While working on the second float half, I noticed some lettering on the edge of my corecell foam that said "A550". This surprised me since I thought I had ordered and gotten A500 from Noahs, but upon checking the rest of my foam (way to go Jay - check the order six weeks after receipt) it turns out that it is all A550.
This discovery prompted me to go crunch some numbers. Using Ian's figure of 950 sq ft of foam to build the entire boat, I came up with the following total weights for different foams:
Pure A400 boat: 119 lbs
Pure A500 boat: 140 lbs
Pure A550 boat: 181 lbs
(these figures disregard the extra weight of HD inserts)
(Note, this is using the best-case (lowest) listed density for each Corecell variant, since Corecell actually specifies an allowable density range for each foam type: A400 density=4.0-4.6 lb/ft^3, A500 density=4.7-5.4 lb/ft^3m, and A550 density=6.1-6.7 lb/ft^3)
I can't draw an exact comparison since my boat will be a Frankenfoam boat (I have mixed foam densities) but still....60 extra pounds for using A550. I wonder what the expected load capacity of an F22 will be? The main F22 page on Ian's web site does not say (see specs at bottom of that page), and I don't know enough engineering to be able to infer or compute it. However, it's something I need to keep in mind: everytime you make a mistake (e.g., heavier foam, too much putty, tapes too wide, etc, etc) you're whittling down that load capacity number which will leave less room for beer, humans, food, and beer. :)