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Firewall Protection

My idea (using the good stuff) would be to pack the empty space with the cured fingers of firestop, then use firesleeve clamped over the outside of the pass-through & wire bundle for CO block.
The idea is that as long as there's no fire, there's no mess; if there is a fire, the fingers will swell up & fill whatever airspace was left in the pass-through.

Sounds good to me.

Is there a downside to using a piece of firesleeve with some trimmed out lengthwise then wrapped around the wires and slid inside the tube? Similar to how the commercially available stainless pass-throughs recommend. You can then firebarrier the exposed end. Firesleeve that is manufactured to the FAA TSO can withstand 2200 deg F for 15min.

As you say, that's the principle in commercial building pass-throughs (pack with with inert fiber or similar, then seal the ends). Should work fine.

I'll toss out another approach too. Pull the wire bundle out an inch or two, wrap it tightly in aluminum tape, then push it back in so the aluminum tape is inside the sleeve. Now inject Firebarrier into the remaining space. The tape will keep it from gluing all the wires together, which is the only real PITA if you ever need to rework the harness.
 
I thought the purpose of intumescent caulk in construction is to not only fill the gaps, but to expand into any space left by melting/burning wire insulation (& even wire) so the hole stays filled. That's why I was looking for a less messy way to use the caulk, instead of fire resistant fiber of some sort.

Charlie
 
I thought the purpose of intumescent caulk in construction is to not only fill the gaps, but to expand into any space left by melting/burning wire insulation (& even wire) so the hole stays filled. That's why I was looking for a less messy way to use the caulk, instead of fire resistant fiber of some sort.

Charlie

That is correct.
 
I thought the purpose of intumescent caulk in construction is to not only fill the gaps, but to expand into any space left by melting/burning wire insulation (& even wire) so the hole stays filled. That's why I was looking for a less messy way to use the caulk, instead of fire resistant fiber of some sort. Charlie

Ummm, so did I ;)
 
After krwalsh flagged titanium as being flammable in post #50 above, I tried it. First, though, I looked it up and found that particles and tiny strands of titanium are indeed flammable. As the thickness increases, the flammability apparently drops. I found no reports of sheets of titanium burning.

I cut a slice of .020 titanium foil to a width of roughly 5/32 inch. I put my MAPP torch in the driveway and focused the flame on the very end of the strip.

316t4q9.jpg


If that image disappears, try here.

Since it was daytime and the flame was hard to see, the end sometimes moved out of the flame. I was able to keep it in the flame for about 30 seconds at a time. This photo shows the brightest and most interesting result of the MAPP flame.

At no time did the titanium itself ignite. I touched the strip close to the pliers and it was cool to the touch; titanium doesn't conduct heat well.

Worth mentioning is that I dropped the hot end in a bit of snow and nothing happened except some sizzles.

Later, I went back and tried to ignite a strip of the .005 foil. I was unsuccessful and could not get it to ignite. I could get it orange/yellow hot and that was about it.

outlsp.jpg


Or here.

This was a thin strip of .005 titanium, heated on the very end. I'm satisfied that it's acceptable, as the FAR says, for use as a firewall in the thickness specified in the F.A.R.


Dave
 
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The more I look at my aluminum brake reservoir and the gaping hole in the firewall where the npt fitting attaches, the more I think I should just make a reservoir out of stainless tube with a plate on the back to rivet to the firewall and cover up the space around the hole. Not only would it cover the gap but it would not melt in a fire and supply more fuel.

Anyone see a downside?
 
The more I look at my aluminum brake reservoir and the gaping hole in the firewall where the npt fitting attaches, the more I think I should just make a reservoir out of stainless tube with a plate on the back to rivet to the firewall and cover up the space around the hole. Not only would it cover the gap but it would not melt in a fire and supply more fuel.

Anyone see a downside?

Is it already installed? I dealt with that problem by removing the external reservoir(integrated into the master cyls), others moved it inside the plane off of the firewall.
 
I am looking for a source of the stainless foil in Canada. The McMaster Carr part number is 3254K16. I do not see it on the Aircraft Spruce website.

Thanks in advance!
 
After krwalsh flagged titanium as being flammable in post #50 above, I tried it. First, though, I looked it up and found that particles and tiny strands of titanium are indeed flammable. As the thickness increases, the flammability apparently drops. I found no reports of sheets of titanium burning.

