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Silicon Sea: Leg 77 Rev 08/13/2001
From: Dan Hogan
Date: 2001 Aug 13, 9:40 AM
From: Dan Hogan
Date: 2001 Aug 13, 9:40 AM
Chart(s): Plotting Sheets
Revised
Dead-Reckoning problem Leg 77 081301 Test your knowledge!
---------------------- ------ ------ --------------------
Promptly at Sunrise on 24/06/2001 we raise anchor at Isl Flamenco
(08d 55.2'N 79d 31.6'W) and head for our departure point at Isla
San Jose Light(08d 10.5'N 79d 15.0'W) motoring.
Speed = SQRT LWL x 1.34
1) What is the Zone Time (ZT) of our Estimated Time of Arrival(ETA)
at the Isla San Jose Light?
What is the UT/GMT ETA?
-- ----------------------------------------------------------------
On our ETA at Isla San Jose we take a departure FIX off of the light that
is (08d 10.5'N 079d 18.0'W). We set our course for the Mid-Ocean Point
(MOP) at (03d 00.0'N 110d 00.0'W).
Variation 2.0dW, Dev 0.5dE. Drift 0.6 Kts Set 285.0d. Speed 10.1 Kts.
2) What is the TC and Distance from the Isla San Jose Light departure
point (08d 10.5'N 079d 18.0'W) to the MOP(03d 00.0'N 110d 00.0'W)?
-- --------------------------------------------------------------------
We plot our track on INT Chart 811 and see that we can not head direct for
the MOP(03d 00.0'N 110d 00.0'W) without crossing land above Punta Mala in
Panama. So we alter course to MOP2 at (05d 00.0'N 80d 00.0'W).
Variation 2.0dW, Dev 0.5dE. Drift 0.6 Kts Set 285.0d. Speed 10.1 Kts.
3) What is the True Course and distance to MOP2 from our Departure point?
What is the Compass Course(CC)/Course-to-Steer?
-- ----------------------------------------------------------------------
The weather has high Cirrus clouds building, wind from the Southwest.
At 14:45:30UT the next morning we take a SUN LL sight. Other Data as above.
| Hs 47d 27.2'
4) What is the DR position?
-- ------------------------
At 22:45:23UT we take another sight of the SUN LL
Hs 10d 07.2'
5) What is the DR position?
-- ------------------------
6) What is the Running FIX(RFIX) position at the 22:45:23UT sight?
-- ---------------------------------------------------------------
Checking our Running FIX against the position of MOP2(05d 00.0'N
080d 00.0'W) it seems we have passed MOP2. So we alter course to our
original Mid-Ocean Point which we re-name MOP1(03d 00.0'N 110d 00.0'W).
Speed 10.5 Kts. Current Set 285, Drift 0.6 Kts. Var 1dW Dev 2dE.
7) What is the TC and Dist to the MOP1(03d 00.0'N 110d 00.0'W)?
What is the Compass Course(CC)/Course-to-Steer?
-- -------------------------------------------------------------
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
