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Ti and Fiberfrax Firewall Fireproofing Guide

sritchie

Well Known Member
Hey all,

I'm just about done fireproofing my firewall with titanium foil and fiberfrax -
Dave Paule suggested this method, and it turned out so well that I thought I'd document the process for y'all. Let me know if you'd like more detailed information!

Here's what the final firewall looks like:
NIqNjzAu9YLobPp3MLlQPS_tTl1WZZXyeAW9t0h1lU-Ja619vnR0oT9zVptnguH95uSOEGU84vRoLJ9Qq8yO42r0IXOx9qnVt69qlJkh1XdDv8ldDo-3Avi4hsrKewnWCzw9Rbq2opFMBdo-O90htm6LQt_fz3P2VKqjUIaDDuJOMvauPdQVotytfmQVYoP5o-9dNNriaiq9mz1L_F2fwvuRuQNUL8JXThaQf8yXlnar4K3i8Eu9MVe48TsczuToAhIiqIxkCb18ZNjyVbJtrkv_H0-BU3sUj3y8VXsKIodsYdPVOPbmiSQdklDThte1mJSRHT-8Ux4GPYsiATyQeBnQp1mBf4cWo9HIKPrnD4mIEVbqsrMKrovJyYoW7PcvTr2A65-sN7p6BJIOtUPrz9TIiONBPovsWBDXMTdKiQPfxHdaCZgXTI_Q_hbJnrhxF8ls2HwmUSptuoiRbpUcThzB8TVYeGB8CC_2HlT86ad_O24dYXQ-DeOr8AwzjSE4mv8OxVJqYWM3fICwC4GvEdfEbaIVJhXCkIQEpnTUxvv2wHjTSORqaDXeggoN8mGWrrZko8stIsEoYqk3M3VV3qYnm4Jq34dh02YCwL5l_dxz5_2JYYuBtug7F83lawZOcvjEleiF-_OXcjOFLk_DIRizmuwWUQyL5tg=w721-h541-no


The titanium doesn't crinkle at all, and is great to work with. This method is more tedious than the stainless foil method, but the results are worth it.

Bill of Materials:

You MIGHT be able to get by with 11' or so of foil by laying things out just right. Don't forget the firewall recess. I had to order a bit extra.

The Process
First, decide where you want everything on your firewall to go, add holes and nutplates, yada yada yada.

Then! Take it all off. Cut a big piece of cardboard so it fits onto the firewall inside the flanges. Do NOT cut out holes for anything other than the firewall recess in the center! Just create the big outline.

Next, use this template to lay out strips of fiberfrax. I managed to cover the firewall with two vertical strips of fiberfrax, side by side. I had no overlap between the two pieces of frax... I left a bit of overlap on the cardboard, then once I test-fitted the pieces against the firewall did the final cut to remove all overlap.

Then, lay out the Titanium foil on top of the fiberfrax. I used three horizontal strips, and cut the center strip to have roughly 1" of overlap with the top and bottom pieces. The Ti foil doesn't feel terribly sharp, but it WILL slice you badly if you let it!

Shears work just fine for cutting the Ti. You can use an exacto knife to cut out the firewall recess in the center. I'd recommend cutting out a square a little smaller, as you can use the dremel later to trim it back further.

Gluing on the Frax

First, lay your pieces of fiberfrax on the firewall to make sure they fit, mark any overlap between the two pieces with a sharpie and cut it off.

Next you'll want to clean your firewall off with some acetone.

Once it's dry, use a caulk gun with your Firebarrier 2000+ to lay out drizzles of firebarrier on the firewall. Stick one piece of fiberfrax on! It shouldn't move, it weighs nothing. Drizzle again on the other side and stick it down.

Next, you'll want to use an exacto knife to trim out all the holes for screws, nutplates, etc, anything that will penetrate. To find nutplate holes, get a partner to sit inside the cockpit and push a nail through the fiberfrax while you provide back pressure. Then, come at it from the firewall side with the exacto knife. For bigger holes you can run the blade around the edge of the hole and cut things nicely. For smaller nutplate holes you'll have to tear a little. Use your air hose to blow out any excess.

This is important - completely remove the fiberfrax from around the flanges of the oil cooler mount! I clecoed it on and used an exacto to trace around the edges, then took off the mount and completely removed the frax underneath and around the flanges. You could glue a piece inside here if you wanted; just make sure it doesn't sit under the flanges.

