Several Months ago I posted a roughly cut article of mine on Heavy weather
for power boats.  The Article was published in Metal boats Quarterly.  A
rough cut synopsis is included, no illustrations, tables or equations and
little formatting.  If you want a complete copy, let me know and I will
e-mail you one.

Heavy Weather

Definition
What constitutes heavy weather depends on the type and size of boat and
the experience of the crew.  A small sailboat (20 -30 feet) can handle
considerably more heavy weather than a small powerboat.  Large boats (40-65
feet) generally fair better than smaller boats.  Finally, in any given boat,
the weather turns heavy when the winds increase five knots beyond any
previously experienced by the crew.
Best Defense
The best defense against heavy weather is avoidance.  If careful, there
is rarely any need for the skipper of a recreational boat to place the boat
and the crew in jeopardy by operating in inclement weather.  It is much safer
and certainly more enjoyable to spend another day securely in the harbor
waiting for a better weather.  Unfortunately, rarely is not the same as
never.  Even a prudent skipper will get caught in a sudden squall or engage
in a passage longer than the weather predictions are accurate.  On these
occasions, the boat can be subjected to major danger and minor problems.
Major Dangers
The major dangers are pitchpoling (turning end-over-end); broaching
(rolling over sideways); and foundering (taking on large quantities of water
and sinking).  Minor problems concern keeping the crew on board and free of
injury, and handling any minor damage from breaking seas.

Procedure
Disputed Subject
The "best" procedure for weathering a storm is a much disputed subject.
There are only a few tactics available, some, all or none of which may work
at any one given time depending on the boat, the crew and the situation.
The adversaries
To understand and choose the correct evasive action, it is necessary to
have a basic knowledge of the wind and the effects of its force on the boat
and the water.  The wind force acting on the water generates waves and acting
on the boat moves the boat through the water.  The effect on each depends on
the magnitude of the wind force, which is in turn dependent on the velocity
of the wind, and various other variables.
Wind Force
The pressure exerted by the wind increases relative to the square of the
velocity.  A plot of dynamic pressure (q) relative to wind velocity in knots
is shown in Figure 1.  Notice how this pressure increases very slowly below
about 20 knots while above 20 knots the curve becomes steeper with each
incremental change in wind velocity.

Effects on the Boat
Power boaters must overcome this force by engine power making winds much
over ten knots an aggravation if not a problem.  In winds with velocities of
20 knots or less sailboaters use this force as a power source to drive the
boat.  As the wind velocity increases, sailboaters can change a portion of
the area of the boat exposed to this force, the sails, to reduce its effect.
Powerboaters have very little of this luxury and winds over 15 knots become a
problem.  Eventually even the sailboat reaches a point where it cannot reduce
the area exposed to the wind any further and must deal with the danger.
Typical Examples
As stated earlier, there are a great number of variables involved in
determining the exact force applied to a boat by the wind, but it is useful
to examine the range of this force by looking at some typical values.  For a
typical sailboat the hull area is around 100 square feet, for a typical power
boat of the same length the hull area may be three times as much.
Sailboat
In 10 to 12 knots of wind the typical sailboat under full sail is
designed to be driven along at hull speed by approximately 500 to 600 pounds
of wind force.  Any increase in this force overpowers the boat.  As the wind
velocity increases, the sail area is reduced until somewhere between 35 and
45 knots of wind the boat is completely overwhelmed by the wind and is
capable of doing hull speed without any sail up at all.
Powerboat
A typical power boat on the other hand is overwhelmed at a much lower
wind velocity due to its larger hull area.  The force caused by 15 to 25
knots of wind makes handling a power boat difficult.  The conclusion is that
it is very unpleasant for sailboats to experience winds above 40 knots and
power boats to experience winds above 25 knots.  Although, it may be true
that many commercial power boats deal with winds above these values, this
book is only concerned with recreational boating.  Commercial boats are
constructed differently, are generally larger than the average recreational
boat have professional crews and are out for profit not fun.
Boat's Mobility
Another point to consider is that because wind pressure is a function of
the velocity; the boat's mobility can effect this velocity and the resulting
force.  For example, a boat traveling 6 knots into a wind with a true
velocity of 20 knots passed a fixed object will feel an apparent wind
velocity of 26 knots.  It is this apparent wind velocity, not the true wind
velocity, that exerts the force on the boat.  The boat traveling into this
wind experiences a pressure of about 2.25 pounds per square foot while the
same boat traveling at the same speed with the wind feels only 0.66 pounds
per square foot pressure or roughly 3 times less wind pressure.

