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Silicon Sea II: Leg 55
From: Dan Hogan
Date: 1999 Jun 16, 9:16 AM
From: Dan Hogan
Date: 1999 Jun 16, 9:16 AM
Chart(s): Plotting Sheet
Sight Reduction and
Dead-Reckoning problem Leg 55 061699 Test your knowledge!
---------------------- ------ ------ --------------------
The last position FIX was at(45d 00.0'S 148d 00.4'W) 05:01:23UT @
12/03/1999. TC 96.9d, Speed 10.3 Kts.We are bound for Trans Ocean
Point 1(49d 00.0'S 170d 00.0'W). The weather has been solid overcast
we experienced a storm for three days. Several of the crew were seasick.
The seas are now large powerful rollers from the west. The wind is from
the West at Force 6 and gusting.
Referring to the ships Navigation Log we see that at 21:01:00UT @
16/03/1999 we have logged 1159.2 mi since our position FIX.
1) What is the DR position?
What is the Zone Description(ZD)?
-- ---------------------------------
The air temp is 5dC(41dF), sea temp is 6dC(42.8dF). Examining the
Pilot Chart Of The South Pacific Ocean fo March, we see that we are
most likely inside the sailing route for the tip of South America.
Based on our latest DR latitude. So we alter the location of Trans Ocean
Point 2 to(52d 30.0'S 100d 00.0'W) and steer for it.
2) What is the TC and Distance for the new Trans Ocean Sailing Point 2?
-- --------------------------------------------------------------------
Reading the pilot Chart we see that the Var is 30dE, Dev 2.0dW. Current
Drift is 15 Kts/day, Set 90d. Speed 10.3 Kts.
3) What is the Compass Course(CC)/Course-To-Steer toward Trans Ocean
Point 2(52d 30.0'S 100d 00.0'W)?
-- -----------------------------------------------------------------
On that same evening, on our course, we manage a round of random sights
just visible through the clouds:
Body UT Hs
Betelgeuse 02:50:00 35d 03.6'
Procyon 02:51:10 35d 56.2'
Peacock 02:51:24 16d 25.3'
Regulus 02:52:22 14d 28.8'
Bellatrix 02:53:11 34d 29.9'
4) What is the DR position at the time of the first sight?
-- -------------------------------------------------------
5) What is the FIX position?
-- -------------------------
Comparing our FIX position with our expected DR position, we see an
unknown current effect. The Skipper decides to alter our TC to 114.1d.
The weather worsens, we have Gale force winds and very large breaking
rollers. We put two reefs in the main and set the storm jib. Still We
sail for 81 Hrs and make 10.3 Kts. Var 30dE, Dev 2.5dW.
6) What is the DR at the end of the 81 hours of travel time?
---------------------------------------------------------
7) What is the UT Time and Date at the DR position?
What is the Zone Time (ZT) Time and Date?
-- -------------------------------------------------
NOTE:
Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 9 Feet, Index correction
-2.5', Time hh:mm:ss in UTC/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
dhhogan@nav.cnchost.com
Navigation-L: http://nav.cnchost.com
