2lb/cuft * 4.5cuft = 9lbs
3lb/cuft * 4.5cuft = 13.5lbs
4lb/cuft * 4.5cuft = 18lbs
FL_Cracker doesn't use any foam in his surf ski...
I am planning to use polystyrene foam in mine. it's lighter, strong as hell and will NOT absorb water, but it comes in blocks that need to be cut and...