Sunday, September 20, 2009

Ravn's keel, part two

I laminated two-inch wide strips of purple heart on my workbench. I wanted everything to be straight. The main assembly was a little more than 6 1/2-inches tall. At the forward end it had a space for the lead ballast keel. To make sure the keel went straight on the centerline of the boat I drilled two holes large enough for 5/16ths galvanized lag screws through the centerline of the keelson. Then I put the laminated keel up against carefully marked where the holes should go and used a self-centering doweling jig to drill the holes in the keel. I buttered up the bottom of the keelson and the top of the keel with thickened epoxy and my neighbor, Ray, and I lifted it into place. Ray held it steady while I drove the bolts in from inside the boat. It snugged down real nice.

I then clamped a plywood ramp into place and we slid and lifted the lead ballast keel into place. More thickened epoxy on all the mating surfaces and I drove four 3/8ths inch galvanized lag screws through the lead keel and into the purple heart wood keel. I packed the countersink holes in the lead keel with lead filings and filled them with epoxy. It was a good way to get rid of the lead filings and would add a little weight to the bottom-most part of the keel. I then fitted and epoxied smaller pieces of purple heart forward of the lead keel and drove a 5/16ths galvanized lag screw through them into the main wood keel. The result was that the lead was not only held in place with the four lag screws and epoxy, but it is dovetailed into the wood keel as well.

I did some shaping of the wood in the front to give it a nice, easy run aft. In the stern section I used some old-growth red cedar as blocking to fill in the skeg area. The red cedar is rot proof like the purple heart, but much lighter to keep weight out of the ends. It is soft, but I surrounded it with purple heart to protect it.

To form the stems I resawed two-inch wide pieces of purple heart 1/4th-inch thick for the laminations of the outside stems. I cut them to length, painted epoxy on each lamination and clamped and screwed them into place.

Finally, I cleaned up the glue squeeze out, sanded everything and used my router to put champers on each side of the bow stem and switch to a small roundover bit for the bottom edges of the keel. I then laid six-ounce fiberglass cloth over the bottom and wet it out. The cloth covers everything below the waterline making a total of two layers of fiberglass cloth over the strakes and three layers over the garboard-midstrake seam.

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