- Contributors (In alphabetical order) - David L. Green, P.E., Senior Consultant Robert D. Horsefield, P.E., Chief Naval Architect (Editor) Jonathan G. Parrott, P.E., Director of Engineering Craig A. Pomeroy, P.E.
This
information has been produced as a courtesy to the fishing industry and
is free to all. Distribution by others requires that the copyright
shown above is clearly shown on all copies. Additional copies are also
available from Jensen Maritime Consultants, but a nominal fee will be
charged for large orders to cover reproduction. Republication must have
the prior written consent of Jensen Maritime Consultants, Inc..
Commercial
fishing is one of the most dangerous occupations with over ninety
deaths each year. While statistics vary from year to year, the numbers
from 1996 remain typical - one hundred thirty six (136) U.S.
fishing vessels were lost. Of this total, 45 were in some way
"stability related", and nine of these vessels accounted for 19 lives
lost.
According to the U.S Department of Health and Human Services publication "Commercial Fishing Fatalities in Alaska"
(September 1997), "an average of 34 fishing vessels and 24 lives are
lost in the commercial fishing industry" each year in Alaskan waters. "This represents an occupational fatality rate of 140 per 100,000 per year, 20 times the national average."
It is important to understand the term "stability related". At least 75% - 80% of "stability related" sinkings
are caused by either overloading, or flooding through deteriorated
systems or boundaries, non-tight closures, or other openings added for
operational convenience. These events impair or invalidate the designed
stability characteristics of an otherwise seaworthy vessel. The
remaining vessel losses are for unknown reasons, as there were no
survivors, and combinations of weather, icing, or initial loading can
be suspected but not clearly defined.
Obsolete
stability guidance is another factor with the potential to increase
stability-related risks. All vessels experience weight growth over
time, and a good rule of thumb is to have a naval
architect review stability every five years, or when vessel
modifications are made. Undocumented changes are especially dangerous
since the vessel crew may not be aware that the stability guidance is
obsolete. Modifications affecting stability include any weight changes,
watertight bulkhead alterations, tank boundary changes, fishing method
changes, freeing port alterations, lifting gear changes, windage changes, ventilation terminal changes, bilge keel area changes, and repowering.
While
the risks are high, so can be the profits. The fisherman must weigh the
risks of his occupation against the benefits. Many losses result from
deferring maintenance of watertight & weathertight
closures, or the lure of potential profit overcoming common sense, such
as pulling an overloaded net on deck, or returning to port with holds
plugged and fish on deck.
B. History of Stability Criteria
United States
fishing vessel casualties are consistent with worldwide experience. In
view of the staggering casualty statistics, stability criteria have
been developed which have proved to significantly reduce the incidence
of casualties when used properly. Up until the late 1960's, there were
very few criteria available to the Naval Architect for judging a
vessel's stability. In 1968, a United Nations study committee, called
the Intergovernmental Maritime Consultative Organization (IMCO),
published a recommendation for intact stability for fishing vessels.
This recommendation was based on a statistical study of fishing boat
casualties worldwide, and quickly became the accepted standard (now
called the IMO standard).
The current arsenal of stability criterias
go far beyond the original IMO standard. The Naval Architect can now
determine the effect of wind & waves, lifting devices, towing nets,
water on deck, etc.. The revolution in the
computer industry has made stability analysis much faster and more
detailed, with some programs simple enough to be used by the Master on
board his own boat. Stability criteria are continuing to develop as
more data is added to the pool of knowledge each year. It is important
to understand, however, that no stability criteria can make up for poor
seamanship or improper loading. The Master is still the one that
decides whether it is safe to pull up that last net, or stack that next
tier of pots.
C. Responsibilities of the Master
The
Master is responsible at all times to ensure the stability and safety
of his vessel. A qualified Naval Architect can supply him with the
necessary information to accurately determine the stability of his
vessel under normal operating conditions. He can also supply a method
of determining stability under unusual circumstances. He cannot,
however, stand over the Master's shoulder and force him to follow the
stability recommendations. The Master must understand basic stability
concepts, be familiar with his stability booklet, and use every means
at his disposal to ensure that the stability of his vessel is adequate
to meet the sea and weather conditions encountered. It is also
paramount that the Master ensure that proper vessel maintenance and
repair is carried out, including maintaining the hull and systems
watertight & weathertight consistent with the stability criteria.
