Bob Easton

Chocolate powered woodworking

Fiddlehead

Bulkheads

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Now that the workbench is done, it’s back to the Fiddlhead. We left off with a stack of resawn cedar.

Harry wants the bulkheads made up by laminating 1/4 inch thick pieces, making each bulkhead a 1/2 inch thick two ply board. Back when I did this for the model, my first result was a pair of bulkheads that curled up like potato chips. Learning from that, I took a more cautious approach. I resawed only to 1/2 inch thickness, not all the way to 1/4. I then did the lamination in two stages, edge to edge first, and then face to face.

The shop is not normally heated, and this week was very cooperative with overnight lows that did not reduce the shop below the 60 degrees needed for West System epoxy. After laminating, I planed both rough boards to near-final thickness; quick work for the big #7 plane. The elipses for hatch openings were cut with a fiddly old coping saw that’s now headed for the trash. Finished with a cabinet maker’s rasp. Handling these, I now appreciate Harry’s intent. They are unbelievably light, much lighter than they would be if made from regular 1/2 inch plywood. The cross grain lamination adds strength over using raw cedar.

The round piece shown in one of the openings is part of a hatch cover, another clever device that Harry designed. Clever, but devilish to construct.

Update – Nov 11, 2008: In only a couple of days these bulkheads have acquired a warp. They didn’t turn into potato chips, but have about 3/32 inch of curl. I don’t like it, but will leave them as they are. It’s probably not enough to make the boat tend to the left.

warped bulkheadUpdate – Nov 20, 2008: More curl. They’ll be potato chips soon! A pencil can be rolled under either of two raised corners. I really don’t want to rebuild these, and I want even less to substitute plywood. I wonder what would happen if they got a good overnight soaking and then dried out under weights. Then again, it probably doesn’t matter that they are warped. The critical edge, the bottom, is still straight.

Another Way to Get Out Parts

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There are two watertight bulkheads in the Fiddlehead. The plans want them laminated from thin cedar boards. Why laminated? Laminating cedar with the grain of each lamination running in different directions keeps the incredible light weight while adding strength. Yes, they could be made from half inch plywood, but would be much heavier.

Building a model exposed the details that were very helpful when buying wood. damaged cedar lumberWilliam, the very helpful guy at M.L. Condon Lumber, was a bit surprised when I said “OK” to a board that had some very obvious cracks, and really nasty edge damage, in the middle of its length. He knew I was building boat and probably assumed I wanted only good long boards. I knew that board would be just fine for getting out the bulkhead parts. William saw it as damaged goods and discounted its footage appropriately. He got rid of a “reject” board and I got bulkhead parts at a bargain price.

Getting them out of the wood requires thickness reduction, like the frame parts described earlier, but done differently this time. Instead of planing off excess wood as waste, I resawed these parts. Resawing is cutting the wood into thin layers. I don’t have a nifty frame saw for resawing like the one used by one of Dan’s friends, (need to make one of those) so I used my bandsaw.

My bandsaw can be opened up to handle 6 inch material, plenty wide enough for the bulkhead parts. Rough cut some slabs out of that cedar board. There was enought wood beyond the damaged area to get the four slabs I wanted.  Joint an edge on each so they will run though the saw. Slice them in half.

resawingresawn stock for bulkheadsI’ve used the band saw a couple of years with the original blade. A trial at resawing with that blade produced some very rough results, completely unsatisfactory. The answer was a Wood Slicer resaw blade, available from Highland Woodworking. Wow, what a differnce! The effort to push the wood through the saw is only about 1/3 of the original blade. The noise level dropped by more than half; no more squealing. The resulting cut leaves two very smooth surfaces. These need very little smoothing. They are now cut to half the original lumber thickness, a good bit thickner than needed. I’ll deal with that after laminating.