I did some more work this weekend extracting old insulation, with decent results:



You can see some water damage where old leaks saturated the insulation along the bottom and caused some rot on the wood down there.

I've learned a lot doing research since starting this project, and my plan has been revised somewhat. I will be lining the interior with foam insulation, and 1 layer of 1" VIPs inside of that. This will produce a box in excess of R-40, which is enough that the dominant source of heat migration will be along edges of the hatch and any other thermal bridges, not through the insulation itself.

I'll also be removing the icebox drain, as I definitely don't want the thermal bridge it introduces.

One final thing I'm doing is greatly expanding the space under the box through which the fuel lines, etc will pass. At minimum I'll be adding a few battery cables to enable low-resistance DC to flow forward to a (hypothetical) windlass, etc, as well as any boat wires.

Alex - you may want to rethink not having a drain. Anything you spill in there will collect and be a real pain to clean. You can always put a valve in the line downstream to open when you need it.

Hey Bill,

I'm actually okay with that. Adding a drain creates a significant migration path for heat into the box, and I'm designing to minimize the ways in which heat can get in. I feel like any spills should be cleaned up by wiping the interior of the box anyway.