A. Discussion of Righting Arms & Metacentric Height
In
common terminology, a stiff boat (with at quick roll) has high initial
(upright) stability. A vessel with a slow roll generally has lower
initial stability. It must be remembered that initial stability has
little bearing on the ability of a vessel to right itself at larger
heel angles. A very stiff boat may have poor stability at high heel
angles, while a boat with low initial stability may have excellent
stability at the higher heel angles.
Righting
arms are a measure of reserve buoyancy, or how much watertight
structure is available to provide buoyancy above the waterline. As a
vessel heels to one side, the center of buoyancy shifts outboard in the
direction of the heel. The horizontal distance from the center of
gravity (G) outboard to a vertical line through the center of buoyancy
(B) is the righting arm (GZ) (see figure 1). As the vessel continues to
heel the righting arm will increase until the deck edge immerses.
Heeling further past this point, the center of buoyancy stops shifting
outboard, and the vertical line through the center of buoyancy becomes
closer to the center of gravity reducing the righting arm. Eventually
the center of buoyancy and the center of gravity will line up and the
righting arm becomes zero. The area under the righting arm curve up to
a given angle is a measure of the energy required to heel the vessel up
to that angle. The area from a given angle to the angle of zero
righting arm is the vessel's reserve
buoyancy. The maximum peak of the righting arm curve represents the
maximum return-to-center force the vessel can exert.
As
shown in figure 1, the intersection of the vertical line through the
center of buoyancy (B) and the centerline of the boat is called the metacenter (M). Since the metacenter shifts with heel angle, the term metacentric height "GM" (the distance from G to M) is defined only at very small heel angles. Hence the metacentric height is only a measure of the initial stability of a vessel.
B. Available Criteria
The stability criterias
currently available are based on stability in calm water with
sufficient safety margins to cover the dynamic conditions of heavy
seas. Over time, this has proved to be a successful approach. Very few
vessels that meet the two basic criterias described below are lost due to stability problems.
The most widely applied stability criteria in use today is Torremolino's criteria, which sets forth minimum values for the initial metacentric height (GM) and the righting arm (GZ) curve for a vessel (ref 46 CFR 28.570):
1. GM at least 1.15 ft 2. GZ max at least 0.656 feet at 30 degrees or greater heel 3. Area 0 - 30 degrees at least 10.34 ft-deg 4.Area 0 - 40 degrees (or flooding angle) at least 16.92 ft-deg 5. Area 30 - 40 degrees (or flooding angle) at least 5.64 ft-deg 6. Angle at GZ peak = 25 degrees or greater. 7. Range of positive GZ =60 degrees or greater.
An alternate criteria originally developed for offshore supply vessels is also widely used (ref 46 CFR 170.173c). This criteria is useful for vessels that have difficulty meeting Torremolinocriterias 6 & 7:
1. GM at least 1.15 ft 2. Area 0 - Peak at least 10.34+0.187*(30-Peak Angle) 3. Area 0 - 40 degrees (or flooding angle) at least 16.92 ft-deg 4. Area 30 - 40 degrees (or flooding angle) at least 5.64 ft-deg 5. Angle at GZ peak = 15 - 30 degrees 6. Range of positive GZ = 50 degrees or greater.
M = Metacenter
K = Keel
G = Center of Gravity
GZ = Righting Arm
B = Center of Buoyancy
GM = Metacentric Height
Figure 1
In addition to one of these basic criterias, others are applied which take into account service conditions:
"Severe
Wind and Rolling" (SWR) criteria subjects the vessel to a blast of
wind, and limits the vessel to 14 degrees of induced heel and specified
righting energy ratios (ref 46 CFR 28.575).
"Wind Heel" criteria places minimum limits on the metacentric height (GM) based on wind profile area (ref 46 CFR 170.170).
Vessels involved in towing should meet the "Towline Pull" criteria which places minimum limits on the metacentric height (GM) based on power, freeboard, towline height above propellers, etc. (ref 46 CFR 173.095).
Vessels
engaged in crane lifting operations at sea should meet "Lifting"
criteria which limits the resulting heel to 10 degrees and the area
between the righting arm and heeling arm to a minimum of 15 ft-deg up
to a specified angle (ref 46 CFR 28.545 & 173.005).
Vessels with large open decks which ship high volumes of water should meet "Water on Deck" criteria (ref 46 CFR 28.565).
