How Do You Build It?

So how do you build a moth? Well, there are lots of ways, some easier than others. My goal was to use a construction technique that would be simple and cheap and yet relatively tough and light. I really like Phil S’s technique using tortured marine plywood. But my design not only called for torturing plywood, but also creasing it. So how do you fold plywood? I wasn’t sure, but I had some ideas. These ideas needed to be tested before I finalized my design. I got several 2’x2’ sheets of 3mm Okoume marine plywood and began to test folding techniques. After just a few tries I found that plywood can be folded pretty easily. Here’s what you need to do, first you need to groove the plywood where you want it to fold and remove enough material from the back side of the fold so that it does not bind upon folding (about 60% of the 3mm ply for a 90deg bend) Then you wet the wood and heat it with a hot iron. After you do this you will find that it folds pretty easily. Let dry and then glue on place. Done. First obstacle down.

After working on the folding technique I went ahead and build a 1:8 scale model of the boat with the 3mm ply. Turned out pretty good I think. I was also able to use this model to estimate the weight of the basic hull (no internal frames or deck). 13lb. Not bad. Granted I still need to add a lot of stuff and the final hull weight will probably be +2x that weight, but it’s an ok start.

While plywood construction is pretty effective for a job like this, it will not be as light as a fully vacuum bagged carbon foam construction. Also, the raw plywood is not great on durability so I intend to give it a single layer carbon skin over the hull on the outside only. This will present some construction challenges and add some weight, but it’s probably worth it to make a boat that will last.

Next Time – Parts and Pieces