It was 90 F when I foamed my hull. I had the heater blasting the hull surface to also help. I feel I actually got good expansion. I waited for that reason. I also heated the buckets of foam parts to help as well and worked in small batches.
We are not foaming this winter just a discussion on the processes of ways it can be done and sealed inside the boat. Hell I am hesitant to do glass work this winter. The math works as I said, if I make a cavity to hold X amount of volume and it only swells to 50% then I have only covered 50% of my volume. SimpleRemember that foam expansion is a direct correlation to the air & surface temperature of the cavity you are filling. You can do all the math you want, but if it's not above the foam manufacturer's recommended temperature for maximum expansion, your yield can be much less (like 50-60% of what you are expecting to get). Ask me how I know.
What was the outside air temp?
90F. I used the heater to get everything above that temperature for good measure. I was cooking that day lol. It was sometime in July when I did it. Maybe 110F total?
?? Where do you get the 60 lb per cubic foot figure? That seems a bit too high to me. Flotation is (I'm probably preaching to the choir) based on the weight of water being displaced. ... did my research ... OIC! Web says 1 cubic ft of water is 62.4 lbs. Foam that weighs 2 lbs.. leaves 60 lbs for flotation. Got it.
Quick Est. // If your boat is 8 ft wide, and 16 ft long (divide the tapperd forward section by half) so roughly 13 feet length wise, (doing the math) looks like you need about 3" of foam under your deck. That should be doable! (thumbs up)
61.5" or 71.5" is the beam 16' 1" center line. My center stringers I cut to 3" and the others are 2" in height. Might need to fill the stringers also will see.