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My vacuum bag layup has crinkles, any advice?

Old 12-07-2007, 01:22 PM
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seanreit
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Default My vacuum bag layup has crinkles, any advice?

I used painters drop cloth that had the woodpecker tool run all over it. Then on top of that paper towel for breather cloth. Then bagged the whole thing and pulled -10 for 8 hours.
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Old 12-07-2007, 02:30 PM
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dreadnaut
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Default RE: My vacuum bag layup has crinkles, any advice?

I suspect that the mylar release did not breathe properly. The woodpecker pokes holes rather than punching holes, That is the flared edges of the ''poked'' hole were drawn back and closed up.

Just a thought. It looks like the resin drew through in some spots, but not in others. Either buy that pink stuff from CST, or lay the mylat on something soft and run the woodpecker a llittle harder
Old 12-07-2007, 04:00 PM
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davidfee
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Default RE: My vacuum bag layup has crinkles, any advice?

Any wrinkles in your drop cloth (or any release film... perforated or not) will result in these resin ridges. The resin fills the wrinkles and stays there. These resin ridges are kind of the nature of the beast.

What you can do is... 1) eliminate wrinkles in the release film as best you can... 2) use less epoxy... 3) use more vacuum. You can substitute peel ply for the release film, and applying the peel ply in strips can help avoid wrinkles.

Good luck.
Old 12-07-2007, 04:29 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

True, but. . . I have not had trouble with this using the perforated release film from CST. I guess it is because it is easier to get it layed flat if sufficient excess resin is being drawn out. And like you said, too much resin can cause issues, like puddling and wrinkling. I usualy start with just an inch or two of vacuum to hold stuff in place while smoothing out the stuff in the bag.

Earlier on, I had tried unperforated painters dropcloth. Lets just say it was very educational.
Old 12-07-2007, 05:08 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

Question, should I put resin in the mold, then layer of glass, then resin, then layer of glass, and no more resin, and let the vacuum pull resin from underneath the last layer through? Or does it matter?
Old 12-07-2007, 05:09 PM
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davidfee
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Default RE: My vacuum bag layup has crinkles, any advice?

Yeah, I wasn't meaning to contradict you. I use the pink perforated stuff from CST myself... but my point was that if the release film goes in with wrinkles... those wrinkles aren't going to disappear when you apply vacuum.
Old 12-07-2007, 05:17 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

I have had similar results - wrinkles and ridges with plastic release. Like David said comes with the teritoy.

I recently tried home made plastic breather (wanted more flexible/stretchy plastic) made in a similar fashion to your description - this caused me problems with pockets of air being trapped and incomplete bleed of the epoxy.

I used peel ply instead and had a great result. Still had to be real careful in the initial draw down to look for wrinkles and bridging.

http://www.rcgroups.com/forums/showt...68#post8538068


BTW - over in the composite section of rcgroups IIRC there is a long thread discussing wrinkles in vac bagging.
http://www.rcgroups.com/forums/showt...light=wrinkles



Like what you are doing

cheers Jeff
Old 12-07-2007, 05:18 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

I think you'll be disappointed if you don't ensure that each ply is fully wet-out before you put it in the bag, as you're likely to get dry areas and puddled areas. How you get each ply wet out is a matter of preference. An ideal would be to have room temp prepreg (yes, it does exist).

What I typically do is brush in a coat of epoxy (often thickened a bit with colloidal silica to make it sticky)... then add plies one at a time. I brush in a thin coat of plain resin between each ply. Small reinforcements are often individually "prepregged" on butcher paper before being added to the layup.

Once the layup is finished, I blot up excess resin using paper towels or toilet paper. Then I add peel ply or release film... making sure to remove any wrinkles. Then the breather and bag as usual. As dreadnaut said, start with low vacuum so you can adjust things and remove wrinkles.
Old 12-07-2007, 05:19 PM
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Default RE: My vacuum bag layup has crinkles, any advice?


ORIGINAL: seanreit

Question, should I put resin in the mold, then layer of glass, then resin, then layer of glass, and no more resin, and let the vacuum pull resin from underneath the last layer through? Or does it matter?
Lay it up then soak up excess. I like to take a paper towel cut into 2'' wide strips, and rolled like a cigarette. I use this to roll the fabric down, and to soak up excess resin. It is inevitable that there will be some wrinkling of the release film but is it is kept to a minimum you should be OK.
Old 12-07-2007, 05:28 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

One other trick.

Massaging the layup- I squeegee the plastic vag bag film during and after the vacuum is pulled. In the larger areas I use a plastic squeegee (apply talc to the plastic to make it slippery) and in the small tight areas I use my fingers. What I am trying to do is smothe it all aut.