Wind Effects on the Water
Waves
The effect of the wind's dynamic pressure on the water causes waves.  The
reason that waves form is that as the wind blows, the dynamic pressure of the
wind on the surface of the water moves the surface layer of the water.
Because the water at depth is not moving the surface layer is moved from one
spot and piles up in another where it is unstable and gravity causes it to
collapse.  The forces of gravity and the wind pressure set up a harmonic
motion on the surface called waves.  Since gravity is relatively constant,
the size of the waves depends on the wind forces.
Waves Effects on the Boat
Although the wind pressure on the boat is not to be discounted, once the
wind velocity reaches 50 knots, it is the waves that cause most of the damage
to a boat in a storm.  Waves in a major storm often exceed fifty feet in
height.  Consider the effects of a 50 foot wall of water on a small boat.
The bad news is apparent.  The good news is that waves greater than 8 ft high
shield a major portion of the hull from the force of the wind much of the
time.
General Properties
Fortunately, all fifty foot waves are not walls of water.  They have a
shape that is defined by the height of the wave (H), its length (L).  These
two properties along with the waves velocity (C) are of general interest to
the recreational boater and indicate the proper heavy weather tactic.
These properties are dependent on the wind velocity (V), the duration
that the wind blows (T) and the distance over the water that the wind blows
called the fetch (F).  It is possible to predict a uniform wave shape and
height given these values.  Unfortunately, real waves are not uniform but
look more like Figure 2.

A wave pattern such as this is best analyzed using statistical methods.  

By using such methods a table of useful wave parameters can be developed.  It
is helpful when analyzing or discussing wave theory to introduces the
following concepts;

W   Fully developed state (FDS),
W   Minimum fetch (Fm) to establish a FDS,
W   Minimum wind duration (tm) to establish a FDS,
W   Average wave period (Ta) in a FDS Spectrum,
W   Average wave length (La) in a FDS spectrum,
W   Most frequent probable wave height (Hf),
W   Average height of all waves present (Ha),
W   Average height of the highest 1/3 of the waves (H3),
W   Average height of the highest 1/10 of the waves (H10).

Wave theory
It can be shown that if a constant wind blows over an infinite stretch of
calm water for an infinitely long time, waves will be generated.  The waves
will continue to increase their height and length until a limiting steady
state condition is reached called a fully developed sea (FDS) state.  If the
stretch of calm water is limited by an upwind shore then a limiting steady
state condition will be reached that may be less than a FDS depending on the
relationship between that distance (fetch) and the steady wind.  Therefore,
each steady wind has a minimum fetch (Fm) needed to establish FDS.
Since the waves increase with time, it follows that there exists a
specific minimum length of time (tm) that the steady wind must blow to
produce a FDS.  It can also be seen that because no such thing as a steady
wind exists in nature, a true fully developed sea state never really exists
either.  However this fictitious term is still a very useful concept when
dealing with waves, if you so desire you can alter the meaning of "F" from
fully to fictitious.  In a FDS the minimum time, the minimum fetch the wave
period (Ta), length (La), and various heights as defined above are all
related to the wind velocity.  Table 1 list the various values of those
parameters relative to wind velocity.

