Deck beam delamination and forces

Discussion in 'Sailboats' started by jmwoodring, Apr 21, 2012.

  1. jmwoodring
    Joined: Apr 2012
    Posts: 17
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Texas

    jmwoodring Junior Member

    Hi everyone
    I'm new here and not sure if this is the correct sub-category, but here goes:

    I'm looking at buying a flush decked,FRP sailboat, which was owner finished from a hull kit. The craftsmanship seems to be high, but nonetheless, I suspect a mistake was made in the design or implementation of the deck. Namely, the laminated beams supporting the deck (5-6 in the forward half of the boat) have begun to open up and split. Perhaps there aren't enough compression posts, bad glue was used, or the scantlings are too small overall.

    This is the boat:

    [​IMG]

    And here is the deck stepped mast:

    [​IMG]

    Here is a shot of the interior:

    [​IMG]

    And here is an example of the delamination:

    [​IMG]

    Now, all of the beams are delaminating on the bottom strip only. Also, it seems to be localized in the center of the beam, mostly. The mast is deck-stepped and there seems to be a full bulkhead support directly underneath it. Also, I saw no evidence of crushing, but was not able to inspect it for long.

    So, what is likely causing this issue? Downward pressure? Lateral pressure from the rig? Bad glue?

    How would you fix the problem? More beams? Make the current ones stronger? Laminate on top of? Thru-bolts?

    I'd appreciate your advice. Thanks.

    James
     
  2. mydauphin
    Joined: Apr 2007
    Posts: 2,164
    Likes: 52, Points: 48, Legacy Rep: 575
    Location: Florida

    mydauphin Senior Member

    What lumber did they use on beams and boat in general, and how did they glue them together?
     
  3. jmwoodring
    Joined: Apr 2012
    Posts: 17
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Texas

    jmwoodring Junior Member

    Might be some kind of mahogany, but no clue really. They're on 18" centers, I believe.
     
  4. mydauphin
    Joined: Apr 2007
    Posts: 2,164
    Likes: 52, Points: 48, Legacy Rep: 575
    Location: Florida

    mydauphin Senior Member

    Before you buy boat, get it survey by someone that knows wood and make sure they followed plans and used proper materials. If they used the wrong materials or glues the whole thing can fall apart on you.
     
  5. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    It looks to be starved glue joints, something defective from the start. If only the bottom strip is seperating, it's doubtful you've got a serious issue. Especially if nothing has happened as a result of the seperations. It would be a good idea to inject epoxy into the crevices to prevent any further cracking and to strengthen the area a bit.
     
  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 474, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Agreed, it's probably part of the lamination process. The inside of the curve portion of a bent laminate receives the most pressure during the assembly. If you're not careful you can starve the joint in this area.

    It's likely you could wedge open the seam, inject some epoxy and brace it closed as the goo cures.
     
  7. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    If a sawzall blade could be slipped into a crack, it would be far better to saw the crack out to the width of the blade, which would roughen the adjacent glue surfaces and also allow epoxy to be injected more effectively. Often you can "kneel" the sawzall in order to start a cut where you can't insert the blade fully yet.
     

  8. jmwoodring
    Joined: Apr 2012
    Posts: 17
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Texas

    jmwoodring Junior Member

    Thanks for your advice. Let the negotiations begin!
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.