Adding the Ti Foil
Now that the frax is up and holes are all cleared out it's time to add the foil, one strip at a time. I started from the bottom.

Lay down some more firebarrier, this time on the Ti foil piece so you don't tear the frax dragging the caulk gun all over it. (Orient it so that the ends want to curl TOWARD the firewall so they don't lift up immediately!)

Place the Ti foil on the firewall, squish it down onto the frax and use some tape on the bottom edges to make sure it's held down. Run a strip of 3m aluminum tape along the TOP edge, taping the Ti foil directly to the fiberfrax.

Before you do the next strip you'll want to attach everything to the firewall that sits on top of this piece, including the bottom rivets of the oil cooler mount. Do that first.

Cleco the oil cooler mount through the fiberfrax using the top rivet holes. Then, use a #30 drill to match drill through the bottom holes, cleco-ing as you go. Remove the mount and give each hole a twirl with a countersink bit and make sure the hole's clear, then cleco the mount back on for support.

Clearing out the holes

Okay, now it gets sort of tedious! You'll want a partner to sit inside the fuselage with a nail or pop rivet shank or something. One by one, have your partner push the nail through various nutplate holes or larger holes to create a dimple on the front side while you provide back pressure. Mark the dimpled spot with sharpie.

Once you've marked all holes, take the nail from your partner and use a hammer to whack holes in the Ti foil at each sharpie-marked dimple.

Then, push an exacto knife into each hole so you slice across the full hole. On larger holes, like the holes for your heater boxes, you can cut all the way across and remove a good amount of material. On nutplate holes you're just trying to define the hole.

Finally, get out your dremel tool with its cutting bit:
nL_WhpSJ27IRvM_1WqrT9EtxDtwp8Jd88D9SpzcfhS07Z5weDvpXQWhdGnwhRcZMPtrlf4uqP_i3gy4khTrnh-0EEHT5SlBUtec_HwrKqrbEIrlzuoziUIfsEMRiaq3KXzyd8PTue7CXF1-dj6UItNrX2Ip0jj75oF5nhDh6XRMMlelwuFiAnpj93N1J8p6scS6lSE6m2q6DVVWkN0UdTLA9cB0RiuBnHUb4HhtiCUU1LXxoPtOJDOhYxKdCqzeBuvCPgIUe88Cnfsju19SArivG7SDpd6py2Ew7yXGSLDQzLyvwmOGutgplAh3SGQyCNqR3aJ7Sn-UmhC9WltMxakPyy9Uwk5HbQZAf-BfNAKid8Mcch97AYhmwDKTV2_o4DHKaS3SKBp9jWbRNeSs1fsu5rgGvg4FzQ2nwZjOSWVwfwPRGZ4thjJB99-XVcl7Lj9zXJfESHKEm-lwEMh2Hf7qJMG4sN2TMalRbsSDDKGfzIWQ6A2CDzXe50-_37KFkQbFI3cAwIQzjzsB9TfU0_FOi_xjiIbumjjGYzREvS8H9VXuZJ2rVX3ZvfU5LE3e3jpBOk6-oZRNQws3JhgsU9PkTpT--V-MknZ1kHy2_K5VEDPqLS1zo2OghbVce1ddoZBjHUE6B_iTZyJWtB3SNsPVDX_KVQz07Z2s=w406-h541-no


and start cutting away to the perimeter of the hole. With nutplate holes you can do a pretty good job with the tip of the cutter, then go in and clear out the very thin foil with the exacto knife, then go back for a final pass. The results look like this:
fNsKrsqFwuzKF8IaxwHHDy8LKGcN00cla78NfYGeMCZSmmC1s8d7klPMh_XUzXEvIaTrcKhvmGERWOfljGyPzOcckvVQnr5QRMBgvq3_ssP8ANW_7pTryMiQcXc_kagGq-VD7gxJa6OvIWZ08SmiGChZ50U3S5Aj0LjvhgqIYKyG-OHod7_rQJ9_bdVTvp06wm9DJuaQrBr-LHrScPQAcMfgc2kV0rJCElx7Ia4vqI7IbkJPCBoGuaRlgkc6jOLPHWxG2LDtxX5QgQE51R_fJx6x4Qw06WkEXCDc3S3FOg36QhxaiKBiZMk0KWfihci8u3kZxD8bfPDa9KMD1wXCpdUOcrfXSuIo8vT8iKt8EIfZilIiWKCl0-ErNnh06Yc12ey0UkeMGlezcwB91-LkJr4Rxa6KIErG2MaqGIWMSeH3XtxSL9UnQN5APLYe5WQlLO64bqwbXFzlJ5soRTDPCGeV0o6NmLxsw4xPKuRBiDmJb7Mv3J472Q4dI4seD67cokdYZKNW7cPuapq953Kbw5tWQTvsopA26WIBvRqIuVJ3U7WgSV2WJGglmaX9NN8W9XmOa9LJhODuYPZR10QbJ7h43TxRj1BRmFzhIS_Op8TAikdJYHqXH5gqDV257TLXOrNaG2FbgkV4M4MYgYInzU2aCKRXunkJL0A=w406-h541-no


