A Letter From Paul:
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 was very
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 and
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 point.
Regards, Paul Thompson