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  #1  
Old 03-16-2011
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Soundproofing PS Engine Compartment

About to tackle this project. Has anyone done it?

The front is easy, the top, sides and back not so much.

I am curious if anyone has done this how they solved the following problems.

- Did you attach the soundproofing to the underside of the cockpit floor hatch or build a floating layer below it?
- How did you handle the aft side of the engine?
- Any way to do the sides with all the items attached there?

I am thinking about just doing the front and top. For the top I would do from where it meets the front to the access hatch, then also the bottom of the access hatch. Maybe improvise a floating panel behind the engine.

I suspect even if I just did the plywood front it would help a great deal. Seems like most of the noise comes through that.

Anyone have factory soundproofing? Would love to see how they do it.

Appreciate any thoughts. Would love to see pictures.
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Old 03-17-2011
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Quote:
Originally Posted by RainDog View Post
About to tackle this project. Has anyone done it?

The front is easy, the top, sides and back not so much.

I am curious if anyone has done this how they solved the following problems.

- Did you attach the soundproofing to the underside of the cockpit floor hatch or build a floating layer below it?
- How did you handle the aft side of the engine?
- Any way to do the sides with all the items attached there?

I am thinking about just doing the front and top. For the top I would do from where it meets the front to the access hatch, then also the bottom of the access hatch. Maybe improvise a floating panel behind the engine.

I suspect even if I just did the plywood front it would help a great deal. Seems like most of the noise comes through that.

Anyone have factory soundproofing? Would love to see how they do it.

Appreciate any thoughts. Would love to see pictures.
RD:

Our came w/factory sound proofing on the front panel. We added SPM tiles from Sailor's Solutions to the underside of the cockpit access panel as well as aft under the area around the binnacle. The SPM tiles are superior to what the factory put in, but never got around to swapping it out. The noise reduction was noticeable, but not dramatic.

Sorry - no pics.
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Old 03-17-2011
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Raindog, the thing about soundproofing is that you always can use more--until your budget runs out.

Most of the makers have installation guides available. The most effective materials seem to be layered, i.e. a foam that does not transmit noise, which is applied by adhesives or hangers to solid surfaces (like the cockpit over the engine) and special nails with very wide heads to attach to plywood sides.

The foam is usually topped by a dense lead-and-vinyl layer, or layers, in the theory that the dense lead will absorb vibrational energy, and if that is loosely coupled to the foam layer, the vibration is trapped and transformed into heat in the lead, and not passed on as sound.

The rear of the engine is a problem, most engine compartments are open to the rear. The best you can do is probably to put some transverse mounts across and put up a sheet of dense (dense & thick) plywood, then attach soundproofing in the front of it to absorb whatever you can before it bounces around. Every gap is a noise leak, but you still will have gaps, and you still need to ventilate the engine compartment.

Soundproofing is always a compromise. You might want to take a couple of digipix, even cell phone pix, and email them to a couple of vendors, asking for their suggestions. Most of them are quite anxious to help people "do it right" because it is so easy to do it wrong, and then people blame the products.

BTW, if your engine mounts are flexible mounts, and they are over 5 years old? The rubber stiffens and transmits more noise and vibration to the hull. Yes, engine mounts really are "supposed to be" replaced every 5 years or so. (Ya sure.)
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Old 03-26-2011
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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.

Bill Murdoch
1988 PSC 34
Irish Eyes
Warderick Wells Cay, Bahamas
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Old 03-28-2011
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Bill is absolutely right about the impact of holes" on soundproofing. BUT, sound does not go around corners so you can have a 6" X 6" hole (I'm exaggerating here) for air intake and as long as you make the air (and noise) go around a baffle (think dorade box) of soundproofing material, then the noise is remarkably attenuated. I used to make enclosures for air compressors used in weaving studios.

The other thing is that a very famous orthopedic surgeon once told me that vibration was absorbed not by the soft squishy stuff we use but rather by the interface of soft and hard materials. So, the thickness of soft material (e.g. foam) is less important, according to him, than the number of layers of hard and soft. This guy was bone-headedly wrong about many things outside his area of expertise so I'll leave it to you to determine if this was within or outside his area of expertise.

Jay

PSC 37, Kenlanu -- getting up to 33F today!
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