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Inside firewall insulation

F

fabricflyer

Well Known Member
What are you guys using out there (if anything) for inside firewall insulation? Has anyone used, or familiar with, Koolmat heat barrier?

Thanks Allen
 
Firewall insulation

I was not thinking when doing motor side of firewall to add insulation. My plane is parked in a desert atmosphere. HOT!! With all the things connected to motor side of firewall I went with double sided insulated foil on inside and worked out great. Always clean but a stand on your head to install. Aircraft Spruce p/n 09-06015 and high temp RTV and your set. Don't smear the hole thing, just put daps to hold in position. Over 40 hrs to date on insulation and it looks like new. 4x3' sheet will work but you can't make a mistake so order a little longer piece. Oh, and I cut out where angles are so it's slice and dice.:rolleyes:
 
Firewall insulation

Dan H. Is correct and I would never ever argue with him. This was just my solution rather than tackling motor side of firewall.:eek:
 
RVTOY said:
With all the things connected to motor side of firewall I went with double sided insulated foil on inside and worked out great. Always clean but a stand on your head to install. Aircraft Spruce p/n 09-06015 and high temp RTV and your set.
Click to expand...

If I understand correctly, you've installed "Ultra Touch Natural Cotton Radiant Barrier" on the cabin side of a firewall?

https://www.aircraftspruce.com/catalog/pdf/09-06014tds.pdf

I have not tested this particular material, but I would be happy to make a small wager about its hot firewall performance. I don't think it will last 30 seconds without open flame on the cockpit side.
 
Huh?

This sounds like a discussion between a couple politicians. All kinds of "you can't do that", but nothing about what you CAN or SHOULD do. Care to enlighten us?

And like some others here, it's really too late for me to address the engine side of this problem, but I'd like to find something to apply to the cockpit side of the firewall.

Thanks,

Jim
 
See Post 2

Jim,

Dan has done extensive testing of all sorts of materials generally used on the firewall to reduce heat transmission to the cockpit. Please see his post above and follow the threads for the real story of science as it applies to this subject.

Best regards,

Merrill
 
Jim,

Some years ago I was working a mid-engine design project with a friend. Since the main spar passed through the engine bay, we got curious about fire protection. I did the reading, built a burn test rig, etc. Later, when building my RV-8, I threw together another burn rig and started exploring how to insulate a conventional sheet metal firewall.

Just a little later, a VAF reader asked what sort of glue to use to attach a particular firewall insulation in his project. Read the ensuing conversations here:

http://www.vansairforce.com/community/showthread.php?t=37012

Turned out the very popular "firewall insulation" was actually polyester fiber. The vendor had done no due diligence before selling the stuff to builders.

A great many products being offered as firewall insulation are entirely unsuitable for a cockpit-side application. Given a typical fuel-fed fire, they will not protect the occupants, but rather, will contribute to their injury. Placing plastic, rubber, paint, or flammable fibers in contact with a red hot firewall is an invitation to the Darwin Awards.

The ironic fact is this: In the end, after much test and measurement, and by a large margin, no cockpit-side insulation scheme was as effective as insulating the entire firewall structure from the engine side...and practically nothing a builder can do to the engine side can cause injury. The above applies to both comfort insulation as well as fire protection insulation.

What do I suggest? I've posted specifics previously. Best to use the search function, because there is much to learn.

As for "Too late to insulate the engine side", well, would it be too late to install a skipped bolt, or a missed rivet, or update your panel later, or pull a tank to fix a leak? Anything worth doing is worth doing right...and you might be interested to know I pulled my own engine and mount off the firewall, as a unit, to install my own insulation. The test results were that significant.

 
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It took me one full day to remove my engine and engine mount, install stainless foil/fiberfrax sandwich, refigure pass throughs, and secure/seal exactly as in Dan's picture above. Half day to rehang mount and engine, reattach what firewall hardware I'd completed to that point.

Dan's testing and suggestions really swayed me- small price to pay, if only to sleep better at night, let alone have a better chance at surviving if god forbid something bad happens.

Between firewalls and fiberglass, there's evidence, not anecdotes behind Dan's suggestions.
 
Proseal

Dan
I've followed your test threads during my build process and plan to use your technique. Thanks for all the hard work.

