Moving boat sideways

[BobH]

It seems a while ago I ran across a U-Tube video about moving a twin screw boat sideways. But I can't find it anymore. I seem to recall it involves moving one engine back and forth between forward and reverse. Maybe both? Can any of the experts on TF explain the maneuver?

Thanks,

Bob
(Still trying to learn how to drive this twin engine boat. Seems our single screw sailboat was easier to maneuver.)

 

[MYTraveler]

Turn the rudder the opposite of the way you want to go, then alternate between port in fwd, stbd in reverse and vice versa. Depending on the boat, that may not be enough to overcome wind and current.

There is a more advanced technique in which engine rpm are varied.

 

[hmason]

Is it always port in forward and starboard in reverse or does it change to move in the opposite direction?

 

[MYTraveler]

Is it always port in forward and starboard in reverse or does it change to move in the opposite direction?

The way I do it, you have to switch back and forth between port forward, starboard reverse. The only changes with direction is rudder position.

 

[hmason]

I'm trying to visualize this. If the rudder is hard over to starboard and I put the port engine in forward, the bow will turn to starboard. Then, I put the starboard engine in reverse and the stern will move to port. Seems to me I'd be making a circle?

 

[rardoin]

As far as twin screws I've only had experience in sportfishers but to "walk" the boat to starboard I would put the rudders hard to port...and leave them there. I then put the port engine in forward (if the stbd is kept out of gear the bow would move forward and to port while the stbd aft quarter moves to stbd and fwd) and the stbd engine in reverse. The stbd engine halts fwd motion and the port prop walks the back of the boat to stb. If the bow wants to move to port I would add/drop stbd throttle (or fuel lever for you pedantic purists) to control the bow. Of the half dozen different boats I have done this on they all seem to react differently so practice with your boat in windless conditions in a safe area. Also the heavier the boat the easier it seemed to me.

 

[MYTraveler]

If you keep the rudders centered, the boat will start to pivot to starboard (port gear forward, starbord reverse), and when you switch (to port reverse/starboard forward), it will pivot back to port. By putting the rudder hard to starboard, the bow of boat will pivot more to port when the starboard engine is in gear. The net effect would be to walk to port.

 

[hmason]

I can't wait to try this. I'll try it out when nobody is around to watch. If it works, I will win many a bet.

 

[BobH]

I'm more confused than ever. It's the windless conditions I have problems with. There never seem to be any. This boat with the full enclosures seems to have more windage than the sailboat we had with the sails up.

Seems to me to move to port, rudders to port, port engine forward will move the bow to port, stern to starboard. Then port in neutral and starboard in reverse, the starboard propwalk will move the stern to port. Not so?

 

[Marin]

While this may work with some twins, it's been our experience with ours that it doesn't work at all. Not if what's being talked about is moving the boat straight sideways as though it had bow and stern thrusters. The boat can be "walked" sideways easy enough, but not moved straight sideways. (This is assuming that the boat does not have a bow thruster but is being moved and directed by the props and rudders alone.

This came up in a discussion years ago with friends at an island we used to visit a lot. The husband had been a fantastic boat handler in the USCG (he is still the best boat handler I have ever met) and he was sure that a twin could be moved straight sideways using the techniques described earlier in this thread. I'd tried them with no success but he is far better at maneuvering than I was then.

No luck at all. He tried everything he could think of and in the end he said it's impossible. The boat can be made to move straight sideways for couple of feet, but that's just until the forces at play take over and one end or the other starts moving to the side faster than the other.

Now in a twin with very widely spaced props like a Great Harbor it might be possible because of the leverage that can be exerted by the props. But in a boat like ours, with the props fairly close-in to the keel, not gonna happen.

Again, it can be walked sideways very easily: move the bow over, then move the stern over, then the bow, and so on. My dog can do that. Blindfolded. But straight sideways? No way. The physics simply aren't conducive to it.

And FWIW, I have yet to meet a twin operator who has claimed and demonstrated he/she could do it, either, at least not with their boat.

 

[hmason]

Marin, I have tried and tried with my GB and could not make it happen either, all though I must say I haven't tried in a long time and may have done it wrong. I'll try again.

