Building A Sailing Pram

I was looking for a new project to build. I wanted it to be a sail boat, but small enough for one person to lift and launch, and easy to build.  I had some designs of my own but while looking through them I found the plans for a small pram that had been designed for the American Plywood Association in 1958.  I had purchased them back when I was a teen, but had never gone beyond studying them. The boat was first designed by C. P. and E. D. Burgess, and later revised by Edwin Monk for the APA, as part of the APA's program to publicize the ease of building with Douglas Fir plywood.  Probably the best known boat from the APA is the Thunderbird.

However, the plans are for conventional construction and I wanted to do this one in stitch and glue, slightly modified.  Instead of stitching I would use boat nails to tack the hull together before gluing the seams with fiberglass tape and epoxy.  I do not want to fiberglass the entire boat.  This took some planning on how to proceed.  I also discovered that many details were left out of the plans, and some of the dimensions did not add up.  But, more on this later. So in a way it is my own design.

The plans called for three sheets of 1/4" Douglas Fir Exterior grade plywood.  I decided to use 6mm Okoume BS1088 marine plywood which is rather expensive but well worth the cost.  But more important, I had some excellent dark red mahogany wood recycled from a four poster bed made in the 1840's.  I would use this through out the boat.  In addition to trim and small pieces, the transom, rudder, skeg and part of the centerboard trunk are all of this wood. I also planned to use System Three Epoxy which I had great success with on the FL 12.

I might add that I live in a motorhome, and I am building boats in an RV park. So my work surface is a picnic table. That's why I call this Picnic Table Boat Building. This also affects when I can build and how much I can do. Plus I do not use a lot of large machines. I use hand tools and a few hand power tools.  My only large machine is a portable table saw that I bought specifically for this project.  I needed it to rip out strips for the miscellaneous parts.  They were taken out of the side rails of the bed. The weather has the largest effect, and here in the Pacific northwest it rains; a lot! This significantly played into how long this project took.

Fig 1.  Plans for the dinghy (click on the image for a large view.)

Initially I bought 2 sheets of 6mm marine plywood from Edensaw Woods.  Out of one sheet I cut out the two sides and two pieces for the transom, and out of the other sheet the bottom.  I went back and bought a third sheet to cut out the parts for the rear seat and forward seat.

Fig 2.

2 and Fig 3 -- From the head board of the bed I cut out the transom and the rudder.

Fig. 3

I built a jig, or strong back, to build the hull on. I used scrap lumber for this. I also built two molds to help the hull keep it's shape until the Fiberglass tape was applied to the seams. Fig 4 shows the jig.

Here is where I ran into the first problem. The plans do not show the angle of the bow and transom. However, from the plans for the jig it shows a measurement for the rise and run (horizontal distance and vertical distance) of the blocks that hold the bow and transom. From this you can get the angle.

Fig. 4

Fig. 5. Also, the plans do not give the actual length of the sides. It gives the curve of the top and bottom. But you have to fit the sides on, attach them and then cut off the excess. Fig 5 shows the sides extending beyond the bow.

The next step was the bottom. Of course they gave no dimensions at all for the bottom. So I measured the length and maximum width and cut a piece slightly larger.  This had to be trimmed down to the right size. Fastening the stern first to the transom and then then to the bow.

FIG. 6

Big problem!. The ply would not bend around that curve (see fig 5.) in fact the whole thing flew apart and had to be completely reassembled. The curve on the piece had to be lowered drastically to fit the bottom.

But I finally got it to fit.

Fig. 7

Fig 8.

This is what it looked like after the tape was put on. Initially I used a much heavier fiberglass uni-directional tape but it looked terrible and so I took it off before the epoxy could set up. I used 6 oz. 4 inch wide plain weave tape. After it was ground down and re-epoxied it was almost invisible. This is before it was sanded.

Fig 9.

This is my boat building "shed"  Of course this is the first time I had to move (nothing to do with building a boat) and I had to move 2 weeks later to another RV park.  The weather throughout this has been horrible. We have had about 3 or 4 days of beautiful weather and the rest of the time (about 6 weeks now) has been rain rain rain. It's raining as I write this.

The next step was to flip the boat and seal the inside of the seams with epoxy putty.

Fig 10. Inner seams

After this I installed the seats. According to the plans the front and rear seats were the typical platform type seats. I made them as sealed boxes, air chambers to provide flotation. The mid seat is a simple athwartship board. It is supported by cleats on each side and eventually the centerboard trunk. Unfortunately I did not photograph the seat installation.

Fig 10.

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