I do have a question.
I see Proseal used between the skin and firewall flange. Why?
 
If stainless is the best firewall, would there be a reason to use a layer of stainless over the fiberfrax rather than foil? How about natural cork?

I am building a 9A. I have a light battery and a fixed pitch Catto. The front end of my plane is light and I believe I will have to put a crush plate to get the CG where I want. The firewall isnt as far forward as the crush plate, but maybe the weight of a second layer of stainless wouldn't be that much of a penalty.

Any thoughts? I will be re-installing my engine next week and still trying to figure out the best options.
 
wirejock said:
I see Proseal used between the skin and firewall flange. Why?
Click to expand...

The cowl area can be pressurised slightly with reference to the cockpit. Therefore any smells, fumes, or smoke from the engine area may be forced into the cockpit under certain circumstances.

Bevan
 
rockwoodrv9 said:
Right on the foil. Just wondering if it would be easier to clean and maintain if it was a sheet.
Click to expand...

Weight would be the primary reason to use foil with its primary purpose, based on DanH posts, is to hold the fiberfrax in place so it can do its job insulating. If weight were not a concern, thicker should, in theory, be better.

my .20 (inflation).
 
firewall insulation

here how I did last year after read tons of threads , finally I followed the Dan way.
Thanks Dan ;)

15qf1hw.jpg
 
Another way, 1/8 fiberfrax with .015 stainless (forward of the main firewall). Needed weight forward anyways and wanted something more robust than foil.... Forward stainless sheet is not sealed around the perimeter to allow off gassing of the fiberfrax in case of fire.

 
Raymo said:
Weight would be the primary reason to use foil with its primary purpose, based on DanH posts, is to hold the fiberfrax in place so it can do its job insulating. If weight were not a concern, thicker should, in theory, be better.
Click to expand...

Technically speaking, the stainless foil is a gas-tight reflector over an insulator, and as such, it cannot be replaced with something like cork. It just happens to hold the insulator in place in this application.

Choice of thickness revolves around weight and appearance. Pick what you like. As noted previously, it can be very thin and meet the fire performance requirement, but thinner is less durable and looks a bit more wrinkly.
 
Double sided insulation interior

Dan H sorry it took so long to get back to material I used.
Insulation with Double sided foil. Spruce #09-066016

The Insulator is one of the finest sound proofing and thermal insulation materials available, and will last the life of the aircraft. The aingle and dual sided Insulator materials are ideal for installation on interior skin, floor, engine covers, doors, headliners, and bulkheads. The Insulator uses multi - layered fiber plys bonded to reinforced high performance foil to provide optimum barrier to acoustics, radiant heat, thermal heat, and moisture. Insulator is available in 4x 6 panels or by the lineal foot (4 wide). Install Insulator with Sticky Stuff spray adhesive and Insul-Tape. Not FAA approved.
 
RVTOY said:
Dan H sorry it took so long to get back to material I used.
Insulation with Double sided foil. Spruce #09-066016

The Insulator is one of the finest sound proofing and thermal insulation materials available, and will last the life of the aircraft.
Click to expand...

That number doesn't work for me.

By the way, notice that the description mentions that its ideal for all sorts of bulkheads and surfaces. But it doesn't mention the firewall

I can't evaluate the product, but be certain that your solution isn't causing a bigger potential problem.
 
I was thinking of replacing the fiber blanket with the cork, then a stainless sheet so,the cork was sandwiched between.


DanH said:
Technically speaking, the stainless foil is a gas-tight reflector over an insulator, and as such, it cannot be replaced with something like cork. It just happens to hold the insulator in place in this application.

Choice of thickness revolves around weight and appearance. Pick what you like. As noted previously, it can be very thin and meet the fire performance requirement, but thinner is less durable and looks a bit more wrinkly.
Click to expand...
 
rockwoodrv9 said:
I was thinking of replacing the fiber blanket with the cork, then a stainless sheet so,the cork was sandwiched between.
Click to expand...

Roughly equal as an insulator for comfort purposes. May result in a smoother firewall appearance when foil is riveted over it.

