Physics of Docking - Pivoting

For additional details pertinent to this video please read the description below.

PIVOTING is the third video in our Physics of Docking series.

Jeff Merrill and Douglas Cochrane have collaborated to share their combined docking knowledge with other boaters through this series of videos. Filming for these episodes was done in San Diego, CA aboard a single engine Nordhavn 57.

There are two commonly used methods to pivot or rotate your single engine trawler, PROP WASH and PROP WALK. These were introduced in the previous episode, THE PROP, and now you can see them in practice in the PIVOTING video. Both actions work best in a “dead slow” or stopped position. By shifting in and out of forward/neutral/reverse you can learn how to control the speed of rotation and keep your circle within a small patch of water.

PROP WASH is used to initiate a turn by first moving your helm hard over and then giving a short forward gear blast. The angled rudder deflects propeller turbulence (wash) and pushes your stern to the side which simultaneously starts spinning your bow. PROP WASH can be used to spin your trawler in a tight circle, either clockwise or counterclockwise by pushing the stern - depending upon which way your rudder is turned. Giving a short blast of turbulence in forward gear and then shifting back into neutral initiates the spin.

PROP WALK is the “paddle wheeling” effect of your propeller in dead slow. Using your propeller to go backwards is inefficient for propulsion (the pitch is reversed) and the blades “crab” your stern sideways in the direction of the rotation. PROP WALK is only effective at very slow speeds as you must overcome forward inertia as this effect only works in reverse.

PIVOTING using short forward gear bursts, countered by a swift shift into neutral, then clicking in reverse is a combination of PROP WASH and PROP WALK commonly referred to when combined as BACK AND FILL. If you favor the forward blasts and hold position with subtle reverse shifts you can use this Forward/Neutral/Reverse technique to turn your trawler in circles. PROP WASH, PROP WALK, and BACK AND FILL are techniques that can give you better control. They are most effective at dead slow when their influence is more significant. You will be a more confident docker once you understand how you to apply these methods to your specific trawler and how it will ultimately behave.

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