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Many
times when we receive a number of emails on a particular
subject we will respond with an article like this
one. In this case, the subject is boat handing in
rough water.
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Battleship New Jersey
in typhoon. The waves don't look like much until
you compare them to the size of the ship. Look
closely and you will see that there are waves
on top of waves so that there is no uniform
wave size. |
A number
of emails addressed the issue of losing control of
the boat while running with the seas. Comments ranged
anywhere from concluding that their boat had a dangerous
defect, to whether they should have bought a catamaran,
to whether they shouldn't be considering some other
type of boat that will handle better.
Questions
such as this point a problem that we've been long
familiar with. That problem is a matter of the lack
of fundamental boating skills among far too many boat
owners. We resist the urge to chuckle at the question
because ultimately this is a serious issue.
Taking a boat out into open water is serious business,
one that requires a comparable degree of knowledge
and skill.
Very often
novice boaters head out on nice, calm sunny days only
to find that conditions suddenly change.
One of
our emails spoke of running down wind in up to six
foot seas in a 30 foot cruiser and encountering the
problem that the boat "for no overt reason would
turn violently into the trough." Clearly
what the writer is describing is what is known as
"broaching," a condition in which a boat
runs down the crest of wave, gathering speed, and
as it meets the backside of the next wave ahead, buries
its bow in that wave. The resistance of the bow hitting
the back side of the wave causes the bow to slew around,
and the boat to veer sharply off course. There's nothing
unusual about that.
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| We
saw it coming but did not run . . . |
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| Our
sturdy Hatteras was built to take it, But
I wouldn't want to test this storm out In
a Silverton. . . . . Know
your own and your boat's limitations.
Smashing into steep four footers in 50
kt winds at 26 kts. is no problem for
this 39' boat. |
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| Whereas
this 50 foot Motor Yacht has
trouble with severe rolling in only three
foot following seas. |
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Typically,
the pilot loses control of the boat, passengers are
thrown around, and this can even result in capsizing.
The problem is not always the design of the boat,
but is often a matter of operator error.
That the writer did not use term "broaching"
was also an indication of his lack of understanding.
Instead, the term "tip over" was used, indicating
the operator's rather appalling lack of experience.
The pilot here was completely unaware that he was
operating the boat at too high a speed for the conditions.
Yet, it's
not merely a matter of speed, but one of the lack
of general seamanship skills. He was unaware that
running with high seas can be just as dangerous
as heading into them. In fact, he seems to be unaware
that taking a 30 foot boat out in 6 foot seas is,
itself, a dangerous proposition.
Many people
come to believe that just because they've been out
in rough water a few times, that they're now "experienced."
Not true. Understanding the effects of wind, waves
and currents is not an easy subject to master. Waves
behave differently under a large variety of different
conditions, so that unless one is familiar with all,
or at least most of these conditions, then one is
not experienced. That's why to get an ocean operator's
license from the USCG requires that an applicant prove
that they have had a large number of hours under such
conditions.
Hull design
has a lot to do with how different boats will handle
under different conditions. The simple fact is that
the vast majority of boats sold today are designed
for creature comforts, not rough water performance.
The number of boats around that have good rough water
capabilities are few and far between. One reason for
this is that people are not willing to give up luxury
and convenience for good handling characteristics.
And so the vast majority of boats are best suited
for protected, not open water operation.
This issue
points up the reason why many people often express
displeasure that this web site doesn't focus more
on "family cruisers" and runabouts, the
sort of boats more suitable use on inland lakes
and rivers. We live and work in an oceanic environment,
so that becomes the focal point for our literature.
We are not inland boaters and know little about inland
boating.
Even the
best of boats won't overcome the lack of knowledge
and seamanship skills. One could easily take a 29'
Blackfin sport fish out in the Gulf Stream and sink
it as a result of inadequate piloting skills. Boats
that are designed for rough water operation will perform
better, but they do not negate the demand for skillful
operation.
Broaching
is a dangerous condition. There are times when wave
conditions will affect any vessel to the point where
running downhill presents the danger of broaching.
The only way to avoid this is to alter course to a
new course where broaching is not a threat.
Once waves
reach a certain height, it becomes necessary for the
operator to match the speed of the vessel with the
speed of the waves, whether he wants to or not. That
means slowing down a lot. One cannot stuff the bow
into the backside of the wave ahead, without risking
the possibility of broaching and loosing control.
