Hi Guys

This is my first post. (I can see that this forum will be very useful to me)

I have watched your videos many many times. I am not new to infusion, but pin holes or voids are my problem.

I understand that the problem is resin starvation caused by too much being removed by leaving the vacuum pump running over night. I am very careful to get a good seal and I use only the best bagging film and tacky tape. But cannot get a perfectly sealed bag! . My catch pot will hold a vacuum indefinately as well as my degasser. But the bag always loses its vacuum.

What is the most common cause to look for?  

Thanks

Fred

With regards to getting a full seal

an additional remark/hint:

Thanks Dave

You said that even one filament of carbon fiber could cause a slow leak. That is probably it I would guess. It is pretty hard to avoid this problem. Any tricks of the trade here. Is a head set (expensive) leak detector a must? Would that pick up that small of a leak?

Thanks

Fred

Not sure, but Im guessing those expensive ultrasonic detectors would pick it up, its what theyre made for. 

Thanks

Anyone had any experience with those electronic leak checkers?

How good are they?

I have been putting the gum tape down with the bag, I thought I was careful to keep it clean, I will try it the way described.

Fred  

Hey Guys, I been gone a while But still been making parts. O MY have a learned alot since I have been here but still love it. I still plan on reading up on how to make a hood soon and trying it.

I will tell you MORE THAN ANYTHING I could not get a good seal because of a mold... When your putting that part on the table to be clayed in #1 gotta be mega mega mega clean, little dust gets in the gel coat and make mini swiss cheese.... Also, after you get your first coat of gel coat on be SURE NOTHIN is sticking out like a little hair or a darn fly leg, NOthing.

Then do the rest of the coats just as meticulously. If not air will sure run through the mold backing material, so if the gelcoat has i minor hole your part will be ruined one way or another.

when you have a bag leak it is faster, if it weaps out after ike 2 mins I bet its your mold, especially if it is a new mold!



Because of this I pressure check every mold I make before I sit there and polish it out. Actually thats where I need to work next, getting a high ball shine on my molds to get that mirror finish with just a light buff.

AND if you got a piece in the works right now thats leaking, you cant leave the pump on or you will suck enough resin out of your part to make it look bad. However you MAY be able seal off the resin in and out lines, then slip a small hole in the leaking bag away from the flow mesh, and feed just the hose in that and seal it with the tape. if you are sucking air from the mold from somewhere the mesh is not then you may be able to hold pressure with the vacuum pump without suckin much resin.



If Brute Force Isn''''t working your not using enough...

I suppose double vacuum bagging would keep the first bag compressed. A lot of extra work though.

Fred

Help!!

Well I just did another attempt at getting a perfectly sealed bag. IT DID NOT SEAL AGAIN! There is absolutely no way I have a leak from the perimeter tacky tape seal. I did have a perfect seal at first, but as soon as I let the vacuum out to shift the bag and re-vacuumed I could no longer get a perfect seal. Big disappointment! I was starting to think a perfect seal was a myth that only worked in the UK.

So, I needed to make a flat panel so I tried for another perfect seal infusion.( I am using the green fine flow media.)

I suspected from earlier failures that the flow media is making microscopic holes in the bag wherever you have cut lines. When I let the vacuum off to shift the bag. (in the example above) the punctures got worse.With this in mind I placed a layer of vacuum bag over the flow media to protect the outer vacuum bag. I did get my first perfect vacuum.

I infused and sealed off the vacuum line, the feed line and left it over night. I expected the worst, but the vacuum held and I had a good part. This is the first time I have left a part cure without leaving the pump running all night, its a bit scarey.

To anyone who has an ultra sonic leak detector, please let me know how well it works. With my leaky bags there was no chance of finding the leak with my stethiscope over the whole bag surface.

Thanks

Fred