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diy floor/padding/insulation ideas?

jcaplins

Well Known Member
For those interior diy'ers... what did you use for the floors?

I have no other interior niceties other than seats. I would like to install some sort of floor system that includes insulation/padding to fill the space between the floor stiffeners. I would like to mount that insulation to a thin piece of something: aluminum, plywood, fiberglass, carbon fiber, ?, etc. I'm not sure about carpeting it or not. The goal would be to have a floor that is not the skin of the fuselage and provide some sound dampening.

I would like to have a separate piece for both the pilot and passenger sides that can easily be lifted out without removing screws. I also don't want something that can slide and bunch up at the rudder pedals either. And I'm not worried about covering the center fuel pump section yet.

fire retardant, non toxic smoke generating materials would be important.

So, what have others done? what worked well, or what would you have done differently.

Thanks,
 
Balsa

I put balsa wood between the ribs and then an aluminum floor on top. The carpet is gel tied in place. I put fiber frax under carpet for fire proofing.
 
The best approach is to insulate the outside of the airplane first. Try 1/16" fiberfrax felt under a 0.005" stainless steel panel attached to the belly, as wide as the cowl outlet and extending about 2 feet rearward. Extend the leading edge into the engine compartment and curl it up to attach to the firewall, so the exit has a nice radius at the firewall corner.

Unsized batts of ceramic refractory fiber (kaowool or similar) don't smoke when heated. It's darn near the only material that doesn't, and would insulate nicely between the aluminum skin and an aluminum floor. Loose fibers are a possible cancer risk, so it would need to be sealed away. The same material is available in rigid board form, which might work well when cut to fit between the stringers. However, be aware that it will smoke when heated, due to the adhesive matrix which holds the fibers in rigid board form. Same is true for fiberfrax felt, BTW. It smokes when heated as the adhesive burns away. With any of these materials, the inner floor would need to be well sealed around the perimeter to keep airborne fibers and smoke out of the cockpit.

Bugsy's balsa wood idea is interesting. Stiff, light, and a good insulator, but I would definitely install the fiberfrax/stainless panel on the outside. Fiberfrax under the carpet as "fireproofing" is like wearing your raincoat inside your underpants. And as as noted (again), it smokes. Don't use it inside the cockpit.

A really trick removable floor panel? Aluminum with a bonded aluminum honeycomb sandwich on the underside.

Bare aluminum floor is wonderful; lightweight, easy to clean, wears like, well, aluminum. Ever notice how we get carpet in our cars, then cover the carpet with floor mats so it doesn't turn into a mess?

Then we install carpet in our airplanes.

The gods must be crazy....;)
 
...

A really trick removable floor panel? Aluminum with a bonded aluminum honeycomb sandwich on the underside.
...

Where would you buy this and is it already bonded?
If not, how would you bond the aluminum to the honeycomb?
 
How hot does the floor get with no insulation? I am sure that there are a lot of RVs flying with out having insulation on the outside under the floor.
 
....

fire retardant, non toxic smoke generating materials would be important.

So, what have others done? what worked well, or what would you have done differently.

Thanks,

Jeff,
For the price of approximately 73 gallons of avgas Classic Aero has a nice floor solution. Take it unless you like to do it yourself. Once in a while I remove the carpet for cleaning or drying ( I am parked under the elements) I can't stand the floor vibration for couple hours. I fly an RV9 the similar fuselage to yours. Luke and Co. did a great job designing that dampening sandwich. You will love it. Just sit on the ground half a day to afford it. :D
 
What about cork for an insulator? I tried to torch through a piece and it worked well with little heat transfer. I can't remember how much smoke there was. Any thoughts about cork?
 
I used some ACS 3/4" soundproofing black foam material (I don't recall what it is called but comes in various thicknesses - not fireproof at all). Over that I laid a piece of 0.040 aluminum on each side of the cockpit (one for pilot, one for passenger). I was able to cut and fit the aluminum so that it stays in place by bending a flange on the center portion where it abuts the longeron, and the other side slides under the longeron on the side of the airplane. Pops in and out easily. On top of the aluminum piece, I glued some skateboard material for friction so my feet don't slide around on the aluminum.

Has worked well for me for 8 years.
 
Where would you buy this and is it already bonded?
If not, how would you bond the aluminum to the honeycomb?

Need a base plate (3/4" birch plywood, a 1/2" aluminum plate, whatever you have handy), a plastic sheet, some sealant tape, and a vacuum pump and fittings. Lay the bottom aluminum sheet on the plate, spread thin layer of a suitable adhesive (perhaps Hysol 9430), add honeycomb, and bag it to the plate for cure. Flip and repeat for the top sheet, which will be the actual cockpit floor.

