SABOT
Standardized Auxiliary Boat
Operations Training
Ninth District - Eastern Region
COMO. Lew Wargo, Sr.
CQEC-9ER
02 APR 2015
GENERAL TOWING
SABOT
GENERAL TOWING
REFERENCES
• Coast Guard Addendum to the National
Search and Rescue Manual (NSS), COMDTINST
M16130.2(series)
• Auxiliary Operations Policy Manual
COMDTINST M16798.3 (series)
REFERENCES
• Boat Crew Seamanship Manual,
COMDTINST M16114.5(series)
Chapter 17
• Auxiliary Boat Crew Qualification Guide,
COMDTINST M16794.52(series)
• SABOT Job Aid (Section H)
GENERAL
A.Do a complete RISK ASSESSMENT with the
crew before undertaking any towing
evolution.
B.Communicate with the towed vessel’s crew
who may have important information
necessary to complete a successful mission
GENERAL
C.Should I Tow?
• What is the WX condition?
• What is the gross tonnage?
• Am I experienced to tow in the conditions?
• Will the vessel’s casualty effect towing?
• Is the construction of the D/V sound?
GENERAL
• What is the number of POB on the D/V?
• Should all or some of the POBs be removed?
• How does the vessel ride in the sea conditions you
may encounter?
• Are all POBs wearing PFDs?
• Has the operator every been towed by the Coast
Guard before and how was it done?
GENERAL
• Does the D/V have the proper fittings for
towing?
• Is the D/V capable of emergency signals to
attract your attention in the event of radio
failure?
GENERAL
D. Caution:
Do not let a preceived need to engage in a
towing mission override a complete, honest
Risk Assessment process that emphasizes
personal safety.
GENERAL
E. Change: The dynamics of a towing
situation continuously change from the
time pre-towing preparations begin until
mooring at the conclusion of the mission.
Think ahead, what could change and how
would you handle the change?
GENERAL
F. Training: Realistic towing training based on
standardized techniques, critical analysis, and
mission debrief will contribute to risk
management and the development of a
towing risk management plan.
FORCES
IN TOWING
STATIC FORCE
A.
Inertia: The tendency of a vessel at
rest to stay at rest. The more mass
(displacement) a vessel has the more
inertia it has and the harder it is to get it
moving.
FORCES
IN TOWING
B.Moment of Inertia: Occurs when a towed
vessel resists turning to change heading. The
larger the vessel, the more resistance there
will be in turning. Unless necessary due to
immediate danger, DO NOT attempt to start
towing ahead and change direction at the
same time. Start slowly on the initial heading
of the tow if possible.
FORCES
IN TOWING
C. Caution: When towing vessels of equal or
greater mass, the capacity and capability of
the towboat will be strained. This requires
slow and gradual changes of speed and
direction. Attempt to start towing on the
initial heading to gradually overcome the
tow’s inertia. Even when underway, the tow
will resist turning.
FORCES IN TOWING
DYNAMIC FORCES
A. Dynamic forces occur once the towed vessel
is moving. They are based on the towed
vessel’s characteristics (shape, displacement,
arrangement, and rigging), the motion
caused by the towing vessel, and the effects
of waves and wind.
FORCES
IN TOWING
A. Momentum:
Once a vessel moves in a straight line, it wants
to keep moving in a straight line.
B. Angular Momentum:
Once the towed vessel’s heading begins to
change, it wants to keep changing in the same
direction.
FORCES
IN TOWING
D. Frictional Resistance:
As a vessel moves, the water in contact with
the hull moves as it is dragged. The greater
the under-water area of the vessel the greater
the frictional resistance. This keeps a steady
tension in the towing rig and is managed by
speed. Higher speeds cause higher friction and
more strain.
FORCES
IN TOWING
E. Form Drag:
The size and shape of a towed vessel can
help or hinder. A deep draft vessel takes
more effort to change direction than a fine,
shallow (planning) hull. Deep draft towed
vessels may be able to help offset form drag
by using its rudder.
FORCES
IN TOWING
F. Wave Making Resistance:
A surface wave forms at the bow while the hull
moves through the water. The size of the bow
wave increases as speed increases and
generates resistance to movement of the boat.
CAUTION: Do not tow any vessel above it’s hull
speed.
