Here's the space after the old box was removed. The square part measures 36"x18"x33" before insulation. The polygon shape at the end adds another 12" of length but I'm not sure if I'll include this space for the box, or see if I can fit the
compressor here.
I'll insulate with 3" of aerogel for R-30 insulation.
For construction of the box, I was planning on using thin
plywood or
fiberglass sheet to make a temporary shape of the box. There is a part for the bridge
deck that is a radius that I'll square off and I need to leave a chase behind the box to run power and
water lines. Once I am happy with the box shape, I'll wax it (mold release) and glass it essentially using the raw space as a female
mold for the exterior of the liner.
I can now take the liner off the boat and build the box working from the outer liner.
Construction: outer
fiberglass liner - 3" areogel insulation - plastic vapor barrier - inner fiberglass liner
The old box had reflective radiant foil on the exterior of the insulation, is this necessary? Is the vapor barrier necessary if the inner and outer liner are fiberglass? If it is necessary, does the vapor barrier go inside or outside the insulation or both?

