Big update time. Spent pretty much the whole day working on the boat (except the part that got over 92` in the garage...)
We'll start out with the piano hinge that I sourced from eBay, 1" per side with pilot holes every 2". With shipping I got 18' for around $38. Since I wanted to be able to take the hinges off to put the carpet on I decided to use button head screws instead of rivets. In order to use the button heads I had to countersink the hinge panels.
Made this little jig for the drill press.
Countersunk all the holes on both sides so the button head wouldn't keep the hinge from closing.
Mounted...
Closed... Yes a worthless picture, but you get the idea.
Now to set the hinge height I mocked up a peice of scrap decking and a plate to set the height. You don't want the hinge too high or two low. Too high and you'll burn your footsie or stub you big toe. Too low and the hatch may not close right.
I used about a dozen vise grips to hold the hinge level onto the frame and then drilled and tapped every other screw hole in the hinge and placing a screw every couple screws to keep the hinge from moving while tapping.
Then I placed the hatch into the hole and marked the hinge and hatch. Pic taken after removing the hinge from the framework.
Set the height, then clamped and drilled the empty holes vs. the framework.
And, closed
Open
One side note, I asked for carpet samples before getting the hatches bent up. 1/4' clearance on the sides and roughly 3/8 at the hinge will give a comfortable fit with 16 or 20oz carpet.