The first step is to build the mold. The mold is made up of three parts. The first are the ribs which will give the boat it's curve. The second part are the stringers (?) which will run the length of the boat and give it it's overall lines. The third is the strong back, which will keep the boat straight and true.
Materials:
Half a sheet of 1/2 plywood. Can be rough. I got mine straight from a job site.
One bundle of strapping (pronounced s'crapping)
Two 2x8 at 16'
Tools:
Jig Saw
Table Saw
Circular Saw
Thickness Planner (You can use the table saw for this if you need to, but be careful)
Exacto blade
Chalk Line
Let's get to it!
First we're going to cut the plywood to make the ribs for the mold. What I did was photocopied 100 copies of the line drawings from the plans. Then using the exacto blade I cut each rib out as carefully as possible, and taped each one to the plywood down the center, so I could hinge it like a door to cut both arches. Using the exacto I then traced the arch onto the plywood, and cut with the jig saw.
Once each rib was cut I used the table saw with a dado blade to make grooves into which the stringers will be placed.
One mistake I made was to not mark all the grooves before cutting with the dado. Take a magic marker, and simply draw where you want each cut to be. while it won't matter in the overall shape of the boat, the mold is sacrificial, it will make your life easier.
Now with all the ribs cut, it's time to cut the strapping to size. I used the strapping for the Keel, the gunwales, and for making the mold. So, try to plan your wood use as best as possible. First I found the wood I'd use for the keel and gunwales, and put them aside. Using a thickness planer I brought the wood down to the desired thickness, and then ripped each piece on the table saw. Don't worry if they've got knots, well save the best pieces for the keel and gunwales, but for the mold, it doesn't matter.
Ok, two out of three steps done, man we're cruising!
The final step is to build the strong back. I chose to use 2x8's for this, mostly because I was surprised that they were reasonably priced. However, I've seen people make plywood strong backs, and that actually sounds like a pretty good idea. Either way, whether you do what I did, or make them from plywood, the point is to have something stiff and straight. I bolted the ends of the two boards together, and assumed that they needed to be made true. Using a chalk line I snapped a straight line onto the 2x8s, and then followed up with a circular saw to make the edge perfect.
Now it's time to put it all together! No wonder cooking shows make it look so easy, this all sounds so simple. Don't worry, in real time, this would be day two. This is where I got tired, and really wanted a nice cold beer. Feel free to do the same, or keep truckin'.
I used the leftover scraps from the plywood board, and screwed them onto the top face of the strong back. Also, I screwed the strong back onto the saw horses to keep it still. Then, I measured off the position of each rib, and screwed them into place, keeping them square to the strong back. With each rib in place, came the task of placing the strapping strips in the best puzzle like manner I could.
Cool. So this is where we have to end the first days work. We need to join the boards that will become the keel. Hopefully you've still got your good scrapping pieces. I cut a rather dramatic angle into each end, to maximize the overlap each piece would have, and then using some West Systems Epoxy glued them together. Then I drilled and put four brass screws in to hold it together while the glue set. This should take a 6-8 hours which sounds perfect for going home.
So once that is done, we've got the mold built! Not bad, no.
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