Engine Room Insulation (Long Question)

[Zach]

Hi guys,

I'm looking for some ideas for the engine room refit of a 1942 83 foot Coast Guard cutter. It was converted to a motor yacht, with about 1500 mile range. Its been through the panama canal, and was a charter boat down in the Tortuga's for awhile in the 90's. Now its getting refit, and my dad has called me in to help out with the logistics.

It is powered by two Cummins diesels, NH-855's. One 8kw Northern Lights generator, and a 30kw Chinese generator. They all have wet exhausts. The noise is incredible, requiring ear muffs when firing everything up, the heat is also incredible.

The call for insulation is two fold, the first is the bulkhead in front of the engines is the rear wall of the aft cabin. It needs to be acoustically insulated so the noise of the 8kw generator is not heard when anchored out for the night. The house is directly above the engine room, and has a large hatch for access. The boat had Masonite panels in between the deck beams to insulate the noise. Standing at the kitchen sink was about like sitting at an intersection with a diesel truck beside you.

What materials should we be looking at for the bulkhead and between deck beams? Looking for both sound and heat insulation.


The exhaust systems on both engines are non-insulated. (Hazardous working conditions right now!)


Generators: The 30kw has header wrap on the cast iron manifold, and a heavy wall rubber hose going to the water lift. (Down stream from the water injection.) The Northern Lights has seen some engineering and is quiet enough not to worry about.

The other idea I am pursuing, is to route the main engine air intakes to outdoors with rubber bellows.

Thanks for your thoughts and ideas... this is a topic that we have no real idea how to proceed!

[David M]

I have never been on a boat that size which has no generator noise when the genny is up and going. Northern Lights does offer cases which fit right over the genset itself..but you will still have some exhaust noise. These cases reduce the noise but do not completely eliminate the noise.

The most effective way of cooling the engine room is through forced draft ventilation that you run whenever the mains are running. There is no such thing as quiet forced draft ventilators of that size.

What I have seen on a few workboats of this size is perforated sheet aluminum a few inches off the bulkheads with fiberglass stuffed between the sheet aluminum and the bulkhead. With wood bulkheads this would be relatively easy and inexpensive to do...no welding necessary. There is that foam material with a mylar layer on one side and thicker rubber on the other designed to sound insulate small engine rooms but this stuff is very expensive.

Make sure you mains and your genny have adequate newer mounts...otherwise the vibration transfers right through the hull.

I would hire a marine surveyor who specialized in boats of your size to come aboard and give you some ideas of what may work, and what is safe. Obviously, you want to use only fire proof or fire retardant materials in the engine room.

[jjtctaylor]

My reco is to contact an expert. I work for a large company with significant noise issues. We work thru IES 2000. http://ies2000atlanta.com/ They will review your needs and provide a solution recommendation, naturally using their materials, etc. But they know their stuff. You will need a high temp insulation then acoustic pipe lagging. You will need to create vibration mounts for motors, and exhaust. They can help with those needs. Then they will create custom sound enclosure and/or removable insulation blankets around the blowers, engines, motors and all else of high noise levels. Then they will provide proper specialty sound materials for walls and ceilings. It is not overly expensive and they will do the analysis for free.

Lastly sound dampening devices convert noise into heat. That is why the materials are specialized. But you will also need to consider cooling plans for engines and motors that are enclosed. The radiant heat is trapped and so is the noise energy. The blankets are heavy, but really do work. Expect not less than 10 db reduction and can be much higher if you can insulate the equipment from the surrounding frame via isolation mounts. The walls, floor, and ceiling are resonating so have to stop that too. Takes a real package to get decent results. Not only will you be happy with the outcome, but it will make work in there reasonably pleasant.

Just a suggestion. I have no affiliation with the company except as a contracted firm on an as-needed basis. Good Luck !

[beetle]

I have used EAR composites for acoustic insulation on my boat, which is a much smaller boat than you are dealing with.

E-A-R Specialty Composites -- noise, vibration, shock, damping, cushioning, sound, control

They seem to know their stuff and it might be worth having a chat with them to find out how they would approach the problem.

For thermal insulation (e.g., wrapping around hot exhausts) I have used glass-filled thermal blankets, and 1/4" fiberglass wrap for tight bends.

Thermal Insulation by BGF Industries, Inc.

