Techno-Talk, July 2006 from BoatUS Magazine
- updated September 2009
always know which way the wind is blowing. Skilled America's Cup
tacticians are renowned for their ability to sense even the slightest
shifts in the wind and to anticipate changes that have not yet reached
the boat. The kids who excel in the junior sailing program at your
boating or yacht club quickly develop an acute feeling for the breeze
and how it can be used to best advantage.
I frequently sail on
the wide-open waters of the Gulf of Mexico and the lower part of
Tampa Bay, areas exposed to wind from all directions. It is not
unusual to see power boats having what is clearly a tough time powering
into the short, steep seas that can very rapidly develop in these
relatively shallow waters. (I have experienced the same conditions
in the Chesapeake Bay and on the Great Lakes, especially on the
very shallow waters of Lake Erie).
Unfortunately the increasingly
popular semi-enclosed fly bridges and air-conditioned wheelhouses
on many powerboats prevent the helmsman from physically sensing
the wind. Secure in a cocoon little different from the environment
in a car, they are isolated from and ignorant of how the wind is
blowing and may accidentally expose their boat and its occupants
to unforeseen and unnecessary risk. These boats should be equipped
with remote reading wind-sensing systems, preferably ones that can
compute and display true wind velocity.
A mariner unaware of
the actual wind condition can expose his vessel to potentially dangerous
situations when altering course after a delightful period of running
in what appears to be light wind and almost flat seas. A boat moving
at 20 knots before a 15-knot breeze is encountering a 5-knot headwind.
The seas appear to be almost flat. The "fun" begins when
a necessary course change puts the breeze on the beam or perhaps
on the bow. If the new course is directly into the wind the helmsman
might attempt to maintain minimum planning speed, perhaps 15 knots.
The 5-knot zephyr is now a 30-knot moderate gale! The once flat
seas are now a nasty chop that has to be pounded into. The passengers
and crew are no longer happy. Slowing the typical planing hull boat
to displacement speed will help, the headwind will be reduced to
perhaps 20-23 knots, however the seas will still be square shaped
and the return trip will take a very long time. The pleasure has
gone from pleasure boating.
There are a number of
solutions to this problem. You can plan all voyages so that they
are dead downwind. However, doing so may not be practical, you might
wind up far from where you want to be. A better choice is to become
as sensitive to and informed about the wind as those guys (sailors)
foolish enough to try to go from one place to another using "free
energy", the wind. (Of course, although the wind is free, the
sails, halyards and sheets needed to use it are NOT!)
A good first step is
to install a set of wind instruments, a wind vane and an anemometer.
The position of the vane relative to the bow and the rotation speed
of the anemometer cups can be shown on a dedicated display on your
instrument panel or presented on your chart plotter. However, the
"raw" information is relative wind data. The only time
the wind speed and direction will be "true" is when the
boat is dead in the water (with no current running). You will need
some additional information and a bit of computational hardware
if you want to know the truth about the wind. Fortunately, the equipment
needed to provide a display of true wind is readily available, often
as part of the autopilot system or the chart plotter.
Some powerboat owners
may be put off by the appearance of sailboat gear, the wind vane
and rotating anemometer cups on their sleek craft. Fortunately some
new technology is available from Airmar (their WeatherStation) and
Maretron. Both of these systems use ultrasonics to determine wind
velocity, have no moving parts and look just like a small GPS antenna.
These systems can measure wind speed, direction, barometric pressure,
temperature, relative humidity, dew point, chill factor and can
determine true wind velocity. Complete information on these two
advanced technology wind sensors can be found at
If you use an iPhone you may find the Wind Meter app useful. It uses the phone's microphone as a sensor, converting the sound created by the air moving across the microphone port into a wind speed reading. Speed can be displayed in feet per second, meters per second, Beaufort Scale, km per hour or knots or miles per hour. Data display can be instantaneous speed or average speed.
By Chuck Husick
Chuck Husick is a pilot, engineer, sailor and former president of
Chris Craft Boats.
© Copyright BoatUS Magazine 2006 (updated Sept. 2009)