Fiberfrax on Firewall Question...

[gtmule]

Originally Posted by DanH

BTW, cutting a hole in stainless foil is easy. Just use the corner of a razor blade to make a series of connecting punctures...poke, poke, poke.

Yep, recognize that ALL your foil edges will be covered in firestop caulk or tape, and really any method of cutting is fine, you'll never see the edge once you're done.

For the pass throughs, I did the tube and sheet with firesleeve, but made them myself. Here is a picture before the foil went on:



The white insulation is just held up with a bit of RTV at this point, eventually the firesleeve/firestop caulk and the various items mounted will hold the foil on, which will support the insulation.

And here's an "after" picture:



I'll install hose clamps and more firestop to seal everything once I know I'm done pulling wires. I have lots of small passthroughs, rather than a couple large ones, just because I was working with existing holes. If you were building a new airplane, I'd recommend two large (1", maybe more) ones.

You might be able to see in the second picture that I slid the firsleeve over the stainless tube and used a bit of firestop to bond the end of the firesleeve to the foil. This seals it, but also turned out to be a really good "mount" for the foil, helping to stabilize it.

I'm considering making up a batch of pass-throughs for my hangar neighbor who is building a -9A. If anyone else wants some, let me know what size we can come up with a price, I guarantee they'll be cheaper than the ones spruce has (which are absurd, at $45 a pop).

[southtarnation]

Originally Posted by gtmule

I'm considering making up a batch of pass-throughs for my hangar neighbor who is building a -9A. If anyone else wants some, let me know what size we can come up with a price, I guarantee they'll be cheaper than the ones spruce has (which are absurd, at $45 a pop).

I would buy two or three. And am ready for them pretty soon.

[JanRV6UK]

Count me in on the pass-troughs as well .. I have no holes yet - so maybe a few in 1" and in 1/2" would do ... What material are they made off ? looks like 4130 tube welded to a plate .. which you then rivet on with Monel rivets ?? What is a good source for the insulation material ?

[gtmule]

Originally Posted by JanRV6UK

Count me in on the pass-troughs as well .. I have no holes yet - so maybe a few in 1" and in 1/2" would do ... What material are they made off ? looks like 4130 tube welded to a plate .. which you then rivet on with Monel rivets ?? What is a good source for the insulation material ?

I used 304 stainless, .032" thick and #8 screws to do the passthroughs, but rivets would obviously work just as well.

The insulation is mcmaster part # 93315K51 (1/4" ceramic insulation 2'x20') the foil is 3254K16 (.002" 321 stainless 20"x10' roll). Mcmaster also sells aluminum standoffs (ex: 92510A642 for a spacer with a clearance hole for a 3/16 screw, 1/4" thick, 3/8" OD).

I've got plenty of insulation and foil left (more than half of each), if someone wants to buy it off me, though mcmaster ships it so much cheaper than I can that it may not make sense....maybe for someone local?

[DanH]

The insulation is mcmaster part # 93315K51 (1/4" ceramic insulation 2'x20')?

Hmmm...a low density wool.

Fiberfrax is a Unifrax trade name covering a whole range of ceramic insulation products. Among homebuilders the word means Fiberfrax 970 felt (the manufacturer calls it "paper"). I think it was Rutan who introduced it to us.

http://www.fiberfrax.com/files/Fiberfrax-Papers.pdf

It is a dense felt (about 10 lbs per cubic foot) held together with an organic binder. It forms a nice firm sheet, easy to trim to exact dimensions and smoothly cover with metal foil or fiberglass fabric.

The organic binder (glue) makes it more durable than a wool blanket product which is simply tangled long fiber. The durability issue is perhaps important given that firewalls vibrate.

Spruce, Wicks, etc all carry 970.

[gtmule]

It's pretty well secured, but if it doesn't hold up, (the only failure mode I could see is it pilling up on the bottom) it won't be that bad to start over and try something else.

[flyingbeaver26]

I've been reading up on all the old threads about FWF insulation and sound dampening... I've got foil and fiberglass on order with McMaster. But just curious, is the general guidance to leave the inside surface of your firewall completely bare? No paint, no insulation?

Since this SS and fiberglass mat will buy extra time to protect the pilot if a FWF fire ensues, you don't want anything inside the cockpit smoldering and chocking you as you make an emergency landing. So I'm thinking I need to break out the paint stripper and remove the paint in this area, right?

[DanH]

Yes and yes.

[Bill Boyd]

Steel EMT fittings, https://external-content.duckduckgo....&nofb=1Cockpit fitted on the engine side with firesleeve, filled when finished with FireBarrier2000. Cabin side showing nuts, visible through the panel cutout:



Firewall side, before wires and cables pulled. The requisite cables and wires are now in place, and all fit with room to spare:

[Checkmate]

I used .005 SS Shim Stock, 1/8" FiberFrax, 3M Barrier 2000+. No wrinkled tinfoil look like the thinner stuff but some oil canning is to be expected around the areas where you attach items over it but still easy to work with, gloves still a must. Also a hydraulic punch works great for making nice clean round holes. Ordered everything from McMaster-Carr.
All steel or stainless purchased or custom made fittings used for any pass through items. No painted surfaces on the cockpit side.

https://lh3.googleusercontent.com/Rs...M=w800-h450-no

https://lh3.googleusercontent.com/77...M=w450-h800-no

https://lh3.googleusercontent.com/xh...g=w800-h450-no

https://lh3.googleusercontent.com/Bg...k=w800-h450-no