That is what I was going to recommend. Call Gibson, you shold be able to get it rathur inexpensively.

I believe they're taking orders for parts through their website. Click on the parts _link_.

www.gibsonboats.com

www.holidaycruisehouseboats.com

Chapter II - Trying to quiet my genset-I placed a 1.5" thick (4'x10') sheet of A/C ductboard across the rear bulkhead that's common with the engine compartment bulkhead and carefully taped the top and sides but...it did not even reduce the sound pressure level by 1 db. I also used spray glue to stick the 1.5" ductboard to the engine hatches but before I could make a sound measurement they fell off but...it did seem to help attenuate the noise for a few minutes.

Second try-I fabricated a box around the genset using the 1.5" ductboard with the soft side to the engine to absorb the sound. The back of the box (stern side) was partially open to allow the water and exhaust lines to enter and exit. This made a noticeable difference but when I measured the sound pressure there was only a reduction of 2-3 db. I think this took care of the higher frequencies but the low frequencies are still coming through. Once I've decided what works, I'll have a sheet _meta_l enclosure fabricated (4 sides and a top; It's already got a stainless steel bottom tray) that will hold the sound absorbing/ deadening material. I bought a sheet of 'QL Sound Absorbing Panel' made by Volvo Penta and sold at Boater's World that I'll try next. It's a 1.25" thick heavy rubber mat with foil on one side and adhesive on the other.

stay tuned...

You can get a product for A/C supple houses

Is it made to produce on the spot air ducts and insulation / soundproofing.

it in installation on one side and silver foil of the other.

it is 4" x 8" and be car with a knife and glued together to a some silver tap the sell there.

I use it to make air ducts, soundproof gen-sets and to produce these 'flame reseting' convening masks.

it is really cheap.

That make a whole kit with how to make them into ducts.

jack

My other hobby and passion is recording and sound engineering and I could bore you to tears on the subject, but I will try and give you the short version.

High freq sounds are easily destroyed with soundproofing that is open cell in natrue. They just don't have a lot of energy and can get eaten up by the foam. This energy is transformed from sound to heat inside of the foam.

The lower frequecies which are down below 400 Hz and start to sound like rumbles are FULL of energy and take a lot of absorbtion material to control.

Corners tend to be the main culprit as the low freqs tend to propogate there, amplfiy and return back towards the center of the room or compartment in this case. This is called standing waves and in certain areas they will increase in volume and other areas they will cancel each other out.

The morale of the story is to find the 90 degree corners of your compartment and HEAVILY insulate them. Plain ole home insulation fiberglass will give you the absolute best sound dampening for the buck and is very flame retardent.

To give you an idea of how much it takes. In a sound recording studio it can take as much a 2 foot of fiberglass packed into a corner to absorb and control the frequencies of a bass guitar.
tim2039014.7200115741

thanks,

I'm using a/c ductboard for the genset box already...I'll work on insulating the corners to see how that works...I'll try the QL Sound Abosorbing Panel material for the corners.

Just keep in mind that it is total thickness of the material that counts in the corners.

One additional note is that any hole is a leak with sound, just like it would be with water.

Additionally, any vibration from the motor that travels into the hull will not be absorbed by what I described.

Sound reduction(see earlier posting)- First I tried covering the entire back bulkhead with a 1.5" piece of Air Conditioning ductboard with less than 1 db of noise reduction. I've finally made some headway in silencing my genset, here are the fixes and the resulting dbs (sound pressure level); hopefully it will help someone.

79db-no silencing; 78db-ductboard over separating bulkhead; 74db-d'board box around genset (rear open with hoses, etc); 68db-d'board on underside of hatches w/soft side exposed; 64db-stuffed fiberglass batt insulation into rear of d'board box, completely sealing it except for alternator air intake (air is then sucked into engine, out through exhaust).

Finally the genset is quiet enough to live with. Now I need to get more air into the engine compartment. I plan on using a ducted exhaust fan to pull hot air out of the compartment; fresh air will be drawn in through the vents. This will help eliminate the possibility of exhaust gases getting into the cabin and an early onset of death.

joetil -50' Burnscraft