Distorted deck plating

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

  1. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi Spaceboy,
    Without being there, I would think that cutting the plate free and checking that the deck beams are fair would be my route, then re-plate - possibly using the original deck material, but that depends if it could lay fair I suppose. Our deck isn't perfect, but it's not really noticeably until you are really close up. My advice would be to not be afraid of cutting material out, it's easy to replace - if working with an empty hull (looks that way, but not sure). If you use zip cuts, make sure you have a face shield, at some point things will move and trap the wheel , sending it all over the place. You can try putting in wedges, or thin plate in you cuts to help. The first cut takes the longest, but things will be ok. You probably could have got this all fixed up in the the time this thread has been active ;)

    Cheers,
    Mark
     
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  2. spaceboy
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    spaceboy Junior Member

    James123, the boat was completed in 1990 approx., been on the hard ever since.
    SamSam, the beams are spaced at 18", the crown of the distortion is between two beams and the transverse weld is between beams,the level is 90 deg to the beams and is 6ft long.
    Mark, that seems like a plan, although I know that the beams are not quite level longitudinally, and at least one is twisted as per pic's, but until the plates are freed I won't know haw much. Although the whole deck is distorted, the afterdeck is the worst.
     
  3. JamesG123
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    JamesG123 Senior Member

    You're a braver man than I. lol. Best of luck.
     
  4. gonzo
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    gonzo Senior Member

    Of course it is not. I never said they were. The deck beams get cut first, then the deck gets jacked up. You seem to react without taking the time to read posts.
     
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  5. MikeJohns
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    MikeJohns Senior Member

    Just to get this in perspective, it's hard to tell, but the hull looks to be somewhere between 60-70 feet ? Do you know the design displacement ? I'm just curious.

    Cabin tops are usually thinner than the deck. Under the mast steps it will be thicker and the fore deck may be thicker too, do you know the plate thicknesses ?

    Unless you are on a very tight budget the best advice is always going to be to initially to employ someone skilled if you lack the skills yourself. Even if it's just for a day.
     
  6. M&M Ovenden
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    M&M Ovenden Senior Member

    It's good to agree in a couple, right? I will second Mark about cutting the deck off and starting from scratch. Fixing up a mess is most often more work then scrapping it all and starting from new. You are unlikely to fix it to your liking and you need to consider cost of regret.
    If the hull is empty, I wouldn't bother with zip cuts. Plasma cutter should be your tool of choice, and considering the cost of zip cuts to cut this much old and new plates, plasma is worth the investment (if you already have a compressor, even more so). A plasma cutter well used won't distort plate.
    If you do cut the deck out and replace it. Consider the natural coil of your plate and try to use it at you advantage. Plate comes out of the factory coiled in big rolls. The flat plates you buy have a memory of that curve and have a natural tendency to curl. Ideally you want that curl athwart ship with the deck camber.
    If you had longitudinals running accross your deck beams, those would be left floating and greatly help with the frames not being set in a fair surface. Where a frame doesn't touch the plating (when fair) you might want to add some longitudinal frames bridging accross fair frames. If the gap is small, you will need to use spacers so the weld doesn't pull the plate against the frame.
    Steel is pretty sweet to work with as, it's easy to weld on and remove temporary tabs. With angled tabs or chain links you can make all sorts of pulling/holding points for clamps or chains to pull or push your plate in place. If you are comforteable welding temporary holding points, there are many tricks to push, pull, hold plate in place.

    Cheers,
    Murielle
     
  7. Ad Hoc
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    Ad Hoc Naval Architect

    Then i'm confused why you are making two contradictory statements on the same subject...

    You seem to react without taking time to comprehend the subject matter and the posts from other members.
     
  8. TANSL
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    TANSL Senior Member

    Why is it more important to show the contradictions, if any, in someone's comments, than to give solutions to the problem posed by the OP?
     
  9. gonzo
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    gonzo Senior Member

    You are mistaken. Can you say which post you are referring to?
     
  10. SamSam
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    SamSam Senior Member

    Whatever happened to this boat?
     
  11. Magic Pearl
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    Magic Pearl New Member

    Where are the longitudinal supports, the stringers, the members in between the frames?? I don't see any in the photos.
     
  12. Magic Pearl
    Joined: Oct 2018
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    Magic Pearl New Member

    I just finished straightening some plating on our pilot house roof. Original plating is 1/8" and like your problem: had severe curling at the seams, especially the long seams (transverse) which were 2@ 10ft long each plus a couple 0f 8ft seams running longwise. Long story short it was a big pain and took three times longer than running new plate (Didn't have new plate).
    i1.jpg i2.jpg

    Distortion was so bad that it caused all the stringers to dip at every seam. Once every seam was split (plasma cut) we faired the frames by slitting them to within 1/2" of the plating, lining them up with dryline, welding the frames and stringers slits in the faired position. Then turned our attention to the plate.
     
  13. spaceboy
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    spaceboy Junior Member

    Hi , MikeJohns, the hull is 57ft lod, 35 metric ton @ half load, 5mm plating.
    Magic Pearl, there are no longitudinals, Just angle frames @18". I will take some more photo's at weekend to give a better idea of the scale of distortion.
    Like you I'm stuck with repairing what I have.
     
  14. John mc b
    Joined: Nov 2018
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    John mc b Junior Member

    Hello, I am a shipbuilder by trade, where you have a bulge in the deck both ways the best way would be to cut that piece out about 50 mm from the edge all the way around and put a new flat piece in, if when you cut the piece and it is concave just hammer around the edge and it will go flat
     

  15. John mc b
    Joined: Nov 2018
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    John mc b Junior Member

    also if the deck is concave only one way at the centre of the dip cut through with a grinder or jigsaw if you don't want sparks, then at each end of the cutmake a ten mm hole, put a wood plank under the deck and jack it up until flat then weld the cut and leave until cold ( wet the plank first ) then weld underneath, when it is cold only then weld the holes up.
     
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