firewall insulation
 

At the point of making the firewall insulation choice.
I have the Dan Horton tests and recommendation.

I plan on following the basic idea on material choice.
- should not catch on fire
- should not produce toxic fumes or smoke
- should meet the 2000 deg requirement

Seems fiberflax had an issue of out gassing when under high temp or fire.
This leaves me with the cerablanket. ( now known as superwool 607). Will get this from McMastercarr.

So the last two issues are how to cover the superwool and how to attach it to the firewall.

My idea is to use Nomex fabric and thread to sew covers for the superwool. This will not survive over 600 deg, but the superwool will. The only reason for the nomex is to contain the superwool fibers. Would not want them in my lungs.

So this leaves the attachment method. Thinking of using screws and nutserts. This way when the Nomex desintegrats the superwoll will still be attached to the firewall.

I know this is going to open a lot of debate, but does anyone see an issue with my idea?

Should the insulation be separate sections between the angle aluminum, or cover the whole firewall in one piece?

No debate. Fact: Nomex burns rather well when placed against red hot stainless.

Here's a quote:

Fabrics woven of Nomex? fiber have a low level of flammability and do not melt or flow at high temperatures. Above 700?F (370?C), they will degrade rapidly to a friable char.

So at the FAA standard 2000F we have:




It should cover the whole firewall on the engine side.

When it gets to that point and you are not on the ground, RUNNING away from the plane.. You are already dead...

I have a two foot square of Firewall 2000 ceramic blanket I never used I'd love to sell....
http://www.aircraftspruce.com/catalo...rewall2000.php

Dan, is there a better way to cover the cerablanket?
My intention is to use the Nomex to encapsulate insulation. As long as the Nomex does not add fuel to the fire, put off toxic fumes, or smoke, it should be okay. Correct?

I cannot comment on the functionality of the system, but 3M's Nextel fiber is woven in to cloth and blankets. It is good to 2500F. You might investigate that. It is a premium ceramic material and might be expensive. Also, coatings that used in the weaving process might outgas as well. A supplier should be able to address such questions.

I worked on a project with 312 fiber to filter diesel particulates then heated them to burn off the carbon. It and variants are quite durable under high temperatures.

Google away . . .

I cannot get to any pics at this moment but I can try to get to some showing my insulation material I used on the engine side of the firewall tomorrow and post here. Dan has done a great deal of testing and knows of which he speaks! DO NOT INSULATE ON THE COCKPIT SIDE OF THE FIREWALL! I used an insulation that I purchased from McMasterCarr that has a ceramic fiber material rated to 2000 deg F sandwiched between stainless foil on both sides. It is on the engine side of the firewall and I used no additional fasteners other than what items were bolted to the firewall (i.e. brake master cylinder, battery box, etc.). I did not install the material underneath the motor mounts! There is a thread on this forum with pics of my install on here somewhere, probably on one of the threads Dan started when he did his tests. If I find it I will come back and post the link. Think long and hard about installing on the cockpit side!

+1, I did exactly the same on my Rocket - not flying yet, final inspection tomorrow.

Which insulation from McMaster did you use? I am thinking the Ultra High Temperature roll, 1/4" x 24" x 20 feet.

IF you really need a fireproof fabric, Bill's suggestion regarding 3M Nextel is a good one. It is sold with and without sizing, the lubricant added to the fabric for weaving. They actually weave it, then burn off the sizing to remove it if you order unsized. Unsized Nextel doesn't even smoke when you apply a torch.

That said, applying even the best fire protection insulation to the cabin side of a firewall is inferior (in every respect) when compared to insulating the engine side of the firewall.

Here's what you get when you do it the right way. You're looking at the cabin side of a simulated Vans firewall; same aluminum angle and rivets (which melt at 1100F, BTW), same stainless material. The engine side is well insulated with a layer of ceramic felt and stainless foil. The same burner is operating on the other side, running at 2000F over 25 sq inches. This 5 minutes into a burn. The small black sheet is a radiant heat target positioned 6" from the back side of the "firewall". It simulates the soles of your shoes, which have just passed 200F. The small dark brown spot is an AN3 bolt, an experiment to look at the heat transfer capability of a fastener. As you can see, it makes a hot spot. We can expect any steel fitting to do the same, which is why it would be dumb to think insulation on the engine side makes adding bad insulation on the cabin side "safe". Note that the firewall structure, complete with its aluminum components, is entirely intact. It will remain so no matter how long the fire lasts.



Same setup, night shot, no flash. Sure do like that (relatively) cool, dark cabin side:



§ 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.