Why do communities have
Speed Limits on the Water?
(Another in the series on Speed)
I was out this weekend sailing with a buddy. He
has a Hunter 33, the wind in the bay was about 10 – 15 knots,
gusting to about 18. The sky had a few Cumulus clouds, that looked
like they had the propensity to become Cumulonimbus later in the
afternoon. But while we were sailing, it was just a classic beautiful
summer day. (For a further discussion on Weather, the University
of Illinois at Urbana-Champaign has an excellent website.
Transiting from his Yacht Club to the open bay, we needed to
transverse some rather shallow areas. Now remember, a sailboat
usually has a much larger draft then a powerboat, and unless it’s
a day sailor, with a keel which can be raised, there isn’t
much leeway in changing that draft.
As we transited one particular shallow and narrow passage, I
noted the 5 mph speed limit posted by our Town. Speed limits are
posted by local governments and states in areas where they feel
for safety or environmental reasons, boaters should go slow. In
this particular passage, both these reasons held true.
The passage way, or at least the navigable passageway was at
best twenty feet across at high tide. The deepest portion was
straight down the channel, with only about a six foot span. At
low tide, our sailboat needs to be right in the middle of that
channel, otherwise we can (and my friend has – one of the
way’s you develop local knowledge) hit bottom.
We’ll come back to this idyllic scene in a while, but first,
let’s talk about your boat’s wake and speed.
Wakes and Speed
There are three major types of Displacement Hulls, Planing Hulls
and Combination Hulls. At low speeds, all three types of hulls
act in the same manner. As you move through the water, the hull
of your boat pushes the water away from itself. Water then moves
out from the bow, in a direction athwartship (at a right angle
to the center line) and abaft (behind). Thus causing the familiar
‘V’ shaped wake we all know and respect.
Generally, the size of a wake is a result of the displacement
(weight) of the vessel, And its speed. The larger the boat; the
larger the wake. The slower the boat (i.e. when a boat is not
on plane); depending on hull configuration and design, the larger
the wake. As a general rule, the larger the wake, the more dangerous
the wake. In addition, wakes of all sizes increase erosion of
the marshland, and provide additional wear and tear on bulkheads.
Our natural resources, our marshlands, are extremely important
to both the local eco-system, as well as to the more regional
eco-system. (For a further discussion, try the National
Wetlands Research Center of the US Geological Survey.
Thus, if we apply the theory that we want to minimize damage
to our environment, and minimize damage to property, we now understand
why localities put into place speed limits.
Now…back to our story
So there we are, traveling by motor, and we’re constrained
by our draft, to the center of this small passageway and all of
a sudden a series of jetski’s and small runabouts come zooming
down the viaduct.
So our tiny ship was tossed, and if not for the courage of the
fearless crew, the East Wind would be lost. (Thanks to “The
Ballad Of Gilligan's Isle” Words And Music By Sherwood Schwartz
And George Wyle for the line, and many years of laughs). But this
is not so far from the truth.
Wakes can push your vessel off its course. Wakes change the water
depth (increase it). Wakes can lift your vessel, since your vessel
floats on top of the water (it’s not a submarine).
One aspect of the law that most people tend to forget is that
you are responsible for the damage caused by your wake. In Georgia,
as in most states, it is illegal to operate your boat recklessly,
as defined by “Causing damage from the wake of your boat”.
Add these two factors, and it was quite possible for our sailboat
to be lifted and pushed to a shallower area of the passageway.
Then we would have been aground for a good six hours, due to no
fault or ourselves.
We were lucky. We made it out of this narrow, shallow channel
without incident, even though our on-the-water neighbor’s
were extremely inconsiderate, as well as lawless. Next time, we
may not be so lucky.
Speed limits are there to protect you, other boaters, and water
users, as well as the environment. Slow down, watch your wake,
and always keep a sharp Lookout (again – ‘s the law).
For more information about
boating safety, why not take a boating course. The United States
Coast Guard Auxiliary offers a large number of boating safety
and navigation courses to the general public. We are also always
looking for people interested in assisting the Coast Guard Auxiliary
in its varied missions. For more info, contact your local United
States Coast Guard unit (www.uscg.mil),
find us on the web at: www.cgaux.org,
or call 1-877-875-6296.