SEAMANSHIP CH. 6 HEAVY WEATHER The reading material for this lesson will be found in CHAPMAN; SEAMANSHIP, Boat handling under adverse conditions in the CHAPTER ON SPECIAL SEAMANSHIP TECHNIQUES AND Text in your student study guide.

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SEAMANSHIP CH. 6 HEAVY WEATHERThe reading
material for this lesson will be found in
CHAPMAN SEAMANSHIP, Boat handling under adverse
conditions in the CHAPTER ON SPECIAL SEAMANSHIP
TECHNIQUES ANDText in your student study guide.
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Unless you are experienced in HEAVY WEATHER and
know exactly what you are going to do..
The best advice for someone going out in a boat
in HEAVY WEATHER is.DONT! If you are caught
out, or feel you have to go, this chapter has
some useful pointers for you.
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WIND WAVES

• Nearly all waves are caused by the wind blowing
  over the surface of the water fresh or salt
• The longer and the stronger the wind blows, the
  higher the waves.
• When the wind blows from the same direction for
  an extended period of time, the waves will tend
  to run in that same direction.
• NOTE WIND directions are given as FROM where
  it is coming.
• All other directions are given as where it is
  going to
• Example Wind comes from the south. Seas will
  run to the north.

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NON-WIND WAVES

• THERE ARE TWO KINDS OF NON-WIND WAVES
• SEISMIC Produced by internal shock waves below
  the earths surface. (EARTHQUAKE)
• TIDAL Produced by internal shock waves within
  the ocean floor, which are MOVING waves and
  attain incredible heights. (Also caused by
  Earthquakes)

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CLASSIC or IDEAL WAVE
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PARTS OF THE WAVE

1. A vertical cross-section looks like a normal sine
   wave
2. The crest is the TOP of the wave.
3. The TROUGH or TROF is the bottom of the wave
4. The HEIGHT is measured from the TROF to the CREST
5. ONE WAVELENGTH is defined as the horizontal
   distance from one crest to the next crest.

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WAVE PARTS (CONTD)

• The SLOPE or STEEPNESS of the wave is measured
  from the CREST to the TROF, in a straight line.
• Putting numbers to the wave picture allows us to
  talk about the significant features of the
  wave(s).

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WAVE HEIGHT

1. The greater the height, the more unstable it
   tends to become (ready to break).
2. Large waves tend to move somewhat slower
3. Height is academic. Remember, a 5 ft. wave is
   almost over your head when you are standing up in
   the boat!
4. Wave heights are notoriously over-estimated.
5. Waves over 3 ft. become troublesome and over 5ft.
   become difficult for small boats and their
   operators to safely and properly handle.

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WAVE HEIGHT WARNINGS
Wave heights of 4-6 ft. or higher usually will be
warned for in a SMALL CRAFT ADVISORY (SCA) issued
by the NATIONAL WEATHER SERVICE, NOAA.
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Weather and Crew Fatigue
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WAVE VITAL STATISTICS

1. The PERIOD becomes extremely useful and important
   to the boater because this is the wave speed, in
   TIME.
2. If you know the WAVE PERIOD , it is possible to
   make significant heading changes or even come
   about without seriously endangering your vessel
   or crew.
3. Knowing the wave period will significantly help
   you judge your approach speed to a dock or
   another vessel or to a person in the water
   awaiting rescue.

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SURF

1. Surf is caused by breaking waves which became
   unstable due to the rising up of the floor of the
   water body.
2. Friction with the bottom causes the wave bottom
   to move slower than the wave top. This makes the
   wave lean into the direction of motion.
3. It doesnt take much of a lean before the wave
   can no longer hold itself together and the top
   crashes ahead of the bottom.
4. This breaking can occur anywhere the physics
   are present but the actual beach or reef is where
   we see it most plain.
5. On the open sea, breaking waves are common with
   wind speeds above 30 kts.

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WAKES

1. Wakes (waves) caused by another boat, can be a
   definite hazard to your vessel and vice-versa!
2. BOW WAKES The wake generated by the bow of the
   vessel. It tends to remain on the forward portion
   of the hull and care should be taken not to
   generate a LARGE wake here. They can be damaging
   to other vessels.
3. STERN WAKES By far, the most dangerous to other
   vessels. Attention must be paid to the stern
   wakes of other vessels, especially those of
   meeting and passing vessels in close quarters and
   close to shallow water or a beach.
4. SOLUTION REDUCE SPEED IMMEDIATELY.

