During testing of our firewall penetration kits, we wanted a fireblock material to seal the stainless steel fitting to the firewall and seal out moisture and gas from the other end. Many months of testing resulted in the use of Rectorseal Biotherm 100. Very nice for sealing the firewall on the RV-10.
The reasons for settling on this material are as follows:
Testing on “high temp” silicone sealer revealed that “high temp” for common silicone meant burning at about 600 degrees. Unacceptable with windblown Avgas burning at 1875 degrees. We tried Intumescent Sealers. Intumescent meaning they expand with heat, supposedly sealing voids better. The problem with intumescent sealers is that they start to expand at 250 degrees. Not a good program right next to a cylinder that runs 350 degrees or hotter. The Biotherm proved through testing to be the best material available for the application of sealing out flames on the firewall. It is easy to apply, stays flexible, it’s not intumescent, and blocks fire to 2000 degrees. Available in 1/2oz/14.7868ml.