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Old 15-02-2011, 11:49   #16
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plus before electronics...if you "dead reckoning" was off...many times you were either "dead"or about to be....
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Old 15-02-2011, 13:27   #17
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In Elizabethan English 'dead' had also the meaning of absolute; thus dead reckoning, which also dates to 16th century English, had the meaning of finding your way between point A and point B without any means to fix your position other than calculations to take into account deviations from your base line course as affected by wind, tide, current and a ship or boat's hydrodynamic characteristics.
As in "dead to rights"? Cool. I forgot about that one.
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Old 15-02-2011, 14:12   #18
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The old ways also allowed for some leeway in your story telling. Columbus went to his grave claiming he'd been to Japan and China although he was out by about half a world. It helped to be really stubborn I think since at that point no-one else believed him! Of course in those days you probably counted yourself lucky if you didn't fall off the edge of the world or get eaten by sea monsters. There's your dead reckoning for you!
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Old 15-02-2011, 14:17   #19
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As most of you are aware, Slocum only had a castoff alarm clock with just the hour hand, no minute or second hand. He used Lunars because that was the only way he could get Longitude without a chronometer. The tables for calculating lunars were taken out of Bowditch and/or the almanacs sometime around the turn of the century, that's the previous century. Accurate chronometers had become relatively cheap and universally available by that time. Navigators were no longer using lunars and/or being taught how to reduce them.

Doubt that Josh would have used GPS unless someone gave it to him and the batteries to power it. Why else would he have left without a proper chronometer other than a severe lack of money and/or extreme frugality? Even though he knew how to get Longitude from Lunars, FWIU they require high level competence in spherical geometry and are arduous and time consuming to calculate. His life would have been much easier with a proper Chronometer. Then again, he may have just been a retro-grouch and preferred to do it the hard way.

Any modern boat should have an electronic log and possibly a taff rail log. I always drag my Walker and compare it against the Raymarine Log. It gives me damned accurate measurement of distance covered through the water. Given an accurate compass and interpretation of the real heading made good, you can get a pretty accurate fix for 24 hours of run, especially if you know the current. Accuracy degrades drastically beyond 24 hours and/or with strong currents of unknown set. You need dead reckoning to advance your position for getting LOP's from the sun for morning and afternoon shots, as well. Doubt that counting shaft revs would be all that accurate on a yacht, at least one of normal size. A typical yacht just gets tossed around too much with any amount of weather. Of course, counting revs would be useless on a sailboat except under power.


My definition of navigating in the good old days is "I was always lost, it was just a matter of how lost."
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Old 15-02-2011, 14:28   #20
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The Sailor's Lexicon, has it as; Dead Reckoning.
Encyclopedia of Nautical Knowledge, has it as; Dead Reckoning.
Merchant Marine Officers' Handbook, has it as; Dead Reckoning.
Bowditch (Pub no. 9) has it as; Dead Recking
Dutton's Nautical Navigation (USN academy) has it as; Dead Reckoning.
Chapman's Piloting & Seamanship, has it as; Dead Reckoning
Now who is going to question all of those august tomes on Navigation??
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Old 15-02-2011, 14:44   #21
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In the days of yore, The Sailing Masters did a lot of traverse tables as they crossed their track line while tacking. Awareness of ship's speed and course played a lot into it. They even had a peg board to track their course & speeds per watch. Interpeting that peg board must have been fun. About as fun as doing higher math on a abacus instead of a modern caculator. Has anyone used a slide rule lately??
I do my celestial with a modern caculator and enjoy the ease of it.
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Old 15-02-2011, 19:28   #22
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Even though he knew how to get Longitude from Lunars, FWIU they require high level competence in spherical geometry and are arduous and time consuming to calculate.
Not really the tables are available on the Internet and the process is a little more involved then the ordinary hilare method on celestial that's all. The main reason lunars were discontinued is that small observed errors resulted in large position errors.

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Old 15-02-2011, 20:04   #23
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Slocumb would have been the first in the line to buy a GPS if Westmarine had a shop in 1895!
No he wouldn't. He was too poor and too cheap. Even the clock he bought was garbage and eventually lost the minute hand -- and he never replaced it.

The only way he would have had a GPS is if he could have made it himself out of wood.
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Old 15-02-2011, 20:21   #24
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No he wouldn't. He was too poor and too cheap. Even the clock he bought was garbage and eventually lost the minute hand -- and he never replaced it.

The only way he would have had a GPS is if he could have made it himself out of wood.
My hero.... sounds like me with my cork and needle for a compass.....
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