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RocketPoxy + chopped carbon fiber

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julienvary

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I love RocketPoxy, I can do "good enough" fin fillets in a hurry, while being half-drunk.
IMG_7563.jpg
Hey, I have chopped carbon-fiber from Wildman taking dust.
RocketPoxy claims they have already the best fillers, so no need for extra CF, but let's try anyway! A pinch of CF for the first try :
IMG_7567.jpg
FullSizeRender.jpg
Hum... Far from perfect, but let's add much more CF for the next batch!

FullSizeRender2.jpg
Ok, that was a terrible idea.

And for your information, while the CF filled RocketPoxy is a tar more rigid than the plain one, it is also way more brittle (from my leftovers)
So, stick to the RocketPoxy instructions, add nothing to it :)
 
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REK

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Did you not use like a dowel or something to make them round and uniform?

Your first set of fillets on the left looks like it has air bubbles, which indicates you mixed and applied without waiting. When it comes to gluing you got to be patient and not rush it.




Alexander Solis - TRA Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 

julienvary

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> Did you not use like a dowel or something to make them round and uniform?
I did, but for the last one, it was like to apply hair clog : it was not breaking down small enough.
The second one : yeah, this one could have been actually similar to the first one, but I my dowel removed too much, and since it is a MD build going mach 1.6 without TipToTip, I wanted some extra epoxy (and applied some more after having removed the tape...)

> When it comes to gluing you got to be patient and not rush it.
Nop, because it is done past midnight, and my kids are starting to scream in less than 6hours! (ref: I can do "good enough" fin fillets in a hurry )

And needless to say, if I wanted to go for the display show, I would have scrapped the 3rd batch, and quickly made another epoxy run without the hair clog.
 
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REK

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> Did you not use like a dowel or something to make them round and uniform?
I did, but for the last one, it was like to apply hair clog : it was not breaking down small enough.
The second one : yeah, this one could have been actually similar to the first one, but I my dowel removed too much, and since it is a MD build going mach 1.6 without TipToTip, I wanted some extra epoxy (and applied some more after having removed the tape...)

> When it comes to gluing you got to be patient and not rush it.
Nop, because it is done past midnight, and my kids are starting to scream in less than 6hours! (ref: I can do "good enough" fin fillets in a hurry )

And needless to say, if I wanted to go for the display show, I would have scrapped the 3rd batch, and quickly made another epoxy run without the hair clog.
Well dont do it past midnight silly lol. This glue requires patience. Bet you didnt read carefully, but the instructions state to wait at least 30-45 minutes to insure all airbubbles are gone. Also after 30-45 minutes the rocketpoxy will be at a consistancy of peanut butter. This helps in shaping fillets into that round, uniform shape that we all admire.

Dont rush, be patient and dont do this past midnight lol.


Alexander Solis - TRA Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 

claytonbirchenough

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So has anyone successfully used chopped or milled carbon fiber in Rocketpoxy?

I'd like to hear about others experiences also...
 

Salvage-1

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+1 ... mix the RocketPoxy together then wait about 30 mins before using it as fillets.
 

AdAstraPerAspera

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Well dont do it past midnight silly lol. This glue requires patience. Bet you didnt read carefully, but the instructions state to wait at least 30-45 minutes to insure all airbubbles are gone. Also after 30-45 minutes the rocketpoxy will be at a consistancy of peanut butter. This helps in shaping fillets into that round, uniform shape that we all admire.

Dont rush, be patient and dont do this past midnight lol.
Instructions?!? Mine didn't come with instructions...

Can anyone snap a pic and post them?
 

markkoelsch

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I bet the fillets with carbon are strong. This is why epoxy filler was invented.
 

REK

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This is on page two from the data sheet that dixon posted.

Application: Apply mixed epoxy to the area to be bonded. Even though the material is a paste it will flow a little bit after applied if used right away. If you do not want any material flow at all when applied this can be accomplished by waiting approximately 15 to 30 minutes after epoxy is mixed before using, this will allow the epoxy to stiffen up and retard flow.


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Zebedee

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Read the title, thought "That is not going to go well"... :)
 

Nick@JET

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Maybe John Olevich will answer, it is his epoxy. As you already know, No need for chopped carbon fiber for strength with RocketPoxy , just to concur with others.
Other epoxies yes, Bob smith, West etc...and just a pinch.
 

AdAstraPerAspera

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This thread also reinforces my personal rule about not touching rockets with any alcohol in my system...
 