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BOW STERN WAKES
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EFFECT OF WIND

1. The more water you draw, the greater your hull
   and keel will resist the side forces of the wind
   and the less sideways motion you will have due to
   the wind pushing your boat.
2. The less hull you have in the water, the greater
   the effect of the wind and resulting sideways
   motion or LEEWAY, especially at low hull speeds.
3. The more cabin structure and freeboard you
   have, the greater the LEEWAY (side motion from
   the wind).
4. Sideway motion is known as LEEWAY( a skidding
   motion of the hull)
5. LEEWAY should be watched and overcome at all
   times, unless you count on it for maneuvering
   purposes.

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DRAFT LEEWAY

1. A, having a deeper draft has more resistance to
   LEEWAY (side-way motion) than B.
2. However, because A has more of the hull exposed
   to the water than B, A will be more adversely
   affected by CURRENT.

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EFFECT OF CURRENT

1. Much more will be said about current in a later
   course.
2. Current can be effective both with the wind and
   against it.
3. While currents may be wind driven they usually
   are deep within the water and their effect is
   independent of the wind.
4. A deep-draft vessel will receive the greatest
   effect from the current because the current has
   that much more of the vessel to act on.
5. Minimizing the effect of the current requires
   lining the hull up WITH the direction of the
   current flow, much as with the effect of the
   wind.
6. Often times, wind and current will produce a
   tricky, even dangerous safety situation for
   steerage and special caution is required.

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WIND CABIN PROFILES
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LEEWAY EFFECT

1. Vessel A, with its large superstructure of
   exposed hull and freeboard makes an ideal surface
   for the wind to push against and shove the hull
   off to one side( the LEE or downwind side).
2. Vessel A would be a much more difficult vessel
   to steer, at low hull speeds.
3. Vessel B has much less exposure to the wind
   with a much lower profile and that much less wind
   resistance and leeway.
4. Vessel B would be a much easier vessel to steer
   with much less leeway, at low hull speeds.

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EFFECT OF WIND ON HULL PROFILES

1. In the previous slide, it is easy to visualize
   the reason for the increased effect of the wind
   on hull A, due to the amount of surface area
   the wind has to work against.
2. It is also easy to see that the low-profile open
   boat will have much less wind effect due to the
   lesser amount of surface for the wind to interact
   with.
3. Vessels with large profile areas such as A,
   sometimes become difficult to control in small,
   tight, maneuvering areas such as docking and
   getting in and out of a slip. Houseboats have a
   very large sail area.

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MINIMIZING EFFECT OF WIND

1. To achieve the minimum effect of wind on the
   boat, it is necessary to face the bow INTO the
   wind.
2. The more the bow drifts away from the wind ( next
   slide ) the GREATER the effect of the wind on the
   vessels heading and the greater the difficulty
   of steerage ( maintaining a desired heading)
3. Minimizing the effect of the wind takes PRACTICE
   PRACTICE PRACTICE under variable loads,
   headings and hull speeds. It is a matter of
   finesseand an integral part of the SEAMANS
   EYE.

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WIND AND YOUR BOAT
A. At the TOP Minimum effect. B. Moving
down-scale, wind effect increases on the hull. C.
Finally, at the bottom, wind effect is at a
maximum (broadside).
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HEAVY WEATHER TACTICS

1. When wind and seas are becoming more and more
   difficult to manage, it is time to employ some
   different tactics.
2. Left to drift, power boats tend to face their
   sterns INTO the wind. This is NOT good.
3. When wind and seas are HIGH, control of the
   vessels heading may not be possible.
4. One of the best solutions to maintaining the
   boats heading in rough seas, high winds, or when
   adrift, is the use of a SEA ANCHOR

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THE SEA ANCHOR(DROGUE)
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THE SEA ANCHOR

1. A simple device which captures water and holds it
   or slows its flow through it, thus slowing down
   the drift speed of the hull, when it is deployed.
2. It also helps to check the yaw, producing more
   stable headings.
3. When deployed from the bow, it is called an
   anchor.
4. When deployed from the stern, it is called a
   drogue.
5. SEA ANCHORS are extremely effective, if they have
   been adapted to your vessels specifications.
6. Several different types of sea anchors follows

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PARACHUTE SEA ANCHOR
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SAIL TYPE SEA ANCHOR
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JURY RIG SEA ANCHORS
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JURY RIGS

1. Jury rigging is the art of making something for a
   specific purpose, out of anything you can find to
   do the job.
2. In a time of need, sea anchors can be fashioned (
   jury rigged ) out of almost anything that you
   can get to suspend itself reasonably close to the
   surface of the water right on top is better.
3. Anything that can reasonably capture water,
   thereby slowing the motion of the boat, will
   work.
4. The more water it can catch and hold, the more
   effective.
5. Usually, there are plastic buckets, tarps, sail
   cloth, canvas remnants, pieces of sheet plastic
   or similar items you can fashion a sea anchor out
   of, Including a hatch cover or door. Any length
   of rope to attach it, will work.