For larger holes, make sure to hold the cutter perpendicular to the edge so the dremel doesn't kick and tear the foil. It's not that fragile so you should be fine!!

Finally, secure the foil by bolting or screwing on any components that below the top inch of this stretch of foil. (That was only the EFII fuel regulator in my case.)

Next Foil Strips

Okay, time for the middle strip. Same drill as before. I recommend an inch of overlap, a strip of aluminum tape along the bottom to join the strip to the bottom strip, and another strip on top to secure this middle strip to the fiberfrax.

DON'T cut out the outline around the heater boxes. You'll want to bolt them through this fiberfrax and Ti sandwich.

Cleco the oil cooler mount on to the new, cleared out bottom holes, and match drill the top holes, clear them out with the countersink and cleco back on.

It's the same drill for the top strip as well! Bolt on firewall components as you go.
 
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Continued...

Firewall Recess
As you can see, I'm not done with the recess Ti yet. I've cut out squares and rectangles of fiberfrax and glued them on with firebarrier. That worked great. My plan with the Ti is to cut out a square for the back - it'll be secured by the throttle, mixture and alt air cable passthroughs - and then for the sides and top, I plan on bending little almost-Z channels. I'll tuck the back end of the foil pieces under that back square, and aluminum tape the outside edge over the middle Ti foil strip. This should be really secure. I'll fill any gaps with firebarrier and call it a day!

Engine Mount Pads
It's important to mount the engine mount directly to the firewall, NOT through the sandwich.

After I mounted all the foil, I put the engine mount on for a test fit, then traced around the pads with a sharpie. I removed the mount and used the tip of the dremel cutting but to trace along the sharpie and cut out the various mount pad shapes. I put the engine mount on again for another test fit, marked what I'd missed, and repeated that a couple of times before the mount was fully clear of the sandwich.

Basically you're thinning out the Ti until you can use an exacto knife to cut through the very thin foil and frax to clear out that section.

Edges
I'll finish up the outer edges with a fillet of firebarrier over the edges of the Ti foil. I'm waiting to do that until I get my camloc flanges mounted and my engine mount installed. Once those are in, I'll tape off the edges and get a fillet down... and that will complete this process!

Pic of the completed firewall once again:
NIqNjzAu9YLobPp3MLlQPS_tTl1WZZXyeAW9t0h1lU-Ja619vnR0oT9zVptnguH95uSOEGU84vRoLJ9Qq8yO42r0IXOx9qnVt69qlJkh1XdDv8ldDo-3Avi4hsrKewnWCzw9Rbq2opFMBdo-O90htm6LQt_fz3P2VKqjUIaDDuJOMvauPdQVotytfmQVYoP5o-9dNNriaiq9mz1L_F2fwvuRuQNUL8JXThaQf8yXlnar4K3i8Eu9MVe48TsczuToAhIiqIxkCb18ZNjyVbJtrkv_H0-BU3sUj3y8VXsKIodsYdPVOPbmiSQdklDThte1mJSRHT-8Ux4GPYsiATyQeBnQp1mBf4cWo9HIKPrnD4mIEVbqsrMKrovJyYoW7PcvTr2A65-sN7p6BJIOtUPrz9TIiONBPovsWBDXMTdKiQPfxHdaCZgXTI_Q_hbJnrhxF8ls2HwmUSptuoiRbpUcThzB8TVYeGB8CC_2HlT86ad_O24dYXQ-DeOr8AwzjSE4mv8OxVJqYWM3fICwC4GvEdfEbaIVJhXCkIQEpnTUxvv2wHjTSORqaDXeggoN8mGWrrZko8stIsEoYqk3M3VV3qYnm4Jq34dh02YCwL5l_dxz5_2JYYuBtug7F83lawZOcvjEleiF-_OXcjOFLk_DIRizmuwWUQyL5tg=w721-h541-no


That's all I've got. Let me know if you find this helpful, or if I can clarify any details of the installation! Hopefully I'll never have to test out whether this thing actually does its job :)
 
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Personal research.....
Can anyone that has done this on an airplane that has now been flying for a while, where the metalized tape was needed to seal joints in the metal overlay, comment on how that held up over time with exposure to engine compartment heat and (in particular) oil exposure (I.E. have you had an instance of a major oil leak and had it not effect the tape... if so please indicate the tape used).
 
