Engine soundproofing

bedouin

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16 May 2001
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My engine is fitted in a large, irregular shaped compartment and there is no attempt at soundproofing at all.

The shape of the space is such that it would not be possible to soundproof some of it - realistically all I could achieve would be about 50% of the surface. Is fitting insulation to that going to be worthwhile or does soundproofing need to achieve a high percentage enclosure to provide benefits?

I am assuming I would use a conventional 15-20mm sound proofing panel - I guess the thin vibration damping style won't be any use in that environment
 

Lon nan Gruagach

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I hate to use advertising jingles, but every little counts. When sound deadening is used as opposed to just a baffle, then any you can install will do its bit.
The main trouble with less than total proofing is that human ears are just too darned good. a dynamic range of about 140dB which means that you can hear a single person at 10 feet as clearly as a jet engine at 100 feet. With that amount of auto level availability it is possible to listen through the walls of some of the best soiund proof rooms.
So, dont be disheartened if your boat isnt immediatly silent, you will benefit fomr not having to talk over it so much. As thick as you can fit and afford.
 
D

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On some yachts in larger engine spaces, the engine itself is boxed in separate to the engine space. The plans for my Rival41C has this for the smaller option engine but not for the larger option engine. Perhaps this could be a solution for you as the shape of the box might be easy to install sound proofing. You can also buy noise dampening paint for the likes of GRP drip pans and hull areas where you would not fit sound insulating panels. Obviously cooling and combustion air supply would have to be addressed in a boxed in engine.
 

yotter

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Me Inverkip, boat Kip in winter, Craobh in summer
It is also very important to ensure that there are no holes, any holes will allow the emission of a considerable amount of noise. Some may have noticed how different the engine can sound if an engine space panel, or perhaps the companionway steps (if the provide engine space access) are moved and not secured correctly.
Angus
 

bedouin

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It is also very important to ensure that there are no holes, any holes will allow the emission of a considerable amount of noise. Some may have noticed how different the engine can sound if an engine space panel, or perhaps the companionway steps (if the provide engine space access) are moved and not secured correctly.
Angus
Yes - that is what concerns me as achieving no holes is likely to be very difficult - i will probably have to construct as sort of collapsible box and soundproof that -and I don't know if I have the space
 

pvb

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You can achieve some improvement by lining the panels you can get at with heavy soundproofing; this will help to reduce vibration and noise transfer. It is very important to seal access doors/panels with neoprene foam strip. If the air intake to the engine compartment is in the cockpit, you can reduce airborne noise from it by making a baffle box, with the baffles covered in soft material (I glued foam-back carpet on to the one I made).
 

fisherman

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2 Dec 2005
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Far S. Cornwall
I have considered installing panels with soundproofing on around the engine rather than to the outside walls of the engine room, as there are too many pipes and other fittings. Or maybe to the deckhead between the engine and me. Trouble is, like last Thursday, dirty weather, onshore wind and not far off the shore had to clear the seawater inlet in a hurry and any obstruction would be a problem Halyard Marine are one supplier.
 

ianj99

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I use lead /foam sandwich from noisekiller.co.uk It is self adhesive and works well. I use an off cut lying on top of the engine to cut down on the rattle from the injectors, injection pump and rocker gear

Also consider fitting an airbox to the engine air intake as this is where much of the noise originates. I did some measurements documented on post 40 of this thread which show a 10db reduction which is a major drop.
http://www.ybw.com/forums/showthrea...ith-a-Marine-Power-Chinese-46bhp-diesel/page4

You can block holes with expanding foam, but you either need a bilge blower or to provide some means for the heat to escape. At least with the airbox, you can install it remotely from the engine, or extend its intake via hose to somewhere it can pickup cool air.
Ian
 

Avocet

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I have much the same sort of engine bay - in fact the bottom of it goes right down to the bottom of the keel (long keeler). Absolute pig to insulate. I tried once with that good foam/lead/foam stuff from Halyard (synthetic lead). I think it made a fair difference but not as much as I'd hoped. As years went by, it became waterlogged from various small leaks and rotted some plywood stiffeners which I then had to replace and galls in. I never bothered replacing the sound deadening and the noise didn't get THAT much worse. The only deadening I kept was the stuff under the companionway steps.
 

William_H

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West Australia
Typical sail boats have quarter berths next to the engine and companion way steps that double as engine box or cover. The cockpit floor is above the engine.
So perhaps first priority would be to seal the gap between the quarter berths and the engine. Then seal the step/cover such that the whole aft end of the boat is sealed from the cabin. That will be the time to provide an air inlet to the area, baffled and remote. You may have to provide cooling air in and out also. Again with outlet inlet remote from cockpit. Perhaps transom or cokpit lockers.
As said it may be easier to build a new box just around the engine rather than seal the whole aft end of the boat. The sealing will also reduce diesel smell.
Once sealed you can look at sound proofing material. I would imagine that the cockpit floor/ roof of the engine bay would be a good start.
Then of course there is the question of vibration. If it is a single cylinder engine then no amount of sound proofing will isolate that thmp thump vibration.
Get a 3 cylinder engine is all I can suggest. Or hoist the sails. good luck olewill
 

Bertramdriver

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Oxford
Coming as I do from the "little spend maximum outcome" school of DIY here are some thoughts.
Sound damping paint is just intumescent paint heavily filled with glass micro balls (as in polyester filler) so buy cheap engine paint and glass balls and mix your own for a 50% saving.
Engine noise is a collection of different sound wavelengths. The paint will knock out / absorb much of the high frequency stuff but for the annoying mid frequencies try buying foil insulated Celotex from your builders merchant. It's used in new builds for heat / sound insulation. It's fire rated, non absorbant, cheap and easy to use. The foil helps protect the exposed surface and cuts back the mid range frequencies. And you can paint it if you have to.
Finally the low frequency stuff. The cheapest solution I've found is recycled tyre rubber, sold as sheets and mats for kids playgrounds.
Again it's cheap and indestructible but you will need to paint with intumescent paint. A mat under the engine bed will absorb a lot of the low frequency stuff that attenuates through the hull.
Or you can go and buy the "good stuff" and spend a lot more.
 

Gordonmc

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19 Sep 2001
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Loch Riddon for Summer
I has a similar problem with an old wooden boat with the engine open to the bilges. The engine box was tight to the engine block, so no scope for insulation there.
Noise levels were reduced from annoying to tolerable with an acoustic blanket.
Mine tied over the top and down the sides of the of the rocker box, so easy to remove. The outer layer was flame-proof and there was a lead sheet inside for "formability".
They are available off the shelf for Land Rovers etc. so a Google should turn them up.
 
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