Hey everyone,

This is my first post but I thought it would be a proper time to join since I actually need some specific advice. I just attempted my first resin infusion from a mold I made a few weeks ago and everything was perfect (to me, but I’m anxiously waiting to be corrected haha) until I actually started my resin flow. I just wasted a whole bunch of resin and carbon fiber but not in an overly irresponsible way, I just think I lacked the experience to know what specific materials to use for my application. I think my bagging film is the problem but I’m open to ALL suggestions/burns/comments/laughs, whatever. I want to learn and perfect this, I can take the criticism. I have no idea what I’m doing haha. I’ve read many posts on here and all the write ups and videos about infusion and issues related for days on end before attempting this which I thought I followed closely and I’m sorry if my lack of experience is going to annoy anyone but I didn’t find any posts from anyone with as severe of an issue with bagging film as I just had. Anyway.. Here was my stack up.

-6-8 layers of partall paste 2 wax
-Sprayed 3-4 layers of evercoat mold release PVA
-4 layers of 3K 2X2 twill, about 1mm total dry thickness
-1 layer of green nylon mesh peel ply
-1 layer of Composite Envisions red Flex Flow media
-Stretchlon 200 bagging film. (As you can see the part/mold is deep with several tight radius’s and depth changes, so I wanted to ensure a tight fit with no bridging and I didn’t plan on baking it which is why I chose this film from everything I looked at.. this might have been the death of me)

So long story short I vacuumed down to about 27 in/Hg according to the gauge on my catch pot (my air converter pump thing that I bought is only rated for 26 in/Hg so I figured that was a good start). I valved off the bag setup and much to my surprise for about 50-60 minutes the bag held completely. I mean the analog gauge didn’t move at ALL. I presumably had zero leaks. I was quite proud of myself for a first timer. I for sure thought I was going to have a tornado of air from somewhere finding its way in but nope, held like a champ. That is, dry, at least. Problems started shortly after that when I started the infusion..

After the hour of being under vacuum I slowly re-introduced the pump to the circuit and unclamped the feed line to my freshly mixed/degassed resin cup (let it sit for 10 mins). The flow was decent as it entered the mold. It appeared the resin wanted to flow more in the left right direction but I guess that was because of how I positioned my flow media. (Not sure if there’s a way to get a more omnidirectional flow through the part? That wasn’t my main problem but I’m curious if anyone has any tips on that.) I had the resin flowing about 3/4”-1” a minute.

Here comes trouble.. As soon as about the middle third of the mold was resin saturated, POP.. hole blew open in the bagging film right in one of the round bottom edges, lost almost all vac. Grabbed my tape, sealed it off.. 2 seconds later.. POP.. another hole blew in the bag, other side, completely unrelated.. sealed that one off.. POP... POP.. POP... FML

And that’s how the next hour of my life went. Pops and tape and more pops and more tape. This damn bag blew holes in itself everywhere on the mold. Even in places that had no sharp material like along the smooth edges of the spiral tube up on the flange. Most of the blow through’s were around the radius’s and tight turns, but some just blew open in random flat spots as well. If you were walking near my garage today you would have thought a person with Tourette’s syndrome was making popcorn because there were that many pops and that many obscenities being shouted at the same time. It seemed that as soon as I sealed one off and the vacuum approached 25-26 in/Hg another hole would blow somewhere.

About 30-45 minutes into playing wack a mole and going through more than half a roll of tacky tape I waived the white flag. I couldn’t seal holes fast enough before another blew and then some of the holes I had sealed previously started to leak again. It seemed like the grey tacky tape wasn’t even sticking to the outside of the bagging film that well anymore. Maybe it was just all my sweat pouring off my face from the stress and anxiety as I watched $100 of carbon fiber and resin being thrown into the trash. I hadn’t even been paying attention to the resin flow anymore because I was panicking so much trying to seal the bag.. With about 75%-80% of the part saturated the resin flow had slowed so much because of the constant air leaks I figured at this point I should just save what little tacky tape I had left for the next run. I clamped off the resin, killed the vacuum, and went to go cry in the corner for a few hours.. I’m just kidding. I went to work. I was crying inside though.

