This is the first video of the FRS12 ‘how to build a boat’ series where we build a plywood boat. We cover building a plywood scarf jig and cutting a plywood scarf joint using a router. These plywood boat plans and more are available for purchase, and come with full size patterns.
How to Build a Plywood Scarf Jig
We use a one inch piece of plywood, two 2x4s and a half inch piece of plywood on the sides to create the angle. The center plywood is screwed to the 2x4s and the sides are fastened on an angle. We generate the angle by knowing the length of the scarf is three inches for the 3/16″ thick plywood. We set the sides based on the angle, so we can get a cut that goes from zero to 3/16″.
To find the angle, we can use a scrap piece of wood and measure it, use an angle finder, or if we know the degree that the angle should be, we can use an angle finder with the degrees already labeled on it.
We set the front up at the same height and we’ll raise the back so they are parallel and the correct height.
Using a Router for Scarfing Plywood
We mounted the router to a piece of PVC board, using dissimilar material because they slide better. We used countersunk holes to mount the router.
The height at the front of the jig is also the same height we set the depth of our router bit, so when we touch the router bit to the front of the jig, it just barely touches. When we cut the scarf and pull the router back to us, the router slides up the hill and creates the scarf cut. When we move the router, our wood will have a scarf cut in it.
We will adhere our plywood down with screws and fender washers to ensure the wood doesn’t move. Make sure the fender washers are far enough back that the router doesn’t hit the washers. It could ruin your router bit.
Aligning Wood on the Scarf Jig
Once we have the jig set up ready to scarf, we will align our wood flush with the edge of the jig. We made a three inch mark, for the three inch scarf and have screws and washers holding the plywood down. We have supports off the back of the table to hold the other end of the plywood.
We’ll bring the router and work from top to bottom to cut our scarf. If we make a mistake – we have a bur, so something we don’t like – don’t worry about it. The sander will take care of it, and if it’s a low spot, you can fill it in with epoxy.
You can build your own boat using our plans and instructional videos documenting exactly how to build a boat! Check out our plywood boat plans for the FRS-12