Table as a Guide
This table can be used as a guide to the general wave conditions that one
could expect to encounter in any given wind.  For example if a 30 knot wind
has been blowing longer than 23 hours, and the nearest obstruction upwind is
over 275 nautical miles away the average height of the highest 10 percent of
the waves will be 21 feet.  Or in other words, the waves will vary in height
form 9 to 17 feet with an occasional 20 footer rolling through.
Shade Portion
The values given in the shaded portion of the table are only of general
interest since the conditions necessary for the parameters to occur are
extremely difficult to experience.  For example, the possibility of a
constant 60 knot wind blowing for 25 hours over a surface 850 miles long is
remote.  That is not to say that an 84 foot sea is impossible to encounter.
First, this value is only the average of the highest 10 percent, not the
maximum wave height; statistically it is possible to encounter a much larger
wave.  Second, not all waves are built from flat calm water.  A 60 knot wind
blowing across water that already has an established 30 foot sea would
require considerably less time to establish FDS.
Real Waves
In fact, most of the fully developed sea conditions that get the
attention of recreational boaters, get built on already established
conditions.  A five or ten knot wind builds gradually over a period of hours,
typically three to twelve, until the full force of the storm hits.  Then the
maximum wind velocity generally last typically 12 to 24 hours, and gradually
tapers off again.  The result is that the waves are either forming or
decaying for the largest part of the storm.
There are some major differences between a developing, mature and
decaying wave system that are useful to boaters when confronted with heavy
weather.  It is convenient to begin with a mature system then discuss the
developing system and finally say a few words about the decaying system.
Mature Wave System
The mature wave system occurs when all the available wind energy is used
to maintain the wave motion.  This condition occurs at FDS when the wind
velocity and the wave velocity are equal.  At this time the motion of a water
particle in a mature wave is purely circular with no windward translation
relative to surrounding water particles in the wave.  There is of course
windward movement relative to the bottom.  As we have seen earlier when
discussing ocean currents, the velocity of this wind driven current is 3 to 5
percent of the wind velocity.  The center of the rotation is at mid wave
height, as shown in Figure 3.

Sinusoidal
The relative circular particle motion produces a surface shape know as
Sinusoidal wave.  The solid curve is the current position of the sinusoidal
surface.  The dotted curve is the position of the water surface after a small
period of time.  The black dot is the current position of water particle "a
or b."  The open dot is the position of the same water particle after the
change in time.  The small circles describe the total paths of each water
particle.
Surface Current
Because there is no net forward motion of the water, the result of this
orbital flow is that a horizontal surface current is formed on the wave,
first in one direction and then in the other.  The horizontal velocity
reaches a maximum at the crest and in the trough of the wave and is zero at
two points midway down the face of each wave where the particle total
particle velocity is completely vertically, either down or up.  The maximum
velocity (Vo) of this current is dependent on the wave height (H) and period
(T).
Orbital Velocity
Notice that the diameter of the circle is the wave height and therefore
the larger the wave height, the greater the orbital velocity.  This orbital
velocity and its distribution along the wave materially affect a boat's
handling in large waves.  For example a 30 foot wave with a 10 second period
has an orbital velocity of about 5.5 knots at the crest of the wave.

'This condition puts the stern of boat in water that is moving faster than
the water surrounding the bow'
Effects of Orbital velocity on the Boat
The water accelerates from zero to maximum in 1/4 wave length.  In the
example that would be a little greater than 100 feet.  If the boat is moving
at 6 or seven knots when it enters this water it cannot accelerate as fast
and steerage control is reduced as the boat surfs down the wave front.  As
shown in Figure 2.16, on the front side of the wave the orbital velocity of
the water is decreasing from a maximum with the boat to a maximum against the
boat in the trough.  This condition puts the stern of boat in water that is
moving faster than the water surrounding the bow.  The result is a torque on
the boat.  This torque, the increase in speed and the decrease in steering
ability all combine to produce conditions conducive to broaching.  This is
why in a mature system broaching is a real threat.  Actions necessary to
defend against broaching will be discussed later.
Developing Wave System
The developing wave system also poses some threats to boaters.  To
understand this phase of the life of a wave let's start from the very
beginning.  All waves systems at one time or another have developed from flat
calm water.  Before the wind begins to blow the particle of water is
stationary both with respect to the bottom and the surrounding water.  As the
wind strikes the surface it moves the individual particle horizontally
through the water a short distance in the direction of the wind and
eventually the drag from the water below draws the particle down into the
water.  Then the particle is submerged and rotates through a spiral and
returns again to the surface and repeats the motion.  As shown in Figure 4a.

