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For years I sailed with the Hurricane Island Outward Bound School in
Maine.  In countless trips up and down the coast in 30' open
sailing/rowing boats, we measured speed by timing a "chip" from bow to
stern and dividing the seconds into 18.  Using a lobster pot yielded
speed over the ground.  Using a small stick gave speed through the
water. 6 seconds for the 30' from bow to stern indicated 3 knots. We
crossed a lot of bays in the fog with nothing more accurate than that
and hundreds of crews over many years did just fine finding the other
side. I now sail a Drascombe Longboat and the only improvement I have
made is to keep a 30' piece of string tied to small piece of wood so I
always have my "chip".  Still works fine.

-----Original Message-----
From: Navigation Mailing List
[mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Noyce, Bill
Sent: Tuesday, June 10, 2003 3:47 PM
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Re: Logs

> 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.
>
> Is there a description somewhere that would tell me how to duplicate
such a
> log?

It sounds to me as if you have all you need to know.  A few more
details:
the "chip" is often a semicircle, with the round part down, and some
lead
attached to the low point to help keep it mostly submerged and upright.
There are three attachment points: two form the bridle, and the third is
a peg.  The three help keep the chip perpendicular to the line, and the
peg pulls out when the line is "nipped", so it can be reeled in more
easily.

The exact time for your sandglass isn't critical, but the spacing of the
knots has to be made to match.  I believe the classic sandglass was 28
seconds.  Leave some blank line so the chip can get settled and out of
the
vessel's wake, then insert a starting mark (at which the man controlling
the line would shout, "Turn!"), and space the knots at 6080*t/3600 feet,
to measure nautical miles (6080 ft) per hour based on feet traveled in t
seconds. (Hope I got the formula right.)

        -- Bill

   

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