Drive a Boat

Question 1

Interaction
The three situations of interaction the bridge team should be aware of are:

Answer 1

When a vessel moves through a seaway, it displaces the water in which it moves.

This results in pressure differences and causes interactional movement between vessels and their environment

Head on interaction
Overtaking interaction
Interaction in narrow channels

Question 2

Head on interaction

Answer 2

1. Vessels pass, bows deflected
2. Attraction when passing alongside
3. HP from propwash may shear sterns away from each other

Question 3

Overtaking interaction

Answer 3

1. Overtaking vessels bow shears overtaken vessels stern away, shearing their bow into the path of the overtaking vessel
2. Attraction when vessels passing along side
3. When bows aligned, bows will be deflected

Question 4

Interaction in Narrow channels

Answer 4

Vessels should pass at as slow a speed as possible to minimise interaction with each other, banks, and shallow water

Also allows for extra thrust if needed to counteract interaction forces

Question 5

Bank effect (Bow cushion effect)

Answer 5

Bow wave pressure shears bow away from bank
LP at the stern sucks stern towards the bank

Counteract by steering towards the bank, counteracting the shearing force of the bow

Question 6

When berthing/mooring, what do we do in relation to the tide?

Answer 6

STEM the current

Question 7

When forced to berth with the tide from astern with a single screw vessel, what do we do?

Same goes for leaving the dock with heavy tide/wind on the beam on a single screw vessel.

Answer 7

Call for TUGS

Question 8

How to SNUB around

Answer 8

With current behind, drop leeward anchor

Allow tide to push vessel around and the wind to continue the swing of the vessel

Pick up anchor and drive out on the reciprocal

Question 9

Short Round

Answer 9

Port side of channel

Hard to STBD

Midhsips, full astern

When way comes on astern, stop, full ahead, wheel to stbd

Wheel to midships when on reciprocal course

Question 10

Open Moor

Answer 10

Stem the tide

Drop windward anchor, 2x amount required

Move transversely until anchor tight

Drop second anchor

Settle the difference by bringing in the 1st anchor until scope of chain required is met

Question 11

Running Moor

Required when tidal waters risk lifting the vessels anchor

Answer 11

Drop 1st anchor, windward side, 2x chain required

Drive up into the tide, drop second anchor

Drive back and settle in the middle, bar tight on both

Question 12

Standing Moor

Answer 12

Same as running moor, but start with high side of the tide first, and let the tide drift the vessel back

Then settle in between

Question 13

What is Squat?
When is it most critical?

Answer 13

Hydrodynamic interaction between the bottom and the vessel
depth >1.5m of the draught of the vessel

Draws the vessel to the bottom, resulting in difficulty steering/sheering

Question 14

Factors effecting squat:

Answer 14

Ships speed

Type of bow

Position of the Longitudinal Centre of Buoyancy
If aft, Squat by the stern expected.
If Fwd, Squat by the head expected