Cycloidal Wave
The younger the wave the greater the proportion of the horizontal
movement.  The spiral starts out rather flat and then develops a more
circular shape.  As the force of the wind continues to work on the water, the
excess energy increases the rotary motion until finally the mature rotary
state described above is reached.  As the wave height grows the particle
motion is much harder to analyze than in a mature sinusoidal wave but it is
apparent that the water moves faster in the crest of the wave than in the
trough.  This condition produces a water surface that is shaped into sharp
peaks as shown in Figure 4b, and is called a Cycloidal wave.
Breaking Waves
Eventually, the transverse motion of the particle begins to cause the
crest to travel faster than the wave itself.  When this happens the water is
flung forward ahead of the crest, the crest disintegrates and the wave
breaks.  This first manifests itself on the water surface as white caps.
Early on, these small breaking waves are of no consequence to the
recreational boater.  As the wave height increases, this situation changes
and larger breaking waves become a major danger to survival.  The force of
the water in a large breaking wave can be as much as one ton per square foot.
Considering the average recreational boat presents a couple of hundred
square feet of surface area to the wave, 400,000 pounds of force is
unleashed.  Forces of this magnitude can crush hulls, break out ports and
hatches or hurl the boat through the air.  The possibility of encountering
large breaking waves during heavy weather tends to interest most boaters.
Steepness
The ease at which a wave breaks has to do with the steepness of the
forward face of the wave, which is in turn dependent on the wave's age,
general shape, height and length.  When a portion of the wave front exceeds
about 30 degrees, the wave will break.  This angle is difficult to measure in
the real world.  What is easy to measure is the wave height and length.
Using these two parameters the steepness of a wave can be expressed by the
steepness ratio.  The steepness ratio (SR), is the ratio of the wave height
(H) divided by the wave length (L).
Steepness Ratio
The steepness ratio of a fully developed sinusoidal wave is about 1 to 15
or 0.067.  Because of this waves shape with a round top, the forward surface
of the wave is much flatter than a cycloidal wave.  To obtain the required 30
degree angle to cause a sinusoidal wave to break the SR needs to be about 1
to 5.  The cycloidal wave on the other hand has a very steep wave front and
therefore tends to break more easily.  The SR of a breaking cycloidal wave is
normally around 1:7.    Most of the breaking waves occur during the
development of the system when it is around 40 percent mature or the wave
velocity is about 40 percent of the wind velocity.
Estimating Maturity
The velocity of a deep water wave (C) is related to the period (T) and
the wave length (L).

It is much easier at sea to measure wave period than estimate wave length.
Therefore Equation 5 is probably more useful.  By timing the number of
seconds and multiplying by three the boater can get the wave velocity.
Comparing this with the wind velocity will give an idea of the maturity of
the storm and the character of the waves to be encountered.
Decaying System
In a decaying wave system the water particle motion remains circular and
so the shape of the wave remains sinusoidal as the storm dies.  First, if
there is enough energy in the wind to maintain the system, the wave height
remains the same but the wave length continues to increase, thus the SR
approaches 1:30.  Under these conditions there are fewer breaking waves but
the distribution of the wave height tends toward larger waves because time
allows the probability of wave patterns combining to produce extremely large
waves.  The large long waves have correspondingly large lengths of wave front
where the wave current is traveling with the boat.  If the water and the boat
are moving at the same rate the rudder force is lost and with it the ability
to steer the boat and broaching again becomes a problem.  It this situation
where the waves are long and the possibility of plunging into the forward
wave front is minimized, it is best to run fast and free in front of a very
large wave to keep positive flow by the rudder.  Finally as the wind velocity
continues to drop, there is not enough energy available to maintain the wave
height and the wave height drops along with the increase in wave length.
Waves in Shallow Water
So far the discussion has been about waves in deep water, but the
recreational boater when crossing a bar also occasional encounters waves
influenced by current and shallow water.  In a mature FDS, the orbital
diameter decreases with depth to 0.04 of the wave height at a depth equal to
the wave length.  Although, this circle is small, it is large enough so that
a wave passing through water that is shallower than 1/2 the wave length
begins to feel the bottom noticeably.  The circular orbits of the water
particles tend to flatten into ellipses and the speed of the wave decreases,
while the period remains constant.  Because the speed of the wave (C) is
related to the period (T) and the wave length (L) by Equation 7, the wave
length must also decrease.

Waves in Current
As the length decreases, the steepness ratio increases because the wave
height remains constant.  When the steepness ration approaches 1:7, the wave
becomes unstable and breaks.  Current running against the wind and into the
wave also slows the velocity of the wave with similar circumstances.  A
current running with the waves increases the wave speed and reverses the same
process flattening the waves.  Large waves in shallow water running against a
foul current can be very dangerous causing very steep, violent breaking waves
that can easily overwhelm a recreational boat and on occasion even a large
commercial vessel.

