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Subject: Silicon Sea: Leg 72
From: Dan Hogan (dhhogan@XXX.XXX)
Date: Tue May 22 2001 - 09:22:07 EDT
Chart(s): Plotting Sheet
Sight Reduction and
Dead-Reckoning problem Leg 72 052201 Test your knowledge!
---------------------- ------ ------ --------------------
Our Last position FIX was (13d 00.0'N 61d 30.1'W) at 08:50:10UT on
30/05/2001. We are bound for a point on chart INT 401 marked as Aruba Gap
(13d 50.0'N 70d 00.0'W). Aruba Gap provides a favorable westerly current of
1.5 Knts.
We have had overcast skys and have missed some possible sights. The winds
have been fluky and we have had to tack several times since our last FIX
position.
Tack 1: CC 333.0d - 04Hrs @XXX.XXX5 Kts - Var 12dW Dev 1dE
Tack 2: CC 242.0d - 11Hrs @XXX.XXX5dE
Tack 3: CC 262.0d - 08Hrs @XXX.XXX5dE
Tack 4: CC 307.0d - 10Hrs @XXX.XXX0dE
1) What is the DR position at the end of the Tack 4?
-- -------------------------------------------------
2) What is the DR position local Zone Time(ZT) and Date?
What is the DR position GMT time and Date?
-- -----------------------------------------------------
3) From the DR position, what is the TC to Aruba Gap
(13d 50.0'N 70d 00.0'W)?
-- -------------------------------------------------
Our speed is 8.5 Kts, Var 10dW Dev 1.0dE. Current Drift 0.7 Kts Set 265.0d
4) What is the Compass Course(CC)/Course-to-Steer for Aruba Gap
from the DR position?
-- ------------------------------------------------------------
The following morning the navigator see stars through breaks in the
clouds. He takes the following sights. Same data as for DR.
Body GMT/UT Hs
UNKNOWN 05:20:00 13d 07.4' (Steering Compass Bearing 009.5d)
Mars 05:21:11 50d 32.2'
UNKNOWN 05:22:03 38d 50.1' (Steering Compass Bearing 050.7d)
Vega 05:22:56 60d 55.6'
Arcturus 05:23:33 42d 49.4'
5) What is the FIX position?
-- -------------------------
6) What are the names of the two unknown bodies?
-- ---------------------------------------------
7) What is the TC and Distance to the Aruba Gap (13d 50.0'N 70d 00.0'W)
waypoint from our FIX?
-- ---------------------------------------------------------------------
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 - Smith_Peter@XXX.XXX
John Simmonds- johnsimmo@XXX.XXX
David Weilacher- daveweilacher@XXX.XXX
Tony Cappiello- cappiello@XXX.XXX
Frank Norris- NORRIS_FRANKLIN_H@XXX.XXX
Dan Hogan - dhhogan@XXX.XXX
Dan Hogan
dhhogan@XXX.XXX
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