FORCES
IN TOWING
G. Wave Drag:
Depends on the wetted surface area of the
hull and the amount of freeboard exposed to
wave action. In heavy seas this can cause the
tow to stop and transfer a heavy strain to tow
rig. In head seas the towing vessel can control
this with speed and angle. In following seas
speed up and slow down to keep tension on
towline.
FORCES
IN TOWING
H. Spray drag:
Provides resistance to the tow increasing
shock load.
I. Wind Drag:
Can cause shock loading and have a bad
effect on the towed vessel’s motion and
stability.
FORCES
IN TOWING
J. Buoyancy Response & Gravity Effects:
A towed vessel’s bow may react to a wave by
pitching up, or by sub-marining. Buoyancy
response to following seas may cause tow to
yaw or gravity may cause it to gain speed and
surf down the face of a wave. Once making
way, a vessel’s buoyancy response or the
effect of gravity may cause severe shockloading.
FORCES
IN TOWING
K. Combination of Forces & Shock-Load
Rarely do you deal with only one force acting
on a tow. Shock-loading may cause severe
damage to both vessels and overload a tow rig
to the point of failure. It may also cause
momentary loss of directional control by
either vessel and could capsize smaller
vessels.
FORCES
IN TOWING
•
•
•
•
•
•
•
TO COUNTER-ACT SHOCK LOADING:
Place vessel In-Step
Lengthen the towline
Change course
Deploy drogue
Reduce towing speed
Adjust towing speed
FORCES
IN TOWING
•
•
•
•
•
•
•
COMBINATION OF FORCES
Inertia
* Momentum
Form Drag
* Wave Drag
Wind Drag
Movement of Inertia
Angular Momentum
Frictional Resistance
Wave Resistance
FORCES
IN TOWING
Shock-Loading dangers:
1. It can cause damage to tow rig and
fittings.
2. It can break the towline and cause “Snapback”!
3. Can swamp or capsize the tow.
TOWING
EQUIPMENT
Towline: Have faked out on deck or otherwise ready for
easy deployment.
• Regularly inspect for: cuts, chaffing, flattening (from
excessive loading), fusing (from excessive loads), or snags
A.
IF ANY OF THE ABOVE – DO NOT USE The tow rig is only as
strong as it’s weakest link! (If a tow rig uses a ¾” nylon
towline with a 1 ton rated shackle, the tow rig is limited to
1 ton!)
Have towline faked out and ready for easy deployment, see
next slide:
FAKED LINE
TOWING
EQUIPMENT
B. Pendant: A short length
of towline used between
the towed vessel and
towline. It is used to
prevent wear on the
towline. This could be 1/2
of a bridle.
TOWING
EQUIPMENT
C. Bridles: Inspect regularly with towline.
1. Use “Y” bridle when both legs can be
rigged to exert an equal pull on the
hull.
2. Should be long enough to clear all
obstructions on the deck and meet
forward of the bow.
TOWING
BRIDLE
TOWING
EQUIPMENT
3. Keep the bridle legs long enough to keep the
angle of the legs under 30 degrees.
4. The legs must be long enough to reduce the
towed vessels yaw.
5. Protect with chaffing gear as necessary.
6. Used to center tow behind towboat and/or to
clear obstructions on stern of towboat.
TOWING
EQUIPMENT
D. Heaving lines:
• Light weight,75 to 100 feet long.
•
Cotton line works well (wet before using)
•
The end should be lightly weighted for
throwing.
•
Suggest having more than one
•
Attach a small snap on the standing end for
quick attachment to the tow rig.
TOWING EQUIPMENT
Heaving line and ball
Float Line
Always yell “HEADS UP” before throwing
Always throw over the target (BOAT)
TOWING
EQUIPMENT
G. Dock lines: Have sufficient dock lines to
moor your vessel while you have another
vessel in an alongside tow.
H. Fenders: Have enough fenders to properly
protect both vessels while in an alongside tow
and for docking with the side tow. Use the
largest size you can store. Have one large
extra fender.
TOWING
EQUIPMENT
I. Skiff Hook:
A snap hook that is used to attach a towline
to the towing eye on smaller boats that do
not have suitable deck cleats. The skiff hook
attaches to the end of a pole (boat hook) for
reaching the towing eye of a D/V. The towing
eye is one of the strongest attachment points
on a boat but is extremely hard to reach for
connecting and disconnecting the towline.