I cut a slice of .020 titanium foil to a width of roughly 5/32 inch. I put my MAPP torch in the driveway and focused the flame on the very end of the strip.

316t4q9.jpg


If that image disappears, try here.

Since it was daytime and the flame was hard to see, the end sometimes moved out of the flame. I was able to keep it in the flame for about 30 seconds at a time. This photo shows the brightest and most interesting result of the MAPP flame.

At no time did the titanium itself ignite. I touched the strip close to the pliers and it was cool to the touch; titanium doesn't conduct heat well.

Worth mentioning is that I dropped the hot end in a bit of snow and nothing happened except some sizzles.

Later, I went back and tried to ignite a strip of the .005 foil. I was unsuccessful and could not get it to ignite. I could get it orange/yellow hot and that was about it.

outlsp.jpg


Or here.

This was a thin strip of .005 titanium, heated on the very end. I'm satisfied that it's acceptable, as the FAR says, for use as a firewall in the thickness specified in the F.A.R.


Dave

titanium needs pressure to make it burn. like the inside of a compressor.
 
Thanks to Dan's info and diagram and Dorfie's experience posted here, I was able to insulate my firewall over a long weekend. Total cost was under $100. Total weight is a pound or less. I didn't do it because of fire paranoia... I did it because I've been flying almost exclusively in composite Jabiru-powered aircraft for the past 8 years and I'm used to flying in comfort. The Jab runs about 100 degrees cooler than a Lycoming in both CHT and EGT. The firewall on our aircraft is a sandwich of stainless steel, ceramic felt, plywood, and padded carpet that extends to the entire fuselage. Cabin temperature is never a problem. When DanH says he can fly his RV-8 in sock feet, well, that's what I'm going for here! The added layer of fire safety makes it a no brainer.

The stainless foil (.002" thick, 24" by 10-foot roll), stainless rivets and rivet washers are from McMaster Carr. The FiberFrax and 3M FireBarrier 2000+ is from Aircraft Spruce. I used 1/16" thick FF on the belly and 1/8" FF on the firewall. I started with the belly and made posterboard patterns first. All edges are folded around the Fiberfrax when possible. The front side overlaps the belly and is secured by screws for the battery box, rivets and aluminum tape. I didn't use a whole lot of rivets on the belly because my belly skin is also my floorboard, so I didn't want a bunch of rivet tails sticking up where my feet go. I was able to use the screws that hold the removable battery box for several anchor points.

If I were to do it again, I think I'd use a thicker sheet for the belly pan similar to what Dan did. Mine is sort of wrinkly. I hope it holds up over time. We shall see!

By the way, the steel conduit fittings in the firewall are for my wiring bundles. They will be lined with firesleeve and caulked with the 3M Firebarrier. I still need to drill out some stainless large area washers to go around them for support. Cost? 64 cents each at Lowes. :cool: You should've seen the guy's face at Lowes when I walked up and asked him how to tell what these fittings are made of, because I wanted steel, not zinc, because zinc melts at a low temperature. He just looked at me like, "What planet are YOU from?" Turns out the steel ones say STEEL on the bag label. (He didn't know that, though!)

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Katie,
How did you get the holes for the pull rivets through the SS foil?
Thanks.
Johan
 
Katie,

The vents are fine. No, they should not lead fire to the tank.

Since you have it down this far, take the opportunity to add a stainless overlay with a curved leading edge wrapping up and around that bottom cross tube. The result would look like an RV-8.



Dan,
What thickness SS did you use for this application?
Thanks.
Johan
 
McMaster Car version of FiberFrax?

Anybody had any experience with this McMaster Ceramic fiber as a replacement for FiberFrax? Seems to be about 1/2 cost than Aircraft spruce?

