Moving a twin engine boat sideways(?).

I have been enjoying the single engine prop walk thread even though much doesn't apply to my twin engine boat. However, it reminded me of something I read that I have yet to try out. That is that some twin engine boats (no thruster), using a balance of rudder, shift and throttle, can be made to move sideways (only).
I keep meaning to try this but, as I keep ending up at the dock easily using normal methods, it always seems to get forgotten.* I think I understand the theory. Lets say you wanted to move the boat to port without any forward/reverse motion or yaw. With the starboard engine in forward and the port in reverse the stern would, of course, move to starboard. But with the helm to starboard the prop wash on the starboard rudder would be counteracting that movement...to some degree. With the right balance, it would seem that the whole boat could be forced to port. I'm sure it takes a particular combination of rudder and throttles to achieve this...if it's actually possible.
It's probably not the most necessary skill, more of a useful trick in flat calm conditions. I do see it being handy in the locks, mostly to neatly get some clearance from the wall before exiting, but that's really not the best place to practice.
So...can any of you twin owners make your boat do this?


-- Edited by Tonic on Monday 8th of November 2010 02:16:22 PM

i havnt tried with my albin (screws) but have done it on a 40ft with twin jet pods, not really relevent. it is diffidently a awesome feeling. not as cool as the crash stop tho

one of our friends who is a licensed captain and does deliveries all the time explained to my husband how to do this but we have not been successful in getting our boat to respond as advertised.* I think we have tried it twice, just for fun.* If we are ever able to actually do it I'll let you know.

Both my previous ( 42' Dutch steel motorcruiser*) and current boat (55' trawler)*move sideways just nicely. Turn the wheel fully over to the opposite direction of the way you want to move the boat, slow astern on the side you want to move to, slow ahead on the other engine.
I use this trick all the time. Like the last weekend when we were to tie up alongside a floating pier and the wind was blowing us away. Coming into the marina, I had to do a 180 before approaching the pier. After the turn, we were at least 10 feet off the dock. I lined the boat up in parallel with the dock, then rudder hard to starboard, port astern, starboard ahead. As it was a stiff breeze I had to increase revs*from idle to*approx 1000 revs. It was a dignified affair. The boat slid in slowly.*

Doing this with a planing hull with*twin water jets is another game. I also skipper a 42' SAR vessel with twin 450 HP Yanmars.*With this setup*I have one hand on the water jet bucket controls and the other on the wheel. *The*bucket controls is for*controlling sideway speed and for*moving forwards/backwards. Wheel is for keeping her parallel with the dock.**This setup is way more responsive than my trawler.

Depending on your hull shape you can usually get it started with a little momentum, either fwd or reverse will do. As r-rossow said, back the engine on the side you want to go towards, ahead on the other engine and turn helm away from direction of desired travel.
This maneuver can be done by tugs with barges by twisting the bow of the tow towards the dock until you have momentun and then shifting the rudder the other way.

Vessels with inboard turning wheels are much better at this maneuver than outboard turning wheels.
As with the prop walk maneuver- practice practice practice. It is a thing of beauty when executed correctly and a horror show when you see someone winding their engines to try to get to the dock when a simple rudder/engine combo would have done just fine (single screw style).

r-rossow wrote:
Both my previous ( 42' Dutch steel motorcruiser*) and current boat (55' trawler)*move sideways just nicely. Turn the wheel fully over to the opposite direction of the way you want to move the boat, slow astern on the side you want to move to, slow ahead on the other engine.

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Thanks Roger.* Yeah, I understand where the controls would basically need to be.* I suppose some boats like yours might respond to simple hard over and idle on both screws, but I suspect most would need some fine tuning with the rudder and throttle settings.** Anyway...next time I go for a spin I'm going to force myself to try this out.* I'll start with the basic configuration and go from there if needed.* If I do get the boat to walk sideways, reliably, I can then make note of the indicated rudder angle and throttle settings.* And yes, I can see it would be a very nifty way of entering and leaving a crowded side-tie dock, but only if I had full confidence in my ability to repeat the manouver. *

*

I've heard all about this "move a twin sideways" business for years and after trying every method described, and having the best boat handler I know (an ex-USCG helmsman) try it on our boat (he had a theory of how to do it, too) I've come to the conclusion that it can't be done.* As did my ex-CG friend. *At least not a boat like ours with a deep keel aft.

I can "wiggle" it sideways by alternating thrust, rudder position, etc. But move it straight sideways? Not with our boat. There's too much underwater drag at the back compared to the front.* So it ends up cocked one way or the other*relative to the dock*no matter what combination of rudder position and thrust configuration one uses.* And this is in dead calm, no current conditions.

I've even had people tell me exactliy how they do it and then when they've demonstrated it to me, they couldn't do it either.

