Prop Walk

[SteveK]

Though sailboats can go at trawler speed most of the time they are trying to get there. Small rudders are enough to deflect direction of travel at speed. Sailboats also use the large rudder at an angle of travel which aids in lift much like a plane wing along with a deep fin. At slower speed the large rudder is more responsive to steering which sail needs more. Larger rudder on power will not necessarily make much difference at slower speed, but will be a drag at cruise. IMO

 

[firehoser75]

The move from sail boat to power boat can, at first, be "surprising". When we picked up our new to us NT in Anacortes to bring her back to Canada, we had no experience handling a power boat of this size (even though the sailboat was basically the same size). My first docking attempt (at Deer Harbour) was "adventurous" to say the least. Turning radius, getting her alongside were both very different. The slip we were assigned required a sharp turn to starboard, bow in. This would have been very easy with the sailboat.

To me, the biggest things I learned through trial and error, a lesson with a large yacht Captain, and reading, are speed through the water, prop wash and walk, and an almost lack of steerage at slow speeds (in neutral).

We found that to turn in the smallest radius, first stop the boat (or very close to stopped), turn the rudder to the position necessary (usually hard over), and apply forward gear (often only at idle speed). If a sharper turn is needed, apply a very short burst of higher rpm. Forward momentum can be controlled by the duration of the burst (or forward application) and/or applying reverse gear to slow or stop. Sometimes we used a technique we called "ouching" that involved multiple (2 or 3) very short bursts in forward gear (starting from a stopped position) with the rudder hard over (first thing) followed by reverse to control forward motion. These "bursts" can basically "kick" the stern over in the direction of the turn a fair bit without producing much if any forward motion.

Our NT definitely turns more easily (certainly backs and fills) easier to port but it can be done to starboard as well. Our boat had moderate prop walk to starboard...... much more than our saildrive powered sailboat that had almost no prop walk.
Our NT could be backed in a relatively straight line, but it required "adjustments" along the way. EG. use reverse gear to get way on then shift to neutral (it backs straight in neutral which negates prop walk). To compensate for any unwanted sideways drift due to the prop walk (so for us to compensate for stern movement towards the starboard) turn the rudder to starboard and give a short burst in forward to "kick" the stern over to port without slowing reverse way appreciably. This "dance" ( a small "Z" pattern) in and out of reverse and using forward to adjust as needed, continues as long as needed to obtain a more or less straight path in reverse. Obviously the bow thruster can also be used to "steer" the bow where needed.
The main point is take the time to experiment under calm conditions and learn how your boat responds to various inputs. Maybe take a boat handling lesson from a "pro"?

 

[Shrew]

Your lower helm and helm door are to Stbd. If the boat back to Port I would be supremely annoyed. My Mainship backs to Stbd. If it backed to port I would have the direction reversed at the gear set, making it reverse to Stbd.

 

[backinblue]

Your lower helm and helm door are to Stbd. If the boat back to Port I would be supremely annoyed. My Mainship backs to Stbd. If it backed to port I would have the direction reversed at the gear set, making it reverse to Stbd.

But what if the finger for your slip is on your port as it is for me? I'm always stern in port tie up at my home slip.

 

[dhays]

Your lower helm and helm door are to Stbd. If the boat back to Port I would be supremely annoyed. My Mainship backs to Stbd. If it backed to port I would have the direction reversed at the gear set, making it reverse to Stbd.

My aft cockpit door is to starboard. Right hand drive causes my boat to walk to port in reverse. Furthermore, I back out of my slip to starboard, so the prop walk in reverse works against that. It can be a nuisance at times, but it works most of the time.

However, last week I took the boat to the pump out dock to pump out the holding tank. In my little harbor the current on an incoming tide causes the current to circle around the harbor counter clockwise. This, combined with a stronger than usual wind out fo the South, had both the current and the wind set me away from the dock.

The approach is a bit awkward because of the surrounding boats/docks. It took me 3 attempts before we were able to get a spring over a cleat and use it to bring the boat alongside the dock.

IF my boat backed to stbd, it would have been easier. Of course if I was a better boat handler, it would have been easier as well.

 

[Jarrow Lily]

Practice a bit until you get the hang of it.


The first ten years are the worst......................

