steel reinforced fiberglass?

Discussion in 'Boat Design' started by Akamuana, Dec 29, 2022.

  1. Akamuana
    Joined: Dec 2022
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    Location: West Coast USA

    Akamuana New Member

    I'm crossposting this from another forum to see if I can find anyone who has actually dealt with this construction technique, or even seen it / heard of it:

    "Looking at a boat built on the lines of Atkins Thistle - similar to the Kendall 32 (and later Westsail 32), but built independently by the owner in 1980. There are a few areas of concern but the one that I'd never heard of is steel reinforcement in the FG layup. According to the seller, who is the second owner and a personal friend of the builder, it was done like a ferrocement build would be done, but using 12 layers of glass layup instead of concrete (both bar and tied wire mesh). Without knowing more, it strikes me as a corrosion nightmare waiting to happen; that said, if all's well after 42 years maybe she'll continue to be sound. Anybody here ever dealt with this?"
  2. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    I think your instincts are correct.It may well be sound but it will be very heavy and if there is an opportunity for moisture to get in there-it will.Why looking at the boat?It would be a bold man who actually bought such a boat when there are literally thousands of other more conventional boats on the market at any time.It might also be a nightmare to sell on eventually due to the unconventional construction.
  3. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    Concrete has very good mechanical properties when working in compression but very low when working in tension. For this reason, metal rods are added, forming the so-called "ferrocement", which greatly improve the tensile properties of the assembly. That is not, at all, the problem of the FG. What could be, therefore, the justification for having to reinforce it with steel?
    philSweet and baeckmo like this.
  4. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    A picture is worth a thousand words, so take some (exterior and interior) or even better find some from the build. Your description is really poor, because "like ferrocement but without concrete, wire mesh and bar" doesn't actually tell us where the "steel reinforcement" is, if indeed there is any.

    To me your description sounds like a monolithic fiberglass build, the meaning of "like a ferrocement build" beeing that it was done on a male plug and not in a female mold. It's even possible that you are dealing with a C-flex build, and people just didn't know the correct terms to describe it.
    12 layers of fiberglass could be a substantial skin thickness, depending on the used glass weight, so any steel could be redundant.

    Anyway, if there is any steel remaining in the structure and corroding, it would be really obvious since rust expands and bleeds. The only exception would be pipe framing, wich can corrode from the inside. Even that could be just cosmetic, depending on how much glass they laid over the pipe. To find sound encapsulated steel, a magnet is all you need.

    More advice is only possible if we know more about the actual build, and that info is easy to obtain with a visual inspection and a magnet.
  5. skaraborgcraft
    Joined: Dec 2020
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    Location: sweden

    skaraborgcraft Senior Member

    I saw a boat built in Australia, what looked like ferro principle, started with rod frames covered in mesh. It was then spray foamed, then glassed inside and out. Apparently been in use for over a decade without issues and unsinkable in theory.

    Hard to make any kind of judgements without seeing pictures.
    KD8NPB likes this.

  6. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    I have used an Embeco grout to bed heavy machinery, very high compressive strength, perhaps this is what the op is looking at?
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