edges of panel under vac

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Sep 6, 2017.

  1. AndrewK
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    AndrewK Senior Member

    Purpose of veil is to have very resin rich surface for applications such as chemical tanks. It is not intended to be vacuum consolidated, most of the resin is going to be squeezed out and wasted.
    I thought you were only using it on the table side.
    Were you told to use it right up front or only as a solution to the trapped air in the bottom laminate?
     
  2. fallguy
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    fallguy Senior Member

    I should add one more thing. Another friend of mine recommended more of a suface for abrasion resistance, so the veil was really only desired on the exterior of the boat where any abrasion might occur and since we had lines from the 0 strands as well. Point is, I will not use veil on any surfaces that don't matter much like bulkheads or anything on the inside, and I won't use veil on the top surfaces(of the table). I did do a test panel today.

    We wetout the peelply and veil at 355g/m^2 with the extra slow hardener. I tried to wetout the peelply, but it was useless. We laid out the peelply and wetted it with that amount. We then put down 50% of the rate of 120% for the glass, then laid the glass, then put the other 50% above the glass to be able to move resin to places where needed. We wetout the corecell at .35kg/m^2, which was a lot. Then we waited 15 minutes until we got to 50 minutes to duplicate a larger panel.

    Then we rolled out the corecell with slow hardener at .35kg/m^2, then half the 100% rate for the top glass. Then we poured the balance on top of the glass.

    It was by far the smoothest wetout we did, although plenty of resin dripped off the part.

    I also put some small sand in Ziploc bags on the edges of the part to try and avoid the vac bag creating a cove around the edges, and we pleated the short sides of the part and tried to work the bag down a bit and definitely had cleaner looking edges.

    We also waited and did not turn the vac on until 100 minutes. This was probably a little bit of a mistake as 90 minutes would have been better. There was no appreciable difference in my breather saturation, in fact it was less than my last part, which I found to be strange. But in hindsight I think we turned on the vac at 85 minutes on the larger panel (crew of 3), and we had xslow resin that was probably only 20 minutes into its 120 minute cure at that time.

    I will give a picture of the result tomorrow.
     
  3. fallguy
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    fallguy Senior Member

    So we did a test piece using all new numbers and wet out methods. It had bubbles in it. But, the bubbles were on the edges and not like before. A couple notable possibilities might have caused the bubbles. At the end of the bottom side wetout, I added a little resin from the bottom of the bucket for good measure-not a great idea, it is possible the rebate held the edge up one one side, and I never ran above 14".

    After discussion with the crew, we decided to run the big panel at much higher pressure today. The vac is turned off in an hour (8h). And in the morning, we'll check it out.

    My first panels were run with higher pressures and had no flaws. Only since switching to the xslow and lowering the pressures have I encountered issues.

    There was pretty significant bleedout on the bigger panel, so I think I could drop the wetout rates for the core bottom to 320 and the top to 300. We turned on the vac at 3:47- 100 minutes into the xslow and 47 minutes into the slow hardeners.
     
  4. fallguy
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    fallguy Senior Member

    Air when we set the wetted core on the bottom laminate is getting trapped between the core and wetted bottom glass under the topside fiberglass and that is the primary problem. We will stop doing two sides on the vac table so we get flow from the bottom side. There is nothing flowing out of the bottom. Our air bubbles have been varying based on how much air presents when we flip the panel over. If we use more resin to wetout the core; that resin flows a bit on the flip of the panel creating ridges and air pockets that deform and change under pressure, but they have no means to escape.
     
    Last edited: Oct 13, 2017
  5. Tungsten
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    Tungsten Senior Member

    Your ex slow hardener should give you a couple of hours at least of open time if not more.Tests will confirm just how long you have.
    Have you weighed the breather before and after so you know just how much resin per sq/yd is being sucked out?
    Detailed pictures of each step would help a lot.
     