- beetle

[Zach]

Thanks guys.

I'll give those folks a call and start sourcing materials.

[nwboater]

Zach, not to take away your thunder, but does anyone have experience using an acoustic sound blanket to quiet down the main? Of couse, I would vent for air-intake and stay away from belts or pulleys.
Richard

[David M]

Just for gensets. I don't see why you could not make a noise cover for your propulsion engine. You would of course want to make sure it has adequate ventilation and be relatively hassle free to remove.

[CarlF]

The challenge with big engines is that a lot of the noise is low frequency. This is much harder to stop than higher frequency sound. A lot of the soundproofing advice deals with normal speech frequencies (for between apartments)

I would take a look at the Green Glue site. This relatively new (and very cost effective) approach is being rapidly adopted in housing over the traditional Mass Loaded Vinyl (MLV) that you find in the typical foam sandwich in boat engine rooms. Green Glue is an elastic goop that comes in a big caulking tube. You put it between two layers of heavy material like plywood, sheetrock,etc. The technical library on their site compares Green Glue to other methods. Even if you don't use Green Glue, it explains a lot about sound control strategy. You'll even learn about the dreaded "triple leaf effect" (as if we don't have enough to dread on our boats ). Haven't tried it myself but will the next time I have a soundproofing project.

Green Glue is your soundproofing and noise reduction material

Carl

[James S]

Off the thread a bit but may be relevant the the level of noise,,,,,Are you sure that water lift shown in the picture is plumbed right..the outlet on the top should have a pick-up tube going down to with-in an inch or so of the bottom.
I'm surprised that the inlet is on the bottom.

[klem]

CarlF makes a good point about what frequency sounds are a problem with larger engines. This is an old thread so I suspect the work has already been completed. One desireable but difficult thing to do is to soft mount the engine so that it does not transmit vibrations well to the entire hull. Evolution Drives do this but I don't know whether they make something large enough to go on an 855. Sound insulation is very important but it will deal with the higher frequency stuff so a combination of both systems is ideal.

The other way to approach this is to go with newer common rail engines which are much quieter to begin with but that is a much larger and more expensive project.

[Mirar]

Hi Zach, I am currently building a large alloy sailboat and am addressing the issues of engine room insulation. To comply to Canadian Coastguard requirements, I am using mineral wool blankets on all the bulkheads and other surfaces,held on with stick on pins. This is made by Roxul and starts with heavy batts placed in between all framing with a softer "blanket" overlayed ,with a mylar foil surface for vapour barrier. Totally fireproof , doesn't absorb water, and a terrific sound barrier. Look on Roxul's web site for info. Even if I wasn't using the marine board version, I would use the regular household Roxul that you can buy at Home Depot as it is far superior to the pink stuff you see in houses.There are some excellent ceramic blanket products made in the US as well with fire ratings to over 2600 degrees F. Many of these products are available in pipewrap configurations as well. google marine insulation/exhaust blankets/pipe insulation for sources.
Greg

[Chief Engineer]

Before you go into all the expense of insulation...check out the price of a smaller genset.....

On the vessel in my avatar we have two Perkins Gensets....being an ex-RN vessel we are used to the sound.

I have seen "lead curtains" hung around gensets on some mega-yachts.

1942? There may be a lot of Hazardous insulation in there now....proper removal would be very expensive......

[gettinthere]

Soundown, Sounddown, Sundown
Silent Running - high performance sound and vibration dampening coating for marine vessels

[Shoalcove]

Hi Mirar,
That sounds like an interesting alternative. Did you use their sound insulating batts?What are you using for a mylar barrier and where did you find it? I've looked at the Soundown products but find them very pricey and would like to investigate alternatives before I commit to any particular product.
Best regards,
Shoalcove

[Mirar]

Hi Shoalcove, I went with the full Roxul program, which involves placing the heavy two in. thick batts between the frames, then covering everything with a solid layer made up of 1 1/2 inch blanket that comes with a very heavy layer of mylar foil glued to it. There is a six in. wide foil tape that you use to join the blankets to create a sealed surface, all held to the hull/deck with deadly sharp stick-on or weld-on pins. I purchased these products from Crossroads C&I in Vancouver, B.C. I believe all this was sourced out of Roxul's Edmonton,Alberta plant. For light duty, one could just use the foil blankets.