NavList:
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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! ---------------------- ------ ------ -------------------- 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? -- -------------------------------- 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? -- ---------------------------------------------------------------- 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? -- ------------------------------------------------ 4) What is the UT/GMT date and Time? What is the Zone Time(ZT) and day? -- ---------------------------------- 5) What is the TC & Distance from the DR to our Hawaii landfall point at (19d 30.0'N 154d 45.0'W) -- --------------------------------------------------------------------- >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? -- ------------------------- 7) What is the FIX position at the time of the unknown body? -- --------------------------------------------------------- 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