edges of panel under vac

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

  1. fallguy
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    fallguy Senior Member

    from Gurit

    RESIN UPTAKE WHEN WET LAMINATING All core materials are porous so the level of resin uptake must be taking into consideration. Lower density cores with a larger cell structure will absorb more resin, as will cut patterns with open structure. To reduce the resin uptake when wet laminating it is common practice to prime the surface before laminating begins. The priming resin will be of the same type as used for the laminate, but with the addition of 4% silica to thicken the resin to reduce resin uptake. Once applied the primer layer may be left to tack-off before commencing the lamination. Typically 100-300g/m2 is applied.

    RESIN UPTAKE WHEN INFUSING
    Taking account of the resin uptake of a core is more critical when using infusion than wet lamination or prepreg as the amount of resin used cannot be controlled. Indicative resin uptakes for different core materials are given in the table below. Panel Resin Uptake is the mass per m2 of resin absorbed during infusion into both sides of a piece of foam. All values given are for plain format core only. Cut, grooved or perforated cores have higher resin uptake due to the open volume of the cuts. The function of the cut or groove is to allow the sheet to conform to the mould shape, so the resin uptake of these finishing options is not given as it is mostly depends on the amount to which the cuts and grooves are opened or closed.
    The resin uptake of plain foam cores is independent of panel thickness for foam cores as resin is only absorbed into the open cells on the surface. For untreated foam core the resin uptake increases with reducing density due to the relative increase in cell size. The particular cell size of Gurit® G-PET™ results in relatively high resin uptake. However, Gurit® G-PET™LITE has a thermally sealed surface which significantly reduces resin uptake whilst maintaining peel strength.
    Type Core Resin uptake (kg/m2)
    Gurit® Corecell™ SAN
    M80 0.71kg/m^2


    Okay, this I misread. I honestly looked at the chart first without the definition. So, I think I will modify my rates to the 350 number you cited Andrew. Thanks a million-this is more rational than me being off by a factor of 5 or more. I guarantee the 100 rate is low.

    As for your last question, the veil is not responsible for the wetout difference. The bottom laminate has been extremely difficult for us to wetout, the rebates and the method are largely the reason I believe. We have either poured the resin above the table or veil, or on our early parts, we poured from above. When pouring above only, wetout is a bear to get the glass through the 90 degree biax fiber angle. I should consider using bristle rollers even, but worried about runs. When pouring below only, we are using excess resin and it is essentially impossible to get the resin amounts perfect on the table and up onto the rebates. When we vac, we can see the areas that were resin rich. But even in those areas we were resin light between the core and the fabric. A solution to this would be to reduce the pour on the bottom and pour more epoxy onto the top of the table side glass. This way, we could move more resin to needed areas, and perhaps use a bristle roller to get it down into any tough spots.

    I am going to continue to use veil, but I am going to stop using it on any surface that is not seen, unless a test bulkhead. Without the veil, I am getting grooves in my surface that follow the raw fiberglass 0 strands. Yes, raw. Interestingly, S3 also told me they prefer Volan A coated glass.. But I already have over 800 pounds of raw glass in house, so I need to use it.

    Anyhow, this week, I will build a bulkhead with these new methods and see what happens.

    We will do the following.

    XSLOW RESIN
    Peelply and veil wetout from above at 14g/m^2
    Pour half of the resin for the table side lamination and even out with foam roller, or 60% resin to glass.
    Glass
    Pour the other half of the glass onto the top, reserve a bit for dry spots, 60% resin to glass for a total of 120%.
    Use a rate of 350g/m^2 on the raw core.
    Lay the core
    SLOW RESIN
    Apply half the resin to the top side of the core using a rate of 110% total instead of calculating any additional for foam.
    Apply the glass
    Apply the other half of the resin to the top side of the glass, reserve a bit for dry spots.

    Bag it.
    Watch the clock and turn on at 100 minutes and not before.