  6. fallguy
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    fallguy Senior Member

    We are just going to stop trapping resin under the topside glass and things will flow then.
     
  7. rob denney
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    rob denney Senior Member

    I have not read all your posts, so feel free to ignore this if I have misunderstood. The following is based on 30 years of vacuum bagging and selling materials and advice to pro and amateur builders and 5 years of infusing, culminating in Intelligent Infusion INTELLIGENT INFUSION – Harryproa http://harryproa.com/?p=1845.

    1) Vacuuming should be at atmospheric pressure or as near as you can get, unless you are using ester resins, some of which have important volatiles which can be boiled off under full vac. Vacuum should be applied as soon as possible after the resin.
    2) The purpose of the bleeder is to pull out all the air and the excess resin. If it is fully wet out, either you are using too much resin or not enough bleeder. As long as there is an adequate path for the excess resin to flow along towards the pump (via a resin trap or you will destroy your pump), a fully wet out bleeder is not a problem.
    3) Any cloth that does not wet out when you pour resin on it is not worth the effort. Pouring resin on crappy glass "because you have it" is false economy. Get new triax or use double bias and uni. Triax on a 33'ter seems excessive.
    4) Tissue does nothing and can be left out. As can peel ply and core absorption in your wet out calculations. ie, wet out the cloth, which if you are careful will be about the same amount of resin as cloth weight. When bagged, it will be about 50%. Some of the surplus will wet out the peel ply, some the core, the rest goes to the bleeder and to filling any gaps and edges in the bag.
    5) Infusion works without wetting out the core, no reason why bagging won't as well, as long as the core is adequately perforated and the resin runny enough.
    6) Most epoxy properties are near enough the same regardless of hardner, but extra slow is often a little (not enough to worry about) worse. What can be a problem is post curing, when one side is still relatively uncured. Make sure the panel is well supported until fully cured. Use the slowest room temperature cure you can to reduce the stress of getting the bag sealed. Adding heat (electric blankets or insulation with a blower heater under it) once the laminate is under vacuum speeds the cure and makes the resin thinner, aiding wet out, air release and minimising resin content. As the core insulates the mould side resin, the heat speeds up the other side so they both cure at closer to the same time.

    Suggestions:
    Start from the beginning. Wet out a 1' square sample of easily wet out glass and core and bag it using full vacuum. Then weigh it and destroy it, taking note of the core/glass interface bond. Put a chisel under the glass on each side to get a peel started, then grab the laminate with pliers and tear it off. As long as the glass has foam on it, the bond is as good as it needs to be. Take pictures and post them here or to me at harryproa@ gmail.com for comments. Then work your way up to what your design specifies and see when problems start.

    Infuse. It is far less stressful and more likely to be a success than bagging. Done intelligently, there is no post infusion cutting or grinding of cured laminate and your fit out time is hugely reduced. You will use 40-50% less resin and get a better, cleaner, lighter job. Again, start small and work your way up.

    Composite building should be easy and relatively relaxed, with predictable, consistent, high quality laminates. If it isn't, you are doing it wrong.

    rob
     
    MassimilianoPorta and Dejay like this.
  8. fallguy
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    fallguy Senior Member

     
  9. rob denney
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    rob denney Senior Member

    There is no reason (either logically or from experience) why any of the topside wetted glass, combined with breather film, combined with the veil, combined with rebates, combined with a slow hardener on the topside on our last two parts, or rivers of resin from overly wet out core cause problems.

    Excess resin and air travel upwards through the laminate, core, laminate, peel ply, perforated plastic and breather. The amount travelling along the rebates or the fibres is miniscule and irrelevant. Imagine you are spreading a towel onto spilled water. How much water escapes out the edges and how much is absorbed into the blanket?

    No matter how much resin and air you put in the fibreglass and under the core, it will be removed if the vacuum and breather are working and the resin is liquid. For exactly the same reason that bubbles blown through a straw will rise to the top of a glass of water, and water sucked through the straw will rise up the straw. If you look at the problem and your solutions from this point of view, it may help.