YBs995gNAq8v2HPVKu8k4ADEaHFFOtYXzzBqwY3huGhqxeqA2SEAq-041riTdd88YrX9-TvOIrKQeXsF1yVuelaLILbcWbLf0UCHKBmWEZOw9hOacxwhNPuYL3s-bZpV72Xno7CT_iOvnqMmxU9CY8GyEQfRDa8ZVcBTtLkDubHa5FEssW_YDoNRSUPrjx-qK1OUQ0UzZcmYTUvGm22a0Cq_iViQZbTlq1IWuBjVcUUWS9we2Mr_A19eEPmgF1IQ1Iw3flLCwsh2VWLdm2f7EMGDzCkzsv6PB90WiNKOzWecgczy2luRmTfeKUqGX5QtxunYG5Ky5hCXivrRKSZORVAMOfEpr4QUbIrnQm3hS6tzF2etE_BSFenc9lb-mD37AVlLCBOosBVSdEJjXQyu5uhCoH6gBnktN6xhd8Uvk_ysLeAyNJXTOZwvYpmH0U_tj0vpp_uSjKwymlSR9dXrCMwOwCokq5sdVrHEAVMzhx-NVpQZ3SiCPBtD-QDTwR7h9Zcv-GEScQcFTeVzYbUjPz7z4_juyzqLbvlMpZKLBPlVBd-BwXfq-ibVToiPVBiowbj2H8ohASxQ1xsVJcALoAxu6cEb0Ks-W7v6shdY3srIegL9YSVY=w856-h294-no


I am seeing people using .002 stainless for the barrier in front of the Ceramic mat, is .002 thick enough? I am planning on using this both on firewall and under the bottom front floor on RV10 but am unsure if the aesthetics of .002 will be too wavy or should I look for .005 in his location.
 
I just finished my firewall, and I found 0.002" stainless to be quite adequate. It is thick enough to be durable, but thin enough that you can still punch holes through it with a scalpel if you need to add passthroughs. I secured the stainless to the firewall using a variety of stainless fasteners, but found the best solution was using a countersunk 3/32 stainless rivet (CCC32 if I remember correctly) and putting a dimpled 1/8" thin stainless washer under that (because I couldn't source large OD stainless washers with a 3/32" ID). I know it sounds a little odd, but I dimpled the 1/8" washer with a 3/32" dimple die, as this gave the best result. The use of the washer creates a larger contact patch with the foil, and covers any small tears that may have occurred when you drilled it. The use of a countersunk washer without dimpling the sub structure (firewall) creates a space between the stainless foil and the firewall. This space is for insulation so you don't get as much pillowing. For the belly I used 0.005" titanium and I'm glad I did as it gives much more of a ripple free surface. This was over the top of 1/16" frax, which was held in place with AN426AD3 rivets around the perimeter and MK319BS rivets through the middle. The perimeter was sealed with Sikaflex Pro to stop moisture egress, as were the AN426AD3 rivets (which were then cleaned off on the inside of the cockpit to ensure no Sikaflex residue remained). The middle rows of MK319BS were wet set using 3M Firebarrier 2000+. For the firewall, I used a biosoluble insulation called Morgan Superwool HT paper. Because the firewall may be penetrated later for additional passthroughs, I wanted to use a biosoluble product rather than traditional Fiberfrax. I wanted 2mm instead of the standard 3mm (or 1/8") to limit pillowing that I have seen on other projects but couldn't source it locally, so I went with 1mm. It still doesn't look as good as the belly, but the pillowing is not too bad. If I was to do things again I would probably try harder to find some 2mm. The downside to this biosoluble product is that it is more delicate to work with than the regular fiberfrax as it has a lower tensile strength and it's temperature is only rated to a 2500degF melting point however this still exceeds the temperature requirements of the FAA test and the melting point is the same as the stainless steel that is encasing it. Morgan is just one of a number of manufacturers of these biosoluble insulation papers. I hope this helps.
Tom.
opU.jpg

2dba42h.jpg

2q8qzrs.jpg
 
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Anybody had any experience with this McMaster Ceramic fiber as a replacement for FiberFrax? .

I have used the McMaster parts:

SS sheet 0.005" thick

Firewall Insulation

Belly Insulation

The firewall insulation is basically loose "batting" insulation and has little or not binder that could outgas when heated. The downside is that it does not want to lay as flat which makes the overlaying foil more prone to "pillowing".
additionally I used 1/4" thick on the firewall when 1/8" would probably be adequate.
 
Tom - Thanks for the hints on how to attach using the washers, great idea. I use your website at times, I think you are making progress much faster than me. PS my wife & I were remember her trip with my son to Tasmania last year, they greatly enjoyed coming out to your farm....she also reminds me how much better organized your shop is compared to mine....

Weasel - Thanks for the McMaster links for the insulation. The one you used although thicker is about 1/2 price of the one I as looking at, thanks!