In terms of walking it sideways, just how does your dog do that maneuver,using 1 engine or both? ��

Thanks, Howard

 

[Marin]

In terms of walking it sideways, just how does your dog do that maneuver,using 1 engine or both? ��

As I said, it's an extremely easy thing to do. He uses both engines and the rudders as well as differential power. The only thing he needs help with is turning the wheel from lock to lock because he is not a particularly large dog and the diameter of the wheel exceeds his reach. But he simply tilts his head in the direction he wants the wheel to go and one of us turns it around for him.

The photo below was taken while we were docking one day and he was watching the person at the helm, shaking his head in disgust at the inefficient manipulation of the controls.

 

[rardoin]

Then port in neutral and starboard in reverse, the starboard propwalk will move the stern to port. Not so?

Let's assume you want to walk the boat to starboard to a dock. In this case I put the rudders hard to port (opposite of direction I want to move toward), port engine in forward, idle speed. Typically I would not alter rudder or port engine throttle after that. Put the starboard engine in reverse and alter stbd throttle setting to keep bow straight ahead and usually boat moves to starboard with little forward or reverse motion. Some boats would require the stbd throttle to stay at idle and I would slip the gear in and out forward to keep all motion lateral. Like HMason wrote...find a spot all by your lonesome and practice. I learned on a 26 footer. My dad ran the boat out when on offshore trips and he would let me run it in. The most fun I had was pulling her up to the fuel dock and walking the boat like a pro...of course when things went textbook. When you get it figured out on your boat in ideal conditions then you'll be able to get the wind and current problem solved to...just takes practice.

 

[rardoin]

Marin...I thought he was just disturbed at my reference to throttles. Actually, in the case of the first twin I ran it had gasoline engines so it fits.

 

[Edelweiss]

Good idea!!

But don't expect the boat to just "jump sideways" to the dock, like a bow thruster. The effect on the bow is much less dramatic than the effect of moving the stern by counter shifting the port and starboard engines. In a perfect world, where there is no wind or tidal effect, the boat would glide to a stop parallel to the dock and allow you to take your time and walk it slowly in, but it's rare that you have those conditions.

Real world you're probably going to approach the dock at minimal speed, with a bow "in" angle and then reverse the outside engine, maybe a little forward thrust with the other, to move the stern to the dock as you come to a stop.

If you haven't already done so, before you practice docking you need to find the pivot point of your boat. It's probably a few feet somewhere behind your bow. (Mine is just ahead of the salon door.) Take your boat out on a calm day and find a buoy or a dolphin to use as a fixed reference point. Point your bow at it and put one engine in reverse and the other in forward. (The reverse engine will probably need a little more throttle to stop forward movement.) Note how your boat rotates around it's pivot point in relation to the reference point. That's your pivot point and knowing that will help you visualize how your boat will "probably" move when you approach a dock and apply different thrust techniques.

Now add wind and tide to that and all bets are off!!

 

[Marin]

We dock our boat the same way we dock a floatplane. Angle in to the dock nose (bow) first at a 30 degree angle give or take.

In the case of the plane all one can do is put in (water) rudder when the tips of the floats are almost to the dock and straighten out parallel to the dock and then jump from the inside float to the dock as the plane slides along it and pull the plane to a stop with the forward mooring line.

With a boat we get the bow right up almost to the dock and then stop the boat and pull the stern in with the combined propwalk from opposing the thrust of the props. We also use the rudders to help move the stern in. Adding power on the appropriate engine will help counter the forces of an adverse current or wind up to a point. Beyond that point we start thinking about making more aggressive use of a spring line or using some other technique.

But we have never been in a position where moving the boat straight sideways up to a dock was something we actually needed to do. We have just played with it to see if it could or couldn't be done.

 

[rardoin]

Marin, do you figure a P-38 Lightning on floats could do the sideways shuffle with reversible pitch props? That would be a sight!

 

[Marin]

Comparing a floatplane to a boat is a futile exercise because the forces acting on them in/on the water are very different.

 

[caltexflanc]

In my experience, the flatter the bottom the easier this is to do. I could do this on my Hatteras, but with its deep keel it is not nearly as easy on a Mainship: you could accomplish it by merely turning the rudders away from the dock and jockeying the engine farthest from the dock in and out of forward and reverse. Came in real handy once when we lost an engine.

