May 22, 2003: Adjusting and Installing the Bulkheads - Where to start - several weeks ago Roger and I did a "dry" fitting of one of the bulkheads. It didn't fit - it was to small by a good half inch on either side. My first thought was that I had made a mistake during the lofting process. I re-measured the bulkhead dimensions and they were correct. My next thought was that I had cut the bottom planks too large. I re-checked my plank measurements and they were correct. Finally I called Sam Devlin in Seattle, who is both accessible and helpful. Sam asked if I had "verified" or "proofed" the bulkheads before cutting them out. I explained that due to my shop size I had decided to cut all of the bulkheads out before assembling the boat. He said that it would have been better if I had cut out the bulkheads after the planks had been stitched together. That's because every sheet of plywood, every scarf, and every boat is slightly different. We discussed my situation at length and decided that adding shims to the bulkheads would be appropriate and would not compromise the bulkhead's strength. On page 95 of Sam's book he says: "After sheer spreaders are positioned at each major bulkhead station and the hull has been spread at the sheer to it's proper beam, you are ready to verify the bulkhead information. this is very important: Even if your designer has given dimensions and sizes for all bulkheads, double-check the bulkhead dimensions anyway. The characteristics of plywood differ,, and hull panels can bend differently boat to boat." Good advice. Sam goes on in the next several pages to give an in-depth description of the best ways to verify bulkheads.
All of the boats I have built to date have started with building a strongback, mounting bulkheads on the strongback, leveling and plumbing the bulkheads, and applying planks to the bulkheads. This process is relatively straightforward but has a few disadvantages i.e. chine logs are needed to connect the bulkheads and to provide a surface to which the planking is glued and screwed. The advantage of stitch and glue is that the chine logs are replaced by taped and glued joints which are strong, are flush with the hull, and don't collect or store water.
Anyway, we spent the week gluing shims to my bulkheads and refitting the bulkheads to the hull. Concurrently we spread the hull and fitted the motor mount bulkhead.
|Before fitting the bulkheads I placed a spreader across the bottom planks of the hull. The spreader is a j-bolt that is goes through a piece of scrap plywood under the hull and through a 2X6 inside the hull.||Roger does a dry fitting of the cabin bulkhead. It doesn't fit! It's too small.|
|Roger and I fit the motor mount bulkhead which, with a little trimming, fits. Here Roger holds the bulkhead while I drive a drywall screw through the side to hold it in place. Note that the level line has been raised to a higher position to accommodate the installation of the bulkheads.|
My next page will show the adjustment and installation of the forward bulkheads.