Carbon fiber blues: vacuum resin infusion failures

My latest obsession relevant to this forum, has been making trash out of carbon fiber and epoxy. True to my nature, I set out on this endeavor with zero experience in vacuum infusion, and rather than take baby steps, I dove right into the most technical and challenging method of composite fabrication. I’ve read tons of threads, and publications about the method, but I just cant seem to get it right. So I’m creating a topic specifically about my expensive failures.

Vacuum resin infusion is fuc*ing HARD. Any number of things can screw everything up and waste time and materials. So why do I do this method vs hand-layup or regular vacuum bagging? Because I am a difficult person!

I’m using West System 105, and the 207 hardner. I’m gonna go ahead and get the 209 extra slow hardner for science, maybe the extra pot life will allow better wet-out

So here are some of the most significant problems I’ve had thus far.

  1. Moving the epoxy fast enough to cover the part
  2. Achieving a full wet-out of the fabric
  3. Finding all the leaks!!
  4. Mixing enough epoxy
  5. Laying the bag effectively
  6. Flow mesh puncturing the bag :angry:
  7. Keeping shit where I put it

The epoxy always seems too thick. I got decent results using denatured alcohol to thin it. I tried heating the epoxy as well, but then it gelled too fast and didn’t travel throughout the part.

Hahaha, this is so frustrating Pictures and setup coming soon, tips and tricks welcome! Here’s the best result I’ve gotten so far Its 12k 200gsm 2x2 twill with spread tow yarn and two layers of 24k 815gsm beneath it


i do love me some good ol carbon fiber trash. i hear it makes the garbage man happy


And it looks so easy in all the YouTube videos.

I want to give this a go one day, even picked up a vacuum pump on eBay for $50 months ago. The what didn’t work threads are often as useful as what did work so definitely interested to see what you’ve done :+1:



pics or it didn’t happen!

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As soon as I get home from work!

Edit: Screw it, I’ve got a few already: Plexiglass mould and layup

Failed wet-out


Brush the resin on first and slow hardener works better. That epoxy you are using wont give the best finish. Doesnt set clear bit a little opaque. Doesnt bother me, I use that one as well. Board doesnt stay clean long anyway.

Im currently using the clear hardener, 207sa. Have you used that one specifically?

i always use slow hardener, and also for infusion you need to use special infusion resin. its less viscous.


The West system has a very similar viscosity to that of the fiberglast system 2000 epoxy which is right around 1000 cps at 72f. While I was deciding on which epoxy to go with, I did a fair amount of compairing this property and they all seem to be pretty close to the same viscosity. @MasterCho uses West system as well, iirc. Perhaps he could weigh in here as well😉

I am pretty sure I’ve read everything MC posted on infusion here but I probably missed a couple of things. My research seems to suggest that diluting the resin with acetone or denatured alcohol is effective, but im not sure which is the better choice…

If this is your first time, give a try few more time, you’ll get it. :grinning: A small project like this, it shouldn’t take more than 40min to infuse the resin into the bag. 207 (working time 100-120 min) is more than enough.

From the pictures, It doesn’t seem anything wrong but I suggest to do the vacuum test before the infusion.

You shouldn’t see any air or bubbles left behind.

I hope it helps.


Id reccomend practising with fiberglass and not carbon, a lot cheaper

Also use just the amount of resin so it sticks do not splash it with a half of litre of it

How is the flow mesh is puncturing the bag? It shold be soft Also put some paper toweld to soak up the extra resin Also fuck the slow hardeners use the fastest one and put a shit ton of it I remember the days when polyester resin was much better, It would harden in 15minutes and it didnt crack on the abuse of speed boats

Definitely sticking to slow hardeners. I use a heat-pad on the mould to expedite the cure once infusion is complete.

@MasterCho I always do the vacuum test before infusion, just as you said in your other threads!! I actually do everything based on your instructions. Don’t worry, I am incapable of giving up on something that I have not figured out. I’m particularly interested in what you use to dilute the resin, if you so do. You live in Chicago, right? what do you do to mitigate the cold temperatures?

Why, using the slow ones will just give you a little bit more of flex With the faster ones it will flex less, in which i do not see a problem :slight_smile: If you put a shit ton of the catalyst it will harden like 1/5th while you are putting more layers on and it will move less so its easier, at least from me…

Once the epoxy is set, it is as permanent as plastics get! Hardener is only a catalyst, the resin is the “concrete” and, as long as it is allowed to cure it will achieve the same properties regardless

dude you’re 15 :rofl:


I remember when I was really young like 5years old and I was working on boats with my dad he bought barrels of polyester and stored them for a long time, that was around 2003 or so and that polyester didnt have the hardener mixed in it, it was pure resin Also Im not 15 :wink: Im 15 and a half bitc*h jk

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if you’re 15, you would’ve been 1 in 2003 :thinking:


I never heard of diluting resin before. :thinking: it might weaken the strength of it… not sure.

I have been using “HIGH IMPACT/HIGH TEMP VACUUM INFUSION EPOXY 3:1 325° F” since I am making car parts in the engine bay, I have had a good result so far.

Check this out.

Yeah, It’s really cold in Chicago.:persevere: I set up a table in the basement.

Next time, please upload a video of how the resin flows so I can tell you better.


nope never used that one.


As it turns out, West System epoxy resin is fairly thick stuff, even at elevated temperatures. To be clear, it is not an ideal resin for infusion due to it’s viscosity. Since I’ve already spent the money on the 105-a, I set out to make good use of the investment. I figured that using the 209 extra slow hardener would allow for a longer pot life at elevated temperature, which would both significantly reduce the viscosity, as well as cut the pot life too. While decreasing viscosity is great, decreasing pot life is bad for infusion, so the theory is to heat the mold with a heating blanket, and hope that the mix would saturate the fabric fully, and still flow long enough to wet out the whole piece. Turns out that was good thinking.

The WS 209 needs a warm climate to set. As it’s only been mid-60’s F here in San Diego lately, the heat blanket should also expedite a proper cure of the epoxy in addition to improving it’s infusion capabilities! So here’s what I did from start to finish:

Made a mold out of plexiglass using a heat gun:

Waxed after taping the boarder.

Layup and bagging:

Vacuum leak test: passed! Full wet out- SUCCESS Mold nestled nice and cozy on top of heat pad, insulated with a bath towel

Now it’s just a matter of time to see the fruits of labor. I’ll update once cured!! SO EXCITING

Celebration beer(s):