Saturday, March 24, 2007

Scarfing Keel and Hull Stringers

Today I moved my table saw and other tools from the garage shop to the newly-roofed building shed, along with the finished stem, skeg, and bulkheads for the first hull I plan to assemble, which will be the port hull. I only had a couple of hours to work today, but in this time I was able to rip some 18' by 3/4" Doug Fir stock into strips for the keel and the hull stringers that go on the top edge of the lower hullsides. Since these parts needed to be longer than 18', it was necessary to use scarf joints to extend them. Shown below are the four stringer parts that I used to make up the two long stringers, which are approximately 23' long. The fastest and easiest method I've found for cutting scarfs is to stack them with each one staggered back the amount of the scarf ratio, then cut the excess material down with a handheld power planer until a smooth "ramp" is created. This is further smoothed with a belt sander. Turn half of these around so the cut surfaces are end to end, and glue them together with epoxy.

Here are the staggered pieces, in the first stages of cutting down with a power planer. Since I wanted a 10:1 scarf ratio on these joints, the amount of offset is 7.5" (for a .75" plank thickness).

The finished ends after smoothing with a belt sander. (These are shown slightly out of alignment for clarity.) This is much easier and faster than it looks, and only takes minutes for the whole operation once you've done it couple of times.

The finished scarf joints clamped for glueing. Keel stinger on the left, two hull stringers on the right. These joints will be cured in the morning. I also sanded the epoxy coated inside surfaces of all the port hull panels, in preparation for a quick second coat. Then I will be ready to join the panels with the butt blocks and glue on these hull stringers.

1 comment:

Rob Granger said...

I loved your journal. Thanks for taking the time to build it (the journal and the boat)