 

[Bacchus]

One item mentioned that affects ability to do this successfully is prop position another that I have experienced that can have a major impact on success is whether your props are recessed in a tunnel. The larger the prop tunnels the less successful you will be... Tunnels reduce the prop walk affect.

Don
'08 MS 34 HT
"Bacchus"

 

[Sailor of Fortune]

"Real world you're probably going to approach the dock at minimal speed, with a bow "in" angle and then reverse the outside engine, maybe a little forward thrust with the other, to move the stern to the dock as you come to a stop."
This is incorrect.
If you want to walk to a port side moor, come in at an( bow towards) angle (slowly) and turn your helm to STBD (away) from dock while backing the port engine and ahead on the stbd (outboard engine). The momentum of the turn away from the dock and the prop wash against the rudder will be your friend.
Watch any busy commercial dock with crew boats tugs and other work boats maneuvering and you will see it over and over. Most boats will walk to some degree. Prop rotation plays a part as well. Inboard turning wheels walk much better that outboard turning wheels.

 

[High Wire]

One item mentioned that affects ability to do this successfully is prop position another that I have experienced that can have a major impact on success is whether your props are recessed in a tunnel. The larger the prop tunnels the less successful you will be... Tunnels reduce the prop walk affect.

Don
'08 MS 34 HT
"Bacchus"

Agree. My old Phoenix had prop tunnels and would not go sideways without significant throttle jockeying. It just was not worth the risk of a mistake.

 

[Marin]

Real world you're probably going to approach the dock at minimal speed, with a bow "in" angle and then reverse the outside engine, maybe a little forward thrust with the other, to move the stern to the dock as you come to a stop.

The above description is how it works (and how we do it) with a boat with counter-rotating props with the port prop being a right-hand prop and the starboard prop being a left-hand prop

In the case of a final approach and docking to a starboard tie, with the outside (port) prop turning in reverse and the inside (starboard) prop turning in forward, both props will be turning clockwise so the combined propwalk will move the stern to starboard (toward the dock).

Putting the rudders over away from the dock (helm wheel in a port turn) the forward thrust of the inboard (starboard) prop against the rudder will add to the propwalk to move the stern even faster to starboard.

(Of course the bow will move to port when you do this because a boat pivots somewhere along its length, so you want to be pretty close to the dock when you initiate this or you'll end up with your stern against the dock and the bow drifting out away from it.)

If the approach and docking is a port tie, then the above control positions are reversed.

The fellow who first taught me to maneuver a twin engine boat gave me a great analogy which helped me remember how to manipulate the shifter levers to get the desired movement of the stern until it became second nature and I didn't need the analogy anymore.

He asked me if I'd ever driven an old-fashioned bulldozer (with lever controls for each tread, not a single joystick). I had so he said to imagine the boat the same way. With both treads shifted to forward, the tractor goes forward. With one tread shifted to neutral and the other in forward, the bulldozer makes an easy turn toward the unpowered tread. With one tread in forward and the other tread in reverse, the tractor pivots toward the tread that's in reverse.

So, he said, think of the shift levers as the tread controls and your butt as the back end of the tractor (boat).

My wife was taught a slightly different analogy, one that is probably even easier to envision. With her arms clamped tight against her sides and angled forward at the elbows, pushing her right arm forward twists her body to the left and her butt pivots to the right. If she pushes her left arm forward, her body twists to the right and her butt pivots to the left.

If she pushes one arm forward and pulls the other arm back her body really twists toward the arm coming back while her butt pivots a lot more toward the arm moving forward.

The boat reacts exactly the same way.

This is why a bow thruster is a great tool if you have one because it's the only way, single or twin, that you can move the bow straight sideways one direction or the other and leave the stern exactly where it is. We don't have a bow thruster and have gotten along okay without one, but there have been times when the ability to move the bow but leave the stern right where it was would have made things easier and faster.

 

[markpierce]

I have round fenders at the boat's "corners" for hull protection when leaving or arriving at dock at an angle.

With a single propeller and a bow thruster, sideways movement can be achieved with a bit of shuttling. When moving to starboard, the rudder is set to port and idled engine in forward gear while the thruster is set for starboard movement. Forward motion is reversed by changing to reverse gear.. Going to port is done with the opposite directions. With my starboard propeller walk, moving to starboard is easier since in reverse the stern tends toward starboard.