The first sheet can be very thin. If the floor stringers are 3/4", use a 1/2" honeycomb, which will result in 1/4" air space between the thin face sheet and the outer skin.

Here's a gear door bagged on a base plate in my shop. Foam core with top plies, but the setup is the same.

IMG_0583.jpg
 
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I used some ACS 3/4" soundproofing black foam material (I don't recall what it is called but comes in various thicknesses - not fireproof at all).

Here Greg knows the risk. If the belly skin melts (as it has been shown to do given an fuel-fed engine fire in flight), or even gets very hot, that black foam will ignite, and when it does it's really awful. The saving feature is the aluminum cabin floor overlay, which should isolate the burning foam to some degree. I'd still bet on a very serious smoke problem.

Below is black rubber soundproofing foam (Soundex) on the cabin side of a simulated stainless firewall, with an FAA-standard 25 sq in hot spot on the front side. The hot metal ignites the foam.

Let's be really careful about insulation in the cockpit, ok?

P8310004.JPG


P8310005.JPG


P8310006.JPG
 
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What about cork for an insulator? I tried to torch through a piece and it worked well with little heat transfer. I can't remember how much smoke there was. Any thoughts about cork?

It's a good insulator, and when it chars, it's pretty good fire protection. Trouble is (again) the smoke in the cockpit. If the floor is really well sealed around the perimeter so the smoke and outgas can't enter the cockpit, it's viable, just like Bugsy's balsa.

On the other hand, fireproofing the exterior of the belly skin so the structure doesn't heat, then using metallic or pure ceramic materials on the inside pretty much guarantees zero problems, no matter what happens.
 
Dan, those are excellent ideas. It's because of what you have written here and in other threads that I haven't put anything in the cockpit area.

Now when I wrote the original question, in my head, "insulation" was more of sound deadening material and floor vibration reduction , rather than heat insulating. But, I do not want the sound deadening material to be a source of toxic smoke. sorry for any confusion.

- I like the simplicity of balsa wood and aluminum.
- cork would be good, but is typically a lot of glue holding it all together and would end up being highly flammable and toxic.
- I wonder if aluminum honeycomb would make the noise in the cockpit worse?
- I like the idea of using ceramic refractory fiber batting; would need to figure of sealing it and still have removable floors.
- Vlad, I have considered the Classic-Aero carpet...but man that is some pricey carpet and foam. Also, I would need some more custom cutouts for antennas which would make it even more expensive. Perhaps all I need is some closed cell foam that's non-toxic.
 
Below is black rubber soundproofing foam (Soundex) on the cabin side of a simulated stainless firewall, with an FAA-standard 25 sq in hot spot on the front side. The hot metal ignites the foam.

Dan Horton,

I am interested in putting some insulation in my fuse for sound deadening. You posted pics with Soundex products. They show 2 different materials on their web site. Is the one you show in your pics and warn about fire the one Soundex says meets the FAR 23:85a/25:856a Part II compliant? Or was it their other product without that listing?

http://www.soundexproducts.com/order.html

Would like to add something, but your post got my attention and I don't want to be foolish here. Would you please give me your advice on what you would use if you wanted to have some sound deadening materials added?

Thank you .
 
I am interested in putting some insulation in my fuse for sound deadening. You posted pics with Soundex products. They show 2 different materials on their web site. Is the one you show in your pics and warn about fire the one Soundex says meets the FAR 23:85a/25:856a Part II compliant? Or was it their other product without that listing?

http://www.soundexproducts.com/order.html

Would like to add something, but your post got my attention and I don't want to be foolish here. Would you please give me your advice on what you would use if you wanted to have some sound deadening materials added?

The first question is "Where in your fuselage?"

The cabin firewall and the floor immediately aft of the firewall are high risk areas for ignition of bad insulation choices. Floor panels some distance aft of the firewall, as well as cabin sidewalls, are low risk, as they are unlikely to be heated to a high level in the event of an engine fire.

Part 23/25.856 materials are intended for cabin sidewalls, and are not fireproof. They are fire resistant, meaning they are merely required to self-extinguish within 15 seconds after the ignition source is removed, without dripping too much melted material. The ignition source per the 23/25.853 test standard is very small....Bunsen burner size. Think little Johnny in the bathroom with his daddy's cigarette lighter, or a hot electrical wire.