 

[Sailinggod]

Prop Walk on Mainship 34

I have a 2007 Mainship 34 and have never noticed any prop walk. Mine has front and rear thrusters which operate quite differently, with the rear of the boat moving faster than the bow as the stern is flatter and seems to slide over easier.
Good luck learning how to maneuver in slow speeds. i find the Mainship to be very easy to control.
Cheers

 

[rherten]

My propwalk is a bit frustrating - I have a right hand prop, which means the boat tends to rotate clockwise in reverse. The helm and door are on the starboard side, so I naturally want to dock on the starboard side. Problem is when I come in to the dock and put the boat in reverse it pulls the stern away from the dock instead of towards it. Fortunately I have bow and stern thrusters but I hate to over-rely on those, especially on a windy day. I've had the boat 2 seasons and I still find this very challenging and frustrating - any advice?

 

[Sailinggod]

Frustrating prop walk

My simple recommendation is to rely on your stern thruster. That’s why they equipped the Mainship with bow and stern thrusters, to make it easier to dock them. I never resist using them, but I do resist using them for more than 5 seconds at a time, giving them a chance to stay cool.
While they won’t win against a strong breeze, which you will need some good seamanship or help on the dock to overcome, they do make life a lot easier.
hope that helps
Cheers

 

[Leo Reise]

We spent 50+ years on a sailboat and there most certainly is a difference in the way they handle compared to a trawler.
Reading the various replies, one thing is clear - handling your boat at slow speeds depends on your time at the helm and practice.
Our IG32 has a single LH 23x16 prop and a rudder area of approx 4 sq.ft. Prop walk is to starboard so yes - preferred dock is bow in - starboard lay.
We have, on a few occasions when visiting or taking on fuel or pump out, had to land on our "blind side", and thanks to my "line handler", EarTec, and good communication, we have been able to do so without too many problems.
Yes we have used "back and fill" and turned in our own length more than once.
That said, there were three times this season that our landing was not that graceful due to a cross-wind and gust at the most critical moment.

Our stern thruster arrives tomorrow for our first winter project.

 

[rgano]

My propwalk is a bit frustrating - I have a right hand prop, which means the boat tends to rotate clockwise in reverse. The helm and door are on the starboard side, so I naturally want to dock on the starboard side. Problem is when I come in to the dock and put the boat in reverse it pulls the stern away from the dock instead of towards it. Fortunately I have bow and stern thrusters but I hate to over-rely on those, especially on a windy day. I've had the boat 2 seasons and I still find this very challenging and frustrating - any advice?

Have you ever tried mooring stern-first? I don't have a stern thruster which with my right-handed-prop-in-a-tunnel with NO prop walk makes a bow first alongside mooring at PITA whenever the stern gets loose. I learned the stern-first method in the oil patch with a twin engine, BT-equipped offshore supply vessel, but it is very useful in this single engine, BT only boat. Slide the corner of the stern into where it belongs with the first mate there to hand over the line and push the bow in with the BT. Our 30 Pilot is very difficult for anybody to get back and forth from the bow, and I prefer to let the wife climb out of the cockpit aft onto the pier after the stern line is over and walk forward to secure the bow line which has been lead along the rub rail to the cockpit beforehand. It's all easier than messing about with a spring line, which we have practiced with just in case, but we pretty much need an assist from ashore getting the spring onto a cleat or piling.

 

[fcsorensen]

I went from a single engine Ocean Alexander 43 with the prop in the hole in the skeg. It walked wonderfully. Reverse took the stern to starboard.

Now I have a single 2007 Mainship 34 with the prop in a tunnel. It will not walk usefully in either forward or reverse.

That’s life.

Fred Sorensen
Treasure Island FL

 

[backinblue]

Yes, rely on your thrusters when you need to in short bursts. Doesn't make you any less of a man or a capt.

I have been practising w/o thrusters when conditions are right and once this season got pushed into a difficult spot due to a worse than anticipated river current after a heavy rain. I won't make that mistake again.

 

[rpackard]

prop walk

When I purchased my Willard 30 21 years ago, I noticed that the commercial fishing boats never had thrusters and maneuvered their boats in close quarters with no problems. Using prop walk (left hand prop so pulls to starboard in reverse) I have NEVER had a problem landing at a dock using the technique that Peter P. described

Prop walk is due to the curvature in the hull. When the stream off the prop ricochets off the curved hull it pushes it to one side. So hulls with little or no curvature will have no prop walk. That is one of the benefits of a true full displacement hull.

Personally I would not install thrusters on a boat due to the maintenance required in cleaning the prop and changing seals. But I need to keep my vessels as simple as possible due to the remote areas that I cruise in. If I purchased a boat that already had thrusters I probably would not remove them and would learn to love them.

