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Old 10-12-2006, 11:21   #1
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NTOTD: Motions of a vessel afloat

There are 6 types of motion of a vessel afloat, though apparently some disagreement over what are the correct terms for these moctions:
  • Yaw: The rotational motion of the hull around a vertical axis (the bow and stern are the extreme points which move most.)
  • Roll: The rotational motion of the hull around a fore-and-aft axis. (the masthead and the keel are the extreme points which move most.)
  • Pitch: The rotational axis of the hull around an athwartships axis. (bow, masthead, stern, and keel are all in motion.)
  • Surge: forward or aft acceleration of the hull.
  • Scend: vertical acceleration of the hull.
  • Slide or Slip: (or possibly other terms) athwartships acceleration of the hull.
Any engineers or others amongst us who can settle the dispute regarding the sideways movement of our boats?
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Old 10-12-2006, 13:54   #2
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Don't forget "Slam or Pound". =Waves/swells cumming up under the can, causing a jar.
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Old 11-12-2006, 04:57   #3
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Ship motion is generally expressed in six degrees of freedom, which can be regarded as combinations of :
three oscillations about horizontal or vertical axes :
roll, pitch, and yaw
and three linear displacements of the center of gravity:
heave, surge, and sway

Sway describes the "sliding" lateral, side-to-side motion of a ship.

Heave describes the vertical, up (scending) and down (descending) motions of the hull.
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Old 11-12-2006, 09:10   #4
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Sway!

That was the other description... I kept finding slip and slide (referring to solids not necessarily afloat)...

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