[CQ-Contest] FW: FW: CQWW Survey

Barry Merrill, W5GN w5gn at mxg.com
Tue Mar 19 20:28:31 EDT 2013

My friend Don has won he Chesapeake Bay Governor's Cup overall
in his 38 foot sloop, so I asked him to answer Randy's Question,
has a GPS had inpact on sailing?

His answer:

-----Original Message-----
From: Don  

Absolutely GPS has a big impact on shorter races (depending on what you
think of as "short").

Perhaps the biggest difference is determining whether you are sailing with
the current or against the current.  GPS can show your actual speed over
ground, while a boat's knotmeter shows your speed through the water.  If the
knotmeter has been calibrated to where it is reasonably accurate, you might
notice a difference between the two instruments of more than a knot of boat
speed over the ground (sometimes, the difference will be several knots!).
This difference generally is caused by current.

It is not so easy as knowing the time of day and knowing whether the tide is
ebb or flood, because the effects of current vary based on underwater
barriers.  It is often the case (particularly when the tide is changing)
that the current in one part of a river will be ebbing while only a few
hundred yards way, the current will be flooding.  This effect is most
pronounced around land that extrudes out into the river because the water
can "curl around" a point of land.  But the "land" can be submerged and show
itself only as more shallow versus deeper water, so you cannot use your eyes
to identify these situations.

A GPS also has a "Velocity Made Good" or VMG over ground toward a waypoint
that can be  entered into the GPS.  The VMG would be the effective speed
over ground toward the next mark of the race.  You can quickly tell when you
should tack to get better speed toward the mark, or whether a decision to
tack had been correct, simply by seeing whether the VMG reading increased or
decreased when compared with boat speed from the knotmeter.

Of course, other factors came into play (for example, sometimes you might
tack or not tack because of anticipated different wind conditions) but
sailing with the current, versus against the current, can give a huge
advantage.  Even sailing with a less-adverse current can be very beneficial.

In the days before GPS was routinely onboard a sailboat, "local knowledge" 
was a major factor in sailboat racing.  I can remember racing when some boat
would tack away from the Fleet.  Boats that tacked to follow often ended way
ahead of those of us who continued on course.  This would be due to the of
the skipper who tacked having "local knowledge" telling him that tacking
would get to a more favorable current.  For folks without "local knowledge"
it often was just a game of follow the leader, and not satisfying.  We
always knew that if "Pete" tacked, we had better follow him or he would end
up half-mile ahead of us.  With GPS, there is not so much pressure to follow
the leader based on local knowledge because GPS can show how you are doing
in the current and charts show water depth at various parts of the river.
Note that Pete did not always win, because he might sail out of the
favorable wind.  But with a relatively steady wind over the course, Pete
would win more than his share simply because he knew that a better situation
with regard to current would be obtained by tacking away.

Having written all that, the comments do not apply in short races (say,
total race course is a mile or less, with several legs to the race course).
This is because everyone mostly is sailing in the same current conditions
and other factors (such as skipper and crew skill with helm control and sail
trim) completely overshadow the effects of current.



At 06:08 PM 3/19/2013, you wrote:
>Any truth to this claim?  We have two classes of ham contesting
>"a boy and his radio" or "assisted" which allows the use of all kinds of
>automated spotting of stations, etc.  The analogy is often drawn with
>or sailing with an outboard engine, which led to this statement, which I'd
>think is accurate for long distance events, but is it, and does it have any
>impact on shorter races?
>-----Original Message-----
>From: CQ-Contest [mailto:cq-contest-bounces at contesting.com] On Behalf Of
>Randy Thompson K5ZD
>Sent: Tuesday, March 19, 2013 2:13 PM
>To: cq-contest at contesting.com
>Subject: Re: [CQ-Contest] CQWW Survey
>I bet sailboat racing was a lot different before they had GPS.

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