Will the foil I previously posted from McMaster work ok or is the another product to look at?
No practical difference between 304 and 309 in this application. 304 costs less. 0.002" thickness is adequate for a firewall overlay. 0.005" might offer a little better appearance, but obviously would weigh more than twice as much.
What do you think of the bio therm products for a fire sealant?
A single Rectorseal product was checked below. You should not make assumptions about any other product from the same company....or a similar product from another company.
http://www.vansairforce.com/community/showthread.php?t=72087&highlight=biotherm
Returning to floors...
The photo below was posted by a member of our community after his forced landing. A loose fuel fitting near the engine driven fuel pump caused a fire. The fire, as can be expected, followed the airstream, meaning out the cowl exit.
That's when things started getting ugly. The inside of the tunnel was insulated with what is believed to have been an aluminized polyester fiber mat, a product a popular vendor had been selling as "firewall insulation". Insulating the backside of an aluminum panel means energy escape from that side is slowed. So, two things happened in short order....the aluminum belly skin melted, and the polyester insulation caught fire.
Even with the powerplant secured, the pilot now found himself with a fire in the tunnel and thick black smoke in the cockpit. He jettisoned a door, which ventilated the cockpit enough for a successful landing in a field. The fire in the tunnel continued to burn after landing, and was not extinguished until much later. Aircraft was a total loss.
Yes, you're looking down through the bottom of the airplane. BTW, note the melted fluid lines.
The builder/pilot did a great job dealing with the emergency, but he was also very lucky. In this case the tunnel contained the insulation fire. The same insulation on the backside of an RV firewall, open to the cockpit, would have severely injured or killed him. This is what happens when you place polyester fiber insulation in contact with hot stainless:
I would not expect the post-consumer recycled denim insulation recommended by Carl to do much better. Remember, "flame retardant" or "flame resistant" merely means the fire will eventually self-extinguish when the heat source is removed. With the heat source active, the material may burn like **** itself and still wear the FAR 25.853 approval.
This is an insulation appropriate for the temperature and heat flux specified for a firewall. It is alumina silica refractory fiber, with no sizing or binder. The burner is running on the opposite side in this photo (same burner, same setting as previous photo), and has been for several minutes. You can see the stainless sheet glowing red near the top.
The downside to the refractory fiber is some degree of lung cancer risk for unprotected users. If the builder wears breathing protection and fully encapsulates the fiber inside an aluminum foil envelope before installation, this is a safe product for use inside the airplane.
However, I can't recommend it for three reasons. (1) If used to insulate the back side of an aluminum panel subjected to flame, it will cause the aluminum to melt through more quickly. (2) Such an approach does nothing to protect the airframe. (3) Compared to insulating on the hot side, it is not nearly as effective.
Same burner again, foil/ceramic felt on the hot side. The rivets and aluminum angle are just as they are in your RV firewall. Note they are entirely intact, rather than melted as they would be if the insulation was on the cabin side. This is several minutes into the burn. The black heat target is 6" from the firewall, and simulates the soles of your shoes, here at 178F. No smoke, no flame transfer to the cockpit, firewall structurally intact. This is a survivable environment.
Let's wise up out there, please. Plastic, rubber, paint and foam in firewall contact has the potential to kill you dead as canned fish. With an RV-10, we're likely to find ourselves mourning a
family.