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03-11-2018, 09:17 PM
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Join Date: Jan 2014
Location: Phoenix
Posts: 160
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Tunnel Insulation
I've been reading through many of the posts. Those of you who followed Dan Horton's method of insulating the firewall, how did you insulate the tunnel and/or belly? Did you insulate the belly on the outside?
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03-11-2018, 09:29 PM
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Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,219
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Quote:
Originally Posted by jeffwhip
I've been reading through many of the posts. Those of you who followed Dan Horton's method of insulating the firewall, how did you insulate the tunnel and/or belly? Did you insulate the belly on the outside?
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I have a 24"x24" piece of stainless on the belly. I rolled the edges, placed a 1/16" fiberfrax blanket under it, sealed the edges with pro seal, and pop riveted it in place with stainless pop rivets.
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Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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03-12-2018, 05:44 AM
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Join Date: Jun 2006
Location: Delaware, OH (KDLZ)
Posts: 4,196
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I used fiberfrax and stainless foil in the tunnel. In over five years I've not had any issues. The tunnel is cool to the touch.
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03-12-2018, 06:16 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Kyle Boatright
I have a 24"x24" piece of stainless on the belly. I rolled the edges, placed a 1/16" fiberfrax blanket under it, sealed the edges with pro seal, and pop riveted it in place with stainless pop rivets.
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Do this ^^^^^
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Dan Horton
RV-8 SS
Barrett IO-390
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03-12-2018, 07:10 AM
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Join Date: Dec 2014
Location: Just Minutes from KBVI!
Posts: 1,039
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Quote:
Originally Posted by Kyle Boatright
I have a 24"x24" piece of stainless on the belly. I rolled the edges, placed a 1/16" fiberfrax blanket under it, sealed the edges with pro seal, and pop riveted it in place with stainless pop rivets.
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How thick is the stainless sheet?
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03-12-2018, 08:40 AM
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Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,219
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Quote:
Originally Posted by 1001001
How thick is the stainless sheet?
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Mine is .008, if I recall correctly. Thick enough to take some abuse, thin enough to cut with snips.
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Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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03-12-2018, 08:43 AM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,597
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Quote:
Originally Posted by Kyle Boatright
I have a 24"x24" piece of stainless on the belly. I rolled the edges, placed a 1/16" fiberfrax blanket under it, sealed the edges with pro seal, and pop riveted it in place with stainless pop rivets.
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While Dan H has convinced me this is the only way to go for insulating the firewall, I would not do this for the belly. If the fire gets so bad that it is needed on the belly, the plane is already gone. The downside of pop riveting this sandwich to the belly is it will tend to collect all the oil and grime that tends to end up there.
I used this insulation (double sided and edges sealed with aluminum tape) in the bottom of the tunnel and never had a hot tunnel: http://www.aircraftspruce.com/pages/...insulator3.php
I used the same stuff inside the double walls in the cabin and the rest of the floor. If I had to do over again, I?d probably not do that as most noise comes from the cabin top.
Again - do what Dan H recommends on the firewall. Leave the inside of the firewall bare.
Carl
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03-12-2018, 10:16 AM
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Join Date: Jan 2010
Location: Denver, CO
Posts: 1,967
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Belly Shield
I did install a belly shield too, using 0.010" SS sheet, which is plenty thick (i.e. it behaves like sheet stock, not foil). Using 1/16" Fiberfrax and securing with rivets and Fire Barrier 2000, the total assembly turned out to be fairly flat and well transitioned. I primed the aluminum skin underneath the belly shield too. See picture on my builder's log below.
http://www.mykitlog.com/users/displa...=222385&row=99
There wasn't much pillowing at all, and I assume that, after final paint, it will all but disappear. After seeing pictures of the RV-10 that had a fire event, with the gapping hole through the belly into the tunnel, I figured it was good insurance. Additionally, shielding the firewall and belly should keep tunnel heat down too; an added bonus. My $0.02.
Last edited by ppilotmike : 03-12-2018 at 10:32 AM.
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03-12-2018, 10:28 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Carl Froehlich
While Dan H has convinced me this is the only way to go for insulating the firewall, I would not do this for the belly. If the fire gets so bad that it is needed on the belly, the plane is already gone.
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No, it is not gone. We've already seen one example glide to a safe landing with a big hole melted through the belly skin. The issue is occupant smoke and fire exposure.
Quote:
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The downside of pop riveting this sandwich to the belly is it will tend to collect all the oil and grime that tends to end up there.
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The edges are sealed, and oil and grime won't hurt stainless steel. If desired, add this panel after the aircraft is painted, or shoot an epoxy primer on the bare aluminum prior to attaching the panel. It adds an additional layer of corrosion protection in the event the proseal or 3M Firebarrier silicone perimeter seal is breached.
The temperature of the belly skin is a function of energy-in less energy-out.
Insulating the inside of the tunnel reduces the fire exposure time and/or severity necessary to melt through the belly skin (into the tunnel, with its fuel lines, etc), because you have blocked one energy-out path.
Insulate the outer surface of the belly, and the aluminum skin has no significant energy-in path. And from the standpoint of comfort in normal operation, the structure never gets heated.
Adding worse to bad, the insulation you're recommending is cotton fiber. Here's the TDS:
http://www.aircraftspruce.com/catalo...9-06014tds.pdf
It's a home construction insulation not even remotely suitable for aircraft. Even if we ignore all questions related to smoke and flame, it is a corrosion risk...it holds water.
Look, the rule here is the same one your doctor lives by, primum non nocere...first do no harm. If you don't want a stainless belly overlay, fine, don't add it. But please, stop doing stuff that can hurt people.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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03-12-2018, 11:01 AM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Structural
Quote:
Originally Posted by ppilotmike
I did install a belly shield too, using 0.010" SS sheet, which is plenty thick (i.e. it behaves like sheet stock, not foil). Using 1/16" Fiberfrax and securing with rivets and Fire Barrier 2000, the total assembly turned out to be fairly flat and well transitioned. I primed the aluminum skin underneath the belly shield too. See picture on my builder's log below.
http://www.mykitlog.com/users/displa...=222385&row=99
There wasn't much pillowing at all, and I assume that, after final paint, it will all but disappear. After seeing pictures of the RV-10 that had a fire event, with the gapping hole through the belly into the tunnel, I figured it was good insurance. Additionally, shielding the firewall and belly should keep tunnel heat down too; an added bonus. My $0.02.
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If I read your blog pictures correctly, the 1/16 Fibrerfrax is sandwiched between the two skins (SS and original belly aluminum) by the same rivets that attach the skins to the fuselage ribs.
Wouldn't having this layer of Fiberfrax in the assembly screw up the structural integrity of the skin to rib riveted joint?
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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