Rob702Martinez

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> Did you not use like a dowel or something to make them round and uniform?
I did, but for the last one, it was like to apply hair clog : it was not breaking down small enough.
The second one : yeah, this one could have been actually similar to the first one, but I my dowel removed too much, and since it is a MD build going mach 1.6 without TipToTip, I wanted some extra epoxy (and applied some more after having removed the tape...)

> When it comes to gluing you got to be patient and not rush it.
Nop, because it is done past midnight, and my kids are starting to scream in less than 6hours! (ref: I can do "good enough" fin fillets in a hurry )

And needless to say, if I wanted to go for the display show, I would have scrapped the 3rd batch, and quickly made another epoxy run without the hair clog.
99% of chopped cf is made for extrusion or plastic/polycarb molding. Which is perfectly fine to use and works just as good for anything you need. There is binder on both sides that breaks down with heat or stir for a bit longer with friction on the sides of the cup. Which is also nice so you can control the density.
It will get the job done for sure, but is not specific for room temp exotherm epoxies. You have to mix it a bit longer to get it all broken up. Chopped 6k tow with a polymer binder on one side of the tow that will mostly dissolve in resin/epoxy, as it costs a bit more and not very common at all and is delicate.
 
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AdAstraPerAspera

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This is why you need a purpose made chopped CF. 90% of chopped cf is made for extrusion or plastic/polycarb molding. So there is binder on both sides that breaks down with heat.
It will get the job done, but is not specific for room temp exotherm epoxies. You would be better off with a purpose chopped 6k tow with a polymer binder on one side of the tow that will mostly dissolve in resin/epoxy. I have used chopped cf, milled cf and kevlar and my own chopped 6k kevlar with polymer on one side and it works like you imagine it to be with Laminating Resins, Rocketpoxy, 30 min, 15min, CA etc.... Kevlar and jbweld are great for MMT root fin surfaces. Also mixing rocket poxy with powdered aluminum or any epoxy helps with keeping the area a tad cooler as it dissipates heat a bit.
I'd this why when I tried mixing chopped CF it never seemed to mix in fully? It always seems to still be in the clumps it came in, no matter how much I mix. Some mixed but not all. Not even close. That wasn't even with rocketpoxy....
 

Rob702Martinez

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What you hve will work....try mixing in a shallow contanier, like a small paper plate or on butcher paper.
When you are adding it, do it in smaller increments. Take a pinch and break it up by rubbing your 2 fingers together as you are sprinkling it in. That should give you much better results.
 

AdAstraPerAspera

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That was with Aeropack structural and Wildmann 1/8"CF, not the milled stuff I just got from you. But I'll try that method next.
 
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ksaves2

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My take on chopped fiber is on high grade adhesives like Proline 4500 or Duralco, totally superfluous. If the fibers are arranged randomly, I doubt there is much added strength plus too little of the fiber and it is dubious to think it adds much. Too much fiber and the bond is going to be weaker as the fibers might not be whetted out completely with adhesive. Another thing I've observed is the viscosity of the adhesive has to be correct so the fibers stay suspended and the mixture flows to a reasonable degree or at least can be shaped into something reasonable.

Julien shows that quite aptly in the photos above. Too thin of epoxy and one gets random furballs without an even distribution through out the fillet. I've done that on a modroc experiment build. Is there a happy medium where it adds strength? Sounds like a maximum/minimum problem as far as the amounts of fiber to add and having the right viscosity of epoxy. I brand it a PITA. As Dr. Drake Damerau would likely say, "In God we trust, all others bring data."

Anyone know what's happened with the good doctor? The rocketry materials site he authored is gone and only on the Wayback Machine: https://web.archive.org/web/20150321210536/http://www.rocketmaterials.org/
I found a Linkdin page he writes on 1/2016 he was working in China for a company for 6months up to that time. Wonder if he came back yet or has or plans to completely drop out of rocketry. His site is still useful for
comparisons but alas, no data on chopped fiber. Kurt
 

AdAstraPerAspera

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I haven't seen Drake in years, used to see him at launches fairly regularly before my old club bit the dust, then saw him once a few years back at MDRA, but I can't even remember when that was.... I didn't even realize he left the country.
 

ksaves2

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I haven't seen Drake in years, used to see him at launches fairly regularly before my old club bit the dust, then saw him once a few years back at MDRA, but I can't even remember when that was.... I didn't even realize he left the country.
This is the latest link I've found: https://www.linkedin.com/in/drake-damerau-phd-364150a

Perhaps work is getting very involved and entails alot of time or like some, they leave. I gave up R/C when I moved and no longer had a flying field I could walk to and lay out an 800 foot high start for sailplanes or fly gas planes or fly (not very well) gas helis.

I think there was a profile of him in the very last issue of Extreme Rocketry. Kurt
 
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