Use of denim in recovery protectors?

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Sooner Boomer

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I know there's a lot of stuff made with kevlar, but what about denim? It seems like it could be made "fireproof" with borax or sodium silicate. I've got several pairs of old blue jeans. I could use some simple stuff for both mod rocks and high power; chute protectors, tracker protectors, etc. How best to test the fireproofing?
 

Kelly

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Do both of these:
1) Light it on fire with a torch and see if it 'sustains' fire. If it lights and stays lit, you don't want to use it.
2) Test with an actual deployment charge - Put it in a rocket and ground test. Judge whether the amount of charring/burnthrough/etc. is acceptable to you.

And, report back!
(Sodium Silicate would make it too stiff/crunchy, wouldn't it? I've used borax+boric acid for other fireproofing uses, though.)
 

GlueckAuf

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I suggest you place a little mound of 4Fg, perhaps 0.2 cc, on the fabric and touch it off. Outside, and on a flame-proof surface, of course.

I think you‘ll find it burns through (just like Nomex and Kevlar fabrics do), but doesn’t melt (if the denim’s 100% cotton) or continue to combust...IF your chemical treatment works.
 

H_Rocket

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I’ve used heavyweight denim for recovery shields without any additional treatment. It seems to do every bit as well as most of the coarse weave Nomex that is commonly used. It will scorch and suffer the occasional blow through, but I get that with Nomex as well.
 

Steve Shannon

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Early in my rocket career I got a small selection of FR swatches. Most were denim. I tried using one once and it burned through more easily than the USFS Nomex pant material I was using. I’ve long since transitioned to heavier Nomex as is sold for rocket use. The fire service pants did work pretty well though for small rockets.
 

rharshberger

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Denim can work once properly treated with a flame retardant. I have made chute protectors from canvas treated with a borate mixture (boric acid and borax dissolved in hot water to get a higher concentration) the proctors are soaked in the solution for a few minutes the allowed to air dry. Nomex will last longer than denim/canvas as it still burns through fairly quickly.
 

Sandy H.

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I've used old blue-jeans treated with a borax based DIY flame retardant for about 3 years. It has worked well as far as I can see. I don't fly a ton, so maybe it will only last 5-10 flights, but cost is pretty much zero and therefore you make them bigger than required and get no real chute damage, in my case. Largest rocket was 4". I don't know if a bigger diameter tube/large chute would get sufficient cover from the size available in the pants leg. . .

I did test with a propane torch and it stopped burning almost instantly. They are a bit stiff, though. It might be interesting to test one I've used a few times in a rocket already using the torch again, just to see if the flights affected things.

Sandy.
 

Pete.D

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I use pieces cut from my old fire-resistant race driver's suit. There's got to be lots of those and other fireman's suits out there; check with racing organizations and fire departments? Suits are typically discarded after a period of years when they wear out or become obsolete, but the (usually) multi-layer fabric is still functional. Most are Nomex but there are other fire-resistant materials used.

Pete
 

rklapp

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My only experience was in high school I had a pair of new jeans. After washing, it had little fuzzies all over. I was playing with a lighter (because what teens do) and touched the flame to my pants I was wearing. A small line of flame went up and down my pants. Freaked me out but was fine and jeans looked better.
 

Sooner Boomer

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I just tried an experiment using treated (and plain) denim.

I mentioned it to a local Tripoli member. He replied:

"I used a cotton bag for the Vulcanite for years

It eventually got impregnated with enough stuff to char to nothing on the ground

Fortunately it didn't cause a fire or damage the rocket but the was nothing left of it but ash on the ground"

My experimental method:
I used a pair of worn denim jeans that were in good shape. I cut off one leg and removed all the stitching. I then machine washed the fabric (no softener). I cut three 6" square pieces. One piece was left plain (untreated), the other two were soaked in likely fireproofing substances. The untreated denim measure 0.035" in thickness, and weighed 10.9 g.

The two chemicals tested were sodium bicarbonate and washing borax.

A cup of tap water was added to a two quart pot and set on an electric element set on "HIGH" When the water began to boil, an excess of the chemical under test was added to the boiling water to form a supersaturated solution. After allowing the solution to regain boiling, the liquid portion in the pot was decanted onto the fabric sample in a rimmed plastic plate. The solution was allowed to soak into the fabric for 5 minutes, then removed and hung over the sink to drain. Each sample was hung in the garage overnight to dry. After drying, the borax sample weighed 28.8g, the bicarb sample weighed 23.6 grams.

Note; both samples became stiff from the dried chemicals, the borax extremely so. No attempt was made to bend or fold the fabric to make it more supple, other than described below.

Three 2" squares of common typing paper were prepared. One gram of FFF Goex powder was measured onto each square (it's what I had on hand). An unmodified Estes igniter was placed in the center of the powder charge, the paper was folded around it, and secured with masking tape. The individual fabric samples were folded into quarters, the powder packet inserted. The fabric samples were held closed with a plastic spring clamp along one edge.

The samples were taken outside to the driveway, and the powder samples ignited electrically by remote.

Restlts: black soot marks were observed on every sample. No samples showed more than cosmetic damage. No charring, no smoldering, no fire was observed on the samples immediatle after igniting the powder packets.

