infusion bag leaks

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#1

So I’ve run a couple of infusions so far. Using CF/CSM sandwich and PER from Fiberglast. The CSM serves as my flow media in-between the layers of carbon. On a couple of them, I’ve been about 75% infused when a leak opens up in my bag. This is after I’ve done a ten minute leak test and lost no more than 1" Hg. Both times it has been near one of the tubes penetrating the bag. So I must be doing something poorly where I send the tubing into the bag.

My approach to date:

  1. Lay my tape down all the way around the mold flange.
  2. Then wrap a piece of tape 360-deg around my vac tube.
  3. Peel the backing off all the tape, and stick the tube tape right onto the flange tape.
  4. Then roll the tube back and forth a little bit until the angle b/t the tube tape and flange tape is closer to 90 degrees.
  5. Then put the bagging film on.

Is there a better, more reliable way to get a good seal here? I’d love to see pics of how you do it. So far, only one piece has been ruined by losing vacuum. I was able to salvage the others with some really quick scrambling with some sealing tape. =)

Cheers,

Jeremy

#2

So you’re using Chopped strand mat or Continuous? Chopped will greatly hinder resin flow BTW.

What we do is simply place the tubing on the perimeter tape, and then put a small strip over the top of the tubing. With the backing still on, it’s easy to pinch the tape and roll the tubing a little to get a good seal.

#3

You can always add some more sealant tape. We use small metal tubes, and I end up wrapping (with some tension) few times around. If I can’t afford bag pleats, or large bulky vac. port area, I will wrap once or twice, stick it on the flange, and add one more strip covering the entire tube area, to bulk up so there are no leaks.

—/Ō—

#4

I’m using Continuous Strand Mat as the flow media / sandwich material.

Thanks for the tips. I was able to plug the last hole with some extra tape.

Thinking about it, it seems like there is just more stress on the tape at the tube insertion points on my bag. I guess I need to learn how to do pleats better… Or use stretchier bagging film.

Cheers,

Jeremy

#5

Interesting choice of materials. As long as it works for you, that’s all that matters. I’m just surprised the Continuous strand mat flows enough. Bad sandwich material though, as it’s not really a core since it’s still a reinforcement fully saturated with resin. Have you looked into scored foam?
You shouldn’t really have “holes” if you’re careful with the bagging film. It needs to be stored safely and handled gently.
Tubing insertion points are common areas for air leaks. IMO, the best and simplest way is to use the least amount of tape. Make sure the bag isn’t tight in those insertion areas, or over the mold in general. If it doesn’t have slack before pulling vacuum, one can be assured that it will be pulling all around under vacuum once it conforms to the mold, layup, flow media, and tubing.
I prefer to not use the stretchy film. Tried it at first, and it was good for learning, but the thicker non-stretch films are stronger. The pink stuff works great, just take your time with pleats wherever needed.

#6

Heres what i do, tape around the border then where the resin in tube and vac tube are going i lay another strip about 2 inches wide directly infront of the border tape, lay the tube on the double strip and press it in a bit. Then lay a strip over each of these, press this around the tube with the paper backing on then peel the backing off and with the backing strip and a popsicle stick make sure it is sealed all round (try not to touch the tape too much). I have never had a leak since doing it this way, in fact i have a part under vacuum waiting for more parts to be made ready and it hasn`t lost any vacuum at all and thats after 2 days. Also a good idea to make sure the tube is clean of grease, i give mine a quick wipe with acetone before placing it on the tape.

Baz