A removable hatch with a viewing port for the common sump top has really needed a lot of thought. I think I have it now.

The size is OD 9.1″ X 6.65″ using .080″ Alclad 2024-T3. The lower section has a 1″ diameter ring as you see in pic 3. The edges were just drawn using French curves as you see in Pic 2. The viewing area will be 3″ x 2″ with a .3 overlap for bonding to the top piece.

There will be nutplates later on the bottom section. Theses are sealed floating nutplates and are used in GA aircraft fuel tanks. NAS1473A-08 (8-32 thread). I’ll probably use MS24693-S52, a countersunk machine screw. I’m using 14 fasteners.

Now the parts are cut out, match drilled and the top piece holes are countersunk. My next step is to prepare the tank lid for floxing in that lower ring. I also need to cut a square out of the top piece and mount some 6mm thick clear PVC as a view port.

I’ve set up a little test floxing some of the PVC to some waste 2024T3 just to be sure it adheres OK using the fuel safe EZ epoxy. Still a bit to do on this hatch.

Hatch layout

French curves

Drilled and cut stage 1