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    Silicon Sea: Leg 77
    From: Dan Hogan
    Date: 2001 Jul 25, 8:57 AM

    Chart(s): Plotting Sheets
    
    Dead-Reckoning problem     Leg 77  072601   Test your knowledge!
    ----------------------     ------  ------   --------------------
    
    Promptly at Sunrise on 24/06/2001 we raise anchor at Isl Flamenco
    (08d 55.2'N  79d 31.6'W) and head for our departure point at Isla
    San Jose Light(08d 10,5'N  79d 31.6'W) motoring.
    
    Speed = SQRT LWL x 1.34
    
    1)  What is the Zone Time (ZT) of our Estimated Time of Arrival(ETA)
        at the Isla San Jose Light?
    
        What is the UT/GMT ETA?
    --  ----------------------------------------------------------------
    
    On our ETA at Isla San Jose we take a departure FIX off of the light that is
    (08d 55.2'N  079d 29.4'W). We set our course for the Mid-Ocean Point(MOP) at
    (03d 00.0'N  110d 00.0'W).
    
    Variation 2.0dW, Dev 0.5dE. Drift 0.6 Kts Set 285.0d. Speed 10.1 Kts.
    
    2)  What is the TC and Distance from Isla San Jose Light to the MOP?
    --  ----------------------------------------------------------------
    
    We plot our track on INT Chart 811 and see that we can not head direct for
    the MOP(03d 00.0'N  110d 00.0'W) without crossing land above Punta Mala in
    Panama. So we alter course to MOP2 at (05d 00.0'N  80d 00.0'W).
    
    Variation 2.0dW, Dev 0.5dE. Drift 0.6 Kts Set 285.0d. Speed 10.1 Kts.
    
    3)  What is the True Course and distance to MOP2?
        What is the Compass Course(CC)/Course-to-Steer?
    --  -----------------------------------------------
    
    At 14:45:30UT the next morning we take a SUN LL sight. Other Data as above.
    
        Hs 47d 54.6''
    
    4)  What is the DR position?
    --  ------------------------
    
    At 22:45:23UT we take another sight of the SUN LL
    
        Hs 15d 34.3'
    
    5)  What is the DR position?
    --  ------------------------
    
    6)  What is the Running FIX(RFIX) position at the 22:35:23UT sight?
    --  ---------------------------------------------------------------
    
    Checking our Running FIX against the position of MOP2(05d 00.0'N  080d
    00.0'W) it seems we have passed MOP2. So we alter course to our original Mid-
    Ocean Point which we re-name MOP1(03d 00.0'N  110d 00.0'W).
    
    Speed 10.5 Kts. Current Set 285, Drift 0.6 Kts. Var 1dW Dev 2dE.
    
    7)  What is the TC and Dist to the MOP1(03d 00.0'N  110d 00.0'W)?
        What is the Compass Course(CC)/Course-to-Steer?
    --  -------------------------------------------------------------
    
    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
            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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