Amidships Chain Storage

Discussion in 'Sailboats' started by Ted Royer, Jul 20, 2018.

  1. gonzo
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    gonzo Senior Member

    The complexity of the system is not relevant. The response of it is. If the system responds to a disturbance (input) by oscillating, then it is vibrating. They are the synonymous. If only part of the system oscillates/vibrates and the rest is completely isolated, then it is different. However, an anchored boat, if it responds to the disturbance by oscillating/vibrating, is a vibratory system.
    An example of a system that has elements that vibrate but does not vibrate as a whole would be a microphone. The diaphragm vibrates, but the rest of it doesn't to any significant degree.
     
  2. TANSL
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    TANSL Senior Member

    Exactly, the same happens with a sea in which there is a boat with an anchor and a catenary. The boat, the catenary or the anchor, or all of them at once, can vibrate, but the sea "doesn't to any significant degree".
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    No wonder you you're in such a pickle and don't understand if you keep consistently mixing up definitions.

    Oscillations = is a simple back and forth motion. A motion that repeats itself. Like the moon oscillates around the earth, or the stone stuck in the tyre of my mountain bike as i peddle..it oscillates around the centre of the wheel. It doesn't vibrate around the wheel.

    Vibrations = there is an inherent restoring force in the body to bring the body back to its equilibrium.

    Confusion arises when both are exhibited and conflated as being the same.
     
  4. MikeJohns
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    MikeJohns Senior Member


    Yes
    Vibrations are oscillatory in their nature but it's quite incorrect to suggest any system with resonance in some conditions can be fully modeled as a vibratory mechanical system.

    The very definition of mechanical vibration is that it's movement about a defined position. The mass components in a vibratory model return to a defined steady state position at rest. The masses in a mechanical vibration are all linked by spring damper functions. That's why I keep saying to Gonzo that it's just not even sensible to suggest it's a valid model except for some small select part of a systems response.

     
  5. gonzo
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    gonzo Senior Member

    That is completely incorrect. Only a damped system will go to a static condition. Otherwise it will continue to vibrate.
     
  6. gonzo
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    gonzo Senior Member

    You are also wrong. The basic vibrating system is a mass and a spring. If it is disturbed from its resting position it will continue to vibrate forever.
     
  7. Ad Hoc
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    Ad Hoc Naval Architect

    So, again, you have no idea what oscillation means....and thus no idea what vibration means and the difference between the two. Why..because your reply, yet again, has nothing, i shall repeat this, nothing to do with the definition of oscillation and/or vibration. Thus clearly demonstrating, again, a total lack of comprehension of the subject matter at hand. Cut and pasting words doesn't obfuscate this simple fact - you remain ignorant on this subject and its associated definitions, despite your protestations to the contrary.

    It is yet again, another non-sequitur, to obscure your lack of understanding on 2 very very simple terms and their definitions, that being, oscillation and vibration.

    So, forthwith, some basic definitions for you regarding: oscillation and vibration:-

    Here and Here

    I did try to find a more simplistic one liner in the manner of your prose, but unable to. But hey, the message is there...and took just a mere few seconds on Google to find too.

    But i did find this
     
    Last edited: Aug 10, 2018
  8. MikeJohns
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    MikeJohns Senior Member



    Well you are confusing an Ideal Mechanical vibration with a Basic Mech vibration and forgetting the damper. Every Basic model of any Vibratory System consists of a Spring-Mass-Damper system. Without continuing excitement, it must come to rest. You know that.

    But regardless even the ideal system has a rest position. It's the position it was in before it started vibrating and the position it would adopt if you stopped it vibrating. This is a pretty fundamental model that you should have grasped.

    I keep trying to tell you that Mechanical Vibration, is quite specifically the movement of a body or bodies in an oscillatory manner about a defined position where the motion of the bodies can be modeled as though connected by spring mass damper connections.

    Why don't you read the definition in any undergraduate Introductory Mechanical Vibration textbook. Surely you have one if you've just studied this ?
     
    Last edited: Aug 10, 2018
  9. gonzo
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    gonzo Senior Member

    Are you claiming than only a damped system can oscillate?
     
  10. gonzo
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    gonzo Senior Member

    I think that is you state that "Mechanical Vibration, is quite specifically the movement of a body or bodies in an oscillatory manner about a defined position where the motion of the bodies can be modeled as though connected by spring mass damper connections", that is pretty close to what I said.
    However, the simplest vibrating system only needs a mass and a spring.
     
  11. Ad Hoc
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    Ad Hoc Naval Architect

    So...here we go again. let's try this:

    If an animal goes 'quack'...and it waddles as it walks....it is a Duck!
    If an animal has four legs and says 'Woooof"..it is a dog!

    Oh, hang on....what have either of these statements got to do with the definition of oscillation and vibration - nothing. Correct!

    See, it is very easy to introduce non-sequiturs into a debate. Which is what you've done, yet again....another twist and turn away.

    So, a quick recap:

    and then

    By where i decided to point out that an oscillation is not a vibration and gave you the definition of each for clarity:

    After which you ignored the definitions (for whatever reason) and again went into your non-sequitur mode, introducing totally unrelated arguments to the simple definition of oscillation and vibration - because you either do not know or did not know or ignore to know this, as it would invalidate your statements of:

    So, for example, your last pearl of wisdom is this:

    Again absolutely NOTHING to do with the definition of oscillation and/or vibration - another non-sequitur. I even gave you a simple definition that had no difficult words to read via youtube one that is almost a one liner - your MO.

    Yet in the meantime you have since gone back and attempted to hide this fact by changing your statement to now read:

    You are very obviously unable to debate engineering issues as you are unable to start any debate that uses well known and well defined terms, words, phrases that have a very clear and unique meaning. The basis for any argument must begin with an acceptable definition of what one is debating from the outset to frame the limits. Thus, the argument can progress since those debating all understand the baseline, the common definition that one is able to find in any text book, or where required for brevity website (as posted) and even on a youtube video.

    Yet you continue to elect and i do stress selectively elect not to use these well established definitions as a common baseline to start an argument because it immediately invalidates your opening premise.
    In layman's language the definitions show you're wrong. And since you elect not to use established terms and definitions in order to control the narrative to your own incorrect definitions it just makes the whole situation untenable and hence the endless nonsense and pages of non-technical rigour and debate on this thread and the other one.
     
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  12. MikeJohns
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    MikeJohns Senior Member

    That’s actually irrelevant .



    Your reply:
    Only short of one very specific term.

    However, not only is there no predictable fixed rest position, but a Craft on a single point mooring does not respond like a vibration anyway. It has a large [ geographical ] area of freedom within which it’s loosely tethered to a single point.
     
    Last edited: Aug 12, 2018
  13. gonzo
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    gonzo Senior Member

    I don't understand what you mean by "area of freedom" I have never heard that term. Usually, we refer to degrees of freedom, of which there is a maximum of six.
     
  14. gonzo
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    gonzo Senior Member

    It is difficult to wade through the rant, so I will limit my response to one item only: your claim that a vibration and an oscillation are completely different phenomena. The definition of vibration, is that it is a mechanical oscillation.
     

  15. TANSL
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    TANSL Senior Member

    It is not fun to see how some are incapable of explaining to another what that other is not capable of understanding or how the other thinks that by repeating the same thing a thousand times that is going to become true. Who will have enough generosity to avoid this show? Thanks, in advance, to the first who tries.
     
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