C. Selection of Criteria
For United States
flag vessels, existing government regulations apply to vessels 79 ft
and over in length. In October 1992, proposed regulations for vessels
less than 79 feet in length were published for public comment. Due to
the large number of comments received, the final regulations are
currently being re-written by the U.S. Coast Guard.
Your Naval Architect should select the appropriate criterias
based upon vessel size and service to ensure compliance with effective
regulations, as well as fundamental safety considerations.
D. Flooding & Watertight Integrity
As
shown in section B above, the righting arm curve (GZ) is assumed to
terminate when flooding occurs through open vents, unchecked tank airpipes, etc..
Such openings can significantly restrict the vessel's operation and
carrying capacity. Your Naval Architect may recommend modifications to
openings, such as adding manual or automatic closures to increase the
usable righting energy.
It
is extremely important to maintain reserve buoyancy above the main
deck, because it creates the forces that right the vessel at higher
roll angles. When rolling in a seaway, an open porthole, vent, or door
can allow water to enter on each roll. A vessel may capsize if too much
water enters, either by excessive free surface, or loss of freeboard.
A
stability test is a scientific experiment designed to gather the data
required to determine the weight and center of gravity of a vessel. As
such the vessel operator must set aside dedicated time to conduct the
experiment when no work is being done and no crew is on board.
Your
Naval Architect will require certain technical information prior to the
test. This includes an Arrangement Drawing and a Lines Plan. If a lines
plan is not available, the boat must be hauled out of the water and
measured.
You
will also need to supply a set of incline weights (usually concrete
blocks) and a crane to move them. The weights should be weighed on a
certified scale prior to the test. Your Naval Architect will tell you
how much weight you will need. Incline weights are available from most
shipyards, or "ecology blocks" may be purchased from concrete suppliers
at minimal cost. Since concrete blocks absorb rain water, they should
be covered between the weighing and the stability test.
During
an incline test, long pendulums are read which accurately measure the
heel angle caused by the movement of the incline weights. Adverse
weather conditions may be cause for postponement of the test since wind
& waves may make pendulum reading impossible. Icing is also cause
for postponement since the ice buildup will increase the weight and
raise the vessel's center of gravity. If ice is present, it must be
removed prior to the test.
On vessels with chines, the chine should be immersed at the transom during the test. This is because the waterplane changes dramatically with small heel angles on boats with fairly flat bottoms aft. This change in the waterplane may throw off the results and require a re-test.
The
vessel must be free to move during the experiment. There must be
adequate water depth to ensure that the boat does not come aground. If
there are tides in the area where the test is to be conducted, the
incline may need to be scheduled during high tide. No other boats
should be rafted to the boat being tested, and all mooring lines should
be loose.
All
large or wide tanks should be either completely empty or completely
full. Small narrow tanks may be slack. Any cross connected tank pairs
should have the cross connect closed. Sea water holds should be empty.
Your Naval Architect will consult with you in advance of the test to
determine what the tankage should be
during the test. For Load Line incline tests, all tanks must have a
visual means of verifying the liquid level, either by having the tank
manholes off, using sight glasses, or overflowing the tank vent. Tankage should be arranged such that trim is minimized and list less than 1/2 degree.
Any
gear and equipment which does not belong with the boat should be
removed or weighed. Foodstuffs, pots & pans, ship's books, charts,
linens, spare parts, fishing gear, crew's effects, etc. which are part
of a vessel's normal inventory may remain on board, but will need to be
weighed if they are out of position. For Load Line stability tests, all
weight except inventoried engine spares, life saving gear, dishes &
galley equipment, and ship's books & charts must be accounted for
either by removal or weighing.
Bilge
water should be minimal (bilges should be dry for Load Line stability
tests). If this is a problem they should be sucked out prior to the
test.
Pendulums
are usually hung in one or more holds, usually in the locations that
give the longest pendulum lengths. Your Naval Architect will tell you
where. The hatch covers need to be removed in those locations. You will
need to supply two lengths of lumber (2 x 4s) long enough to span the
hatch at each pendulum position.
B. Running the Test
There are nine basic steps that your Naval Architect will perform during the test:
1. Skipper Conference - Discussion of vessel condition (tanks & deadweight) and operation (fuel burnoff sequence, hold loading sequence, fishing equipment, etc.)
2.
