I needed a clean flat-ish surface to mount some very big photovoltaic panels onto, and there just isn't enough real estate for all that other stuff up there. After cutting through a live 120V wire with a jig saw (oops!) I decided a skillsaw set very shallow and a grinder with a cut off wheel were the right tools for the job. Never having done this sort of work before, I'll admit to hours of baking myself to death on the roof in the direct sun while I endlessly climbed up and down the ladder to get more tools. At the end of two days of frustration and cursing, there was nothing left to remove, and me and my lovely assistant Georgiana built cover plates for the interior, painted them, and riveted them onto the underside of the roof, but cover plates weren't the only thing we added.....
I've seen some amazing custom stainless steel and glass hatches online, but these are all custom fab jobs and at custom fab prices, so peasant airstream hatch shoppers are pretty much limited to lewmar and bomar hatches. I chose a lewmar medium profile hatch, and set it into some nice clear fir that I milled myself a few years ago. The process of putting it in went something like this:
Build a wooden curb to bridge the gap between the upper and lower layers of aluminum.
Cut an aluminum flashing sheet to sit atop that. Paint or finish both pieces.
Cut a hole in the roof that the curb will just fit into, while trying not to cut through any major structural members or electrical runs. This is harder than it looks with the major electrical running down the length of the roof.
Use the cutout from the aluminum flashing to mark the hole on the underside inside of the roof. Carefully cut that hole out.
Shape the curb until it fits perfectly with the curve of the underside roof, and as much as the hatch can handle it, shape the top side too.
Put butyl tape on the bottom of the flashing perimeter, already pre-drilled for rivets at 1 1/4 inch spacing.
Set flashing atop wooden curb/spacer, squirt a big bead of 5200 onto the inside perimeter where the hatch will sit and bed the hatch down in it.
Pilot and set appropriate fasteners, I used #12 1 1/4 stainless screws.
Drill through flashing, putty, and roof and set olympic rivets around the perimeter, trim and grind rivets with insanely expensive rivet head grinder.
Seal the edge of the flashing with self leveling caulk.
Go to the underside and screw the metal to the curb.
2 days and about $500 later, Voila! Hatch!