So I long ago chalked this up to armchair theory, at least with regards to boats with hull configurations like ours. A twin-engine planing hull with no keel and little underwater drag difference between the fore and aft portions of the hull, maybe it can be set up to work.* But I've never run a boat like that so can't say if it works or not.

-- Edited by Marin on Monday 8th of November 2010 07:29:28 PM

It can be done... but it is really boat specific. I have a bud that has a 80' fast passenger ferry that he can walk sideways into a 30kt wind... I have watched him do it dozens of times. His parking spot typically has boats rafted up to 3 deep in front of his spot and astern. He has about 5' of clearance on both ends. It is a thing of beauty to watch. Of course he has been doing this into the same spots for 15 years!. Last weekend he was with me on my new boat and tried it... 45' shallow draft twin screws... he couldn't make it walk sideways. The river current was about a knot and it may have been a factor. It is also a juggling act between rudder position and throttles.
HOLLYWOOD

I assure you it is real. A couple of Very experienced tug captains that i know were in a ship simulator class in Ft Lauderdale. They asked the instructor if the small navy ship that was being demoed would "Walk" the instructor said absolutely not and dismissed the 2.
They were not to be put off so easily, after all the ship simulator is supposed to produce real life
results.
When they got it to walk, the instructor was dumbstruck and making excuses as how it wouldn't work in real life etc.

some of the sweetest handling boats are crew boats. They can be made to dance.

hollywood8118 wrote:

It can be done... but it is really boat specific. I have a bud that has a 80' fast passenger ferry that he can walk sideways into a 30kt wind...

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"Walking" a boat sideways is, in my definition, different than moving it straight sideways.* "Walking" to me is working it sidways in a series of moves, each of which results in the boat angling a bit and then the next "step" angles it the other way, with a cumulative motion of the boat moving laterally toward the dock.* That's not what I'm talking about-- I can do that easy enough.

I'm talking about this claim that people have that a twin can be moved straight sideways, as though it had bow and stern thrusters. by angling the rudders one way and using differential thrust.* That's what I've never seen work, at least not in boats configured like ours is.

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Marin: keep trying. My boat has at least as much deep keel aft as yours, so that isn't a factor.
I use that manouvre almost every time I come in to my shelter, as with a tight turn from the fairway I almost never get it exact, so I need to move the bow away from the first post, or risk marring the varnish, so the best way to do that is to walk the whole boat a little to the other side. So yes, I do get some practice, and I get to know exactly where my boat is going to move with a little more, or a little less throttle, as the shelter posts are a reference point.

Marin wrote:

*
hollywood8118 wrote:

It can be done... but it is really boat specific. I have a bud that has a 80' fast passenger ferry that he can walk sideways into a 30kt wind...

Click to expand...

I'm talking about this claim that people have that a twin can be moved straight sideways, as though it had bow and stern thrusters. by angling the rudders one way and using differential thrust.* That's what I've never seen work, at least not in boats configured like ours is.
Ok so let me be a bit more clear..... he can bring his boat within 10'-30' of the dock and be parallel to the dock... and can move the boat absolutely SIDEWAYS with less than 5' of clearance off the bow and stern. The boat might "yaw" a bit , but he corrects this with rudder position. no see/saw movement at all... parallel to the dock SIDEWAYS. I have been on the boat in over 25kts of wind off the dock and he still does it.... it pisses me off how easy he makes it look.* I could do a version of this on Volunteer using the rudder turned away from the dock to push the stern to the dock .. while bow thrusting to the dock... with some reverse to keep the boat from going forward... but not in a beam wind off the dock!
HOLLYWOOD

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koliver wrote:

Marin: keep trying.

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Sorry, I don't believe it can be done with a keeled trawler-type vessel.* "Walking it," moving one end and then the other, sure.* But straight sidways as though using a bow and stern thruster together?* Not for any distance more than a couple of*feet if that.* Sorry, I don't buy it.* I've never seen it done in this type of boat and the people who've*said, yes, I do it all the time and then demonstrated it actually walked it, first the stern sideways, then the bow sideways, etc.* Hell, my dog can do that.

But straight sideways into a dock from a decent distance out?* The physics are against it I think.

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hollywood8118 wrote:...using the rudder turned away from the dock to push the stern to the dock .. while bow thrusting to the dock...*
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If you have a bow thruster to move the bow sideways while the rudder and prop thrust is moving the stern sideways, hell, my dog could do that, too.

I'm not talking about a twin with a bow thruster. I'm talking about these people who claim you can move a twin straight sideways with just the props and the rudders.* I maintain it can't be done in a keeled trawler, and I've seen every possible combination of thrust and rudder tried and none of them work as claimed.