Steve
 
Another question... what would be a good length/width for a belly skin fire shield for an RV-7? I'm at the deburr/dimple stage on that skin and I figure it might be a good idea to go ahead and do all the prep for that part now...
 
Another question... what would be a good length/width for a belly skin fire shield for an RV-7? I'm at the deburr/dimple stage on that skin and I figure it might be a good idea to go ahead and do all the prep for that part now...

No one really knows for sure. Anecdotal accounts, at least one NTSB report, and one direct report here by an owner suggest that (1) the flame follows airflow out the cowl exit, and (2) belly skin melt area is pretty close to the firewall.

Most seem to be using 24" long as a sensible guess.
 
Has anybody tried the fire protective paint that Aircraft Extras (Vans Airforce Advertiser) has on their link. This type of product has been used successfully in certain types of building construction in regards to prolonged structural integrity in fire situations. If it reacts as advertised, it would be much simpler. Just a thought.
 
No one really knows for sure. Anecdotal accounts, at least one NTSB report, and one direct report here by an owner suggest that (1) the flame follows airflow out the cowl exit, and (2) belly skin melt area is pretty close to the firewall.

Most seem to be using 24" long as a sensible guess.

That's a usable figure.

What about the width? Or perhaps more specifically, anyone know the width of the cooling exit on a stock RV-7 cowl? I'll probably wind up modding mine with a cowl flap but I don't see the width changing...
 
Has anybody tried the fire protective paint that Aircraft Extras (Vans Airforce Advertiser) has on their link.t.

Search "Contego" (IIRC) for an intumescent paint test.

I very much doubt the protective char will stay in place given flight conditions. Remember, a building interior doesn't have a 100 knot wind.
 
The RV-7 outlet is 12.5in wide. My titanium belly skin is cut to 13.5in wide. It is available from titanium goat in 14in width.
Tom.
 
How About the Things Going Through the Firewall?

I'll be using 1/8" Fiberfrax and .005 titanium foil over that.

What's the best practice about installing fasteners and fittings that go through the firewall? Should I make a spacer the thickness of the Fiberfrax for that local region? And if so, can I use aluminum or must it be stainless or titanium?

Dave
RV-3B, still entertaining me with a fun construction project
 
What's the best practice about installing fasteners and fittings that go through the firewall? Should I make a spacer the thickness of the Fiberfrax for that local region? And if so, can I use aluminum or must it be stainless or titanium?

<SNIP> as I have the same question. Hoping to hang my engine in the next couple weeks so I can start fitting things to the firewall. I'm going to have a lot going on there (dual electrical, EFI) and bolting through a soft layer doesn't strike me as good practice. My thought is to cut holes and/or use spacers and seal all the gaps.
 
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There are a great many potential insulators....cork to Aerogel, and everywhere in between.

The primary advantages of the common Fiberfrax felt product are availability from the usual aircraft supply sources, and ease of use. Placed on the forward side of the firewall, out-gassing of a binder (the glue binding the fibers together) is inconsequential, although it is best to provide a vent path.
 
Does the brand of aluminum tape matter? I have some harbor freight laying around and just tested it in my powder coating toaster oven. I had it in for about 10 to 15 minutes at 450 just to see what would happen. No flames but it did smoke and the adhesive gave out. Then put a flame to another piece. It caught on fire pretty quickly but then went out just as fast. I think it was the adhesive that burned for a bit. Is this a common occurrence or what should be expected with aluminum tape?
 
Expected. And perfectly okay.

The tape is a seal during normal operation. It will melt almost immediately if subjected to a typical engine compartment fire. When installed to cover a vertical seam between stainless steel foil sheets, it will allow outgassing into the engine compartment after melting.... Exactly what we wanted to do.
 
Expected. And perfectly okay.

The tape is a seal during normal operation. It will melt almost immediately if subjected to a typical engine compartment fire. When installed to cover a vertical seam between stainless steel foil sheets, it will allow outgassing into the engine compartment after melting.... Exactly what we wanted to do.

Thank you! Now i may proceed!!!!
 
Here is my firewall mostly completed. A few things left to do but finally happy with the progress I've made. I also put titanium foil on the bottom of the fuse just aft of the cowling for more fire protection. I powder coated the battery box, pass throughs, fuel/oil pressure manifold and the oil cooler brackets.
20200429-171240.jpg
 
Aft of the firewall on the belly, you'd want something thicker than foil since it is a primary firewall there.

