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Firewall sealant and Fire Safety

How about a solvent test...

I have plenty of cured CS1900 and more FireBarrier. No trouble to submerge samples in oil. Heck, I've had some urethane rubber samples in oil more than two years. Same for proseal samples in MEK/lacquer thinner mix, and in 3% hydrogen peroxide.

Fuel? If you have that much fuel spraying around the engine compartment perhaps it would be best to review the burn tests again ;)

The photos of various products failing miserably are pretty convincing to this old fireman.

None of these products failed miserably. Some exhibit unexpected issues and some are pushed to the outer limits of their performance or beyond. The idea is to study how they work and how they fail, then create ways to use them effectively.
 
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Thread drift---

None of these products failed miserably. .

My apologies, I was not too clear was I??

The reference was to the firewall insulation you did the burn test on.

Thanks again for all the effort, and sharing of the knowledge
 
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Fuel? If you have that much fuel spraying around the engine compartment perhaps it would be best to review the burn tests again ;)


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Dan
I see your point. However, I was thinking more along the lines of fuel being spilled during maintenance, etc. I look forward to the added tests.
Charlie
 
First off I would like to thank Dan for his efforts in furthering safety with his testing and detailed summaries, inflight fire certainly ranks #1 with me and I will continue to reduce it's effects and minimize the risk on my aircraft.

I mentioned in a earlier post that I had used Resbond as a OEM of packaging equipment, a little background:

Our application consisted of a tubular electric heater and sealer assembly that operated at about 1000?F and recepicated at a rate up to 800CPM.

The design criteria required a product that would insulate at the 1000?F working and possible higher failure temperatures, stand up to the high cyclic loads, and not produce any hazardous gases should we lose control and have a thermal runaway.

All of the products we selected performed well at the normal operating temperatures, where the products failed (with the exception of the Resbond) was in the thermal runaway condition where they produced hazardous gases.

We selected Resbond in 1982 and it is still used in this and other applications to this day.

Dan pointed out in his post the importance of mechanical bonding, I could not agree more. As he identified, the one disadvantage of Resbond is it lacks the flexibility of the other products requiring some design thought to insure the product stays locked into the intended position.

Thanks again Dan.
 
...the one disadvantage of Resbond is it lacks the flexibility of the other products requiring some design thought to insure the product stays locked into the intended position.

Actually I think mechanical fixation is a sensible requirement for all the materials. Some stuck in this burn test, but if I hooked a shaker to that stainless panel I'd bet none of the strip samples would remain adhered when heated.

Cold sealing is another story ("cold" being less than 300F). Obviously the silicone sticks well and will remain absolutely gas-tight, the key requirement when the airplane is not on fire. Our engine compartments are full of carbon monoxide and our cockpits are enclosed; we must not allow air exchange.

My only concern for Resbond is cohesive or adhesive failure, cracking or disbonding from a collection of vibrating sheetmetal flying in close formation and thus losing a gas-tight seal. For example, consider a filet to close the openings where the firewall flange, fuselage shell and cowling mount hinge all meet. For sure the firewall vibrates and the hinge section is worse; we've all seen 'em with the eyes broken off.

I don't have any more Resbond here or I'd set up some vibration tests. Somebody should, because Resbond is by far the closest thing to fireproof you'll ever squeeze from a tube.
 
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The reference was to the firewall insulation you did the burn test on.

Ok, the rest of the story...

Some time ago Mike sent a sample of the insulation installed on the cabin side of his RV-10 firewall. It came to him via a third party rather than a vendor. Mike didn't know for sure what it was, and he had become concerned. Although I could not identify the brand with certainty, I was pretty sure it was a polyester fiber insulation similar to a sample previously tested, and probably the same as that involved in a recent RV-10 incident. I suggested he remove it ASAP.

This weekend my buddy Stan and I were standing around the shop enjoying a cool one after doing the sealant burn and I remembered Mike's sample, still in the envelope on the shelf. We walked outside, clamped it to a stainless panel, and hit the burner. This was 15-20 seconds later:

Mikes%20Sample%201.jpg


In this photo the burner has been turned off almost a minute. Consider how long that minute might be in the air.

Mikes%20Sample%202.jpg
 
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foil/insulator sandwich

The firewall perimeter got a filet of FireBarrier before adding the foil/insulator sandwich,

Dan, what product did you use for the sandwich? Engine or cabin side? How did you attach it to firewall?
 
