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Subject: Silicon Sea: Leg 83 Rev. 12/10/01
From: Dan Hogan (dhhogan@XXX.XXX)
Date: Mon Dec 10 2001 - 10:21:21 EST
Chart(s): Plotting Sheets
Sight Reduction and Rev.12/10/01
Dead-Reckoning problem Leg 82 120101 Test your knowledge!
---------------------- ------ ------ --------------------
Our last position FIX was (11d 29.8'N 132d 29.5'W) 11/07/2001 @XXX.XXX
We are bound for a landfall at Hawaii(19d 30.0'N 154d 45.0'W). Var 10.0dE
Dev 1.0dE; Current Drift 0.7 Kts Set 285d. Speed 9.7 Kts.
1) What is the Compass Course(CC)/Course-to-Steer for our Hawaiian
landfall point?
-- ---------------------------------------------------------------
2) Based on the available information, what is the anticipated
Speed Made Good(SMG) to the Hawaii waypoint?
-- -----------------------------------------------------------
The sky has been overcast for days. we have been unable to get a sight.
Var 10.0dE Dev 1.0dE. Speed 10.4 Kts. TC
Since the last FIX(11d 29.8'N 132d 29.5'W) 11/07/2001 @ 03:40:15UT,
navigating only on dead-reckoning having sailed a total of 1170.0 Nmi.
We take a SUN LL sight:
DATE UT/GMT Hs
15/07/2001 20:10:35 61d 20.6'
3) What is the DR position?
-- ------------------------
|Current Drift 0.7 Kts, Set 285.0d.
4) What is the Speed Made Good(SMG) to this DR?
What is the Compass Course(CCMG) this DR?
-- ---------------------------------------------------
At 01:44:36UT that same day we take another SUN LL sight. Use your plotted
True Course(TC) and Speed 10.2 Kts:
Hs 40d 44.1'
5) What is the Zn bearing of the SUN at the above sight?
-- -----------------------------------------------------
6) What is the RFIX position?
-- -------------------------
7) From our DR position, what is the Distance Off and True direction of
the Running FIX?
-- --------------------------------------------------------------------
8) What is the TC and Distance to the Hawaii landfall point at
(19d 30.0'N 154d 45.0'W) from the FIX?:
You should try at least two of the methods.
On a Great Circle?
On a Rhumb Line?
On Mid-Latitude Sailing?
On Mercator Sailing?
-- -----------------------------------------------------------
8a) As an aside try calculating from the RFIX to Sydney
(33d 50.0'S 151d 20.0'E).
-- ---------------------------------------------------
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(Dead-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
Tony Cappiello - cappiello@XXX.XXX
Frank Norris - NORRIS_FRANKLIN_H@XXX.XXX
Sam Chan - schan@XXX.XXX
Mike Wescott - wescott_mike@XXX.XXX
Dan Hogan - dhhogan@XXX.XXX
*****************************ANSWERS LEG 82*******************************
1) CC= 279.7d
2) SMG= 10.4 Kts
3) DR= 18d 17.6'N 151d 17.8'W
|4) SMG= 11.1 Kts
CCMG= 279.1d
5) Zn= 282.5d
6) RFIX= 18d 37.2'N 152d 13.6'W
7) DistOff= .2 Nmi
Direction= 187.7d
8) GC= Init.
Course= 290.7d
Dist= 152.5 Nmi
RhumbLine
Course= 290.1d
Dist= 153.3 Nmi
Mid-Latitude
Course= 290.3d
Dist= 152.5 Nmi
Mercator
Course= 290.1d
Dist= 153.4 Nmi
Dan Hogan WA6PBY
C27 "Gacha"
dhhogan@XXX.XXX
Nav-L Page: http://www.wa6pby.com
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