Learning to plank – a great time as a CBMM Apprentice for a Day

It happens all too rarely, but I was able to cash in a Christmas gift and spend another great day with Chesapeake Bay Maritime Museum‘s Apprentice for a Day program. The current boat is an enhanced reproduction (a reproduction with some more modern updates incorporated) of GHOST, a deadrise bateau from about 1920. GHOST, a deadrise bateau GHOST's transomShe is a longtime fixture in the museum’s collection but has not, as I understand it, seen the water in that time. Little is known, therefore, about her performance. She is just shy of 16′ LOA with a beam shy of 6′. In her day she carried a sprit rig with 146 square feet of sail.

I found her reincarnation with two rough side planks clamped on to molds and an oak stem. Her chine logs and transom were in place – check out that upsweep in the chines and the laminated keel – as were the initial stab at that most curious of Chesapeake boatbuilding creations, the chunk bow.transom and aft end of chine log Chunk bow Rather than planking the forward portion of the bottom, where planks could get twisted and tricky, the builders took a page from the dugout-builders of yore and carved pieces from solid stock. Arduous, but it did the trick.

Our first task was to fit the bottom-most port side plank (the bottom will be diagonally planked).

It had only been roughed in to fit the rabbet in the chine log and chunk bow. It was pretty fussy. The picture shows it close, but not quite there. They are hoping, by the way, that that knot will disappear in shaping, but it looked rather ominous. Fitting the plank forwardIt was pretty amazing how much little shifts at the bow translated to big swings at the stern.

Bottom plank We did finally get it in place and then marked off the line of the chine, cut proud of it (funny looking thing, when laid flat!), and re-hung it with clamps. We then reset the sheer battens to get a sense of how she was shaping up. Our goal was to mark off the top side of this plank using the sheer as a reference. Trimmed plank Checking out the sheer

I will say in advance that this was a day I learned a great deal and, as with many cases of learning, the lessons sometimes came through mistakes. Here is where the big mistake – by all of us – began. We used a second batten to mark off a shape we liked for the top edge of the bottom plank or, as the planks on this boat will be flush, the bottom edge of the top plank. We then hot-glued scraps between the two battens to make a pattern for the top plank.Top plank pattern Choosing plank stock We selected a cedar flitch, marked the top plank on it, and cut the edge abutting the bottom plank.

Well, when we hung our new plank, it was immediately apparent something had gone amiss. Failing to fit the new plank If we closed the forward end up tight to the bottom plank, there was a yawning gap at the stern. If we tried to close that as well, the mid-section spring outward. This was not a job for a deftly wielded hand-plane. Something was extremely wrong.

What had happened? Well, if you haven’t guessed, go back to the picture of the battens laid out and the pattern being made with them. See anything wrong? The upper batten in the picture is on the bottom plank. The sheer batten is on the frame. We didn’t account for the plank thickness on the sheer! When we finally figured this out and rebuilt the pattern at day’s end, what a dramatic difference in shape. Lesson learned by all of us, but it took the entire afternoon to get there.

Mistake included, though, an extremely educational and fun day in the shop.

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