 

[Sailor of Fortune]

Marin
The reason it is not working for you is you have your engines backwards. Stbd tside moor should be helm away (port, you have that correct) and stb eng reverse, port ahead, WITH SOME FWD MOMENTUM.

 

[cappy208]

True 'walking' sideways requires inboard turning wheels. To get a visual of how it works, Picture yourself standing behind your boat out of the water. (With inboard turning wheels). To walk to starboard you would use the port engine ahead and Stbd engine in reverse. The propellers would be turning clockwise( port turning inboard((ahead)) and Stbd turning clockwise ((astern)). The bottom of the wheels that are biting the water 'drag' the stern to starboard. The rudder is adjusted to the 'sweet spot' that keeps the bow approximately even with the stern. However the rudder on most yachts are not big enough to really help much.

What you are describing is not really waking, but just twisting and wiggling. Boats with outboard turning wheels do not walk but use the ahead engine with opposite rudder to overwhelm the astern engine. This results in not walking sideways but skittering diagonally ahead as you approach a dock.

True walking is directly sideways. Some boats will never truly walk sideways against the wind or current. (Excepting thrusters).

 

[Donsan]

Are you certain it wasn't a pod drive? They can move sideways and there is a Youtube video demonstrating it.

 

[Edelweiss]

True 'walking' sideways . . . . . . . . . However the rudder on most yachts are not big enough to really help much.
What you are describing is not really waking, but just twisting and wiggling.

That is correct:

Unlike most single engine yachts and Commercial boats, most twin engine yachts use a small rudder (some exceptions noted). The spade rudder is fine for normal cruise speeds but has little effect at docking speeds. The engines are often used for maneuvering in tight spaces and marinas.

Since there is very little rudder surface to react against, the propeller side walk is greater than the wash against the rudder and the boat doesn't react as predicted. If that is the case and the wind or tide is pushing you away from the dock, you're unlikely to generate enough side thrust to push the boat back. Better off to back out of the slip and re-position for another docking attempt.

 

[Marin]

Marin
The reason it is not working for you is you have your engines backwards. Stbd tside moor should be helm away (port, you have that correct) and stb eng reverse, port ahead, WITH SOME FWD MOMENTUM.

The docking maneuver Eidleweiss and I just described works perfectly for us and has for the 17 years we've owned the boat. It's how we do every single docking we've ever done, in fact. Maybe you're thinking of a boat with the opposite prop arrangement. But our boat has counter-rotating props with the port prop being a right-hand prop (turns counter-clockwise going forward) and the starboard prop being a left-hand prop (turns clockwise going forward). (photo)

So to move the stern to starboard you put the starboard engine in forward and the port engine in reverse. This causes both props to turn clockwise which means the propwalk from both props is in the same direction and moves the stern to starboard. At the same time, the port engine in reverse is exerting some leverage on the boat to "pull" the port side of the boat back while the starboard prop in forward is exerting leverage to "push" the starboard side of the boat forward, which creates a pivoting moment which, when added to the propwalk effect moving the stern to starboard, makes the whole boat pivot counterlockwise (viewed from above) even more smartly and moves the stern even more smartly into the dock on the starboard side.

Then if you add rudder away from the dock, the forward thrust of the starboard propeller against the hard-over rudder directly behind it moves the stern even more smartly to starboard.

If we did with our boat what you describe, we would defeat the maneuver because the thrust against the rudder would be countering the effect of the propwalk.

If you're talking moving the boat straight sideways for anything more than a couple of feet, that doesn't work no matter what you try to do. And having forward momentum sort of defeats the whole notion of moving the boat straight sideways into a tight spot anyway, right?

Inboard turning wheels walk much better that outboard turning wheels

No they don't. Because when the thrust is opposed, both props will be turning the same direction assuming counter-rotating props. So one will be turning inboard and one will be turning outboard. Oppose them the other way, and one will still be turning inboard and one will still be turning outboard. So the amount of propwalk will be the same in either direction.

 

[psneeld]

Both work...as many things in boating...there's more than one way to do it.