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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: How Many Chronometers?
From: George Huxtable
Date: 2009 Sep 17, 11:11 +0100
From: George Huxtable
Date: 2009 Sep 17, 11:11 +0100
In [9766], Gary recorded a disagreement with my suggestion that one can do little to protect a sensitive object, such as a crystal oscillator, from environmental changes in ambient temperature, by such means as wrapping it in blankets. I claimed that this could have only a short-term effect, and that the ambient changes would always get through in the end. He wrote- "So I disagree with George to the extent that if the watches are kept in an insulated box, to limit the effect of diurnal changes in cabin temperatures, then the change in rate will only happen based on long term changes in ambient temperature, say on a cruise from the Caribbean to England. But, if the cabin is kept in a range of temperatures which are habitable for humans then the change of rates can be kept to a small number." I recall that as a child, British winters, in a house with only local heating, were made tolerable at night only by using a hot-water-bottle (such aids may be unknown and unnecessary in the USA). And I recall how rapidly such a bottle would lose its heat, though wrapped in blankets with me, so that before very long it was a pleasure to kick it out. I also recall the use of a vacuum "Thermos" flask to keep cups of tea hot, and their failure to do so for more than a very few hours. This in spite of the fact that some pints of water were involved, a substance which has the highest specific-heat of any, which means that it holds more heat, and keeps its temperature, longer than anything else. Gary's crystal oscillator in a blanket, without such heat-ballast, would not keep the outside temperature at bay for long, but with a bottle of water to keep it company, he might increase its thermal time-constant to a few hours; not for days, however. As for his "range of temperatures which are habitable for humans", there might well be different views on that from different societies in different eras. A week ago, I was looking over HMS Cavalier, a World war 2 destroyer built in 1944; the sort of ship that escorted Arctic convoys to Murmansk and Archangel in Northern Russia, Summer and Winter. She was refitted in 1957 and retired in 1974. Yet still, she had a completely open bridge, without windows, and only a dodger to keep the weather off. And I was rather surprised to find, tucked away on that open bridge, sheltered from rain but from nothing else, electronic gear such as a radar display. How, I wonder, would modern American bridge-teams, sheltered from the world in their air-conditioned cocoons, without even an open bridge-wing to walk out on to, have fared under such conditions? Or in the environment accepted by some present-day small-craft sailors, the ones that venture away from tropical trade-wind sailing? The "bridge" got its name from an open lattice structure, that bridged the gap between the top of the paddle-covers, to provide an all-round view. From such a perch, steamers in their thousands were conducted across the North Atlantic, the year round.. In thick weather, a lookout was expected to be stationed at the fo'c'sle head; no shelter provided. These were considered to be habitable conditions then, but I doubt whether Gary would describe them so now. Polar explorers, by the way, would carry sledge chronometers: pocket watches, slung round their necks inside their furs, essential for guiding them back to base along the correct longitude. When Shackleton's Endurance went down in the Antartic ice in 1915, the ship's box-chronometers were abandoned with the ship, and from then on the expedition relied on four such pocket-chronometers. Only one of those remained in working order throughout that remarkable journey from Elephant Island to South Georgia, being essential for Worsley's feat of small-craft navigation. Together with Brad, I'm intrigued by the type of yoga that Gary adopts to enable him to read a chronometer that's duct-taped to his belly. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---