If you permit the boat to go zooming off the front
side of the wave, you have to consider the consequences
of what happens when you quickly meet the back side
of the wave ahead.
Would
you drive your car 50 MPH down a road full of foot
deep potholes? The analogy is an appropriate one here.
You'd end up tearing the wheels off the car, losing
control and crashing. When the wind blows, the water
becomes full of potholes. And worse.
Negotiating
inlets
This is
one circumstance where broaching and loosing control
presents an unusually serious threat, for loss of
control can mean crashing into a jetty or going
aground or ashore. Severe tide rips occur when an
outgoing tide meets incoming seas. The result is very
steep waves with a short distance between crests.
But it can also occur at places where promontories
generate strong currents, or even bottom features
below the surface cause unanticipated conditions.
Dangerous conditions that occur without warning, unless,
of course, you have been educated as to how to anticipate
these.
Sure,
having a well designed boat helps, but you've got
to bring yourself up to speed with equally good seamanship
skills. Either that, or risk becoming yet another
story on the evening news.
When
approaching an inlet with a nasty tide rip, it is
best, whenever possible, to approach it as close-in
as the water depths will permit. That means approaching
the channel from the side. The last thing you want
to do is chug through a mile or two of tide rip as
many people are prone to do.
To do
so safely means that you have to know your water depths
outside of the deep channel, and whether or not there
are any obstructions. Once you're into the rip with
nasty following seas behind you, it's a matter of
good seamanship to keep the boat at the right speed
and under control.
Finally,
be wary of crowded inlets under poor conditions. If
there is too much traffic, don't be in a big hurry
to join the fray. Wait until traffic lets up some.
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* * * *
One of
the things that makes boating so very interesting
is that there is so much to be learned. Another is
that it can be dangerous, which, for the adventurous
just adds some spice to the banquet. The socially
oriented recreational boater is unlikely to ever learn
much in the way of seamanship; he owns a boat as an
avenue for recreation, something to do with family
and friends. It's a whole different ball game for
the true boater, for whom boating is a hobby or avocation.
Him we can call the true yachtsman whether he owns
a small outboard or a mega yacht because his real
interest lies in challenging the sea, be it an ocean,
bay or river.
One major
problem that the boat owner has is that most will
never have the opportunity to operate enough different
boats to be able to discern the difference between
a good handling boat and a poor one. The most common
complaint is that a boat rolls too much. More often
than not, this is the perception of the inexperienced.
All boats roll, and in big waves they roll a lot.
If you
are on a boat with a flying bridge, keep in mind that
the higher up you are, the greater the range of motion
will be. It's like sitting on top of a flag pole:
that pole does not have to bend many degrees in the
wind for the pole sitter to experience a violent range
of motion. A person sitting in the cockpit, though
he is experiencing the same number of degrees of roll,
is moving far less because he is sitting at the base
of the radial arm, while the person at the far end
of that radial arm is being flung around violently.
It's not the boat's fault, it's his fault for wanting
to sit up so high.
Seamanship
is the ability acquired by a seaman to pilot his vessel
skillfully under adverse conditions. It's a skill
that involves understanding your boat, wind, waves,
tides, currents and geography. Nowadays, operating
a boat is regarded as little different than driving
a car: just get in and steer the boat around. We see
this casual disregard for the need to acquire any
kind of boating skills whatsoever on every single
weekend at the local marinas where we can observe
dozens of boat owners who have yet to learn even how
to dock their boats with any degree of skill.
Spending
a few hours on Sunday at the local gas dock watching
the antics of unskilled boaters can be some of the
best free entertainment available. But it's a lot
less funny when you happen to be out on the ocean
with one of them. Amazingly, I see this all the time
with "licensed" captains who have been hired
by brokers to operate boats for the day on a survey.
These are often young men who have studied the navigation
books and have passed a test. But books and tests
can't give you hands-on experience, and these young
fellows often have little.
Tide
Rips
This is
so clearly illustrated when they often head straight
out an ocean inlet, directly into a tide rip. A tide
rip is a condition in which the tide is rushing through
a narrow channel against the direction in which the
waves are moving, causing the waves to become taller
and steeper, with less distance between crests. You
do not head directly into a tide rip unless there
is no other way to avoid it. To avoid a tide rip you
have to know your water depths around the inlet. Just
because the channel is marked doesn't always mean
that you have to stay in the channel.
