Module 13: Manoeuvring — OOW Oral Prep

Lesson 1 of 10 · 1 min

Propeller Effects — Single Screw

Understanding propeller effects is essential for predicting how the vessel will behave — especially at low speed when rudder effectiveness is reduced.

Effect	Right-hand propeller ahead	Right-hand propeller astern
Paddlewheel effect (transverse thrust)	Stern swings to starboard (bow to port)	Stern swings to port (bow to starboard) — stronger astern than ahead
Helical discharge current (wash)	Water discharged aft and to port — adds to paddlewheel effect	Water discharged forward — strikes the starboard quarter (the hull, not the rudder, which is abaft the propeller), pushing stern to port
Rudder effect	Effective when vessel has headway	Very limited astern — rudder in turbulent backwash

See it

Right-hand single screw: which way the stern goes

Ahead, the stern swings to starboard. Astern, it swings to port — stronger, and regardless of helm position.

5/5Right-hand single screw vessel going astern: the stern will kick to port regardless of helm position.Use this to your advantage when berthing — come alongside port side to and the astern kick swings the stern into the berth. Starboard helm helps only while she still has headway; once the way is off, the rudder does little.

Plan view, port side up · not to scale · the hull is not shown turning · your vessel's manoeuvring data governs

Say it out loud. Talk “Interaction — bank effect and ship-to-ship” through with the live Tutor.

Start a live lesson →

Lesson 2 of 10 · 1 min

Twin Screw Handling

Advantages

Can turn in own length — ahead on one screw, astern on the other
Transverse thrust effects largely cancel out — predictable astern movement
Better manoeuvring at low speed
Redundancy — can manoeuvre on one engine if one fails

Turning short round

Port screw ahead, starboard screw astern — vessel turns to starboard
Starboard screw ahead, port screw astern — vessel turns to port
Rudder amidships for clean rotation
Use thrusters if fitted to assist the turn

Say it out loud. Talk “Pivot point and transverse thrust” through with the live Tutor.

Start a live lesson →

Lesson 3 of 10 · 1 min

Effects of Wind

Situation	Effect
Wind on the bow	Slows the vessel — increases stopping distance. Bow tends to pay off downwind as speed decreases
Wind on the quarter / astern	Vessel tends to yaw — more rudder required to maintain course. Following sea can cause broaching
Wind on the beam	Vessel makes leeway — set to leeward. High freeboard (superyachts) increases windage significantly
Berthing with wind off the berth	Most difficult — vessel blown away from the berth. Use a bow line first, let the wind close the stern, or use a spring
Berthing with wind onto the berth	Easier — wind helps close the vessel. Control approach speed carefully to avoid coming in too fast

Say it out loud. Talk “Interaction — bank effect and ship-to-ship” through with the live Tutor.

Start a live lesson →

Lesson 4 of 10 · 1 min

Squat and Interaction

Squat

In shallow water, the flow of water under and around the vessel is restricted — creating a low-pressure zone that draws the vessel down
Vessel sinks bodily and may trim by the bow or stern
Effect increases with the square of speed — double the speed, four times the squat
Can significantly reduce UKC without warning — reduce speed well before entering shallow water
Trim depends on hull form: full-bodied hulls (block coefficient above about 0.7) tend to squat by the head; fine-lined hulls by the stern

Interaction

When two vessels pass in close proximity, the bow wave and stern suction of each vessel affects the other
In narrow channels: vessels attract at the bow and repel at the stern — creates a tendency to sheer toward each other
Passing alongside a moored vessel: suction effect can pull the moored vessel into the passing vessel
Overtaking (MGN 199): the vessel being overtaken may first take a sheer into the path of the other; abeam, the bows turn away and the sterns swing together, with an overall attraction between the hulls. The smaller vessel feels it most
Reduce speed when passing in confined waters — reduces interaction forces

Say it out loud. Talk “Interaction — bank effect and ship-to-ship” through with the live Tutor.

Start a live lesson →

Lesson 5 of 10 · 1 min

Anchoring Procedure

Step	Action
1. Anchor plan	Position selected — shelter, depth, holding ground, swinging room, clear of traffic. Master approves. Anchor party briefed
2. Approach	Approach into wind or current (whichever is dominant). Slow to bare steerage way before letting go
3. Let go	At the chosen position — anchor let go, cable veered out under control as vessel drifts back
4. Scope	3× the depth at high water minimum for good holding. More in heavy weather. Deckhand counts shackles and reports to bridge (each shackle = 27.5m)
5. Confirm holding	Take cross-bearings immediately. Monitor for drag. Vessel should face into wind/current and lie steady
6. Exhibit lights/shapes	Anchor ball by day, anchor light by night

Say it out loud. Talk “Pivot point and transverse thrust” through with the live Tutor.