Preparation for Heavy Weather
Many times all that one can do when dealing with extreme weather is to
prepare the boat and crew and take what comes.  The amount of preparation
depends on the boat, the crew, the skipper and the severity of the oncoming
storm.
Information
First, get all information on the approaching storm that is available on
the radio or using techniques described in Chapter Eight on Weather.  Try to
determine the wind strength and direction and the duration of the storm.
Write the barometer reading and the time in the log and update the reading
every hour.
Fix position
Next fix the boat's position on the chart, locate the nearest safe harbor
and calculate a run time to the harbor.  Also, locate the nearest lee shore,
estimate the severity of the wind and the amount the boat will drift down
wind.  Note the locations of shallow water or adverse currents.  Using this
information, decide whether the boat should run for protection, sea room or
continue on course.  In making the decision to run for cover the skipper
needs to judge the conditions that the boat will encounter at the harbor
entrance.  See the section on 'Crossing the Bar' at the end of this chapter.
Prepare the Crew
The crew should prepare by putting on the proper warm and waterproof
clothing.  Prepare quick snacks.  High energy foods like candy and a thermos
or two of hot soup are needed to keep the crew efficient.  Any drugs needed
to suppress seasickness symptoms should be taken early enough to become
effective.  Seasickness in a storm is not only a discomfort, it is dangerous
because it reduces the strength of the crew when strength is needed for
survival.  Handling a boat in a storm is exhausting work. In many instances,
even though the boat has weathered the storm, the crew has perished due to
exhaustion from cold, hunger and exposure.  A tired brain makes bad
decisions.
Safety Harnesses
Safety harnesses should be worn by any crew on deck.  In a storm-tossed
sea without help nearby any individual lost overboard is lost, if they cannot
be recovered within a couple of minutes.  The possibility of being recovered
without a life line is minimal.  Sailboats often run a line fore and aft
along the deck to which a safety harness can be attached.  Power boaters are
very seldom as well rigged or even equipped with safety harnesses.  Although
most power boat crews may expect to spend most of their time in the shelter
of the cabin, if a crew member needs to go forward to rig a sea anchor or
make emergency repairs, they need to be tied off.
The most dangerous time for the crew is immediately after exiting the
cabin.  Emerging from the relative calm of the cabin into all the motion and
fury is startling.  Once on deck the individual can adjust to the force of
the wind, the flying spray and brace against any oncoming seas.  If a wave
hits before they make the adjustment there is a good chance they will lose
their balance.
Life Jackets
Life jackets are debatable.  Unfortunately the conditions where a life
vest will actually saved a life are limited.  If the water is cold, the life
expectancy can be a matter of minutes.  The extra bulk of a life vest makes
working more exhausting as well as awkward.  It is entirely possible than
wearing a life preserver will reduce the chances of survival by tiring the
crew unnecessarily or upsetting their balance and pitching them overboard.
These two objections do not apply to passengers or once the loss of the ship
becomes unavoidable.
Survival Suits
Survival suits will preserve life for an extended time even in cold water
but they are also impossible to work in.  If they are available, they should
be positioned where they can be distributed quickly in case the ship needs to
be abandoned.  Any other survival gear like extra water and food for the life
raft should also be moved to an accessible location.
Prepare Emergency Equipment
Emergency equipment like flares, EPRIBS and the first aid kit should be
located and moved to accessible, secure positions.  Those rarely used pieces
of equipment like drogues, sea anchors, warps, cable cutters, and panels to
cover the windows need to be located and positioned before the sea conditions
makes rummaging around in the lower reaches of the vessel uncomfortable.  All
large windows not needed for navigation should be covered early.
Secure Equipment
The properly dressed and tethered crew should secure all equipment on
deck.  Everything that can be stowed below should be stowed in lockers.
Equipment that must be left on deck should be lashed tightly.  The force of
wind and waves in the center of a severe storm is hard to imagine.  Shock
cord is woefully inadequate.  Larger items should be attached with extra
lashings.
All equipment below should likewise be stowed and secured.  All locker
hatches should be secured both above and below decks.  Those above deck, if
they come open, will lose their contents into the sea and take in water.
Those below will empty their contents into the cabin.  Heavy flying objects
are a hazard to your health.  Getting hit in the head with a flying one pound
can of tomatoes will do more than get your attention.
Securing Hull Openings
Secure ports, cowls and hatches as it becomes necessary.  Stale air in
the cabin can add to seasickness keep as much ventilation as possible without
endangering the safety of the vessel.  Large quantities of water can get
below through these openings and jeopardize the safety of the vessel.  Check
the bilge for excess water and debris, clean and pump if necessary.  Check
the bilge pump intake screen to see that it is not clogged.  Close all
through hulls.  An overturned boat will remain floating as long as air
remains inside the boat.  Closing the through hulls will prevent air from
leaking out of the cabin.
Hang On
Once preparations are complete there is very little left to do except
hang on solve problems as they arise and persevere.  Better times will come,
even though that may not seem possible during the din and confusion, which is
unbelievable and difficult to imagine without the questionable benefit of
experience.

