Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Logs
    From: George Huxtable
    Date: 2003 Jun 11, 00:29 +0100

    Vic Fraenckel asked-
    
    >As anyone who has read Patrick O'Brien's Aubrey/Maturin novels knows, the
    >use of a log line is often mentioned. It is essentially a board with a
    >bridle and a long knotted line on a reel. I surmise that the bridle was used
    >to keep the face of the board perpindicular to the water flow in order to
    >maximize the drag on the log. It was the midshipman of the watch to use the
    >log to ascertain the speed of the vessel at periodic intervals. I am sure I
    >am not telling members of this list anything they do not know! I would like
    >to duplicate this speed log for my own sailboat. I understand that the log
    >was tossed overboard and a 30 second sandglass was turned. The board pulled
    >the knotted line off the reel and the mid counted the knots that passed thru
    >his fingers during the 30 second interval. He then nipped the line which
    >caused the board to become more streamlined (parallel to the flow)  in the
    >water and the line was reeled in. The number of knots counted equalled the
    >speed.
    
    Response from George-
    
    Yes, Vic, you have it right. Some additional details follow.
    
    What you're referring to is a "chip log", or sometimes "ship log". The
    board is sometimes referred to as a "log ship". It's usually triangular,
    and one edge is usually lead loaded so the thing just floats, with that
    edge down, and a corner up, at the end of the three-leg bridle. The lower
    legs of the bridle are usually firmly fixed to the board, but the upper one
    is just held to the board by a pushed-in wooden peg. Between the bridle and
    the first of the knots is a length of "stray line" intended to be long
    enough so that the board is out of the disturbed wake close behind the
    vessel before measuring starts, when the message goes out to turn the
    glass.
    
    The line is coiled on a reel which spins very freely about a horizontal
    spindle, held over his head and gripped between the hands of a seaman who
    has to keep his feet firmly planted apart on the afterdeck, because he has
    no "one hand for himself". The line runs between the fingers of an officer
    or midshipman, who counts the knots as they pass. The sand-glass (finely
    crushed eggshells were better than sand) was chosen to be 28 or 30 seconds,
    but there was always much confusion about suitable combinations of
    knot-spacing and time. Faster vessels might have a 15-second glass, and
    closer knots, to minimise the length of line required. At night, the glass
    had to be viewed in the light from the binnacle lamp and the hand watching
    it had to shout out when time was up.
    
    Even if the vessel was travelling fast, there was little tension on the log
    line, as long as it could run out freely. When counting knots stopped, the
    line was given a tug, which was enough to pull out the wooden peg, and the
    board would flip over to be horizontal and become easy to pull back.
    
    The earliest reference to such a log that I know of is in Matthew Bourne,
    "A regiment for the sea", 1580 (ed. Eve Taylor, Hakluyt Society, 1963). In
    place of a sand glass, Bourne proposes measuring time by reciting a form of
    words that has the right duration (a religious catechism, or a bawdy poem,
    I wonder which?). The length run out would be measured in arm-spans as it
    was gathered back in, an arm-span being nearly a fathom.
    
    There's a picture of a chip-log in Paasch's Illustrated Marine Dictionary
    of 1885, (originally "from keel to truck"), reprinted in Conway classics
    1997. Also in "A glossary of sea terms", Gershom Bradford, Cassell 1954,
    where he states that on one occasion the clipper "Flying Cloud", off Cape
    Horn, once ran out 18 knots, "and there was still a little sand in the
    glass". I've heard a story of one of the china-tea clippers, at high speed,
    where the log line reached its end and yanked overboard the Chinese seaman
    holding it overhead, from his insecure posture. At that speed, there was no
    question of going back to pick him up, especially a Chinese, who were
    regarded as of little worth in those days. The speed was reported to the
    "old man" as "sixteen knots and a Chinaman, sir".
    
    George.
    
    ================================================================
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ================================================================
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site