For example,
the Port Everglades inlet at Ft. Lauderdale has adequately
deep water to the south outside the channel. Since
the prevailing winds are east/southeasterly, this
wide deep inlet can produce a very nasty tide rip.
However, it is easily avoided by leaving the market
channel to the south, but very rare is the captain
I see who ever does this. Instead, they subject us
to heavy bashing and plumes of spray for nearly a
mile beyond the jetties.
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| A
deep water inlet with a strong tide rip and
moderate seas can produce conditions like
this. Do you know how to handle it? What would
you do if encountering a situation like this? |
Why do
they do this? Well, because they are not familiar
with this famous inlet, though they will surely tell
you they are. That, you see, is a fundamental
ingredient in this thing called seamanship. It doesn't
begin and end with just boats and waves, but also
understanding how weather and topography affects the
movement of water. Any sailor worth his salt, understands
that the contours of the bottom under the water is
just as important as knowing shorelines and channels.
These are the kind of things that are only taught
in master seamanship courses by those who are truly
master seamen.
Consider
this: It can more comfortable, and safer, cruising
in twelve foot waves than six foot waves (under some,
but not all, circumstances). How can that be? Well,
if you have any understanding of waves at all,
you know that it's not the height of the wave that
is most important, but the distance between waves.
If the distance is very far, as with swells, they
can be very large indeed, but not be threatening or
causing undue discomfort. Yet a steep four foot chop
can be downright dangerous or make your time on the
water miserable.
Waves
are peculiar things. If you've ever taken the time
to actually observe them, you know that the water
making up the wave doesn't actually move in a linear
direction. No, the water in a wave actually moves
in a vertical circle and similar to the way sound
waves move through the air or AC current travels through
a wire: it undulates. It is caused by friction of
the wind on the water surface, obviously. But water
is heavy, and does not want to move. Waves rise up
because of this resistance of the water which is not
pushed around easily.
The point
to understand here is that a single wave can weigh
dozens of tons, usually much more than your boat,
and though water is fluid, it resists the movement
of your boat through it. Good seamanship involves
choosing the best pathway through the waves, even
though that usually doesn't take you in a straight
line to your destination. In going from point A to
point B, you have to decide whether pounding the boat
straight into the waves is preferable to choosing
a more comfortable course.
Sailboats
cannot sail directly into the wind; instead, they
have to tack back and forth at angles in order to
travel upwind. A wise motor boat pilot often does
the same thing rather than subject his boat and passengers
to such abuse. The trick is in figuring out the best
angles relative to wave direction, tides and currents.
When
waves become large enough, like around four feet for
a 30-40 foot boat, all choice in the matter is lost
as the waves determine what direction it is even possible
to travel in. As waves get yet larger, the distance
between crests increases relative to boat length and
it may become easier to navigate.
Sea
State
Sea state
is the term used to indicate, not only wave height,
but is also a description of wave life. As winds are
increasing and building up wave height, as at the
start of a storm, waves will be shorter and steeper.
The shape of waves is determined. in part, by how
long the wind is blowing at a particular speed. Waves
will remain steep as long as wind speed is constant
or increasing, but as soon as the wind slackens, wave
height and duration will begin to decrease. These
waves will be far more comfortable than the waves
while winds are constant.
Currents
The next
most important factor affecting waves is current.
If you ever get the chance to fly over the Gulf Stream,
just look down and you can clearly see the effect
of the northward flow on the pattern of waves. At
each point of the compass, the effect of the current
on the direction of the waves is different. The real
seaman will understand how this affects waves from
all directions.
If the
wind is in the same direction as the current, not
only will wave height be lower, but distance from
crest to crest will increase, making for a more comfortable
ride. While winds directly opposite current will make
waves short and steep, winds perpendicular to the
current will create confused or highly irregular waves
that can be equally dangerous. Here, the current works
to scatter or break up waves. Wave height will be
inconsistent and when winds are very strong, will
create what are called "rogue waves."
If you've
ever seen two wakes of boats traveling in the same
direction come together, then you know exactly what
a rogue wave is: it's two waves coming together at
oblique angles to form a single, yet larger wave.
This is why currents around promontories or sudden
changes in bottom topography can create very dangerous
conditions. Cape Horn, Cape of Good Hope, Cape Hatteras
are all famously dangerous promontories that create
very dangerous conditions because they divide two
large bodies of water that converge. Thus the waves
and currents also converge.
