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    Re: Silicon Sea: Leg 70
    From: Michael Wescott
    Date: 2001 Apr 25, 12:38 EDT

    --------
    Sorry for the delay ... busy at work and I fumble-fingered the first try and
    didn't send to the list.
    > Direct Passage Plan Waypoints:
    >
    >     Bridgetown                  13d 05.5'N  59d 47.4'W
    >     ST Lucia/St Vincent Pass    13d 30.0'N  61d 10.0'W
    >     MOP1(N of Aruba)            12d 30.0'N  70d 00.0'W
    >     Cristobal, Panama           09d 23.0'N  79d 55.0'W
    >
    >
    > 1)  What is the total distance in nautical miles to Cristobal?
    > --  ----------------------------------------------------------
    Using Mid-latitiude sailings
    Leg 1 =  80.4  (MLat = 13d18')
    Leg 2 = 516.4  (MLat = 13d)
    Leg 3 = 584.1  (MLat = 11d)
    Total 1217.3
    > If Silicon Sea's average speed is 7.5 Knots under sail.
    >
    > 2)  How many days (to the nearest tenth) is it to Cristobal?
    > --  --------------------------------------------------------
    1217.3/7.5/24 = 6.8 days
    > The boat is stocked, the compass repaired and swung. All fuel, water and
    > supplies are topped off (See NOTE Below). After our final checks, we
    > depart Bridgetown at |Sunrise(SR) 29/5/2001. Speed 8.1 Kts, Var 13dW, Dev
    > 2dW. Current Set 270, Drift 0.7 Kts.
    >
    >     Bridgetown Departure                    13d 05.5'N  59d 47.4'W
    >     St. Lucia Is./St. Vincent Is. Pass      13d 30.0'N  61d 10.0'W
    >
    > 3)  What is our Zone Time(ZT) ETA at the St. Lucia/St. Vincent
    >     Pass waypoint?
    > --  -----------------------------------------------------------
    Sunrise: 29-05-2001
    From almanac for 10d is 0538 LMT minus interpolation of 5 min minus
    another minute (being east of central meridian by 12.6') give departure
    of 0532 ZT.
    From plotting sheet:
    C=287T S=8.7 Dist=84.5
    Time = 9.71h = 9h43m.
    ETA = 1525
    > 4)  What is the Compass Course/Course-to-Steer for the Pass?
    > --  --------------------------------------------------------
    From plotting sheet:
    C = 287T
    Correcting for current C=289T
    Correcting for Var C=302M
    > The navigation is pilotage as we can see several of the Lessor Antilles
    > islands. The islands highest points are, St. Lucia 959 mtrs(13d 50.1'N
    > 64d 04.0'W); |St. Vincent 1219 mtrs(13d 15.7'N  61d 10.0'W). Var 13dW,
    > Speed 8.0 Kts. Using a handbearing compass at 18:27:00ZT we take the
    > following bearings, :
    Seems like that puts St Lucia 150 mi too far West. Made up to fit the
    problem?
    >     St. Lucia    292.2d
    >     St. Vincent  129.7d
    Account for Var: 279.2T and 116.7T
    > 5)  What is our Departure point position to the nearest minute?
    > --  -----------------------------------------------------------
    From plotting sheet:
            13 25'N   61 28'W
    > 6)  What is the TC from our departure point to MOP1(12d 30.0'N 70d
    >         00.0'W)?
    >     What is the distance?
    > --  ---------------------------------------------------------------
    Using mid latitiude sailing (ML = 13): d.Lat = -55  d.Lo = -512
    cos 13 * d.Lo = -498.9 TC = atan2(-55, -498.9) = 263.7
    dist = sqrt(55^2 + 498.9^2) = 501.9
    TC = 263.7
    Dist = 501.9
    > Var 13dW, Dev 1.5dE. Current Set 270d, Drift 0.7 Kts.
    >
    > 7)  What is the Compass Course(CC)/Course-to-Steer for MOP1?
    > --  --------------------------------------------------------
    With current almost directly behind us there shouldn't be much
    difference. Using law of cosines to account for current C=262.9T
    Add 13 for W Var C=275.9M
    Sub 1.5 for E Dev C=274.4C
    CC = 274.4
    <PRE>
    --
            Mike Wescott
            Wescott_Mike{at}XXX.XXX
    --==_Exmh_-18116158520
    Content-Type: text/plain
            Mike Wescott
            Wescott_Mike{at}XXX.XXX
    </PRE>
    

       
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