Fatmat on firewall

[rcotner]

Does anyone out there know if fatmat will withstand the temps seen by the inside of the firewall?

Ray

[MiniVanMan]

What are you trying to accomplish first?

Second, FatMat is butyl based rubber. It gets gooey in summer heat temps. Add engine heat to it, and you'll probably be able to suck it through a straw.

[rcotner]

I want to minimize vibration in the firewall. I have sprayed lizard skin on the engine side. I thought it might be good to put sound deadening material on the inside as well. I have heard good things about fatmat but if it is a soft rubber with a low melting point, that will clearly not work very well. Are there any other suggested products?

[MiniVanMan]

Point of diminishing returns. Lizardskin is a product designed to do exactly what you want. Do it on both sides if you're that concerned with vibration.

There's a lot of misconception on vibration dampers. More isn't necessarily better. It's just more.

25% coverage with a damper will provide about 80% of the damping on a panel. 100% coverage will not increase that 80% that much. Lizardskin isn't necessarily as effective as a high mass butyl based damper, but it is designed for heat. If you're looking to overdo it, then just coat the inside as well the outside. Though there are butyl based products that have high heat tolerances, but the question becomes "tolerance till what?", complete failure where the foil detaches from the substrate, or it turns into a puddle oozing down the panel it's on?

Also, being in Oregon, I'm sure you get some cold days in winter. What's good to 300* F, may freeze, crack and fall off at 20*. The butyl acts a damper and an adhesive. How much temperature fluctuation can it handle before it loses it's adhesion and elasticity?

Don't get me started on people that cover their entire cars in Dynamat/Fatmat/Secondskin/Rammat, etc, etc. Here's a good link to go through that targets many of the issues with noise and vibration in a car and how to best tackle them without adding 100 lbs to your car's weight.

http://www.sounddeadenershowdown.com/

[FFinisher]

Does anyone out there know if fatmat will withstand the temps seen by the inside of the firewall?

Ray

Yes, I have used this product on mnay cars in many applications. It is just fine.,

[MiniVanMan]

The other problem with vibration dampers like FatMat (or any of the others) is that when they fail, you really don't know because they're under something. Don't get caught up on brand. FatMat is no better than Dynamat, and Dynamat is no better than Rammat. Nobody is making their own, it's all sourced product from one Chinese factory or another.

That being said, the question again is, is it important enough to use in the application you intend to risk the potential failure due to the stressed conditions it will endure.

Not saying that vibration damping isn't important. I'm just saying use the right product for the application. A damping compound like Cascade's VB-1X is a better solution than a butyl based mat on the area you're looking to cover. Use your damping mats on large flat panels like your floors, quarter panels, door skins and such. Don't worry about corners and tight curves as those don't resonate to begin with. Where two panels meet but don't necessarily join, fill the edges with extruded butyl based rope and let that mash into place.

Point being, the products exist to do exactly what you want. Just making sure you're using the right product for the specific application.

If you can't tell, I HATE the damping mat myths that exist out there.

[rcotner]

Thanks for taking the time to comment MiniVanMan. I appreciate your insight. I have already mounted the firewall after coating only the outside. I will fill the space with thermal barrier like Dynaliner but will avoid the butyl rubber on hot surfaces. I asked the question for precisely the concern you addressed. Thanks again!

[68GT500MAN]

MiniVanMan makes some great points that I will use in this build. To answer your original question: I have never had any problem with FatMat "melting" or becoming "gooey" in any of my builds.
Doug

[rcotner]

Thanks for the feedback MiniVanMan!

[rcotner]

Thanks for the feedback MiniVanMan!

I meant thanks for the feedback GT500man! Do you really have a vintage GT500? That is my dream car!

[Bob Cowan]

Vibration in a flat panel can be really annoying; often called "Tin Canning" or "Oil Canning". It can set up wierd harmonics in the car. I was kinda worried about it when I built my car. So I bought a cheap bead roller from harbor freight, and rolled beads in a lot of panels. Especially the big ones. Doesn't seem to be an issue. Might not have been without the beads, either.

Lizard Skin is a great heat insulator. If you put it on the outside of the fire wall, You could probably put ice cream on the inside and it wouldn't melt.

[DaveSL33]

Is it possible, or does it make sense to use Dynamat over Lizard Skin to further reduce noise?

Vibration in a flat panel can be really annoying; often called "Tin Canning" or "Oil Canning". It can set up wierd harmonics in the car. I was kinda worried about it when I built my car. So I bought a cheap bead roller from harbor freight, and rolled beads in a lot of panels. Especially the big ones. Doesn't seem to be an issue. Might not have been without the beads, either.

Lizard Skin is a great heat insulator. If you put it on the outside of the fire wall, You could probably put ice cream on the inside and it wouldn't melt.

[MiniVanMan]

Vibration in a flat panel can be really annoying; often called "Tin Canning" or "Oil Canning". It can set up wierd harmonics in the car. I was kinda worried about it when I built my car. So I bought a cheap bead roller from harbor freight, and rolled beads in a lot of panels. Especially the big ones. Doesn't seem to be an issue. Might not have been without the beads, either.

Lizard Skin is a great heat insulator. If you put it on the outside of the fire wall, You could probably put ice cream on the inside and it wouldn't melt.

I'm not familiar with Lizardskin (yet). I'm a sound guy, so I look at this from a sound perspective.

Panel beading works well. It uses the same principle that you'll find in corners and curves on a piece of metal.

Here's the test for everyone. Take a piece of sheet metal and hit it. It'll resonate at a pretty high frequency. Now, fold it over into an arc and then hit the crest of the arc. The resonance is much lower. The tighter the bend, the lower the resonance. This is why slathering Dynamat all of over a car is pointless. It also shows how the panel beader reduces resonance as it creates beads that form small arcs.

I think a vibration damper is a better overall solution that a panel beader, however, if you're racing, and weight is a huge concern, a panel beader will benefit quite a bit. Any panel vibration is lost energy from somewhere. Ultimately, the best way to decrease vibration is to increase mass, but go with what best fits the application and goals. Dynamat is an easier solution than a panel beader, that's for sure. Especially when utilized in an efficient manner.

Is it possible, or does it make sense to use Dynamat over Lizard Skin to further reduce noise?

No. Dynamat is a vibration damper. Not a noise reducer. In fact it's horrible at noise reduction. It works for vibration reduction.

It sounds like semantics, but it's a point I want to make clear when we're tackling a specific issue.

Vibration dampers reduce resonance in a panel. Noise barriers block noise from entering at a particular point. Two completely different products for those two different applications. A vibration damper is a horrible noise barrier. A noise barrier is a horrible vibration damper.

Now, there's no reason you couldn't put Dynamat over Lizardskin, but I'd have to ask the same question I asked to begin with in this thread. Why??

[MiniVanMan]

I also want to point out that there's another vibration damping solution that comes in the form of a liquid. Lizardskin makes it. Cascade makes it. There are places where it makes better sense to use it. A firewall is probably one of them.