Retrofitting firewall thermal insulation

I am building a RV-7A. I'm reading that firewall insulation is important for comfort.

All the threads I've been seeing recommend fiberfrax covered by metal foil on the front side of the firewall. I've unfortunately have already mounted the engine and plumbed it up enough that I'm reluctant to disassemble, making it difficult to put insulation on the front side.

I've also read that fiberfrax may not be safe for the interior cockpit environment, and that other sound-insulating materials could ignite and bring a fire into the cockpit.

Has anyone else found satisfactory thermal insulation for the firewall interior? Or if you built to plans and didn't insulate the firewall at all, are you satisfied, or regretful?

David

Perhaps Im reading too much into your words, but I wouldnt characterize the installation of exterior firewall insulation as being for comfort. If by "comfort" you mean having a chance at living through the unlikely event of an engine fire, then ok, yes.

As has been well demonstrated in tests documented on this forum, iinterior insulation does more harm than good with respect to fire protection. Probably better to go without rather than to use it. Your call on post-enging hanging exterior insulation installation. Most folks dont have exterior insulation and in-flight fires are quite rare. But if it did happen...

erich

You might be interested to know I un-hung my own engine and mount to install engine-side insulation, after testing showed there was no cabin-side approach nearly as good.

Might I add that I don't care if anyone does or does not insulate. Thousands of RV's with bare firewalls make their owners happy. Just stop placing stupid stuff on the cabin side.

I removed my engine to do the firewall insulation/ fire barrier following Dan Hortons documentation I found on the forum. The insulation and SS fire barrier was more labor intensive than the removal and reinstallation of the engine and mount.

DanH said:

Just stop placing stupid stuff on the cabin side.

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And yet a couple of ?experts? seem to have done just that.

http://www.vansairforce.com/community/showthread.php?t=27253&highlight=Firewall

Makes it a little bit difficult for us novices to decide an appropriate method. Your testing, however, does provide some data versus none at all.

Fwd side heat/noise option

Kool Mat sells a product called ?Zero Clearance?. Peel ?n stick sort of stuff - VERY aggressive glue. I was able to cover at least 80% of my firewall (engine attached - ugh) by piecing in around the penetrations and attachment areas. Be sure to get some of their tape - same glue, which means it won?t move once it is placed. Seal the edge with Permatex Ultra Black.

Installation is much easier with the engine on the hoist!

This same product is what I also covered my cowling inside. I also sealed the perimeter with Permatex Ultra Black. Cut carefully so no wrinkles are present so the edge lays down easily.

https://www.koolmat.com/heat-resistant-products/foil-heat-products-protection/

KatanaPilot said:

And yet a couple of “experts” seem to have done just that.

http://www.vansairforce.com/community/showthread.php?t=27253&highlight=Firewall

Makes it a little bit difficult for us novices to decide an appropriate method. Your testing, however, does provide some data versus none at all.

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Krea, those posts date from early 2008. Back then we all assumed gluing rubber and plastic to the cabin side of a firewall was a safe practice. I'm including myself, as I recall at least one airplane leaving my shop with what was probably Thermozite on the firewall.

Everything is fine until it's not. Back in the 70's, most of us drove drunk and ignored safe sex practices. People died, we shrugged. Now we do a forehead slap and say "What was I thinking?"

I should probably get the burn rig out of the attic and bring it over to Synergy, or Falcon Field. Seeing is believing.

BTW, experts die too. Remember Vern Dallman?

https://app.ntsb.gov/pdfgenerator/R...tID=20001211X11589&AKey=1&RType=HTML&IType=LA

http://lincolnbeachey.com/vern.html

Thank you all, and especially Dan for everything you've posted here.

This clarifies the issues and process.

David

F1Boss said:

Kool Mat sells a product called ‘Zero Clearance’. Peel ‘n stick sort of stuff - VERY aggressive glue. I was able to cover at least 80% of my firewall (engine attached - ugh) by piecing in around the penetrations and attachment areas. Be sure to get some of their tape - same glue, which means it won’t move once it is placed. Seal the edge with Permatex Ultra Black.

Installation is much easier with the engine on the hoist!

This same product is what I also covered my cowling inside. I also sealed the perimeter with Permatex Ultra Black. Cut carefully so no wrinkles are present so the edge lays down easily.

https://www.koolmat.com/heat-resistant-products/foil-heat-products-protection/

Click to expand...

Mark, Mark, Mark... yer killing me Smalls. Blake sells this stuff, probably for less than most anywhere else.

https://www.flyboyaccessories.com/Heat-and-Sound-s/7.htm

We used to carry some products for the inside of the firewall, but Dan Horton's burn rig showed that it wasn't the best idea. However, the foil faced, sticky, fiberglass (or other material) on the engine side has worked quite well for me. It was on my previous Rocket and held up great and certainly helped with the "hot feet" problem.

Each aircraft is different, but adding stuff like is shown above should be relatively cheap and easy. Use foil tape along seams, or over "boo-boos", then seal the edges down with ProSeal (from a baggie with a clipped corner) and you'll have a neat, tidy, life-time installation.

I hate to argue with Mark, but ProSeal is a MUCH better edge sealer than Permatex. Oil or fuel will eventually soften any silicone RTV sealant. It may be "resistant" to oil/fuel, but the "black death" just laughs at oil/fuel.

Vince

vfrazier said:

I hate to argue with Mark, but ProSeal is a MUCH better edge sealer than Permatex. Oil or fuel will eventually soften any silicone RTV sealant. It may be "resistant" to oil/fuel, but the "black death" just laughs at oil/fuel.

