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Re: Silicon Sea: Leg 70
From: Michael Wescott
Date: 2001 Apr 25, 12:38 EDT
From: Michael Wescott
Date: 2001 Apr 25, 12:38 EDT
-------- Sorry for the delay ... busy at work and I fumble-fingered the first try and didn't send to the list. > Direct Passage Plan Waypoints: > > Bridgetown 13d 05.5'N 59d 47.4'W > ST Lucia/St Vincent Pass 13d 30.0'N 61d 10.0'W > MOP1(N of Aruba) 12d 30.0'N 70d 00.0'W > Cristobal, Panama 09d 23.0'N 79d 55.0'W > > > 1) What is the total distance in nautical miles to Cristobal? > -- ---------------------------------------------------------- Using Mid-latitiude sailings Leg 1 = 80.4 (MLat = 13d18') Leg 2 = 516.4 (MLat = 13d) Leg 3 = 584.1 (MLat = 11d) Total 1217.3 > If Silicon Sea's average speed is 7.5 Knots under sail. > > 2) How many days (to the nearest tenth) is it to Cristobal? > -- -------------------------------------------------------- 1217.3/7.5/24 = 6.8 days > The boat is stocked, the compass repaired and swung. All fuel, water and > supplies are topped off (See NOTE Below). After our final checks, we > depart Bridgetown at |Sunrise(SR) 29/5/2001. Speed 8.1 Kts, Var 13dW, Dev > 2dW. Current Set 270, Drift 0.7 Kts. > > Bridgetown Departure 13d 05.5'N 59d 47.4'W > St. Lucia Is./St. Vincent Is. Pass 13d 30.0'N 61d 10.0'W > > 3) What is our Zone Time(ZT) ETA at the St. Lucia/St. Vincent > Pass waypoint? > -- ----------------------------------------------------------- Sunrise: 29-05-2001 From almanac for 10d is 0538 LMT minus interpolation of 5 min minus another minute (being east of central meridian by 12.6') give departure of 0532 ZT. From plotting sheet: C=287T S=8.7 Dist=84.5 Time = 9.71h = 9h43m. ETA = 1525 > 4) What is the Compass Course/Course-to-Steer for the Pass? > -- -------------------------------------------------------- From plotting sheet: C = 287T Correcting for current C=289T Correcting for Var C=302M > The navigation is pilotage as we can see several of the Lessor Antilles > islands. The islands highest points are, St. Lucia 959 mtrs(13d 50.1'N > 64d 04.0'W); |St. Vincent 1219 mtrs(13d 15.7'N 61d 10.0'W). Var 13dW, > Speed 8.0 Kts. Using a handbearing compass at 18:27:00ZT we take the > following bearings, : Seems like that puts St Lucia 150 mi too far West. Made up to fit the problem? > St. Lucia 292.2d > St. Vincent 129.7d Account for Var: 279.2T and 116.7T > 5) What is our Departure point position to the nearest minute? > -- ----------------------------------------------------------- From plotting sheet: 13 25'N 61 28'W > 6) What is the TC from our departure point to MOP1(12d 30.0'N 70d > 00.0'W)? > What is the distance? > -- --------------------------------------------------------------- Using mid latitiude sailing (ML = 13): d.Lat = -55 d.Lo = -512 cos 13 * d.Lo = -498.9 TC = atan2(-55, -498.9) = 263.7 dist = sqrt(55^2 + 498.9^2) = 501.9 TC = 263.7 Dist = 501.9 > Var 13dW, Dev 1.5dE. Current Set 270d, Drift 0.7 Kts. > > 7) What is the Compass Course(CC)/Course-to-Steer for MOP1? > -- -------------------------------------------------------- With current almost directly behind us there shouldn't be much difference. Using law of cosines to account for current C=262.9T Add 13 for W Var C=275.9M Sub 1.5 for E Dev C=274.4C CC = 274.4 <PRE> -- Mike Wescott Wescott_Mike@XXX.XXX --==_Exmh_-18116158520 Content-Type: text/plain Mike Wescott Wescott_Mike@XXX.XXX </PRE>