Sound proofing the engine room.

[Shoalcove]

I want to clean up the engine compartment this year to better organize things and to reduce the noise. I've looked at both the paint from Silent Running and the foam from Soundown. It seems to me that you would gain best advantage from using both products(assuming they actually work). Has anyone tried this or had experience with either product? Also a very practical matter- how do you attach things like wires, hoses and filters after you have soundproofed? I'm thinking of raised plywood pads but would like to hear your ideas.
Thanks a ton,
David

[Chris Campbell]

Hi David,

Weatherbird had a foam/lead/foam/foil sandwich of some type - not sure who made it since it came with the boat, but it worked quite well. Attaching things to the walls was done exactly as you've suggested, with solid pieces glued into holes cut in the insulation. I think keeping the size of the solid bits down helps with the sound dampening, since a solid block will transfer more noise than the insulation, though. Weatherbird had a small block for each bolt, rather than a large block for a given fixture (fuel filters, fuel pumps, and fire suppression).

That Silent Running paint-on stuff looks interesting! I'll be curious to hear if anyone's had experience with it. I won't have room for much on Luna due to the tight quarters the engine is mounted in (under the forward dinette settee) - that might be a good solution for me. Thanks!

Cheers,

Chris

[Homer]

After repowering last year I lined the underside of the teak and holly sole (which is above the new Volvo Penta in the bilge) with 1 1/2" Sound-Stop panel from Defender. The stuff is multi-layered and is rather heavy. It goes in easily and really does a good job of both sound and thermal insulation. Most pleased.

[Quetzalsailor]

Soundproofing means: airtight, discontinuous, heavy, floppy, absorptive and assymetrical.

Airtight: enclosure(s).
Discontinuous structure: gaskets, engine mounts, flexible shaft couplings, nothing touching the noise source.
Heavy: easier on buildings than on boats, ships or planes (Lead foam sheets as sold by West Marine)
Floppy: soft enough to not transmit sound energy, follows on with the discontinuous, above.
Absorptive: the sound batts, acoustic tile etc.
Assymetrical: usually talking here about adjacent wall surfaces or glass windows; make the layers of enclosure not the same so that they simply do not want to vibrate sympathetically or by being 'coupled' by the intervening air.

For a small boat, it's pretty tough to do well:

Airtight is tough, particularly if the engine needs air to run and to cool, and the enclosure is inconvenient at best and tough to retrofit. Gasket what you can.
Discontinuous: engine mounts, rubber hoses for exhaust.
Heavy: not likely beyond what you can do with plywood casework and doors.
Floppy: not likely, either
Absorptive: use the foam sheets
Assymetrical: not likely; there will not be doubled enclosure components.

(I've designed enough theatres and performance spaces to have some experience with the problem.)

[Homer]

My goal was not to soundproof but to merely make the saloon quieter, which was easily achieved. The lead/foam prevented the sole from acting like what I would describe as a drum. Sound proof would have required all sorts of difficult engineering including venting and such. That was way out of the question. I am happy with simply achieving quieter.

[Figment]

http://plasticclassicforum.com/viewtopi ... lit=silent
The silent running thread.

A few years down the road, yeah I'll say it's effective. The foam/foil sandwich stuff is more so, but in an application where that stuff is impractical, I'd use the Silent Running again.

[Shoalcove]

What about using the Silent Running and covering it with the Soundown? Is that more effective or just more expensive? I hope to haul the old engine next week and will have the area at my disposal.
Thanks,
David

[Figment]

I think the time and effort would be better spent on doing a Very Good Job with the soundown.

[Shoalcove]

Thanks, I appreciate the opinion. I'll put the money into the Soundown.
David