Like many builders, I can't justify paying the outrageous prices that are commanded for aviation-grade certified firesleeve end dip (currently up to $118 a quart). But, you can't just leave the cut ends of the firesleeve hanging out to soak up oil and moisture. The two low-budget alternative end treatments I've heard of are Plasti-Dip (that non-slip stuff you dip your screwdriver handles in) and plain old RTV. In the spirit of scientific inquiry, I obtained a quantity of each and prepared two sample pieces of firesleeve, one treated with Plasti-Dip and one with RTV.
The cured Plasti-Dip (on the left in the photo below) was more brittle than I had expected, and developed cracks when the firesleeve was flexed gently. The RTV remained slightly rubbery, as it is wont to do, and the end of its test piece remained well sealed after the flex test.
Then I got out the matches and started burning stuff. When exposed to direct flame, the RTV became charred and began to emit a small amount of smoke, but would not ignite. This seems like appropriate behavior for the end of a piece of firesleeve.
The Plasti-Dip sample, on the other hand, caught fire quickly and burned like a candle until I snuffed it out:
The reader is left to draw his own conclusions as to which substance is most appropriate for use in an aircraft environment. The quantity of material involved is very small, and if you have open flame in your engine compartment, a quarter ounce of Plasti-Dip lighting off is probably not going to be your biggest concern. I will tell you that my firesleeve is treated with RTV.
I must also note that in order for this to be a truly meaningful test, I should have subjected a sample of the expensive stuff to the same tests... but I ain't that rich!
cheers,
mcb
The cured Plasti-Dip (on the left in the photo below) was more brittle than I had expected, and developed cracks when the firesleeve was flexed gently. The RTV remained slightly rubbery, as it is wont to do, and the end of its test piece remained well sealed after the flex test.
Then I got out the matches and started burning stuff. When exposed to direct flame, the RTV became charred and began to emit a small amount of smoke, but would not ignite. This seems like appropriate behavior for the end of a piece of firesleeve.
The Plasti-Dip sample, on the other hand, caught fire quickly and burned like a candle until I snuffed it out:
The reader is left to draw his own conclusions as to which substance is most appropriate for use in an aircraft environment. The quantity of material involved is very small, and if you have open flame in your engine compartment, a quarter ounce of Plasti-Dip lighting off is probably not going to be your biggest concern. I will tell you that my firesleeve is treated with RTV.
I must also note that in order for this to be a truly meaningful test, I should have subjected a sample of the expensive stuff to the same tests... but I ain't that rich!
cheers,
mcb
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