TOWING
PROCEDURES
Throughout the entire towing evolution,
communications between the coxswain and
crew is absolutely necessary for a Safe and
efficient operation.
TOWING
PROCEDURES
A. Notification: Get as much information as
possible/needed before getting underway.
Assign this duty to one of the crew.
Write all information down. Develop a full
understanding of the situation.
Make a conscious decision to “Accept” or
“Not Accept” the mission.
B. Brief the crew.
TOWING
PROCEDURES
• C. Evaluate the conditions with the crew.
• D. Navigate safely to the scene:
Operate at a safe speed at all times.
Keep a constant awareness of position
and area hazards.
Stay aware of the distressed vessel’s
position and condition.
TOWING
PROCEDURES
E. Communications with D/V:
1. Keep in radio contact on a regular
basis and give an ETA.
2. Advise POBs on D/V to don PFDs.
3. Get details of D/V’s deck layout
4. Ask for any important information.
5. Determine if anything has changed.
TOWING
PROCEDURES
6.Ascertain any sense of heightened urgency.
7.Inform the D/V that once on scene you will
observe conditions and make final
preparations before setting the tow.
TOWING
PROCEDURES
NOTE
Once on scene don’t allow D/V to become
endangered while waiting for POB to put on
their PFDs. Take action to remove POBs from
danger or from the D/V.
TOWING
PROCEDURES
• F. Perform On-Scene Assessment:
1. Evaluate the location and any
abnormal conditions of deck fittings.
2. Confirm the number of POBs.
3. Note any unusual conditions that
would affect towing, (loose gear,
rigging, etc.)
TOWING
PROCEDURES
4.Decide if you should place crew on D/V or
remove any POBs from the D/V.
5. Decide whether to tow or not.
6.Do you need a bridle on the D/V?
7.Will a drogue be needed for the tow?
8.Brief both crews of intentions.
TOWING
PROCEDURES
G. Determine the approach: Crossing the
“T”, parallel or back-down.
H. Determine method for passing tow rig
I. Brief both crews
J. Determine the “Danger Zone”
K. Determine the “Maneuvering Zone”
L. Determine the “Optimum Position”
“Y” BRIDLE
ASTERN TOW
“Y” BRIDLE
ASTERN TOW
SINGLE LEG
ASTERN TOW
SINGLE LEG
ASTERN TOW
SINGLE LEG
ASTERN TOW
“V” BRIDLE
ASTERN TOW
ASTERN TOWING
A. Maneuver:
•
Your vessel so crew can maximize use of the
best deck area for passing the tow rig.
•
Bow or stern into the seas. This will provide the
most vessel control and visibility for the
coxswain, while station keeping a safe
distance from the D/V.
•
Plan a safe “Escape Route” for emergency.
ASTERN
TOWING
B. Rough seas: In rough seas make approach
with bow or stern into the prevailing forces.
(if it works in rough seas it will work in any
seas)
(NOTE: IF THE SEAS ARE TOO HEAVY AND YOU
ARE TAKING ON WATER OVER YOUR STERN,
YOU ARE IN SEAS TOO ROUGH FOR YOU!)
ASTERN
TOWING
C. Approach:
– Make approach at the slowest speed
possible while maintaining steerage.
– Stop in optimum position and pass the tow
rig with a heaving line (At coxswain’s
command).
– (Coxswain MUST let the crew know before
making correcting maneuvers so that they
can safely tend lines.)
ASTERN
TOWING
D. Opening & closing:
Use opening and closing maneuvers to maintain
optimum position. Act before a problem
develops.
(NOTE:) Maneuver as required but it is
preferable not to maneuver when lines are
over (except the heaving line).
ASTERN
TOWING
E. Passing the tow rig:
(Include drogue if it is needed.) In calm
conditions the rig may be passed by simply
handing it over or by use of a boat hook.
Practice using a heaving line for moderate
or heavy seas.
ASTERN TOWING
1. To pass the heaving line:
• If cotton heaving line wet it to make it more
flexible and to minimize tangling.
