Stringer Replacement with Composit Materal -

Discussion in 'Materials' started by kkresge, May 14, 2015.

  1. kkresge
    Joined: May 2015
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    Location: NE PA

    kkresge New Member

    I am new to this forum and to boat restoration, I have a little knowledge which can be dangerous.

    I have been looking for information on using an alternative material for replacing the stringers in my 1968 Caravell boat, after removing the carpet and decking I found that all the stringers have rotted out and now require to be replaced.

    :?: My question is can a composite decking be used in replacing the stringers in a boat. This decking I am referring to is what is available at local home improvement stores and used for decking on home decks.

    My plan is to use expanding foam to fill the voids in the hull between stringers, the old foam sheets were water logged when I removed them. I would expect this would limit the exposure of the stringers to water.

    :?: Further question if this material can be used is if it needs to be sealed in the same manner other material is sealed with epoxy or resin?
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Composite decking is a poor choice. The adhesion of the resin will be bad, it is heavy and it is too flexible. The original were plywood or pine and lasted for decades.
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    There are a few different types of composite decking and all are unsuitable, simply because they're not structural elements. Some are lighter than wood, but all suck as stringers, beams, etc.

    Foam filling around wooden elements tends to promote mold and rot issues, not decrease them.

    Wood is used because it's relatively cheap, especially compared to made made products, it's easy to work and mill and with encapsulation can last decades. Even without epoxy coatings, it can last a few decades.

    Budget wise, it's very difficult to find something better than wood. This said, there are alternatives, such as Cossa board and other materials. They'll cost more, but many aren't subject to the issues wood can have, locked up in a boat's bilge.

    So, figure out what your goals are, which will likely make the material choices quite limited.

  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    As mentioned, there are many options on a core for stringers, all have their pros and cons, so knowing your plan for the boat and expectations helps.

    Plywood is readilly available, low in cost, easy to work with and strong, but may eventually rot. The time frame for the potential rot depends more on your level of attention to detail than anything else.

    You can also make hollow stringers, you just need to make the laminate thicker so it can take the entire load. If you use wood, then make a thicker laminate it won't matter if the woods rots or not. It also significantly reduces the chances of the wood rotting because there is less of a chance that water will ever reach the wood.

    The main cause of rotten stringers is sloppy workmanship and too thin of a laminate covering the stringer, unsealed screw holes should be a close second.
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