Drive a Boat

Question 1

What is Interaction?

3 types?

Answer 1

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

Results in pressure differences.

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

Pass at slow speed to minimise interaction

Question 5

Bank effect?

Answer 5

Bow wave pressure pushes bow away from bank

Low pressure at the stern sucks stern towards the bank

Counteract by steering towards the bank

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 (2 anchors)

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

Squat?

Answer 13

Hydrodynamic interaction between the seabed and the vessel
Bernoullis principle

Pulls the vessel towards the seabed

Affects steering

Worst when depth of water is less than 1.5x draught

Question 14

Factors effecting squat:

Answer 14

Ships speed

Shape of the hull

Question 15

What can we do to reduce squat?

Answer 15

Slow down