Weight savings compared to SS foil? Just curious. Any savings is a plus.

Application notes:

Given fire exposure, the binder in the fiberfrax and some volatile components in the Firebarrier 2000 sealant will outgas. That gas needs an escape path. We want it to go into the engine compartment, where it is harmless.

So, before applying any fiberfrax, be sure the firewall is sealed at the perimeter flange, as well as around any openings, like under the mounting flanges of the heater boxes. No leak paths into the passenger compartment.

Fixating the fiberfrax to the firewall with a few beads of FB2000 is not a bad idea, and convenient for fabrication, but I'd keep it to a minimum, depending instead on mechanical fixation with SS pop rivets through foil, fiberfrax, and firewall. You simply can't depend on sealant to remain highly adhesive when hot.

Now, very important...the desired outgas path is provided by one of the foil overlaps. Those overlaps are sealed with aluminum tape in normal service. We want the tape to melt so the outgas can pass through the overlap, thus at least one section of overlap should be located in an area with a high likelihood of 1100F or more. The likely hot spot is down at the base of the firewall, so the surest bet is a vertical overlap seam right up the center. Horizontal overlaps higher on the firewall may not get hot enough. Is it critical? Maybe not, but the vertical overlap should make it predictable.
 
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The .005 titanium foil weighs about 1/2 ounce MORE than .002 stainless steel foil. But of course it's lighter than thicker stainless steel foils.

I suggested the titanium not for weight savings, but for ease of working it after reading a few stories about how the edges of the stainless steel would cut people's fingers. I bought some of the titanium foil and played with it and thought it was a reasonable alternative in that regard. Sam lives nearby and when I took a look, he showed me some of the cuts he had from the titanium foil, so it's not as benign as I had thought. Still, since it's about eight times stiffer in bending and 2.5 times the thickness, the titanium is probably more controlled and less sharp overall.

The extra bending stiffness gives a smoother look to the firewall, if that is important you you.

Dave
 
I?d be curious how Ti does under Dan H?s burner test. It autoignites at 2200 degrees f and powder or grindings ignite at 480 deg F. http://archpdfs.lps.org/Chemicals/Titanium metal.pdf

I have watched Ti burn in a machine shop where they didn?t observe proper machining processes. Quite interesting and lots of heat. I do know some helicopters that have used Ti for firewalls and it does eventually tended to fatigue from vibration and start cracking.
 
Sec. 23.1191 ? Firewalls.

Sec. 23.1191 — Firewalls.

....some sections omitted....

(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.

(h) The following materials may be used in firewalls or shrouds without being tested as required by this section:

(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.


===========

Not having Dan's pet dragon, I cut a strip of .005 titanium foil and attempted to ignite it using a MAPP fuel torch. I was unsuccessful. I concluded that as a protective layer for the fiberfrax, the .005 foil was satisfactory.

outlsp.jpg


Please note that the stainless steel firewall is still in place on Sam's RV-10.

I'm using some .020 titanium for some firewall-related things on my RV-3B.

Dave
 
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Personal research.....
Can anyone that has done this on an airplane that has now been flying for a while, where the metalized tape was needed to seal joints in the metal overlay, comment on how that held up over time with exposure to engine compartment heat and (in particular) oil exposure (I.E. have you had an instance of a major oil leak and had it not effect the tape... if so please indicate the tape used).

I have 185 hours on mine. I used stainless tape to seal up the stainless foil encasing ceramic fiber. I had a major oil exposure event at about the 60 hour mark - left the dipstick in the hangar :eek: - that resulted in hot oil everywhere including the firewall (quick turn around and land when I noticed oil seeping out the oil filler door on take off). The stainless tape is holding up fine.
 
eh?