 

[Choices]

You have only shifts in a transmission. Why waste them when you have a thruster?

 

[koliver]

Prop walk is due to the curvature in the hull. When the stream off the prop ricochets off the curved hull it pushes it to one side. So hulls with little or no curvature will have no prop walk. That is one of the benefits of a true full displacement hull.

I have heard this before, but...Aren't both sides of a FD hull curved? Doesn't the stream actually hit both sides equally?

My Semi Displacement hull, with twins where the props are aft of the keel by at least a foot, gets a great assist from prop walk in reverse. There is no curved hull close to the props. In fact, the props are far enough aft that the angle of the hull is as much or more fore and aft as it is sideways.
Prop walk allows me to effectively guide my travel in reverse by choosing which engine is engaged. Engaging the port engine in reverse pulls the stern to Starboard, the Sb engine pulls to Port.

 

[psneeld]

My hard chined, relatively flat stern 40 foot trawler has the most prop walk of any vessel I have run. Use it regularly in , maneuvering. My understanding asymmetrical trust of the prop accounts for a lot of walk.


Twins get the benefits of offset props from the centerline to accentuate walk.

 

[dhays]

My propwalk is a bit frustrating - I have a right hand prop, which means the boat tends to rotate clockwise in reverse. The helm and door are on the starboard side, so I naturally want to dock on the starboard side. Problem is when I come in to the dock and put the boat in reverse it pulls the stern away from the dock instead of towards it. Fortunately I have bow and stern thrusters but I hate to over-rely on those, especially on a windy day. I've had the boat 2 seasons and I still find this very challenging and frustrating - any advice?

I have the same issue. Sometimes it is hard.

Whenever possible, I try to approach so that I’m holding hard left rudder at the end. This will cause the stern to move to starboard and the reverse prop walk simply slows it down. When I do it right, all forward momentum is gone right as the boat lays up against the dock.

That is harder if you are pulling into a slip with little room. In that case you can’t angle into the dock to do the above. However, hard left rudder will still move your stern to Stb without causing too much forward motion. Just quick shift into forward will move that stern to the right. Again, when I do it right, it is wonderful.

However, there are times when wind and current conspire against you and the prop walk just makes it worse. That is when I’m really glad I have bow and stern thrusters and often wish they were more powerful.

 

[rgano]

A partial explanation of why prop walk happens was explained in US Navy texts as the hydrodynamic effect of deeper water on the bottom of a propeller. The reader was informed that the higher pressure at the bottom of a prop gave the blades there a better "grip" so that one might envision the propeller rolling along the bottom. Thus a left-handed prop in reverse pulls the stern to stbd.

 

[cbouch]

I have a single engine left hand prop and a large keel. I put the wheel all the way to port and by alternating the transmission from reverse to forward to reverse, etc, etc the boat will turn to startboard within its own length. It works, be patient. Attached is a picture showing the keel.

 

[Capt Dan]

Often the mark of a good boat handler is that only idle speed is used. This also makes things simpler as you only need to use the shifter, not the throttle. Practice it.
All that being said, there are cases when a little extra “shot” or “burst” of throttle is needed. Practice this to, and try and keep the burst to a controlled quick up and down of rpm. This can normally be done by ear and by feel, no need to watch the tach, keep your head on a swivel looking at the situation.

Never “speed shift”. Always pause in between ahead and astern. (Most electronic shifters build this pause in)

Every boat is different, tunnels, skeg extending to gudgeon at the base of the rudder vs no skeg may have a big effect. Size and type of wheel also a factor. Size of rudder a factor also. Many Trawler owners have increased the rudder size, or modified the shape.

Also check next time you are on the hard that your rudder swings equally one side to the other. When I purchased my boat this adjustment was way off.

Come to think about it, perhaps it should be slightly off depending on your prop size?

 

[backinblue]

I have a single engine left hand prop and a large keel. I put the wheel all the way to port and by alternating the transmission from reverse to forward to reverse, etc, etc the boat will turn to startboard within its own length. It works, be patient. Attached is a picture showing the keel.

This is all well and good and a worthwhile manuever to learn and practice. But it takes time to turn a boat that way and in some situations you don't have time. At my home slip I deal with tidal currents in a river. Depending on the weather and the height and timing of the tide, the current can be running very fast. When leaving my slip, I have to make a quick 90 degree turn or run into the next downstream pier. When doing that when the current is running strong (and possibly with wind too) if you don't make that turn very quickly and with decent headway, you will end up against the boats at the next pier. At times you have to actually "crab" your boat at an angle into the current till you clear the channel where the piers are lined up perpendicular to the current. If you have a single engine and no thrusters, you don't always get to come and go when you want to.

