Vacuum Bags: How To Find, Fix, and Avoid Leaks

Vacuum bagging is an integral part of many composites manufacturing processes, including prepreg, resin infusion and conventional vacuum consolidated hand-layup but getting vacuum bags to seal properly and reliably can be difficult and frustrating, especially for those relatively new to the process.

In this video tutorial we use our many years of experience of vacuum bagging to go through all the possible causes of leaks in vacuum bags, how to avoid them in the first place, how to test for them, how to locate them and how to fix them. We will also discuss when to give up and make the decision to re-bag a part.

Most of the tools and equipment used in the tutorial are available from Easy Composites and are listed on the video's Project Page in our Learning Area:

[TheSturle]

These videos are like having a dad or granddad learning you all the smart hacks in the trade.
This is one of the most important films you have made. Kudos for not only creating fancy videos for chasing views, but genuinely useful ones as well.

[MattPuccini]

This definitely is the best composites channel on YouTube, great job guys

[MatthieuLibeert]

An important thing to add while using a digital gauge is that moist in your lay up might cause a 'vacuum leak' as water is boiling under vacuum causing the digital gauge to raise over time. you might think you have a small leak, but everything is fine

[ChuckThree]

This video won’t get the views, but it’s probably the most important/useful video yet of this incredibly educational channel. Thank you EC!

[brxnah]

The stethoscope trick is genius. I bought a cheap one and I'm letting other people in the shop use it. It was taking me forever to find any leak whatsoever. It's a great teaching tool because you can look at that area and figure out why it didn't seal. It's hard to hear very small leaks if it's not quiet in the room, but larger leaks that make the vacuum drop within a few seconds are clearly audible. Don't be fooled by what sounds like a vacuum leak near the port as if air is getting into the bag, that port is sucking it out which won't be silent.

[MatthieuLibeert]

must have been hard creating those mistakes on purpose to make this video while being experienced sealing bags :D thanks for the great video!

[tunedone]

The only one channel that I'm waiting for videos. Thanks for your work and WE NEED MORE VIDEOS ON CHANNEL!!! At least 2 on month.

[perro]

I've learnt hugely from your videos. Many thanks. It is very true about a leak. Don't even think of doing an infusion unless you have a full vacuum. Here are my 2 cents learnt from experience. I am making skis using vacuum infusion. My core is a porous material. So it would take a couple of tries to get a vacuum. Initially it will appear as a leak .... but it is just the pump pulling the air out of the core material. So be patient, that needle will eventually settle. I use a primer to first seal the porous core, at least 2 coats, but in my case, I WANT resin to get in at the tip and tail of my material, so I leave those areas exposed. I am getting good results with water based acrylic paint. On the first coat I thin it out a bit for better penetration. Don't forget the pump is powerfull enough to separate water. As a beginner I also do a test for the amount of time my resin will take to cure. I don't settle for half an hour. Half an hour for me gives me a 'warm feeling'. But I usually do 3 to 5 hours as sometimes it takes a while to suck the air out of the system. That for me is working well.

[sailsoon]

Thank you very much for passing on your knowledge! I was looking for a channel like yours for years. I hope your effort is rewarded with lots of happy customers.

[stevesloan]

I know Ill be watching this again down the track.
Awesome work!

[mateszentes]

You guys made an excellent job again. I can't said enough how grateful i am for the information what you gives us (for free). Soo thank you so much Easy Composites.

[jennaanderson]

Man this is a super duper awesome video tutorial thankyou for sharing your knowledge with the world for free

[ComFrag]

One more tip: In case you´re using a vaccum hose for your drop test - don´t clamp it right next to the bag. Place it at least 10cm away from it. This way you can clamp the line a bit closer towards the bag after you´ve performed your drop test. Clamping (cheap) polyurethane vaccum lines damages them - this can cause a leak, which you would include in your system otherwise. I wouldn´t recommend clamping down on the same spot more than once as it will damage your line even more - making the leak worse.

[nonamesareavailabe]

you guys are really doing such a good job with these videos.

[CarbonWorkshops]

Iv just spent the last 4 years learning all this with trial and error and error again! And now you make the video 😂

[loganmarriott]

Paul, I should have sent you the bloopers clips as I think I’ve made all those mistakes. Great job

[Rodrigo]

I’ve learned a quick trick for inserting the resin feed line when bagging. When I’m doing this I cut the chamfer too but I put the sealant tape right around it so once it penetrates the bag (I don’t always use the scissors) its immediately sealed
Everyone who makes vacuum bags for resin infusion, try this out, checks if it works for you and save you some time 💪🏼 Great job and have fun, it’s a very cool industry 😄

[ComFrag]

A lesson I´ve learned from working with composites as a Formula Student engineer the past two years: Don´t use old sealant tape that has lost its tack. We had some sponsored tape, which had expired over a year ago when I started - now that we had to buy new rolls I don´t ever want to go back. But don´t be mistaken - new sealant tape can also be too tacky and make it difficult to fix any missalignment with the bags perimeter. When using such tape I would advise to use it in a climate controlled room as warm weather can make it nearly impossible to work with it.

[b.w.oostdam]

You are so right, for my small hobby (RC) projects, I always find it to be very very difficult to get my vacuum-sealing anything close to perfect. Totally perfect has not been achieved by me yet 🙂

[Abrora]

As usual good, comprehensive and right explanation! Thanks!