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Old 02-07-2016, 02:11 PM   #81
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If you visualize the prop as an automobile tire turning with its blades touching the "ground," you will immediately know in which direction the stern will move using that prop.
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Old 02-10-2016, 09:10 PM   #82
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Dramamine is recommended!

All these examples are only to twist or walk to port. I am not going to changing directions so as to try to make it clear how prop torque works, leaving it as a 'one sided example'. All of the prop torque comes from the bottom half of the blades. (as noted by an earlier poster who made the comment about the 'tires on the bottom'.)

Here is why boats with outboard turning wheels can't walk sideways. (without some outside force or help)

via Imgflip GIF Maker

In the above examples, the top video is both ahead, outboard turning.
via Imgflip GIF Maker
the second is backing the port, ahead on the stbd. the stern is being twisted to the starboard. The intent is to lift the bow to port, but you have to accept some stern slew the "wrong" way
All the prop torque is pushing the stern of the boat away from the dock.
The only way an outboard turning vessel can 'walk' sideways is using an outside force (bow/spring line, thruster, wind, current) to twist against to go sideways. But that is not walking, it is twisting, warping, springing, or breasting (depending upon which part of the world you learned your vocabulary from.)

The only thing that can be attempted (depending upon rudder size and horsepower) is to walk an outboard turning vessel by slewing it diagonally overpowering the backing engine with the ahead engine, but it is really influenced by wind and current more than an inboard turning vessel. And the progress is about at a 45 degree angle to the dock, making it impractical to dock in tight spaces as has been described earlier.



However, inboard turning wheels have two distinct attributes. Here is one of them.


Inboard turning wheels.

This is an example of inboard turning wheels, ahead propulsion.
via Imgflip GIF Maker


Now, here is the 'walk' laterally sideways.
via Imgflip GIF Maker


This is while walking to port, with approximately 10 to 20 degrees Stbd rudder. (the amount varies with wind, vessel characteristics, and rudder size.)

port backing, stbd ahead. Note direction of bottom of wheels, both are walking the stern to port. On a good walking vessel the stern will walk faster with the rudders used to balance the walk out to be even and in control.

This has little to do with space between wheels, depth of keel, or other physical attributes. It is all about the prop torque and how to harness it (or realize that you have NO prop torque to benefit from to walk sideways)



Sorry if the GIFs make you sick. They sort of all blend together after a while as I was making them!
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Old 02-10-2016, 11:36 PM   #83
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"The only way an outboard turning vessel can 'walk' sideways is using an outside force (bow/spring line, thruster, wind, current) to twist against to go sideways. But that is not walking, it is twisting, warping, springing, or breasting (depending upon which part of the world you learned your vocabulary from.)"

Sorry to bust your bubble, but in the last 21 years of driving my outboard turning (in fwd) boat, I have never needed anything but the shifters, to get my boat to spin on its helm, or to move the stern where ever I wanted it to go by applying a little reverse of the appropriate side. Using the rubber on the road analogy, if ever I want the stern to move to port, I apply a little starboard reverse, or if I want to move the stern to starboard, I apply a little port reverse. Always works. Never need a line to the dock.

The key is, in reverse, each side will always move the stern to the other side. When backing down the fairway, with both in reverse, steer by putting one side or the other into neutral until the boat staightens out, then both in reverse, with throttles at idle. Always works.

To get off the dock, put the side nearest the dock in reverse, the side away in fwd. twists the boat until the stern is outboard of the boat tied close behind, then both in reverse and away you go.
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Old 02-12-2016, 11:55 AM   #84
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You're not bursting anyone's bubble. I'm just trying to clear up the reasons 'why' inboard and outboard turning wheels perform differently.

Often (sometimes even in this particular thread) people who 'think' they know whether they have inboard or outboard turning wheels when they actually have the opposite! Then again, the concept of moving a boat laterally sideways (without a bow thruster or spring line) is an anathema to others. There is a difference between twisting the stern off, and walking the entire boat. Sometimes people want to actually know the 'how and why' (as the OP asked) of why their boat 'does this' when I back, or twin screw.

My intention is to share this info with others, not to seemingly contradict how you feel about running your particular vessel. You will not find this info anywhere in a yacht forum, because as you have so eloquently put it, "NO yachts have inboard turning wheels". This is not true. However, certainly the majority of yachts do have outboard turning wheels. But for those people who see 'something' done on another boat, and wonder: "Gee, why can't I do that with my boat?' This explanation may help them see the why.


The 'walking' of inboard turning wheel does not require twisting. The entire boat moves laterally (sideways) away from (or towards) the intended destination. Your comment only reinforces my explanation about how outboard turning wheels affect maneuvering.

Closing with an observation: If you have never operated a vessel with inboard turning propellers, don't knock that there are maneuvering characteristic differences between inboard and outboard turning vessels.

What you don't know isn't necessarily bad, or wrong. Just unknown.
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Old 02-12-2016, 01:10 PM   #85
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We used this technique on Crew Boats in the Gulf of Mex. 135 footers with 4 engines. We left the inside engines in neutral and just used the outside engines. Docking was so tight.
Boats would all be backed in. They were tied with 2 stern lines and then to each other. If you left. someone else would come right in. Basically bumping the boats on each side as you slid in. If you couldnt walk the boat, you would never be able to back in because the river current would spin you around.

It would be easier to explain how to do this if you had the space to lay up against the dock. Start by pulling parallel to the dock and come to a stop. Then turn wheel away from the dock (turn in opposite direction than you want to walk). Cross the shifters in Clutch (the detent position on the shifter which is idle speed and in gear) as if you were going to pivot toward the dock. It will take a few seconds before the boat actually reacts. it will then move sideways toward the dock. It will take some fine tuning adjusting the engine speed or taking one of the engines out of gear for a moment or two to keep the boat from going forward or backward.

