Firesleeve end dip: A scientific inquiry

[mburch]

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

[Greg Arehart]

Thanks Matt! Pretty reasonable "everyman" test. I know which I would choose.

greg

[SHIPCHIEF]

Which RTV product did you use? Those results look good, thanks for sharing.
I was thinking about using the red/copper high temp RTV in the squeeze tube from Permatex (and competitors), that states "High Temp". Which looks alot like the fire stop sealer used in bulkhead wire transits used in ship construction. (Read 'Firewall Penetration')
I notice that some builders have exotic firewall penetrations, and Van uses some basic concepts. The old Cessna 172 has a rubber grommet for each wire bundle or tube, pretty basic. A think a nice fillet of high temp RTV would be a reasonable improvement?

[mburch]

Originally Posted by SHIPCHIEF

Which RTV product did you use?

I used the regular red stuff, not any of the "ultra" types. I do use Ultra Copper to seal all my firewall gaps, since it won't corrode aluminum, but for this specific use I selected the red flavor since it looks the most like the certified stuff. I know that's not a very good reason but I'm happy.

mcb

[petehowell]

I found that Xylenes can be used to thin red RTV to make a true dip liquid. I might have found that tip elsewhere here on VAF.

Xylenes can be found at HD, Menards or the like. It is sorta nasty stuff, so use caution.

[randylervold]

I've heard you can also thin RTV with MEK to make such a dip. Haven't tried yet but been meaning to. Can anyone confirm that MEK works?

[scard]

I can confirm that MEK works just fine to thin red RTV. That is how I prepped all of my fire sleeve ends. At first when you start stirring in the MEK, it looks like it isn't going to do anything, but as you continue to stir, it mixes perfectly. You can produce the exact consistancy that you want with no effect on drying/curing. Smells bad, works great!

[mburch]

Originally Posted by scard

I can confirm that MEK works just fine to thin red RTV. That is how I prepped all of my fire sleeve ends. At first when you start stirring in the MEK, it looks like it isn't going to do anything, but as you continue to stir, it mixes perfectly. You can produce the exact consistancy that you want with no effect on drying/curing.

Good idea! I tried acetone but it didn't seem to do much (maybe I just didn't wait long enough). For my next batch I'll see how a stronger solvent works.

cheers,
mcb

[DaX]

As a kid I used to dip sticks into plasti-dip, light it on fire, and sling it onto things pretending it was napalm. It's probably a lot more flamable while liquid, but still not something I'd want to use anywhere a fire could occur!

[Jekyll]

DaX:

I know a good shrink...

My favorite was balsa airplanes, lighter fluid and a local high suspension bridge.

Jekyll