I would like to insulate the factory sheet metal box around my built in Cummins/Onan Generator. I am not finding anything in the RV.Net search or the Camping World site and I would assume that others have already taken on this type of project. Is foil faced, ridged foam best or is there another product that I should consider? I am planning on using upholsters spray glue to hold the new panels in place unless someone has found a better method. JH
I have already covered my metal box with styrofoam but If I had it to do over I would use Dynamat. I used it on the engine cover of my Arctic Cat Prowler and it helped a lot. It's fairly expensive, 12 sq. ft. for around sixty bucks. It's a thin peel & stick soundproofing that stops sound vibration. I got mine at HookedOnTronics.com
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2003 Sierra SP 26'Toy Hauler
1997 F-350, PSD, 4X4, red Crew Cab, long bed.
2007 Arctic Cat Prowler, Arctic Cat 500
I used Dynamat in two areas; under the doghouse/engine compartment and in the genny compartment. Both were inprovements in noise reduction. Bought the Dynamat from Summit racing as a underhood kit.
Peter & Dawn 97 Winnebago Adventurer 37RW 96 Prowler 27X SOLD
IAFF L-792
Onan warns to not put it on the floor of the compartment, because with a gasoline generator, there is a chance that any sound deadening material will absorb spills and such. Everywhere else is free game, provided the genset has enough CFM coming in and out, and the clearances are correct.
I don' have a list of suppliers anymore, but I used to work for a shop that customized vehicles for movie set use. We did upgrades to gen sets in TV news trucks. We used a thick mat that has several layers, one of which was 1/16 inch lead shield. Talk about expensive!
Use a search engine with the words "sound deadening" & "sound reduction". I found those to give me the best results.
I settled for the blue polystyrene board from Dow. Double thick helps cushion sound waves. I don't like glue in a heat environment. I used fasteners to clip the foam to the wall, much like when you take your door panel off? Those annoying little discs with the pointy pins that go one way into the door panels. You can pre-drill some holes and buy them by the box at the auto store. A body shop or online will help you if your auto parts store are loosers lol. But I know they have 3-5 in a box on the "HELP" line now owned be Dorman. I knew a guy that used 2 inch shag carpet from the 70's then pinned foam board over the top.
I want to share two sound ideas here the I incorporated from the movie industry. Their gen sets are so quiet, I used these ideas on my RV. Now people walk by and talk without raising their voices. Some stop and listen and have asked "Is you genny running?" lol I love it....
1. I have built, a long tail pipe... Think of a car with a new muffler, there is very little sound proofing in the engine compartment when you think about it but, none the less the vehicle is quiet. Some of it is the muffler, but some of the quiet is done with the bends in the tail pipe. They have kits you weld in at a muffler shop to add bends to your current pipe. Hot Rod magazines have had articles on this so you can pipe length and bends under your short roadster. 4 to 5 right angle bends will kill 1/2 your noise.
I also added a small fork lift muffler that the truck shop threw out. I've seen many mufflers off of Quads and such that can be used. Just get one with a side inlet and a center-end outlet. Make a bracket to mount the muffler on with the outlet pointed at the sky. I made mine out of bed frames I found in an alley and wood blocks for skids.
I found a coupler that fit my genny's flex pipe. I pull the flex pipe out from under the MH skirt and put it into a bent tube that looks like a square U turn I have bent at a muffler shop. That is 2 right angle turns. Then put the "u-pipe into the muffler on a swing down platform on chains that looks like a tiny jail house bunk. I hang the tail pipe that goes to the roofline on fasteners that are similar to a Pintle.
Near the roof line the pipe takes a 90 degree turn for 18 inches and then back up to the sky. 2 more turns. I travel with the pipe in a bracket that hangs under the MH side skirt and the 18 inch right angle hangs in a bicycle hook screwed into a wood beam under there.
It takes all of 30 seconds to set up. Some noise escapes from the slip tubes because I'm too lazy to use clamps. Maybe some day.
Go to motorcycle & quad shops, or forklift & industrial shops like John Deere dealerships and see if they will let you have used parts. Tell them about your project. With all the liability law suits, good luck with this lol. But maybe you have a friend or family member willing to go dumpster diving for ya.
2. The other thing is to baffle the floor for ventilation and sound buffering. I covered the inside of my louvered genny access door with foam to close off the holes as well as did the movie gen trick. They vent through the floor. All sound goes up or down, NOTHING sideways. All you do is cut 2 slots in the floor the width of the gen box and put a box underneath to channel the air through the baffles. You can carpet the ducts with indoor/outdoor carpeting for easy degreasing.
Please Please Please remember put in a couple cross members to reinforce the floor to replace the wood strength you removed. you can go to a welding shop and have them weld in some angle iron, Or some serious wood beams like 4X4's that can take the weight can be strapped in with carriage bolts and large washers.
You do need to separate the warm and cold side with a vertical wall of some kind. Leave room for genny jiggle and use a garden hose slit down the side for a grommet. If you feel not enough air is moving, put a 115v. squirrel cage fan on the cold air side to move it along.
This method lets you seal off the vented tin door that lets so much noise out! Now all 4 walls, ceiling and floor have some kind of sound buffering. There is more than enough ventilation. Don't fall for people telling you that you will overheat the compartment. Think about it, the original door has nothing to move the air along and heat builds up to a ridicules point and the noise is pointed right at your campground neighbor! I have never had so much as a stink eye pointed at me running my genny outside of "Campground Noise Etiquette Hours of Operation".
I would have the openings face the rear of the vehicle if you travel in wet country. You could have the cold facing forward and the hot facing rear if you gen while traveling for A/C or what have you. But certainly not both facing each other inward to prevent re-breathing hot air so easily.
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