composite panel engineering question

Discussion in 'Boatbuilding' started by Charly, Mar 30, 2015.

  1. Charly
    Joined: Dec 2009
    Posts: 429
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    Location: st simons island ga

    Charly Senior Member

    my intention is to install a removeable water tight bulkhead, amidships,in each hull of a 36 catamaran.

    I would like to use some two inch thick dow corning insulation "pink board" as core, since I already have it, and some 20 oz triax fabric on each side, epoxied on, as the skins. It will cover a hole about three feet wide by about three feet high, with cedar or spruce stiffeners on one side to accept thru bolts so I can fix it to the existing bulkead flange, which will have a gasket.

    What I don't have a clue about is how much hydro pressure or air pressure could develop in a catastrophe, and how do you figure out how many layers of 20 oz glass would be needed? Would one layer each side be strong enough?
  2. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    It will not be easy to get that patch resulting watertight. Could you show a picture of what you want to do ?. Moreover, the resistance should have the bulkhead itself depends on the design pressure to be applied. It would be necessary to have more details on the bulkhead, location, height, distance to main deck, etc. In general, it is not advisable to make holes in the bulkhead. Try to avoid it.
  3. Charlyipad
    Joined: May 2014
    Posts: 227
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    Location: St Simons is ga

    Charlyipad Senior Member

    This shot was taken during the build before the hull stringers were added.

    I don't have the exact dimensions but you get the idea. No perforations in the existing bulkhead flange, only in the insert. The insert would overlap on the outside of the bulkhead flange, and have thru bolts that would connect to "stringers" behind it, that would overlap the flange on the back side, so when you tighten down on the bolts they would compress a gasket at the flange. The thru bolts would be set in oversized holes filled with structural bog for a snug, threaded fit. a dab of caulk should seal it all up. Also i want to have an 8" inspection port in the middle so I can open it up when needed for airflow to ventilate the whole hull.These bulkhead inserts would be semi permanent- rarely removed.

    Any ideas or critique appreciated.
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