BCM SECTION C - SEAMANSHIP, NOMENCLATURE, STABILITY Flashcards
What is the “BOW”?
Front end of a boat, going forward is to advance from the stern to the bow.
What is the “STARBOARD” side?
When facing the bow (forward) the starboard side is the “Right”
What is the “PORT” side?
When facing the bow (forward) the port side is the “LEFT” side.
What is ATHWARTSHIPS?
Line or Running from side-to-side of the boat. Left-to-Right.
What is AMIDSHIPS?
Centerline of the Vessel
What is STARBOARD BEAM?
The middle right region of the vessel (long side) that is between the Starboard bow and quarter.
What is PORT BEAM?
The middle left region of the vessel (long side) that is between the Port bow and Quarter.
What is OUTBOARD?
Action or reference that refers to the movement going from centerline outwards away from the vessel.
What is INBOARD?
Action or reference that refers to the movement going from outside to centerline of the vessel.
What is the STERN of the vessel?
The back or rear end of the vessel.
What is the PORT QUARTER
If facing forward toward the bow, this is the back left corner side of the vessel at the stern.
What is the STARBOARD QUARTER
If facing forward toward the bow, this is the back right corner side of the vessel at the stern
What is the PORT/STBD BOW
This is the left and right side of the bow.
What is the WINDWARD side?
The side where the wind is coming from. If the wind was pushing against the port beam/structure of the vessel, port would be the WINDWARD side.
What is the LEEWARD side?
The side where the wind is going/transiting away from. If the wind in striking the port side and going to the starboard, then starboard would be your down-wind LEEWARD side.
What are the (03) Hull Types?
Displacement
Semi-Displacement
Planning
Define Keel.
the centerline spine of the vessel, this lowest part makes up the “backbone” of the structure and runs fore to aft. (front to back). Keels can be internal or external.
Displacement is measured in?
Gross Weight Tons (GWT)
What’s a Through-Hull fitting?
An opening on the bottom of the hull usually to intake raw water (salt water). i.e. would be Sea Chests, Speed logs, Machinery Cooling systems, CAPAC.
(02) PRIMARY FORCEs that affect a boat’s stability
Dynamic (external)
Static (internal)
Define/Describe DYNAMIC Forces. (Stability)
Dynamic Forces are EXTERNAL forces that act on the stability of the vessel.
i.e. Waves, Winds, Currents, Tide.
Define/Describe STATIC Forces. (Stability)
Static Forces are INTERNAL “on-Ship” forces that act on the stability of the vessel. I.e. Persons, Cargo, Fluids in the Ship, Gear. ICE Build-up
Define Center of Gravity.
The center point of the vessel in which the vessel plateaus to it’s natural rest.
How does Center of Gravity change when weight is added or subtracted?
Center of Gravity follows the weight. If weight is added to the starboard side then the COG will shift right. If weight is removed it would shift left. This is what causes a “List or Lean”
Define Buoyancy.
The UPWARD acting force of water being displaced against the bottom of the surface or hull in the water.
Define Gravity in relation to Stability.
The opposing force acting DOWNWARD against buoyancy.
Define Equilibrium
The state in which the UPWARD (Buoyancy) and DOWNWARD (Gravity) equal/balance out.
What is LISTING
a PERMANENT lean in vessel caused by a vessel adding weight to one side. Examples can be all static weight sliding to one side, or flooding. This can be Dangerous and cause a vessel to capsize.
General Features Boat Features that affect Stability
Some examples: Rudder, Stability Fins, Sked, Hull design, Buoyancy Collar Features, Recesses to escape water, Scuppers, Baffles in tanks.
Effects of Freezing Spray.
Freezing Spray can cause ice build-up which becomes a static force as it is directly adhering and acting as weight on the superstructure, causing the COG to shift to the weight and offset the natural stability of the vessel. This can cause capsizing.
(02) Common Types of Keels
Bar Keel (external bar) Flat-Plate Keel (internal framework)
Describe a Displacement Hull.
Displaces the water, “pushes”. Operates at slow speed, strong stability. i.e. Sailboats, Barges, Tugboats. (Strongest Stability is Slow-Speed if towed)
Describe a Semi-Displacement Hull.
Operates as a displacement at slow speed, yet will planning or rise above the surface of the water at higher speeds. i.e. common yachts, powercrafts, cabin crusiers. (more common)
Describe a Planning Hull.
Strongest Stability and designed to normally operate at higher speeds. The hull will break the surface of the waterline easily with minimal to no displacement. (These vessels should not be operated or towed at slow speeds, due to the design is made to be most stable at higher speeds). I.e. High Speed Performance Vessels, Jet Skis aka PWC.
