Boat Operations Flashcards
Set
Direction toward which water is flowing, measures in True degrees
Drift
Current, wind, and waves measured in knots
Windward
Side of direction from which the wind is blowing
Leeward
Side or direction away from the wind
Pitching
Up/down motion of bow/stern
Rolling
Side to side motion
Yawing
The boat sheering off to port or starboard due to the action of waves taking charge of the stern and may cause to broach.
Flooding tide
Tidal current flowing from sea toward the shore, resulting in higher tidal stages
Ebb tide
Tidal current flowing from shore to sea, results in lower tidal stages
Slack tide
The period of no horizontal movement
Eddy current
Occurs at channel bends, uneven bottoms and near points of land. A circular current
Center of gravity
Point at which the weight of the boat acts vertically downwards
Buoyancy
The upward force of water displaced by the hull. Force of buoyancy keeps boat afloat.
Center of buoyancy
Center of gravity of displaced water.
Equilibrium
Center of buoyancy acting upwards/vertically is below the center of gravity acting downwards.
Heeling
Temporary leaning
Listing
Permanent leaning
Tripping
When a boat is pulled sideways by an opposing force. Can cause the boat to heel over beyond its ability to right itself
Two types of stability
Longitudinal (fore and aft) prevents pitching
Transverse (athrwatship) prevents capsizing
Two primary forces of stability
Static- inside forces
Dynamic- outside forces
Free surface effect
Vessel containing liquid in a compartment. The liquid can flow from side to side which makes the boat not want to right itself. This causes loss of stability
Free communication with the sea
Unobstructed movement of seawater into and out of a vessel due to damage of the hull.
Downflooding
The entry of water into the hull, due to lack of maintaining watertight integrity of a vessel.
Barometric pressure
Normal: 29.92
Dropping will cause warmer, cloudier weather. Continually decreseasing will cause weather to worsen.
Surf
Lines of waves that mount higher as they pass over shallower water and finally break as they near the beach.
Breaker
A wave or swell of the sea breaking on the shore, shoal, reef bar or inlet.
Window
Area where waves have momentarily stopped breaking
High/low side of wave
High- carries most potential energy
Low- least potential energy and represents the safest direction to turn
Saddle
Lowest part of wave
Closeouts
Two waves breaking towards each other. Should be avoided
Shoulder
The edge of a wave
Rip current
A relatively strong, narrow current flowing outward from the beach through the surf zone and presenting a hazard to swimmers
Chine
The edge formed on the hull of a flat bottomed or V shaped boat where the bottom joins the topside.
Hard chine lockup
Boat suddenly heeling 50-80 degrees on a false keel. Must turn into direction of heel and immediately back to amidships to rock MLB off it’s false keel.
Types of breaking waves
Plunging
Spilling
surging
Surf
Several waves or swells of the sea breaking on the shore, shoal, reef, bar, or inlet
Swell
Distant wind generated waves which have advanced to calmer and more rounder form. The heave of the sea.
Wave
A periodic disturbance of the sea caused by local winds
Plunging
Lack of water ahead of the wave. Raises up suddenly and breaks with tremendous force.
Spilling
Generated when the ocean floor has a gentle slope, gradually spills forward down its face until it is all whitewater.
Surging
Wave builds very quickly and expands its anger on the beach
Pitch
Distance a propeller would travel in 1 revolution
Cavitation
the formation of bubbles in a liquid, caused by low pressure in the suction intake by the movement of a propeller.
This creates less pressure. Resulting in lest thrust.
Side force/ prop walk
Stern moves sideways due to unequal blade thrust.
