Propeller walk, rudder, wind and current

The lesson in plain words

1. Flow makes it work
   • A rudder is an underwater steering blade.
   • Turn it and flowing water pushes your stern sideways.
   • Flow comes from movement through the water or propeller wash, the stream thrown by a propeller.
   • Here we mean a conventional shaft drive, with the rudder behind the propeller.
   • Ahead wash reaches the rudder; astern wash goes forward instead.
   • Stopped through the water in neutral, you have no useful rudder flow.
   • Swivelling drives steer by directing thrust, so they can steer astern before moving.
2. The kick ahead
   • A kick ahead is a short burst ahead with the rudder over.
   • Wash pushes the stern sideways before you gain much forward speed.
   • Rudder to starboard pushes the stern to port and turns the bow to starboard.
   • Reverse the directions for rudder to port.
   • Helm means your wheel or tiller, a lever attached to the rudder.
   • A tiller moves opposite to the rudder.
   • Use a brief burst and check the space around both ends.
3. Steering astern
   • Sternway means moving backwards through the water.
   • A conventional rudder needs this flow to steer astern.
   • On some yachts it begins to steer effectively at about 1 to 2 knots, but do not treat that as a fixed threshold.
   • Once it works, the stern follows the wheel.
   • A tiller moves opposite to the desired stern movement.
   • Hold either firmly: reverse flow can force the rudder hard over.
   • Keep sternway slow and use small angles.
4. Pivot point and swing
   • The pivot point is the point around which your boat appears to turn.
   • With headway, it is roughly one third of the length back from the bow; the stern swings widely opposite the bow.
   • As sternway builds, it moves aft, towards the stern, and the bow swings more widely.
   • Its position varies with motion and forces.
   • Check clearance at both ends: turning the bow away from a quay can swing the stern into it.
5. Rudder angle
   • Maximum efficiency is near 35°; a practical stop is about 32° (Marí Sagarra).
   • Excess angle can separate the flow, causing stall, less steering and more drag.
   • The exact response depends on rudder and flow.
   • Use small angles with sternway and hold the helm firmly.

Step by step

Try a kick ahead in clear water

1. 1Stop through the water with room around bow and stern. Both ends will move when you turn.
2. 2Put the rudder to starboard and give a brief burst ahead. Wash pushes the stern to port and turns the bow to starboard.
3. 3Return to neutral and watch your remaining movement. A short kick limits forward speed; it does not stop existing motion.

Key data

Key points

• No flow, no rudder steering; ahead wash can supply flow at rest.
• A kick ahead swings the stern before much forward speed builds.
• With sternway, the stern follows the wheel; a tiller moves the opposite way.
• Hold the helm firmly astern, and check clearance for both ends.
• Beyond about 35°, stall may reduce steering; the exact angle varies.

Check what you have read

True or false?

Practice case & exam keys

Exam keys

1. 1Rudder steering needs flow through the water or ahead propeller wash.
2. 2Kick ahead: short burst ahead with rudder over; rudder to starboard swings stern to port.
3. 3Astern with sternway, stern follows wheel; tiller moves opposite. Hold the helm firmly.
4. 4Pivot usually forward with headway, aft with sternway. Peak rudder efficiency near 35°; practical stop about 32°.