Replacing sound depressing in engine compartment

[P27]

I need to replace the sound depressing it’s falling off and decomposing leaving a black residue from the foam I have not decided to go with the precut squares that are adhesive backed or to purchase the kits with spray on adhesive. My thought is the precut adhesive backed squares would be easier to install but with a lot more seams and how will the adhesive hold compared to spraying the adhesive from a can I think the sprayed method would be a better approach but may take a bit more work and time looking for advise.

[redsky49]

In the commercial trades, the use of stick pins is predominant for similar applications. In conjunction with spray adhesive, pretty bombproof.

[P27]

I do believe the stick pins are in the kit I was looking at I am somewhat cautious about peel and stick do to the fact that almost all glued don’t do well with heat

[tkeithlu]

I used narrow strips of thin plywood tacked over the panels every six inches or so to make sure that they didn't fall in the works. It's held up for 9 years OK.

[redsky49]

Originally Posted by P27

I do believe the stick pins are in the kit I was looking at I am somewhat cautious about peel and stick do to the fact that almost all glued don’t do well with heat

Epoxy the stick pins, spacing based on weight of insulation. You won't need many. For sound dampening choose your materials carefully. Many, if not most vendors, make claims but provide zero documentation. There are organizations that establish testing criteria. In the US for example, ASTM. Look for performance across multiple octaves.

What frequencies are you trying to address. Most products work best at only certain frequencies. Will you require a cleanable surface? Foams are probably not the answer then. Lead works well at low frequencies, for example.

Are you trying to dampen the sound (absorbers) or contain it (reflecting) or a combination of both? Can you seal cracks and gaps? What about door gaskets?

Do you require nonflammable materials? Look for both a smoke and burn rating (somewhere less than 25/50). Lower is better.

To compare apples to apples look for a chart like this:

[P27]

Originally Posted by redsky49

Epoxy the stick pins, spacing based on weight of insulation. You won't need many. For sound dampening choose your materials carefully. Many, if not most vendors, make claims but provide zero documentation. There are organizations that establish testing criteria. In the US for example, ASTM. Look for performance across multiple octaves.

What frequencies are you trying to address. Most products work best at only certain frequencies. Will you require a cleanable surface? Foams are probably not the answer then. Lead works well at low frequencies, for example.

Are you trying to dampen the sound (absorbers) or contain it (reflecting) or a combination of both? Can you seal cracks and gaps? What about door gaskets?

Do you require nonflammable materials? Look for both a smoke and burn rating (somewhere less than 25/50). Lower is better.

To compare apples to apples look for a chart like this:

Thanks I will look into it

[Mahayana]

In 2013 we ripped out the deteriorating factory installed foam and replaced it with rolls of foil backed sandwich of foam with a plastic layer in the center. Spray on adhesive has worked like a charm. We motor whenever necessary, sometimes for great distances when going to the destination means a beat. This solution has held up well.

First shot is of the backside of companionway steps. Sorry, can’t flip the second.

[Sunsetrider]

I replaced the OEM insulation in the engine box to deaden the sound of the VP diesel. I wants with a roll of soundown sticky-back plus the pin things shown above. Works well and stays up. Great improvement in noise level. Check out soundown website. Quality product.

[Sunsetrider]

Went with not wants with!!

[boatbroke]

Hi P27,

Spray adhesive works really well (nice work Mahayana!). Just try ensure the surfaces are all nice and clean and the recommended dry times/temperature are followed, solvent entrapment can cause the glue to not cure/release.

I usually try put some pan head self tapping screws with a large wash around as well as a bit of a fail safe. Always use the tape for seams and edges as the most often peel here.

Better to spend an extra 10 minutes for peace of mind.

Good luck!

[CarinaPDX]

I used adhesive combined with pan head screws and fender washers - still going well after nearly 40 years. But the foam itself isn't so it is time to replace. I used a 1" foam/heavy rubber/1/4" foam sandwich with an aluminized mylar (?) top cover - I would not use lead instead of the heavy rubber. All edges and seams were sealed with a matching silver tape which helps hold the foam in place and prevents moisture and diesel from penetrating the foam. The old Sabb engine was pretty noisy and this made a big difference.

Greg

[Hudson Force]

When looking at material options for this application consider performance automotive firewall padding. I used this and found it very effective as well as inexpensive.

[Bycrick]

The least of your longevity worries will be the adhesive. I put sound-barrier foam in the engine spaces in 1998. The fancy stuff with the lead-filled plastic layer. Since then, the plastic foam has deteriorated and most of it that was not held on mechanically has fallen off. The worst problem with replacing it has been getting off the old adhesive and foam remnants which sticks to the bulkheads like a poor relative.

[P27]

Originally Posted by Hudson Force

When looking at material options for this application consider performance automotive firewall padding. I used this and found it very effective as well as inexpensive.

In searching for material to use I took a look at rock wool I would really consider it if came in sheet form it is waterproof fireproof doesn’t mold evidently doesn’t have foil covering like foam. It is an insulation so don’t know if it would trap excessive amount of heat around engine

[DeepFrz]

Rock Wool is a pretty poor sound insulation compared to the purpose made closed cell and lead/heavy plastic insulation.