Hi,
I have a problem with my vacuum bagged part. It has got a small spots between fibers (micro air bubles?). Can you tell me whats the reason of this? Bad hand layup? Not enough reasin or vacuum?
Thanks,
Mike
If you tell us how you layed it up it would help.
Like peel ply or release film? Breather and how much? Did it get fully saturated? What does the back side of the part look like? Did you lose vacuum? (<----that creates LOTS of small bubbles).
Looks like you didnt have enough vacuum, had a small leak, or you trapped a lot of air during the layup and it got dispersed into many smaller pockets of air.
…also what resin matrix did you use? Cure or work time?
Looks to me like you had some air trapped and it made it’s way all over the part. Are you infusing? If not, you should give it a try. Should solve that if that is your only issue.
OK, so its a hand layup of 2 layers of 160g/m2 twill. I used peelply (83g/m2) with one layer of breather (120g/m2). Almost whole surface of breather was saturated with excess reasin. I had a few leaks at the begining but I make them. Than I had prermanent small microleak, and I didnt find the place. So my pump was running almost all the time. Maybe really this was the problem…
Here is the full size picture of the back:
http://www.carbonmike.webzdarma.cz/DSC00798.JPG
Im using MGS L285 reasin and 285 harderer. It is high quality german epoxi system for small airplanes, gliders and models.
Geltime at 20-25°C (70-80°F) is about 2-3 hours.
By the way this is my first vacuum bagged part ever. 
More pictures:
I will probbably use vac. infusion next time.
Thanks for help
I’d get rid of the breather too if you’re going to try infusion.
it almost looks like dry spots rather then air
Your micro leak was your problem in addition to letting the breather to become fully saturated. With saturated breather and a leak you might have been getting all of 3" of mercury (except for those areas surrounding the vac nozzle). I would also ditch the peel ply for release film.
With release film, once you roll the air out of the glass its pretty hard for it to get back in (which helps if you have a small leak). With peel ply, theres zero tolerance for leaks.
Something that will help you in the future is to go to a hardware store and buy a soft rubber lamentant roller (those used in formica work).
Once the part is under vacuum you can roll the roller on the exterior of the bag and get rid of excess resin and air.
Ok, thanks for your help. I will work on it and use release film or maybe go straight for infusion.
Mike