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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Silicon Sea II: Leg 49
From: Dan Hogan
Date: 1999 Mar 15, 7:19 AM

```Chart(s): Plotting Sheets

Dead-Reckoning problem     Leg 49  031599   Test your knowledge!
----------------------     ------  ------   --------------------

Our last position FIX was at (35d 00.2'S  156d 59.7'E) at 09:05:22 {at}
18/02/1999GMT.Speed 8.7Kts, TC 86.8d Var 13dE, Dev 2.0dE. Current Drift
17 mi/day, set 185 according to the Pilot Chart. We continue on course
through the night. The weather is deteriorating and it begins to rain.
At 19:45:00GMT the wind heads us and we are forced to change our
Compass
Course(CC) 45d to port to stay close-hauled.

1)  What is the DR position at the time of the course change?
--  ---------------------------------------------------------

2)  Taking all factors in consideration, what is the TC we are
making good?
--  ----------------------------------------------------------

A storm has come up and we battle Wind and Sea. The boat is bouncing
hard and the knotmeter is oscillating wildly. We use the distance log
on the knotmeter. The storm has caused us to sail the following legs:

TC      Speed   Dist    Time/in/Hrs

072d     8.7     91.3    10:30:00
027d     8.7     52.2    18:30:00
122d     7.5    198.1    26:25:00
095d     9.5    311.1    32:40:00

3)  What is the DR position at the end of the storm?
--  ------------------------------------------------

4)  What is the GMT Time and Date of the DR position?
What is the Zone Time(ZT) and Date of the DR position?
--  ------------------------------------------------------

5)  What is the TC and distance to our destination at(40d 50.0'S
174d 20.0'E)?
--  ------------------------------------------------------------

A look at our charts shows that we are off of New Zealand's North
Island. The chart shows that Mt. Egmont, 2518 mtrs high, sits on the
headland at the bight between North and South Islands and is our best
land mark.

6)  At what distance should we be able to see the mountain on the
horizon?
-------------------------------------------------------------

With a speed of 9.7 Kts.

7)  About what what Zone Time(ZT) and date should we expect to have
Mt.Ebmont on the horizon?
--  ---------------------------------------------------------------

NOTE:
Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 9 Feet, Index correction
-2.5', Time hh:mm:ss in UTC/GMT,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{at}mtrs x
2.07; Nmi = SQRT HE{at}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{at}wellspring.us.dg.com
John Simmonds- mobi{at}netconnect.com.au
Jim Manzari  - manzari{at}bluewin.ch
Dan Hogan    - dhhogan{at}concentric.net

Dan Hogan WA6PBY
dhhogan{at}concentric.net
Catalina 27 "GACHA"
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