Can't tell you what to expect when subject to the FAA standard 5" x 5" 2000F hot spot; not tested. Speculation? Ignition temperature is very low compared to inorganic fibers, but it may char in a beneficial manner. For sure would need provision for significant outgassing, much more so than the fiberfrax felt, in which the organic burn-off is limited to the latex binder.

RVTOY said:
Dan H sorry it took so long to get back to material I used. Insulation with Double sided foil. Spruce #09-066016
Click to expand...

Bad choice. Maybe pictures would help. Both were taken with the exact same burner running on the hot side....but the results are very different.

Here is what you want. The forward side of the firewall is insulated with an inorganic ceramic felt under SS foil. The structure you see is the same as in your RV; notice the rivets are not melting. The burner has been running several minutes. The black radiant heat target represents the soles of your shoes:



Here's what I'm afraid you'll get with an organic fiber on the inside of your firewall. Same burner, same setting. BTW, this is Nomex felt. Good luck with cotton.

 
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Thanks Dan. I did a mapp gas torch test and the thermal transfer was very low, but there was lots of smoke. The cork did char and was easily broken apart but you could touch it with the torch on the other side.
 
rockwoodrv9 said:
Thanks Dan. I did a mapp gas torch test and the thermal transfer was very low, but there was lots of smoke. The cork did char and was easily broken apart but you could touch it with the torch on the other side.
Click to expand...

I note (and I hope others do too) that you are proposing cork as an insulator on the forward, engine side of the structural firewall, so a center overlap vent in the foil overlay would release the outgas and smoke into the engine compartment, which is, of course, already on fire. The issue is how much outgas and smoke, as it is (to some unknown degree) a fuel. A small quantity is not a problem. A large quantity might be a problem. If you got lots of smoke with a little bitty torch, well, gee. I remind you that the outgas product from ordinary fiberfrax felt is limited to the organic latex binder.

Read this: http://www.vansairforce.com/community/showpost.php?p=1005173&postcount=5

A word on testing. Applying a bunsen burner or a bottle torch to a material sample is the very rough equivalent of an FAR25 cabin wall insulation test. The fundamental pass-fail is that the material must not exhibit open flame 15 seconds after the burner is removed (self extinguishing), and it must not melt and drip. Think "Little Johnny with a cigarette lighter in the airliner bathroom" and you have the right idea.

The difference between the above and firewall/powerplant fire testing is the specified heat flux...in essence, the quantity of heat energy transferred to the sample. The above uses a Bunsen burner with a flame 1.5" high to heat one edge of the material, much as you might light the edge of a sheet of paper. Powerplant equipment critical to flight and firewalls get blasted with a much larger burner. The specified burner nozzle exit is 6" x 11", if that helps illustrate the difference.

Vendors routinely state "FAA Approved", but when you read the fine print, the quoted standard is in fact 25.853, which deals with passenger cabin walls, seats, and partitions in transport category aircraft. It's a good standard for your cabin upholstery..but there is no firewall insulation criteria in 25.853.

Along similar lines, the pretty blue foil backed cotton insulation meets "ASTM-84"....a standard keyed to flame spread across the ceiling of an open room.

Below are the appropriate standards for Part 23 aircraft. Take particular note of 23.1182. Our EAB aircraft don't need to meet Part 23 standards. Some of us think they should be better.

§ 23.1191 Firewalls.

(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.


§ 23.1182 Nacelle areas behind firewalls.

Components, lines, and fittings, except those subject to the provisions of §23.1351(e), located behind the engine-compartment firewall must be constructed of such materials and located at such distances from the firewall that they will not suffer damage sufficient to endanger the airplane if a portion of the engine side of the firewall is subjected to a flame temperature of not less than 2000 °F for 15 minutes.
 
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DanH said:
The burner has been running several minutes. The black radiant heat target represents the soles of your shoes:
Click to expand...

That is a great test. I am assuming that the 178 degrees we see is degrees F? Pretty interesting to know that even with the SS foil and fiberfrax that your feet would be so hot you would have to move them off the pedals. Was the temp stable? How long did it take to get to 178? Thanks for the great info. Fire doesn't happen often but when it does it can be bad.
 
DanH said:
Jim,

Some years ago I was working a mid-engine design project with a friend. Since the main spar passed through the engine bay, we got curious about fire protection. I did the reading, built a burn test rig, etc. Later, when building my RV-8, I threw together another burn rig and started exploring how to insulate a conventional sheet metal firewall.