Pendulum Setup - Pendulums will be set up in positions that are
sheltered from the wind and yield the longest pendulum lengths. This is
normally in holds with the pendulums suspended from one or more deck
levels above. A board is typically placed across a hatch opening from
which the pendulums are hung. In the hold bottom a marking board is
placed transversely on sawhorses. The pendulum bobs are weighted X
shaped vanes that are submerged in buckets of water or oil for motion
damping. For Load Line tests, the three pendulums are ideally set up in
different locations and the damping fluid is oil. Each pendulum is
measured to determine its length.
3.
Weight Placement - The inclining weights are normally placed on the
widest portion of open deck available, either at the rail or near
centerline. Weights are normally staggered so that each weight can be
moved all the way across the deck to the other rail. The block
positions are marked on deck so that movement distances can be measured.
4.
Deadweight Survey - Your Naval Architect will inspect all spaces in the
vessel for deadweight and prepare a list of weights and locations. For
large vessels where the deadweight survey is lengthy it may be
performed the day before the test. All spaces must be unlocked.
5.
Tank Survey - The levels in all tanks will be determined by visual
inspection. This is usually accomplished by reading sight gauges or
sounding tubes. Full tanks should be completely full into the vent or
fill lines above the tank. Empty tanks should be sucked down until the
stripping pump loses suction. For Load Line stability tests, empty
tanks must have their manholes removed, and if the bottom corner is not
visible from the manhole they must be gas free - safe for men.
6.
Freeboards - At pre-determined positions along the length of the vessel
on both sides, a sounding tape is dropped over the side and the
freeboard (distance from the deck to the water) is measured. By using
the lines plan in conjunction with these freeboards and the specific
gravity of the water (see item 7 below) an accurate representation of
the waterline and displacement (vessel's total weight) will be
developed.
7.
Specific Gravity - The density of the water the vessel is floating in
varies depending on its salinity and temperature. A hydrometer is used
to determine its specific gravity.
8. Block Movement/Pendulum Reading
- Once steps 1-7 are completed the incline can begin. All non-essential
personnel will be asked to leave. Those remaining on board will need to
supply their weight to the Naval Architect, and must remain perfectly
still in the same positions during each pendulum reading. The mooring
lines are slacked off and then initial upright pendulum readings are
taken. All subsequent pendulum readings are measured from the initial
readings. One block is then moved across the deck, its new position
measured, and another set of pendulum readings are taken. This is done
twice on each side with an intermediate pendulum reading taken with the
weights back in their starting positions. For Load Line stability
tests, three movements are done on each side.
9.
Calculations - The final step is to perform approximately five minutes
of calculations to determine the validity of the results. This is done
only to determine if the test was successful, not to give any stability
results. If the data is bad, steps 5 through 9 will be repeated.
Typical sources for bad data are excessive tank free surface, high
waves & wind, tight mooring lines, grounding, and open tank cross
connects.
C. Stability Analysis
Once
the stability test has been completed, a detailed set of calculations
will be performed in the Naval Architect's office. These calculations
will determine "Lightship", which is the total weight of the vessel
(without liquids in tanks or deadweight), and its center of gravity.
With this information any vessel condition may be analyzed on a
computer to determine operational limits.
These general recommendations are applicable to most vessels.
A. Free Surface
Free
surface is the sloshing of liquid in a tank from side to side. As a
vessel heels to one side, the center of gravity of the liquid in a
slack tank shifts in the direction of the heel, making the heel worse.
Narrow tanks have very little free surface, and are not generally a
cause for concern. Wide tanks (larger than 1/3 of the beam) with free
surface can cause severe stability problems. Only one pair of fuel
storage tanks and one pair of fresh water tanks should be slack at any
time.
B. Ballast Tanks
The
operator should always know the levels of the ballast tanks. If water
inadvertently enters an empty ballast tank or seeps out of a full
ballast tank free surface will result. Ballast tanks should be kept
either completely full or completely empty, and be checked on a regular
basis.
C. Sea Water Holds
Due
to the potentially high free surface of sea water holds, they should be
operated only in a completely empty or completely full condition, and
checked periodically to ensure that the level does not change causing
free surface to develop. Sea water holds should be filled and emptied
with the greatest care, by seeking shelter, or by assuming a favorable
heading into wind and sea. No more than one centerline or pair of P/S
holds shall be filled or emptied at a time. When
operating with slush or crushed ice in a hold tank, excess water should
be continually pumped out to minimize free surface effects. Many
insurers now require a level alarm to be installed at the top of each
flooded sea water hold so that the crew is alerted if the water level
falls below that point.