History:- I attended a composite seminar at Oshkosh and one of the demonstrations was vac bagging a single piece of cloth over a foam pyramid. Using the squeegee (plus talc) the all the wrinkles and puckers in the glass were removed - impressive stuff. In the demonstration of the squeegee method no breather was over the composite itself (breather around the edge of the bag). The process relied on squeegeeing the excess air and resin out to the breather material. Result:- No wrinkles.

cheers Jeff
Old 12-07-2007, 05:37 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

ORIGINAL: dreadnaut

Lay it up then soak up excess. I like to take a paper towel cut into 2'' wide strips, and rolled like a cigarette. I use this to roll the fabric down, and to soak up excess resin. It is inevitable that there will be some wrinkling of the release film but is it is kept to a minimum you should be OK.
I have put hthe layers in like David (most sucessful method) plus another method -wet all the layers up as a group on the bench and put them into the mold as a wet mass (only on small molds). The all layers at once method has troubles with air entrapment!

Yes I like to soakexcess resin before the final vacuum.

With my little molds that fit in a bag with clips (easy to get at) I do an initial quick vacuum with tissue, remove the saturated tissue and then proceed with the normal vac techniques. Then I can use much thinner breather so that I can more easily massage out the wrinkles.

Hint:- I often use a hair dryer to warm the laminate once it is under vacum -it makes the epoxy more runny. The vac bag I use is heat shrinkable and the hair dryers shrinks out the wrinkles in the bag and allows the bridges in the bag to stretch down into the mold. Stuffs up the bag for repeated use[X(] I am using food packaging tube as my vac bags - designed for heat shrink.


cheers Jeff
Old 12-08-2007, 11:15 AM
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Default RE: My vacuum bag layup has crinkles, any advice?

Aside from what has already been listed above...About the only way your gonna get a repeatable smooth IML surface is to make yourself a caul...

Definition taken from About .com:
"Definition: Smooth metal plates, free of surface defects and of the same size and shape as a composite lay-up, used in contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished laminate."


http://www.fiberset.com/html/glossary/glos_c.htm
http://books.google.com/books?id=VkX...y7So#PPA206,M1
http://books.google.com/books?id=5t5...2dmec_XH-_hU7Q

Most of these links refer to cauls as being a metal plate which is not necessary...You could just do a 2 or 3 ply e-glass laminate (semi rigid) to the IML surface and use that as your caul...

A couple of ways to get there...One would be to wax up your mold with the appropriate "part thickness" tooling wax to get the IML dimensions....Or...Maybe an easier way: Just clean up the back side of the part you have pictured...Set it back in the mold and just do a wet lay-up to that IML surface...Remember it will be just like your OML as far as surface finish...So clean it up to suite your IML requirements...

If you use your existing laminate...I'd pay a little extra attention to the corner radii...If you had any bridging or resin rich corners in the initial part...Sand them to the correct part thickness prior to making the caul...Then your corners will come out nice and tight...If you don't fix them and the caul has loose tolerance corners...You'll have crappy corners in your parts...Hopefully that makes some sense...

I'm working on a project...It will be a few weeks before I get to making cauls...I wish was further along so I could show you some photos...Darn..

Have Fun...

Chuck

P.S. Nice looking work there!! As everyone else mentioned...Wrinkles are kinda part of the game...
Old 12-08-2007, 11:54 AM
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Default RE: My vacuum bag layup has crinkles, any advice?

One Question after re-reading...Are you regulating your vacuum?? If so..Why not shoot for 100% debulk?? Just curious...

I understand regulating vacuum while skinning foam cores ect...

But making a part in a mold I always try for a full 14.7 psi (or what ever barometric pressure will yield on a given day)...

Maybe I'm missing something?? Maybe I'm reading your gauge wrong?? (I'm reading it as 10inHg)...or maybe that what your system is capable of??

I'm not trying to be an arse...Just wondering...

Have Fun...

Chuck
Old 12-08-2007, 01:02 PM
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seanreit
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Default RE: My vacuum bag layup has crinkles, any advice?

I bought a pressure regulating switch and can't figure out how to get it to go lower than pulling 10. My system is capable of going to 30 without the pressure switch, but then it just runs continuous. I have 25 gallons of capacity on the vacuum system. Which pulls the bags down pretty quick. I have not found any good way of regulating the vaccuum to any other pressure than full on (30) and pressure switched (10).

Any suggestions would be appreciated and I am taking very good notes from this thread, so thanks guys!
Old 12-08-2007, 01:03 PM
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Default RE: My vacuum bag layup has crinkles, any advice?


ORIGINAL: navav2002

Aside from what has already been listed above...About the only way your gonna get a repeatable smooth IML surface is to make yourself a caul...

Definition taken from About .com:
"Definition: Smooth metal plates, free of surface defects and of the same size and shape as a composite lay-up, used in contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished laminate."
Wow! I thought I was crazy. I had thought of doing something like this. Good to know I am not the only ''nut'' out there.