The only trawler-type boat I've ever seen do this is a Grand Banks 41, and they do it with a pair of pod drives that can rotate independently*and are controlled by a computer.* THAT I'll buy into, and like I said, I've seen it work.

Now if a twin engine boat has it's props mounted way at the ouside corners of the stern where they can provide a lot of leverage, maybe.* Like a Great Harbor.* But on*a GB, CHB, etc. where the props are mounted fairly close to the keel, not gonna happen.* That configuration can't develope enough leverage with differential thrust**to overcome the thrust that's moving the stern.

This has been discussed ad infinitum for years*on the GB owners forum and nobody there can make it work, from amateurs like me to professional skippers.* The physics just aren't there on this configuration of boat.

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-- Edited by Marin on Monday 8th of November 2010 11:31:13 PM

Marin, I have done this to get to the dock between two pair of rafted boats, going sideways only, no fore and aft movement, the bow getting to the dock at the same time as the stern.
It requires a bit of concentration, and in my boat, no 10 knot crosswind.

Right, tomorrow afternoon I'm going to try it.Things may get ugly.

ON Most of the sport fish killers I have worked, the rudders are so small that the props will get the boat to do as you desire , regardless of the rudder position.

Its all about matching the turning force you get from the off side engine in fwd, pushing against the rudder that would turn your bow away from the dock and move your stern towards the dock, with the propwalk of the near side engine in reverse, that holds the stern from approaching the dock too fast, and the reversing thrust that keeps you from moving forward while you slide gently towards the dock. Takes a delicate hand on the throttles. Helm left hard over, gear levers left alone. If the motion is creeping forward or aft, a little throttle adjustment will correct that. If the stern goes in before the bow is ready, or vice-versa, it may be necessary to stop all and put the helm over the other way to straiten out, then reset and start again. This happens, but not too frequently.
I have even left the helm to go down to the dock with a line, while the boat steadily creeps towards the dock.
I suppose with speedboat rudders or no keel, the behaviour of the boat would be different. You just have to learn your particular characteristics and work with them.
The amount of side movement I get is not enough to counteract any significant crosswind or cross current.

Marin wrote:The only trawler-type boat I've ever seen do this is a Grand Banks 41, and they do it with a pair of pod drives that can rotate independently*and are controlled by a computer.*

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I've had a couple of good size twins in my past and have tried to maneuver them
sideways as described in this post. I've failed everytime. Having been on a GB 41
and watched the skipper do this was mind boggling. As Marin has stated, you can
accomplish this quite easily with pod drives but they use "resultant force" by turning
the pods at odd angles to one another and are, as he says, controlled by a
computer. To see a conventional twin do this maneuver, I'm from Missouri.

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koliver wrote:

Its all about matching the turning force you get from the off side engine in fwd, pushing against the rudder that would turn your bow away from the dock and move your stern towards the dock, with the propwalk of the near side engine in reverse, that holds the stern from approaching the dock too fast, and the reversing thrust that keeps you from moving forward while you slide gently towards the dock.

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Yeah, yeah, yeah, been there, done that, got the T-shirt.* That's the standard blurb that* the books and all the theorists say.* Doesn't work, at least not with our boat.

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Thanks all. So the answer seems to be yes, no, and maybe. The book did say "some" boats and it makes sense that a full displacement hull would be tougher than something flat. I would imagine rudder size/efficiency also come into play. Nothing left but to try it (next nice day I have the time). I'm still a relative newbie at this and, at worst, it will be good, additional practice. Even if my boat won't actually move directly sideways, I might find that it will do something else of use.

I'll let you know.

Tonic wrote:

Even if my boat won't actually move directly sideways, I might find that it will do something else of use.

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You will learn a lot, regardless of how your boat behaves.* It's far more important I think to learn what your boat does in such-and-such a situation than try to duplicate what someone else does (or theorizes about) with a different boat.* Our boat doesn't move directly sideways, period.* It doesn't even drift directly sideways in a 90-degree crosswind because above-water windage and below-water drag are not evenly distributed.*

So having found all this out a long time ago, it's a maneuver we don't even consider when faced with a close-in maneuvering situation.* What we do instead is use moves and techniques that DO work with our boat.* Some of these we were taught by boaters more experienced than us (like Carey who has given us some great docking advice over the years), some we pulled from previous experience--- our "normal" docking technique draws on our floatplane docking experience for example--- and some maneuvers we've discovered on our own.* So you'll learn a lot when you start "messing around" with maneuvering techniques.