D. Freezer Holds
Holds
that store frozen cargo need to be loaded with care, and secured as
necessary. In heavy seas, loose cargo may shift and result in a
dangerous list situation.
E. Listing
Never
correct a list until you know the cause. If cargo has shifted resulting
in a list, pumping from tanks on one side to the other can result in a
dangerous situation by dramatically increasing tank free surface.
F. Icing
Stability reports generally give restrictions for operating under icing conditions. For the Bering Sea,
the ice accumulation is usually assumed to be approximately 1.32 inches
on decks and 0.33 inches on the sides, based on IMO recommendations.
During severe "icing" conditions the vessel may encounter ice loads of
much greater magnitude. Due to the lack of predictability in icing
conditions we strongly recommend that vessels take action to minimize
ice build-up by heading downwind or taking shelter.
G. Cranes
The
use of on-board cranes at sea can cause a dangerous situation if the
resulting list is too great, leading to a reduction of reserve
buoyancy. A stability report usually incorporates recommendations on
usage of cranes at sea. A good rule of thumb is never to submerge more
than half of the available freeboard in the act of lifting.
H. Freeing Ports
Freeing ports and scuppers should be kept clear of debris at all times to maintain their effectiveness.
I. Factory Operations (ref: 46 CFR 28.255)
A
space supplied with water for the sorting or processing of fish must be
fitted with a dewatering system capable of dewatering the space under
normal conditions of list and trim at the same rate as water is
introduced. Pumps used as part of the processing of fish do not count
for meeting this requirement. The dewatering system must be interlocked
with the pumps supplying water to the space so that in the event of
failure of the dewatering system the water supply is shut off.
J. Trash Chutes
A
trash chute from a watertight processing space should have a non-return
flapper and a means of securing it closed watertight from outside the
space. The area in way of the chute should be kept clear of machinery
and stores for access in an emergency. The flapper should never be
secured in an open position. The chute's operation should be checked
periodically.
K. Weather Tightness
All
weather deck doors, air ports, and vents should be kept closed and
securely dogged when operating in heavy weather conditions. All
watertight doors should be kept closed except when used for passage
under safe conditions.
L. Bilges
Bilges
should be kept pumped to a minimum level at all times. Bilge system
requirements for all fishing vessels are described in 46 CFR 28.250
& 28.255.
M. Modifications
No
permanent ballast or other such weights should be added, removed,
altered, and/or relocated, and no watertight bulkheads should be
removed or altered unless the effect on stability has been investigated
by your Naval Architect.
N. Anti-Roll tanks
Vessels with exceptional stability may be equipped with an anti-roll tank. These tanks are designed such that the liquid sloshes from side to side out of sync with the vessel's
rolling. In a correctly designed tank, the liquid will slosh to the
high side of the tank to reduce the vessel's roll amplitude, and give a
much more comfortable ride. In a poorly designed tank the liquid will
shift to the low side of the tank, increasing the rolling amplitude.
Anti-roll tanks must be "tuned" to each vessel. Since a vessel will
behave differently in a light condition than a heavy condition, an
anti-roll tank may be ineffective or dangerous in an out-of-tune
condition. For this reason, an anti-roll tank should never be put into
operation without first calculating its potentially negative effect on
stability.
O. Stability in a Seaway
Care
should be exercised when steering with a following sea. Going too fast
may drive the vessel through the swell ahead onto the downside where
the following swell can catch the stern and throw the vessel broadside
to the swells. This "broaching to" may cause the vessel to capsize. An
equally dangerous situation may result if the vessel's speed is close
to the speed of the swell upon which it is riding causing a loss of
steering control.
P. Freeboard
Freeboard
is the vertical distance measured from the water to the deck at side.
In some instances your Naval Architect may recommend a minimum overall
freeboard corresponding to the deepest possible draft.
Q. Deck Loads
Each
stability report will provide guidance for the maximum load (crab pots,
cod ends, etc.) which may be safely placed on deck. All deck loads must
be secured in a fashion that will prevent shifting in a seaway. You may
also be limited by the strength of the deck supporting the load. If you
are concerned about deck strength you should request that your Naval
Architect perform a structural analysis.
