Once again, my log entries lag behind the actual progress....About 2 weeks ago I dry-fit the other half of the hatch hinge and start of the hatch frame and discovered that the large screw heads were bigger than the space allowed inside the hinge so it didn't lay down as flat as it should.
These were 1/4" x 2" pan head stainless screws so I had to find something else (I was using stainless in case to avoid corrosion years later and I wouldn't want to dig into the finished hatch to replace them. Elevator bolts or similar could have worked but I didn't find any stainless ones in the area or online that would take over a week to get so I figured I'd see if carriage bolts could work without too much deformation around the holes.
Since I have only one hurricane hinge on hand, I first tried it on some scraps of aluminum the same thickness as the hinge and I figured the deformation would be acceptable.
I also checked to see how much of the bolt head clearance I had saved - here is a scrap with one carriage bolt and one pan head screw set inside a scrap of aluminum angle showing a big difference so I had apparently solved my problem.
In dry-fitting the hinge with the top frame wood again it was much better but still didn't quite lay right. With careful inspection with a flashlight underneath I could see that the upper side of the bolt head was still hitting because it was too close to the hinge and didn't completely fall into the pocket apparently made to accommodate fasteners so I pulled the bolts back out yet again and ground down one side of the head.
This let met finally get to building up the hatch frame. My original rib plan was to use 7 - a double rib at each end plus 3 single ribs evenly spaced between them. Since I made 8 ribs I decided to use all 8 rather than the 7 I planned to use with 4 double ribs and make the ribs line up with the seams and fastener heads I already have in the roof above. Even though I made them from the same template, there were more small differences between them than I expected. I built the frame in place in the trailer get a good fit. Ribs are attached to top of the frame with pocket joints and Sika adhesive. This shows them with spacers, clamps and a sturdy scrap of 3/4" plywood to take the place of the eventual bottom frame member thickness.
The next day I sanded the ribs and attached the 1x2 poplar on the bottom and sanded some more to get the ribs as even as possible to one another.
I also re-discovered that the trailer frame and floor have a slight crown with the center about 3/16" higher in the center than on the right and left sides. This meant that the frame hits first in the center then the outside corners when pressing down. I had noticed this when installing the floor but that was about 2 years ago! I used a belt sander to take a little meat out from the center to reduce the difference and I may have to a little more later (one of my options may be to change the fasteners holding the rear threshold trim from rivets with big heads to either oval head or even flat head screws. I then installed blocking in the frame along the top and bottom with pocket joints and more Skia adhesive. I also put one block center to hold a light fixture to be installed later with pocket joints but no glue in case I have to move it . I ended up moving it because the chosen location would interfere with the eventual countertop edge.
I added a 1/8" luan skin to add lateral stiffness to the frame using staples and gorilla glue,
Here it is a few days later.