Vacuum Bagging Anyone?

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JDcluster

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I know there are a few people who do it.
I have dabbled with it in the past and want to dive in deeper.
Need some tips and more info on proper setup?

I have the needed materials; Bagging film, Peep-Ply; the bleeder / breather is on order...
I have a vacuum pump that I use for degassing propellant so that's not an issue.

My last true attempt was done using the Food Saver method aka: Poor Mans vacuum bagging.
Found on John Coker's awesome website: https://www.jcrocket.com/kitchenbagging.shtml

My biggest problem(s) being: wrinkles in the final product.
I've ordered some 3M spray adhesive to prevent it.
I've done fiberglass, Carbon fiber and Carbon / Kevlar hybrid cloth.

On my next project I'll be doing Carbon and FG on a 4" fincan.

I'd like to vacuum bag it for better results.


JD
 
One thing I do to eliminate wrinkles is to have a bleed on the vacuum to control it. Basically, I remove almost all of the air in the bag, but it is only under a very weak vacuum (and stays there). Then I can take as long as I need to smooth out and/or adjust the bag and layers easily yet still hold everything in place, so that keeps the bag from inducing wrinkles. Then I slowly increase the vacuum by reducing the bleed. Doing it that way I can keep up and keep everything smooth. When I'm happy with it, then I just cut off the bleed. A needle valve for a bleed works best, but you can do it with a ball valve and a delicate touch. I've had very good luck keeping out the wrinkles even on more complex curves such as a fincan.

David
 
The 3M tack spray will help with the stack moving and rucking/puckering but too much is a no no! It can and probably will prevent full saturation and even cure of resin. Use very sparingly.
 
I've heard of this trick a long time ago.
I was hesitant about trying it myself but, if it helps.
It's been about 15 years or so since I really got into laminating tubes.
Need to dig up all the old techniques.


JD

The 3M tack spray will help with the stack moving and rucking/puckering but too much is a no no! It can and probably will prevent full saturation and even cure of resin. Use very sparingly.
 
For the wings I make, nothing beats getting a smooth surface like a nice piece of waxed 14 mil mylar that goes over the part, under the peel-ply.

Here are a couple of wing cores in the mylars, going in the bag, and the result.

kj

IMG_4557.JPG

IMG_4558.JPG

IMG_4583.JPG
 
I did a write-up on how I bagged a fincan, and here's a link.

https://www.raketenmodellbau.org/repository/archive/167793?view=true

My approach is likely more involved than what you want to do, but perhaps there is something I did that will help you (I didn't get any wrinkles for example). One thing that helped me was to use the stretchy bag material. And, you should avoid the 3M adhesive - it will prevent the epoxy from wetting out the cloth.

Jim
 
JD:

I've been vacuum bagging my large fins. 4 feet by 30 inches. 2 layers of CF on each side, done all at the same time.
My EX vacuum pump did NOT work. Those oil driven pumps start to smoke badly. Fortunately, I was at the firehouse and they had a Gast oilless vacuum pump.That worked brilliantly!
As far as wrinkles, avoid the super 77. just get a printer's roller and roll the snot out of the stuff, get the peel ply rolled on then stick on the breather. Flip and repeat, then vacuum the crap out of it - I went 2.5 hours.
Make sure your table is flat otherwise you'll put a warp in your final product. I was able to straighten 1/2 inch 9 ply baltic birch....
Maybe bring one for the board meeting saturday, depending on how i get down. Pick up the DOA then?

rick
 
I had my first go-round with real vacuum bagging.
It is more work than simple fiber glass lamination.
Picked up a used pump from E-bay for less than $300 but, a little more than I want to spend.
It's smaller than my propellant pump.

I had to run to the hardware store for more fittings to adapt the NPT over to flare.
here's a pic of the setup under vacuum.
2015-02-06 12.28.22.jpg

2015-02-06 12.28.29.jpg

It pulls about 22 in Hg.
Not as good I would have wanted but, it's a start.
At first, I had a few issues getting a good seal on the bag.
Once I resolved most of them; the vacuum went from 15 to 20 almost instantly.
Started with 3 fins as a test project.... I have 3 more to do after this.

JD
 
Last edited:
The fruits of my labor:
I used 1 layer of 6 oz S-Glass and 1 layer of 3 oz E-Glass
on all of them.

Initial trim up.

2015-02-06 20.25.25.jpg
2015-02-06 20.26.00.jpg

I vacuumed them for about 3 hrs
Turned off the pump then let them sit for another 2 hrs before I removed the bagging materials.
They were slightly tacky to the touch when I removed them.
I used West systems Epoxy with 206 slow hardener for this.

If I was doing CF I would have used AeroPoxy. It is thinner and takes even longer to cure.

Smooth on both sides.

JD
 
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Funny. I did the reverse for my setup. Adpated the compressor tank fitting from flare to 1/4 " NPT. Used standard air compressor hose which is NPT, and use NPT quick disconnects on both ends of the hose.

Looking good.
 
The HVAC pump I have for propellant uses flare fittings with a vacuum hose which is also Flare.
The vacuum hose has rubber seals on both ends no need for any Teflon tape there.
The GAST pump I bought specifically for this uses NPT.
I also wanted a inline ball-valve to limit the vacuum.

JD


Funny. I did the reverse for my setup. Adapted the compressor tank fitting from flare to 1/4 " NPT. Used standard air compressor hose which is NPT, and use NPT quick disconnects on both ends of the hose.

Looking good.
 
My second day, second project:

Three 1/4" birch plywood fins for my new 4" Rocket R&D Sky Raider.
6 oz S-Glass with a top layer of style 120 3 oz E-glass ( same as yesterday)
2015-02-07 13.40.56.jpg


The only real difference on this is: I taped the root edge to keep the epoxy off for better bonding to the motor tube.
I got a better seal with this bag it's pulling almost 25" Hg.

2015-02-07 13.40.42.jpg


JD
 
Check out Fibre Glast. The link goes to their bagging materials. The Stretchlon 200 may help with wrinkles. You can completely eliminate wrinkles by using a caul plate, this is a bit more of a challenge on a tube but it is very simple for flat fins and produces beautiful results.

An additional note, the yellow sealant tape makes eliminating leaks much easier but be sure to put flash tape down first if you are working on anything other than a hard gloss surface or it is a bear to pull off.
 
I just ordered some more sealant tape.
Never used the flash tape I'll have to get some.

My next challenge is to VB the fins on a long booster.

Thanks!

JD
 
I installed a few ball valves in my system which allows me to vac-bag two projects at once. But it also allows for me to finely control the amount of vaccum so that I can eliminate any wrinkles prior to finally letting 'er rip.
 
The flat surfaces are easy, compared to trying to do tip-to-tip on the fins that are already installed on the rocket.
The first time had to be aborted due to the bag being undersized...


JD
 
If you are sealing the bag to something like unpainted plywood, the sticky tape is a pain to remove cleanly. Flash tape also makes clean up generally easier no matter what your work surface is.
 
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