So just as a lesson for us poor unwashed non-RV folks, why are you guys doing this exactly? Is it part of your build sequence? Do you not have firewalls as Dave Paule noted ie .015 SS? Or is this something above and beyond the book build?

For the M2 we put sound insulation on the back side of our SS firewall....and ok some annoying heat transfer in the summer months. But not for fireproofing.

Just curious. I learn a lot from you guys by asking the assumed stupid questions.
 
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For the M2 we put sound insulation on the back side of our SS firewall....and ok some annoying heat transfer in the summer months. But not for fireproofing.

You installed fire transfer material.

Search "firewall insulation".
 
You installed fire transfer material.

Search "firewall insulation".

Ah I see. Not book. I dont necessarily agree with your conclusions, but I understand your line of reasoning. Thanks for the clarification.
 
Ah I see. Not book. I dont necessarily agree with your conclusions, but I understand your line of reasoning. Thanks for the clarification.

Try testing it with samples of your products, then you will know. That's what Dan has done with numerous products (and most likely your product) and shared his results with us. Thanks Dan.
 
titanium needs pressure to help it burn. when exposed to normal pressure under the cowl it should not burn.
 
I have 185 hours on mine. I used stainless tape to seal up the stainless foil encasing ceramic fiber. I had a major oil exposure event at about the 60 hour mark - left the dipstick in the hangar :eek: - that resulted in hot oil everywhere including the firewall (quick turn around and land when I noticed oil seeping out the oil filler door on take off). The stainless tape is holding up fine.

Thanks for the info.

Do you recall specifically what stainless tape you used (or the supplier)?
 
Don't really want stainless tape for this application. Melting is desirable to vent the overlap seam.

This makes sense but what about the adhesive? Wouldn't the adhesive "melt" or soften and allow off gassing in either case?
 
Belly fireproofing

What size area would you or did you cover for fireproofing the belly? Specifically:
Wider than the cowl outlet at the front? Full width of belly?
How far back from cowl outlet did you insulate?
Did you keep it the same width front to back, or taper towards the rear?
Thanks.
Johan
 
What size area would you or did you cover for fireproofing the belly? Specifically:
Wider than the cowl outlet at the front? Full width of belly?
How far back from cowl outlet did you insulate?
Did you keep it the same width front to back, or taper towards the rear?
Thanks.
Johan

I did not! I may add this before first flight, but nothing yet.
 
What size area would you or did you cover for fireproofing the belly? Specifically:
Wider than the cowl outlet at the front? Full width of belly?
How far back from cowl outlet did you insulate?
Did you keep it the same width front to back, or taper towards the rear?
Thanks.
Johan

I made a fiberfrax and SS sandwich on the belly of my bird. I used the 1/16" Fiberfrax and 0.010" SS sheet. It came out nicely, with no noticeable pillowing. My belly shield is full width, going back about 20" in the middle and tapering a little further back along the sides. I intend to use 1/8" Fiberfrax and 0.010" SS sheet for the fire wall, secured with SS rivets. The SS sheet is thick enough that it doesn't wrinkle much, so I think my finished product will weather nicely in the engine compartment, although I'm not yet finished with it. Folding the SS sheet to get a nice infill in the recessed box in the firewall is difficult. For that I intend to use a thinner SS sheet (I think it's 0.005"). I will use aluminum tape for a seam, in order to provide a place for venting in a fire event.
 
I made a fiberfrax and SS sandwich on the belly of my bird. I used the 1/16" Fiberfrax and 0.010" SS sheet. It came out nicely, with no noticeable pillowing. My belly shield is full width, going back about 20" in the middle and tapering a little further back along the sides. I intend to use 1/8" Fiberfrax and 0.010" SS sheet for the fire wall, secured with SS rivets. The SS sheet is thick enough that it doesn't wrinkle much, so I think my finished product will weather nicely in the engine compartment, although I'm not yet finished with it. Folding the SS sheet to get a nice infill in the recessed box in the firewall is difficult. For that I intend to use a thinner SS sheet (I think it's 0.005"). I will use aluminum tape for a seam, in order to provide a place for venting in a fire event.