But the
conditions caused by the topography of a Cape Horn
can be just as easily created on a large bay or lake
by a similar topography. Hence boaters can get into
big trouble on the likes of Chesapeake Bay as they
can those other famous trouble spots. All along our
coastlines there are hundreds of spots where wind,
current and land mass shapes can cause sudden and
unexpected dangerous water conditions. The boater
is running along, happy as a clam, in comfortable
conditions, and suddenly he is hit by the unexpected.
"We
were running along and everything was fine. Then,
suddenly we were hit by these huge waves and the boat
leaned over so far that my sister on the bridge fell
and broke several ribs. The sofa in the salon went
from the port side to the starboard side and smashed
the cabinets and paneling. Later we learned that the
batteries broke loose, which is why we lost power
to the radio and couldn't call for help."
Stories
such as that were told to me many times in my insurance
claims work over the years. When I plotted the location
of the mishap on a chart, it usually became very clear
why they ran into trouble. Their description of the
event was all wrong: they were not suddenly hit
by big waves. Oh, no. What they did was pilot
their boat into an area containing big waves. The
potholes in the road did not jump up and hit the car,
the car was driven over the potholes, and had the
driver been looking where he was going he could have
avoided them.
In such
cases the boat operators unknowingly piloted their
boats into dangerous waters around promontories or
confluences of currents which are predictable if you
have the knowledge. In most cases one can plot the
trouble spots on a chart if you know how to read one.
Down
in the Caribbean there are some spots, such
as the Windward and Mona Passages, which are famous
for their dangerous waters. These involve very strong
tidal flows between major islands. So, too, areas
of the lower Chesapeake where all that tidal water
flowing out on an ebbing tide around promontories
can kick up hellacious seas very unexpectedly to the
unknowing, and where hundreds of them get in trouble
every year. All because they are unqualified to be
operating a boat where they were.
There
are times when the trouble spots cannot be avoided,
so that good seamanship calls for making preparations
for entering areas of dangerous waters, as well as
knowing how to pilot the craft through them. Just
because you have a fast boat doesn't mean that you
can escape from trouble quickly. Once you pilot a
boat into troubled waters, you become trapped
by them, and only good seamanship will get you out.
Lacking such skills, you days on Earth may come to
an end.
Bottom
Topography
Probably
one of the least understood and anticipated influences
on wave conditions is bottom topography. Water depth
has a major effect on waves which will behave very
differently between shallow and deep water.
Waves
do not merely affect the surface of a body of water.
The motion involved actually goes down fairly deep,
around four times the height of the waves. So if a
wave is four foot, the water is being disturbed down
to a depth of about sixteen feet.
Thus,
when you have a situation where the bottom suddenly
rises up to near the surface, this can cause nasty
sea conditions. There are excellent examples of this
in the Bahamas where there are actual underwater cliffs
that rise close to the surface.. You can imagine what
happens when a current meets a sheer under water wall
or very steeply rising shelf. It's much the same thing
as the wind flowing around tall buildings. Water moving
against a submerged plateau is going to "hump
up" at that point.
Not only
does the underwater obstruction force a change in
water flow direction, but will cause increases in
velocity and create nasty eddies. These things can
create some of the most dangerous water conditions
there are. Like rapids on a river, only a very skilled
boatman can handle them.
Even
worse is the location where many of these factors
come together, such as a promontory and steep underwater
shelf, along with a forced increase in water flow
and possibly the venturi effect of two headlands coming
together. Such places can be serenely placid at one
moment, and deadly the next as the slack tide or winds
suddenly change.
The foregoing
discussion covers the factors that influence waves.
In Part II we'll discuss boat handling under those
circumstances.
Recommendations
For Novices
If you
are a novice, I recommend that you do several things.
1.
Never rely on GPS electronic maps for your knowledge
of the waters you navigate. There is a good reason
why, the first screen you see when you turn it on,
warns you not to rely on it: it does not contain all
the information you need to navigate safely.
2.
Buy paper charts of the areas that you intend to navigate,
INCLUDING your local area. Learn to read charts and
study them. Memorize the geography of the land and
the topography of the water.
3.
Learn about tidal flows and currents, their direction
and velocity. Know the places that are best avoided.
4.
When encountering rough water, take the time to be
observant of what is happening around you. Use the
opportunity to practice and learn boat handling skills.
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