Just a little later, a VAF reader asked what sort of glue to use to attach a particular firewall insulation in his project. Read the ensuing conversations here:

http://www.vansairforce.com/community/showthread.php?t=37012

Turned out the very popular "firewall insulation" was actually polyester fiber. The vendor had done no due diligence before selling the stuff to builders.

A great many products being offered as firewall insulation are entirely unsuitable for a cockpit-side application. Given a typical fuel-fed fire, they will not protect the occupants, but rather, will contribute to their injury. Placing plastic, rubber, paint, or flammable fibers in contact with a red hot firewall is an invitation to the Darwin Awards.

The ironic fact is this: In the end, after much test and measurement, and by a large margin, no cockpit-side insulation scheme was as effective as insulating the entire firewall structure from the engine side...and practically nothing a builder can do to the engine side can cause injury. The above applies to both comfort insulation as well as fire protection insulation.

What do I suggest? I've posted specifics previously. Best to use the search function, because there is much to learn.

As for "Too late to insulate the engine side", well, would it be too late to install a skipped bolt, or a missed rivet, or update your panel later, or pull a tank to fix a leak? Anything worth doing is worth doing right...and you might be interested to know I pulled my own engine and mount off the firewall, as a unit, to install my own insulation. The test results were that significant.

Click to expand...

I fortunately read many posts on the subject and gave up my initial idea of Dynamat on the interior (thanks to Dan and others previous work/experimentation). I ended up getting an automotive heat reflecting material (adhesive-backed fiberglass with an aluminum reflective coating. I put this on the engine side of the firewall and it works quite well. My initial phase I flights we all in the 90* ambient range and I never noticed heat radiating from the firewall. Not scientific, but it achieved my objective of reducing heat load from the firewall in summer. This approach does not provide the flame protection that Dan's method does, but it was much easier to source and install.
 
lr172 said:
I ended up getting an automotive heat reflecting material (adhesive-backed fiberglass with an aluminum reflective coating. I put this on the engine side of the firewall and it works quite well..This approach does not provide the flame protection that Dan's method does, but it was much easier to source and install.
Click to expand...

...and it cannot do any harm.
 
I'm in

Thanks Dan,
I broke down and bought a roll of firewall 2000 from aircraft spruce Saturday for the firewall side. I'll have to pull the engine and mount but this would be for a good cause. Not sure whether to attach with a stainless pop rivet and washer or use some of that firewall 2000 rtv stuff in blobs between blanket and firewall. This blanket has alum on one side, stainless on the other, and ceramic sandwiched in between. I don't want the blanket coming off years from now and was wondering what kind of pop rivet spacing you think would do the trick?
cj
 
grubbat said:
Thanks Dan,
I broke down and bought a roll of firewall 2000 from aircraft spruce Saturday for the firewall side. I'll have to pull the engine and mount but this would be for a good cause. Not sure whether to attach with a stainless pop rivet and washer or use some of that firewall 2000 rtv stuff in blobs between blanket and firewall. This blanket has alum on one side, stainless on the other, and ceramic sandwiched in between. I don't want the blanket coming off years from now and was wondering what kind of pop rivet spacing you think would do the trick?
cj
Click to expand...
Just another data point. I used the firewall 2000 material you have purchased. I did not rivet anything at all. The material is being held in place by the various components that are bolted to the firewall. It is sandwiched in between the component and the firewall. Then I have used aluminum tape on all of the edges. It has been flying for 5 years and still doing just fine.
firewall%252520insulation.jpg
 
grubbat said:
...bought a roll of firewall 2000 from aircraft spruce Saturday for the firewall side. ... Not sure whether to attach with a stainless pop rivet and washer or use some of that firewall 2000 rtv stuff in blobs between blanket and firewall. This blanket has alum on one side, stainless on the other, and ceramic sandwiched in between. I don't want the blanket coming off years from now and was wondering what kind of pop rivet spacing you think would do the trick?
Click to expand...

SS pop rivet and SS washer Take a look at the spacing of the existing structural rivets in the firewall. The proper spacing would put a pop rivet between them "every so often" ;)
 
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