Why the propeller rules the manoeuvre
Manoeuvring well under power is about understanding two things: that the rudder only steers when water flows past it, and that the propeller pushes the stern to one side. It is not an eliminating block, but it is one of the most practical, above all for berthing without scares.
Steering and way
The rudder deflects the water that flows past its blade; that is why it needs way (or the propeller wash) to have effect. Without water movement, the rudder barely steers. When you put the helm over to one side, the stern swings to the opposite side and the bow enters the turn.
The transverse thrust of the propeller
A single propeller pushes the stern sideways as well as forward or backward. With the most common propeller, the right-handed one (right-hand pitch):
- Engine ahead: the stern tends to swing to starboard (and the bow, to port).
- Engine astern: the stern swings to port (and the bow, to starboard).
The effect is most noticeable at low speed or with no way on, exactly during harbour manoeuvres; with good speed ahead it is barely felt. With a left-handed propeller (left-hand pitch) it is all reversed.
The standing turn (ciaboga): turning almost on the spot
The standing turn (ciaboga) is turning the boat almost on its own axis using the propeller effect. With a single right-handed propeller you turn better to starboard:
- Ahead with the helm to starboard, and before gathering way,
- Astern, taking advantage of the stern swinging to port (and therefore the bow continuing to swing to starboard).
- Repeat, alternating ahead/astern without letting the boat gather way.
With two propellers the standing turn is much easier: one ahead and the other astern.
The turning circle
When turning, the boat does not pivot on its centre: with way on ahead, the pivot point is located about one third from the bow, so the stern describes a larger arc on the outside of the turn. It is worth bearing in mind so as not to hit the stern when turning close to a quay or another boat.
The mooring lines
The mooring lines have names according to their function:
- Head/stern line (largo): leads forward or aft and holds the boat longitudinally.
- Breast line (través): perpendicular to the quay, it brings the side in.
- Spring (esprín): crosses forward or aft and stops the boat running ahead or astern.
- Back spring (codera): used above all for leaving the berth, pivoting the bow or the stern against the quay to push the other end out.
Berthing and leaving the berth
- Approach with the bow to the strongest element (wind or current): that way you steer better.
- Do it with a small angle and little way; you can always give a touch of engine, but you cannot stop dead.
- Put out a head/stern line first, and use the propeller and the rudder (and the transverse thrust) to bring the stern in.
The factors at play
Wind, current and waves deflect the manoeuvre. The force of the wind on the topsides produces leeway (a push to leeward). On the approach, always leave clear water to leeward, in case the boat sets that way.
How to study it
- Burn in the rule for the right-handed propeller: ahead, stern to starboard; astern, stern to port (most noticeable at low speed).
- Remember that a single right-handed propeller turns better to starboard.
- For berthing: bow to the strongest element, small angle, little way.