Instructables
Picture of Vacuum Bagging Basics
I must preface this entry with a citation for a homespun vacuum source that saved my bacon in this exercise. DrCrash has a great solution using nothing more than a hardware store bicycle pump for this project, as there was no way I'd encumber my little apartment with an unwieldy electrical unit.

Vacuum bagging is a commonly used technique in composites, and for good reason. When done correctly, your part will have a nice, uniformly distributed compression about the surface of the layup. This in turn helps to minimize any voids (e.g. bubbles and wrinkles) in the buildup of layers. Also, when used with a porous substrate made of peel-ply and breather-cloth as we'll see, it assists in having the optimal ratio of resin to reinforcement (e.g fiberglass, or carbon fiber, or Kevlar) by squeezing out the excess.

The project is quite simple for illustrative purposes. I'm making a small container from a mold of a nice tea container lid. I'll go over the steps to make this part, but the vacuum bagging phase is what this topic is about, so we'll be delving into that a bit more thoroughly.

First, a few suppliers that I've had quite good success with:
Fibreglast dot com - Lots of supplies for the intrepid.
Aerospace Composite Products - They also had the check valve and bag attachment and 1/4" neoprene tubing used in DrCrash's vacuum tool, and very personable customer service.
Tap Plastics While they don't have much for vacuum bagging, it's still a worth while source to mention with all their instructional material and from my experience, good staff.
USPlastics Is also well known supplier.
Both TapPlastics and Fiberglast have some very good instructional material that is invaluable for someone learning about new techniques.
 
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hardlec3 years ago
Is there a picture of the finished item?

I have an adapter for my air compressor that pulls a vacuum. Would this be useful?

Not trying to be inappropriate, but: Why would a zip-lock bag fail? I ask this to learn, not to try to make an actual project with a zip-lock bag...
shortshift (author)  hardlec3 years ago
You could try a ziplock but my guess is that it would leak ...even a slow leak would defeat the purpose of the exercise. It really is a PITA...
I'd try sealing it with "tacky putty"---the removeable clay-like stuff that you put posters on the wall with.
akmark1 year ago
Great write-up. I'm ordering supplies as we speak... but what about the bag connector / port? What specifically is that tool (i.e. McMaster-Carr Part no.) or where did you get it? Thank you!
akmark akmark1 year ago
Ahh, I found it on the Fiber Glast website. Apologies... but it's $39.99! There must be a more economical way to connect the pump to the bag.
dmanske2 years ago
Thank you for taking the time to do this.

The sealant tape you are showing, looks like 'Butyl Tape'. I have a roll of it in my basement. It is available at any good building supply that sells metal roofing. Quality metal roofing companies (e.g. Everlast Roofing) require butyl tape during the installation along gable end edges between the rake flashing and the metal sheet. Just ask for butyl tape at a good building supply place. You may not have good luck at a big box store. Just a heads up.
I f ya want to go to the trouble you can use a A/C compressor from a car then all you'd have to do is add a motor of somekind, they already have valves installed and you can pull about 27 lbs( which i believes varies according to your elevation!) Tks for this instructable been wondering about this very thing!
shortshift (author)  tazmaniac_377524 years ago
hey tasmaniac - ya you are right.  I actually found this pump works okay for really small things but for larger projects like the gas tank i made for my moto, it just wasn't drawing the air i needed to handle a large moulding.  if you can find an air compressor kicking aruond, hack it!!!

tojours,
Adam

LOL yeah I already have one! I put hoses on one way and use it as a vaccume pump then switch the hoses and use it for compressor to run my air brush!
Srry what i was interested in was  the homade vaccume bags! I figured they would make great storage for my seasonal big game hunting clothes!
Slagnaf6 years ago
I built a vacuum pump out of an old fridge compresser to use as a desoldering station. My question is: Does anyone have any ideas about how to build a trigering device, so the the vacuum does not run all the time?
shortshift (author)  Slagnaf5 years ago
I don't but I'd love to see how you made your vacuum work...
petercd Slagnaf5 years ago
I used a vacuum advance from a car distributor, soldered on a tab that activated a heavy duty microswitch which was connected to the compressor's power. I used springs adding more to get different vacuum levels, wasn't an exact science but it worked. :)
jamesotron5 years ago
Just a quick question - what did you use to tint the resin?
shortshift (author)  jamesotron5 years ago
ah yes, the tint came from the epoxy resin distributor. I've used resins from both West Systems and Tap Plastics and both sources offer tinting for their products...i've been pretty happy with the black you see here. Have no idea how well the other colors stand up to UV light, tho...
Ragged Edge7 years ago
Shortshift thanks for mentioning our kit. We have never really had a problem with offgasing causing loss of vacuum in our Roarockit Thin Air Press system. You may see a small loss of vacuum right after the initial pressing. I check my pressing for the first five minutes. Ten seconds of pumping with the manual pump always beings it back up to full vacuum. The small loss of vacuum is cause from the trapped air being pulled from the skateboard veneers and foam mold. Even when use epoxy in the Thin Air Press there seems to be no problem with holding vacuum. We have actually left sealed bags sit for months while travelling to find them still holding vacuum when we return. Ted from Roarockit
drcrash7 years ago
Here's a YouTube video of a guy demonstrating vacuum bagging of composites.

http://youtube.com/watch?v=s12pUg9ypVU

(He's doing a bunch of carbon fiber motorcycle parts in a big bag, with an electric pump, but its basically the same deal, if anybody wants to see it in action. That video series isn't bad. If you look at the "related" tab you can find the episodes demonstrating the layup, etc.)

I suspect that the bike pump will work for big bags---maybe even Trubuchet03's fairings---if your bag is well-sealed, you have a reservoir, and you suck most of the air out with a vacuum cleaner first. After that, you just need to pump now and then to keep up with the solvents outgassing.

trebuchet037 years ago
Nice :)

An alternative (and less likely to leak) method for going around corners with sealing tape is to place your thumb on the tape on corner (maybe slightly before to allow clearance) and force the tape to make a rounded edge. The stuff is stout enough that it will handle it just fine and maintain its seal abilities :)

Always keep in mind that the worst thing you can do to a vac-bag part is to apply a vacuum, and then release it (you're basically forcing air into places that you just displaced of resin :/)

I didn't go too far into vac bagging details - but here's a larger part made and vac bagged (for inspiration and such :p) :)
Large Part Making
shortshift (author)  trebuchet037 years ago
Hey, that's a good point about contiguous tape! the tape is really quite bendable, so this makes sense. I'll try it out and see how it goes on my next bagging session. Yeah, this was just meant as a low end instructable for smaller projects, I liked reading about your bike fairing project. What kind of speeds are your riders clocking?
Slow :p

~30mph -- but we weigh way too much (~90lbs total vehicle weight) and our fairing has way too much structure to it :p This year's goal is sub 50 pounds - so a 12-15 pound fairing is about where we want to be.

The irony is - that fairing was made on a "low end" budget - for a fairing :p

Oh,

US Composites is another good supplier (we use them and fiberglast) :)
shortshift (author)  trebuchet037 years ago
One Word, and One Word only: monocoque!!!! US Composites is a good reference, I'll include them in the Summary.