The Strongback


How do you build a boat upsidedown when the keel and waterline are level, the deck is sloped 7"s from bow to stern, and the garage floor slopes 2 degrees in the opposite direction as the boat?

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I built a strongback. Two 2x6's sistered together, level and square, epoxied to the floor. It was always my intention to deck the boat with 1/4" Marine plywood, laminated to 3/4", then apply the 'decorative' decking strips in a similar fashion as David Goodchild had done on his Toad Hall.
Having no schedule for deck beams (stringers), I decided that I would need two stringers to support the plywood seams of the first layer. the next layers would be lapped, and at that point the deck would be self-supporting.
The strongback is 47 1/4"s C.to C., which is 48"s over the arc of the deck. The stringers are 2x4's ripped in half, and rabbetted together. The slope of the deck was achieved by placing short 2x4 risers below the stringers at the stations to transfer the load to the strongback.


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The frames now had to be notched for the new deck beams. To be sure that all the notches lined up, I stacked all the frames, lining up the centerlines and the deck beams edges, and screwed them together temporarily. Then I built a double-legged T-square from some 1 & 1/2" aluminum angle, 10' long with two 2' legs spaced 47.25" O.C. The top frame was marked and the lines were transferred down to the bottom frame with a square. The notches were cut with my trusty Bosch sabre saw.

Finally, time to build a boat!  [990612almostkeeltime120x90.jpg]

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Copywrite © Alan "Maddog!" MacBride 1999
Most recent Revision 12/18/99