Best Steel for Hulls and Structure

Discussion in 'Boat Design' started by Bahama, Jun 24, 2010.

  1. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    I've not seen any discussion on the better steel choices that are available to a boat builder for the hull and structure. Are there any alloys with some small amounts of nickel or copper that are not cost prohibitive?

    I was reading here and was intrigued that just 3.75% gave some very nice corrosion resistance. And it surprised me that 0.635% seemed like it just the right amount of copper because going higher didn't improve things and actually made it slightly worse for the "Continuously wet with seawater" category.

    Anyway, I was just curious what are the better properties and percentages to look for in steel. I was reading about A242, which seemed very interesting, but I don't know the cost of it and it it's any good for a ship hull. A440 and A441 also seemed interesting. A373 and A36 looked nice, but not as good as the others.

    I'm also interesting in knowing if you need any repairs, how readily you can find the steel in question--I don't want some exotic product, but I do want to learn if there is something offered that is readily available and is affordable and does offer some added protection against corrosion.

    Thanks for any posts, I think this would be interesting information to know.
  2. apex1

    apex1 Guest

    Common is the Grade A shipbuilding steel, better a HT steel like GL A 36 (HT stands for high tensile).

    Corrosion resistance is not the important factor, but strength! every steel will corrode in seawater when not protected, even SS.

    For a boat of your size, common AH32 is sufficient, don´t worry. And it can be replaced in case of trouble in every port and every other anchorage around the world.

    If corrosion is bothering you, build in Monel, that will never corrode and you can skimp on antifouling. But beware! The hull and deck will cost you the same amount as a yard built, complete boat in aluminium.

  3. M&M Ovenden
    Joined: Jan 2006
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    M&M Ovenden Senior Member

    A36 will be the most readily available steel in the states or you could get 44W from Canada with upgraded properties :) .
  4. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    When I saw your corrision note it reminded me of this steel that I read about with 36% nickel that is rust free and antifouling, but they said that it cost a fortune... you don't paint it below the water line, but you would want to above for temperature control. I couldn't remember the name of it, and I looked up what your Monel reference was--and there it was. That was the steel!

    Thanks for all the info, especially AH32 and GL-A 36.

    It looks like the AH32 has a Tensile Strength of 440-590 and AH36 is just a bit more at 490-620.
  5. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    thanks for the info. What is predominant in UK/Europe?
  6. jg451
    Joined: Jul 2010
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    jg451 Junior Member

    Back in the early 60's the Johnsons, contributors to Nat Geo. built their new boat it was constructed of COR10 steel (old spec A242 cortenA now A588 cortenB). It is a paintable steel that is meant to rust if exposed, the rust not flaking but forming a protective coating to the surface. Neat stuff. Cost obviously varies where you are on the world. It is not cheap. It is however a viable alternative.

  7. Gypsie
    Joined: Apr 2005
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    Gypsie Randall Future by Design

    I have a 40ft yacht built from Cor10 steel launched in '78, not only is the steel extremely resistant to decaying rust but absolutely bullet proof (handy when striking coral knobs at 6 knots). If you can build your hull with Cor10 (commonly known as "Weathering Steel") then go for it.

  8. apex1

    apex1 Guest

    Cor ten is really a good material...........

    ...have a replating of a 10 cm² in a underwater area........... Or, no, skimp on it, you have just 2000 miles to go to the place where they have it...........

    Docksitters don´t need any reliable material (Grp crap is ok, or better than that), passage makers need the very sophisticated stuff! Plain metal, bare wood, or the like.
    Corten sounds good, Monel is better, Titanium is perfect.

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