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Firewall sealant and Fire Safety

I'm not a big fan of the pillowing look, either, Jon. But it's what I went with for the functionality, and since I finished building and started flying, I only have to look at it about three times a year for a few hours. Doesn't bother me enough to mention.

Once you get going bolting on accessories, you won't have much exposed SS foil left to look at. It's fine.;)
 

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Bill, an aside...the firewall penetrations for control cables (circled) don't really need firesleeve. Just install the cable and pump the penetration full of FireBarrier. Gas tight and fireproof. It's not hard to cut the cured silicone if you ever need to replace the cable.

A penetration for wiring passage is a good candidate for firesleeve because it allows adding or removing wires. Those tend to be off to the side like the one in the foreground where they are not so exposed to fuel fire.
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I believe that burning paint might smell bad but do not believe it is generating any serious amount of toxic fumes.

It doesn't take much smoke to be a breathing problem. Since we don't know what is in any given paint formulation, I'm not willing to go beyond "probably".

Insulation delays temperature rise. It doesn't stop it. The goal is to buy time, i.e. the ability to remain in control.

I don't think folks grasp how hot the firewall can get given an FAA-standard fire, even with an insulation package. The photo below is from a recent test, 0.060" 970 fiberfrax with 0.002" foil. The blue wires are thermocouples, with the temperatures displayed on the red meter. The black meter is the hot side thermocouple. The aluminum angle on the back side of the "firewall" has passed 400F at 1:30 into the run, so if painted, it would be generating smoke. Temperature will rise to 750 or so in 10 minutes.

The real goal is the second number on the red meter. It's the black heat target 6" aft of the firewall, a proxy for the soles of your shoes.
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The potential issue would be smoke generation, if you got a good fire going on the forward side. I don't know at what temperature EkoPrime might start generating smoke, or its components. Probably low risk.

As a data point, I had this response from Andy at Stewart Systems regarding painting the parts riveted to the firewall.

We have not done lab testing on it, but I can tell you it will not be any issue unless your engine compartment is on fire. I have painted Continental cylinders with Ekopoxy and Ekocrylic and it has held up very well. I also did spark plugs with that combination. They discolored a little, but otherwise have held up great over many hours of operation.
 
The cured Shore A hardness is very low at 20, half that of 3M Firebarrier 2000+. The SDS doesn't mention calcium carbonate, a major ingredient in the 3M product. I think the mechanism is the release of CO2 for fire suppression during decomposition, but I'm no chemistry guy. I note a caution regard oils.

I happen to have some test sealants in process and hope to report more later. Unfortunately the Sika product isn't one of them. My reliance on the FireBarrier 2000+ product is partially based on flying it 12 years in an engine compartment.

Thanks for your input Dan. I suppose as a fay sealant the hardness isn’t too important? Other than that I understand it’s hard to know from just a data sheet. I did find fire barrier at one supplier here - $129 plus shipping - per tube - minimum 12 tubes!!
 
Thanks for your input Dan. I suppose as a fay sealant the hardness isn’t too important?

If you're talking about the fay seal between SS overlaps, low Shore hardness should not be a problem.

I did find fire barrier at one supplier here - $129 plus shipping - per tube - minimum 12 tubes!!

At those prices you might shop for some Dapco 2100, the advantage being known level of oil resistance.

As a data point, I had this response from Andy at Stewart Systems regarding painting the parts riveted to the firewall.

We have not done lab testing on it, but I can tell you it will not be any issue unless your engine compartment is on fire.

Well, that's what I'm talking about...temps in excess of 400F. An insulated firewall in normal operation is just bare toes warm. I'm not kidding. I've been kicking my shoes off and sticking my feet through the rudder pedals for years now...
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I did find fire barrier at one supplier here - $129 plus shipping - per tube - minimum 12 tubes!!

Hi Trent, Repelec distribute 3M Fire Barrier 2000+ in Australia. Repelec wouldn't sell to me direct, but my local electrical wholesaler ordered a single tube from them (cost $78 in Jan 2022).
 
Hi Trent, Repelec distribute 3M Fire Barrier 2000+ in Australia. Repelec wouldn't sell to me direct, but my local electrical wholesaler ordered a single tube from them (cost $78 in Jan 2022).

That’s an awesome lead, Greg. Thank you!
 
Fire prevention priorities ?

This "sticky thread" covers what happens when the fire is raging at your firewall very well. I am deliberating whether all the ugly foil and sealant is worth the trouble. Fire sleaved hose might fail around 500F. Wire insulation probably sooner. When it gets quiet, the fire goes out.
So, how can we prioritize fabrication and maintenance to avoid a fire ?
* Fuel fittings can leak ,ie AN fittings, nuts and pipe threads
* Fuel fittings can break due to vibration and lack of support
* An arcing "fat wire " could start a fuel line fire

What am I missing ? Your experience is sincerely appreciated.
 
