Seamanship Navigation Flashcards
Inland Rules of the Road apply to what areas
- Harbors
- Rivers and inland waters
- Except Great Lakes, portions of Mississippi, Atchafalaya River, Red River of the North
International Rules of the Road apply to
Vessels and seaplanes navigating on high seas and inland waterways of foreign countries except where local laws prevail
Bow
Front end
Stern
Rear
Athwartships
Side to side
Fore
Line parallel to keel towards bow
Aft
Line parallel to keel towards stern
Beam
Widest part of ship (amidships)
Draft
Vertical distance between keel and waterline
Masthead Light
- White light placed centerline
- 225-degree light arc
Sidelights
- Red (port), green (starboard)
- 112.5-degree light arc
Stern light
- White light placed near stern
- 135-degree light arc
When mast and both sidelights are visible
Meeting
Mast and one side light visible
Overtaking or crossing
Overtaking
- Vessel approaches from (22.5*) abaft of either beam
- Overtaking vessel must give way to boat being overtaken
Meeting/Head on,
- Masts of each vessel are in line, at night both sidelights visible
- Alter course to starboard and pass port to port
Crossing
Give-way vessel alters course and/or speed to pass astern of other
Machine driven vessels, who has right of way?
Machinery-driven vessels stand clear of vessels unless being overtaken
Restricted visibility
Visibility restricted due to fog, mist, snow, heavy rain, sandstorm
Vessels constrained by draft
Power-driven vessels restricted in ability to deviate from course due to draft and depth/width of water
Vessels restricted in ability to maneuver
Vessel which due to the nature of her work is restricted in her ability to maneuver as required by the rules of the road and is therefore unable to keep out of the way of another vessels
Examples of vessels restricted in ability to maneuver, vehicles which are:
- Dredging
- replenishment
- personnel transfer
- aircraft launch/recovery
- mine clearance
Vessel not under command
-A vessel, which through exceptional circumstances, is unable to maneuver as required by the rules of the road and is therefore unable to keep out of the way of another vessel
Power driven vessel
Any vessel propelled by machinery
Short blast
About one second in duration
Prolonged blast
From four to six seconds in duration
Bell, when is it used
Used on vessels 12 meters or more in length for sound signals
Who sets the size for vessels bells and what is the sound rating for them?
- Coast Guard
- 110 dB at 1 meter
Gong, when is it used
Used on vessels 100 meter or more in length in addition to a bell
Who sets the size and intensity of gongs?
Coast Guard
High Tide
maximum height of the water resulting from rising tide
Low Tide
minimum height of the water resulting from outgoing tide
Mean High Water
the average height of all high tide water levels measured over a 19 year period
Mean Low Water
the average height of all low water levels measured over a 19 year period
Spring Tide
occurs when the sun and moon are in line with the earth (new &full moon) combining their influences causes high tides to be higher and low tides to be lower than average
Neap Tide
occurs when the sun and moon are 90 degrees apart (first and last quarter moon), gravitational effect of sun counteracts that of the moon causing lower than normal high and low tides
Flood Current
when the horizontal movement of water is toward shore or up a tidal river
Ebb Current
when the horizontal movement of water is away from shore or down a tidal river
Slack Water
the period of time in which there is little to no current is called the minimum before flood or ebb
Set
direction of current expressed in direction toward which current flows
Drift
velocity or speed of current
Propeller Action
water is drawn from all directions forward of and around the blades creating a low pressure area on the forward face and a high pressure area on the after face, forcing it into a stream toward the stern
How does Propeller Action affect the boat?
boat move ahead as the propeller tries to move into the area of low pressure
Screw Current
water flow pattern into the arc of rotation is suction screw current
How does Screw Current affect the boat?
Thrust flow pattern out is discharge screw current which will always be stronger and more concentrated
Side Force
caused by the rotation of the propeller blade and interaction with the hull drag, discharge current against rudder, and energy transfer to water or hull
How does Side Force affect the boat?
Right handed screws will move stern starboard when going ahead and port when going backward
Cavitation
occurs when the propeller draws in an air water mixture vice water only
How does cavitation affect the boat?
causes loss of effective thrust diminishing propeller efficiency
When can cavitation occur?
- backing down
- rapid acceleration
- change in direction
What can be done to correct cavitation?
-Slowing RPMs to allow the air to dissipate
Rudder Action
Used to steer the vessel in a desired direction
What affect does Rudder Action have on the boat?
Increases pressure on one side when it is turned thus pushing the stern in one direction and causing the bow to move in the opposite direction
How does wind affect small boats?
Acts on hull topsides, superstructures, smaller boats and crew causing vessels to make a leeward at a speed proportional to wind velocity and amount of sail area
Seas
product of wind acting on the surface of the water
How do “seas” affect small boats?
They affect handling in various ways depending on their height, direction, and the vessels characteristics
How do “currents” affect small boats?
Acts on vessels underwater hull and will cause drift over ground in direction of flow
Variation
- offset from true geographic north to magnetic north
- different for different points on earth, can be found on charts given for locality
Deviation
- Effect of the ships magnetic signature on a compasses bearing, which remains constant for each heading
- Caused by magnetic metallic masses in and on ships, making ships effectively large magnets
- Annotated every 15 degrees of a complete circle
Tools required for determining course on a chart
- chart of area
- parallel rulers
- pair of dividers
How to determine course on a chart?
- place one side of parallel ruler on desired course line
- walk them to a compass rose to determine true or magnetic reading
- apply variation and deviation as required
- plan most direct route with the fewest course changes
On a compass rose, what do the inner and outer rings represent?
- Inner: magnetic reading
- Outer: true reading
While making the most direct route, what should be taken into consideration?
Check the chart carefully for hidden dangers such as rocks, shoals or submerged objects
What actions should be taken if rocks, shoals or submerged objects are noted on the map?
-Plan deviations around these objects allowing a wide berth
Line of position (LOP)
- Visual range or line determines using an object located in front of you
- Can indicate direction
- cannot indicate location
Dead Reckoning
- Process to determine the boats approximate position based on speed, time, and course along with its’ last known position
- Current, wind and other external forces are the three factors Dead Reckoning not take into account.
Compass Bearing
- Direction expressed as degrees from a reference point using a magnetic compass
- You must add/subtract deviation before it can be plotted
Relative Bearing
-Direction from the boat’s bow at 000 degrees measured clockwise thru 360 degrees
Fix
- A known position on earth
- Obtained by using two or more bearing taken simultaneously and plotted
- Position is determine by back plotting two lines, where they intersect is where you are