Mike,
Thanks. What I was looking for.
When you say sandwich, did you wrap the fiberfrax between two layers of SS, then attached that to the belly, or is it belly skin, fiberfrax covered by SS? If it is the latter, how did you manage the sharp edges of the SS foil?
What method of attachment did you use?
I have not worked with 0.010" SS foil (my firewall was done with 0.002) and wonder how easy it is to work with the 0.010", like bending, folding on itself, cutting and making holes. I was contemplating using 0.005" on the belly but will go with 0.010" if it is easy to work with.
Thanks for your response.
Johan
 
I made a fiberfrax and SS sandwich on the belly of my bird. I used the 1/16" Fiberfrax and 0.010" SS sheet. It came out nicely, with no noticeable pillowing. My belly shield is full width, going back about 20" in the middle and tapering a little further back along the sides. I intend to use 1/8" Fiberfrax and 0.010" SS sheet for the fire wall, secured with SS rivets. The SS sheet is thick enough that it doesn't wrinkle much, so I think my finished product will weather nicely in the engine compartment, although I'm not yet finished with it. Folding the SS sheet to get a nice infill in the recessed box in the firewall is difficult. For that I intend to use a thinner SS sheet (I think it's 0.005"). I will use aluminum tape for a seam, in order to provide a place for venting in a fire event.


Mike,
I looked for pictures of your install on your builder's site, but could not find the belly fireproofing. Could you point me in the right direction please.
Thanks.
Johan
 
I made a fiberfrax and SS sandwich on the belly of my bird. I used the 1/16" Fiberfrax and 0.010" SS sheet. It came out nicely, with no noticeable pillowing. My belly shield is full width, going back about 20" in the middle and tapering a little further back along the sides. I intend to use 1/8" Fiberfrax and 0.010" SS sheet for the fire wall, secured with SS rivets. The SS sheet is thick enough that it doesn't wrinkle much, so I think my finished product will weather nicely in the engine compartment, although I'm not yet finished with it. Folding the SS sheet to get a nice infill in the recessed box in the firewall is difficult. For that I intend to use a thinner SS sheet (I think it's 0.005"). I will use aluminum tape for a seam, in order to provide a place for venting in a fire event.
Mike,
Do you remember where you got your .01" SS foil? My search on internet was not fruitful for a wide piece that can be used on the FW.
 
Sorry I've been away for a while. Work gets in the way! ;)
My belly shield consists of 1/16" FFrax against the belly skin (aluminum) with a 0.010" SS sheet over that, riveted to the structure. The O.010" SS sheet was easy to work with and allowed me to break the edges, so that when everything was riveted in place the edges of the SS stayed tight, without lifting up. The FFrax compresses a bit during riveting, but overall the pillowing is not very evident in the finished structure (probably also due to the thicker SS sheet). Below are some links to the VAF post where I list where I got the SS sheet and also to my weblog, which hasn't been updated in months, but shows the finished belly shield.

http://www.vansairforce.com/community/showthread.php?t=128497&highlight=sheet&page=2

http://www.mykitlog.com/users/display_log.php?user=mikrettig&project=803&category=10711&log=222385&row=80

I will do 1/8" FFrax on the firewall, similar to what Dan Horton has recommended. My SS sheet will be held in place there using SS rivets, symmetrically spaced across the firewall.
 
Dan,
I'm curious about your post. Sounds like you have put a lot of thought into this and I'd like to try and follow you in it. I'm curious too about your heating experimentation in these regards.

It seems there are some assumptions that I haven't been able to come to yet and need some help on.

You mention ensuring that the firewall is sealed so there are no leak paths to the cockpit. You say that the fiberfrax and binders forward of the firewall need to have an escape path for the gases from those binders burning.
You suggest providing a path forward of the firewall by providing seams in the foil with overlay tape that melts away so the gas will go forward away from the firewall.

Since the firewall was made impervious to leaks why not make the fiberfrax protective foil impervious as well? Why assume that once the seam tape is gone that the gas will go forward? Seems that the pressure would still be higher in the engine compartment and that once the tape melts a path would be open for the fire to work against the fiberfrax perhaps ignite those gases and then work against the firewall that we are trying to protect. Wouldn't it be better to let whatever gases build in the sandwich find a path out at the edges? Just thinking out loud and wanting to understand why not make the foil totally sealed just like the firewall? Thanks

Weight savings compared to SS foil? Just curious. Any savings is a plus.

Application notes:

Given fire exposure, the binder in the fiberfrax and some volatile components in the Firebarrier 2000 sealant will outgas. That gas needs an escape path. We want it to go into the engine compartment, where it is harmless.

So, before applying any fiberfrax, be sure the firewall is sealed at the perimeter flange, as well as around any openings, like under the mounting flanges of the heater boxes. No leak paths into the passenger compartment.