On the engine side, I'd suggest ordinary Fiberfrax felt (available Wicks, Spruce, etc) under stainless steel foil, attached with SS pop rivets and sealed around the perimeter with 3M Firebarrier 2000. Common 24" wide SS foil is fine, actually preferred. Overlap a mid-panel seam about 2 inches and cover it with one strip of aluminum foil tape. In a fire the aluminum tape will melt away instantly and provide a directed escape path for the outgassing binder in the Fiberfrax.

My%20Firewall.jpg
 
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On the engine side, ordinary Fiberfrax felt (available Wicks, Spruce, etc) under stainless steel foil, attached with SS pop rivets and sealed around the perimeter with 3M Firebarrier 2000. Common 24" wide SS foil is fine, actually preferred. Overlap a mid-panel seam about 2 inches and cover it with one strip of aluminum foil tape. In a fire the aluminum tape will melt away instantly and provide a directed escape path for the outgassing binder in the Fiberfrax.
Dan, What thickness stainless foil (shim stock) did you use? I'm thinking ~.003".
 
For firewall insulation on the engine side, Firewall 2000 looks to be equivalent? Ceramic blanket with SS foil on the heat side?
In an earlier thread, Dan mentioned that he hadn't tested Firewall 2000. Is there any reason to think this would be an unsafe product to use (attached with SS blind rivets) on the engine side of the firewall?
http://www.aircraftspruce.ca/catalog/appages/firewall2000.php
 
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In an earlier thread, Dan mentioned that he hadn't tested Firewall 2000. Is there any reason to think this would be an unsafe product to use (attached with SS blind rivets) on the engine side of the firewall?

I didn't bother testing it because the specs say it is rated at 1000F, not 2000F. Doesn't make it unsafe on the engine side, but it doesn't make it optimum either.
 
Long term add-on.....

One year ago I submerged samples of cured CS-1900 and cured 3M FireBarrier 2000+ in a jar of motor oil. After all, aircraft engine compartments do tend to be oily.

After a year I find very little physical difference between the oiled samples and dry control samples. Hardness, toughness, etc all seem to be unaffected.
 
Supplier and shelf life of 3M Fire Barrier 2000 Plus

Where did you purchase your 3M Fire Barrier 2000 Plus? The 3M pdf says the effective life is 12 months after manufacture. Anyone have any insight on this shelf life?
 
Try Home Depot, Lowes, or whatever bigbox construction store is local. Also, good electrical supply houses usually stock it, or something similar.

Charlie
 
Try Home Depot, Lowes, or whatever bigbox construction store is local. Also, good electrical supply houses usually stock it, or something similar.

As stated previously, the big box stores only seem to carry latex based intumescent caulk, not FireBarrier 2000 silicone. Not at all what you want.

Any thoughts to using Vans heat reflecting material over the fiberfrax as a low cost substitution of stainless steel?

Any sort of shiny metal film over fiberfrax will reduce heat engine transmitted to the cabin during normal flight. An aluminum foil, however, would be totally useless as a fire barrier. Seconds after application of the standard 5" x 5" 2000F hotspot, the aluminum will evaporate. Then the binder will burn out of the fiberfrax, and airflow will blow the loose fiber off the firewall.
 
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The link you provided does not specify what type of metal the heat reflecting material is.


Yeah the Vans website does not say what it's made of. It's intended for under the cowl. I just saw how cheap it is and was wondering if it could work in this application. Dan's assumption that it aluminum is probably accurate due to it low cost.
 
Yeah the Vans website does not say what it's made of. It's intended for under the cowl. I just saw how cheap it is and was wondering if it could work in this application. Dan's assumption that it aluminum is probably accurate due to it low cost.

It's aluminum. Works great over fiberfrax to protect fiberglass and paint.

Cowl%20Insulation1.jpg
 
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To those who have bought the ss shim stock, were you happy with the .003 thickness or did you buy .002 or something thicker and are you happy with your decision? I'll need 100" of it for my -14 and that stuff is kinda pricey.
 
This report has been linked in at least two threads. Read it again, carefully.

https://www.atsb.gov.au/publications/occurrence-briefs/2018/aviation/ab-2018-124/

Most readers focus on the battery meltdown. Although thermal runaway does appear to be the initial issue, it was not the proximate emergency. The emergency was fire in the cockpit, resulting in burn injury to the pilot, his exit of the still moving aircraft, and the ultimate total loss of the airframe due to fire.

