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Silicon Sea: Leg 81
From: Dan Hogan
Date: 2001 Oct 17, 9:21 AM
From: Dan Hogan
Date: 2001 Oct 17, 9:21 AM
Chart(s): Plotting Sheets
Sight Reduction and
Dead-Reckoning problem Leg 81 101701 Test your knowledge!
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At 13:10:12UT @ 06/07/2001 our DR position was (07d 50.2'N 121d 39.8'W).
We are headed for a Hawaii landfall point at (19d 30.0'N 154d 45.0'W).
The sky has been overcast. Wind has been increasing and we are under a
reefed main. The seas are building and at 13:08:00UT @ 08/07/2001 WWV radio
reports a large storm with gale force winds at (120d 30.0'N 019d 45.0'W)
moving Northwest at 0.5 Kts.
At 14:00:00UT @ 08/07/2001, by log meter, we have traveled a distance of
439.5 Nmi since our last DR position. True Course(TC) 289.9d.
1) What is the current DR position?
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2) What is the approximate distance and direction to the storm
(019d 45.0'W 120d 30.0'N) from our DR position at 14:00:00UT @
08/07/2001?
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During the storm, from the time of our DR at 14:00:00UT @ 08/07/2001 we
sail as follows until the end of the storm:
TIME TC SPEED
6 Hrs 289.9d 9.5Kts
12 Hrs 278.0d 6.2Kts
5.5 Hrs 275.0d 4.5Kts
36 Hrs 270.0d Hove-To fore reaching at 1.3Kts
3) What is the DR position at the end of this time?
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4) What is the UT/GMT date and Time?
What is the Zone Time(ZT) and day?
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5) What is the TC & Distance from the DR to our Hawaii landfall point at
(19d 30.0'N 154d 45.0'W)
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>From the DR position after the storm we pick up our TC, Speed 10.2Kts.
Var 9.0dE Dev 1.0dE. That same evening we manage the following sights:
BODY UT/GMT Hs
Mars 03:39:20 33d 51.2'
Unknown 03:40:15 24d 43.7' 42.0d Compass Bearing. Bright
Antares 03:46:09 39d 40.0'
Regulus 03:46:59 30d 15.1'
Dubhe 03:47:45 29d 20.8'
Rasalhague 03:48:11 41d 11.3'
6) What is the unknown body?
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7) What is the FIX position at the time of the unknown body?
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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 - Smith_Peter@EMC.COM
John Simmonds - johnsimmo@dingoblue.net.au
Tony Cappiello - cappiello@kearfott.com
Frank Norris - NORRIS_FRANKLIN_H@LILLY.COM
Sam Chan - schan@socal.rr.com
Mike Wescott - wescott_mike@EMC.COM
Dan Hogan - dhhogan@veriomail.com
Dan Hogan WA6PBY
C27 "Gacha"
dhhogan@verimail.com
Nav-L Page: http://www.wa6pby.com
