Hatch build questions

[calumet]

My solid walls are of ½” plywood. Do the ribs need to be ¾” as described in the plans? I intend to use 30 gage sheet metal for the roof with no plywood underneath. How do I make the transition from roof to hatch. If covering the hatch with the sheet metal as well, do I need plywood there because of the overhang?
Any detailed instructions on hatch locking handle installation and latches?

[calumet]

Since the Luan cracked, I am using 26 gage sheet metal for the roof and hatch. As far as the overhang, will this be ridged enough, with the ¾ channel , to support the weight of the hatch?

[mikeschn]

The hatch ribs need to be thick enough to eliminate springback. Ask anyone who has had to rebuild their hatch cause they skimped on the ribs.

If you have lots of 1/2" plywood laying around, glue some ribs together to make 1" ribs!

Mike...

[madjack]

....we glue up 2 pieces of 1/2" ply to make 1x1.5" ribs...for the hinge rib on both the hatch and body we add another piece of 1/2' to make a 1.5x1.5" rib and turn it so we are screwing into the side instead of the end grain or the ply...no ply should be needed on the body but because of stress placed on hatch, it should be ply covered and then the sheet metal...the hatch should be constructed to come within a 1/4" minimum of the body...you should have a notch cut along the sidewall where the hatch rests, this allows room for the trim and weatherseal
madjack

[calumet]

Thanks guys.
I built the hatch before receiving the replies so it is ½” ply for ribs with 11/2”x11/2” pine braces as well as top and bottom. When attaching the hatch to test for fit, I found that I had built it approximately 1” too long. I was following the generic Benroy plans and guess that I didn’t allow for the walls falling below the floor and attaching to the frame. So, I ripped the extra length from the bottom and sanded the floor edge a bit.
When looking from the side, the ribs protrude farther in the middle of the curve. Is this what is referred to as spring back? Can I retrofit with additional ½” ply glued in pieces to the ribs between the braces?
The hatch also does not came down square at the bottom but catches the wall on one side by about ¼” Since the hatch has been built for a while I am assuming it has warped a bit. Will attaching the 26 gage sheet metal straiten it? How do I make sure that the metal is straight and not attached to follow the warp?