 

[psneeld]

Usually in situations that I can't turn into in time, I can back into them and sometimes back a fair ways out of the marina for the same reason.


I know most don't like doing this and may not have the skills to do this, but it's the way out when foreward doesn't work, then after that there are other tricks. As walking the bow through the current and unusual spring line use.


When one is a single with no thruster and on a working vessel with a schedule, one learns to be creative and does get the practice to improve.


But there are ways possible to maneuver.... though a thruster would be preferred.

 

[backinblue]

Usually in situations that I can't turn into in time, I can back into them and sometimes back a fair ways out of the marina for the same reason.


I know most don't like doing this and may not have the skills to do this, but it's the way out when foreward doesn't work, then after that there are other tricks. As walking the bow through the current and unusual spring line use.


When one is a single with no thruster and on a working vessel with a schedule, one learns to be creative and does get the practice to improve.


But there are ways possible to maneuver.... though a thruster would be preferred.

Thanks and I don't disagree. I am always docked stern in so it's always bow out first. I'm not a working vessel with a set schedule so I am glad to have thrusters when needed and not have to deal with spring lines or other methods when conditions are the worst. When conditions are not bad, I practice w/o thrusters, but I don't have a lot of prop walk anyway. Using forward and reverse thrusts I can get the boat to turn when the current is relatively mild.

 

[SteveK]

This is all well and good and a worthwhile manuever to learn and practice. But it takes time to turn a boat that way and in some situations you don't have time. At my home slip I deal with tidal currents in a river. Depending on the weather and the height and timing of the tide, the current can be running very fast. When leaving my slip, I have to make a quick 90 degree turn or run into the next downstream pier. When doing that when the current is running strong (and possibly with wind too) if you don't make that turn very quickly and with decent headway, you will end up against the boats at the next pier. At times you have to actually "crab" your boat at an angle into the current till you clear the channel where the piers are lined up perpendicular to the current. If you have a single engine and no thrusters, you don't always get to come and go when you want to.

Thanks and I don't disagree. I am always docked stern in so it's always bow out first. I'm not a working vessel with a set schedule so I am glad to have thrusters when needed and not have to deal with spring lines or other methods when conditions are the worst. When conditions are not bad, I practice w/o thrusters, but I don't have a lot of prop walk anyway. Using forward and reverse thrusts I can get the boat to turn when the current is relatively mild.

I was in a river marina and know what you are saying about currents and crabbing.
The last two posts tell me you should not be stern in but bow in.
You need headway to turn, water flow over rudder to steer. The current neutralizes some or all of that flow. Try bow in and back out. You should have more control bow to current.

 

[backinblue]

I was in a river marina and know what you are saying about currents and crabbing.
The last two posts tell me you should not be stern in but bow in.
You need headway to turn, water flow over rudder to steer. The current neutralizes some or all of that flow. Try bow in and back out. You should have more control bow to current.

I appreciate the advice, but I need to be stern in for boarding. I board on the swim platform or from the port side, but the finger for my slip is only about 12 ft long so bow in won't work. I'm at a yacht club and the slips are a little unusual. Some are just pilings, some have small fingers, so stern in is the norm except for some of the much smaller boats. Also note that the river is tidal so I get current in both directions but the worst is outgoing especially after a heavy rain.

 

[SteveK]

I appreciate the advice, but I need to be stern in for boarding. I board on the swim platform or from the port side, but the finger for my slip is only about 12 ft long so bow in won't work. I'm at a yacht club and the slips are a little unusual. Some are just pilings, some have small fingers, so stern in is the norm except for some of the much smaller boats. Also note that the river is tidal so I get current in both directions but the worst is outgoing especially after a heavy rain.

OK. I am trying to picture a 35 foot boat with 12 feet of dock. I see your problem.

 

[OldDan1943]

Prop walk, idle, creeper speed, back and fill and spring lines are your friends. Practice, practice, practice.

 

[backinblue]

Prop walk, idle, creeper speed, back and fill and spring lines are your friends. Practice, practice, practice.

But thursters are my BFFs! lol

 

[OldDan1943]

But thursters are my BFFs! lol

Of course unless your batteries are low or flat.