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    Silicon Sea: Leg 82
    From: Dan Hogan
    Date: 2001 Dec 02, 2:51 PM

    Chart(s): Plotting Sheets
    Sight Reduction and
    Dead-Reckoning problem     Leg 82  120101   Test your knowledge!
    ----------------------     ------  ------   --------------------
    Our last position FIX was (11d 29.8'N  132d  29.5'W) 11/07/2001 @ 03:40:15UT.
    We are bound for a landfall at Hawaii(19d 30.0'N  154d 45.0'W). Var 10.0dE
    Dev 1.0dE; Current Drift 0.7 Kts Set 285d. Speed 9.7 Kts.
    1)  What is the Compass Course(CC)/Course-to-Steer for our Hawaiian
        landfall point?
    --  ---------------------------------------------------------------
    2)  Based on the available information, what is the anticipated
        Speed Made Good(SMG) to the Hawaii waypoint?
    --  -----------------------------------------------------------
    The sky has been overcast for days. we have been unable to get a sight.
    Var 10.0dE Dev 1.0dE. Speed 10.4 Kts.
    Since the last FIX(11d 29.8'N  132d 29.5'W) 11/07/2001 @ 03:40:15UT,
    navigating only on dead-reckoning having sailed a total of 1170.0 Nmi.
    We take a SUN LL sight:
        DATE          UT/GMT        Hs
        15/07/2001    20:10:35      61d 20.6'
    3)  What is the DR position?
    --  ------------------------
    4)  What is the Speed Made Good(SMG) to this DR?
        What is the Compass Course(CCMG) this DR?
    --  ---------------------------------------------------
    At 01:44:36UT that same day we take another SUN LL sight. Use your plotted
    True Course(TC) and Speed 10.2 Kts:
        Hs 40d 44.1'
    5)  What is the Zn bearing of the SUN at the above sight?
    --  -----------------------------------------------------
    6)  What is the RFIX position?
    --  -------------------------
    7)  From our DR position, what is the Distance Off and True direction of
        the Running FIX?
    --  --------------------------------------------------------------------
    8)  What is the TC and Distance to the Hawaii landfall point at
        (19d 30.0'N  154d 45.0'W) from the FIX?:
        You should try at least two of the methods.
        On a Great Circle?
        On a Rhumb Line?
        On Mid-Latitude Sailing?
        On Mercator Sailing?
    --  -----------------------------------------------------------
    8a) As an aside try calculating from the RFIX to Sydney
        (33d 50.0'S  151d 20.0'E).
    --  ---------------------------------------------------
    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(Dead-Reckoning)=position
    by sailings, EP(Estimated Position)=DR+current affect. Dist to
    Horizon: Nmi = SQRT HE@mtrs x 2.07; Nmi = SQRT HE@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@EMC.COM
            John Simmonds   - johnsimmo@dingoblue.net.au
            Tony Cappiello  - cappiello@kearfott.com
            Frank Norris    - NORRIS_FRANKLIN_H@LILLY.COM
            Sam Chan        - schan@socal.rr.com
            Mike Wescott    - wescott_mike@EMC.COM
            Dan Hogan       - dhhogan@veriomail.com
    *****************************ANSWERS LEG 82*******************************
    1) CC= 279.7d
    2) SMG= 10.4 Kts
    3) DR= 18d 17.6'N  151d 17.8'W
    4) SMG= 10.8 Kts
       CCMG= 280.3d
    5) Zn= 282.5d
    6) RFIX= 18d 37.2'N  152d 13.6'W
    7) DistOff= .2 Nmi
       Direction= 187.7d
    8) GC= Init.
            Course= 290.7d
            Dist= 152.5 Nmi
            Course= 290.1d
            Dist= 153.3 Nmi
            Course= 290.3d
            Dist= 152.5 Nmi
            Course= 290.1d
            Dist= 153.4 Nmi
    Dan Hogan WA6PBY
    C27 "Gacha"
    Nav-L Page: http://www.wa6pby.com

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