How to get a perfectly sealed bag?

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How to get a perfectly sealed bag?

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fgayford	fgayford posted 13 Years Ago HOT Topic Details
Group: Forum Members Posts: 433, Visits: 1.2K	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
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Dave	Dave posted 13 Years Ago HOT Post Details
Group: Forum Members Posts: 48, Visits: 253	With regards to getting a full seal If you are convinced it is the bag then there are 4 areas where the leak will be. This is assuming you are using resin infusion method or vacuum bagging. 1. Most obvious - The gum tape sealing the bag to your mould or the bag to itself. Best way to prevent this - Patience and good practice. When sealing your bagging film take your time and remember to compress the gum tape with your fingers all the way around the mold. Try to not crease or wrinkle the bagging film in any way. Make sure there are no obstructions however small they may appear, for example a single carbon filament that has got caught in your gum tape could cause a tiny leak. 2. The through bag connectors for your tubes. There are a few methods to make sure a perfect seal every time. If you are infusing then try to prevent the bag from creasing/wrinkling when you put the tubes into the silicone connectors and make sure some gum tape goes with the tube slightly into the connector. These are slightly more unlikely but you never know: 3. The bag! Make sure when you cut your bagging film and seal it to your mold it is done in a clean environment as small amounts of dirt/tiny stones can puncture your bag to the point where it will only start leaking when you pull vacuum inside the mould. These are very difficult to detect but easy to prevent with a clean and large work space. 4. Your mould! If there are any cracks in the gel coat then you may want to check that out. That's about all I've ever seen go wrong. If you assess these areas systematically you should find your leak or more importantly prevent one from occurring. Also when you pull full vacc or as close to as your pump can, most pumps will slightly change in the sound they make. Try it with just your catch pot attached to hear the change in tone. Not sure if you were asking this but your pin hole and void problems: This can be a number of things mainly the one you have already addressed which is having your vacuum pump on for long periods of time. If i want to make a cosmetically perfect piece that is maybe 1-2% heavier i will shutoff the vacc port just before the inlet port (i don't run the pump for any extended period after infusion unless it is a particularly huge infusion). This usually prevents any pin holes. If you are still having issues then it could be resin having lots of air in it, contours of your mould being too sharp or stopping the material laying into it properly and a number of other things. Hope this helps, Dave.
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Matthieu Libeert	Matthieu Libeert posted 13 Years Ago HOT Post Details
Group: Forum Members Posts: 955, Visits: 3.4K	an additional remark/hint: I always tape of sharp edges of the mould with ducttape for example... sharp mouldedges could punture the vacuumbag when vacuum is pulled Matthieu Libeert Founder MAT2 Composites X Sports website: www.mat2composites.com
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fgayford	fgayford posted 13 Years Ago HOT Post Details
Group: Forum Members Posts: 433, Visits: 1.2K	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
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