Distorted deck plating

Discussion in 'Metal Boat Building' started by spaceboy, Aug 28, 2018.

  1. spaceboy
    Joined: May 2013
    Posts: 25
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: nw uk

    spaceboy Junior Member

    Mike, cutting and welding is the way to go for me. The boat is an Alan Buchanan design, built to Lloyds certification. The original owner spent a small fortune on Lloyds surveyors. No part of the build or machinery installation was done without approval. I think the yard went bust before the deck could be rectified. I have the sheets with weights and hydrostatics, understanding them is a work in progress, a bit of light reading at bedtime.
    Sam, most of the deck is as in the pic', the afterdeck is the most pronounced. Flame straightening would be the best option, but as Tansl indicated, finding someone with the gear, knowledge and skill might not be easy, even though I live near to Cammell Lairds.
     
  2. JamesG123
    Joined: Mar 2015
    Posts: 654
    Likes: 75, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    Won't be easy nor cheap because time = money, and flame straightening is a time intensive process. Its literally someone sitting there with a blowtorch and a bucket of water trying to coax steel molecule crystals into lining up the way they want. Your best bet is cutting off the worst of the bad plate and welding in new sheet metal. Esp. if you are handy with a grinder and welder yourself.
     
    Last edited: Sep 2, 2018
  3. TANSL
    Joined: Sep 2011
    Posts: 6,726
    Likes: 491, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    It will not be easy to join a flat iron with another that is deformed, even slightly, and the contribution of heat from so much welding can make the situation even worse.
    I'd recommend using the heat to straighten the existing and, if nothing is achieved, change the entire surface undulated by new plate.
     
  4. JamesG123
    Joined: Mar 2015
    Posts: 654
    Likes: 75, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    Not if proper steel fabrication methods are employed. The deformed frame will be stable when the bad sections are removed, taking the stress out of the structure. He can then put in a new section that is the proper size
     
  5. TANSL
    Joined: Sep 2011
    Posts: 6,726
    Likes: 491, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I have assumed that the frames were in good condition and that the only deformed is the plate. If the frames are also deformed, the heat will be much less effective since giving them the correct shape will be very difficult. If the frames are deformed, the best thing is, using "proper steel fabrication methods" (that is always necessary), to change everything.
     
  6. JamesG123
    Joined: Mar 2015
    Posts: 654
    Likes: 75, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    Assuming that the deck plates were flat when they were welded down, and the buckling was caused by thermal expansion of the plates between frames, its unlikely that it is perfectly uniform and so there will be stresses exerted on the frames out to the gunwales, either tension or compression, but probably compression. So when he cuts the deck, it will probably pop one way or anther as the stress is released.

    In I think the second pic from underneath you can see that a roof beam is bowed and twisted. Might just be sloppy original fitting, but it could where the deck plate stresses have concentrated and warped the beam.
     
  7. Barry
    Joined: Mar 2002
    Posts: 1,447
    Likes: 243, Points: 63, Legacy Rep: 158

    Barry Senior Member


    "so as not to burn the material that would become brittle"
    Where do you come up with this idea??
     
  8. TANSL
    Joined: Sep 2011
    Posts: 6,726
    Likes: 491, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Wherever I come from, which does not matter in this case, it is not an "idea" but the experience of many years working in the workshops of large shipyards.
    Anyway, so as not to be discourteous to you, if you still want to know where I'm coming from, I could explain it to you through private mail so as not to bore the public with things that very few people can be interested in.
     
  9. baeckmo
    Joined: Jun 2009
    Posts: 1,292
    Likes: 259, Points: 83, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    Dear TANSL, Barry's question is not about your personal origin; I think we have a semantic salto mortale here (or too much ego....?). But you are claiming that there is a risk for material brittleness in connection with flame straightening. This is contrary to my experience, and I think also to Barry's dito. So his question (and mine as well) is where this statement comes from; simply can you refer to some kind of validation.
     
  10. TANSL
    Joined: Sep 2011
    Posts: 6,726
    Likes: 491, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Dear @baeckmo, I assure you that I understood perfectly what Barry meant and, simply, I wanted to answer him with a little irony. I'm sorry if it has not been understood like that.
    As I say, after using that method for many years in various Spanish shipyards, I have seen plates burned by an abusive application of that method. The heat/fire, burns the carbon of the plates and they can become brittle. That is the best method that I know to solve the problem posed by the OP but, like any other solution, it is preferable that it is applied by a professional who knows the system. That is my experience, not "an idea", wherever I come from.
    Answering your question : I do not have any kind of validation, whatever you want to say with that, I only speak of my experience.
    Cheers.
     
  11. JamesG123
    Joined: Mar 2015
    Posts: 654
    Likes: 75, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    TANSL is correct here if not semantically precise (¿Cómo es tu español Barry?). It is very easy to negatively effect the temper and corrosion resistance of a steel with the over enthusiastic application of heat.
     
    fallguy and TANSL like this.
  12. Barry
    Joined: Mar 2002
    Posts: 1,447
    Likes: 243, Points: 63, Legacy Rep: 158

    Barry Senior Member

    The question to Tansl is perfectly valid when he says that an application of heat, which you support, will burn the metal and make the steel brittle.
    Tansl has been quick to criticize other contributors as to the validity of comments on this forum and therefore I would like him to substantiate this comment.
    While I have never built a boat of STEEL, I would have assumed that the alloy would not contain enough carbon to affect any strength and certainly not become brittle without a
    quench even if it did have enough carbon.
    BUT perhaps I am missing a technical reason for a brittleness increase with the incorrect application of heat in this application. While I have not built a boat of steel, our fab shop with up to 35 people used steel in other structures, thin sheet fuel containment vessels, with significant distortion, and have never heard that heating up mild hot rolled steel, which I suspect is the main
    material used in small steel boat construction, (say to 50 feet but maybe more) would become brittle

    While it was many years ago, nothing comes to mind with several Metallurgy and Corrosion related courses taken, that such a issue as one suggested by Tansl, exits.

