Double-Bag Infusion

General Composites Discussions Composites Talk
#21

Hi DD, yes everything was debated in that other thread, and is clear now, but still amazed at how the double bag thing has made the wastage of several tons of electronic ink, even by many experienced infusers who defended with apparent good arguments one point just to discover several months later that they where (I was) fooled by the “double bag beast”.

Maybe you can explain the best way to achieve the desired reduction of the speed of the resin infusion front, without restraining the resin inlet, for a large project, connecting the resin “pot”, large bucket in the case of a large project, that needs to be replenished often to a low vacuum does not seem to be practical, waht can be done then ? any recommendations in regards to difussion meshes for this purpose? , maybe enka …

#22

On a boat project there is no need for reducing resin speed. There is enough surface where the resin can distribute so that it will slow down it self.
You have a amount of resin that can enter the mould, restricted by the physics. This amount of resin can distribute in the flow media. And you have an amount of resin that can saturate the laminate in z direction. Normally you will not have a too flat saturation angle because than more it flows on the mesh than more surface to saturate in z. Tham means that even that is self regulation. Of course not if you make a teacup amd use a 20mm diameter hose, but if you take care of the diameters and part size it is not critical.

#23

Like always a pleasure to hear your expert opinion …

So we will use a double bag only if we do not attain an almost perfect vac integrity, if that where the case (db), we will fit the second bag outside of the perimeter of the first bag, without any breeder, so it does seals the other plastic effectively, with a vacuum outlet spiral hose (with peelply wrapped around) under the first film bag and another vacuum outlet to serve the vac to the second plastic, then we empty the first bag to maximum vac and after it settled apply vacuum to the outer vac line I suppose ???

More doubts, we plan on using Infutac as the spray adhesive to keep our reinforcements in place, any good or any bad this brand and type of adhesive???

Or is the same as the ones sold by airtech ??

An another one, do you have any trick to be able to glue the green flow 75 properly to the peelply layer ??

Maybe with a bit of hot glue gun can do the trick ??

Thanks a lot for your help, I am already in contact with Daniel D. in regards to the purchase of some more 30 DD clamps

#24

3:58 single or double?

http://youtu.be/KvyAbM67yKI

#25

Hi Dallas, it certainly seems the russians (whom I highly respect as technicians) have used a double seam in their infusion, if that means a double bag or not, it is very difficult if not impossible to distinguish in the video.

Certainly the db or sb thing is extremely controversial because it very much seems that it works, but despite its ability to look diferent than reality, several tests have been conducted, even by Diab who inserted a scale inside the first bag and concluded that the second bag did nothing that could be noticed, also others have gone even farther, even making test samples of pieces just to find there was no improvement in the double bagged ones, so despite of its apparent goodness the db gives nothing more than a better seal.

The “thing” is really umbelievable, because it is obvious that the Boeing engineers in charge of their composites Dept. must knom a thing or two about vacuum and composites, and they went as far as to patent it, make a patent for something that is against the laws of physics and that is almost useless, really an amazing situation ( or better said embarrasing for Boeing), and so many experts in the field fooled in their beliefs really something that does not happen every day, but we have to accept the crude reality.

#26

In my opinion the thing is clarified enough already and being of such anature that i think this thread should be a sticky thread of this forum to help other infuser colleagues avoid being self fooled by the very own nature of the process …

#27

Well the video is very very vague. And fuzzy in certain areas which leads me to think it was a mock for filming. It certainly looks like a db.

#28

they might be using db just to improve integrity …

#29

Yep that’s what they said in the video while the guy was leak checking.

#30

“just” for vacuum integrity. Vacuum integrity is the most important thing at a infusion. If you vacuum is not stable you will never get perfect results.