Each
vessel has its own stability characteristics and will tend to be
restricted by perhaps two or three of the criteria limits described in
section IIB. Because a similar size boat was able to place a larger
winch on his deck does not mean that your boat can. It is very
important to discuss any proposed changes with your Naval Architect
beforehand to ensure that the stability will not be impaired.
A. Adding Weight
Adding
weight high will raise the center of gravity and reduce stability.
Adding weight low will lower the center of gravity and increase initial
(upright) stability, but this is not always beneficial. Adding weight
on vessels with low freeboard causes the deck edge to submerge at a
smaller heel angle, and the righting arm curve to drop off sooner.
B. Removing Weight
Removing
weight below the main deck will reduce the initial stability, but may
increase the range of stability (the angle where the righting arm drops
to zero). Removing weight above the main deck will increase both the
initial stability and the range of stability.
C. Weight Growth
All
vessels will get heavier and experience a rise in the center of gravity
as time passes. This is because equipment, spares, dirt, paint, etc.
tend to accumulate. You should make an effort to keep your vessel in a
clean condition to reduce this potential problem. We recommend a new
stability test and report be prepared every five years, and whenever
you add/remove/relocate major pieces of equipment. It is also advisable
to perform an annual vessel cleanout, removing nonessential equipment
& gear.
D. Hull Form Modifications
There
are various methods of altering an existing hull that can significantly
alter load carrying and stability characteristics, including sponsoning, midbody
extension, deepening, raised poop decks, stern extensions, and house
additions. As a general statement, any hull alteration which creates
additional freeboard has the potential for improving stability and/or
increasing vessel payload. Each of the listed techniques can have
different benefits and costs for a particular vessel design.
Any
hull alteration is expensive. To obtain the best benefit to cost
factor, advance consultation with your Naval Architect concerning your
project objectives can pay high dividends. The same computer models
used for stability calculations can be utilized to forecast stability
and loading performance of different configurations. A few words
relative to each modification technique follow:
1. Sponsoning - Sponsons are extensions to the beam of a vessel, usually resulting in a second set of wing tanks. A carefully designed set of sponsons
will be almost unnoticeable to the eye, and will dramatically improve
stability and cargo carrying capacity. Wider vessels tend to have a
faster roll period (time to complete one roll cycle), which may not be
desirable in extreme cases.
2. Midbody Extension - For vessels with good stability, a midbody lengthening is a good way to increase the cargo carrying capacity. Vessels with poor stability may not benefit from a midbody lengthening because the stability is changed very little, and the extra cargo space may not be usable.
3.
Deepening - Adding watertight space on top of existing working decks
increases freeboard, thereby improving stability. This can be very
effective when a wet hold vessel is over tanked (too much weight and
too little buoyancy), or more combined deck and hold cargo is desired.
4.Raised
Poop Decks - A raised poop is a modified form of deepening. The
additional buoyancy aft does not increase freeboard, but does increase
righting arms as a vessel rolls. This relatively minor modification can
significantly improve stability characteristics.
5.
Stern Extension - A stern extension typically has very little effect on
the overall stability. Its common uses are to get the stern further out
of the water if the aft deck is very wet, and to increase working space
on the aft deck.
6. Adding
a house - The addition of a full width house will make a vessel heavier
and reduce upright stability, but will increase righting arms as the
vessel rolls. If your boat has sufficient upright stability but has
difficulty meeting the stability range requirements, the addition of a
watertight house may be helpful to the stability.
On September 15, 1991, safety regulations for United States
flag commercial fishing industry vessels were published by the U.S.
Coast Guard and became effective. Subpart E, Stability, is currently
applicable to vessels 79 ft or longer. Additional regulations will be
published in the future for vessels less than 79 feet in length. In
general, the regulations impose requirements for new vessels and
vessels which are modified after the effective date.
There
are two very important definitions: "Substantial Alteration" and "Major
Conversion". There is no clear boundary between these definitions. A
vessel undergoing a "Major Conversion" must meet several additional
stability criteria, which may further limit operations.
New
vessels built on or after September 15, 1991 must meet unintentional
flooding (damaged stability) per 46 CFR 28.580, which may be extremely
difficult or impossible to meet for vessels with large open holds or
engine rooms. This requires vessels to survive flooding with stability
margin when damaged lengthwise 10% of the vessels length (or 10 feet if
less), and transversely 30" from the side shell. All spaces with
through-hull fittings, such as engine rooms and lazarettes, must also be assumed simultaneously flooded. The alternative to meeting this criteria is obtaining and maintaining a Load Line.
