View Single Post
Old 10-21-2020, 07:43 AM   #4
Bkay
Guru
 
Bkay's Avatar
 
City: Reedville, VA
Vessel Name: Wingspan
Vessel Model: Aluminum Catamaran
Join Date: Aug 2018
Posts: 580
I think chasing down sources of noise is a never ending, but worthwhile, task. Everything you that helps create modest improvement increases enjoyment.

As you know, finding and closing all the air leaks is step 1. I also had good luck with Sounddown products. If you can only put them on the engine room overhead, that should create some modest improvement. I also believe any exposed area that you can add insulation will help capture airborne noise even if you can't retrofit 100% of the engine room. I guess with steel you don't want to use the noise absorbing paint, right?

I also used mass loaded vinyl under the cabin flooring. Weight was an issue so I went with 1 pound PSF MLV. I'm sure it helped but I can't quantify how much. I also used a flooring that absorbed airborne noise and I have a number of rugs down. I believe any soft surfaces absorb airborne cabin noise.

Trying to isolate engine from the hull if it's hard mounted is a good idea. But there are some risks that you might set up sympathetic (or is it harmonic?) vibration that at certain RPM's makes it worse. I have hard mounts on my aluminum hull and that seems to work better that the soft mounts on my last (wooden) boat. I think I'm at 74db at WOT (2300 RPM) and my last boat was 85db at fast cruise of 2800 RPM. It's only 11db but a HUGE difference.

Good luck.
Bkay is offline   Reply With Quote