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Chris Rogers
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On the tacky tape thing - one tool that I really like is an aluminum roller with a handle and smooth radiused edges for rolling over the tape and pressing it down. You can make holes in the bag if you swerve off the tape but it is a great tool for when you're still trying to get a better bag and your thumbs are tired. Heat helps too - if you are working in a cooler room going over your sealant tape with a heat gun (or better - a hair dryer because its not as hot) and roller will often get you the last bit to get over your drop test or hit your target vacuum. I don't remember where I got mine but it looks like this: https://www.bestmaterials.com/images/MR08580-large.jpg
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Hanaldo
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Bagging tape definitely has an expiration date, it gets less tacky as it gets older. This is one reason I like the Cytec and Easy Composites tapes so much - they start off very tacky, which means that even as they get old they retain quite a good tack, and they are very pliable, which makes working them harder that much easier.
The AT200Y suffers badly with age. It is ok when it is brand new. But even by the time it is a year old, it has lost a lot of its tack. And because it is so firm, it is very taxing to work it and try to get it to stick properly.
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Sustainablecatamarandesign...
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Thanks Hanaldo, being new to resin infusions I've been going through a really steep learning curve and had difficulty eliminating leaks I couldn't hear (pretty easily down to 30-60 millibar with a 6 cfm robin-air two state pump but taking days trying to track down leaks enough to get to 2-20 millibar...) and coincidentally enough I have been using AT200Y.
Is shelf life/storage of the tape also something to be very concerned with or simply relatively conscious of (working in Hawaiian heat where 85 degrees F in the shade but using freshly purchased tape, some of which doesn't have expiry date or manufacturing date...).
Best regards and thanks a million your advice may have saved my sanity trying to find leaks,
Dave
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Hanaldo
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There's so many, I've barely scratched the surface. But, I wouldn't use Airtech AT200Y or GS-333T again. Just awful.
My absolute favourite is Cytec (now Solvay) LTS90B. The stuff Easy Composites sell isn't bad either, but not quite as good as the LTS90B.
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Sustainablecatamarandesign...
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Hanaldo, any particular brands/grades of bagging tape you particularly recommend using or avoiding?
Dave
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Massimiliano
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+xGood tips above, but just to add one: Put a lot of effort into pressing down your bagging tape. I think until you realise how tiny a leak has to be to cause problems, you won't realise how much effort it can take to get the bagging tape to seal. This is especially true if you are using a firmer or older tape, there are many different grades and some are much easier to get a seal with than others. But even the soft ones can often take a lot of pressing to fully close a tiny air passage, and if you try to take a shortcut and not work every inch of your seal, then there's a good chance you will miss the leak. My thumb nails will often feel bruised for days after an infusion, that's how much effort it can take. It is finicky stuff, sometimes you can throw the bag on and barely put any effort in and pull a 100% vacuum straught away, and sometimes you will work and rework every inch of the seal 2 or 3 times and still have a leak, and it's only on the 4th time around while your thumbs are screaming for mercy that you magically press the right spot and the leak is gone. Following beliblisks tips will improve your chances of getting a full seal without the pain, but if you've done all that and still have a leak, you're better off spending your time working the bagging tape than you are searching around with a leak detector. To answer the original question - I've got a Bacharach Tru Pointe 2100. It was hideously expensive, it works well. It has probably paid for itself by now, but I do this every day and have been for 8 years. I would estimate it has probably found 1 in every 25 leaks that I have had in that time. For the hobbyist, those aren't great numbers. Ultrasonic leak detectors are ok, but I would consider them luxury equipment for the professional rather than essential equipment for everybody. Nail your technique and put time and effort into the bagging tape, and 24/25 times you won't need the expensive gear. Thank you all for the usual diamonds I receive from you! I will put more attention to the digital gauge. I made an infusion last week and despite pressing the seal many times I was not able to pass the drop test. I then borrowed an ultrasonic leak finder from a friend and was still not able to spot the leak! Long story short, I trashed the bag and the seal, used new seal and new film... drop test passed! I know to cover the spiral with peel ply, I have learnt today to cover the edges of the infusion mesh too... thanks!
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Hanaldo
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Good tips above, but just to add one:
Put a lot of effort into pressing down your bagging tape.
I think until you realise how tiny a leak has to be to cause problems, you won't realise how much effort it can take to get the bagging tape to seal. This is especially true if you are using a firmer or older tape, there are many different grades and some are much easier to get a seal with than others. But even the soft ones can often take a lot of pressing to fully close a tiny air passage, and if you try to take a shortcut and not work every inch of your seal, then there's a good chance you will miss the leak. My thumb nails will often feel bruised for days after an infusion, that's how much effort it can take.
It is finicky stuff, sometimes you can throw the bag on and barely put any effort in and pull a 100% vacuum straught away, and sometimes you will work and rework every inch of the seal 2 or 3 times and still have a leak, and it's only on the 4th time around while your thumbs are screaming for mercy that you magically press the right spot and the leak is gone. Following beliblisks tips will improve your chances of getting a full seal without the pain, but if you've done all that and still have a leak, you're better off spending your time working the bagging tape than you are searching around with a leak detector.
To answer the original question - I've got a Bacharach Tru Pointe 2100. It was hideously expensive, it works well. It has probably paid for itself by now, but I do this every day and have been for 8 years. I would estimate it has probably found 1 in every 25 leaks that I have had in that time. For the hobbyist, those aren't great numbers. Ultrasonic leak detectors are ok, but I would consider them luxury equipment for the professional rather than essential equipment for everybody. Nail your technique and put time and effort into the bagging tape, and 24/25 times you won't need the expensive gear.
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Chris Rogers
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I agree with everything said here about process - and the digital gauge will tell you a lot - especially about when you finally find the leak! Generally this level of awesome bagging is an infusion or pre-preg (especially autoclave) thing - where leaks are more catastrophic. Random note: probably half the hardest to locate leaks I have ever found in infusion bags are from cut edges of the flow mesh poking through the bag. Plumbing and quick-connect fittings are a usual suspect too. My experience is that a leak detector / ultrasonic listening probe is a last resort... when you still can't find what is up - your drop test isn't good enough - and you have chased the bag edges down and checked all the penetrations. Probably people making airplanes use one every day but as a boatbuilder it's been only a special occasion tool. I have a beat up old Amprobe one with the earphones which is just a super-sensitive version of putting your ear to the bag - not a magic wand! It is way easier to use one with earphones than just the LED lights. Good over-the-ear earphones are very nice too. Using one is super annoying if you have a large or complex bag and sometimes you find the leak easily and sometimes you have to go back and re-bag the part anyway. Moving and crinkling the bag is really noisy and small leaks are only easy to hear once you get very close. Finding a leak in the middle of a huge bag is hard - finding one in the sealant tape or in plumbing is easier. I've heard about using a thermal camera to find leaks but haven't done it - I guess they show up cold. Anybody do this before?
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beliblisk
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Just be methodical. Hers few tips: -Clean working space helps (i vacuum my small workshop befor applying vacuum bag)
-i apply perimiter seal tape prior to anything else so it seats on clean sourface(add pleats later on)
-seal silicone inserts from the inside as well
-watch for stray fibers
-make big enough bag
-double tape on pleats
-take your time(you will get better and quicker soon)
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Massimiliano
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+xI do prefer a digital gauge over a leak finder, too. If you are careful with your bag the leak is always at the sealing tape. And a digital gauge helps finding them a lot quicker and much more reliable than an ultrasonic leak finder. Thank you all for the replies. I do have a digital gauge, but still not have enough experience to match the vacuum loss to a specific issue...
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