Tug use Offshore in bays and Rivers

Question 1

When performing a flat tow it is advantageous to lead with the _______ end of the ship rather than the ligh end. The tug should be made up on the end with the ______ free board if practical

Answer 1

Heavy, Most

Question 2

True of False: If the power tug is made up to far away from the pivot point, it can become overly difficult to control the ship. The lever arm is so great that with any speed the ship has a tendency to broach or sheer.

Answer 2

True

Question 3

Voith bow drive (VBD) and Azimuth bow drive (ABD) tugs are best used in flat towing in what position?

Answer 3

Set up for pulling the light end, and trailing the heavy end.

Question 4

What issues can a voith bow drive during a flat tow?

Answer 4

If the flat tow is heavy in the stern and bow the VBD can have difficulty controlling the tow in power make up. Additionally the wash from the voith units can have a negative interaction with the underwater portion of the flat tows hull, particularity if the flat tows draft is deeper than the VBD’s draft.

Question 5

When one starts considering the towing of ships or special tows like drill rigs, what are the critical factors?

Answer 5

tug size and horse power

Question 6

At present ( in the united states) if a tug takes a disable ship in tow where is it common for them to connect to?

Answer 6

directly into the ships anchor chain before the anchor, leaving the anchor on

Question 7

Experience has shown that very large merchant ships and large LNG tankers (125,000) will not track behind the tug without?

Answer 7

Active steering of the ship

Question 8

It is suggested that in significant _____________, towing and controlling any very large merchant ship ( with house aft) will be difficult

Answer 8

quartering winds

Question 9

Flat towing is?

Answer 9

is the shifting of a ship or barge that is not under its own power.

Question 10

The idea of having at least one tug made up so that it can control the flat tow single handedly is worth pursuing because?

Answer 10

It mitigates the risk of flat tow movement dramatically.

Question 11

Why is integrated multiple tugboat use more complex?

Answer 11

the number of conning commands required to control the tow increases dramatically, taxing the multitasking skills of the captain.

Question 12

What is the main difference in general between flat towing a barge vs a ship?

Answer 12

A barge is not directional stable due to its length to beam ratio. A ship will be more directional stable due to its high length to beam ratio. The directional stability of the ship will generally increase as the draft of the ship increases.

Question 13

True or False: It is generally requires more force from the power and assist tugs to initiate a turn or maneuver with a ship flat tow.

Answer 13

True

Question 14

How can you increase the lever arm to the pivot point of the flat tow?

Answer 14

place assist tugs on the after end of the tow

Question 15

On approaching a ship or barge to be flat towed, careful observations should be made as to the condition of the vessel such as?

Answer 15

• is the ship down by the head or stern?
• is the ship loaded or light?
• how will wind or current effect the ship?

Question 16

When flat towing a ship stern first it is advisable to remember?

Answer 16

that the expensive end is out front, if the tow were to hit something, the rudder and propeller of the ship would be most vulnerable.

Question 17

What are the two reasons it is generally more effective on a dead ships to move the power tug closer to the pivot point and slightly away from the dead ships bow or stern?

Answer 17

• If the power tug is made up to far away from the pivot point the leverage arm is to great and it will be difficult to control.
• ship can be made up parallel to mid body of ship without having issues with the counter of the ship.

Question 18

Why is it generally easier for the power tug to turn toward the dead ship while maneuvering underway?

Answer 18

The power tug is then working its stern line and the stern line is usually farther from the ships pivot point.

Question 19

Why can it be difficult to turn away from the dead ship without an assist?

Answer 19

the power tugs headline is considerably closer to the dead ships pivot point. That significantly reduces the leverage of the power tugs headline with any head way.

Question 20

If there is only one assist tug it is generally more effective to have the assist on the?

Answer 20

opposite side and end of the power tug.

Question 21

What position is best position for a VBD in a power make up?

Answer 21

on the lighter end of the flat towed ship or barge.

Question 22

Even more so than with conventional tugs, the tractors placements should be away from?

Answer 22

the extreme ends of the bow or stern.

Question 23

What is a way to mitigate the negating hydrodynamics effect of wash against the ships hull when using VB tugs?

Answer 23

By having both tractors thrusting at a 45 degrees angle toward each other, movement ahead or astern can be controlled precisely.

Question 24

True or False: With speeds of less than three knots, a direct pull from the trailing tractor is most efficient.

Answer 24

True