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Thread: Metal gusset material

  1. #1
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    Default Metal gusset material

    Small galvanized gusset plates on my family's dory have finally rusted through after fifty years. They're about 4" long, diamond shaped, and made of much thicker material than, say, Simpson/Strong-Tie uses. The dory is used mostly on freshwater these days but is pretty well suffused with salt after all these years and is stored near saltwater. What are my options for replacement? Here's how I see it:

    Galvanized: I'm not that convinced by modern galvanization, plus unless they could be found in this small weird shape they'd have to be cut, and would start rusting immediately.

    Aluminum: easy to shape and drill, but my experience has been that some aluminum corrodes faster than others in the saltwater environment, and I don't know what to ask for.

    Stainless: perfect, if it could be ordered custom cut and drilled. I'm not set up to work this stuff.

    Brass/bronze: is is tough enough to be structural, and can I get thick sheet?

    What say you?

  2. #2
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    Default Re: Metal gusset material

    Advice in big red writing
    Quote Originally Posted by katey View Post
    Small galvanized gusset plates on my family's dory have finally rusted through after fifty years. They're about 4" long, diamond shaped, and made of much thicker material than, say, Simpson/Strong-Tie uses. The dory is used mostly on freshwater these days but is pretty well suffused with salt after all these years and is stored near saltwater. What are my options for replacement? Here's how I see it:

    Galvanized: I'm not that convinced by modern galvanization, plus unless they could be found in this small weird shape they'd have to be cut, and would start rusting immediately. Make them out of mild steel of the correct thickness and send them to a galvo tank to be dipped. Ask your local fab shop to put them in with one of their batches.

    Aluminum: easy to shape and drill, but my experience has been that some aluminum corrodes faster than others in the saltwater environment, and I don't know what to ask for. Don't go there.

    Stainless: perfect, if it could be ordered custom cut and drilled. I'm not set up to work this stuff. OK or find a local fab shop, could be pricy.

    Brass/bronze: is is tough enough to be structural, and can I get thick sheet? Yes for bronze, and Yes,

    What say you?
    Or you could glue on wooden gussets.
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
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    Default Re: Metal gusset material

    What, Nick said. Heck, I'd even use mild steel and put cold galvanizing on them. That stuff works pretty well when applied copiously.


    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  4. #4
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    Default Re: Metal gusset material

    We're talking about rural midcoast Maine. "Local" fab shop is likely to be Boston, a four hour drive away. Will look into bronze. Cold galv lasts about two years this close to salt water. Thanks!

  5. #5
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    Default Re: Metal gusset material

    Quote Originally Posted by katey View Post
    We're talking about rural midcoast Maine. "Local" fab shop is likely to be Boston, a four hour drive away. Will look into bronze. Cold galv lasts about two years this close to salt water. Thanks!
    Really? I would think there must be any number of shops serving the lobster boats in the area. Ellsworth/Southwest Harbor/Trenton maybe? I'll bet Ryan at Ocean House in Manset would be able to steer you in the right direction. And something like few gussets for a dory should be $100 and a six pack, plus materials costs. Bronze flat stock is readily available and easily worked - I'd go with Nick's advice there. Not cheap but you will never have to do it again.
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  6. #6
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    Default Re: Metal gusset material

    G-10 is a glass-epoxy laminate available in sheets from McMaster-Carr. It's strong, doesn't corrode can be worked with common tools and bonds well using epoxy. I'd call it a toss-up vs. 1/8" bronze plate, but it's easier to buy.

  7. #7
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    Default Re: Metal gusset material

    Aluminium alloy 5083 (for plate) or 6082 (for extrusions, like flat bar) don't corrode in a marine environment. Use austenitic stainless steel 316 fastenings 304 if you can't get 316.

    Rockport Steel (Rockport, ME) are great they will supply you with small quantities of material - or fabricate it for you. They should have 6082 flat bar, which you can cut to shape.

    Cheers -- George
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  8. #8
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    Default Re: Metal gusset material

    +1 for G-10/FR4. FR4 is flame retardant G-10 and may be easier to get. Aside from the color, that are essentially the same.

    Aluminum: 5052-H32 or H34. It is not as stiff as steel, but you can go a little thicker.
    Alternatives
    6061-T6 (T651 is same if over 1/4 inch) 6063 is OK too.
    5083, 5086 and 5456 H321 or H116 Marine grade only (ASTM B928)
    Stay away from any 2000 or 7000 series alloy.

    EDIT George is right, 6082 is good too.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  9. #9
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    Default Re: Metal gusset material

    Cold galv lasts about two years this close to salt water.
    I live 300 feet from saltwater and have several cold galvanized projects that have been going strong for over 10 years.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  10. #10
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    Default Re: Metal gusset material

    My home is thirty feet from salt water. My neighbor has a steel framed two story house that is over forty years old! The frame was sprayed with cold galvanize when it was first built. No rust as yet!
    Jay

  11. #11
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    Default Re: Metal gusset material

    The nearest "Hot Dip" from mid- coast Maine is basically Boston. The Maine locals seem to really shy away from it, but I just sent a centerboard down there from Searsport. ( A friend drove it down there) They did a fine job. Note that "hot dip" has a minimum charge and it is usually pretty steep. I wait until we have accumulated a good pile of stuff. Anchors, chain, garden gates, plant-stands or whatever. (We send out welded up ADA handrails and railings to be dipped fairly often so I usually include my stuff in that)

    However, if these are what I think they are and it was mine I would make them from bronze, copper or even brass plate. In fresh water brass would be fine. Cut them out on a band saw, and if they are clips, bend them in my little hydraulic press brake, or in a good vise with a hammer. If they are just flat it is a piece of cake.
    (I do this sort of thing all the time. If you have a drawing(s) or paper templates you can send them out to be made of any material you want. It doesn't matter if it is Boston or San Francisco to UPS!)

  12. #12
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    Default

    Rockport Steel is close! Will look into it.

  13. #13
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    Default Re: Metal gusset material

    What Bruce said, if you have a bandsaw you can cut brass and copper sheet on it. The finer the blade (smaller teeth) the better.
    '' You ain't gonna learn what you don't want to know. ''
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