How much foam

i am going to build an 18' bass boat and i need to know how much foam i should use . i am really not sure because this needs to be know in order for me to design it. I also need to know he placements such as the stretch of the whole base or just a section. thanks

 

1 cubic foot of foam for every 60 lbs of boat wt (includes engine, and everything that goes into the boat. You will need to have enough foam around the motor area to float the motor (usually this is provided by filling the very rear corners of the boat with foam). The rest is spread out around the rest of the boat, some high, some low. The idea is to have enough foam in the boat so if it is full of water, it still floats level or slightly higher than the surface of the water (level flotation). 60 lbs/cu.ft. will give you more than enough flotation, because things weigh less submerged than in air, because of density. Better safe than sorry. Design in air cavities that total the cubic footage needed, then pour in 2 part expanding foam to fill the cavities. These cavities can be in unused corners, around live wells, in the bow, under the combing, under the seats, inside the consoles, etc.

Steve