Current Events

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Current Events

• Hope fades for mudslide victims
• Widespread killings follow mosque bombing in Iraq
• Katrina report calls for urgent changes
• White House study finds pervasive failures
• through government
• The flying luxury hotel of tomorrow
• Cruise ship will sail through the air, not the
  water
• Rice and UH featured in ESPNs Pride of the
  Program last night. Good for Rice, not for UH
• Duke survives scare 73-66 over GA Tech

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Current Sailing
7/2/2009
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Lesson 12 Current Sailing

• AGENDA
• Introduction/the importance of current sailing
• The Estimated Current Triangle
• The Actual Current Triangle
• Applying current to select an optimum course
• Applicable reading Hobbs pg. 224-233.

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Definitions

• Current the horizontal movement of a body
  of water.
• Also all factors that may cause a ships
  projected position and her true position to
  differ at any time.
• Causes

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Importance of Current Sailing
Pre-Sailing Phase - Used in voyage planning
to select a course to make good your desired
track using an estimated current. Piloting Phase
- Used while navigating by comparing the DR
position to the position of the fix of the
same time. Course and speed alterations are
made based upon the calculated set and drift.
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EBB
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Current Triangles

• Estimated Current Triangle - Used during the
• pre-sailing phase using an estimating for the
• magnitude and direction of the current.
• Consists of
• TR/SOA
• Set (S) and Drift (D)
• Computed Course (C) and Speed (S).
• - Used to calculate which course and speed will
• be needed to maintain the desired TR and SOA.

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TR
SOA
C
S
D
S
Estimated Current Triangle
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Current Triangles

• Actual Current Triangle - Used during piloting
• to determine the actual set and drift.
• Consists of
• Course (C) and Speed (S)
• Set (S) and Drift (D)
• Course Over Ground (COG) and
  Speed Over Ground (SOG).
• Used to calculate which course and speed will
• be needed to maintain the desired TR and SOA.

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C
S
S
D
COG
SOG
Actual Current Triangle
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Set and Drift

• Set the direction of the current normally
  expressed in oT.
• Drift the speed of the current, normally
  expressed in knots.
• Set and drift combined describe the current.

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Actual Current Direction
0700 Fix Position
0730 DR Position
Course Speed Vector
C - 090 S - 12
Set Drift Vector Set 220 T Drift 2
kts Distance 1 NM
COG SOG Vector
0730 Fix Position
Computing Set Drift
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Example
Given the TR and SOA of the ship and the
estimated Set and Drift, find the Course and
Speed you need to drive to stay on your intended
track. TR - 090 T SOA - 12 knots D
- 225 T S (set) - 3 knots
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S - 225 D - 3
(C - 060) (S- 14)
TR - 090 T SOA - 12 kts
Example
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Example
Given that set and drift of the actual current is
045T at 3 knots and your course and speed are
090T at 12 knots, find your COG and SOG.
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Set - 045 T Drift - 3 kts
(C - 055) (S - 14)
TR - 090 SOA - 12
Example
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Estimated Position
The Estimated Position (EP) is essentially a DR
that takes into account the set and drift
experienced by the ship. See Figure 13-4 in Hobbs
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Sanity Check
Upon determining course and speed required, you
should check your plot by remembering these
points When compensating for set and drift,
all corrections must be opposite of the current
effect. 1. Current pushing ahead, decrease
speed. 2. Current pushing astern, increase
speed. 3. Current pushing left, steer more to
the right. 4. Current pushing right, steer
more to the left.
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