Large diameter CF tubes - a few questions

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#1

I would like to roll some large CF tubes ranging from 8" to 14" outer diameter with about 0.06" thick wall. I have already sourced my materials, resins, epoxies, hardeners, etc from Soller Composites. My questions have to do with vacuum bagging. I have watchd several how-to videos but none of them deal with large tubes like I will be working with.

#1 - How powerful does my vacuum pump need to be?

#2 - I am worried about the actual bagging process with tubes this large. For example if I’m working on a tube that is 12" x 48", can I still tape the bagging material to the working surface, slide the tube inside, and proceed as shown in all the videos and get a good uniform result? I’m worried that the seams will be irregular. Is there a better method for large tubes?

#3 - Are there any special considerations when working on a tube this large?

Thanks for your help.

#2

The pump itself should pull to a high vacuum level, .9 atm at least. The amount of consolidation force is what’s important. If you have a leak free bag it’ll take a while to suck down but it’ll eventually reach it’s maximum level.

I’m not sure how vacuum bagging for tubes scales but the “better” process for large tubes is filament winding but it requires special machinery. You could try using a bladder and an outside mold but it sounds like you need multiple diameters and I’m also not sure how bladder molding scales as well.

#3

Large diameter tubes are easier than you would think. Make a large envelope type bag and make it about 2.5 to 3 times the length of the tube (depends on the part and mold). Put the mold with the carbon, release film, and air weave an all in the bag and invert the extra length of bag you made and push it through the inside of the tube. Pull your vacuum and cure.

#4

Thanks I appreciate the feedback. I’ve gotten quotes from shops that are equipped for filament winding but the cost is prohibitive for my market. I can’t retool for filament winding myself so bagging is my option.