    What are you using for a bleeder? What is between it and the laminate? Is the vacuum reaching all the way across the job? You should not be able to lift a pleat in the bag using finger and thumb and pulling hard. Are the perforations clear? Check a few on each sheet and use a vacuum cleaner if they are blocked. Is the breather breathing? Spread it across your mouth and breathe through it. Is the resin still liquid when the vacuum is applied? Keep a teaspoon of your first batch separate and refer to it when the vacuum is applied. These are elementary questions, but one of them is probably the cause of your problem.

    If laminating one skin and the core works, then it is either a bleeder problem or a gelled resin problem which stopped 2 skins and the core working. You should still use a breather if you bag only one skin and the core otherwise the excess resin will remain on the job, and the vacuum may not extend all the way across.

    Apart from using the xslow resin, none of your solutions will help (logically or from experience). Not using bleeder will make the situation worse as the excess resin remains on the job and the vacuum may not travel all the way across the job.

    Adding infusion grooves is trivial compared to the effort you are expending on wetting out the laminate. Set up a skilsaw with a skinny blade 1-2mm deep and run it along your core at 2" centres. Or use perforated plastic and infusion medium. The resin used will still be much less than what you are throwing away at the moment.
     
  10. fallguy
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    fallguy Senior Member

    I would have liked to try infusion. But I think getting shown how to do it to avoid a dry area in the laminations would be important. I offered to pay someone and even per diem and out of pocket to show me on this very site, but had no takers. I am in the middle of the US in Minnesota, not exactly boat builder paradise.


    Here is the full detail of how the part that failed was made. You can see that I was pushing the geltime on the topside lamination a bit.

    XSLOW RESIN for this part 2:07p mix time (120 min gel time)
    1. Rebates are taped on the vac table all the way around and form a pond, if you will. Approx 24" x 33'
    2. Section is waxed
    3. peelply and veil are laid down
    4. veil is wetted
    5. half of the resin for the bottom glass is rolled out evenly
    6. bottom glass applied
    7. rest of resin is applied with paint roller
    8. laminating roller is used to remove all air and move resin up onto the rebate edges
    9. corcell is wetted at 350g/m^2
    10. corecell is flipped
    11. minor fill was done with 50/50 cab/balloons as this part had high density sections and some staples to fill

    SLOW RESIN for the balance 2:47 mix time (60 min gel time)
    12. wetout of core on other side at 350g/m^2 (way too much as it was already wet some from the 2" oc perfs
    13. half the resin is put down for the glass and evened
    14. top glass wetted out
    15. peelply
    16. perf'd plastic or breather film as I call it
    17. bleeder
    18. bagged

    Turned on vac at 3:44pm, a few leaks to deal with, had 26"Hg at about 3:50p, time to gel for xslow is 4:07p, time to gel for slow is 3:57p.

    The vac runs, bleeder saturated, not fully, but pretty good, no resin in vac lines though. At some point things gelled up and locked in the air bubbles.



    I will not use slow resin again!

    But I highly doubt the extra 10 minutes I had on the xslow resin gel time would have resulted in a significantly different story. I believe the perf'd plastic or breather film a/o gel times is stopping my flow. So, the best solution might be to only do one side of the panel at a time which would result in lots more open time; perhaps too much. Otherwise, if I try to do both sides, I will for sure saturate the bleeder fully and probably run resin into the vac lines a bit. But if that is okay, then let me know what you think. If I only do one side at a time, I might still be able to use the perf'd plastic and get a good result and not lose too much resin out of the part?

    Thanks!!! I really appreciate the expert feedback. These are very expensive errors. Perhaps I need to expect to run resin into my trap? I have not done so to this point. In fact, no resin has made it into any of my intake lines, but I have wrapped them with bleeder.