This usually will only work with boats that do not have a real keel, so to speak. That is - a relatively flat bottom.

It works on my Mainship 36 on not so windy days. Problem is, I have separate throttles and shifters. The oil field boats all had one throttle/shifter for each engine. So much easier to control. Dont know why all boats aren't that way.
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Old 02-12-2016, 04:48 PM   #86
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The single lever throttles are the way to go. I don't know why so many companies installed them in he 80's. I want to change mine to single lever but the cost is too much to justify. Maybe next Christmas. I am looking at two consignment shops to see if I can find two used ones.
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Old 02-12-2016, 06:36 PM   #87
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Quote:
Originally Posted by BruceK View Post
I found and printed an easily understood demystifying article on "Walking Sideways" some time ago. Written by Capt. Alan Ross Hugenot, headed "Two For The Road",a footnote to the copied page reads "102 SEA / JUNE 2004. No idea where I found it, those interested, with sleuthing skills, check it out.
http://02eab56.netsolhost.com/images...EW_06-2004.pdf
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Old 02-12-2016, 06:36 PM   #88
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I am not a fan of single control levers...but like many things...what you get used to can become a favorite.
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Old 02-17-2016, 05:08 PM   #89
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When referring to a running diesel engine I was under the impression that idle meant the transmission was not engaged which is how you get definitions of high and low idle on a Diesel engine.
So you can run your Engine at wide open throttle at Idle
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Old 02-17-2016, 05:18 PM   #90
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To me "idle" refers to to the minimum throttle setting, whether the transmission is engaged or not.
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Old 02-17-2016, 07:09 PM   #91
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To me "idle" refers to to the minimum throttle setting, whether the transmission is engaged or not.
There is a big difference on the engine's load at idle between neutral gear and "engaged." "Idle" to me means minimum RPM and out of gear. Minimum throttle while transmission is engaged: we're talking no-wake speed.
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Old 02-17-2016, 07:30 PM   #92
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To me "idle" refers to to the minimum throttle setting, whether the transmission is engaged or not.
. But I need a higher idle speed in neutral for satisfactory lowest rpm in gear, so there are 2 idle speeds, one in neutral, one in gear.
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Old 02-17-2016, 08:02 PM   #93
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. But I need a higher idle speed in neutral for satisfactory lowest rpm in gear, so there are 2 idle speeds, one in neutral, one in gear.

Shouldn't be an issue with diesel engines because they are governor-controlled to maintain specified RPM as opposed to a throttle used for gasoline engines. Putting my diesel engine in gear does not alter RPM.
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Old 02-17-2016, 08:47 PM   #94
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Yes that's why A diesel is either idel or underload.
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Old 02-17-2016, 09:16 PM   #95
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We always referred to "idle" as "Out of Gear". A few extra words, but what the heck.
When you hit the first detent position in gear, we referred to that idle speed as "Clutch".
So when you were teaching someone how to handle the boat, the usual terminology was either " Put it in Clutch" or "Take it out of gear". This of course is assuming that additional power was not required.
When docking, speed or actually lack of, is critical. This is where the single lever is king. You shift and power up with the same handle. Imagine the nightmare with 4 throttle levers and 4 shifter levers. Or, sometimes even 6 engines.
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Old 02-18-2016, 12:09 AM   #96
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Shouldn't be an issue with diesel engines because they are governor-controlled to maintain specified RPM as opposed to a throttle used for gasoline engines. Putting my diesel engine in gear does not alter RPM.
Definitely happens with my old Lehman 120s. Your engine(John Deere?) and its controls are almost certainly more sophisticated. One rpm for no load, a lower rpm when loaded(in gear). For tight maneuvering I set throttle/rpm in gear, leaving throttle untouched while shifting in/out of gear.
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Old 02-18-2016, 05:07 PM   #97
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On engines with strictly mechanical governors they are set to low speed idle. (what ever the mechanic feels the set up requires). It depends upon the physical dynamics of the engine, gear, shaft, wheel. The newer electronic controls are customizable to have both high idle, low idle and an 'engage bump' so there is no staggering of rpm as it is engaged. I suspect most (if not all) the denizens here on TF have the ancient variety mechanical governors though! :-)
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Old 10-06-2016, 09:28 PM   #98
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i managed to get my boat walking sideways. i have a twin engine with counter rotating prob. how do i get it to slow down and drift sideways? i approached the dock sideways with the method and it was pretty fast, is it good enough to idle both engines and keep the wheel turned away from the dock or do i have to straighten the wheel.
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Old 10-06-2016, 09:39 PM   #99
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Rudder to midships the rudder is pretty useless until you gain enough headway. throttle would depend on what the setting is. What is the lowest rpm in gear? it may just be that the RPM is set to high to go any slower. The engine should have low and high idle. It can be adjusted.
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Old 10-06-2016, 09:56 PM   #100
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Quote:
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i managed to get my boat walking sideways. i have a twin engine with counter rotating prob. how do i get it to slow down and drift sideways? i approached the dock sideways with the method and it was pretty fast, is it good enough to idle both engines and keep the wheel turned away from the dock or do i have to straighten the wheel.
If I understand your situation correctly, you are concerned that your "walking sideways" happens too fast and you want to do the same manoevre more slowly.
If you staighten the wheel, your boat will pivot. It is the prop wash from the engine in forward that is keeping you from pivoting. That is couneracted by the prop walk of the engine in reverse, trying to move the stern away from the dock and holding the boat from moving forward. To Walk towards the dock, the prop wash must contribute a little more sideways motion than the walk of the other engine. Keeping things in balance requires a delicate hand on the throttles. If you can't slow it down, your engines may be idling too fast. You can try shifting into neutral, but not spinning the wheel.
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