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    Silicon Sea: Leg 72
    From: Dan Hogan
    Date: 2001 May 22, 09:22 EDT

    Chart(s): Plotting Sheet
    Sight Reduction and
    Dead-Reckoning problem     Leg 72  052201   Test your knowledge!
    ----------------------     ------  ------   --------------------
    Our Last position FIX was (13d 00.0'N  61d 30.1'W) at 08:50:10UT on
    30/05/2001. We are bound for a point on chart INT 401 marked as Aruba Gap
    (13d 50.0'N 70d 00.0'W). Aruba Gap provides a favorable westerly current of
    1.5 Knts.
    We have had overcast skys and have missed some possible sights. The winds
    have been fluky and we have had to tack several times since our last FIX
        Tack 1: CC 333.0d - 04Hrs @XXX.XXX5 Kts - Var 12dW Dev 1dE
        Tack 2: CC 242.0d - 11Hrs @XXX.XXX5dE
        Tack 3: CC 262.0d - 08Hrs @XXX.XXX5dE
        Tack 4: CC 307.0d - 10Hrs @XXX.XXX0dE
    1)  What is the DR position at the end of the Tack 4?
    --  -------------------------------------------------
    2)  What is the DR position local Zone Time(ZT) and Date?
        What is the DR position GMT time and Date?
    --  -----------------------------------------------------
    3)  From the DR position, what is the TC to Aruba Gap
        (13d 50.0'N  70d 00.0'W)?
    --  -------------------------------------------------
    Our speed is 8.5 Kts, Var 10dW Dev 1.0dE. Current Drift 0.7 Kts Set 265.0d
    4)  What is the Compass Course(CC)/Course-to-Steer for Aruba Gap
        from the DR position?
    --  ------------------------------------------------------------
    The following morning the navigator see stars through breaks in the
    clouds. He takes the following sights. Same data as for DR.
        Body        GMT/UT          Hs
        UNKNOWN     05:20:00        13d 07.4' (Steering Compass Bearing 009.5d)
        Mars        05:21:11        50d 32.2'
        UNKNOWN     05:22:03        38d 50.1' (Steering Compass Bearing 050.7d)
        Vega        05:22:56        60d 55.6'
        Arcturus    05:23:33        42d 49.4'
    5)  What is the FIX position?
    --  -------------------------
    6)  What are the names of the two unknown bodies?
    --  ---------------------------------------------
    7)  What is the TC and Distance to the Aruba Gap (13d 50.0'N  70d 00.0'W)
        waypoint from our FIX?
    --  ---------------------------------------------------------------------
    Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 9 Feet, Index correction
    -2.5', Time hh:mm:ss in UT,unless otherwise stated. Silicon
    Sea II is a 34,000 lb(15.40t) displacement sailing vessel, 48' 3"
    (14.70m) LOA. 39' (12.00m) LWL; Cutter rigged. Can tack to 45d.
    Water Tanks = 220 gal(1000 ltrs). Fuel Tanks = 155 gal(700 ltrs).
    Fuel consumption .675 gal/Hr at 8.5 Kts. DR(Ded-Reckoning)=position
    by sailings, EP(Estimated Position)=DR+current affect. Dist to
    Horizon: Nmi = SQRT HE@XXX.XXX
    PLEASE respond with your results and thinking on these exercises to
    the NAVIGATION list at large. If you have questions or problems, A
    lot of folks on the list are knowledgeable and willing to help. Any
    questions or doubtful areas will be responded to promptly. Let us
    hear from you soon!
    Good Navigating!
       -=The Navigation List Working Group=-
            Peter Smith  -   Smith_Peter@XXX.XXX
            John Simmonds-   johnsimmo@XXX.XXX
            David Weilacher- daveweilacher@XXX.XXX
            Tony Cappiello-  cappiello@XXX.XXX
            Frank Norris-    NORRIS_FRANKLIN_H@XXX.XXX
            Dan Hogan    -   dhhogan@XXX.XXX
    Dan Hogan

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