Hull Inspection during construction

Discussion in 'Fiberglass and Composite Boat Building' started by myastral, Jun 9, 2006.

  1. myastral
    Joined: May 2006
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    Location: Taiwan

    myastral Pan Asian Yacht Service

    Has anyone found a good way to check for core adhesion during construction ?? Im going to look at a 120 that is getting cored and they would like an inspection before they start to do the glass work anyone have a good systen for checking ??
     
  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    It's not unheard of to use ultrasound equipment for this, but it takes a very skilled technician and a good machine for it to work. What core material is being used? Something like Nomex will probably be a lot harder to inspect than foam or balsa.
     
  3. Karsten
    Joined: Jun 2004
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    Location: Sydney

    Karsten Senior Member

    I'm guessing that one skin is laminated and the core is bonded to that skin. They would like you to check if the core bond is o.k. before laminating the second skin.

    If this is the case they should have used perforated foam or foam with intersecting cuts in both surfaces. You can tell if the bond is o.k. by looking at the perforation holes. The core bonding glue should have been squeezed through these holes. If not it is likely that there are air pockets between the first skin and the core. You can tell by rubbing your hand across the area. It will sound differently if there is no bond.

    If the hull is out of the mould the best way to check for delamination is to go to a newsagent and buy yourself a pen. Use the change to tap against the laminate with the edge of a coin and use the pen to mark areas that sound dull. The dull sounding areas have delamination.

    Ulatrasound is useless for this. With ultrasound you can find delamination between plies or other foreign bodies like knife blades or gloves in the laminate because the ultrasound will be reflected by these objects and the equipment will detect a different skin thickness because of this. It's not going to pick up delamination to the foam because most of the ultrasound will be reflected at the boundary between laminate and foam no matter if there is a bond or not.

    Hope this helps.

    Cheers,
    Karsten
     
  4. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    I've seen thermal imaging used to find fractured core due to impact. I don't know if this would work for core adhesion. You might want to look into it.
     
  5. Buckle
    Joined: May 2004
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    Location: Plymouth, UK

    Buckle Composite Engineer

    Perhaps you may wish to consider vacuum bagging your core to the hull. Adhesive bleed, through the core should be highly visible and would solve this difficult inspection task.

    Having confindence in your process is a good start.
     
  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    They make equipment to check for adhesion. You need to get samples of the laminate. They measure the amount of tension necessary to pull them apart. You can use cut-outs from through-hull fittings, exhausts, etc.
     

  7. BondMaster
    Joined: Jun 2006
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    Location: Houston

    BondMaster New Member

    Delamination Testing

    Our company develops equipment that finds delaminations/disbonds in composite materials and some metals. The equipment would not be cost effective for a boat owner but, it would be for someone in the boat business. If you would like more information on this please get in touch with me. We only manufacture, sell, and train on the equipment. We do not do inspection work.
     
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