What am I missing ? Your experience is sincerely appreciated.

Larry, you're not missing anything. The #1 priority is to prevent fire with quality fabrication and careful maintenance.

Thankfully, a very high percentage of folks installing an insulation package on the engine side of a firewall will never face a fire. Of course, the same thing can be said about safety wire. Or nomex gloves. Or firewalls, for that matter. If it will never face a fire, why bother with stainless steel?

Me? I decline the debate. Better to view it as a comfort insulation. Everyone can enjoy that aspect, on every flight. As a bonus, when installed on the engine side it won't contribute to killing anyone if there is a fire. Instead, it will buy time.
 
Thanks Dan

My objective didn't come across well.
I was just hoping to add anything to improve my build or inspection awareness upstream of the firewall. No argument with "employ all options to maximize favorable margin".
 
I hear ya'. Most common sin, in my opinion? Poor hose routing. Trouble is, installations vary so much there is no way to tell anyone what is good or bad.

The RV-7 in my shop right now had a hose routed against motor mount tubes, in close proximity to an exhaust pipe. Over time, it exhaust heat baked the rubber core to rock hard brittleness. It caught fire on the runup pad.
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Exactly where and how do I apply the sealant on a quickbuild?

I have a quick build RV8. I haven’t installed the cowl hinges or top forward skin. I will use the 3m Fire Barrier 2000+ Dan Horton recommends. But I can’t figure where or how to apply it on the quickbuild. On the inside it just falls off in the event of a fire. I can’t see how to get it between the firewall flanges and adjoining skins even when they haven’t been riveted. Any pictures of the application on a quickbuild would help me.
 
I have a quick build RV8. I haven’t installed the cowl hinges or top forward skin. I will use the 3m Fire Barrier 2000+ Dan Horton recommends. But I can’t figure where or how to apply it on the quickbuild. On the inside it just falls off in the event of a fire. I can’t see how to get it between the firewall flanges and adjoining skins even when they haven’t been riveted. Any pictures of the application on a quickbuild would help me.

Ken, the only way to get between the skin and the firewall flanges is to pry the flange out a 1/16th of so and wipe in some sealant. Most folks don't bother.

Mostly you want to be sure to close the holes at the base of the slots between each flange section.

Sealants do tend to fall off hot steel, but stays pretty well if given just a little mechanical advantage. A small fillet added to the engine side after riveting should be fine, as is a very small fillet on the back side.

Silicone sealants and paint don't get along, but proseal is paintable. If desired, wipe a tiny bit of proseal into the edge of the fay joint prior to the paint shop. No proseal elsewhere.
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A detail worth noting...

The standard brake fluid reservoir is a welded aluminum tank with an outlet nipple extending through the firewall. The plans call for a nylon fitting screwed in the nipple, then nylon lines run to the brake masters.

The photo below suggests an aluminum can with a nylon nipple might not be such a good idea. In this case the can got hot due to an engine compartment fire on the ground. Aluminum is a terrific conductor of heat, so not surprisingly, heating the can melted the nylon fitting, which then released the brake fluid into the cockpit. Kindly recall brake fluid is flammable, 83282 a bit less so (450F flash point) than 5056 (250F). Not that it matters. The nylon didn't melt until about 490F, so the fluid there is already at the flash point.

What we have here is a fire transfer device.

So what to do? The reservoir below is encased in a simple 0.016" stainless shield. There is a 1/16" insulation liner, and it's sealed with FireBarrier 2000+. It will preferably get a steel fitting on the cabin side, but I would not have any concern for an aluminum fitting, because it's not going to get hot enough to be a concern, given both the can and the firewall itself are insulated on the hot side. Plumbing will be steel braided nylon, not bare nyloseal or similar.

Let's build better airplanes...
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Or... you can mount the reservoir firewall aft as I did. I have a polycarbonate one so you can visually check the fluid level with a little neck craning.
 
Or... you can mount the reservoir firewall aft as I did. I have a polycarbonate one so you can visually check the fluid level with a little neck craning.

Where did you put it?

On the -8's, the rear corner of the forward baggage compartment works really well.
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Where did you put it?

On the -8's, the rear corner of the forward baggage compartment works really well.
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That's what I did - easy to check by opening the baggage door, one less firewall penetration.
 
Me three. Easy install by putting the T fitting just after adell clamps instead of at the reservoir and running one line to the reservoir.

Since these nylon lines are not under pressure, I used a heat gun to relax the bend.
 

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Me three. Easy install by putting the T fitting just after adell clamps instead of at the reservoir and running one line to the reservoir.

Since these nylon lines are not under pressure, I used a heat gun to relax the bend.

Duplicate it with aluminum line from reservoir to tee, steel braided to the master cylinders, and AN fittings everywhere. Nothing to do with fire. It just guarantees you'll never have brake fluid on the floor.
 
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