Power Boats
A power boat in heavy weather is vulnerable because the high freeboard
exposes a large surface area to the force of the wind and seas.  Most power
boats also have large windows, which if broken can allow large quantities of
water below.  Exposed to heavy weather, the powerboat's options are limited,
to running for cover, defensive course selection, or station keeping.
Running for Cover
A power boat's main defense, especially the smaller boats, is speed and
vigilance.  The probability of successfully riding out a severe storm at sea
is considerably less for a small power boat than a small sailboat.  The
sooner a storm can be predicted the better chance the boat has to make it to
safety.  Boat speed places a limitation on how far a small power boat can
prudently get from sheltered conditions.  In setting this limit the skipper
should be aware that a boat that can do 20 knots in flat water cannot do 20
knots once wind generated waves are present, especially if the course is into
those waves.
Forced Speed Reduction
As the wind rise, a boat heading into the wind will have to reduce its
speed or change its course to prevent pounding.  If the waves are short and
steep the screws may come out of the water as well.  Changing course so that
the boat is running 45 degrees into the weather extends the boat's path on
the wave and reduces the pounding.  This course is very uncomfortable due to
the part roll and part pitch motion of the boat and lengthens the run for
cover.  Turning the boat down wind reduces the apparent wind on the boat by
the speed of the boat and the motion is more comfortable.  Down wind is the
best direction to run for cover.
Beam Seas
If the desired course of the boat places it beam to the seas, it may
become necessary for the power boat to tack towards its destination, running
first 45 degrees into the wind then 135 degrees off the wind.  It should be
pointed out that the most vulnerable position for a boat in severe conditions
is beam on to the wind and seas.
Defensive Course Selection
If it becomes necessary to ride out a storm in a powerboat, the major
decision is whether to run into the waves or with them.  Each skipper must
judge the storm conditions and the behavior of the boat in choosing which
course they think is best.  The question of whether to run into or away from
the storm is hotly contested and I am sure depends on the individual vessel,
storm and skipper.  The right choice early in the storm with steep short seas
may be different later in the same storm when the seas lengthen and flatten.
Downwind
Running downwind away from the storm, decreases the velocity of the wind
by the speed of the boat and increases the length of the waves which in turn
reduces the forces the boat and crew must resist.  For example, it is
possible for a power boat going twelve knots to run with a six or seven foot
wave using the two knot orbital current on the crest to keep them on a single
wave.  This is not necessarily as good an idea as it sounds; because the boat
will tend to surf down the wave front.  When surfing, the water and the boat
are moving at the same speed, helm control is reduced and the tendency to
broach is increased.  It is better to lose a little distance on the wave and
regain helm control.
Sea State
In this manner, it may be possible to handle very large seas
successfully, especially early in a storm when the waves are moving slower or
late in the storm when the seas are sinusoidal in shape and the slope of the
wave is more gentle.  The general guidelines are that in short steep seas it
is best to slow the boat down and let the waves run under the boat.  If the
waves are high and long, hold as much speed as possible and run away from
them.
Pitchpoling & Broaching
Running downwind the skipper should be mindful of the increased chance of
pitchpoling, broaching or being pooped by a following sea, especially early
in a storm.  The seas are cycloidal in the early stages of a storm and their
steep faces and sharp crests can cause considerable trouble.  Negotiating
short, steep seas safely requires the boat speed to be carefully controlled.
The speed needs to be slow enough so the bow does not plunge into the trough
or wave ahead causing the boat to be flipped by the wave coming from behind,
yet fast enough to maintain steerage control and avoid broaching or being
pooped by a following sea.  Slowing a power boat running downwind may not be
an easy task.  The wind force on the superstructure alone will drive it at