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Obviously polysulfide is a good sealer. That said, Permatex Ultra Black (aka Loctite 598) has proven to be very oil resistant. Recall quite a few of us have been making silicone/glass cylinder wraps with it. I use nothing else for caulking baffles and such.

3M FireBarrier 2000 has held up well at the firewall perimeter, but my engine compartment isn't very oily. Key advantage is intumescence, swelling to fill gaps when exposed to fire. Given aluminum coated fiberglass is a comfort insulation, that particular property is moot. May as well use a polysulfide sealant or the 598.

Please note FireBarrier 2000 is not the same fire caulk product found at the big box stores. Lowes, for example, stocks a latex base FireBarrier product, as well as a new offering called FireBarrier 3000WT. It is identified as an intumescent neutral cure silicone, but I've not burned any, or subjected it to long term engine compartment exposure.

https://multimedia.3m.com/mws/media...tight-sealant-3000wt-technical-data-sheet.pdf

F1Boss said:

Kool Mat sells a product called ?Zero Clearance?. Peel ?n stick sort of stuff - VERY aggressive glue. I was able to cover at least 80% of my firewall (engine attached - ugh) by piecing in around the penetrations and attachment areas. Be sure to get some of their tape - same glue, which means it won?t move once it is placed. Seal the edge with Permatex Ultra Black.

Installation is much easier with the engine on the hoist!

This same product is what I also covered my cowling inside. I also sealed the perimeter with Permatex Ultra Black. Cut carefully so no wrinkles are present so the edge lays down easily.

https://www.koolmat.com/heat-resistant-products/foil-heat-products-protection/

Click to expand...

These type of insulation works to reflect heat and hardly any for insulating.
Furthermore, there are other issues if the fire/extreme heat gets to it and starts burning. Test a section of it by putting a torch to it and see if it generates awful lot of smoke.

Bavafa said:

Furthermore, there are other issues if the fire/extreme heat gets to it and starts burning. Test a section of it by putting a torch to it and see if it generates awful lot of smoke.

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True, an aluminum foil faced glass mat is comfort insulation, not fire protection....but smoke, flame, etc won't hurt anything when it's forward of the firewall. Assuming good gas sealing (the firewall is air tight), you can put almost anything on the forward side without adding significant risk. Not at all the same as placing it on the cabin side.

Stainless foil over a ceramic fiber insulator...comfort during normal ops, very good fire protection.

Aluminum foil over a fiberglass insulator...comfort during normal ops, only limited fire protection.

DavidHarris said:

Or if you built to plans and didn't insulate the firewall at all, are you satisfied, or regretful?

David

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No insulation on my firewall, inside or out. No regrets but an engine fire might change my mind. I spared no expense on TSFlightlines fuel, oil and brake lines and inspect everything during oil changes.

Raymo said:

No insulation on my firewall, inside or out. No regrets but an engine fire might change my mind. I spared no expense on TSFlightlines fuel, oil and brake lines and inspect everything during oil changes.

Click to expand...

I have never had an in-flight RV fire but read the accident reports of a few. The stainless steel "Firewall" is not the weak point. The fiberglass cowl will fail, allowing heat and smoke to impinge on windscreen, which will eventually fail... Before then all that heat and smoke will completely obscure your forward vision and eventually make the cockpit environment un-bearable even if firewall is intact. One word parachute or bailout. Fire in flight is a bad, FW insulation or not.

Insulation does keep overall normal heat and noise down in cockpit... implied increased fire protection aside. Not saying insulation is bad or does not help, just saying everything around the SS fire wall is fiberglass or aluminum.... both have some resistance to fire and ignition.

gmcjetpilot said:

I have never had an in-flight RV fire but read the accident reports of a few. The stainless steel "Firewall" is not the weak point. The fiberglass cowl will fail, allowing heat and smoke to impinge on windscreen, which will eventually fail...

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That would be one accident report, the Alexander RV-8. Got links to others?

There was one report of a melting windshield on a Kitfox, but the early KF round cowl and windshield arrangement is very different as compared to an RV.

In any case, the issue here is not turning an otherwise reasonable defense (a stainless firewall) into a fire transfer device.

DanH said:

That would be one accident report, the Alexander RV-8. Got links to others?

There was one report of a melting windshield on a Kitfox, but the early KF round cowl and windshield arrangement is very different as compared to an RV. In any case, the issue here is not turning an otherwise reasonable defense (a stainless firewall) into a fire transfer device.

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Sorry Dan did not see your question. I think we are talking past each other.

1) Does firewall insulation reduce heat and noise in cockpit making it more comfortable? Yes

2) Is putting flammable insulation and materials on cockpit side of firewall a bad thing? Yes. DanH: "...not turning an otherwise reasonable defense (a stainless firewall) into a fire transfer device" Point was taken. Ha ha.

3) Other in-flight RV fire accidents? I know of the RV-8 and recall another, but I was referring to all in-flight fires. A Lancair Legacy (recent) had massive engine failure and fire en-route; Pilot made forced landing, got on the ground, survived but badly burned. Bottom line fire bad.

4) Will good engine side insulation help with in-flight engine (oil/fuel) fire? Yes. I would not count on it saving my bacon if there was a big oil fed fire, but it helps. It's the obscuring smoke that is critical.

5) Things that can help (besides bailout) which airlines do or starting to do, to save crews, especially cargo planes subject to more intense fatal fires due to things like pallets full of lithium batteries: