sheet of 1/4″ and a number of offcuts worth keeping for future projects. I ordered the wood from Boulter Plywood who seemed to have the best prices even after including shipping.

Originally I was going to have all the parts CNC cut on a buddy’s router, but he was having trouble getting it all set up. I was anxious to get the project started, so I just drew everything out by hand. All you need is a square, straight edge, ruler, and flexible batten for curves. The plans were originally in metric, but Ross has converted them to imperial. There are a few places where the sub dimensions don’t add up to the overall dimension, but that’s due to rounding and is never more than 1/16″.

Some of the bulkheads have holes cut out for ventilation or hatches. I made a quick beam compass with two nails and a scrap of wood. It’s important to cut limber holes so water won’t get trapped and cause rot problems. I used a quarter for the radius which seems about right.

The first daunting challenge of the build was to scarf four 4’x8′ pieces of plywood into two 4’x16′ pieces. First I screwed the sheets together making an 1:8 set of stairs to set the correct slope. Some people do 1:12, although that eats up more length and I’ve had no trouble with 1:8.

Once the slope is correct and the sheets are screwed together, I took a plane and knocked off the corners until I had a nice flat surface. This plane was absolutely not the best for the job, but my other planes were at my shop and I couldn’t be bothered to go get them. It did work however.

Frequently check with a straight edge to make sure all the humps are taken out.

Next I epoxied two sheets together with thickened epoxy. First, put down plastic underneath so it doesn’t stick to the floor. Then, saturate each face of the scarf joint with neat epoxy so it really wicks into the fibers. Then slather on some thickened epoxy and weight the joint down. I just sighted down one edge to get the sheets parallel.

The edge wasn’t perfectly straight to use as a datum, so I struck a chalk line. I measured from that to a number of different points along the hull plank where I then drove a nail. Then I used a piece of flexible shoe moulding as a batten to make the curves.

After a ton of work I had all the hull planks and bulkheads cut out. You can see how the hull planks will be forced to form a boat shape when their edges are brought together.

Here’s the pile of parts on the left, and bulkheads/frames on the right. It’s pretty cool that the pile on the right looks just like the body plan in a line drawing, other than the lack of bottom rocker.

These have been the heros of this part of the build. A jig saw to roughly cut out the parts, and a small plane to take the cut down to the line.

The beauty of stitch and glue boats is that there are no jigs or strong backs required to build the boat. You just stitch the panels together with zip ties and the shapes form the boat. This does require accurate panels though.

Adding the whisky plank! Somehow I think this is a more meaningful milestone for strip builders.

Once I got the hull formed I propped in the bulkheads just to see what it looks like.

The bulkheads required some 3/4″ stiffeners in places that I epoxied on. Once those had cured, I stitched the bulkheads in place. In “real” boat building, the edges of parts that contact the hull are beveled so they sit flush. This bevel can change (rolling bevel) along the curve of the hull which can make it complicated. In stitch and glue, you just put your bulkhead fore or aft of the line and fill the resulting gap with thickened epoxy.

Next it was on to fiberglassing the seams. I “tack welded” between the zip ties with a little blob of thickened epoxy and once that had cured, I cut the zip ties in the area I was working. I put a coat of neat epoxy along the seam, a bead of thickened epoxy, a strip of 4″ x 12oz tape, and then enough neat epoxy to make it go clear. Not too much, or the tape can float off of the wood.

I tried a few different ways to apply the thickened epoxy. Originally I used zip lock bags with the corner cut off, but I had trouble getting consistent fillets and the bags would rip. Plus there seemed to be a lot of waste. I later switched to spooning on the epoxy with a putty knife, and then using a plastic squeegee trimmed into a nice radius. This was a little slower, but I think it was more controllable.

Finally I had all of the seams taped. It was a long slog getting all of this done. Each section of the boat had to be done at once and it was hot which made the epoxy kick off quicker.

 

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