NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Chip log
From: Rick Emerson
Date: 1998 Nov 15, 08:42 EST
From: Rick Emerson
Date: 1998 Nov 15, 08:42 EST
Bob responded to a question I posed on the list about traverse boards and whether anyone still uses one. The description of a chip log is a pretty good one. Rick S/V One With The Wind, Baba 35 ------- start of forwarded message (RFC 934 encapsulation) ------- [...] From: bob-norris@XXX.XXX To: rick@XXX.XXX Cc: live-aboard@XXX.XXX Subject: Re: Chip log Date: Sat, 14 Nov 1998 21:02:23 -0500 Hi, Rick -- I think you asked about details on a chip log during the thread on traverse boards. I lost your address, and was waiting for you to chime in again. I remembered Baba 35. Consulting my old Sea Scout manual, I find that it's a quadrant of wood, weighted on the rounded side so it will float vertically, rounded side down. A bridle, about 6' long in total, connects the lower corners, and a tapered wooden plug is seized to the middle of it. The main length of the log line is connected to a hole in the peak, and about 3' along it is seized a wooden socket that fits the tapered plug. With the plug in the socket, the chip sits upright, and when streamed stays virtually still in the water as the ship moves on. When the timing is finished, a tug on the log line pulls the plug out of the socket, the chip flips, going nearly horizontal, and is easily retrieved. Quoting: "The log line is small stuff, similar to the lead line, loosely laid flexible untarred hemp being the best. "(The line) is got on a stretch, wetted, and marked as follows: The log line should be at least 150 fathoms long. Fifteen fathoms from the chip is a piece of red bunting. This marks the end of the stray line, the line allowed to run over while the chip gets settled comfortably in the water. "From this piece of bunting distances are marked off every 47' 3" by a piece of fish line seized between the strands of the log line. Each division from the red bunting is marked by knots in the fish line, one, two, three, etc. [Ergo, "knots" -- Bob] These main divisions of the line are each further subdivided into 5 equal parts by bits of white bunting, indicating each 2/10 of a knot. Single tenths are arrived at by estimation. "The line, being marked, is wound on a large reel with handles. "The other instrument, and a very important one, is the log glass, and old-fashioned sand glass filled and regulated at the chronometer, to run out in 28 seconds. "Then we have the proportion...: Twenty-eight seconds is to one hour, as 47 feet, 3 inches is to one knot; or 6,080 feet (the sea mile, or length of an average minute of arc on a meridian of the earth." So: 28 sec. / 3600 sec. = 47.25 feet / 6080 feet = 1 knot (run out when the log glass empties) The more feet run out, the more knots and white buntings show up, and obviously the faster you're going. When your helper calls "mark" as the sand stops, grab the log line and count the knots and tenths. If the plug hasn't pulled out yet, yank the line and reel it in. Actually, get your apprentice to reel it in while you go put the peg in the traverse board. Executive Privilege, you know, deserved by your Superior Knowledge (which keeps you out of Situations that demand your Superior Skill, etc.). Hope this diverted your mind from contemplating the sorry state of the world for a little bit :) You might forward this to the Navigation list. I don't know the address. BoB-) S/V "High Hopes" - -- "Gentlemen never sail to weather." BoB-) S/V "High Hopes" [...] ------- end ------- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-= =-= TO UNSUBSCRIBE, send this message to majordomo@XXX.XXX: =-= =-= navigation =-= =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=