An
evaluation of the regulatory impact will be essential for all future
changes to hull form or carrying capacity. Two essential stages of
project planning will be:
1.Clear determination of applicable regulatory requirements.
2.Preliminary engineering verification that the modified vessel will satisfy the regulations.
In
unique circumstances for which no precedent has yet been established,
the correctness of a preliminary evaluation of applicable requirements
should be offered to the local U.S. Coast Guard OCMI for confirmation.
Qualified Naval Architects can then verify that a planned alteration
will satisfy both the vessel Owner's objectives and regulatory
requirements.
VII. License Limitation Program (formerly Fishing Vessel Moratorium)
The
former Fishing Vessel Moratorium has been superseded by the License
Limitation Program. The full text of the regulations may be found 50
CFR 679.4, which is also available on the following web site: http://www.fakr.noaa.gov/regs. This program limits certain catcher and catcher-processor vessels in Alaska groundfish and Bering Sea/Aleutian Island crab fisheries to a maximum length overall (MLOA) shown on the groundfish license.
VIII. Vessels Requiring a Load Line or Classification
The
following information is offered only as basic guidance. For the
complete text of the law, please refer to 46 USC Chapter 51, and 46 CFR
42.03. The following definitions apply:
Fishing Vessel
(as defined in 46 CFR 28.50): "a vessel that commercially engages in
the catching, taking, or harvesting of fish or an activity that can
reasonably be expected to result in the catching, taking, or harvesting
of fish."
Fish Processing Vessel (as defined in 46 CFR 28.50): "a vessel that commercially prepares fish or fish products other than by gutting, decapitating, gilling, skinning, chucking, icing, freezing, or brine chilling."
Fish Tender Vessel
(as defined in 46 CFR 28.50): "a vessel that commercially supplies,
stores, refrigerates, or transports fish, fish products, or materials
directly related to fishing or the preparation of fish to or from a
fishing, fish processing or fish tender vessel or a fish processing
facility."
Existing Vessel
(as defined in 46 USC 5101): "a vessel on a domestic voyage, the keel
of which was laid, or that was at a similar stage of construction,
before January 1, 1986; and a vessel on a foreign voyage, the keel of
which was laid, or that was at a similar stage of construction, before
July 21, 1968."
46 USC 5102, Application (of Load Line Statues) 1995
(a) Except as provided in subsection (b) of this section, this chapter (LOAD LINES) applies to the following:
1. a vessel of the United States 2. a vessel on the navigable water of the United States 3.
a vessel owned by a citizen of the United States or a corporation
established under the laws of the United States or a State, and not
registered in a foreign country. 4. a public vessel of the United States. 5. a vessel otherwise subject to the jurisdiction of the United States.
(b) This chapter (LOAD LINES) does not apply to the following:
1. a vessel of war 2. a recreational vessel when operated only for pleasure 3. a fishing vessel 4. a fish processing vessel of not more than (less than) 5,000 gross tons that:
was constructed as a fish processing vessel before August 16, 1974, and is not on a foreign voyage
OR
was converted for use as a fish processing vessel before January 1, 1983, and is not on a foreign voyage.
5. a fish tender vessel of not more than 500 gross tons that:
was constructed, under construction, or under contract to be constructed as a fish tender vessel before January 1, 1980, or was converted for use as a fish tender vessel before January 1, 1983
AND
is
not on a foreign voyage or engaged in the Aleutian trade (except a
vessel in that trade assigned a load line at any time before June 1, 1992).
6. a vessel of the United States on a domestic voyage that does not cross the Boundary Line, except a voyage on the Great Lakes. 7. a vessel of less than 24 meters (79 feet) overall in length. 8. a public vessel of the United States on a domestic voyage 9. a
vessel excluded from the application of this chapter by an
international agreement to which the United States Government is a
party. 10. an existing vessel of not more than 150 gross tons that is on a domestic voyage 11. a small passenger vessel on a domestic voyage 12. a vessel of the working fleet of the Panama Canal Commission not on a foreign voyage.
46 CFR 28.720 Survey and Classification (of Fish Processing Vessels)
Each Fish Processing Vessel which is built after, or which undergoes a major conversion completed after July 27, 1990, must be classed by the ABS, or a similarly qualified organization.
