Vacuum Bagging

[Ray Barnes]

I was looking at the West Sytems venturi type of vac. bagging kit. Does this system work well? Does the compressor run the whole time to generat the vacuum? Is their any other route to take to vacuum bagging that isn't real exspensive. I have never tried doing it and would hate invest allot of money and find it's something I don't want to get into. I would just use it to make small parts like wings and cowls and flat stock.

 

[Joe_Knesek]

Ray I just happened to be building this type of system and no the compressor does not run the whole time. You have a couple of options but either way you need a check valve between the bag and the venturi.

The simplest method is to make sure your bag doesn't leak and just seal off the system once you have pulled the required vacuum.

The better approach which is what I am doing is to use a 3 way valve between the compressor & the venturi which is coupled to a sensor that monitors the vacuum. When the sensor detects the change in vacuum it will open the valve activating the venturi and maintaining a constant vacuum without the need for the compressor to run the whole time.

 

[Ray Barnes]

Are you using the West System type? Where are you getting the sensor? Thanks for the help.

 

[Joe_Knesek]

Ray I built my own system because I use many of the same parts in the digital flow meters I make. You can get everything you need from this site: http://www.joewoodworker.com/veneering/v2-about.htm .

 

[Preston_Hall]

You can get a pump from any old refrigerator and it will work just fine. Once a vacuum is drawn the pump does not need to run. Well, unless you have no leaks which will always be the case.

The only thing you need to spend money on is the bagging and release materials.

 

[noodles]

Where is a good place to get a bag and what do you use for release materal?

 

[Joe_Knesek]

http://www.acp-composites.com/acp-vbes.htm

 

[Jim Caldwell]

Once you have the vacuum system together and start to build, here is the best source of supplies I've found.

I'm sure others here will have other supplier's too.

http://www.shopmaninc.com/index.html

 

[Joe_Knesek]

Does anyone have a source for Prepreg?

 

[Jim Caldwell]

No, but you might try Tatan Marine (the sailboat builders) in Painsville for sources or material.

 

[tnrcboatracer]

For prepregs your best bet is the aerospace market: Hexcell, Hercules Aerospace, and many others. The problem will be the small quantities, low temp freezer storage, and the fact that most prepregs require an autoclave to cure the resin (typically 350F, 100PSI, vacuum on part).

Signed,

An ex-Aerospace Composites Engineer. :huh: :huh:

 

[Brian Blazer]

Where is a good place to get a bag and what do you use for release materal?

I use heavy duty garbage bags.

 

[Joe_Knesek]

Where is a good place to get a bag and what do you use for release materal?

I use heavy duty garbage bags.

I assuming I can also use food storage vacuum bags for small parts?

 

[Joe_Knesek]

For prepregs your best bet is the aerospace market: Hexcell, Hercules Aerospace, and many others. The problem will be the small quantities, low temp freezer storage, and the fact that most prepregs require an autoclave to cure the resin (typically 350F, 100PSI, vacuum on part).
Signed,

An ex-Aerospace Composites Engineer. :huh: :huh:

I'm interested in the type discribed below which I grabbed from Netcomposites.com

"Description

Low Temperature Curing prepregs are made exactly as conventional prepregs but have resin chemistries that allow cure to be achieved at temperatures from 60-100°C. At 60°C, the working life of the material may be limited to as little as a week, but above this working times can be as long as several months. The flow profiles of the resin systems allow for the use of vacuum bag pressures alone, avoiding the need for autoclaves. "

 

[tnrcboatracer]

I've never heard of these prepregs, but I have been out of the composites industry for many years. They sound interesting, but there isn't a source listed. I sounds like the resin will go through a significant viscosity decrease with just a little heat. You will still need to store them in a freezer, and the shelf life will be very limited.

 

[Joe_Knesek]

I've never heard of these prepregs, but I have been out of the composites industry for many years. They sound interesting, but there isn't a source listed. I sounds like the resin will go through a significant viscosity decrease with just a little heat. You will still need to store them in a freezer, and the shelf life will be very limited.

Thanks for the info Jon

 

[Mike Broad]

I would have thought that because rubbish (garbage) bags are opaque it would make the job more difficult. A good material to use for bagging is PVC damp course membrane sheet available from a builders merchant, not too thick. The open seams can be stuck together with commercial silicon sealant and allowed to cure. The final seam can then be joined with glazing tape, it comes on a roll and feels a bit like "Blue Tack" . The best material I used was not surprisingly purchased from a West Systems supplier. As I recall it was not very expensive. The bags can be used several times if you are careful.

Mike Broad