Rebuild – batten seam carvel plank

The O.K. Clark was built using the batten seam construction method where the seam formed as two planks, meet edge to edge and then backed up by a batten. Batten seam is a modification of traditional carvel or smooth plank construction. The method became popular in modern boatbuilding because, if done correctly, it produces a hull that can be launched and sailed right from a trailer without requiring several days of swelling as is typical with traditional carvel planking. Chris Craft and similar boats built in the 40s, 50s and 60s made great use of the method, producing strong lightweight hulls that have lasted for decades as evidenced in the ACBS shop now.

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The Clark developed serious problems with seams that could no longer be made water tight as a result of the thinner battens used in her original construction. Several large checks in the planks below the waterline were also a source of serious inflow of water. While we attempted to stop the worst of these, our last effort at getting her sailing revealed too many cracks and holes to safely keep her afloat. The decision to haul her out and put her back on her trailer was made with grave concern to her ultimate fate.

Rebuild options were considered. Since she was non-traditional in her original construction and not an historic boat there was little pressure to rebuild her as a traditional carvel built “replica”. Replacing the original planks and battens seemed a waste of time because, while her planks had grown thin from sanding, and her battens were too light to suffer refastening, there was no sign of rot in any of her wood. Her bronze fastenings were in fine fresh water condition. Thus the decision was made to go ahead with a modern matrix skin, to retain as much of her interior as possible, while giving her a new exterior.

The process was pretty straight forward. The hull was emptied of any nonstructural elements and then rolled over. It was then aggressively ground free of any paint. All of the seams were reefed to clear any remaining paint, putty, or seam compounds. A couple of lengths of planking were replaced because they’d been deformed from sitting on a trailer for so long. Gump wedges, long cedar strips ripped into a slight wedge shape, were cut, coated with epoxy and tapped into the now gaping seams to make the hull a near monocoque structure. All deadwood was sawed away following the rabbet from the stem head right back to the sternpost. A hog (drooping) that had developed in the original keel from the boat’s long stay on a trailer was worked out with planes and some pushing. The hull itself was faired, first with planes, and then with coarse sand paper and long boards leaving a skin thickness that averaged about a half inch throughout, with an additional 5/8” where the battens backed up the now solid seams. The centerboard case, which caused enough leaks by itself to sink the boat on her last launching, was unbuilt and removed. The hull was coated with a straight epoxy mix, followed by a thickened fairing mix to fill small gaps and voids in the old skin.

Veneers were then glued on with monel staples serving as mechanical connectors to the old hull. Clamping devices were needed to get good surface to surface fits between the old planks and the new veneers. The first layer went on diagonally at an angle to the sheer and from sheer to rabbet. This was done to add sheer strength and to help bind the original planks together in the new matrix. The first veneer layer was washed, and faired to prep it for the second layer. The second layer was planned with veneers laid in to match the original planking from the sheer down to just below the waterline. Some spiling was done to get pretty fair lines to any seams that became obvious from printing through, as is frequently the case in cold molding like this, where boats had been laid up for a few years. This process would provide the boat with stability and appear to be traditionally planked. From below the waterline down to the rabbet, veneers were fitted in as diagonals, opposite to the first layer beneath them. This allowed for efficient use of materials since cut offs could be used for these short runs, and because we felt that it would make for a stronger matrix.

Considerable time was spent planing the old keel surface and raw edges of the new skin in preparation for the new hackmatack plank keel. Again, the hull was epoxied, washed, faired, and finish sanded to get it ready for the layer of glass cloth that was applied, set in, and then faired with thickened epoxy. The glass work was done so that it was contiguous across the faying surface for the new deadwood pieces. Te cutwater included a curved chunk at the bottom where it tied into the plank keel. Since not a single solid piece of hackmatack was anywhere to be found from which the whole piece could be cut, a lamination was made up for it. Bronze bolts, fabricated in the shop from 5/8” rod stock, were used to attach the new cutwater, plank keel, and stern post which were all bedded in a big sticky smear of 3M’s tenacious 5200 adhesive caulk.

An all new centerboard case was built and fitting it’s bed logs was probably the most difficult part of the job since it was installed offset against the side of the keel as originally built. The bedlogs are large chunks of heavy white oak and the bottoms of both pieces had to be cut in a slight curve that was also angled to ft the changing “V” of the hull. The whole big heavy structure that became the completed case, had to be manhandled in and out many times during the fitting and fastening to ensure a good ft.

Once the case was installed and after the final fairing of the new hull, the final finishing included a lot of reassembling of the original furniture. Te O.K. Clark appears now to float a little higher than before due to the new matrix, which does not soak up as much water, making the O.K. Clark lighter than the original boat used to be. Te hull is now about a solid inch thick and near bullet proof after this careful rebuild lead by Gary Kresser, assisted by Dick Wiesen, Mark McQuestion, Brian McGowen, Don, Paul Markwart, Jim Kolbe, and some BOCES students, who added more than their fair share to the project. The O.K. Clark is docked at Canalside, in her original luster and charm.

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