Start a live lesson →

Lesson 6 of 10 · 1 min

Mooring Lines — Purpose and Names

Line	Position	Purpose
Head line	Forward, leads ahead from bow	Holds bow to the berth
Forward breast	Forward, leads at right angles to the vessel	Holds bow close to the berth — no fore/aft control
Forward spring	Forward, leads aft from bow to a shore point aft	Prevents vessel moving forward along the berth
After spring	Aft, leads forward from stern to a shore point forward	Prevents vessel moving aft along the berth
After breast	Aft, leads at right angles	Holds stern close to the berth
Stern line	Aft, leads astern from stern	Holds stern to the berth

Say it out loud. Talk “Pivot point and transverse thrust” through with the live Tutor.

Start a live lesson →

Lesson 7 of 10 · 1 min

Turning Short Round — The Single-Screw Sequence

Channel one and a half lengths wide, single right-handed screw, no thruster. Turn to STARBOARD — the propeller decides, because every phase then adds rotation the same way:

Phase	Action	What does the work
1	Kick AHEAD, full starboard helm — short burst	Prop wash over the rudder steps the stern to port, bow to starboard, without gathering real headway. The ahead kick's own transverse thrust pushes the stern the other way, to starboard, but the rudder force overwhelms it
2	Engine ASTERN, helm amidships	Transverse thrust walks the stern to port — the bow keeps swinging starboard — while taking off the way you made
3	Repeat, alternating	Each ahead kick with helm, each astern kick with the paddle-wheel — the same swing, fed from both directions

Say it out loud. Talk “Turning circles and stopping distances” through with the live Tutor.

Start a live lesson →

Lesson 8 of 10 · 1 min

The Thruster's Honest Envelope

Limit	Reality
Speed	Effective at rest to ~2–3 knots — above that the tunnel flow collapses and the thruster is noise
Leverage	Greatest with sternway or stopped (pivot point aft = long arm); weak making way ahead (pivot forward, short arm)
Wind	Do the arithmetic once for your vessel: windage area × 25 knots against thruster tonnes-force — most yacht thrusters lose
Endurance	Thermal cutouts arrive mid-manoeuvre when you have leaned on it; electrical load may shed other systems

Say it out loud. Talk “Bow thrusters and azimuth drives” through with the live Tutor.

Start a live lesson →

Lesson 9 of 10 · 1 min

Berthing in Wind — Two Plans, Not One Technique

Onshore wind

The wind berths you for free; the risk is arriving too fast and being pinned. Approach flat and slow, stop her a beam-width off with everything controlled, and let the wind lay her on — fenders early, lines fast smartly. Plan the DEPARTURE before arriving: spring off stern-first, thruster, or a tug when the forecast builds.

Offshore wind

The high-windage bow blows off the instant way comes off. Come in steeper, carrying way; first line ashore FAST — the fore spring — then power against it to walk her alongside. And know your honest wind limit: above it, the seamanlike call is a tug or a different berth, made out loud before the paint decides.

Say it out loud. Talk “Berthing and unberthing with wind and tide” through with the live Tutor.

Start a live lesson →

Lesson 10 of 10 · 1 min

Crash Stop — What Full Astern Actually Does

From full ahead, a crash astern is neither quick nor straight: the vessel carries her way for multiple lengths while the astern power builds, transverse thrust swings the stern (to port for a right-handed screw) so she finishes stopped ACROSS her original track, and steerage way is gone long before the way is. That is why the collision-avoidance answer is usually a bold turn, not the telegraph: a turn keeps steerage and moves the CPA immediately. The crash stop is for when there is no water to turn in — and its distances and behaviour for YOUR vessel are on the manoeuvring data card the examiner expects you to have read.

Say it out loud. Talk “Pivot point and transverse thrust” through with the live Tutor.

Start a live lesson →

Manoeuvring

Propeller Effects — Single Screw

Right-hand single screw: which way the stern goes

Twin Screw Handling

Effects of Wind

Squat and Interaction

Anchoring Procedure

Mooring Lines — Purpose and Names

Turning Short Round — The Single-Screw Sequence

The Thruster's Honest Envelope

Berthing in Wind — Two Plans, Not One Technique

Crash Stop — What Full Astern Actually Does

Check yourself

Oral questions