prop walk

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What is Prop Walk?

Prop walk, also known as asymmetric blade thrust or paddlewheel effect, is the tendency of a boat's stern to be pushed sideways when operating in reverse with a single propeller. It occurs because the propeller blades travel a longer cylindrical distance on the upstroke compared to the downstroke due to the downward angle of the propeller shaft relative to the water surface. This creates more thrust on the upstroke side, pushing the stern sideways.

Factors Affecting Prop Walk

  • Propeller Rotation: A right-handed propeller will push the stern to port in reverse, while a left-handed one will push it to starboard.
  • Shaft Angle: A steeper downward shaft angle increases prop walk. Saildrives with parallel shafts experience minimal or no prop walk.
  • Propeller Type: Two-blade propellers generally produce less prop walk than three-blade props. Folding and feathering props reduce it further.
  • Speed and RPM: Prop walk is more pronounced at slow speeds and high RPM.
  • Hull Shape and Prop Clearance: The amount of clearance between the prop and hull, as well as the hull's shape, can impact prop walk.

Using Prop Walk to Your Advantage

While prop walk can make close-quarters maneuvering challenging, it can also be used as a tool for better control when docking or undocking.
  • Approach at an Angle: When backing into a slip, approach at a 20-40° angle with the stern leading towards the direction of prop walk (port for right-hand prop). As you engage reverse, the prop walk will help straighten the boat's approach.
  • Use Bursts of Power: Short bursts of forward or reverse thrust can be used to adjust the boat's angle and realign with the slip.
  • Practice and Timing: Mastering prop walk requires practice, timing, and understanding how your specific boat behaves. Start in open water before attempting tight maneuvers.
In summary, while prop walk can be challenging, understanding its causes and using techniques to take advantage of it can greatly improve your boat handling abilities, especially in close quarters.
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