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Chart(s): Plotting Sheet

Sight Reduction and
Dead-Reckoning problem     Leg 58  090299   Test your knowledge!
----------------------     ------  ------   --------------------

At 17:35:00UT @ 27/03/1999, the distance log shows 147.7 mi traveled,
we are at our waypoint(55d 30.0'S  63d 00.0'W). The weather has been
steadily deteriorating, we are now in a full storm. There is very heavy
rain, low visibility and a Force 9 wind from the SW. Ocean rollers
rise to 11 feet. At the height of storm the mainsail tears at the
middle batten. We struggle through until morning repairing the sail.

At 10:00:00UT in the morning light of 28/03/1999 we see the dark out
line of an island off to port. Taking bearings, on what we determine
to be Isla de los Estadas, our DR position is plotted as(54d 50.0'S
63d 40.0'W).

1)  Using the waypoint position(55d 30.0'S  63d 00.0'W) and the DR
    position(54d 50.0'S 63d 40.0'W).
    What was the estimated speed we made during the night?
    What was the course we made?
--  ----------------------------------------------------------------

The wind backs to 45d at Force 6. Seas are confused. We have low
scudding
clouds surrounding us. Speed is 8.7 Kts, Var 10dE, Dev 1dW. We are
holding
a Compass Course(CC) of North. We continue to hold to this course until
18:00:00ZT @ 29/03/1999.

2)  What is the 18:00:00ZT DR position?
--  -----------------------------------

Our planned initial stop after rounding Cape Horn was Port Stanley,
Falkland Islands(51d 40.0'S  57d40.0'W). But the wind and the storm have
driven us past the Falkland Islands. We will have to bypass them. After
examining the Pilot Chart For The South Atlantic Ocean, which has
current
Drift in knots per Knotmeter readings, we see that there are favorable
currents close in to the coast line. We break out our planning chart
published by Brazil and decide we will have to put in at Rio de Janeiro.
The chart depths are in Meters. Silicon Sea II's fathometer maximum
reading
is 100 fathoms. The favorable current is inside the 200 meter line.


3)  Can we use  the fathometer to stay inside the 200 meter line?
--  -------------------------------------------------------------

We plot a course to get us to Rio using the best current and most
direct route. Var 10dE, Dev 1dW, Speed 10.3 Kts, Drift 0.8 Kts Set 20d.

    Rio de Janerio (22d 54.0'S  43d 10.0'W)

4)  What is the TC and Distance to Rio de Janerio from the DR position?
--  -------------------------------------------------------------------

5)  What is the Compass Course(CC)/Course to Steer-to-Steer to
    Rio de Janerio to from our DR position?
--  ----------------------------------------------------------


6)  What is the estimated UT date and time of arrival(ETA) at Rio?
--  -------------------------------------------------------------

7)  What is the time Zone Description(ZD) at Rio?
    What is the Zone Time(ZT) ETA at Rio?
--  ---------------------------------------------

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@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
C27 "Gacha"
dhhogan@nav.cnchost.com
Navigation-L: http://nav.cnchost.com

   

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