Just got done watching more video from the Jungmeister crash at the Missoula Montana airport yesterday. I feel terrible for the family and friends....and maybe this isn't the place to say this...but that's never stopped me before. haha

After viewing the pictures/video of the wreckage....why would anyone cover with dope/fabric? It's gone, and it was gone that fast!! (at least that's what the witnesses said...) Polyfiber, and Stewarts (and probably others... I'm not farmilliar with them) are both fireproof...why would you not utilize that safety feature??? It just never made any sense to me. Sorry .... now back to the regularly scheduled conversation.
John

I have yet to see any items referencing a crash at Missoula.

You did inspire me to see that polyfiber is indeed fireproof; a search for Stewarts did not come up with anything so reassuring - maybe I did not use the right search terms. If I live long enough so that I need to worry about recovering my Maule fuselage and empennage, thank you for reminding me of choices and consequences.

A very brief but oh so enjoyable acquaintance lept to his death from a Thunder Mustang when it caught fire after takeoff - in that horrible situation, I don't know whether I would have the presence of mind to remember that I have smoke hoods and a halon extinguisher within reach behind the copilot's seat- but I do try to run through the scenario before takeoff and I do gently nudge every pilot I talk to for any length of time towards having extinguishers and hoods even if it is not their own plane (nag nag): I mourn my acquaintance.

I believe the reason that some of the old grizzled graybeards will still use nitrate and butyrate dope... and even cotton occasionally... is because the ye olde tyme craftsmen can get either a more drum-tight fabric tension, and/or it is easier and faster for them to work during installation. Cotton being a natural material is easier to make it "sing and dance" around strange shapes, and do miraculous things in the right hands. Nitrate dope (cellulose acetate nitrate) is sticky, adheres wonderfully to the structure, shrinks and tautens incredibly, etc. The old school crop duster outfits that did a LOT of fabric work on airplanes every year, and had to get the job done right yesterday, were apparently the last group routinely using cotton and Nitrate on a regular basis. Maybe some of the older AG pilots on this forum can verify that or correct me if that is not true?

But then there's that little Hindenburg problem. The nitrate-doped linen fabric burned almost as fast as the hydrogen did. There were a LOT of survivable crashes that became not survivable because of Nitrate dope, and aluminum pigment powder (the stuff they fireworks out of).

So a long time ago they changed to Nitrate for the first few coats on fabric, and went to Butyrate dope (cellulose acetate butyrate) for the outer four or five layers, because it was somewhat less flammable.

Ray Stits developed a much safer system in the 1960's. It wasn't "fireproof" but they were able to certify it as "will not support combustion". Lives were saved.

Nowdays they have these really safe water-based systems. I haven't used them yet, but our EAA chapter is using Stewart Systems on a chapter project and it looks like it has a lot of advantages over even my old favorite Stits.

All that said, if you are restoring a 1930's era Bucker, and you are trying to do a really accurate museum-class restoration, you have no choice but to take the risk of using the historically correct but less safe materials.

EZFlap,

You are partly right about the old nitrate, silver, and butyrate on cotton covering. It is actually harder to get tight. But that works out the way the show plane guys want. It takes many, many coats of butyrate to tighten. By the time they have say fifteen coats of butyrate on the much tighter weave of cotton, they get the very tight, very shiny, very slick show plane look. The safety issue is that they are for show, not flying. So they get very little exposure to incidents and accidents.

No, crop dusters had no use for cotton once Ceconite came on the scene. Tack the stuff on a bit with cheap high school grade common glue, iron it tight as a drum, use the simplest and cheapest process currently available, and go back to the field soon after a crash.

As for cotton, which the old guys called linen, I flew a 64 model Callair that had original factory linen in 1982 because it had never crashed. Crop dusters don't change fabric out just for looks. You could put your finger through the top of the wing anywhere. Only the County Road Department Yellow paint kept it from melting. Doesn't take much to change the direction of air. The next year another pilot got the wheels down in corn and turned it over. It finally got new polyfiber.

contact

Well, one reason for dope and linen might be because it's pretty fun to apply, especially with the hangar door closed. At least I think it is. I don't really remember so well.

I have to agree with contact.... simple and quick was where it was at when I worked for a crop spray outfit. But we converted to Polyfiber ASAP. I think dope/fabric was a bunch more work than the synthetic processes. I will conceed that you can hide a multitude of sins with the dope systems... just build more and more.
I just can't see any sense in having that worry too... there's so many safer ways to go. I also find it ironic that the feds are so wound up on interior materials being fire resistant, yet don't even bat an eye about nitrate/butyrate dope. Like was said, I've seen a few crashes that went from survivable to fatal due to fire. It just seems such a waste.
JH

Wear the nomex Uncle Sugar gave you. I had it on in every crash. Never had a fire. Guess it works.