Delemma-Hull to deck joint

Discussion in 'Fiberglass and Composite Boat Building' started by Roly, Jan 7, 2010.

  1. Roly
    Joined: Jul 2005
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    Location: NZ

    Roly Senior Member

    Greetings. I have been away earning the bucks to restart my project- sad but true.
    I have a delemma!
    David Gerr specifies overlapped,bedded, & mechanically fixed hull to deck joints
    in "Elements of boat strength".
    There is no provision for fillet & tab type methology.

    Boat is 34' monohull, 20mm glued kauri strip planks glassed both sides. (840gm/epoxy b.s.)

    http://share.shutterfly.com/share/received/welcome.sfly?fid=ee1859e18f46e828&sid=3AcuGzRozZOeA
    No good pic's of what I am trying to explain unfortunately

    I have laid up the deck (epoxy balsa) with no flange for an overlap;Apart from the 20mm overlap of the stip planked hull.
    By flange , I mean a return on either the deck/hull or both, for bolts. I did build a rebate into the mold for tabbing.
    For some reason I assumed DG supported a filleted internal cnr and glass both sides of the hull/deck junction with at least the wt. of glass of the hull both sdes. Seems he doesn't.
    Apart from it being tedious & costly, Is it viable?
    Thx in advance.
     
    Last edited: Jan 10, 2010
  2. Roly
    Joined: Jul 2005
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    Roly Senior Member

    Apparently this type construction of hull/deck joint is common these days here.
    My layup is per below drawing.
    This is not to a rule, rather what has been done and worked. (Proof in service)
     

    Attached Files:

  3. Herman
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    Herman Senior Member

    I also see it in service here.

    Filleting the inside, and glassing it can be a pig, but apart from that, there is nothing wrong with it.

    Impregnate your fiber on a table, and roll it on a piece of cardboard tube. That at least saves you from messing with too much resin inside and upsidedown. (or even better, roll the boat...)
     
  4. Steve W
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    Steve W Senior Member

    As Herman said,dont wet it out in place,do it downhand and then offer it into place,it is easiest to limit the pieces to manageable lengths,say a meter and do both layers together but stagger the joints,also wet out on a strip of peel ply.It of course goes much easier with a helper.
    Steve.
     
  5. Roly
    Joined: Jul 2005
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    Roly Senior Member

    Thanks for the corroboration & tips.
    The db goes on pretty easily. We will do the external tabbing wetout on the boat for minimum fibre distortion & as continuous as possible.
    I am curious to how much glass you guys used? Similar quantities to
    the pdf I included? (Displ. dependent of course).
     
  6. tunnels

    tunnels Previous Member

    First, Roly what part of nz do you live in ?? i live in west Auckland . :p
     
  7. cookie munster
    Joined: Jan 2010
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    Location: Holland

    cookie munster Junior Member

    In the pictures of your build it looks as if you have a deck clamp on the inside of the hull, which would/could act as a flange. Picture only shows front part, not the whole hull. I don't see the clamp in your drawing. :confused:

    [​IMG]
     
  8. tunnels

    tunnels Previous Member

    by the look of the date on the post i would say hes well past that and could be sailing by now . Here in new zealnd there is a flexable type of epoxy that is just what the doctor orded for that type of work . its an epoxy ,semi flexable, sticks like nothing i have ever used before , has a long working time is easy to use and easy to clean up, we did all the 8 deck and transom joins on the match raceing boats i made in South Korea .There was no fastenings at all through the decks they were just glued and not even glassed on the inside !! The outside we had a 5mm groove between the deck and the hull as the squash out area and just coved it and took off the surplus and that was it !!Fantastic stuff
     
  9. apex1

    apex1 Guest

    Would you mind to share your knowledge? Has that product a name?



    And I doubt he finished the boat in the past ten days......................
     
  10. tunnels

    tunnels Previous Member

    HPR25 ,comes in 2 colors ,white or black , its 2 to 1 mix is easy to use , its made by Adhesive technologies ltd here in Auckland nz . Its is west system resin based so has a good reputation . The 36 ft match racing yachts we were making had the decks and the internal floor grid over the keel stub socket ,that included the mast step was also stuck down with HPR25 . The boat in a fully finished condition was lifted from its cradle into the water each day on one single pin that went through the FIBREGLASS floor grid and had a STAINLESS STEEL yoke attached to the lifting strap from the crane .
     
  11. Roly
    Joined: Jul 2005
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    Roly Senior Member

    Sorry, didn't see your post.
    What looks like a clamp there actually is the remains of the old deck.
    All gone now, the frames are gone, & hull is glassed in 660gms triaxial both sides with bulkheads per Gerr's scantlings.
    We have filleted & tabbed the whole interior, hull to deck, and are about to do the exterior, sheer. (Only weekends, unfortunately)
     
  12. cookie munster
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    cookie munster Junior Member

    Ah, that explains it :)

    Is there any rule of thumb for determining the weight for the outer tabbing at all? I have to do a somewhat similar join for a 27"sailboat, but don't have a clue how heavy it should be....
     
  13. Roly
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    Roly Senior Member

    My rule of thumb (gleened from multiple sources)- must be as strong as the laminates it is bridging with a 100mm
    overlap,layers edges staggered ; The substrate well abraided with 36 grit.
    Actually, we used 2x weight of laminate internally and 4x weight externally for
    extra strength to an expose part of the boat. (Sheer)
    Composite engineer specified 2X.
    Double bias all round. The off axis loading of the db is an unknown variable,but it goes on so well. (An it is commonly used for this purpose.)
     
  14. tunnels

    tunnels Previous Member

    Double bias is the best choice by far to do any types of joins with as 100% of the glass is working for you not 50% like when you use a 0-90 type of glass , The plus also is that the strands are longer and get a better hold of the epoxy and longer strands will streach more in exstreme conditions and not break as easly !!. All that make sense ??:D
    Its a good place to use peel ply when you put your glass on and roll the glass and peel ply out at the same time!.
    When the resin is hard the peel ply comes off and leaves you with a beautiful ,completely smooth, nice to work with ,100% uncomtaminated surface to Fair and fill and sand . Worth thinking about in the future !!
     

  15. cookie munster
    Joined: Jan 2010
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    cookie munster Junior Member

    Thanks Roly, appreciated
     
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