Leak-free 5200 Bottoms

My first encounter with an old wooden boat involved helping a neighbor down at our camp on Lake Champlain “soak in” his beautiful little wood-planked outboard. Soaking it in meant exactly that. We launched it in late May, and Pete stood there watching as his boat quite literally sank until it was lying on the bottom in about a foot of water at the Lake’s shore. “There. We can come back tomorrow and pump her out and see if she’s ready to float.”

Well, finally she did float, but all summer Pete was plagued by leaks.

There had to be a better way! Fiberglassing the bottom would keep water out, but only at a high cost. Boats are in water and they ship water, or get rained upon. At least some of that water seeps through the bottom planking and sits there between wood and fiberglass. First the planking and then the framework rots from the wet side in.

Ahh…. then how about removing the entire bottom planking and applying copious amounts of West System Epoxy between the frames and bottom planking? Not only does doing so create a variation on the fiberglass problem, wooden boat hulls flex as they race through the water. West System does not flex, however, so the first hard hit translates into failed epoxy and, yes, leaks anew along with the rotting.

While SMB was still in its conceptual/research phase, I Googled “5200 bottom” and found the answer to this quandry in an excellent  article titled, “What is a 5200 bottom and why should I have one?” This article in the Antique Boatshop Web site offers a rich historiography along with superb and highly actionable content. The following excerpt describes what it is, and the balance of the piece will tell you why you should have one:

“A ‘5200 bottom’ as it’s known in the wood boating community is where you remove  the current bottom, make repairs or replace damaged frames and chines, tighten and/or replace all frame bolts….then use new mahogany planking supported by marine grade plywood as the inner layer sealed in a proper and flexible wood sealer. The new lumber is attached with silicon bronze fasteners and 3M 5200 adhesive in lieu of the lead soaked canvas between the inner and outer layer. The 5200 product comes in a caulk tube which is applied to the inner layer (marine grade plywood) before attaching the outer mahogany planking.”

AT SMB, the 5200 is also applied to the framework to which the plywood is attached, but only after all surfaces of the framework and marine plywood receive four liberal coats of Smith’s Clear Penetrating Epoxy Sealer.