NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Taffrail log and an alternative
From: Trevor Kenchington
Date: 2002 Jun 22, 10:41 -0300
From: Trevor Kenchington
Date: 2002 Jun 22, 10:41 -0300
Many thanks to Bill Noyce and Arthur Pearson for their suggested solutions to the non-electronic log problem. I'd still like an instrument that would record distance run rather than instantaneous speed, without needing batteries or an LCD. Still, I might have to force myself to compromise on one or the other feature! As to Arthur's suggestion: > For bay crossings in the fog of Maine and Nova Scotia, a simple 30 foot > chip log allows one to measure speed often enough and accurately enough > to keep an accurate DR for several hours. Simply tie a bit of wood > (weighted on one edge to be traditional and to minimize wind drift) on a > length of light line, drop the chip overboard and time the number of > seconds it takes for 30 feet of line to run out. Divide 18 by the > number of seconds to get nautical miles per hour, so 6 seconds indicates > 3 knots. I measure speed and plot a DR every 15 minutes. Any inaccuracy > in speed measurement is less important that whatever allowance one makes > for current and lee way. This is all I have had on dozens of trips > Downeast and back in Maine and combined with a good ear and a good nose > you should be fine (keep the engine off so you can hear surf, gulls, > barking dogs, etc.). Heaving a chip log is an attractive alternative but a bit awkward if single-handed or with a crew that does not share a passion for such eccentricities. If reduced to that level of technology, why not go one step further and use a Dutchman's log? Trevor Kenchington -- Trevor J. Kenchington PhD Gadus@iStar.ca Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 Science Serving the Fisheries http://home.istar.ca/~gadus