Physics of Docking - Pivoting

  Рет қаралды 58,464

JMYS - Trawler Specialists

JMYS - Trawler Specialists

6 жыл бұрын

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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Пікірлер: 40
@larrypatterson3957
@larrypatterson3957 5 жыл бұрын
Great information. Thanks for taking the time to share with us.
@JeffMerrillYachts
@JeffMerrillYachts 5 жыл бұрын
Thanks Larry, we appreciate you watching and commenting!
@larrypatterson3957
@larrypatterson3957 5 жыл бұрын
@@JeffMerrillYachts Hi Jeff - You certainly do a wonderful job showing all of your clients boats. I keep watching and if I win that lottery, you will be the third person I call (after the wife and my tax attorney). Until then, I will continue to watch and learn......and dream. Great job with your videos and your learning series is great as well! Take care.
@billyjay4672
@billyjay4672 5 жыл бұрын
Hi Jeff and Douglas. Very interested in what you are showing especially a landlubber like me I'm thinking seriously about getting into boating offshore.so I'm taking this all in and saving all your tips keep up the good work.and you never know you may see me sooner than later.
@JeffMerrillYachts
@JeffMerrillYachts 5 жыл бұрын
Thank you Billy Jay! There is a lot to take in and you are wise to be planning ahead. Please keep in touch and thank you for watching.
@user-xw2jj1ho2b
@user-xw2jj1ho2b 2 ай бұрын
Wow thanks I am a new boat owner and didn’t know how to pivot . I have a 41 ft
@JeffMerrillYachts
@JeffMerrillYachts 2 ай бұрын
Rodney: Glad you found this helpful!
@Wanderns
@Wanderns 6 жыл бұрын
Amazing. Tks for sharing
@JeffMerrillYachts
@JeffMerrillYachts Жыл бұрын
Thank you!
@cq7415
@cq7415 2 жыл бұрын
Good, explained nicely. Thanks for sharing.
@JeffMerrillYachts
@JeffMerrillYachts 2 жыл бұрын
C Q: Appreciate you watching, thank you.
@what8ever
@what8ever 6 жыл бұрын
Getting the boat moving backwards very slightly will also allow you to use that momentum against the rudder while in ahead.
@JeffMerrillYachts
@JeffMerrillYachts 6 жыл бұрын
Hi Nick, the momentum in that drift/coast zone at very slow speeds can definitely influence direction. Thanks for your comment.
@sailinstyle
@sailinstyle 5 жыл бұрын
isn't that a 55? Description says 57 but this boat has the usual Nordhavn reverse rake pilot house windows. The 57 and 50 are unique with motor yacht style pilot house windows, and other features that differ from the rest of the fleet.
@JeffMerrillYachts
@JeffMerrillYachts 5 жыл бұрын
SailinStyle - Very good observation and you are close. The boat we used for filming is one of only a handful of Nordhavn 57’s with the reverse raked pilothouse windows. The majority of 57’s and all 50’s have the aft swept (car windshield) wheelhouse windows. One way you can tell it’s a 57 is the flybridge is behind the pilothouse, not on top (like a 55). Also, the 55 has a single column fiberglass dry exhaust stack. All of the Nordhavn 57's have two shorter fiberglass columns outboard in the aft section of the flybridge. When a dry stack was ordered on a 57, the engine exhaust was routed to the starboard side stack. Those 57’s with wet exhaust (that was a popular new build option) have the twin stacks for consistency, but also more for styling (some engine heat ventilation runs up fiberglass columns too).
@sailinstyle
@sailinstyle 5 жыл бұрын
Wow, I had no idea they built a reverse-rake version of the 57! If I'd looked closer I would have spotted the dual outboard stacks and the position of the pilot house, and then I would have been really surprised!
@CheersWarren
@CheersWarren 4 жыл бұрын
Interesting , I would have preferred if you left the thrusters for a separate video. I have a 15' old inboard launch the prop walk is huge so much so that it drags the entire boat sideways , practically no pivoting . Shame as it makes it very hard to maneuver in close quarters which is when you need it! Going to take a lot more practice I guess to find a way. Cheers Warren
@JeffMerrillYachts
@JeffMerrillYachts Жыл бұрын
Thanks Warp 2. Obviously different handling characteristics between a 15' launch and a 57' trawler, but many of the principles are the same. Just about every trawler has a bow thruster now (few did 30 years ago) even sailboats are getting bow thrusters. Practice is the best teacher. Thanks for watching and commenting!
@theespjames4114
@theespjames4114 6 жыл бұрын