     
  11. AndrewK
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    AndrewK Senior Member

    Fallguy, a few final comments from me and then I will leave it to Rob to guide you further, as I imagine you are getting frustrated with differing advice.
    1. Post some pictures, this will help advice given and perhaps the panels are not as bad as you describe and advice may be that there is no need to scrap them, perhaps.
    2. Ditch the veil as this is an unnecessary complication, if you want to increase the surface abrasion in certain areas use 200gsm plain weave glass instead or 135gsm kevlar. But I caution the need to do this in the first place, simply stick to your design and it will be fit for purpose. It can be a common trap to add a bit more here and there and all you end up with is a much heavier boat with questionable improvement to strength or serviceability of the structure.
    3. If you have reached the point where you dont want to invest any more time to perfect your vacuum bagging process then forget the one sided at a time bagging. This is very inefficient with time and materials. There is nothing wrong with a 1:1 glass:resin open laminate.

    My offer to skype still stands if you want to talk further, vacuum bagging or infusion.
    Cheers Andrew
     
  12. rxcomposite
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    rxcomposite Senior Member

    The veil may be important if you want a super perfect finish as good as your mold. As the resin shrinks after curing, you will see the weave pattern. However, if you are painting your boat, A microbaloon laden primer will hide the imperfection. Only a few grams difference/m2 in weight + added process.
    I don't use veil in hidden structures like the bulkheads. Peel ply both sides works best for better grip and reduced sanding.

    There is still another process we use as a substitute for wet bagging. We saturate the fibers with resin and place a plastic film (non stretch bagging film) on both sides and squeege the excess resin out to sides. Works for single skin laminate, non cored. Works also for tabbing. We cut the laminate while wet using a pizza cutter, stick it into the part and peel off the backing layer. A short stiff brush is used to form it into place.
     
  13. rob denney
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    rob denney Senior Member

    There is no point in trying to reduce bleed out. Quite the opposite, you want as much resin out as you can get. Do a sample with more layers of bleeder than is required and see if any of the cloth is resin starved. Autoclaves work at 6 atmospheres without resin starvation. Put a piece of wet towel in a vice and clamp it as tight as you can (much more pressure than atmospheric). It will still be wet as you cannot squeeze wet fabric dry. Resin starvation is a function of poor wetting out or relaxing the pressure before gelation, not too much pressure or too much resin removal. Put the wet towel in the vice with multiple layers of dry towel each side and squeeze. The wet towel will still be wet.

    Perf plastic is to allow you to get the saturated bleeder off. If it is restricting the flow too much, run over it with a prickle roller (might have to make one using drawing pins and an old resin roller) to make more/bigger holes. Leaving it out will mean grinding off the resin saturated breather which is no fun at all. Peel ply will not work as a substitute.

    Do whatever it takes to get all the surplus resin and air out. If this requires multiple layers of bleeder and/or a full resin trap, so be it.

    Don't apply any more resin than required to wet the cloth ie, the same weight of resin as cloth. Misers like me apply the last layer of cloth dry and let the surplus resin wet it out under vacuum. Not recommended for single layer triax, but if you used db and uni, it is worth experimenting.

    You are pushing the gel time too hard. The resin under the core is insulated, so gets warmer than ambient, and cures quicker, so allow some time for this. Eliminate the unnecessary steps such as wetting out the veil (the veil itself is a waste on a panel boat, but doesn't slow down the process if you don't wet it out), rolling to remove the air (the vacuum does this far more effectively than you can), wetting out the core (do the peel test from my other email first to put your mind at rest) and the minor filling (the resin will fill any gaps).
    Use the Xslow, spread it quickly (pouring it over the job and spreading it with a wide squeegee is quicker than rolling) and work in the cool part of the day and/or cool the resin to 25C or lower (be careful with this, cold resin does not flow as well as warm). Pre measure the resin and hardner so they only have to be combined and stirred.
    Consider whether triax inside and out is overkill (it is for any 33' sailing cat I have ever known), particularly at the ends and low stressed/highly reinforced parts of the panel.
    Work fast, even if it means a little sloppiness.
    Before you mix resin, seal one long side of the bag including the outlet onto the table and apply the tacky tape to the other sides of the bag. Brown tape the table where the tacky tape goes and remove it after the wet out is complete so you have a dry area to seal onto.
    If you still don't have enough time, get more helpers or longer gel time resin (xslow, room temperature cure, thin laminate open time epoxy here is 330 minutes). There is no such thing as too much open time.
    If you still can't get it bagged before gelation, lay up the skins separately, or make smaller panels with rebates so you can join them. Or infuse.

