Pedro - 

guys this  problem was nightmare  to my friends parts also so errors caused him by these  2 spots : 1. VACUUMING BAD LEAKED! SECOND AND MAIN 2. MOLD YOU THINK YOU MADE GOOD BUT FROM PHOTO I SEE SAME ERROR ITS TINY HOLES IN YOUR MOLD THAT DO LEAKS FROM YOU AND PART NOT HAVE FULL VACUUMING AND YOU CAN NOT FIND ERROR. MY ADVISE DO NEW MOLD AS I THINK HERE YOU GETTING ERRORS.

Hi everyone!
I have exactly the same problem I tried the trick with getting a layer of tacky resin. It helfed alot with the Pinholes but i still get some voids. If i can fix that too with the tips above i´ll post a few pictures with results. It would be great to hear of your problems have been solved pedro!

Finn

Hello Pedro
If you didn't have voids or pin holes the part would be perfect. If you used polyester the sun will turn it ugly yellow in a year like the the cheap polyester chinese car hoods coming into this  country. You really should be using epoxy and then uv resistant clear coat.
It looks like you taped down the carbon fiber all the way around the perimeter of your mold. (I could be wrong but lets assume that is what you did)
So look at one of your voids. Follow one of the fibers from perimeter through your void and to the other perimeter. Because you have taped it down the only way for the vacuum bag pressure to push the carbon strand down is to stretch the carbon strand which is now locked tight from either side of the mold by the tape and bag pressure of 14 PSI. It ain't going to happen! Carbon in tenion is the strongest material known to man. Ask me how I know? I used to tape my perimeters and got the same voids you did.
So what I do now is put a few pieces of making tape to just hold things and delibrately push in a little slack into the carbon. I draw just enough vacuum to start to squeeze the stack and then close off  the vacuum and push the carbon through the bag into the tight spots that I know I will have problems with and then increase vacuum again, stop at half vac and do the same and then finally full vac and message some more.
It has made all the difference to my layups.
Hope this helps.
Fred   

I think we've all been through this one!  I only do hand lay projects, I just find it easier.  The first one os often caused by the bag moving the fabric once you've pressed it into the mold.  It especially occurs on flanges etc.  Try trimming your cloth shorter if you can.  The pin holes is another pain.  I find carbon wets out very easily (almost too easily) which makes it seem that you dont need to work it too much.  I foound that this gives pin holes but a stable laminate.  If you make sure you go over the whole area pressing the resin in with the brush (even if it appears properly wetted out) it will help get rid of these. 

Using polyester with vacuum may make both these problems worse.  You could pull out the styrene which is quite volatile causing bubbles and a poor resin matrix.  I can really recomend the EL2 resin.  Its a nice, low viscosity, easy to handle resin.  I dont use any other on carbon now.

Hi Pedro,

Try once again but laying up the resin (1mm thickness) first until tacky almost dry, then laying up the CF. I think that will ensure to get the solid surface when de-mould and  no pin holes.. don't give up  I'am on "HIGH STRESS LEVEL" in composites project to.

Regard

Leon  

Hello, Leon

The truth is that i´ve used PVA, not easy lease, and the resin is poliester(much cheaper, but i think that is not the problem).

I´ve applied a first layer of resin, but didn´t wait until it be te tacky.

Thank for the help.

Regards,

Pedro

Hi Pedro,

I've involve in this process vac bag lay-up for more than 10 times trial and error, the problem just like what you did. Then I move on resin infusion method, My suggestion for vac bag lay-up process is, firts do not using PVA, use chemical release agent "easy lease" you can buy at easy composites. Second, you have to applied epoxy resin  "tacky-surface" or polyester compatible gel coat "dry-surface" before you laying up the CF and aplying resin. Third, is turn down the vacum pressure and make sure that there is no leak on the vac bag

Regards

Leon

Hello,

I´m trying to make a fender for two times, but i have always the same problem.

The process was:

- 2 layers of wax

- 3 layers of PVA

- hand layup

- perfurated film, breather and vac bag

When i pull the vac i payed attention and made wrinkles with the bag in the corners, but it seems not working.

The result of the firt attempt:









The result of the second attempt:









The mould was like this:







If anyone know what am i doing wrong, please tell me.

Thanks,

Pedro