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  #1  
Old 03-11-2018, 09:17 PM
jeffwhip jeffwhip is offline
 
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Default 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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  #2  
Old 03-11-2018, 09:29 PM
Kyle Boatright Kyle Boatright is offline
 
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Quote:
Originally Posted by jeffwhip View Post
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?
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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  #3  
Old 03-12-2018, 05:44 AM
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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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  #4  
Old 03-12-2018, 06:16 AM
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Quote:
Originally Posted by Kyle Boatright View Post
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.
Do this ^^^^^
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  #5  
Old 03-12-2018, 07:10 AM
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Quote:
Originally Posted by Kyle Boatright View Post
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.
How thick is the stainless sheet?
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  #6  
Old 03-12-2018, 08:40 AM
Kyle Boatright Kyle Boatright is offline
 
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How thick is the stainless sheet?
Mine is .008, if I recall correctly. Thick enough to take some abuse, thin enough to cut with snips.
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  #7  
Old 03-12-2018, 08:43 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post
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.
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, Id 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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  #8  
Old 03-12-2018, 10:16 AM
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Default 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.
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Last edited by ppilotmike : 03-12-2018 at 10:32 AM.
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  #9  
Old 03-12-2018, 10:28 AM
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Quote:
Originally Posted by Carl Froehlich View Post
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.
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:
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.
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.

Quote:
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
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.
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  #10  
Old 03-12-2018, 11:01 AM
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Question Structural

Quote:
Originally Posted by ppilotmike View Post
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.
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?
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