    IN a hurry, no time to edit
     
  2. fallguy
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    fallguy Senior Member

    Quickly, though, it appears not enough resin was between the core and glass and too much resin was between the table and the glass and when it moves, it does not move laterally, but vertically through the panels, which is why the parts are all perfect near the holes
     
  3. AndrewK
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    AndrewK Senior Member

    No sizing on your stitched glass fabric? are you sure?? I would be very surprised if that is the case.
    I did say earlier that I suspected that you are floating your laminate on top of the resin. Adding more resin than required is not the best solution. I dont disagree with adding a bit more to the bottom laminate but no more than calculated on the top, I use the calculated amount for the job and no more but do rob the top laminate slightly to make the bottom a bit more rich knowing that it will migrate to the top as it is compressed.
    Making the rebates on the table side complicates things, the only way to have no voids consistently is to infuse. Infusion is not difficult providing you bagging skills are up to the standard of having no leaks.
    I also mentioned in your other threads that using different hardeners may have consequences on the final laminate properties. I am not saying not to do this just be aware that it is not just about controlling gel time, you need to have all information on hand when making choices.

    I still say ditch the veil if you are having trouble with trapped air in the bottom laminate when the 0deg tow is table side then flip this around, have the +45/-45 on the table.

    If you would like to discuss more over Skype send me an email, late evening your time would work.
     
  4. fallguy
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    fallguy Senior Member

    Yes I'm sure no treatment. Told so by the vendor. It is absolutely a factor based on my reading and the epoxy vendor. I should have used the same vendor for epoxy n glass. Who knew?

    After I build a test panel, I will get back to you with results and advice. We can skype then.

    My BH do not need rebates and RW said no internal rebates, so am considering making a stock panel with rebates for testing.
     
  5. rxcomposite
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    rxcomposite Senior Member

    Our purchaser bought fiberglass from China. Turned out it has no surface treatment or sizing. It is very hard to wet with polyester or epoxy. We would get dry spot from coin size to fist size. Had to throw away tons of that stuff.

    Volan is a finish compatible with epoxy or poly. Silane works also as well. There are other finish specific only to type of resin being used.
     
  6. fallguy
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    fallguy Senior Member

    That is the stuff I have...

    I am going to buy bristle brushes and consider wetting out in reverse and rolling up wet and rolling back out.

    But it is really difficult.
     
  7. fallguy
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    fallguy Senior Member

    I wish it could be treated by me, but it requires drying and everything.
     
  8. fallguy
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    fallguy Senior Member

    Andrew-in my reading it says sizing is required for weaving fabrics, but the sizing is cooked off with heat or chemicals, then a treatment might be applied. Not in my case. Fabric is raw with sizing cooked off only.
     
  9. rxcomposite
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    rxcomposite Senior Member

  10. AndrewK
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    AndrewK Senior Member

    Can you take it back? if not infusion may be the only way to get a decent wet out.
    Post photos of the test panel.
     
  11. fallguy
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    fallguy Senior Member

    I can't do the test panel today. I am going to add bristle rollers/bubble busters to the mix. Look for a post perhaps Wednesday 11am cst.
     
  12. fallguy
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    fallguy Senior Member

    Wow. I got the veil tds and it says 320g/m^2.

    Not going to use that everywhere. ######s
     
  13. rxcomposite
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    rxcomposite Senior Member

    Are you sure that is veil? Veil is available in 30 grm/m2 or the heavier one in 50 gr/m2. It is very thin and has the opacity of an onion skin. Chopped Strand Mat (CSM) is available in 280, 300, 450 gr/m2.
     
  14. fallguy
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    fallguy Senior Member

    TDS attached on the veil....but it isn't right....the veil I have isn't 71" wide ?? I'll mention it to the vendor...unless it comes in different widths and they gave me the wrong width is all?

    They told me it was epoxy compatible, but they make a non-soluble in styrene version. Seems like that would be the epoxy version, but what do I know. I just got the TDS today. I am not the wisest customer on some of these. The mat is the resin sucking monster. 320g/m^2 on both sides of my glass is resin absorption rate, not the weight of the veil

    I was told today that stitched or knitted fabrics do not have a treatment by one person. Another person told me fiberglass can't be woven without treatments. I read somewhere that the treatments used for weaving are not the same as the treatments used to help resin flow. Does anyone know a vendor that would sell 22 ounce triax in the US? I asked to get the TDS for the fiberglass I have.

    turns out I needed to get the TDS before I made the purchase..... I sort of overtrusted the vendors to help me get the right stuff....

    but didn't you say the ratio was about 12? The weight of the veil is 26g, so 320/26 is 12.3...isn't that what you meant?
     

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  15. rxcomposite
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    rxcomposite Senior Member

    Right. Or the easiest way, multiply by 12 the unit weight of the veil by 12, so 26(gr/m2) x 12 = 312(gr/m2) resin requirement. Multiply by 15 if you want a shiny resin rich hand layup outer layer.
     
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