    Now before the technocrats jump all over these comments, about heat affecting the temper and/or brittleness of steel a qualification:
    In this application, assuming a hot rolled thin sheet, the applicationof heat to help reduce the distortion will probably not affect the strength, brittleness or corrosion resistance of the steel
     
    Last edited: Aug 31, 2018
  13. TANSL
    Joined: Sep 2011
    Posts: 6,726
    Likes: 491, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    @Barry, I do not know what it would take you to consider validated/substantiate a fact, not an idea, but I do not have such validation. I can ask others for many things, just as you can ask me for whatever you want. I would be happy to attend to your kind request but, I repeat, I do not have elements to "validate" my claim. Better said, yes I have elements to validate what I say, it is enough to have a little experience with metallic construction works to know that the steel used in shipbuilding, which is more carbon rich than "normal" steel, can lose its chemical / mechanical properties, if a flame burns it. I do not need to validate that because it is a reality. You may not have experience with large steel ships, but if you look at the structure of a burnt metal building, it may be brittle.
    I have no objection to you trying to treat me as bad as I treat others but asking me to validate/substantiate my claim is stupid. Nobody with a minimum of experience in metal boilermaking would ask for such nonsense. You do not have it and, therefore, you can not see the logic of what I say, it is not an "idea" of mine, but an accomplished fact. To paraphrase a prominent member of this forum, engineering consists of "facts".
     
    Last edited: Aug 31, 2018
  14. Barry
    Joined: Mar 2002
    Posts: 1,447
    Likes: 243, Points: 63, Legacy Rep: 158

    Barry Senior Member

    Tansl
    Nothing that I have said pertains to me treating you "bad"
    Asking you to supply information as to how this embrittlement due to "carbon rising out of the metal" was to have you supply perhaps an "engineering" rationale to your comment rather than merely state that you have seen this happen, ie the embrittlement due to an application of heat due to the carbon leaving the metal composition"
    If what you say is an "accomplished fact", then there will be a proven process that you could have supplied that supports your comments

    Some comments to your post
    1) no you don't have to validate anything, I was just inquiring as to the process,
    2) asking you to validate your previous comment, is not stupid
    3) You STATE that I do not have even" a minimum experience in metal boiler making, and would not ask for such nonsense". mmm? 37 years of owning a fab shop as part of our business,
    5 years of mechanical engineering education, 3 years working in a machine shop ( early school years, and thankfully all the machinists, welders, fabricators were European tradesman who passed on a small part of their expertise to a neophyte), 3 years in partnership owning a proprietary plating company doing plating that reduced friction and corrosion in the oil and gas industry, meeting the requirements of various standards for low pressure fuel and liquid containment vessels due to the volatile nature of the transportable liquid, gives me a little bit
    more than the "minimum experience" in this area.

    BUT note that the inquiry as to the request to substantiate your comment, I was hoping that you would have the background to supply the details of the process that you mentioned.


    To Spaceboy
    It is unlikely that with this much distortion that an application of heat will rid your boat of the unfairness of the plate. Working with the pictures that you have, I am guessing, that the raised
    hatch areas may have contributed to this high level of distortion. IT APPEARS from these few pictures that the highest amount of distortion is located along the same
    transverse line as the hatches, but it is hard to say, and I am making a guess here.

    Ie they welded in the deck, then cut holes in the sheet, added in the vertical raised section for the hatches WITHOUT providing support to limit distortion in the rest of the frame, and deck
    plate.

    I would take the advice of others and cut out the frames and distorted sections, you could provide a transverse temporary support if you are worried about any hull movement, ie
    gunnel to gunnel temp support to hold the shape.
    When you get to the hatch raised element, ensure that you have some framing immediately under the vertical hatch frame welded to the upper deck from the bottom before you cut the opening ( longitudinally and transversely ,) and cut it with a zip cut, not an oxyacetylene torch to minimize heat, and weld in the hatch frame vertical members with low heat and stitch welds
    until the weld in complete. I would also ensure that the hatch frame is not made of say 1/4 inch flat bar which when welded on the side may have enough strength when cooling to
    distort the decking. Ie make the frame hatch out of the same thickness as the deck

    These comments above are based on the chance that the area of maximum distortion is due to the incorrect installation of heavy raised hatch areas that
    MAY HAVE caused the distortion. If the distortion is everywhere and not related to the hatch elements, then the above has no validity
     
    Last edited: Sep 1, 2018

  15. TANSL
    Joined: Sep 2011
    Posts: 6,726
    Likes: 491, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Yes, but apparently it was not enough.
    Too long your speech to read it. If you have as much experience as, apparently, you are saying, why do you question what I say by asking for validate/substantiate statement? Absurd, you should know, with all that enormous experience that you say you have, that I am right.
    Given the personal touch that this seems to have acquired, I apologize if I do not answer you anymore. Try to be happy with yourself. Best wishes.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.