Get On the Good Foot: Stitch and Glue Boatbuilding

The Core Sound boats are built with the "stitch and glue" method. Basically, this method involves joining sections of hull panels together with wire stitching and then epoxying and fiberglassing the seams. This makes the basic hull structure to which bulkheads and interior framing is added. It's really much more like welding than traditional woodworking.

So the first step for a boat of any length is to create long, continuous sheets of plywood from which the hull panels with be cut.

To this end, I first made a 20' long temporary workbench. I then set up my 3/8" plywood to be joined into one long panel. this involves what is called "scarfing." Scarfing consists of cutting a fine angle into the end of two sheets of plywood which can then be overlapped along this cut and glued together. The longer the scarf cut, the more surface area and the stronger the joint. My plans call for a 12 to one bevel.

Just about every online discussion about scarf joint eventually terminates with a various schemes to construct some sort of jig or cutting contraption to make the job easier. Now anyone who knows me will tell you I'm a fiend for doing things the absolute hardest way, but this seems a bit of overkill even for me.

I'll admit it was a bit tempting to cobble together some massive, medieval-looking device with big timbers, pulleys, and clanky ratcheting mechanisms to dangle a sheet of plywood just so over my table saw. But lacking a Quasimodo henchman, this did not seem the proper path. I digress...

Instead, I spent some time sharpening my planes.

And let me tell you, that was time well spent. Anyone who has spent any time using a plane knows what a big difference sharpness makes. Consider that in order to plane down plywood you will be spending half of your time (every other ply) cutting across the grain. If your plane is not very sharp you will be in for a VERY bad time. Seriously.

By way of illustration, think back to when you were a kid. Remember your first skateboard. No, not the bad-ass one with the pimped-out clear polyeurethane wheels. I’m talking about the one before that. The one with the cheap-ass metal wheels (or, God help you, the clay ones). Now remember what happened when you were trucking along down the road, perhaps getting towed by one of your friends behind his BMX bike. Yeah, you remember. You hit a damned pebble the size of a pinhead and it stopped those cheap ass wheels LIKE THAT. That’s why you have that scar on your chin, right?

Well that is pretty much what’s gonna happen to your plane if your blade isn’t sharp. Nuff said?

For me, the best way to get and keep them sharp is with the Scary Sharp method, which involves various grits of abrasive papers bonded to a sheet of glass. The planes blades are secured to a wheeled honing guide than is then rolled over the abrasive at a consistent angle. I use a General no. 809 guide.

I've heard of people building their own out of children's wooden car toys and the like. The General is adjustable which is nice for changing between the glass sheet and wet stones which stand taller, requiring a different angle. I keep this near the workbench and use it frequently.

So, after cutting a couple of these scarfs entirely by hand, it occurred to me that for some years now I have been the proud owner of a Ryobi hand power plane. It took care of the first 95% of the scarf cutting in about 5 minutes versus the hour or so I spent on them previously. I still did the final fine-tuning of the scarfs with the hand planes. But damn, I feel stupid.

Once the scarfs are cut, it’s time to join the panels which involves epoxying the two halves together with a mixture of thickened epoxy. The epoxy is thickened with either fumed / colloidal silica or wood flour which is added until the mixture reaches the consistency of peanut butter. Now I’ve read these same instructions from many sources and this “peanut butter” consistency has always struck me as a bit nebulous. So let me try to be more precise. We are not talking about that runny-ass hippy peanut butter that you have to stir for half a damn hour so it won’t make a greasy mess out of a slice of Wonderbread. No sir, we are talking good old Jiff. And not that crunchy stuff either.

Now one point needs to made absolutely clear. Even this thick mixture is going to run all over the place. It’s going to get on you. It’s going to get on your tools. It’s going to get on the cat. It’s going to get on just about anything you don’t want it to get on unless you take some time to set up properly first. This means covering everything in the area that you don’t want permanently bonded to your boat with plastic or the like before you even think about mixing up your epoxy. After trying various thicknesses of plastic wrap and wax paper I’ve have finally decided that the perfect film for this is plastic coated freezer paper.