Ok, so there was an ignition source (a hot battery) on the engine side of a firewall. The question investigators fail to ask is how did a hot battery result in open flame on the cockpit side of the firewall?

The J170 has a firewall assembly typical of composite aircraft, a bonded-in plywood core faced with a ceramic fiber sheet (fiberfrax) or similar, then covered with a stainless steel sheet. Here's a link to the construction manual; check pages 45 to 53:

https://jabiru.net.au/wp-content/uploads/2018/05/Jabiru-J170-Constructors-Manual-WEB.pdf

I've never burn tested a SS/fiberfrax/plywood assembly, but I suspect the bare stack-up would do moderately well. The problem is practical detail. As noted in this thread and elsewhere, steel fittings and bolts are both capable of point heating. They can glow red and transmit (by conduction) more than enough heat to provide an ignition hot spot.

Look at the photo at the bottom of page 53, a view of the cabin side after installation of all the bolts and fittings:

Jabiru%20Firewall%201.jpg


Now jump to page 234:

Jabiru%20Firewall%202.jpg


Yes, that's foam insulation glued over all those ignition point sources.

Folks, I cannot absolutely state that in this case the fire transfer mechanism was hot battery-->hot hardware-->foam ignition. We just don't have enough information, all too typical for an EAB crash report. I have watched bolts glow red in an otherwise relatively cool firewall, and if it walks like a duck and quacks like a duck...

So, two lessons.

(1) For the umpteenth time, don't put stupid stuff on the cabin side of firewalls, even when properly insulated on the forward side.

(2) Lithium battery runaways can get very hot. The mere fact that the battery is on the opposite side of the firewall, or within a containment box, does not guarantee adjacent objects will remain below ignition temperature.
 
RV8 baggage area

...
(1) For the umpteenth time, don't put stupid stuff on the cabin side of firewalls, even when properly insulated on the forward side.
...
This is a very good point, and something I have not given a lot of thought to. One thing I need to consider is the RV8 forward baggage area - I was assuming I could just toss backpacks or other baggage in the forward baggage area, but I think it would be wise to consider the flammability of anything I put up front, or think about a good layer of insulation.
 
This is a very good point, and something I have not given a lot of thought to. One thing I need to consider is the RV8 forward baggage area - I was assuming I could just toss backpacks or other baggage in the forward baggage area, but I think it would be wise to consider the flammability of anything I put up front, or think about a good layer of insulation.

We can insulate the forward face of course. We can limit or protect steel hardware penetrating the engine-side insulation. However, the real key is that fire (or to be more precise, heat) goes with the air flow, which is significant, in the ballpark of 20-25 cubic feet per second. Highest temperatures will be within the combustion zone (think just downwind of the fuel source), extending to and through the cowl exit, because that is where the vast majority of the air is going. In comparison, the airflow through the cowl-to-fuselage joints is minuscule. I think (opinion) the probability of a really hot upper firewall is low...assuming a builder doesn't bolt a potential heat source like a lithium battery directly to it.
 
Observation

I have read a lot of incident and inflight fire reports where the fire goes either un detected for critical moments (or minutes in the case of several airliners) or un responded to for periods of time that would often have allowed safe landings.

I have to consider that in RV type airframes, an over temperature / fire detection and alert system near the cooing air exit would provide improved odds of a faster reaction and landing.
 
Cabin firewall insulation

After reading through the posts about firewall forward insulation I have decided to go the Fiberfrax/.002 SS direction. In ordering the .002 SS I found that it comes in almost exactly twice as much as I need so.... What about using the extra to to a Fiberfrax(or other people friendly insulator)/.002 SS on the cabin side also?
 
After reading through the posts about firewall forward insulation I have decided to go the Fiberfrax/.002 SS direction. In ordering the .002 SS I found that it comes in almost exactly twice as much as I need so.... What about using the extra to to a Fiberfrax(or other people friendly insulator)/.002 SS on the cabin side also?

There are very few people-friendly insulators (smoke, flame, cancer, etc). Fiberfrax is not people-friendly. Bare stainless is quite safe.
 
Cabin firewall insulation

What comes to mind based on "bare stainless is quite safe" would be to lightly spread stainless wool behind the cabin side covered by the SS foil held in place by SS rivets. The intent is to make a slightly more comfortable cabin while not introducing bad things.

Or

Is this a waste of time and materials?
 
