NavList:

George wrote:

> Lu asked about the meaning of the word "keld",; thanks to others who
> have replied with definitions.
>
> It's sent me to my own bookshelves, but none of my own dictionaries
> has the word either, so I should have explained it as I used it. Not
> even in Smyth's "Sailor's Word Book", where almost anything nautical
> can be found. My wife has found it in our copy of "A Glossary of Sea
> Terms", by Bradford (1954), as- "Kelds: Smooth patches in the midst of
> ruffled water", which seems to cover it.
>
> It may be of interest to discuss it a bit further.
>
> Most small-boat sailors in and around the English Channel will, I
> expect, be familiar with the term, and with the phenomenon. Many
> others, who sail in waters where currents flow over an uneven bottom,
> will know it too. I associate it with upwelling of water, from below
> the surface, which shows itself as a spreading, still, oily pool,
> roughly circular, in the middle of the waves. Those patches can be 100
> ft. across, or more.

Excellent observations George.

My thoughts, perhaps relevant, perhaps not given the scale:

When running whitewater in rafts and canoes, reading the water is crucial.
One looks for all manner of signs as to what is ahead of them downstream to
set up a safe route.  The signs can be very subtle.

As a gross example related to your question, if the bottom is raised with
current running over it, as in a submerged rock or boulder, it forms what is
called a "pillow."   A pillow is a dome of smooth water running over a rock
or significant high point in an otherwise "choppy" set of rapids.  The
closer to the surface, the higher and smoother the "dome."  At this point
the paddler knows there is a submerged rock ahead, with a high pressure zone
upstream of it and an low pressure zone and eddy immediately downstream from
it.

That can be good or bad.  The water flow around the upstream side of the
pillow can force your bow away from the rock, the depression downstream can
suck your bow in while your stern is being forced away and spin you nose to
tail in a heartbeat if strong enough.

How wide a berth do you need to give the obstruction? That is determined by
looking downstream of the pillow.  If there is a set of diminishing standing
waves, that means deep water behind the pillow, and life is good.  Next to
worst you will do is spin into the eddy and sit there until you do a peel
out when ready to leave. Worst is capsize if you don't shift weight for the
rapid turn (lean upstream).  If no standing waves, don't get sucked into the
eddy--sailing will not be smooth for you. <g>

Simplistically, think of it as a micro dam, with all the associated
hydraulics.

If no current and still present, time to contact the Brit equivalent of the
US EPA.  At nearly $100 US a barrel, there is no need for British Petroleum
to be leaking oil from a pipeline.  Bad for all or us ;-)

Bill





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