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Listen to a steel ship just built in 1943, what do I hear?

  1. Dec 20, 2016 #1
    Saw a movie for free on YouTube, "Away All Boats"



    At minute 4:44 an old timer listens to the ship and hears "her" talking. An ex ship captain explains to the old timer that the sound he hears are built up stresses from welding in the newly constructed ship being released.

    Has anyone ever heard such a sound in a newly constructed ship and if so can you describe the sound?
     
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  3. Dec 20, 2016 #2

    jedishrfu

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  4. Dec 20, 2016 #3

    anorlunda

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    I watched the video linked by at OP at minute 4:44. In the movie, the sounds were heard while still in drydock before launching.
     
  5. Dec 20, 2016 #4

    jedishrfu

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    Its possible that the ship would have some noises but remember its Hollywood.
     
  6. Dec 20, 2016 #5

    anorlunda

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    By the way, those videos were quite impressive. The sight of the ship flexing is frightening. It reminds me of the day I was flying in a Super-DC8 airliner, and transverse bending waves traveled up and down the fuselage like it was wet spaghetti. It was very scary to passengers.

    My own vessel is a Westsail 32, reputed to be one of the most seaworthy designs existing. I've never noticed her flex at all, even in the roughest conditions, so the mere idea of flexing scares me. But another famous sailboat brand, I have heard skippers refer to as bendy-tau.
     
  7. Dec 20, 2016 #6

    russ_watters

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    I would think that "stresses working out" itself would have no sound as it is just deformation of metal. But associated with that would be metal-on-metal rubbing as parts of the ship move around a bit. That would be typical metal creaking.
     
  8. Dec 23, 2016 #7

    Baluncore

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    I would expect a riveted boat to creak as the overlapping plates settle against each other. On the other hand, a newly welded boat that makes cracking noises would worry me as it would indicate cracking of welds due to gas inclusion or thermal contraction.
    Properly designed weldments should not crack, they should be designed to plastically deform the material.

    A fully welded hull can be expected to efficiently propagate any sound.

    Remember the old saying “A good ship creaks”. It is probably better to creak than to build up greater stored energy in a structure.
     
  9. Dec 23, 2016 #8

    anorlunda

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    Does it have to be the welds? I think the question is interesting. The word creak sounds right, even if we normally think of creaking in terms of wood.

    Suppose we take a steel plate say bigger than 300x300x2 cm and subject it to moderate external bending forces that do not cause permanent deformation. During the bending, I would expect it to make noise, but would the noise cease instantly when the plate becomes stationary? I don't know the answer to that, but instinct tells me that residual noises may continue for some time, as some stresses are relieved at the molecular level. When the external forces are removed, the noises would resume for a while.
     
  10. Dec 23, 2016 #9

    Baluncore

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    Those sounds are known to occur and are too small to be heard by the human ear.
    If stresses are being relieved at the molecular level then dislocations are migrating and mechanical energy is being radiated. That loss of energy seems to contradict your " ... and subject it to moderate external bending forces that do not cause permanent deformation".

    Is it good that a ship talks? There is no question that a steel ship will generate noises while releasing energy stored during manufacture. With time the stresses of manufacturer will be relieved by exercise and the noises should reduce.
    Britain transitioned from riveted to welded ship construction during WW2. The USA had largely transitioned before WW2. Preheating of steel before welding is needed in cold environments. It is quite possible that the quality of the welds used in wartime ship construction were below standard and may have made more cracking noises than we would find acceptable today.
    When I have used insufficient preheating before welding a hard steel, I have heard the cracks following me along the weld. That distinctive sound tells me to go back, grind all the cracks out, preheat it properly and then start the weld again.
     
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