Transom Core Alternatives

Discussion in 'Fiberglass and Composite Boat Building' started by tomherrick, Apr 3, 2008.

  1. tomherrick
    Joined: Sep 2006
    Posts: 90
    Likes: 1, Points: 18, Legacy Rep: 14
    Location: Versailles, Kentucky

    tomherrick Junior Member

    I've got an '84 C-Dory with a rotten transom core. I'll finish removing the last of the original balsa core tomorrow. I'm considering alternative core lumber and methodology for layup. Foams and balsa are not in the plan due to expense and balsa seems like an accident waiting to happen; great when all's well, but quickly unserviceable with any water migration. But, the designer certainly had in mind keeping the transom light and I'll try to keep it in line with that concept.

    I've looked at true marine plywood, but it's not available in my area and shipping for a couple of these high-priced panels is beyond budget. It's also pretty heavy in a Doug Fir.

    I've been considering creating my own 'plywood' core with lumber I have available in the shop. Of all the species I have available, the old-growth redwood seems to be one to fit the bill. It's lightweight and very rot resistant (unlike the stuff being harvested today), but it's not particular strong; kinda splintery. But, I've been thinking of resawing it to one-eighth inch stock for an alternating orientation epoxy layup. I've got to build up to an inch and a half, or about 12 laminations. Seems that with the pieces being custom fit with no voids before lamination, and each layer being laid up at 90-degrees to the next in epoxy, that I'd have a pretty tough transom. But, I'm a cabinetmaker and house restoration guy, not a boat builder.

    Does my approach using pretty close grained old-growth (harvested 40-50 years ago) redwood and an epoxy lamination sound reasonable to folks here?


    Tom Herrick
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Plywood will be as cheap a core material as you can get. Sea Cast (a polyurethane resin mixed willed milled up cured polyester) is an option, but probably more costly and certainly much heavier then foam or balsa.

    Have you considered pour in polyurethane foam, rather then sheet goods? It's cheaper, form fitting and will stick to the inner and outer 'glass skins well (if clean). Look into the 8 pound stuff from which will save the bother of cutting up plywood.

    The brittle redwood doesn't sound particularly appealing. I'm picturing the laminate filled with separated bits of fractured redwood in a few years.
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