surprisingly high speeds.  Towing warps to slow a power boat should be
avoided.  Any lines strung out behind a power boat may become fouled on the
prop with disastrous consequences.
Boat Control
If the skipper cannot control the speed of the boat it may be best to
take the more uncomfortable but safer course and power into the wind.  This
presents the bow, which is better designed to take the force of the storm, to
the elements.  If the seas are sinusoidal, control of the boat is seldom a
problem and running directly into the seas produces a fairly smooth up and
down motion around the long axis of the boat.  If the seas are cycloidal,
heading into the wind requires the boat speed to be progressively reduced as
the conditions get worse.  Eventually the boat may be moving so slowly that
it is barely keeping steerage.  This is called station keeping.
Station Keeping
Station keeping is very similar to hoving to with a sailboat.  Enough
power is maintained to keep the boat heading between 50 degrees off and
directly into the wind.  Just slightly off the wind is generally a little
more comfortable where the motion is mostly pitch.  The more off the wind the
more power that can be applied, but the greater the danger of being caught by
a gust and forcibly turned sideways to the wind and waves.  In this position
the boat is very susceptible to broaching.
Drogues and Sea Anchors
Holding the head into the wind by using a drogue, sea anchor or trailing
warps off the bow may or may not work.  The experience of sailboats using
this method is poor.  Certainly the sea anchor will keep the head into the
seas and places the bow in a position to split the waves.  However, the boat
can no longer be powered forward with the engine or it will over run the
lines.  This is not a method to consider in a powerboat unless no other
options are available
Trailing Warps
If warps or sea anchors are to be set it is best to attach them using a
harness that is attached just aft of amidships rather than to the bow.  Heavy
loads on the bow will tend to depress it and increase the possibility of
taking green water over the bow.  The lines need to be protected from chafe
and long enough to reach several wave lengths ahead of the boat.  The amount
of drag is important, the object is to slow and stabilize the boat not stop
it.  Too much drag will stop the boat and subject it to the full force of the
breaking waves.  The boat must be allowed to fall back with the wave so that
the immense force of the wave will be dissipated and less damage will occur.
This necessary backward movement places abnormal loads on the rudder and may
damage it.
Changing Tactics
Changing course or removing warps in mid storm is difficult.  Recovering
any warps in the midst of a storm is practically impossible and if it becomes
necessary will probably require the warps to be cut loose.  Radical course
changes that require the vessel to pass beam to the weather are difficult and
dangerous, especially if the crest of a wave hits the boat while it is beam
to the weather.  Try to make any turns beam to the weather on the back side
of waves.  It may not be possible to time the maneuver so that the boat can
turn a full 180 degrees before the crest of the next wave hits.  The exposure
can be reduced by breaking the turn into two segments.  First, turn the boat
45 or 50 degrees off the wind and hold this course until a suitable sea
approaches.  Then, as the crest passes, make the remaining portion of the
turn.

Don Dodds
Bird of Time
NPR

G'day again. While we're waiting for LENNY to pass over us a thought struck
me.
What is the wind pressure on 700 sq ft perpendicular to the forecasted 120
kt sustained wind, gusting to 140+ kts? Can someone figure that out? I don't
think I have enough docklines deployed :-( Maybe there aren't enough
docklines on the planet!

My marina took in a new 75' Azumit. Roughly 1300 sq ft and also will be
broadside to the breeze.

Last year in Hurricane Georgs(no relationship to the listmister) we had big
seas(15-18 feet) just outside the marina. The breakwater did a pretty good
job of keeping the surge down so the boats only had the wind to contend
with. In this storm the forecast is for 18 to ?? ft coming right into the
entrance. So we will have lots of surge which wears the docklines no matter
how much chafe gear is installed.

More drama to follow from a bad day in Paradise.
Wet and winderly yours!

Dave & Nancy
Swan Song
Northsea 58'
Tortola, BVI