[C320-list] Engine compartment sound proofing - Some preliminary results
clburti at gmail.com
clburti at gmail.com
Tue Jun 24 19:17:35 PDT 2014
Ken,
This would make a good article for Mainsheet if you approve. A couple of hi-res photos and a bit more detail about the process is all we need.
From: Ken Danko
Sent: Tuesday, June 24, 2014 8:30 PM
To: C320-List at Catalina320.com
Hi all:
I have wanted to install engine soundproofing for years and the recent
discussion here motivated me to finally make the move. I took Jeff's
suggestion and this morning I went to West Marine and bought their kit:
$155 including our very high sales tax. I was disappointed to find that
there wasn't enough material to fit both of the covers. There was enough
for the front cover and probably the top of the rear cover.
Before I started the job I decided to measure the sound levels with my
iPhone. So here are the details on that. I have an iPhone 4s running the
latest operating system. The free app I used is called dB Volume; I
didn't change any of the default settings. I set the iPhone on the outer
curved edge of the dinning table, face up , with a 1/2 inch overhang,
and with the microphone facing the engine. I first measured the
background noise without the engine running: 42 dB. I then started the
engine and ran it at 1500 RPM (admittedly an arbitrary speed). With the
existing engine cover on and the steps down and the companionway open I
got a reading of 71 dB. Then I took the front cover off just to see what
the sound level would be: 80dB.
I spent a couple of hours meticulously cutting and installing the
soundproofing material on the inside of the front cover. I made sure
that there were no gaps and I taped all the ends. I had to cut out a
half-moon shape (1/4 inch deep) in the middle to accommodate the
flywheel. I taped over this area with the metal tape provided in the
kit. I have to say, it looks great.
I know that I need to do the back cover to experience the full effect
but I wanted to see how much sound reduction I would get from my day's
work so I started up the engine and set it at 1500 RPM again. I was
delighted to hear the engine, which, to my untrained ears, sounded
quieter both in the cockpit and below deck. But then I set about
measuring the resulting sound level with my iPhone. Guess what? 71 dB!!!
So much for my own judgement about sound! I turned the engine off and
re-checked the background noise level, it was still 42 dB.
I realize that I am going to have to buy some more material to do the
back cover and I am exploring alternatives to West Marine. I will report
back to the group when I finish the project. But I have to say, I'm
pretty disappointed so far. It was a gorgeous day here and as I drove
home I looked out over the bay and thought about how I could have spend
the day sailing instead of installing sound proofing that did nothing to
reduce the sound levels.
Ken Danko
"Grace"
San Francisco
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