Originally Posted by runnin4melife
I am looking at some vacuum pumps right now as I would like to bag the mud guard for better impregnation as well as reduce air bubbles. I was looking at the el cheapo versions (~$80-100) that run 3+ CFM. I am used to heavy duty HVAC style vacs that do 20+ CFM but don't feel like spending $400 or more for something that won't be used professionally.
The issue I have are:
Will I need more CFM to draw down to the appropriate atmosphere I am trying to get?
Sort of.... They do have a corelation, but what you want is a two stage unit. Some single stage pumps claim that they will go to 26 inches of mercury, but in reality , they wont. The ones that will are two stages. They come in different cfm. steps. I have this.....
Longevity, if I am bagging something I will need to run the pump till everything has cured so it will take a while, will this blow a cheap pump up?
You can either use your vacuum chamber, as reserve, or build you a tank set from pvc pipes for about 20-30$.
Curing, can I use IR lamps when bagged in heavy mil plastic or will I wind up with plastic soup, same thing with HTE?
Yes, but you have to step it, as most bags are good to 150-200. Biggest issue is that the IR heat lamp will localize more heat in spots, and they will cook the stuff. So a longer cure for about say 2 hrs, them dismantle, as it has set, and then full post heat cure.
Is it worth it? Even if I do not bag the piece I can still use it to off gas resin before I apply it, but how many bubbles do I create when applying it or pressing layers of CF down...?
Yes it is. I degass most if not all resins before use. I bag almost nothing. I am not hammering on the bagging, but it is a mess, and adds to the cost. I tend to achieve the same with mechanically additions to hold the fabric in place, but none of the pieces I make commercially are in a need for bagging. The reason it is beneficial to degass the resin before use, is specially noticeable with the use of post heat cure resins, as the small bubbles you cannot see while stirring, will blow up and those are the ones you see afterwards in the cured matrix. Yes you whip up a few while working the layup, but they are so big that they pop easily. But it is not all good. Some epoxy's degass better than others. For example, the HTE and 1618 is a pain in the a$$. They have a lot of surface tension, and it is like boiling milk....
So with the hte, I bring it to 90 deg.F. then degass in stages, and same with the 1618. You can also give the cup a squirt of acetone to break the surface tension. Brass has gone through the roof, and I made my own chamber, as seen in my degass video. But I do not think that you can beat the price for any of the ebay vendor's complete kit's. You will get a Chinese pump though. JD Industries.... Yellow Jacket, and some of the few great US made ones. Just make sure it is two stage.