    Re wetting out the core: The resin forms a liquid skin over the indentations (which are cut open bubbles of foam) and only wets out the foam if the air under the skin can escape. Unless the indentations are filled, you are only sticking to the edges. I am not sure what the pressure is that causes the air to blow through the skin, but I am pretty sure it is considerably less than the one atmosphere you will get when it is bagged. Using thickened resin makes it harder for the air to escape. Squeegeeing it does not help. Heating it with a hot air gun does (the air expands, the resin gets thinner), but this is a waste of time and the heat may lead to premature cure.

    Your plans are seriously deficient if they have not covered most of the points above, and the rest of them in discussions with the designer after you threw away the first panel.

    I can't visit, but if you want to set up an infusion panel and Skype me (harryproarob, email me first so I can turn it on) with a camera phone, I can help you through the process. I know of no one who has infused large parts who would revert to wet laminating (or ply, or strip). Ditto for Intelligent Infusion vs conventional fitting out with edges to be filled, bulkheads trimmed, fillets/tabbing, cutting/grinding and getting sticky and dusty.
     
  14. fallguy
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    fallguy Senior Member

    Thanks Rob. Yes, the gel time was pushed for sure. A major factor in the problems was that my first 5 parts I made before using perforated plastic were great, so I didn't even know I had a problem. They were smaller though. When I started to make the larger panels is when the troubles began. Then I thought the core wetout rate was the issue. The one common element in all the large panels vs my early samples was the perforated plastic. It breathes, but perhaps not enough before our gel times. Now that I added resin to the core wetout; more air is introduced when we flip the part. That air is the bugger and my use of slow resin on the top of the part locked in in before it could escape. Work is done in a building that is 72F or a bit less. Sometimes we open the door if it gets warm, but our climate is relatively reasonably controlled. S3 would not recommend XXSLOW resin for this job because it required heat blankets and such.

    Breather saturation is my only concern, so some reduction in resin where possible and perhaps a 2nd bleeder layer. Almost all your advice on speeding wetout has been done with the exception of the veil wetout and time with too much time on careful wetout of the triax, but we do take extra time around the edges to get the rebates wetted. The last part was the first time we had epoxy near the gum tape-lesson learned.

    Things might have been fine with just the same resin on the top......

    I will run 4 samples Monday. One will be everything the same with xslow resin, one will be without breather film (although you are concerned about this), one will be no glass on the top side, but wetted peelply with breather film, and one will be no glass on the topside without breather film and double bleeder. Best part will probably be what I do next. The singlemost common denominator in parts that were good versus parts that were not perfect and had varying degrees of problems is the perforated plastic. The second common denominator might be the core wetout rate. Another common issue big vs small would be gel time, so I am going to try to get my samples done at 80 minutes before applying vac. I think we can do any of the above at 80 minutes on larger panels.
     

  15. fallguy
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    fallguy Senior Member

    Thanks RX. Yes, no veil will be used on anything that is out of view. I did use veil on on of my BHs I did for a sample, but I definitely won't be adding veil to much of anything on the inside of the boat otherwise; not worth the headache. I am even considering ditching the veil on the inside of the cat hull exterior. If it hits a dock; I'm in trouble!
     
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