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Q. I'm making a pontoon boat from empty 55 gallon drums. How much foam
do I need?
A. Each 55 gallon drum requires about 8 cubic feet of foam. Since
each cubic foot weighs two pounds, you will need 16 pounds of foam per
empty drum. Therefore, it will require about one gallon kit (makes two
gallons) per drum.
Q. Can I brush or spray the liquid foam onto a vertical wall to provide a
uniform thickness of insulation foam?
A. No, the liquid foam will just run to the floor, then rise. You
will have a big blob of foam on the floor.
Q. Is this foam compatible with styrofoam?
A. Yes - it will not "eat" or dissolve styrofoam. If you have a large cavity to fill, it can be worthwhile to put some chunks of styrofoam in the cavity to save foam.
Q. How do I know how much foam I need to float my boat?
A. Great question! Get your calculator ready, you will need
it. A cubic foot of urethane will float about 60 pounds of "dead
weight". The wood parts of your boat will probably float, so you
don't need flotation foam to offset that weight. The fiberglass parts of
your boat will barely sink, so you really don't need much foam to offset the
fiberglass- maybe one cubic foot of foam per two hundred pounds (or more) of
fiberglass hull. The metal parts of your boat are what you really need to
account for. A small (4-6hp) outboard may weigh 45-55 pounds. A 50hp outboard will weigh about 200 pounds.
So a 16 foot fiberglass skiff with a 50 horse outboard will need about six cubic
feet of foam to keep it afloat. A 12 foot plastic kayak will only need one
cubic foot. A 30 foot fiberglass sailing sloop with a diesel engine and
lead keel would need about 150 cubic feet of foam. Actually, very few 30
foot keelboats have positive foam flotation, but it's not out of the question-
especially when you consider all of the air pockets that would exist, as well as
all of the wood interior components that provide some positive flotation.
Q. Do I need to paint or fiberglass over the foam?
A. You probably should. Urethane will
absorb a small amount of water, because some of the the cells are open (95%+ are
closed, though). Painting or glassing will seal the foam and prevent any
water absorption, but it really shouldn't be necessary unless the foam is
constantly immersed in water, such as in a boat with bilges that are always
wet. The foam is not UV resistant, so it should be painted if exposed to
sunlight.
Q. Is the urethane foam resistant to fuel, oil, and solvents?
A. Mostly yes- It is resistant to splashes of gasoline and diesel fuel, although
it will absorb a small amount because no pourable foam can be guaranteed to be
100% closed cell. A strong solvent such as acetone or toluene would
eventually break the foam down, but it would take a long time.
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