Having now had La Chica fully foam sprayed (average thickness
40mm) from cabin sole port to cabin sole starboard everywhere in
fact except for the bilge, I would like to make some comments.
Before you start, mask everything you do not want foam on. Use
plastic on large areas and the blue masking tape to stick it on. Use
masking tape on it's own in the small or narrow areas. Don't use the
white masking tape or as our foam man suggest the brown parcel tape,
both are hard to get off as they stick too well and breakup when you
try to pull the stuff off.
As Brent has suggested. Forget your excitement and don't let the
foam man go away before you have carefully checked every square
millimetre of the foamed area. You will find holidays, especially
where shadows formed while spraying. Look closely next to frames and
stringers. That is where you are most likely to find the holidays.
Flat surfaces seem to cause little problem but stick a stiff piece
of wire (mark the depth you want with a piece of tape) through the
foam to check the depths at random intervals.
Fortunately, if you have built one of Brent's boats, the shadow
problem will be minimal as there are few to no transversals but
check those stringers.
Clean up! The Elephant in the room. It is very hard to control the
exact depth of the foam, resulting in a sometimes very uneven
surface. My guy did a fairly good job on the hull sides but overhead
uneven and lots of fairing had to be done.
After trying all the methods described in previous posts I settled
on one. A 4inch (El Cheapo Chinese NZ$15.00) angle grinder with one
of those 3M brillo pad type disks that they use for removing paint
rust from steel. This was very fast and accurate but it makes a hell
of a mess. You need a Tyvek disposable suit and a full face
respirator (covers eyes as well, I used the 3M product). I tried at
first with a half mast and goggles but the dust kept on getting into
the goggles and then into my eyes. With the grinder, it took one
full day (8.5 hours) to fair the hull and another day to clean up.
For cleaning up you need a brush with firm bristles and a good
vacuum cleaner. Brush the foam first, then vacuum. If I had stuck to
the knife system, I would still be there.
After clean up, I touched up with a knife, a surefrom tool (looks
like a plane with a cheese grater attached) and a Japanese saw. I
did not want to use the grinder again as it would have meant another
major clean up. So try and get everything as right as possible
before cleaning up fully. You will need to clean up in some spots
while grinding, so as to see what is happening. You also need a
static free cloth to wipe your visor every now and again as the dust
sticks to everything.
Lastly, I borrowed an airless spray unit from a friend and
sprayed latex/acrylic water based paint onto the foam. You need to
do this as the dust does not stop until you do it. It also seals the
surface and gives it a firmish crust. You use lots of paint, I think
I used around 25 Liters (on a 32Ft heavy displacement double-ender).
Fortunately the paint was free, given to me by a friend who is
caretaker for a large school. He was quite please to get rid of all
the partly emptied cans in his paint locker.
Lastly, It cost me NZ$1 200.00. This is cheaper that buying a kit
and doing it your self (in NZ the kits would have cost around
NZ$1700 and then you must still do the work). It was also both
cheaper and much quicker than buying sheet foam and cutting and
pressing it in.
Hope the above helps other who will need to do this job at some
Regards, Paul Thompson