soholingo

I am going to get one of these pumps. The Autovac is perfect but it costs twice as much as the EZ vac. I plan on glassing wings, and bagging items in the mold. I also plan on doing different types of foam, pink and blue note. Why do I need more pressure to glass these wings...

Jay

davidfee

Jay,
It's funny... I've heard several times that "you need more pressure with the denser foams." This just doesn't make any sense to me, and I've done a lot of vacuum bagging over the years. You want as much pressure as you can get without crushing the material or forcing all of the epoxy out. It's just like clamping two pieces of wood together with glue in between.

The point is not that you want more pressure (better vacuum) with the blue/pink foams but, rather, that those foams have much better compressive strength and will allow you to pull more vacuum before they crush.

For white foam I use 6-10" Hg and for blue foam I use about 15-18". If it's a rigid mold, I'll pull as much vacuum as I can get, which is usually about 23" Hg. Full vacuum is about 30", but there will always be small leaks and you'll never get there. Trust me, I work in an ultra high vacuum research lab. I spend much of my time plugging leaks.

If you want to bag things in molds you will want the strongest pump you can get because the weaker ones just won't give you the pull you need to bag complex shapes. Plus, the more pull you have, the more excess resin you can squeeze out of a layup (one of the benefits of vacuum bagging).

-David

soholingo

David,

Again you have come to the rescue, I will save up and get the auto vac....

Thanks much.

Jay