Join Date: Jan 2007
Location: The house is in Kingsport, TN. Boats are on Watauga Lake and in New Bern, NC
Thanked 51 Times in 46 Posts
Rep Power: 11
When we bought Irish Eyes there was soundproofing on all the vertical surfaces of the engine compartment, under the cockpit aft of the removable part, and under the removable part of the cockpit. There was no soundproofing under the large hinged engine access door below the companionway. The installation has not been perfect by any means.
In order to be effective the soundproofing must be continuous with no holes. Think of a shoe box sized container made of soundproofing material enclosing a radio with its volume turned up. With the box completely sealed it is relatively silent. Cut a 2” hole in the top of the box and it will be almost as loud as with no box at all even though the radio is 95% surrounded. Well, there are lots of holes in the engine compartment. Control cables and wires come and go. The shaft area aft of the engine is open to the bilge and hence to the entire boat. The area below the companionway is open to the engine space. You certainly could not fill the engine compartment with water, shake the boat, and expect no water to leak out. Expect the sound to leak out as well. Look at the full-enclosure boxes generator manufacturers put around their generator sets. Even they have a problem figuring out how to get air to the engine after they are through.
Many things are mounted on the surfaces of the engine compartment. The list is almost endless; icebox pump, alternator regulator, sea water strainer, Racor filter, electric fuel pump, Halon fire extinguisher, engine drive refrigeration controls, refrigeration salt water condenser, electrical wiring, isolation diodes, amperage shunts, hoses galore… The list just goes on and on. Now here is the question, should the insulation go under them or should it be cut away where they are mounted? If it is cut away, should spacers be installed in the cut out areas to raise the mounted items up to the new surface? Crushing the foam and foil under the mounted items does nothing to make their mounting more secure. Cutting the foam and foil away around them produces more holes in the soundproofing. In my case the soundproofing goes under everything. Everything wobbles, and the wobbling is destroying the soundproofing. I don’t think crushed soundproofing is effective anyway.
The open cell foam is a fire hazard. Even if it is treated to be non-flammable it can still soak up oil – lubricating oil or diesel fuel. While you could safely throw matches at a pool of either liquid in a pan, they would easily catch fire if soaked up in a rag. In an attempt to protect the foam from becoming an oil filled wick, there is a mylar/foil layer on its surface. There are two problems here: first, the adhesive between the mylar/foil and the foam is failing on my boat allowing the mylar/foil to separate from the foam, and second, the unprotected edges are, well, unprotected. The edges eventually become a grungy greasy mess, especially at the bottom of the vertical part near the engine dip stick and fuel filter where years of splatters and drips have accumulated and soaked into the foam.
My soundproofing seems to be of two different sorts. One kind has fallen apart. You know how polyurethane foam sometimes hardens and turns to dust? The foam in about half of my soundproofing has done that. It is a colossal mess to clean up with black foam powder settling everywhere and leaving the surface mylar/foil and interior vinyl/lead layers flapping about.
The glue that was used to install the soundproofing seems sufficient for the vertical surfaces. It was not adequate for the overhead surfaces. To reattach the soundproofing under the removable cockpit floor the previous owner had added six screws with washers under their heads. That meant the soundproofing draped down in the spaces between the screws leaving a gap between the soundproofing and the panel that was open at the edges allowing the noise to just go around the soundproofing. After trying several types of glue that did not work, I wrapped lower surface of the soundproofing with aluminum expanded metal lathing and screwed the whole lot in place with king sized washers of 3” diameter aluminum disks. That seems to do adequate job of keeping the soundproofing tightly against the panel. Actually, I copied the method used by a generator manufacturer for all of his soundproofing. The soundproofing under the aft part of the cockpit was of the depolymerizing sort; it fell down and disintegrated soon after we bought the boat. The black foam dust made a mud-like mess in the bilge under the packing gland.
I wish I knew a way around all the problems.
Oh, by the way, the soundproofing foam under the removable part of the cockpit floor makes it noticeably cooler than the fixed part behind it which now has no foam. It is much more pleasant to stand on a cool deck in the summer while motoring. I need to replace the missing foam. My bare feet will be happier.
1988 PSC 34
Warderick Wells Cay, Bahamas