• Take 2/3 of the heaving line coil into the
casting hand and the reminder in the other.
• Check if area is clear of obstructions.
ASTERN
TOWING
• Advise the coxswain when ready (“I have a shot”)
• Coxswain will give command “Take your shot”
• Call out to the D/V “Heads up”
• Cast so the heaving line falls across the D/V’s deck.
• Tell the coxswain when casting
ASTERN
TOWING
• If not successful, quickly retrieve the heaving
line and prepare a second line or attempt.
• Repeat steps 2 through 7 until successful
ASTERN
TOWING
2. Keep coxswain advised on tow rig transfer:
a.
“TOW RIG AWAY”
b.
“TOW RIG IN THE WATER”
c.
“TOW RIG ON D/V”
d.
“TOW CONNECTED”
e.
“D/V CREW SECURED”
ASTERN
TOWING
F. Connecting the tow rig:
1.
2.
3.
4.
5.
Monitor crew of D/V to follow directions
Towline clear of any gear on deck
Chaffing gear
Under railing
Not pulling against railing or stanchion
ASTERN
TOWING
2.Connect to cleat or the “Towing Eye”.
If using the towing eye use extreme caution
in bringing the vessels together. (Not safe to
do in rough seas)
If using deck fittings, be sure they are in
good condition. Don’t hesitate to put crew
aboard to check out conditions.
ASTERN
TOWING
3.Have crew of D/V return to cockpit area after
securing towline
4. Slowly open distance between boats and
manually adjust length of towline. (Crew and
Coxswain should be in communication
constantly during this process.)
(Line in water, Tension coming on line, under
tow)
ASTERN
TOWING
5. Have your crew take a working turn on
bitt/cleat before there is a strain on towline.
6. After length is set (Maintain a catenary in
tow rig) make up line on bitt/cleat.
ASTERN
TOWING
A. Start tow slowly and if possible, in the
direction the D/V is pointing.
B. Set “tow Watch” and maintain COMMS with
the D/V.
C. Slowly bring tow onto desired heading
D. Watch for “YAWING” or any other problems
with the tow.
ASTERN
TOWING
E. Maintain catenary while towing
F. Keep tow in step and tow at safe speed
G. If yawing:
•
straighten helm of D/V or, If O/B or I/O raise
it’s lower unit or,
•
adjust the trim on D/V (Move POBs) or,
•
decrease speed or,
•
change angle into waves or wind or,
•
deploy a drogue from D/V.
USE OF A
DROGUE
H. Drogues are used behind a tow to slow it
down and give stability. It acts much like
a parachute. It’s deployed from the stern
of the towed vessel. A traditional drogue is a
canvas or a synthetic cloth cone open on
both ends.
USE OF A
DROGUE
With a short hawser and large swells on the
stern, the drogue is deployed to prevent the
tow from running up the stern of the towboat
as it keeps tension on the towline preventing
the tow from “surfing down the face of a
wave.
USE OF A
DROGUE
The drogue should have about 200 feet of line
(marked every 50 feet) attached to the bridle
swivel using a shackle.
Pass the drogue directly to the D/V and watch
the crew ready the drogue rig. Use centerline
attachments or bridle unless compensating for a
jammed rudder.
USE OF A
DROGUE
• A second light line should be attached to the
smaller end of the drogue for ease of drogue
retrieval.
• Start the tow moving slowly, then deploy the
drogue. Once it sets, increase speed while the
towed vessels crew observe the rig.
USE OF A
DROGUE
To avoid fouling drogue lines:
Slow or stop the tow and have the towed
vessel recover the drogue.
Run a “dumping” line from the drogue to the
stern of the towed vessel (suitable for large
drogues that drain slowly).
ASTERN
TOWING
I. Shortening the tow:
1. Select a safe area
2. Brief both crews on planned action.
3. Determine new towline length
4. Reduce speed and take off way slowly
5. Break towline from bitt/cleat
ASTERN
TOWING
6. Back as crew keeps line out of screws
7. When at desired length, make up line on
bitt/cleat
8. Resume tow in direction of D/V heading
ALONGSIDE
TOW
• Always do in calm protected waters.
A. Determine which side to tow from:
• Consider side of dockage
• Consider your visibility
• Consider location of fittings on each vessel
• Consider the type of approach (free or backdown)
• Consider which vessel will be against the dock.
