NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Traverse board and the log.
From: tony
Date: 2005 Dec 2, 18:43 +0000
From: tony
Date: 2005 Dec 2, 18:43 +0000
About eight times, I believe, and certainly after any major change of course. on 2/12/05 11:39 am, George Huxtable at george@HUXTABLE.U-NET.COM wrote: > Any ideas about this question? > > In the days of streaming the log, how many times, in a watch of four hours, > would it normally be streamed? Details follow. > > =============================== > > Thanks to all the Nav-l members who have provided such helpful responses to > my request for a drawing of a traverse-board, both on-list and off it. > > Renee Mattie has helpfully written- > >> There is a very clear jpg of a line drawing of a traverse board at >> http://www.rootsweb.com/~mosmd/travbrd.htm >> As this is an educational website, the author may be willing to allow you >> to >> reuse it in your publication, and even to make modifications. >> >> It would be easy to remove the text at the top and/or to add column >> headings >> for the knot-log pegs at the bottom. >> Presumably, the column headings should be I through XI and 1/4, 1/2, 3/4 >> as >> shown in the photo at http://www.californian.org/ebay/htm/traverse.htm >> (Or left blank as in >> http://www.maritime-museum.aland.fi/current/g/pinkom_l.jpg ) >> >> >> It wouldn't even be all that difficult, using available drawings and >> photos >> as a reference, to draw one from scratch. > > ========================= > > > Renee, and others, have pointed to the useful and interesting website of > Duane A Cline, at- > http://www.rootsweb.com/~mosmd/travbrd.htm > > You can go to that site to see his drawing, and his text. The text is also > copied below. > > ==========================(quote from Cline) > ========================== > > Navigation: The Traverse Board > The Traverse Board was used as a memory aid by navigators as early as the > seventeenth century, and would certainly have been used by the officers and > crew on the Mayflower. With this simple device they were able to record how > far and in what direction they had traveled during each four-hour watch. > > It consisted of a simple wooden board, equipped with pegs which were > inserted into a series of holes. > > The upper portion of the board was marked out in the thirty-two points of > the compass. Notice there are a series of 8 holes radiating out from the > center to each of the thirty-two points of the compass on the outer circle. > A set of eight pegs is attached to the center of this circle. > > > > > USING THE TRAVERSE BOARD > > > > > At the end of each half-hour of the watch, the officer on duty would take a > peg and stick it into the hole in the compass bearing on which the ship had > run during the half-hour just completed. > > The first half-hour of the watch was represented by the first circle of > holes nearest the center of the compass, and so on. At the end of the > four-hour watch all of the pegs would have been used, with the last peg > inserted in the outermost circle of holes. > > To record the speed at which the ship had been traveling, the rows of holes > at the bottom of the board were used. At the center of this row of holes was > another set of eight pegs on strings. The holes to the left side of the > center were used for the first two hours of the watch, while those on the > right side were used for the last two hours. > > At the end of the first half-hour of the watch, the officer in charge would > insert a peg at the hole which represented the knots-per-hour at which the > ship had been traveling. [Remember that this was determined by using the > log-line.] If the ship had been traveling at four knots-per-hour, the > officer would count over from left to right on the first row of holes and > place the first peg in the fourth hole. > > At the end of the four-hour watch, the officer in charge would transfer this > information from the traverse board onto a slate -- or perhaps a piece of > paper. At the end of the day the master or captain of the ship would use > this information to write up his log, which was a detailed record of the > voyage. The navigator would use the same information to chart the progress > of the voyage on his maps. > > Traverse Boards provided a simple and relatively foolproof method of > recording information which could be used even the foulest weather. > > It is interesting to note that the use of the traverse board was adopted by > the navigators from northern Europe and England and was used as late as the > beginning of the twentieth century. No examples of traverse boards from the > Mediterranean navigators has ever been found. > > ========================== (end of quote from Cline) > ========================== > > There's no problem, to my mind, in the upper, dartboard-like, part of the > picture, of 32 "spokes", each containing 8 holes. Clearly, that refers to 8 > successive observations of vessel's course, at half-hour intervals, to the > nearest compass-point. They could be entered in an order, inner-to-outer, as > Cline suggests, or the opposite. It wouldn't matter, as long as it was > agreed. > > But the difficulty that worries me arises with the 4 rows of "speed" holes, > below the dartboard, where Cline suggests - > "To record the speed at which the ship had been traveling, the rows of holes > at the bottom of the board were used. At the center of this row of holes was > another set of eight pegs on strings. The holes to the left side of the > center were used for the first two hours of the watch, while those on the > right side were used for the last two hours." > > That would indeed allow for 8 speeds to be recorded during the 4-hour watch, > at half-hour intervals, one speed for each pegged course. However, I suggest > that the evidence of preserved traverse boards shows that many (perhaps all) > were not intended to be used in that way, but instead for four speeds to be > measured over the watch, one for each row of pegs at intervals of an hour. > And not in two separate blocks of four, to the left and to the right, as > Cline has suggested.. > > That question may be have been somewhat confused by overpainting and > redecorating of the boards over the years, as a result of on-board > weathering from the harsh environment, or from the well-meaning attentions > of collectors or museum curators. > > Cline's model for his drawing may be, at a guess, the board illustrated in > "The Haven-seeking Art", by E G R Taylor, (my ed. is 1971) plate X11 ("found > in the Isle of Barra, 1844"). At least, the decorative key-shape at the top > corresponds closely to his. The bundle of 8 strings emerges from between two > columns, To its left, there are 10 columns, which have been marked 1 to 10. > To its right, the columns have been marked, starting again at 1. But there > are only 9 columns to the right, so they are marked 1 to 9. It makes little > sense, to me, for the board to be designed to mark speeds to 10 knots over > the first half of the watch, then speeds up to 9 knots over the second half. > And that's one difficulty; how do you split a speed block into two equal > parts, when it comprises an odd number of columns, as is commonly the case? > > So I doubt whether that example was intended to record 8 speeds in two > blocks, but suggest instead 4 speeds, each given a single row, right across > the board. > > But if the speed-block had been designed to record only 4 speeds, why did it > need a bundle of 8 pegs? Well, that's made clear in certain traverse boards, > which show, at the right, either a single column marked 1/2, or a set of 3 > columns marked 1/4, 1/2, 3/4. By pushing one peg into a whole-knots hole, > and another into a fractional-knots hole, the precise speed can be noted. > > So the illustration in the Taylor book could well have been intended to > record 4 speeds in a watch, using its 19 pegs to show a maximum of 16 3/4 > knots, to the nearest quarter-knot, using if necessary 2 pegs for each row. > > That may seem an unreasonably high speed to allow for. For a steamer, that > might be the case, but the American clipper ships were claiming ultimate > speeds of around 20 knots (see David MacGregor, "Fast Sailing Ships", 1973, > page 190). With a good wind from the right direction, they were the fastest > things afloat, by a long way. > > The scale on the speedometer of my car reads to 140 miles per hour, though I > couldn't (illegally) get the thing above 100, downhill and downwind, try as > I might. In a similar way, a mariner wouldn't wish to be limited by the > speed-range of his traverse board! > > How often, then, would a sailing vessel stream the log? Lecky, in > "Wrinkles", in the late 1900s, dealing with steamship matters to a great > extent, only expected the log to be streamed at 2-hour intervals. But steam > vessels were not so subject to the caprice of the wind, and log readings > might have been required more often, for sailing vessels. Perhaps every > hour, but 8 times in a watch (every half-hour) seems to be overdoing it > somewhat. It seems to me likely, to fit in with evidence from traverse > boards, that an hourly log reading would be noted on the board, in > association with a pair of courses. > > Does anyone have views, or even better, evidence, as to how often the log > would be streamed, and exactly how it would be pegged-up on the board? > > I now have an email address for Duane Cline, so I will send him a copy of > this mailing. > > > > George > > =============== > > contact George Huxtable at george@huxtable.u-net.com > or at +44 1865 820222 (from UK, 01865 820222) > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.