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DEPLOYING A DROGUE FOLLOWING SEAS
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DEPLOYING THE SEA ANCHOR
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WHERE YOU DONT WANT TO BE

• The following two slides focus attention on two
  situations where you NEVER WANT TO BE
• The BROACH and
• A PITCHPOLE
• Good seamanship practices, a SEAMANS EYE and a
  continuing alertness and understanding of the
  effects of the impending weather situation on
  your vessel, can prevent such a situation.

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LITTLE OR NO RECOVERYFROM THE BROACH
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PITCHPOLINGABOUT AS BAD AS IT GETS
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REVIEW QUESTIONS NO. 1

• The time it takes two wave crests to pass the
  same point is known as the___________
• a. scan
• b. second trip
• c. period
• d. span

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REVIEW QUESTIONS

• The time it takes two wave crests to pass the
  same point is known as the _______________
• c. period.

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REVIEW QUESTIONS NO. 2
2. The uninterrupted expanse of water over which
the wind blows is called the _______ a.
stretch b. fetch c. path d. trof
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REVIEW QUESTIONS NO.
2. The uninterrupted expanse of water over which
the wind blows is called the _______ b.
fetch
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REVIEW QUESTIONS NO. 3
3. A sea anchor___________ a. is a heavy anchor
for use in open water b. is highly effective
regardless of method or skill employed in
its use. c. is usually cone-shaped of canvas
or other cloth material and prevents
excessive yawing when properly
deployed. d. is easily handled.
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REVIEW QUESTIONS NO. 3
3. A sea anchor _________________ c. is
usually cone-shaped of canvas or other
cloth material and prevents excessive
yawing when properly deployed.
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REVIEW QUESTIONS NO. 4
4. The angular measure from the trough to the
crest of the wave is the____ a. pitch b.
slope c. spill d. swell
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REVIEW QUESTIONS
4. The angular measure from the trough to the
crest of the wave is the _______ b. slope
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REVIEW QUESTIONS NO. 5
5. Nearly all waves are caused by______ a.
cycloidal action b. the wind blowing across the
surface c. earthquakes d. swell over changing
bottom conditions
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REVIEW QUESTIONS NO.
5. Nearly all waves are caused by__________ b.
wind blowing over the surface
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REVIEW QUESTIONS NO. 6
6. If forced to operate a power boat in heavy
seas, _____ a. alter course to run in the
trough or the waves where the sea is
calm. b. alter course to run just ahead of the
crest of a very high wave since waves are
always spaced farthest apart there. c. alter
course to run broadside to wind and waves since
rolling motion is more comfortable than
pitching motion d. slow speed and alter course
to run into wind and waves at approximately
45 degree angles.
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REVIEW QUESTIONS
6. If forced to operate a power boat in heavy
seas_______ d. slow speed and alter course to
run into the wind and waves at approximately 45
degree angles.
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REVIEW QUESTIONS NO. 7
7. A warp is____________ a. used in place of a
drogue b. used when running abeam of the
seas c. streamed from the bow d. usually made
of heavy planking so that it will float.
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REVIEW QUESTIONS
7. A warp is ______________ a. used in place
of a drogue
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REVIEW QUESTIONS NO. 8
8. Running with high seas abeam is most likely to
cause a vessel to____ a. hog b. jibe c.
pitchpole d. broach
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REVIEW QUESTIONS
8. Running with seas abeam is most likely to
cause a vessel to_____ d. broach
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REVIEW QUESTIONS NO. 9
9. Of the waves caused by boats, which is the
most dangerous? a. Bow wave b. Beam wave c.
Mid-ship wave d. Stern wave
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REVIEW QUESTIONS
9. Of the waves caused by boats, which is the
most dangerous? d. Stern wave
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REVIEW QUESTIONS NO. 10
10. When you have too much weight aft, your
vessel will tend to____ a. roll b. slew c.
yaw d. pitch
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REVIEW QUESTIONS
10. With too much weight aft, your vessel will
tend to_______ c. yaw
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END CHAPTER 6