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    Silicon Sea: Leg 81
    From: Dan Hogan
    Date: 2001 Oct 17, 9:21 AM

    Chart(s): Plotting Sheets
    
    Sight Reduction and
    Dead-Reckoning problem     Leg 81  101701   Test your knowledge!
    ----------------------     ------  ------   --------------------
    
    At 13:10:12UT {at} 06/07/2001 our DR position was (07d 50.2'N  121d 39.8'W).
    We are headed for a Hawaii landfall point at (19d 30.0'N  154d 45.0'W).
    
    The sky has been overcast. Wind has been increasing and we are under a
    reefed main. The seas are building and at 13:08:00UT {at} 08/07/2001 WWV radio
    reports a large storm with gale force winds at (120d 30.0'N  019d 45.0'W)
    moving Northwest at 0.5 Kts.
    
    At 14:00:00UT {at} 08/07/2001, by log meter, we have traveled a distance of
    439.5 Nmi since our last DR position. True Course(TC) 289.9d.
    
    1)  What is the current DR position?
    --  --------------------------------
    
    2)  What is the approximate distance and direction to the storm
        (019d 45.0'W  120d 30.0'N) from our DR position at 14:00:00UT {at}
        08/07/2001?
    --  ----------------------------------------------------------------
    
    During the storm, from the time of our DR at 14:00:00UT {at} 08/07/2001 we
    sail as follows until the end of the storm:
    
        TIME        TC          SPEED
    
        6 Hrs       289.9d      9.5Kts
        12 Hrs      278.0d      6.2Kts
        5.5 Hrs     275.0d      4.5Kts
        36 Hrs      270.0d      Hove-To fore reaching at 1.3Kts
    
    3)  What is the DR position at the end of this time?
    --  ------------------------------------------------
    
    4)  What is the UT/GMT date and Time?
        What is the Zone Time(ZT) and day?
    --  ----------------------------------
    
    5)  What is the TC & Distance from the DR to our Hawaii landfall point at
        (19d 30.0'N  154d 45.0'W)
    --  ---------------------------------------------------------------------
    
    >From the DR position after the storm we pick up our TC, Speed 10.2Kts.
    Var 9.0dE Dev 1.0dE. That same evening we manage the following sights:
    
        BODY        UT/GMT          Hs
    
        Mars        03:39:20        33d 51.2'
        Unknown     03:40:15        24d 43.7' 42.0d Compass Bearing. Bright
        Antares     03:46:09        39d 40.0'
        Regulus     03:46:59        30d 15.1'
        Dubhe       03:47:45        29d 20.8'
        Rasalhague  03:48:11        41d 11.3'
    
    6)  What is the unknown body?
    --  -------------------------
    
    7)  What is the FIX position at the time of the unknown body?
    --  ---------------------------------------------------------
    
    NOTE:
    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{at}mtrs x 2.07; Nmi = SQRT HE{at}ft x 1.17.
    
    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{at}EMC.COM
            John Simmonds   - johnsimmo{at}dingoblue.net.au
            Tony Cappiello  - cappiello{at}kearfott.com
            Frank Norris    - NORRIS_FRANKLIN_H{at}LILLY.COM
            Sam Chan        - schan{at}socal.rr.com
            Mike Wescott    - wescott_mike{at}EMC.COM
            Dan Hogan       - dhhogan{at}veriomail.com
    
    
    Dan Hogan WA6PBY
    C27 "Gacha"
    dhhogan{at}verimail.com
    Nav-L Page: http://www.wa6pby.com
    

       
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