Tips on Dagger Board Trunk Construction?

Discussion in 'Boatbuilding' started by CatBuilder, Dec 21, 2011.

  1. hoytedow
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    hoytedow Wood Butcher

    That is a very good question.
    Take a piece of high density styro-foam and test it under vacuum and find out.
     
  2. hoytedow
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    hoytedow Wood Butcher

  3. CatBuilder

    CatBuilder Previous Member

    There's got to be something at Home Depot that could stand up to vacuum, but then dissolve. Anyone know something that would work?

    Or, failing that, I can just do it in halves, then join... only problem is, I don't know how to join the halves properly. :(
     
  4. hoytedow
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    hoytedow Wood Butcher

  5. CatBuilder

    CatBuilder Previous Member

    (checking on closed cell foam supplier)

    Or, another thought too:

    What about using foam or pretty much anything as a spacer and laying up *just the inner skins* by hand, doing them as halves of the total clamshell?

    Then, I could join those inner skins to each other, sand them and hang the cores and everything else on them and infuse the whole shot.
     
  6. hoytedow
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    hoytedow Wood Butcher

  7. hoytedow
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    hoytedow Wood Butcher

    If you used thinner eps for spacer, you would need far less acetone to remove the form, and shrinkage under pressure would probably not be much of a factor.
     
  8. Yobarnacle
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    Yobarnacle Senior Member

    Vacumn is only one atmosphere pressure. Used to write greetings with marks-alot on 16 oz styrofoam cups. Put them in the collection basket on RSV diving to 2000ft. Get back thimble sized cups with tiny,tiny, legible writing. Sent to family and friends as souvenirs. One atmosphere isn't 2000 ft deep sea pressure.
     
  9. CatBuilder

    CatBuilder Previous Member

    Right, but I need 1/2" spacing.

    The vacuum is 14.2 PSI. Doesn't sound like much, until you imagine taking a piece of foam and putting a small, 1" x 1" stand at the bottom of a 14lbs weight and set it on the foam. It'll compact, I think.

    Either way, I can avoid all of the molding/sticking problems if I do the following:

    1) Put some flexible, soft foam on the board, wrapping it (1/2")
    2) Put some plastic over that
    3) Laminate the inner skins by hand, in half shells
    4) Join the half shells and sand the outside of the new case
    5) Put my foam and glass into place, stapling if necessary
    6) Put outer glass into place stapling
    7) Infusion materials
    8) Infuse, using the inner skin as the back of the vacuum bag

    That's one way.
     
  10. rberrey
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    rberrey Senior Member

    Cat , foam backer rod comes in whatever size you want. It can come in rolls depending on the stiffness. It is a long roll of foam that will take the place of the rope. Another option would be the foam you put under wood flooring, you may have to wrap it two or three times to get your 1/2". Rick
     
  11. hoytedow
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    hoytedow Wood Butcher

    It would have to be a foam easily dissolved. Not all foam is.
     
  12. Yobarnacle
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    Yobarnacle Senior Member

    include primercord in the sacrificial foam....and sacrifice it when time comes. :)
     
  13. hoytedow
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    hoytedow Wood Butcher

    That would be a blast!
     
  14. AndrewK
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    AndrewK Senior Member

    CatBuilder; no I did not miss understand the crush foam. My suggestion just requires the aft D section to be added later when you glass the trailing edge.

    What kind of perforated foam do you have, is it meant for infusion or bagging only?
    Bagging only perforations are large and only spaced at 50mm, you want many small holes commonly at 20mm spacing.

    My suggested spacing material is what is commonly done here as they all work and are cheap if not free. Carpet and lino comes free from the layers as they have to pay to dispose of the offcuts. Plastic or cardboard sign boards are cheap from local hardware depot or packaging material store. I will try and find a photo of the texture the carpet back leaves on the laminate if you like.
    1/2" clearance all around makes very sloppy and noisy boards.
    What I described allows for the glass that comes in over the deck into the case and from the hull bottom into the case and you end up with no high spots inside the case at all. The board will be fully supported as the case is smooth and foil shaped. This is why you only need 6mm around the board.
     

  15. CatBuilder

    CatBuilder Previous Member

    Thanks, Andrew.

    I understand what you are saying now. Leave the D until later. How would I join the D section with the already finished product? I am not clear on how to do a taper in that. Do I just grind the D down or make the D with a taper on each end, then use the taper in the foam/glass flat panel and join them up like a patch?

    You did miss something that rberry posted from his designer.

    1/2" (12mm) is the size of the trunk gap, but you use bog on the exits of the trunk to make a tight fit after the boards are installed. This provides a nice, neat, easily controlled surface and mating to the existing hull.

    The middle of the trunk makes no difference at all, so 1/2" up there is no big deal. Loads on a board are at the keel (hull) and deck level.
     
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