did I miss the rudder direction while pivoting ?
@JeffMerrillYachts
@JeffMerrillYachts 6 жыл бұрын
Hi James - at 6:15 I mention rudder hard over to back and fill, is that what you are asking about? Helm all the way to one side provides the best deflection of propeller turbulence. Thanks for watching!
@masterful7574
@masterful7574 5 жыл бұрын
JMYS - Trawler Specialists Just what exactly is propeller turbulence?
@SoundzAlive1
@SoundzAlive1 4 жыл бұрын
@@JeffMerrillYachts Yes I noticed that it was not made blear at the begining but was on the diagram. I always use the cat technique on my new Riviera dual engine cruiser. That is, rudder neutral and steer with throttle, so does this method have some advantages or disadvantages? I did see the trap that when you want to go ahead after the spin you have to correct the helm which I don't need to. André
@kenlee-97
@kenlee-97 4 жыл бұрын
@@masterful7574 it's just another technical terms for prop-wash or axial (straight) thrust.
@kenlee-97
@kenlee-97 4 жыл бұрын
@@SoundzAlive1 are you from oz?
@highliner250
@highliner250 5 жыл бұрын
Teach ...pivot-point ....transverse thrust , using external forces to your advantage ( wind ...current ). These forces work for all vessels big and small.....
@JeffMerrillYachts
@JeffMerrillYachts 5 жыл бұрын
Leonard, agree. Natural forces, wind, tide, current can definitely assist (or impede). Turning into the wind to hold your position instead of with the wind to drift down course. A lot to discuss. Thanks for participating with this.
@highliner250
@highliner250 5 жыл бұрын
My first boatven was a little 20 foot Clinker built with a one-lunger ( not even sure how many horses ) , it used to blow the most perfect smoke rings putting down the harbour. I have been playing and working on boats bever since . I have been working as a marine Pilot for twenty years , all ships great and small, the biggest was a Containership ( 385 meters Long ), the ships are approaching 400 meters now , they all handle the same ....pivot point, transverse thrust , wind , current .... my little boat was still my favorite.
@masterful7574
@masterful7574 5 жыл бұрын
JMYS - Trawler Specialists tide only goes up and down.
@kenlee-97
@kenlee-97 4 жыл бұрын
@@masterful7574 true, he's probably referring to tidal /currents ,as an effect of moving water in a certain direction. Cheers.
@joemast2984
@joemast2984 5 жыл бұрын
How does this maneuver work with counter-rotating props on single engine stern drives
@JeffMerrillYachts
@JeffMerrillYachts 5 жыл бұрын
Joe - I can't answer that from experience. Most trawlers do not have a stern drive and that is our primary focus. Most stern drives that I'm aware of don't have a separate rudder that you can "bounce" the wash off of to move the stern from side to side. Anyone with stern drive experience have a better answer for Joe?
@joemast2984
@joemast2984 5 жыл бұрын
Thanks for the reply. I didn’t know if this technique would work on a smaller boat.
@kenlee-97
@kenlee-97 4 жыл бұрын
@@joemast2984 Joe, a counter-rotating duo-prop design sterndrive will act exactly like a single propeller outboard engined boat, as the two props will counter act each propellers slight bit of prop-walk/transverse thrust IF there's EVEN ANY to begin with in the first place, as most sterndrives/outboard engines have propellers that don't produce any prop-walk/transverse thrust. Cheers.
@davidbentata8407
@davidbentata8407 3 жыл бұрын
Faire deux choses à la fois devient compliqués
@JeffMerrillYachts
@JeffMerrillYachts 3 жыл бұрын
David: Yes, “Doing two things at the same time becomes complicated” is true
@b.atwater3904
@b.atwater3904 5 жыл бұрын
I find it hard to believe that people that have money to buy high end boats can be so clueless on how to operate them. Guess you can't buy commonsense or experience. Some good tips here but Wow...
@JeffMerrillYachts
@JeffMerrillYachts 5 жыл бұрын
Benjamin, sorry, I missed your comment and this is a very late reply. Not everyone who buys a boat knows how to operate it, but most are very willing to learn. What may seem to be common sense is not always so, there is a lot to learn when you buy a boat and experience can be "bought" through time and effort. We realize that many already know a lot of what we are sharing, but to some it will be brand new and others a refresher.
@kenlee-97
@kenlee-97 4 жыл бұрын
@@preferredcustomer8273 best comment!
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