Engine Room Acoustical Insulation

[pacificsailors]

We had to remove some of the bulkheads in the engine room on our Monk 36 to get to the fuel tanks which we are in the process of replacing. When we replace the bulkheads we want to add some sort of sound dampening material. It can't be very thick so the floorboards can still be removed. We are considering a product like FatMat. Has anyone done this? What other options are there? Thanks!

 

[Comodave]

I like Soundown products. Not cheap but are very effective. Just a happy customer.

 

[pacificsailors]

Thanks. Soundown just seems to have 1- or 2-inch thick insulation. We really don't have the space for that. Curious how you attached it to our walls though?

 

[Comodave]

You can use sheet metal screws with fender washers if you have a substrate to screw into. If you can’t screw into the substrate then they have glue on pins that you stick through the insulation and put a fender washer and then a push on cap to hold it.

 

[Keysdisease]

It can't be very thick so the floorboards can still be removed.

This sounds like a clearance problem, with traditional vinyl/foam insulation you can transition thicker product to make them thinner by carving the decoupler off the back of a vinyl foam insulation.

This means that you could use 2" product on the bulkhead and make it 1" thick for the bottom 6" for floorboard clearance. Same for 1" transitioning to 1/2", if I understand your issue properly.

I looked up FatMat and it looks similar to DynaMat. This is primarily an automotive damping product for vibration damping. It will have some airborne noise reduction properties, but that's not the primary use for this product.

Another option would be to use Mass Loaded Vinyl (MLV) which is either 1lbsqft (1/8") or 2lbsqft (1/4"). This is the basic lead replacement all purpose noise barrier. Inexpensive, durable, resistant to chemicals, doesn't care about getting wet. This is the same barrier as in the typical vinyl/foam insulation, just without the foam. The foam on either side of the vinyl enhances the performance of the vinyl noise barrier. Won't work as well as vinyl/foam, but boats are full of compromise.

In noise control, more is better, and as close to 100% coverage is important.

 

[woodsea]

The goal of covering the sides of tanks in an engine space is to reduce reflected noise. A hard surface reflects noise, a soft surface absorbs. Many builders used ceiling tiles to cover hard surfaces. Cheap, fire retardant and reasonably effective absorbing noise. Probably best to assemble some sort of frame work rather than glueing directly to the tanks.

 

[Capecodder]

This is what I’ve used.
https://soundown.com/marine/

 

[Mako]

The goal of covering the sides of tanks in an engine space is to reduce reflected noise. A hard surface reflects noise, a soft surface absorbs. Many builders used ceiling tiles to cover hard surfaces. Cheap, fire retardant and reasonably effective absorbing noise. Probably best to assemble some sort of frame work rather than glueing directly to the tanks.

Exactly right. A very effective application would be perforated panels on those tanks (like those cheap perforated tiles), sitting on a space frame of (example) 1", and fill the space behind with rock wool.

This reduces reflected noise but is not good to be used as a sound insulator to keep sound from the engine room entering the salon. For that you need mass loaded vinyl, lead-foam panels, Sundown, etc.