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How I did my Firewall Insulation

Mike D

Well Known Member
There are many ways (and many opinions) on how to do your fire insulation. Here is how I did mine. I'm sharing, so don't flame me too much :)

Dan H has some good reviews of different insulation materials. So that is a good place to start. I did my own very primitive burn tests based on the reviews from Dan.

My goals, in case of fire, were to:
1. Do no harm (insulation cant burn or create smoke)
2. Keep my feet from burning while trying to get the plane on the ground.

Additional goal was easy maintenance and good wear properties.
Of course this is in addition to other precautions like steel fittings, and good firewall pass through. (power cable pass through is being redone)

I used:
1. Ultra-High Temperature Ceramic Insulation Roll, 6 lbs./cu. ft. Density, 1/4" McMastercarr.
Ultra-High Temperature Ceramic Insulation
2. 3M fire barrier 2000
3M+FIRE+BARRIER+2000
3. Reynolds Wrap? Super Strength Foil

- The insulation will stop the heat, wont burn, and wont create any smoke or fumes.
- The 3M fire barrier is there to plug holes
- The aluminum is there to encapsulate the insulation.

Ceramic insulation with a piece of paper on top. This is 30 sec into the burn. I can touch the insulation with my bare hand 1 second after flame removal.
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On the floor, I cut strips, and used the fire barrier very sparingly to tack the aluminum foil and insulation. Just enough to flip it over and rivet it in.
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On the firewall, I built brackets from 0.025 aluminum, and riveted them to the aluminum angle on the firewall. I then built an inner wall from 0.025 aluminum to hold the insulation/foil in. These inner walls are shorter than the full height so can remove them without having to remove the rudder peddles. These are just for controlling the heat from burning my feet. They also clean up the look of the firewall. I will also make side panels from 0.025 aluminum with insulation on the first 10".
The left side has the inner wall installed, the right side shows the brackets (no inner wall)
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The tunnel has similar but uses 1/8" insulation

So, for better or worse, that is how I have done it.
Take this as one data point and do your own tests. Vans is comfortable with blank SS firewall. This just keeps the heat off my feet without creating any additional hazards.


----------------------------------------------
On another note:

I bought this kit already started. So in this case I had to remove the gear support, drill out the floors, and remove the black foam that was there for "sound insulation". The black foam smokes badly when exposed to heat. Please don use it near your firewall.

Removing the floor and taking out the foam.
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Here is the foam where I put flame to the aluminum next the foam. The aluminum milted (as expected) and the foam made lot of white smoke. :(

This is the foam I removed - (NOT for firewall) - http://www.aircraftspruce.com/catalog/appages/supersoundproofsheet.php?clickkey=7775
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Mike - thanks for posting this thought-provoking information.

In your estimation, would the ceramic insulation provide enough sound reduction to make it viable for that purpose in areas near to but aft of the firewall?
 
not for sound insulation

No, I don't think it will provide much sound insulation properties. There was a noticeable difference in the bare floor sound vs. with the new insulation installed, but not enough to make a difference when in an actual flying environment.

After flying my -6A for many years, sound insulation is very far down on my list of priorities in the build. I'll take the weight savings and invest into some headsets. Just my opinion.
 
Ceramic

Mike,
How does the ceramic mat do with moisture? Does it wick it up and retain the moisture?
cj
 
CJ,
Good concern. I do have corrosion concerns and that is why I used aluminum instead of stainless to encapsulate the insulation.

The 1/4" ceramic insulation feels (and is open like) a polyester fiber fill like they use in blankets, stuffed animals, and pillows. So I don't think it will hold moisture, but I have not tested for that. If you were to pour water on it, the water would go straight through the insulation. It will not soak up any water if placed in a dish of water.

The 1/16" insulation I used for the tunnel is more solid, but water does not soak into it.

Any idea how I could test for it?
 
Testing found that insulation placed on the cabin side of a firewall is no where near as effective as insulation placed on the engine side.

The key reason to fully encapsulate the above ceramic batt insulation is its cancer risk. Fiberfrax felt is a lot easier to work with, not as risky, thinner, and works great under stainless foil on the engine side:

http://www.aircraftspruce.com/catalog/appages/fiberfrax.php?clickkey=6977

http://aircraftproducts.wicksaircra...0j?&plpver=10&origin=keyword&by=prod&filter=0

Do NOT use fiberfrax felt on the cabin side, as it outgasses binder when heated.

Super Soundproofing foam's "FAR 25.853a certification" is, in my opinion, dangerously misleading. Don't install any sort of rubber or plastic insulation near the firewall, or under the forward floor.

§ 23.1191 Firewalls.

(f) Compliance with the criteria for fireproof materials or components must be shown as follows:

(1) The flame to which the materials or components are subjected must be 2,000 ±150 °F.

(2) Sheet materials approximately 10 inches square must be subjected to the flame from a suitable burner.

(3) The flame must be large enough to maintain the required test temperature over an area approximately five inches square.

(g) Firewall materials and fittings must resist flame penetration for at least 15 minutes.

§ 23.1182 Nacelle areas behind firewalls.

Components, lines, and fittings, except those subject to the provisions of §23.1351(e), located behind the engine-compartment firewall must be constructed of such materials and located at such distances from the firewall that they will not suffer damage sufficient to endanger the airplane if a portion of the engine side of the firewall is subjected to a flame temperature of not less than 2000 °F for 15 minutes.
 
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Do NOT use fiberfrax felt on the cabin side, as it outgasses binder when heated.

I was about to make a post asking about using Fiberfrax on the cabin side, scratch that idea...

I used 1/8 Fiberfrax and .0002 SS foil on the firewall side so far. It seems to offer some sound dampening but not a lot. I've used Super Sound Proofing 1/2 Foam all over minus the front floorboards (Used firestop/blocker spray foam) and in the back part of the tunnel I did Foam mat on top of 1/16 Fiberfrax and then wrapped the entire thing in SS foil and then pressed it on in the space, no adhesive holding it down but it's a tight fit.

For the front part of the tunnel I was going to do similar with the 1/16 Fiberfrax, maybe double it and then just wrap it in SS foil. Then 3M 2000+ caulk the areas around the fuel pump, filter and red cube mount.

After reading the above I plan to keep this foam stuff away from the firewall, but what are some other are some options on some type of sound proofing on the cabin side?
 
After reading the other thread about insulation I'm going to really rethink some things.

Probably wasn't the best idea using the spray foam under the front floorboards, seemed like a fantastic idea at the time and had seen where some other builders did similar. After seeing the videos where it catches on fire it doesn't give me a warm fuzzy about having it on the plane. That said I don't really know a reasonable way to remove it, hopefully the risk is somewhat mitigated by it being in a confined space.

I'm still unsure what I want to do on the Cabin side and the front part of the tunnel. I'm going to do some home tests on these stainless steel wraps and see what it takes to get it to burn through, gas, ect... should be fun playing with some fire! Also it was pointed out that doing this might actually make the hot tunnel issue worse by effectively not letting any heat escape... so that's a concern.
 
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