Edge rebate for glass tape joint

Discussion in 'Materials' started by Stefano Dilena, Aug 19, 2021.

  1. Stefano Dilena
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    Stefano Dilena Junior Member

    May have been discussed before, but could not find the right info on previous threads.
    The following being relative to 20mm PVC core infused panels, 600g/sqm reinforcement each side.

    In the image attached, at the centre is foam core, in red the original reinforcement applied by vacuum infusion, and in purple the glass tape.
    The design calls for tape joint with 2 extra layers in the configuration at the top.

    Is making a rebate with a router on the panels so that the tape layers end up flushed ( bottom configuration) a bad practice? This would reduce the effective thickness of the foam at the joint by 3mm( 1.5mm each side)
     

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  2. TANSL
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    TANSL Senior Member

    You must overlap some layers with others, therefore, the solution above in the figure is correct. The solution in the figure below is not correct. Also, the core should have some overlap as well. I do not know how to express the idea correctly in English, I hope the image clarifies what I want to say. There may be other similar solutions.
     

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  3. Stefano Dilena
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    Stefano Dilena Junior Member

    That makes sense, thanks a lot.
     
  4. fallguy
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    fallguy Senior Member

    Typically, the rebates are only made on the outside surfaces in thinner cores like say 12mm.

    You can modify an electric planer to do them.

    The surfaces to be made fair are hogged enough to relieve the tape plans. The glass is applied to the entire panel and then the tapes are done later.
     
  5. TANSL
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    TANSL Senior Member

    I don't think I get it right because if you apply glass to the whole panel, why do you need the tapes?
     
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  6. BlueBell
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    BlueBell "Whatever..."

    I agree, but the design dictates otherwise.

    No. In fact, the tape is likely unnecessary, but configuring it as in the lower image would be fine too.

    Scarfing the foam is a good idea. Are the foam joints fused? If so, how?
     
  7. TANSL
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    TANSL Senior Member

    Okay, of course, design almost always rules, although good practice in shipbuilding (which may force design changes) has to be taken into account. But at this moment I cannot think of a design that could force us to apply the solution with tapes that @fallguy proposes.
     
  8. fallguy
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    fallguy Senior Member

    Of course you can.

    Suppose two panels are made on an infusion table and must be seamed. 124E5C91-012D-4526-A004-219B4446D639.png
     
  9. TANSL
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    TANSL Senior Member

    No, I cannot and, from what I see, you are not capable of imagining a project with a problem that forces you to adopt the solution indicated by you. I insist on my question, if you are going to put glass on the whole panel, why do you need the tabs? Let me answer you: not at all.
    Please answer, if you like, to end this discussion. For my part, it is finished.
    Cheers.
     
  10. fallguy
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    fallguy Senior Member

    Sorry if I was offensive. There is nothing complicated about the answer I gave the OP and this solution is used all the time by builders.

    My finger sketch is crude, but shows the point. I am suffering with a stuck kidney stone, so if I have a tone, it may be from the chunk of salts tearing its way through my ureter.
     
  11. TANSL
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    TANSL Senior Member

    I am very sorry for your ailment. I know that it is very, very painful and I wish you a speedy recovery.
     
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  12. upchurchmr
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    upchurchmr Senior Member

    Foam is so weak, even in good marine versions that scarfing and localized reinforcement is not required.
    The local reinforcement can't hurt, but it should be done next to the foam so the continuous glass will be straight and retain the highest strength.

    If you don't like or don't understand the answers, then make test samples and break them. Might take some cleverness to get good tests.
    Cheap to have confidence in your process.
    Did you ask the designer?
    Good luck with getting a real answer.
     
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  13. fallguy
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    fallguy Senior Member

    If you zoom in on my avatar of the transom step; you can see there is a tape relief on the top edge of the step! Addendum: there is no relief on the top edge because it is so narrow the tape covers the seam and both hullsides and the top in one go (perhaps a bit light I know, but 600/225 tapes)
     
    Last edited: Aug 20, 2021
  14. Stefano Dilena
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    Stefano Dilena Junior Member

    The main reason why I asked os because I came across a this image here that shown the Z-joint in the Duflex panels.. This to me ridiculous compared to a classic tape joint..
    There is no overlap of laminate, and the length of laminate joining to the next panel is half the thickness of the core( balsa core showed).

    Considering the joint technique showed by Fallguy more than appropriate for the job, what is the general consensus of the joint proposed again in the second screen shot below? This should produce a flat surface on both sides of the joint, with only one rebate on each panel( on opposite sides), and without the use of glass tape ( the joint is glass on glass glued with Epoxy).
    The image shows the panels joined on top, and before joining below.
     

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  15. fallguy
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    fallguy Senior Member

    Stefano-I believe you are confusing a joint which is laminated as a whole unit and joints that cannot be...
     
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