Emergency Towing

Question 1

What is one of the most dangerous evolutions conducted in the marine environment

Answer 1

Towing

Question 2

No two towing evolutions are

Answer 2

exactly the same

Question 3

Except int he simplest, easiest and least risky of all situations, towing should be

Answer 3

a last resort and then only if Coast Guard or commercial sources aren’t readily available.

Question 4

When should you tow someone

Answer 4

If the Coast Guard or commercial sources can’t or won’t be available in time to keep the vessel and its occupants safe

Question 5

The most important concerns is

Answer 5

safety

Answer 6

through communication

Question 7

Realistic towing training based on standardized techniques, critical analysis, and mission debrief will contribute to

Answer 7

risk management and the development of a towing risk management plan.

Question 8

For non-emergencies, rather than take another vessel in tow the best choice may be

Answer 8

for the disabled vessel to simply drop anchor and await assistance from commercial sources.

Question 9

Other forms of assistance to a boat include

Answer 9

Transferring fuel (if it can be done safely), providing a communications relay, or standing by and monitoring until assistance arrives

Question 10

The moment you attach a line to another vessel, you become

Answer 10

responsible for it and all persons onboard.

Question 11

Your first responsibility is to

Answer 11

your own vessel and crew, and keeping them safe is paramount.

Question 12

If the time comes when you must tow another vessel (or be towed), what is critical?

Answer 12

a fundamental understanding of the issues involved is critical.

Question 13

All personnel on the vessel being towed should be

Answer 13

wearing a suitable PFD.

Question 14

If a tow line fails under load it will snap back in the direction

Answer 14

of the pull.

Question 15

The preferred tow lines are usually

Answer 15

double-braided nylon of suitable circumference and length for the vessel to be towed because it offers a good combination of strength and elasticity.

Question 16

When towing a small vessel only a short distance in protected waters, what kind of rope can be used

Answer 16

polypropylene (but NOT a ski tow rope!) can be used.

Question 17

Offshore or in heavy weather, more tow line may be needed to keep a towed vessel in step and to minimize the effect of shock-loading due to seas.

Answer 17

keep a towed vessel in step and to minimize the effect of shock-loading due to seas.

Question 18

The tow line should always be the _______ ____ in the towing gear.

Answer 18

“weakest link”

Question 19

Towline should be stowed on

Answer 19

tow reel whenever possible, with the bitter end secured to the reel with smaller line. The line will lie evenly on the reel. More importantly, to quickly release the towline in an emergency, just cut the smaller line with a knife, and the bitter end will run free.

Question 20

When putting new towline in use, splice an eye at both end to allow an “end-for-end” switch before part of the towline is beyond useful service.

Answer 20

to allow an “end-for-end” switch before part of the towline is beyond useful service.

Question 21

Things the da

Answer 21

Cuts
Chafing
Flattening
Fusing (caused by overheating or over-stretching)
Snags
Hardening (heavy use will compact and harden a towline and reduce its breaking strength)
If a line shows any of these characteristics, do not use it as a towline.

Question 22

It is not always possible, or safe, to attach a tow line directly , in these cases a

Answer 22

bridle might be the best coalition. The bridle attaches to the eye of a tow line and is made fast to the deck fitting(s) on the towed vessel. Like the tow line, double-braided nylon makes the best towing bridles for most small to medium-sized
vessels.

Question 23

For a towing bridle to equally distribute the load and provide a center pull,

Answer 23

both legs of the bridle should be even length.

Question 24

To reduce west and chafing at the towline end, use a

Answer 24

pendant

Question 25

Use a long bridle when

Answer 25

the best attachment points of the towed vessel re well aft to either side of the deck, but maintain a fair lead forward to reduce chafe.

Question 26

The angle of a tow bridle’s left should be

Answer 26

less than 30 degrees

Question 27

The legs of a towing bridle should be long enough to reduce

Answer 27

towed vessel yaw

Question 28

protect bridges with

Answer 28

chafing gear when nescessary

Question 29

Where should thimbles be used in two bridles

Answer 29

in the leg eyes where they mmeet

Question 30

When shackled to the towline, remember to _____ the shackle pin.

Answer 30

Mouse

Question 31

What is a length of light line used to carry a larger line or hawser between vessels?

Answer 31

a messenger

Question 32

The following may serve as a messenger for small vessel towing evolutions

Answer 32

heaving line and heaving ball
float line
fender

Question 33

What line is made if light, flexible line with a monkey’s fist at the thrown end?

Answer 33

Heaving line.

Question 34

Heaving line must be at least __ feet long.

Answer 34

75

Question 35

What protects towlines, bridles and pendants from wear caused by rubbing against deck edges, gunwales, bulwarks, chocks, taffrail or two bars

Answer 35

Chafing gear placed at friction points.