So It feels to me like the bagging film just failed. Or I failed and used it improperly. OR I failed by using the wrong bagging film. Now it’s everyone’s turn to roast my methods. I’m hoping someone here can shed light on what caused the bag to blow me. The stretch-o-matic 200 or whatever it’s called is supposed to stretch quite a bit and I didn’t think I overdid it, but maybe I’m wrong. I even left a little extra slack before I sealed it down, but maybe not enough. Who knows. I thought I had everything down solid, but I was wrong.

Someone PLEASE help me decide how to approach this next. I already ordered another gallon of resin and some stretchlon 700 bag film because I read it’s much tougher and a little thicker than the 200, maybe that’s the key? I eagerly await all of your questions and instructions. Thanks in advance for helping me enter the wacky world of composites everyone.

PS I tried to upload an image of my mold but I couldn’t get it to work no matter what size I choose it just hangs on uploading forever. Doea anyone else have issues uploading from their camera roll?

Biggest issue is just the choice of bagging film really, nothing major. Strechlon and the other high elongation bagging films really aren't suited to infusion, for a number of reasons. Primarily, you can't actually take advantage of their stretch when you are infusing, because as the resin fills the chamber (the inside of your bag), the areas where the bag has stretched will slack off again and they will just fill with resin. 

Secondly, those films aren't actually compatible with epoxy. Best case, epoxy will stick to it, making removal a bit difficult. Worst case - and I do believe this is what has happened to you - the epoxy can attack the bagging film and make it porous, leading to holes. This depends on the specific epoxy you are using, some are harsher than others.

Personally, those films are only useful for vacuum bonding. Some other users on here have success with them and swear by them, but I certainly never did and I'm sure that is the difference in chemistry between the materials I use and the materials they are using. Each to their own, but I would recommend ditching the Strechlon and getting yourself some nice bagging film like what Easy Composites have.

Thanks for that information. I hadn’t seen anywhere specifically that the stretchlon films weren’t suited for infusion. It makes perfect sense that the epoxy attacked the bag since I had zero leaks until it was introduced. I was using the infusion resin 4500 system from Fibreglast, but I just ordered a gallon of infusion resin from composite envisions since it’s way cheaper. I originally purchased everything from fibreglast before I found CE. I saw they have several standard bagging films. I think I’m going to call them today and pick their brain about which one to use.

Do you have a suggestion for a specific film that I should look into? I also have a package of model 3578-A polyethylene bagging film from fibreglast, I had added it to my original order as a backup. It’s very cheap though and I’m not sure if I should attempt it with that or wait and get some good stuff from CE first.

+x

 

N2CFRI - 9/9/2020 2:19:12 PM

Thanks for that information. I hadn’t seen anywhere specifically that the stretchlon films weren’t suited for infusion. It makes perfect sense that the epoxy attacked the bag since I had zero leaks until it was introduced. I was using the infusion resin 4500 system from Fibreglast, but I just ordered a gallon of infusion resin from composite envisions since it’s way cheaper. I originally purchased everything from fibreglast before I found CE. I saw they have several standard bagging films. I think I’m going to call them today and pick their brain about which one to use.Do you have a suggestion for a specific film that I should look into? I also have a package of model 3578-A polyethylene bagging film from fibreglast, I had added it to my original order as a backup. It’s very cheap though and I’m not sure if I should attempt it with that or wait and get some good stuff from CE first.

Hi,
I've done my first 16 foot boat infusion last saturday and is was more or less successful, only messed up on the gelcoat brushing it  :-(
Somewhere here I read to use  nylon bagging film becauswe epoxy does not stick to it and you can save the peel ply
the standard EC nylon (red) bagging film I used was easy to put down with gumtape and the price is very competetive
good luck

Thanks, Torsten.