BACK-DOWN
FREE APPROACH
ALONGSIDE TOW
B. Prepare alongside tow lines
C. Position fenders to protect both boats
D. Prepare dock lines and have boat hooks ready
E. Note direction of wind and current and
consider their effect on mooring
F. Always connect Line #1 first then #2.
ALONGSIDE TOW
G. If necessary you can then start towing in a
forward direction only.
H. Connect line #3 and then #4 if used.
I. Adjust fender position or use a “Walking”
fender as necessary.
ALONGSIDE TOW
J. Tighten lines as follows:
• While going forward and turning away from
the tow, tighten lines #3 and/or #4.
• Go in reverse to tighten lines #1 and #2 or
while in forward turn into the tow.
ALONGSIDE TOW
• CAUTION: Keep all body parts out from
between boats.
• Always place the eye of a line on the D/V so
that adjustments can easily be made from
towing boat.
• You may have to place crew aboard the D/V
as a lookout
ALONGSIDE TOW
4 LINE
ALONGSIDE TOW
3 LINE
ALONGSIDE TOW
MOORING
ALONGSIDE TOW
A.
It is easier to moor into the prevailing
force and on the lee side of dock.
B.
Use only enough speed for steerage
C.
Use a lookout to call range and bearing
to dock and objects or other traffic.
MOORING
ALONGSIDE TOW
D. It is easier to turn toward the tow in
forward. To make a turn away from the
tow consider going in reverse. You can
make a very sharp turn in reverse.
E. If possible, place the larger of the two
vessels against the dock.
F. Secure D/V to the dock
MOORING
ALONGSIDE TOW
G. Gather required information for reports.
H. Break tow
I. Report “Tow secure” per local policy.
J. Get underway
TOWING
PRECAUTIONS
• A. Have all POBs on D/V don PFDs. Furnish if
necessary. Don’t jeopardize POB or vessel
safety waiting for POBs to don PFDs.
• B. Remove POBs when necessary
• C. Cast heaving lines well over D/V so line
falls across D/V’s deck.
• D. Monitor conditions of the tow rig.
TOWING
PRECAUTIONS
E. Establish and maintain D/V COMMS
F. Monitor any sea-water on D/V
G. Monitor conditions of POBs on D/V
H. Keep clear of tow rig (SNAP-BACK)
I.
Keep tow rig attachment points low and
near the centerline
TOWING
PRECAUTIONS
J. Do not attach tow rig to lifeline,
stanchions, grab rails, or ladders.
K. Do not attach lines to cleats that are
only held by screws.
L. Avoid using lines provided by the D/V
M. Avoid using knots to join tow-lines
N. Use two crew if possible to tend lines
TOWING
PRECAUTIONS
O. Tend a towline by hand until secured to
D/V then secure on coxswain’s command.
P. Only use figure-eight cleat hitches on
cleats with NO weather hitch.
Q. Crew should keep clear of towline.
TOWING
PRECAUTIONS
R. Crew should not cross arms but change
hands when handling lines.
S. Keep towline clear of prop and rudder.
T. Use chaffing gear as needed.
U. Avoid towing boats over 50% larger.
V. Tow at a safe speed for conditions.
W. Avoid sudden maneuvers.
TOWING
PRECAUTIONS
X. Consider a drogue to reduce yaw.
Y. Have helm of D/V manned and have D/V
steer at stern of towboat if needed.
TOWING
PRECAUTIONS
Z.
Keep towed boat in trim, consider:
1. Condition of D/V (damage, taking on
water, etc.)
2. Structural design of D/V
3. Cargo
4. Number and location of POBs
TOWING
PRECAUTIONS
WARNING
Overloading astern, or along either side of the
centerline, may swamp or capsize a tow!
TOWING
PRECAUTIONS
AA. Maintain a diligent tow watch. All
crew should be assisting in this.
AB. Bridle breaking strength should be
equal to or greater than towline.
AC. If possible, do GPS and chart work at
dock
TOWING
PRECAUTIONS
AD. If there is a possible need for a pump
or drogue, pass before start of tow.
AE. Coxswain/Crew should inspect the tow rig
before it is connected.