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    Silicon Sea II: Leg 55
    From: Dan Hogan
    Date: 1999 Jun 16, 9:16 AM

    Chart(s): Plotting Sheet
    Sight Reduction and
    Dead-Reckoning problem     Leg 55  061699   Test your knowledge!
    ----------------------     ------  ------   --------------------
    The last position FIX was at(45d 00.0'S  148d 00.4'W) 05:01:23UT @
    12/03/1999. TC 96.9d, Speed 10.3 Kts.We are bound for Trans Ocean
    Point 1(49d 00.0'S  170d 00.0'W). The weather has been solid overcast
    we experienced a storm for three days. Several of the crew were seasick.
    The seas are now large powerful rollers from the west. The wind is from
    the West at Force 6 and gusting.
    Referring to the ships Navigation Log we see that at 21:01:00UT @
    16/03/1999 we have logged 1159.2 mi since our position FIX.
    1)  What is the DR position?
        What is the Zone Description(ZD)?
    --  ---------------------------------
    The air temp is 5dC(41dF), sea temp is 6dC(42.8dF). Examining the
    Pilot Chart Of The South Pacific Ocean fo March, we see that we are
    most likely inside the sailing route for the tip of South America.
    Based on our latest DR latitude. So we alter the location of Trans Ocean
    Point 2 to(52d 30.0'S 100d 00.0'W) and steer for it.
    2)  What is the TC and Distance for the new Trans Ocean Sailing Point 2?
    --  --------------------------------------------------------------------
    Reading the pilot Chart we see that the Var is 30dE, Dev 2.0dW. Current
    Drift is 15 Kts/day, Set 90d. Speed 10.3 Kts.
    3)  What is the Compass Course(CC)/Course-To-Steer toward Trans Ocean
        Point 2(52d 30.0'S 100d 00.0'W)?
    --  -----------------------------------------------------------------
    On that same evening, on our course, we manage a round of random sights
    just visible through the clouds:
        Body            UT          Hs
        Betelgeuse      02:50:00    35d 03.6'
        Procyon         02:51:10    35d 56.2'
        Peacock         02:51:24    16d 25.3'
        Regulus         02:52:22    14d 28.8'
        Bellatrix       02:53:11    34d 29.9'
    4)  What is the DR position at the time of the first sight?
    --  -------------------------------------------------------
    5)  What is the FIX position?
    --  -------------------------
    Comparing our FIX position with our expected DR position, we see an
    unknown current effect. The Skipper decides to alter our TC to 114.1d.
    The weather worsens, we have Gale force winds and very large breaking
    rollers. We put two reefs in the main and set the storm jib. Still We
    sail for 81 Hrs and make 10.3 Kts. Var 30dE, Dev 2.5dW.
    6)  What is the DR at the end of the 81 hours of travel time?
    7)  What is the UT Time and Date at the DR position?
        What is the Zone Time (ZT) Time and Date?
    --  -------------------------------------------------
    Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 9 Feet, Index correction
    -2.5', Time hh:mm:ss in UTC/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@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  - PSmith@IMPS0014.US.DG.COM
            John Simmonds- johnsimmo@bigpond.com
            Jim Manzari  - manzari@bluewin.ch
            Dan Hogan    - dhhogan@nav.cnchost.com
    Dan Hogan WA6PBY
    Navigation-L: http://nav.cnchost.com

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