Question 36

Three common items can be used to help with the towline or bridle wear to prevent chafing

Answer 36

old fire hose
heavy canvas
lether

Question 37

steel or galvanized iron, grooved, heart-shaped insert that is fitted into eye splices to provide strength and to minimize wear and tear due to chafing action.

Answer 37

A thimble. Thimbled splices permit joining two lines with shackles.

Question 38

What is a triangular shaped heavy steel plate with three holes, one at each corner?

Answer 38

a fishplate

Question 39

The three-fold purpose of the fishplate is to

Answer 39

add strength at the connections
at weight to the make-up
maintain a horizontal position underwater while towing to prevent twisting of the hawser and bridles

Question 40

What are attachment or fair lead points on vessels for towlines, anchor lines, and mooring lines.

Answer 40

Fittings

Question 41

For towing, only use attachment points and fair leads designed

Answer 41

for horizontal loads. Common fittings include mooring bitts, towing bitts, cleats, chocks, and Samson posts. A tow bar or taffrail acts as a fair lead.

Question 42

What hook has a quick release safety buckle and snap hook clip that can be attached directly to the boathook handle.

Answer 42

Skiff hook

Question 43

To use a skiff hook you

Answer 43

Attach the skiff hook line to a towline with a shackle or double becket bend
Use the skiff hook assembly to reach down and place the hook into a small disabled vessel’s trailer eye
The hook is snapped into the eye and the handle is slipped off the round stock and pulled back

Question 44

What is a frougue

Answer 44

a device that acts in the water somewhat the way a parachute works in the air. The drogue is deployed from the stern of the towed vessel to help control the towed vessel’s motions. Operators must familiarize themselves with the operating characteristics and effectiveness of available drogues. Test drogues under various conditions to learn drogue capabilities. The time to learn about a drogue is before you need to deploy one.

Question 45

Drogues are typically used when

Answer 45

he tow is shortened as in preparing to tow into a bar or inlet. With a short hawser and large swells on the stern, the drogue is deployed to prevent the towed vessel from running up the stern of the towing vessel and keep tension on the towline to help prevent the towed vessel from “surfing” down the face of a wave.

Question 46

PREPARE THE DROGUE GEAR

Answer 46

Visually inspect the drogue rig for worn rusted, or corroded fittings and swivels, correct
size shackles, and untangled bridles.

Ensure that the drogue rig has 200 feet of two-inch, double-braided nylon line properly
attached to the bridle swivel using a correctly sized shackle. Make sure it has no sharp
fittings or exposed wires, and is stowed in a manner that will keep it intact until it is deployed.

Provide all necessary equipment with a drogue rig such as extra shackles, bridles, straps,
and chafing gear to achieve the best possible connection on the stern of a tow.

Place all equipment in a gear bag along with laminated written instructions and illustrations on
how to rig a drogue, both with and without a bridle. At night attach a chemical light to the bag
and include a flashlight inside.

Attach flotation to the bag, usually a fender, and two lines, each 40 feet in length, to the
handles of the gear bag. Bend a heaving line or buoyant line onto one of the lines.

Question 47

Fenders

Answer 47

rotect a hull when maneuvering in close proximity to other vessels, docks or pilings. Fenders have either eye(s) or a longitudinal hole for attaching lines. They can be spherical, cylindrical, or rectangular prisms. Fender size varies greatly, and the appropriate size should be used depending on the situation. Use fenders that will keep space between vessel hulls or rub rails and hulls.

Question 48

What type of sources cause a vessel to resist motion

Answer 48

Static forces such as mass of the vessel and its displacement.

Question 49

What are the two different properties of statice forces which cause resistance in towing vessels

Answer 49

Inertia and the Moment of Inertia

Question 50

INERTIA

Answer 50

is the tendency for a vessel at rest to stay at rest. The more mass a vessel has (the greater its displacement), the harder it is to get it moving.

Question 51

The moment of Inertia

Answer 51

occurs when a towed vessel resists effort to turn about a vertical axis to change heading. The larger the vessel, the more resistance there will be in turning the vessel. Unless necessary in a case of immediate danger, do not attempt to tow a disabled vessel ahead and change its heading at the same time.

Question 52

Both interim and the moment of inertia strain the towing equipment so

Answer 52

deal with them separately whenever possible

Question 53

Once making way, the static forces

Answer 53

lessen

Question 54

Dynamic forces occur once

Answer 54

the towed vessel is moving

Question 55

the dynamic forces forces when a vessel is being towed depend on the

Answer 55

vessel’s characteristics (Shape, arrangement, rigging)
the motion caused by the towing vessel
the effects of waves and wind

Question 56

Once a vessel is moving in a direction its _____ wants it to keep moving in a direction

Answer 56

momentum

Question 57

ANGULAR MOMENTUM

Answer 57

Once the vessel’s heading begins to change, it wants to keep changing in that same direction. The faster the towed vessel’s heading changes, the harder it is to get the tow moving in a straight line.