I used .020 Titanium. Taken from FAR Part 23.1191, here are some acceptable materials for certified airplanes:

(1) Stainless steel sheet, 0.015 inch thick.

(2) Mild steel sheet (coated with aluminum or otherwise protected against corrosion) 0.018 inch thick.

(3) Terne plate, 0.018 inch thick.

(4) Monel metal, 0.018 inch thick.

(5) Steel or copper base alloy firewall fittings.

(6) Titanium sheet, 0.016 inch thick.

Dave
 
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I enjoy the ingenuity and research builders do. Personally my thought is the
fiberglass cowl will not last long with a full blown fuel fed fire even if the firewall
has extra protection. The benefit of firewall insulation is less heat and noise
into cockpit. Fire? I think stock stainless firewall is sufficient with that in mind.
A fire would be a nightmare. Have the best fuel lines under the cowl for sure.
Oil fires and catastrophic engine failures are also risks.
 
I’m quickly getting to the point where I’ll be making lots of FWF decisions and poking holes in the firewall of my RV-8. I bought it as an unfinished project, and the previous builder painted the inside of the fuselage, including the firewall..

I plan on insulating the engine side of the firewall (already have the Fiberfrax - just need the foil), but need to deal with the paint. Any suggestions on how to remove paint from the inside of a SS firewall? I can’t imagine that the fiberfrax/foil combo would keep it cool enough to ignore this in a fire situation.
 
For insulation/foil, what do you do about the recess? I've seen a couple firewalls completely cover over this but doesn't that defeat the purpose of the recess? I was thinking about following the contour with the insulation/foil and sealing the inside edges and foil taping the outside edges.

Thoughts??
 
This is my take on the firewall protection issue...

My intent is to offer an extra 10 minutes protection from a fuel fire in the cowl while gliding to a ditching. If the structure can stay intact and the crew isn't smoked out for that long, you might have a chance.

The firewall, including the prop gov cutout and heater air valve structure are covered, and all edges are sealed with high temp RTV. The blanket will stay in place on it's own, and where needed, I fastened in through the FW with stainless big head pull rivets.

The silvery material is an aramid fiber with a mylar coating, rated to 1800F, and the sublayer is two plys of silicone impregnated fiberglass. Pretty much what a fire suit is made of... Both are manufactured by Newtex (Z-Flex and Z-Block).

Stitched it all together with Nomex thread.

And just to quell another fire before it starts, the engine mount does not sandwich the blanket against the FW.
 

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1 or 2 tubes of 3M?

I’m just getting ready to apply my SS sheet. How many tubes / cartridges are needed? I don’t want to get 90% done and run out of 3M 2000+

Thanks!
 
Allen,

My firewall is not done yet but I did the recess in sections. First I cut the fiberfrax for all of the surfaces and it is held in place by the 3M fire barrier 2000. Then I cut pieces for the sides which had flanges to slide under the other pieces. I made templates for all of the pieces first, test fit them and then cut the foil. Nothing exotic is required to do the bends of the foil. I just clamped a piece of angle to my workbench and used a piece of scrap wood to make the bend. I did the same for the lower aft section. For the sloped section of the recess I simply cut the main piece along the recess and then made a bend for the sloping section. This part isn't totally complete yet, but here are some pics to show some of the steps.

Also for the attachment I used enclosed stainless blind rivets that I got from McMaster. The foil is a little difficult to deal with since it isn't very rigid so it tends to flop all over until it is secured in some manner.
 

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Hi Tim,

I used 2/3rd of a cartridge when I did the firewall and belly insulation in my RV-7. If you're needing any more than that you're probably making your filets a little on the large side, and you've got to carry this weight around for the rest of the life of the aircraft.

Tom.
 
Thanks!

Thanks a lot to all in this post and Dan for testing. I think I added something useful which also does no harm. Very light weight. The firewall recess was a pain. A flat firewall would’ve been much easier and less bloody. I made a card stock templet and filled the recess with folded origami SS sheet. It worked very well. I have much respect for those doing this without removing the engine/mount! I could’ve gone lighter & neater on the 3M if I had an extra hand. But is ok.
 

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