Lesson 13 Dr And Current Sailing

Slide 1: Fundamentals of Tank Naval Science Light FL 6s 58ft 9M Lon Dead Reckoning and 9 Po g int 5 5 9 9 5 9 9 9 9 11 11 5 9 Current Sailing 11 9 11 15 11 11 15 15 9 11 19 15 17 0 pa 17 19 19 96 081 17 17 19 11 20 20 10 21800 20 20 20 21 20 08 20 0 20 21 20 C- 085 T 21 21 21 S - 12 21 23 23 23 23 23 23

Slide 2: Dead Reckoning • DR - Determining the position of a vessel by adding to the last fix the ship’s true course and speed for a given time.

Slide 3: Dead Reckoning • Uses: – Determine when change course/speed – To predict the time of sighting lights and other aids to navigation – Project future positions relative to hazards – Measure the effects of current (winds, seas) – Alter course to account the effects of current

Slide 5: Plot a DR Position Every Hour on the Hour 09 10 11 00 00 00

Slide 6: Plot a DR Position at Every Course Change 29 c-090 20 C- 1 80 25 C-0 24

Slide 7: Plot a DR Position at Every Speed Change 27 21 15 S-10 S-15 S-5

Slide 8: Plot a DR Position for Every Line of Position (LOP) s-1 95 c-1 0 Tank 08 26 0826

Slide 9: Plot a DR Position for Every Fix or Running Fix 6 084 46 37 0937 R-Fix

Slide 10: A new course line shall be drawn from every fix with 2 DRs at your fix interval 0846 c- s-1 106 0 52 58

Slide 11: Typical DR plot

Slide 12: Speed-Time-Distance Calculations • using a nautical slide rule, electronic calculator, set of pre- computed tables, or speed nomogram. D=S xT where: D = distance traveled S = speed in knots T = time in hours

Slide 13: Three Minute Rule In 3 minutes a vessel travels in yards a distance 100 times its speed in knots. D = S x 100 where: D = distance traveled (yds) S = speed in knots

Slide 14: Six Minute Rule In 6 minutes a vessel travels in miles a distance equal to its speed in knots divided by 10. D = S / 10 where: D = distance traveled (nm) S = speed in knots

Slide 16: Terms Used in Current Sailing Track (TR) Speed of Advance (SOA) Course (C) Speed (S)

Slide 17: Terms Used in Current Sailing Set (S) Drift (D) Course Made Good (CMG) Speed Made Good (SMG)

Slide 18: Previous Present DR Position Fix Position Course & Speed Vector r to c CM Ve G &S ift MG Dr Ve t& cto Se r Present Fix Position Actual Current Triangle

Slide 19: Previous Future DR Position Fix Position Course & Speed Vector rre ec ed Tr or ac nt ted Cu Exp pat ct k& Ve SO or tici A Ve An cto r Estimated Position at Future Time Estimated Current Triangle

Slide 20: Actual 0700 Current Fix Position Direction 0730 DR Course & Speed Vector c - 090 T Position s - 12 kts CM G& SM Set & Drift Vector GV Set = 190 T ec tor Drift = 2 kts Distance = 1 NM 0730 Fix Position Computing Set & Drift

Slide 21: Example Given the course and speed of the ship, and the estimated set and drift, find the anticipated track and the anticipated SOA. C - 090 T S - 12 knots D - 225 T S (set) - 3 knots

Slide 22: c - 090 T s - 12 kts kt T (TR s ift 25 (S - 10 Dr t - 2 -1 0.1 2 T) -3 Se kts ) Example

Slide 23: Example Given the set and drift of the estimated current is 045 T at 3 knots, and the desired track and SOA are 090 T at 12 knots, find the course and speed needed to make the track and SOA good.

Slide 24: TR - 090 T SOA - 12 kts kt T (C (S - 102 s ift 45 -1 Dr t - 0 -3 0.2 T) Se kts ) Example

Slide 25: Sensibility Check 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.