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Small Craft
Warnings
Small
craft is a relative term and means ships less than
ships. Because small craft entails so many sizes of
boats, it's up to you to know what sea states are
dangerous to your boat. The authorities are just giving
a general warning to let operators know that conditions
may be dangerous to some boats. If you have a small
outboard, then obviously all small craft warnings
apply to you. No official agency could possibly gather
all the possible differing factors and put them into
something more specific.
The criteria
to use is wind speed and sea state. Twenty knot winds
make for nasty, if not big, seas. Your obligation
is to be sufficiently educated in order to understand
when conditions become a threat. No one can tell you
that because they do not know you, your boat, or your
skills.
Big Seas, Little
Seas
In Part
I we discussed why it is difficult to have a general
discussion about seamanship, and why experience is
so important. Water and waves behave differently
under different circumstances. Smaller waves, say
in the 4-6 foot range are often more dangerous than
larger waves when in open waters. I've made crossings
of the Gulf Stream from Florida to the Bahamas in
8-12 foot seas that were far less threatening and
uncomfortable than 4 footers.
Since
different boats behave differently under differing
circumstances, it is up to the operator to learn how
to become a good seaman, learning about his boat's
strengths and weaknesses. In maritime law there is
an axiom that no boat is seaworthy without a skilled
captain.
No one
is going to learn much without making the effort to
learn. You can try to learn from others, but nothing
is going to take the place of actually being
out there under the kinds of conditions you want to
learn about. That means that you have to challenge yourself
and your boat a bit and test the waters.
The sensible
way to start out is with moderate conditions and circumstances
that are less dangerous. As a young racing sail boat
sailor, I learned rough water seamanship simply by
taking the opportunity to go out when conditions were
bad. I got a big thrill of going out and challenging
the ocean. People thought I was nuts, but what they
didn't realize was that I didn't start out challenging
12 foot seas. Like every other good seaman, I started
at the small end of the scale, but didn't stop once
I'd learned the easy stuff.
Then,
when the big blows came along, I'd round up my crew
and out we'd go into conditions that would make most
boaters hair stand on end. Granted, there is not much
point in doing something like that in a floating motel
room, but if you're a cruising boat owner who is going
to sooner or later get caught in bad conditions, the
best way to learn to deal with them is simply a matter
of practice.
Not only
will you learn about seamanship, but you'll also learn
a lot about boat design, equipment and safety. Who
knows, you might even have fun doing it.
Controlling
Speed
In a power
boat, you have an advantage that sailors don't have.
That is the ability to control your boat speed relative
to wave speed, and along with the direction of travel,
are the two most important factors. Controlling speed
controls the effect a wave will have on a boat. Most
people don't want to slow down when conditions get
rough, but that is an inescapable necessity.
Following
seas are those conditions where the direction of the
waves is anywhere aft of a line drawn through the
beam. When heading straight downwind, with waves heading
exactly in the same direction as your boat, is known
as a following sea. When that direction is
a number of degrees off a line drawn down the center
of your boat, these are called quartering seas.
Seas at an angle off the bow are said to be on the
forward quarter. Seas parallel to the centerline
are called beam seas. Seas directly on the
boat are head seas.
Regardless
of direction, it is necessary to control your boat
speed and choose the one speed at which the boat becomes
most responsive and controllable. Going too fast in
a following sea means that you'll fly off the top
of one wave and bury the bow into the back side of
the next. That's not good, so we need to find the
right speed which yields the most comfortable ride
while still keeping good control of the boat.
When
following seas start to get really big, we have only
two choices: either we slow down to the appropriate
speed, or we have to change direction. If we put the
seas on the aft quarter we can maintain a higher speed
without stuffing the bow into the backside of a wave.
On the other hand, we may not end up going in the
direction we wish. (And here you may have thought
only sailboats engaged in tacking) It then becomes
a matter of whether our higher speed makes up for
the extra distance we have to travel. Often times
it does, making it advantageous to alter course 20-30
degrees.
Broaching
I briefly
touched on the subject of broaching in Part I. Controlling
a broach is a function of controlling boat speed.
It is best to avoid broaches by never running into
the backside of a wave at such a high speed that you
loose control. Once it happens, the only thing you
can do is chop the throttle immediately.
As with
a skid in a car, don't try to steer out of it. It
is best to hold the wheel where it is and let the
slowing speed get you out of it. The danger is in
allowing the boat to suddenly go broadside to the
waves and possibly capsize. Once the bow is no longer
buried in the wave ahead, you can use the rudder and
throttle to quickly right your course.
Big head
seas bring just about any kind of pleasure boat to
a grinding halt. When waves get to around 5-6 feet
and we want to head upwind, we're pretty much stuck
with idle speeds. Unless, you want to try quartering
the head seas and see if that won't get you where
you're going at a higher speed without taking blue
water over the bow. At a 45 degree angle you can increase
speed only slightly. At 60 degrees a bit more, but
makes it tough to get where you want to go.
Tacking
back and forth in this manner certainly is not a prescription
for going anywhere fast, but it can get you there
eventually. That's why the experienced pilot will
try to use lee shores to advantage. If you can use
a course alteration to get in the lee of a shoreline,
you may be able to get to your destination in a round
about fashion without beating your brains out. What
I'm referring to, of course, is finding ways to use
irregular shorelines or islands to your advantage.
