The plans for this particular boat described how to build and install a deck mounted hatch. I decided to forego that option and instead use the aft bulkhead for access. Various reasons prompted this, but we'll save that for a later article.

I was intimidated by the execution. The trick would be a smooth and fair hairline cut that would allow use of the cutout part as the hatch. My jigsaw skills are sketchy at best, and tearouts and splintering seems the rule. And how to start the cut without widening the 1/16" kerf?
At the Wooden Boat Festival in Port Townsend I talked to Tom Regan, a skilled builder from South Puget Sound. He had access ports on his amazing Oughtred double enders with the cutout as the hatch, and gave me the idea to use a special japanese saw called an Azebiki to carefully plunge cut thru the ply (the funny stubby one on the pic).
Not one to pass up an opportunity to aquire new tools, I promptly ordered a specimen from Lee Valley/Veritas. It worked very well, and has the potential for many other weird tasks too. A japanese holesaw (which I already owned) replaced the jigsaw part for the bulk of the operation. It produced a clean and tiny kerf, tracing the line perfectly without wandering. Still this is a job requiring outmost concentration.

To hold the hatch in place I decided on 4 locations along the periphery for toggles. Also from Tom came the idea of using bits of brass half round leftover from keel rubrails. By raising the toggles on disks of 3/16" marine ply, I hope to provide a better grip when fingers are wet and cold and also avoid scratching the paint by repeated use.

The seal is a line of 1/8" sticky back weatherstripping from Ace.

For a handle I used a scrap piece of walnut, and the back of the hatch has some reinforcing to prevent warping.

All in all it is almost certainly faster to do this bulkhead hatch as opposed to the framed, raised job up on deck. Cheaper too, not requiring hinges or other store bought hardware (besides the Azebiki).