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Sight Reduction and
Dead-Reckoning problem     Leg 68  080700   Test your knowledge!
----------------------     ------  ------   --------------------
Our last position FIX was at (3d 00.0'N  30d 59,9'W @ 12/05/2000 at
20:30:00UTC). Our last DR position was at a Walker Log reading of 614.4 mi
(15/05/2000 at 05:30:00ZT @XXX.XXX We are heading for the
island of Barbados(13d 10.0'N  59d 20.0'W). Speed 10.5Kts, Current
Set 280.0d, Drift 0.7Kts. Var 19dW. Dev 1.5dE.
The weather is deteriorating. Mares Tails clouds have changed to Cirrus
clouds which have been thickening and lowering. The wind is increasing and
is slowly backing.
At a Walker Log (which reads a maximum of 999.9) reading of 919.1 mi we
manage a quick sight of the Sun through a short break in the clouds.
   Body                 UT                              Hs
   Sun LL               10:31:12                66d 10.2'
Later that evening at a Log reading of 004.2 mi we manage a quick sight of
an unknown moderately bright Star through a quick break in the clouds.
        Body            Zone Time(ZT)   Hs            Steering Compass Bearing
        Unknown         18:31:12        48d 29.0'     316.0d
1)  What is the Running FIX(RFIX) position?
--  ---------------------------------------
Var 19dW, Dev 1dE. Speed 10.7Kts. Current Set 280d, Drift 0.7Kts.
2)  What is the Compass Course(CC)/Course-to-Steer for Barbados
    (13d 10.0'N  59d 20.0'W)
--  ------------------------------------------------------------
3)  What is the distance to Barbados from our RFIX?
--  -----------------------------------------------
The weather has been, scattered showers and a solid overcast. The wind has
been shifting and un-predictable. We have sailed the following courses
since our Running FIX. Speed 10.7 Kts.
        TC       DIST       TIME ON COURSE
    333.0d   213.6 mi   20:13:00Hrs
        248.0d   263.9 mi   24:40:00Hrs
        288.0d   192.6 mi   18:00:00Hrs
4)  What is the DR position at the end of this run?
--  -----------------------------------------------
5)  What is the TC and Distance to Barbados(13d 10.0'N  59d 20.0'W)
    from this DR position?
--  ---------------------------------------------------------------
6)  What is the UT date at the DR position?
--  ---------------------------------------
The highest point on Barbados is Mt. Hillaby 1104 meters.
|7)  What should the Walker Log read when we are be at the distance
     that the Navigator expects to be able to sight Mt. Hillaby on the
         horizon?
--  ------------------------------------------------------------------
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@XXX.XXX
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@XXX.XXX
        John Simmonds- johnsimmo@XXX.XXX
        Jim Manzari  - manzari@XXX.XXX
        Dan Hogan    - dhhogan@XXX.XXX
Dan Hogan
dhhogan@XXX.XXX
NAV-L Web Page: http://nav.cnchost.com

   

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