Many novice
boaters get themselves in a pickle by heading out
the inlet on a fairly rough day and go charging off
in beams seas only to find that they can't get back
so fast because to return they now have to take seas
on the bow. The moral of this story is don't head
out without considering how you're going to get back.
When
waves get big, the steepness is normally (tides and
currents excepted) a function of whether winds are
steady, increasing or decreasing. As all fishermen
know, just because waves are big doesn't automatically
mean that these are impossible conditions.
Building
winds are most dangerous and those likely to get us
into trouble, for conditions are likely to worsen.
Decreasing or dying winds means that the energy that
causes or creates waves is decreasing and so wave
steepness will decrease and spacing from crest to
crest will increase. Though waves may still be quite
large, they will permit the boat to go at higher speeds.
The seas left over from storms can be very large,
but not necessarily uncomfortable.
I learned
this lesson back in the 1960's when, docked at Bahia
Mar we were waiting for the Stream to calm down before
crossing to Bimini. A cold front had been through
and the wind had blown for nearly a week. Looking
out over the ocean we could see nothing but big lumps
on the horizon. There was big surf along the shoreline.
Well, we waited and waited, and being on vacation,
were seeing it go down the tubes.
Finally,
I said to hell with it, let's just go anyway. It was
pretty nasty along the shoreline, but much to may
amazement, once well out in the Stream we had 12 foot
swells rolling down from the north, but they were
so big that it was like driving a car over rolling
hills. It was a completely comfortable crossing. That
was one of my first lessons that taught me that all
waves are not created equal. The question becomes,
what kind of waves are they? and from what direction?
Arriving on the other side was a different story,
where we couldn't enter the harbor for the huge surf
breaking on the bar, so we went somewhere else instead.
Several
day later in Nassau, for reasons I couldn't fathom,
winds freshened out of the northeast again and kicked
up a nasty chop in the 12-15 waters of the Bahamas
Banks. Now where can we go, I schemed? We can't head
into it toward Abaco, where I wanted to go, but we
could head south to the Exumas, or go visit the mosquitos
and no-see-ums in Andros. Just one problem: If we
got down there, and the wind continued to blow northeast,
as it is prone to do in winter, we wouldn't be able
to get back.
Or could
we? By studying the charts, I could see that it might
be possible to plot a course down the less (western
side) of the Exumas and stay in the lee of the islands.
This was risky because there are nasty rocky shoals
jutting miles out from each of the islands in the
chain so that one cannot follow the lee shores closely.
If you get too far out of the lee, the chop will get
real nasty with the tidal currents between islands.
I decided
to go for it and hope for the best. This proved to
be a mistake. The shoals were worse than they appeared
on the charts. I couldn't get anywhere near the lee
shores of the Examas (since you can't read depths
in real choppy water) and found myself surfing southbound
in a thousand feet of water in the tongue of the ocean.
We were going to end up trapped by sea conditions
and topography and I had no choice but to turn around
and head back. Sometimes you can't win.
Confused Seas
These
are among the worst conditions, and don't necessarily
have to involve large waves to be dangerous or make
life at sea miserable. Confused sea conditions are
best avoided since there is no getting around them
and nothing one can do to make things better. Confused
sea conditions occur as a result of major shifts in
wind direction that occur quickly. This causes waves
coming from differing directions, resulting in waves
that are irregular and unpredictable.
They are
mostly an oceanic phenomenon but do occur on large
lakes or very large bays during or after thunderstorms,
but will die down quickly on smaller bodies of water.
But on oceans, confused seas can last for days after
major fronts or hurricanes. Even large thunderstorms
can have a significant affect on the ocean. Like throwing
a rock in a pond, a storm or front can send out waves
in different directions from the winds that caused
them previously. The waves come together and make
the surface very bumpy.
So called
rogue waves are caused by two waves from differing
directions coming together at oblique (very wide)
angles. Like two boat wakes coming together, the net
effect is to create a yet higher wave, up to two or
more times the height of the originals. These can
be downright dangerous due to their unpredictability.
The best way to deal with them is to stay tied to
the dock.
When caught
out in confused seas, one needs to be particularly
alert for those big ones that suddenly pop up out
of nowhere. With a bit of experience one can come
to anticipate them soon enough in advance to take
evasive action.
We often
hear reports of skippers describing boats "falling
off a wave." They don't mean slamming in the
ordinary sense, which is avoidable. A situation occurs
that is the opposite of a rogue wave; instead of two
waves coming together to make a taller wave. it happens
that undulations from confused seas can create exceptionally
large troughs. The boat hull can be on a hump and
suddenly that hump just disappears out from under
the boat. What happens is that the undulation moves
away, the boat is left with nothing supporting it
and it simply drops. Weird but true.
One can
observe this very clearly on those days when there
are confused swells as opposed to waves. It's very
common in the wake of tropical storms.
Waves on Top
of Waves
This
is another dangerous sea condition. It occurs when
waves get very large, and at a time when when winds
and seas are still building. No pleasure craft should
be out in these conditions.
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