Technical Notes on Securing the Deck:
The plans aren't clear how to construct the upper deck of the Martha Jane. The length is about 9.5 feet, the length of a sheet of U.S. measurement plywood plus a bit more.
I asked around, but didn't get any guidance on what exactly should be done, so I butted on two scrap pieces, to give the deck its length, while saving a little wood, as the hatchway would be cut out of the center of the piece.
DO NOT DO THIS!
I advise you to butt on one piece of extra plywood that covers the distance from the port to starboard side. This is necessary to get the proper crown shape to the deck.
My two extra pieces didn't allow this, giving me a pronounced dip in the upper deck.
To remedy this, I propped up the deck and stringers from inside with 2X4 lengths. The hatch rails and tabernacle braces straightened the deck considerably and held the shape. Note however that instead of the designed hatch rails I installed beefier rails (a 2X8 cut diagonally to the dimensions of the designed rails) that provided more rigidity.
This is not meant to be a criticism of the designed rails--a lot of people managed to build them so they worked. I just couldn't seem to do this, so I went with something that was easier for me to construct and install.
I also bolted the tabernacle braces to the deck with carriage bolts. These worked so well, the deck actually separated halfway from one of the stringers! A little bit of fill, and it'll be no problem. A slight dip remains, but I seem to be the only one who can see it, and then only on the days I feel particularly critical. I think it's going to be all right.
I love being able to walk across the deck (albeit stooped, as the tent is still over the boat) and not have it creak, pop, and bend!