Question 58

FRICTIONAL RESISTANCE

Answer 58

As a vessel moves, the layer of water in immediate contact with the hull moves. Due to friction between water molecules, the layers of water close to the hull try to drag along. The vessel appears to move “through” the water. This attempt to drag water alongside takes energy. As speed increases, this action becomes “turbulent.” This turbulence takes additional energy, and more speed requires even more power.

Question 59

DRAG

Answer 59

The less water a hull shape has to push out of its way, the easier it will move through the water. A deepdraft, full-hulled vessel takes more effort to move than one with a fine, shallow hull. A large amount of lateral resistance, spread evenly over the length of the hull, will hinder effort to change a towed vessel’s direction, but will help offset angular momentum in steadying up on a desired heading.

Question 60

WAVE MAKING RESISTANCE

Answer 60

A surface wave forms at the bow while the hull moves through the water. The size of the bow wave increases as speed increases, causing the wave to create resistance for the bow to be pulled or propelled through the water.

Question 61

Never tow a vessel faster than

Answer 61

the design speed of its hell

Question 62

A boat cannot go faster than about

Answer 62

1.4 times the square root of its waterline lengt, in knots.

Question 63

”Shock-load” or “shock-loading” is

Answer 63

the rapid, extreme tension on the towline, which transfers through the tow rig and fittings to both vessels.

Question 64

frictional forces act on

Answer 64

the hull, topsides, superstructure, and rigging.

Question 65

Wave drag

Answer 65

depends on the “normal” wetted surface area of the hull and the amount of freeboard exposed to wave action. Wave drag has a large effect on the strain of the tow rig.

Question 66

In when towing in head seas, be aware of:

Answer 66

Towing vessel can only control the effect of wave drag by the speed and angle that the towed vessel encounters the waves. Limiting speed and towing at an angle to the seas to prevent them from breaking over the bow of the towed vessel.

Question 67

When towing in following seas be aware that

Answer 67

Wave drag causing the towed vessel to speed up as the crest approaches, increasing
speed to keep tension in the towing rig, and reducing speed as the crest passes

Question 68

Spray Drag

Answer 68

The spray from a wave could slow the towed vessel and increase the amount of shock loading. Spray drag could also adversely affect the towed vessel’s motion by imparting a momentary heel, pooling on deck or in the vessel cockpit, and in cold weather form ice, and thus decrease stability.

Question 69

Wind drag

Answer 69

Wind drag can cause shock loading and have a bad effect on the towed vessel’s motions and stability. A steady beam wind can cause list and leeway, while a severe gust can cause a threatening heel. List, heel, and leeway may cause the towed vessel to yaw. A headwind increases tow rig loading in a direct line with the towed vessel while the towed vessel crests a wave, causing shock-loading.

Question 70

Because of the potential dangers, the tow vessel must use various techniques to prevent or counteract shock-loading, or reduce its effect.

Answer 70

Reduce Towing Speed

Slowing down lowers frictional resistance, form drag, and wave-making resistance. Reducing these forces will lower the total tow rig tension. In head seas, reducing speed also reduces wave drag, spray drag, and wind drag, lowering the irregular tow rig loads. The total reduction in forces on the tow could be rather substantial. When encountering vessel wake in relatively calm conditions, decrease speed early enough so the towed vessel loses momentum before hitting the wake. A small towed vessel slamming into a large wake will shock-load the tow rig, and may even swamp.

Get the Vessels “In Step”

Extreme stress is put on the tow rig in heavy weather when the tow vessel and the towing vessel do not climb, crest or descend waves together. Vessels in step will gain and lose momentum at the same time, allowing the towing force to gradually overcome the towed vessel’s loss of momentum, minimizing shock-loading. To get the vessels in step, lengthen rather than shorten the towline if possible. When operating near bars and inlets, getting the vessels in step may be impractical due to rapidly changing water depth and bottom contours.

Lengthen the towline

A longer towline reduces the effect of shock-loading in two ways. The weight of the line causes a dip in the line called a catenary. The more line out, the greater the catenary. When tension increases, energy from shock loading is spent on “flattening out” the catenary before it is transferred through the rest of the rig and fittings. The second benefit of a longer towline is more stretch length. Depending on the type of towline, another 50’ of towline length will give 5’ - 20’ more stretch to act as a shock-load absorber. Remember to lengthen the towline enough to keep the vessels in step and minimize the shockload source.