home made genny sound sheild

[Capt. Tobb]

During my unexpected "vacation" to hurricane hole for Gustav and Ike I realized that I had to do something with genny. She makes Nancy Grace sound like a mouse. I tend to be one of these guys that likes to make stuff, sure you can buy it off the shelf and I bet it would cost less when you figure time, material, beer, ER room bills. Anyway, I want to make a sound sheild for my 15kw Westerbeke. Enter the drawing board and you guys, have any of you guys done this? Here are my thoughts:

1) insulation- I want to use HVAC duct board, I have alot of it free, should be easier to adhere to the outer cover and less mess than mineral wool, and did I meniton that it is free?

2) outer cover- not too sure on this one. I would prefer to use something that will not rust or corrode(go ahead and say no $h!t) FRP? I am afraid it may melt or discolor. I have seen this material used to make signs, it is two thin sheets of metal with 1/8" corrogated plastic between. The metal is covered in vinyl(I think) Any ideas? I plan to use aluminum 90 degree angle for the corners.

3) venting- I dont know it factory shields have sound insulation over the vents and I am assuming that you only need vents on the shock side of her?

Any thoughts??

 

[Boatsb]

The vents are tunnels so the sound is contained. I lined mine with mineral wool and it did a great job killing the noise. I did have a shield but the insulation was gone. The sides are metal and the top is FRP.

 

[Angela]

The Westerbeke sound shield leaves a LOT to be desired. I have one and it's a piece of crap. The rubber latches all failed, melted and broke by the time the genny had just 250 hours on her, and the sound shield was equally as young. If you want to fix and replace them, you'll find that Westerbeke is pretty darn proud of those little rubber pieces that are designed to fail and to keep you coming back for more. I ended up putting SS latches on it to keep it together.

Also, the insulation is crumbling to the point of it being dust. I've had to use aluminum tape all over it just to keep what's left of the insulation in tact.

So, I have to say you are better off making a sound shield of your other option was to buy the Westerbeke sound shield which is a cheap piece of crap for a lot of $$$$. However, if you shop for a new one today, they don't use those rubber latches. I don't know if they improved the rest of the box.

I'd like have a new box myself. I keep eyeing those lead (or whatever it's made of) sheets that drape over a frame. These are much easier to handle when you need to get in there and work on it.

Keep us posted (with photos!) of what you make and how you do it.

 

[Brian Degulis]

The duct board or duct liner is a great sound absorber one of the best. If you want to go a step further you could add a sound blocker under the duct board Mass loaded vinyl is the most popular these days. I see no reason you couldn't make the enclosure out of plywood maybe MDO or HDO to make a nice professional job. I've learned over the years that sound shields shorten the life of hoses and other rubber and plastic components on the gen set. Consider adding a 120V blower (small one) to bring in air I've done this I wire it directly to the gen's output terminal with it's own fuse so it just turns on when the gen fires up it helps a lot.

BTW there is acompany in Tampa FL " Acousti Block" that sells the mass loaded vinyl and other sound proofing products.

Brian

 

[Capt. Tobb]

Thanks for the help.... Brian, I am not familiar with MDO or HDO, also do you think a bathroom fart fan would be ok? It would be out of site.

 

[Fanfare]

Some trips I run my genny a lot. I think you need a continuous duty fan system. My 50MY only came with two passive aft-facing clamshell vents for the generator/battery room. It really got hot down there, not good for hoses or wiring or battery water. I have added one 110v. input fan, one exhaust fan using the original vents. When I still had my Onan I had a third exhaust fan rigged to take the hot cooling air from the windings and sent this outside, as I found this was most of the heat. This also ensured I had negative pressure in the generator room in case of an exhaust leak. I probably should do this with my newer Phasor, but the ducting is different.

 

[Brian Degulis]

Thanks for the help.... Brian, I am not familiar with MDO or HDO, also do you think a bathroom fart fan would be ok? It would be out of site.

MDO is (medium density overlay) it's a plywood with a bonded paper face it's used by sign painters paint's up nice with no grain pattern.

HDO is (high density overlay) it's plywood with a phenolic water proof overlay it's used primarily for re usable concrete forms. It's very smooth and when painted looks like fiberglass.

Both are just an easy way to build a plywood box that doesn't look like a plywood box.

I would use a small maybe 6" squirel cage blower Grainger's got lots to choose from.

Another poster mentioned venting the space itself I did that also by replacing the OEM 32V blower with a 120V slightly larger blower. That goes a long way to reduce the temp in the space between the gen sets and 7 AC compressors there's a lot of heat being generated.

Brian

 

[Roscoe]

When venting machinery spaces, how do you position the vent exhausts to avoid odors drawn into the boat via the 'station wagon effect'?

 

[Fanfare]

On my 50MY the generator room is below the galley, in the forward one-third of the boat. If you look at the photo of the 53MY on the Sams masthead at the top of each page, the galley is where the trapezoid-shaped window at deck level is. It is far enough forward that normal air flow of forward motion prevents exhaust gasses from being a problem. However, my generator exhaust is on the starboard side near water level. I made sure to have the forced air exhaust on this side. Intake is on port side where air is fresher.

Most of the station wagon effect is from the stern main exhausts, exiting at a large almost flat transom. This causes a vortex which can deposit soot and diesel exhaust smell around the back of the boat. It is worse at higher speed, or when there is a following breeze.