It even has a name. Thanks.
Old 12-08-2007, 01:06 PM
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Default RE: My vacuum bag layup has crinkles, any advice?


ORIGINAL: seanreit

I bought a pressure regulating switch and can't figure out how to get it to go lower than pulling 10. My system is capable of going to 30 without the pressure switch, but then it just runs continuous. I have 25 gallons of capacity on the vacuum system. Which pulls the bags down pretty quick. I have not found any good way of regulating the vaccuum to any other pressure than full on (30) and pressure switched (10).

Any suggestions would be appreciated and I am taking very good notes from this thread, so thanks guys!
Try putting a ''T'' fitting in the vacuume line and conect the branch to a small ball valve to get a pressure bleed.
Old 12-08-2007, 01:14 PM
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seanreit
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Default RE: My vacuum bag layup has crinkles, any advice?

I'm such an idiot, duh, I already have that, I had shut it off to keep pressure, so I misspoke, and didn't use my brain, sorry.
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Old 12-08-2007, 01:31 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

ORIGINAL: dreadnaut


ORIGINAL: navav2002

Aside from what has already been listed above...About the only way your gonna get a repeatable smooth IML surface is to make yourself a caul...

Definition taken from About .com:
"Definition: Smooth metal plates, free of surface defects and of the same size and shape as a composite lay-up, used in contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished laminate."
Wow! I thought I was crazy. I had thought of doing something like this. Good to know I am not the only ''nut'' out there.

It even has a name. Thanks.
Actually cauls are not uncommon in the Aerospace Industry...Parts which require a controlled IML surfaces..for instance a build up structure with Ribs ect. will basically have to use both IML and OML tooling...The tooling will vary depending on the nature of the part of course...

For us and our home projects...I think we can use those principals and "Find Ways" to adapt them for our applications too...


Vacuum:
Yeah...My pump runs continuously too...Which is what I want...I want to continuously be removing the volital's which are generated as a byproduct of the epoxy resin curing...

Is there a reason you don't like your pump running continuously?? Not sure what equipment your using...But that should be what it's designed to do...

I know you all have heard this before..he he.....But...In an Autoclave...You still leave the vacuum source hooked to the bag...The Autoclave will be responsible for applying pressure to the laminate...The purpose of vacuum will be to remove the volitals...Very important...

Have Fun...

Chuck

Edit...I see the pic of your pump now...Wow...Nice Set-Up!! It should be designed for continuous operation...
Old 12-08-2007, 04:01 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

This is what I built for vacuum, it is my third one and the best. I hate to have the pump running continuously with noise while I work in shop. This runs for 10 seconds about every 15 minutes if you have no holes in you bag. This is the web site for plans ttp://www.veneersupplies.com/vacuum_press.php When you pull vacuum over 8 you need a Mac Valve so the pump will restart. I used a vacuum controller from Airtol, if you look in upper right of picture for a slot you can adjust vacuum. I pull to 26, it stops and when it drops to 22 it starts again.
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Old 12-08-2007, 04:07 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

there's my problem, I ordered an x30 and got an x10!
Old 12-08-2007, 07:32 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

Wow...What a nice set-up you have there!! Very impressive!!

So your intent is to shoot for 100% debulk...You just had the wrong regulator...Correct?? Well then that is good

Have Fun...

Chuck
Old 12-08-2007, 08:13 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

YUP
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Old 12-10-2007, 12:29 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

On the vacuum switch. I use this one here ([link=http://www.veneersupplies.com/product_info.php?cPath=60_36&products_id=58]Adjustable Switch[/link] and it has completely adjustable switching points with a couple of little screws.

As far as the bag goes, I too get wrinkles and have a pretty complex compound curve in my hull halves. I'm hoping that the Stretchelon bagging film, coupled with careful application of the bleeder ply will help minimize this problem.

On the other hand, I have heard about reusable silicon sheets that you can use for your mold - you vacuum the silicon sheet to your mold and heat set it (or set it somehow). The silicon takes the form of your mold and makes it super easy to seal each lamination.

For my next attempt, I intend to try to laminate the glass / kevlar flat on the workbench on top of a bleeder ply and then work that into the mold carefully rolling it with a small dry paint roller. The bleeder ply will hopefully be flat bonded to the glass - though I know air entrapment will potentially be an issue.
Old 12-10-2007, 12:49 PM
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Default RE: My vacuum bag layup has crinkles, any advice?

How do I know if I have a "Rotary vane" vacuum pump?
Old 12-10-2007, 01:22 PM
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Default RE: My vacuum bag layup has crinkles, any advice?


ORIGINAL: seanreit

How do I know if I have a "Rotary vane" vacuum pump?
Based on the picture, yours could be. The clue is the attacment of the line goes tangent to the round part of the head. This is characteristic of vane pumps and centrifugal pumps. Mine is a diapragm, and the line come right out the middle.

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