...an over temperature / fire detection and alert system near the cooing air exit would provide improved odds of a faster reaction and landing.
I have one of those. It's a $13 digital meat thermometer with the probe stuck through the firewall. It doesn't have an alarm so would only serve as confirmation of a fire. I also installed a 3/8" aluminum tube "spray bar" in front of the firewall which is plumbed to a fitting on the panel into which my Halon fire extinguisher nozzle fits. I hope I never have to use those things.
 
Koolmat

Does anyone have experience with the Koolmat product for the front side of the firewall. I have seen the installation of Fiberfrax with stainless sheet riveted onto the firewall, but am not a big fan of the pillowing look.

Was curious if anyone had any experience with Koolmat's ease of use for installation. My thought was to adhere it with Firebarrier 2000+ then attach my components to the firewall through the koolmat (except those that need grounding as they would attach directly to the firewall) to help hold it should the firebarrier 2000+ fail to hold it in place.

I would of course do all the other sealing as recommended. This would simply be in addition to everything else like many of you have done. Thoughts?
 
I have one of those. It's a $13 digital meat thermometer with the probe stuck through the firewall. It doesn't have an alarm so would only serve as confirmation of a fire. I also installed a 3/8" aluminum tube "spray bar" in front of the firewall which is plumbed to a fitting on the panel into which my Halon fire extinguisher nozzle fits. I hope I never have to use those things.

IIRC, there have been tests showing that halon in a piston engine cowl can't compete with the hurricane of cooling air, and just blows out the exit. I'd be more prone to save the halon for me. :)
 
Thicker SS?

Does anyone have experience with the Koolmat product for the front side of the firewall. I have seen the installation of Fiberfrax with stainless sheet riveted onto the firewall, but am not a big fan of the pillowing look.

No Koolmat experience but maybe consider using thicker SS. 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. Also a hydraulic punch works great for making nice clean round holes. Ordered everything from McMaster-Carr.
See Photos below

https://lh3.googleusercontent.com/0...N8WQrNNP9vah-5Li-ixC1oM-uWa6gw4c=w800-h450-no

https://lh3.googleusercontent.com/V...FCUYYt9BhvGNgK9RZL808hV9m1EhIfMI=w450-h800-no

https://lh3.googleusercontent.com/Y...f228SuVOh_IJ2FsA5CCrtiIqPJnOxjT=w1608-h904-no

https://lh3.googleusercontent.com/9...XbymSh2SY697_AxtZppYVg__W7ykl3gl=w800-h450-no[/QUOTE]
 
Stupid stuff?

Dan, in post #83 you said "For the umpteenth time, don't put stupid stuff on the cabin side of firewalls, even when properly insulated on the forward side." Would you consider Stewart Systems EkoPrime to be Stupid Stuff if applied to the structural aluminum parts prior to riveting them to the cabin side of the bare stainless steel firewall? (All parts highlighted in the attachment) I plan to use Fiberfrax, SST foil and Fire Barrier 2000+ on the forward side as described in this thread.
 

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Would you consider Stewart Systems EkoPrime to be Stupid Stuff if applied to the structural aluminum parts prior to riveting them to the cabin side of the bare stainless steel firewall?

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.
 
Fire barrier 2000 - Australia

Unfortunately I can’t find any fire barrier 2000 here in Australia. There are other products but it’s hard to know if they are the same or similar based on the test numbers.

Would anyone know of any products similar to fire barrier 2000 here in Australia? (Hard question I know).

@dan what would you say about this product based on the data sheet: Sika 670 Firestop. It looks to be a silicone product, has 4 hours fire resistance to AS1530.4 and has 35% flexibility.

Here is the link to the data sheet: https://aus.sika.com/content/dam/dms/au01/6/sikasil_-670_fire.pdf

It’s a nightmare looking at these standards. The best I could find on AS1530.4 was a graph of the furnace temps - within 5 minutes the test gets to 600c (1100F) - I would hope you are on the ground by then - and the test gets to 1000c (2000f) at about the 90 min mark. So I think this sealant has a similar temp protection? (Maybe?)

No comment on the data sheet of fluid resistance - but it does say it’s a silicone product.

Anyway, I tough generic question I know - but would appreciate any feedback or help. As always, being on the other side of the planet makes finding equivalent products hard.
 

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@dan what would you say about this product based on the data sheet: Sika 670 Firestop.

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.
 
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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.

I believe that burning paint might smell bad but do not believe it is generating any serious amount of toxic fumes. I also agree that it is a small risk as there just isn't any mass of material there.
 
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