Fixating the fiberfrax to the firewall with a few beads of FB2000 is not a bad idea, and convenient for fabrication, but I'd keep it to a minimum, depending instead on mechanical fixation with SS pop rivets through foil, fiberfrax, and firewall. You simply can't depend on sealant to remain highly adhesive when hot.

Now, very important...the desired outgas path is provided by one of the foil overlaps. Those overlaps are sealed with aluminum tape in normal service. We want the tape to melt so the outgas can pass through the overlap, thus at least one section of overlap should be located in an area with a high likelihood of 1100F or more. The likely hot spot is down at the base of the firewall, so the surest bet is a vertical overlap seam right up the center. Horizontal overlaps higher on the firewall may not get hot enough. Is it critical? Maybe not, but the vertical overlap should make it predictable.
 
I guess there are as many ways to install a stainless firewall shield with Fiberfrax as there are folks doing it, this is our rendition. We used .010? hard for the bottom and firewall and .010? soft for the oil filter recess. The extra thickness adds a little weight, but it is nearly impossible to drill a round hole in anything much thinner. Using a hole saw in the thin material is also very problematic. We used .062? frax on the belly and .125? on the firewall. While it certainly gives one a warm fizzy feeling knowing it?s up there in the very unlikely event of an engine fire we were more interested in sound deadening and cabin temperature considerations.

I think we followed all the good advice previously posted to this thread with some enhanced fabrication techniques mostly for aesthetics to an area that nobody will see. I apologize for the belly picture, I forgot to take a picture before we took it off the rotisserie.


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Very professional looking. Sure beats my 2 thou foil wrinkle look. That said, the 5 thou titaniumgoat sheet on the belly came out pretty well, but I was only putting it over 1/16" frax.

Tom.
 
That looks good. I am currently doing the same on my RV-7. From the pictures it looks like some attachment points are recessed. They look like micro cupcake forms. What is the purpose for those? Did you make them yourself ?
 
I made the offset washers from the soft .010 SS, with a simple press die with a center alignment pin. The pictures pretty well explains the process. I squeeze the die in a bench vise to form the washer. I used 1/8? Fiberfrax and I knew I would get a lot of pillowing if I didn?t do something like this. I glued the frax to the .010? SS with water diluted Elmer?s glue sprayed on with a pump bottle.


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Pattern for rivets and belly fire protection on RV-10

I am planning on putting a sandwich of either Titanium or SS and Fiberfrax on the belly of my RV-10. I have a QB fuselage so the skins are already riveted on. The forward floor ribs of the RV-10 angle out as opposed to straight back. Does the sandwich need to be riveted to the doubled structure of the skin and the floor rib or can I just make a rectangular sandwich and capture it by just riveting through the skin? If I do the later, I would obviously try to capture as many ribs as possible.

If it is recommended not to rivet just to the skin, the shape of the sandwich will be a trapezoid and the seam running front to back will be exposed a bit to the slipstream. Might that cause any potential problems in peel-back?

I am about to put the floorboards in and it would be much easier to put the sandwich in now while I have access to the floor ribs and can easily drill through them.

I will probably go just 18 inches back from the firewall which would cover the fuel pump. According to pictures and accounts of an actual RV-10 fuel fire, the fire damage did not extend that far back.

Thank you in advance for any feedback.
 
On all of my belly fasteners that went through the Fiberfrax, I made small .063 aluminum spacers. That way I had a solid Ti-al-al connection all the way through. With the Fiberfrax laid on top, it was easy to locate these spacers, and using an Xacto knife, cut out the Fiberfrax to clear them.

This is on my RV-3B, using 1/16"Fiberfrax and .020 Titanium for the belly overlay. The airframe itself has the original belly skin there per the plans.

On the Ti edges, I stopped the Fiberfrax maybe 1/2" short of the rivet line and riveted the Ti directly to the aluminum belly. Worked out very nicely.

Dave
 
Michael, offhand I can't think of any reason why the overlay can't be riveted to the belly skin only. Others have done so, for what it's worth. Through the rib flanges is good too. You'll be using a sealant under the edges, so they are effectively glued with no way for the slipstream to raise them.
 
Lets make it easy then

Based on the 2 comments, I will use a simple rectangular sandwich starting at the firewall and trailing back. This will require just fastening the sandwich to the belly skin and possibly a few floor ribs.

Thank You
 
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