Where do I find info on vac pressure. My pump pulls 28" max. Where should I be? Carbon fiber,epoxy resin. Not structural but would like to know if it makes a difference structural or not. Thanks in advance
For infusion: 29" or better.
For wet bagging: anywhere between 14 and 28. Depends on your setup and requirements.
Hi Herman, i’m still a bit confused with “For infusion: 29” or better." does it mean where ever you are in the world your pump need to be able to pull this coz my pump goes as far as 27
thanks.
Do you mean hand lay up and bagging. I tried this but have bubbles problems in some corners. My pump only pull to 15-16 inHg :sad2:
I need a better vacuum pump.
Wet lay up and bag on these parts. What do you mean by set up and requirements? Can a person pull too much resin out with high vac?
What you want to achieve is near to no air in the dry stack, during infusion. Any void that might develop initially has the same pressure, and thus air, as the pressure in the dry laminate.
This means that if the pressure is 14 Hg, there is quite some air in it. This void will only collapse to half its size, if the resin goes to athmospheric.
If the void is near perfect vacuum, the void will collapse almost completely. This is how you get a near void free laminate.
For wet bagging things are totally different. You start at atmospheric instead of “perfect vacuum” so once you are pulling a vacuum, you are only enlarging the voids that are in your hand laminate. You will also compact the laminate, so some resin needs to disappear (into the bleeder) and this will take some of the air with it, but air deep in the laminate is hard if not impossible to remove. (laminating the first layer resin rich does help, it makes more moving resin).
Factors that determine (part of) succes are:
-viscosity and flow of the resin when a vacuum is pulled. Apply vacuum later, and the resin is more viscous. (whether this is a good thing depends on other factors.)
-type of perforated film. Film with larger or more holes has more bleed out.
-type of bleeder. A thin bleeder will saturate, stopping the bleed.
-playing with vacuum. Some report better results by first pulling a high vacuum, then bringing the vacuum back. This might work because of the principle I noted in the infusion section above.
Keep in mind:
Vacuum does not move fabric. Fabric is hard to get into corners. Round off corners before laminating (can be with a mixture of resin and filler, and a popsicle stick, or a spoon)