David, On Cat’s Paw, I installed special sound insulation to quiet the noise of our 30 hp Perkins diesel. Decided to make noise measurements in the cockpit, the cabin just forward of the engine, and all the way forward in the V-berth (using a cheap dB meter app on the iPhone). 2 inch thick sound foam with a special sound-adsorbing backing on the wooden engine housing in the cabin (sides, front and top) and on the sides of the cockpit lockers. Just too hard to get to the underside of the cockpit floor. It made only a small difference in sound level - maybe a dB or two (I think 3 dB is a factor of 2). When talking to a professional sound person when we separated a large room with wooden sliding doors in our rental apartment downstairs with special sound-absorbing materials, professionally installed, I was told that even a small gap in the insulation would basically make the whole thing pretty ineffective. 90 percent coverage with insulation would let much more than 10 percent of the sound through. That job really worked - they left no crack uncovered and it really blocks the sound. So my guess is that unless every exit point surrounding the engine were insulated, it would make little difference (and I left the whole cockpit floor uninsulated). Also the engine can transmit sound by vibration through the engine mounts - perhaps new ones would help - have not tried that. But as it stands, pretty disappointing.
See you at the Newport rendezvous in September - I can show you what I did. Eric Cat's Paw C&C 35 Mk II Mattapoisett, MA > From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of David via > CnC-List > Sent: August 28, 2014 6:22 PM > To: CNC CNC > Subject: Re: Stus-List Engine Sound Insulation > > Well I heard from one about the not-so-great results from installing engine > sound insulation...anybody else want to chime in with an opinion about > whether it is worth it? > > David F. Risch
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