I was looking at that film as well. I just ordered several yards. I guess I’ll be prepping the mold again soon and pleating the hell out of the extremely oversized bag.

How do you all position/lay your flow media? Is there a wrong way and a right way? Is there an up side and down? I noticed that when I started the resin flow the resin quickly moved left to right but not so much in the forward and back direction which isn’t great in my mold as it’s almost a square shape. I’d like the resin to reach out more uniformly. I had a full circle spiral tube around the mold flange for vacuum so the pull was even. I think it was just due to the direction of the channels in the flow media.

Any suggestions there?

Proper/regular flow media shouldn't have a flow direction, that isn't how it works. Knitted flow media and shade cloth (what some people use instead of flow media) can have a bias in one direction because it overlaps itself and so creates a bigger void for resin to flow into. Im not sure if that was you are using, but normally the red flow media is for larger infusions and the green is for smaller. But different brands change it up, just to confuse everyone haha.

Flow direction shouldn't hugely matter for small infusions anyway, you dont need to overthink that. Just have a good 2-3" brake zone at the vacuum end of the layup where you leave the mesh short of the outlet and just use peel ply or breather to continue the air path. This will choke the resin flow so the the rest of the part will wet out before the resin starts to evacuate the chamber. Or get yourself some MTI hose - this is great for learning the ropes and may save you some stuff ups.


As for bagging - pleating is not as hard as you may think. Just make your bag 1.5-2x the foot print of your mould (so use a measuring tape to measure the full LxW of your mould including the deepest sections). Go oversize rather than undersize, trying to skimp on bag will cause leaks. 

Thanks, Hanaldo.

I was using this stuff from CE..

https://compositeenvisions.com/flex-flow-stretchable-flow-media-30-wide/

I didn’t think regular flow media should have a bias flow direction either which is why I thought I may have laid it upside down or something. I also thought it may have to do with the stretchlon film I was using filling voids in the flow media that it should be.

I guess I’ll make a nice break zone and try again when my new bagging film comes in this weekend.

I use the tyhe EasyFlow infusion mesh which works fast with epoxy IF2 resin and have a infusion spiral for the resin  and multible vacuum connectors without spiral so I can regulate the where the vacuum is pulled and stop the catch pot filling up.
With the easyflow I did not notice any flow direction no matter how you put that in, it was the vacuum extraction points which helped most.

Thanks everyone.

I have never used any of these materials before so I wasn’t sure if that was normal or not. I have a feeling that the stretchlon 200 was so flexible that it sucked down into the flow media and may have caused the unusual flow patterns.

I will look into the MTI hose too. I’ve already ordered the standard red nylon bagging material from CE, waiting for tracking. I want to make sure I get anything else I might need to make sure this next attempt is successful.

I have one more question for you all.. I used 3K 2X2 twill for this layup. 4 layers made the overall thickness about 1mm when I pulled the failed part out of the mold tonight. Each dry layer measures about .25mm thick. The individual sheets of fabric are very thin and the weave is disturbed quite easily when I’m working it into the mold. When I first attempted this mold without resin infusion as a manual layup I was using a yard of carbon fiber that a friend gave me. I just measured some of the scraps from that piece and they measure about .75mm thick without smashing the micrometer down on the fabric too much. Each individual “strand” or bundle of the weave in one direction measures about 2.5mm wide on the thicker stuff, VS about 1.5mm wide on the .25mm stuff that I just used. Does anyone know from those rough measurements what the “weight” model specifications of the thicker carbon I have here is to order?

I’d like to order some more of that heavier stuff for this next go. Even though the infusion failed I can see the finished product well and I didn’t like how the weave looked at all in the bends compared to how the heavier stuff laid in the mold the first time. It was also much easier to work the heavier stuff into this mold than the ultra thin stuff that I accidentally ordered.