eglass tape in a glued joint?

Discussion in 'Materials' started by TwoBirds, Sep 22, 2016.

  1. TwoBirds
    Joined: Aug 2016
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    TwoBirds Junior Member

    I'm gluing a board for a coaming, spruce to luan ply, Titebond 3, will putting fiberglass tape between them strengthen the joint?

    2B
     
  2. PAR
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    PAR Yacht Designer/Builder

    Nope. PVA's don't have any real gap filling properties and the modulus of elasticity isn't well suited for 'glass fabrics.
     
  3. SukiSolo
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    SukiSolo Senior Member

    Not to mention PVAs' are not properly waterproof, ;) even TiteBond3 which has reasonable 'resistance' but nothing like epoxy, resourcinol etc.
     
  4. PAR
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    PAR Yacht Designer/Builder

    Agreed, though TiteBond III does pass the type 1 WBP test, it just barely does. These glues also tend to creep under load and can soften quite a bit if well soaked.
     
  5. TwoBirds
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    TwoBirds Junior Member

    Thanks Guys :)

    so if I used epoxy, fiberglass tape would make the joint stronger than epoxy alone?

    not sure I understand the water resistance bit, I've got a pair of "temporary" oars I made with well over 200 miles on them (at 3-4 knots), glued with titebond 2 with one coat of tung oil, they're holding up just fine, seems like a coaming with two or three coats of paint that might get splashed 2 or 3 times a day should be ok shouldn't it?

    2B
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    A PVA on your combing will be fine with an occasional splash. PVA's require a really tight joint and if they have it, they'll tolerate some moisture. The real problem is with less than perfect joints, that let in some moisture. TiteBond II is water resistant and will release if the wood or glue gets fairly wet. TiteBond III will tolerate more moisture, but tends to deform and lose grip when wet. If allowed to dry out, it regains it's stiffness and grip, assuming nothing moved in the process.

    Placing 'glass fabric between the layers, will not change epoxy modulus properties. If the combing was heavily loaded, like a body falling hard against it (dynamic loading), yes, the fabric will offer some additional help, but in a static load, nothing to get excited about.
     
  7. TwoBirds
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    TwoBirds Junior Member

    Thanks Par, my boat has a fair amount of titebond in it, had me worried for a bit there :)
    sounds like it may be a problem even so, I was worried about starving joints more than getting too much glue :(

    I don't much like using epoxy, could just be that what I have is crap but I have trouble with curing about half the time even in my heated shop, definitely won't buy pro-glass next time.

    2B
     

  8. tom28571
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    tom28571 Senior Member

    No. There are probably some instances where an interstitial fabric might improve a glued joint but, in general, the answer is no. I have built a couple of light aircraft propellers (72" Dia.) and wanted to test this factor which has been suggested in cases where the laminates were fairly tightly clamped. I made several test blocks to test sheer or peel resistance. I am planning to revisit the test again since my first batch gave inconclusive results with no fabric, or absence of, showing superiority..
     
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