Conclusion: untreated denim may be suitable for limited use as recovery protection. Its condition would need to be inspected prior to each flight. The useful life may be extended by the use of common houshold chemicals as fireproofing agents.

Pictures:

powder packet with 1 gram of FFF powder
pac1.jpg


Estes igniter placed in packet
pac2.jpg


taped packet
pac3.jpg


test proceedure
test.jpg


results: sodium bicarbonate; washing borax; plain
result.jpg


 
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rharshberger

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I just tried an experiment using treated (and plain) denim.

I mentioned it to a local Tripoli member. He replied:

"I used a cotton bag for the Vulcanite for years

It eventually got impregnated with enough stuff to char to nothing on the ground

Fortunately it didn't cause a fire or damage the rocket but the was nothing left of it but ash on the ground"

My experimental method:
I used a pair of worn denim jeans that were in good shape. I cut off one leg and removed all the stitching. I then machine washed the fabric (no softener). I cut three 6" square pieces. One piece was left plain (untreated), the other two were soaked in likely fireproofing substances. The untreated denim measure 0.035" in thickness, and weighed 10.9 g.

The two chemicals tested were sodium bicarbonate and washing borax.

A cup of tap water was added to a two quart pot and set on an electric element set on "HIGH" When the water began to boil, an excess of the chemical under test was added to the boiling water to form a supersaturated solution. After allowing the solution to regain boiling, the liquid portion in the pot was decanted onto the fabric sample in a rimmed plastic plate. The solution was allowed to soak into the fabric for 5 minutes, then removed and hung over the sink to drain. Each sample was hung in the garage overnight to dry. After drying, the borax sample weighed 28.8g, the bicarb sample weighed 23.6 grams.

Note; both samples became stiff from the dried chemicals, the borax extremely so. No attempt was made to bend or fold the fabric to make it more supple, other than described below.

Three 2" squares of common typing paper were prepared. One gram of FFF Goex powder was measured onto each square (it's what I had on hand). An unmodified Estes igniter was placed in the center of the powder charge, the paper was folded around it, and secured with masking tape. The individual fabric samples were folded into quarters, the powder packet inserted. The fabric samples were held closed with a plastic spring clamp along one edge.

The samples were taken outside to the driveway, and the powder samples ignited electrically by remote.

Restlts: black soot marks were observed on every sample. No samples showed more than cosmetic damage. No charring, no smoldering, no fire was observed on the samples immediatle after igniting the powder packets.

Conclusion: untreated denim may be suitable for limited use as recovery protection. Its condition would need to be inspected prior to each flight. The useful life may be extended by the use of common houshold chemicals as fireproofing agents.

Pictures:

powder packet with 1 gram of FFF powder
View attachment 481779

Estes igniter placed in packet
View attachment 481780

taped packet
View attachment 481781

test proceedure
View attachment 481782

results: sodium bicarbonate; washing borax; plain
View attachment 481783

View attachment 481785
A boric acid (powdered roach killer) and borax dissolved in hot water is a common fire retardant solution and the ingredients are easily obtained from just about any hardware store. Its what I use on my canvas chute protectors, which I no longer use in favor of the nomex ones I make from Ebay nomex.
 

Sooner Boomer

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A boric acid (powdered roach killer) and borax dissolved in hot water is a common fire retardant solution and the ingredients are easily obtained from just about any hardware store. Its what I use on my canvas chute protectors, which I no longer use in favor of the nomex ones I make from Ebay nomex.
I'll have to look for it. Still looking for waterglass (sodiun silicate). There was a radiator leak fixer that was made from it plus fine metal powder - can't find it anymore.

BTW, almost all cellulose insulation, aka "dog barf" is treated with boric acid. Some are also treated with fungicide - probably want to avoid that.
 

rharshberger

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I'll have to look for it. Still looking for waterglass (sodiun silicate). There was a radiator leak fixer that was made from it plus fine metal powder - can't find it anymore.

BTW, almost all cellulose insulation, aka "dog barf" is treated with boric acid. Some are also treated with fungicide - probably want to avoid that.
The boric acid and borax is supersaturated (if I remember the term correctly) which is why the solution is mixed hot so a higher concentration can be achieved.
 

Sooner Boomer

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The boric acid and borax is supersaturated (if I remember the term correctly) which is why the solution is mixed hot so a higher concentration can be achieved.
I used boiling water. There was undissolved materiel in the pan. Crystals started forming almost immediatly as the fabric cooled. I can try wadding up the fabric repeatidly to simulate use and re-test. I'mm running out of "spare" igniters!
 

OKTurbo

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I recently found this on sale and bought a couple of yards to try as chute / shock cord protectors. It feels very similar to what I’ve been getting from rocket vendors.

89F93EF3-DC1C-4C51-A087-9DD49F2836BB.jpeg4C133E3F-F1B2-4069-89F0-B182247D3C7A.jpeg
 

jrap330

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Is 1 gram approximately the ejection charge in a Model Rocket engine? I thought I read here on TRF it was more than that. Because based on the fact that Denim is a heavy material...I would assume it would provide protection.
 
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