Part 23/25.856 materials are entirely unsuitable for firewalls and forward floors. An engine fire is not an ignition source that can be removed at will, and the energy level (2000F over 25 sq inches) is much, much higher. In my opinion, there are no 23/25.856 materials suitable for firewall contact. In practical test, some have been absolutely horrifying. No surprise really. Regardless of claims, why would any sensible builder think rubber, plastic, and polyester can be placed in contact with red hot stainless steel, without adverse consequences?

Actual sound deadening is a big subject. There are several possible approaches. The absolute best would be to build a composite airframe, as the vibration decay loss factors for all composite materials are much higher than metals. Damping resonant vibration of panels can also be done with the addition of mass (lowering natural frequency), or stiffening (raising natural frequency), or adding true damping, i.e. turning the vibratory energy into heat. All of these things add weight.

Ever noticed how an airplane can be much louder when operated in a certain engine RPM range? That is resonant vibration; the engine or prop is exciting a panel at its natural frequency, so its vibratory amplitude gets large. If I had such a range and i wanted to run there, I'd try chasing down the offending sound generator (the particular vibrating panel), and deal with it as necessary.
 
The first question is "Where in your fuselage?"

The cabin firewall and the floor immediately aft of the firewall are high risk areas for ignition of bad insulation choices. Floor panels some distance aft of the firewall, as well as cabin sidewalls, are low risk, as they are unlikely to be heated to a high level in the event of an engine fire.

Thanks for info Dan. Do you know of a specific product that would be suitable for firewall and floor next to firewall (fireproof)? Since rebuilding in composite is not an option, would like to know if there is a suitable product out there?
 
I use this product to pre-protect clothing for full fire burns on performers clothing. Works very well. If you want to add some protection to a material. That is not to say spray this on a flammable material and hope for the best, but something to consider.

Here I am on fire with Ban Fire on a white cotton dress, I got two burns out of the clothing probably could have done a third easily.

kent%20on%20fire.jpg


http://www.banfire.net/allproducts.htm

Kent
 
Thanks for info Dan. Do you know of a specific product that would be suitable for firewall and floor next to firewall (fireproof)?

Sound insulation on a firewall? No, I'm not aware of a suitable product specific to sound reduction, rather than heat. Why do you think you need one? Even with 20 lbs of insulation, any conceivable sound reduction won't trump ANR or in-ear headsets.

Read this thread...good folks who thought they "needed" various insulation products inside the cabin, and installed very bad choices...cotton fiber, urethane foam, etc.

http://www.vansairforce.com/community/showthread.php?t=141016

Bad firewall and floor insulation should be called fire transfer material. It brings an otherwise isolated fire right into the cockpit. Some do so very rapidly.

This from NTSB report LAX99LA063. The actual failure was a loose B-nut on the fuel pump. The airplane was in the pattern, and flown by a well-respected guy.

Factual Information
On December 31, 1998, at 1151 hours Pacific standard time, an experimental Young Harmon Rocket II, N288M, was destroyed following an in-flight fire and hard landing at a private airstrip near Esparto, California. The commercial pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. He and one passenger departed approximately 10 minutes before the mishap. The pilot was in serious condition after suffering burns over 1/3 of his body and succumbed to his injuries over a month after the accident; the passenger sustained minor injuries. Visual meteorological conditions prevailed for the local personal flight and no flight plan had been filed.

The pilot completed one flight and was taking another passenger up for a short flight around the area. On the downwind leg witnesses reported everything looked and sounded normal, and then they heard several pops, which they attributed to the engine being throttled back. One witness asked the other if the airplane was on fire. The flames he thought he observed went away. They dismissed his observation as sun glare and turned away. When they looked at the airplane again on base leg, 2 to 3 feet of bright yellow/orange flame and a trace of black smoke emanated from the cowling. On touchdown the airplane bounced, hit again, then skewed 20 degrees to the left. The left main landing gear collapsed outboard and the right main collapsed underneath the airplane. They gathered fire extinguishers and did not see the airplane come to a stop.

The passenger stated he saw light gray smoke in the cockpit and notified the pilot. The pilot secured the master switch and turned onto the base leg. At this point the passenger did not observe flames or feel any heat. As the airplane turned wings level onto final, thick black smoke that smelled like burning fiberglass or plastic filled the cockpit. After the airplane came to rest, he observed flames around the pilot and felt high heat. He yelled to the pilot to open the canopy, but the pilot responded he could not get it to open. Momentarily, the canopy opened halfway.

As the rescuers arrived, flames were still coming from under the cowling. The front cockpit was so filled with smoke that they could not see if the pilot was still in the airplane. The rescuers helped the rear passenger out, and then noticed the pilot on the side of the runway.
 
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