What joint to use in bulkheads??

Discussion in 'Boatbuilding' started by CatBuilder, Jun 3, 2011.

  1. CatBuilder

    CatBuilder Previous Member

    I have a few bulkheads cut out now that are larger than one single sheet of plywood in width. So, I need to join the pieces to make one large bulkhead.

    My designer suggests, for the regular, non-beam bulkheads, that you can, "join together at the bilge and sheers with gussets" to make bulkheads out of scraps of bulkhead ply you have hanging around.

    My joints are about 2/3 of the way across the bulkhead. They are perfect vertical lines.

    Do I butt them and gusset them? If so, what kind of gusset is my designer talking about?

    Is there a way to do a quick butt and tape?

    Or... am I stuck doing the dreaded (because it takes so much time) scarf?

    Thoughts?
     
  2. Charly
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    Charly Senior Member

    hey Cat, is it too late in the game to bag and laminate some up? Are you using fir or okume? Do you have any of the 3 mm stuff left over?
     
  3. hoytedow
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    hoytedow Wood Butcher

    Take a router and make a rabbet on each vertical edge then glue a batten to join them.

    Drawing is obviously not scaled in any way.
     

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  4. CatBuilder

    CatBuilder Previous Member

    I should have mentioned they are solid ply. 12mm.

    Checking out rabbet joint.
     
  5. hoytedow
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    hoytedow Wood Butcher

    Plywood rabbets well. Epoxy is the glue of choice. Batten can be made from 6mm ply if it needs to be flush or 12mm if raised surface is acceptable.
     
  6. rasorinc
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    rasorinc Senior Member

    What about a butt joint plus 2-3 layers of 12 oz Bi/AX tape 8" wide both sides. I like Hoyts idea but would use tape also. Using both should make the joint extremly stiff and very difficult to seperate.
     
  7. CatBuilder

    CatBuilder Previous Member

    Sounds good to me. Wish I had some thin ply for flush joint. Mabye I can just grind the proud part away?
     
  8. hoytedow
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    hoytedow Wood Butcher

    Maybe chamfer the raised edge?
     

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  9. rasorinc
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    rasorinc Senior Member

    You don't have to use ply--go buy a piece of hardwood and rip it down to 1/4" or 5/16s"
    epoxy it in and use the Bi/ax and your good to go. If no hardwood avaiable use dry yellow pine. Get the dense stuff, machine graded, any truss company has it and most lumber co. carry it. Heavy stuff compared the regular yellow pine. Loes does not carry it or Home depot. strong..............2x6x10' about $$5.00.
    Also you can rip down your 3/4 ply strips to 1/4 or whatever you want. Stan
     
  10. hoytedow
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    hoytedow Wood Butcher

    They both have syp in pressure treated. Your wood stool is syp, pressure treated, of course. ;)

    Hardwood, not oak, would be better. Ash would be the best if you can find it, or hickory, though hickory may be too hard and difficult to work with. Poplar is readily available but I don't know about its properties in a marine environment. Probably fine if well sealed with epoxy.
     
  11. sabahcat
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    sabahcat Senior Member

    Whats so hard about doing an 10:1 scarf?

    Go hard with a powerplaner and finish it up with a two speed sander, soft pad and stick on or velcro with 36 grit

    I always scarf two full sheets and then cut the full sized bh from that
     
  12. hoytedow
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    hoytedow Wood Butcher

    Scarfing the oversize blank is a good idea. Then you can temporarily rejoin them before cutting the outside dimensions. Then they will be easy to fit together.
    For someone who has little scarfing experience, the rabbet is the easiest way to go.
     
  13. sabahcat
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    sabahcat Senior Member

    Funnily enough, for someone who has zero rabbet experience it looks to be a PITA compared to a scarf ;)
     
  14. rasorinc
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    rasorinc Senior Member

    Hoyt, I think poplar rots if you look at it the wrong way. 3 coats of epoxy on an interior piece should be good protection but it is not a strong wood.
     

  15. hoytedow
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    hoytedow Wood Butcher

    Then I would go with ash or, if not available, p.t. yellow pine, with lots of epoxy.
    I think ripping 12mm into 6mm would be a PITA. I could be wrong. Have been before.
     
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