One idea that might be worth pursuing with regards to trying various docking maneuvers (if you haven't done this already) is to do it open water using a floating cushion of some sort as the "dock."* You can't damage anything, you won't put anyone else's boat in jeopardy, and you can approach the thing from all directions, upwind, downwind, etc.* While not as good as using an actual dock, this open water maneuvering will at least give you a feel for how your boat responds to differential thrust and different rudder inputs, how fast (or slowly) it responds, and so on.* The floating cushion will give you visual reference against which you can judge your boat's behavior.

As Eric has said earlier, with practice you can maneuver anything




-- Edited by Marin on Tuesday 9th of November 2010 02:13:35 PM

Just a note on this "parallel" docking, which is what you doing when you attempt to move your boat sideways. With a single engine boat and a bow thruster, parallel parking is a breeze. You pull up along side the forward boat, hit your thruster to about a 45 degree angle (just like a car) and as you are backing you can adjust the angle with the thruster. When the stern is fully in to the dock and the bow has cleared the boat in front of you, just thrust the bow to the dock and your in. I have had to run a slalom course in reverse over the years to get my boat to the TraveLift at the yard. No panic, just hitting the thruster to keep me on the desired reverse course. It also compensates for any prop walk that might occur.

SeaHorse II wrote:

Just a note on this "parallel" docking, which is what you doing when you attempt to move your boat sideways. With a single engine boat and a bow thruster, parallel parking is a breeze. You pull up along side the forward boat, hit your thruster to about a 45 degree angle (just like a car) and as you are backing you can adjust the angle with the thruster. When the stern is fully in to the dock and the bow has cleared the boat in front of you, just thrust the bow to the dock and your in. I have had to run a slalom course in reverse over the years to get my boat to the TraveLift at the yard. No panic, just hitting the thruster to keep me on the desired reverse course. It also compensates for any prop walk that might occur.

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I don't get it. Why would you back in when you could do it forward? My single screw with thruster and a keel, drives in more or less like a car. I approach the opening ( given a space at least four feet longer than my boat, at a thirty to forty five degree angle, aimed at a point one third back in the space. When my bow is about six feet from the dock, I turn my helm all the way away from the dock and apply a couple seconds of forward thrust, wait until I am there, and apply a short shot of reverse to stop forward motion. If my bow starts to go off the dock at this point, then I give it a shot of bow thruster. Works every time, even with the wind blowing off the dock.

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-- Edited by Carey on Tuesday 9th of November 2010 03:45:46 PM

Carey wrote:
I don't get it. Why would you back in when you could do it forward?

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Since the reaction of the bow with a thruster is quicker that turning the helm, adding/retarding power or waiting for prop walk to occur, I have found that I have better controll, faster reaction and no helm needed when backing in to a tight spot.* Not to mention that if for some unforseen reason the space shrinks (overshooting, boat in front reverses, etc., your escape route is forward and you are already pointing that way. I had an expert 5 years ago show me this and it really stuck.

Sure, space permitting, go in bow first.


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SeaHorse II wrote:

*
Carey wrote:
I don't get it. Why would you back in when you could do it forward?

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Since the reaction of the bow with a thruster is quicker that turning the helm, adding/retarding power or waiting for prop walk to occur, I have found that I have better controll, faster reaction and no helm needed when backing in to a tight spot.* Not to mention that if for some unforseen reason the space shrinks (overshooting, boat in front reverses, etc., your escape route is forward and you are already pointing that way. I had an expert 5 years ago show me this and it really stuck.

Sure, space permitting, go in bow first.
Even in questionable space, it's been foolproof (and in my case that's a good thing). Not by choice, but rather my own mis-judgement of space, I have gotten into spaces just two feet longer than my overall length. I certainly wouldn't presume to say you should change your method. As to my doing so, I don't think I have a substantial enough thruster to make it work. I might try it sometime when I am forced to back down a fairway and then parallel park though. Thanks for the explanation.

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AllAs to prop walk, and how it's effecting your maneuvering, I must say I am dumbfounded. I run a 26"x24" five bladed screw powered by 420hp, and find prop walk so negligible that it is never under any circumstances a necessary part of my docking equation. I understand the principle, but have never found that it overshadowed the effects of the keel, rudder or inertia. But that's me and my boat.

With a 32 square wheel , and a rudder suitable for 12K, we can walk the stern with ease!

The one thing that nobody seems to mention that is at least as important as bowthrusters/sternthrusters/jet packs/pod drives and other assorted goodies is ENVIRONMENTAL.
Use the current to your advantage! Get the current on either side of your bow or stern to set yuo into the dock and feather as needed.
I've taught boat handling to many people and the women are way easier to get this concept than men.
Watch at a fuel dock sometime and see vsls approach with current behind them. Instead of tucking their stern in and letting the current set the stern to the dock, they will insist on turning the bow towards the dock ,letting the current grab them (and then yelling at the misses!)
This maneuver is called a fair tide landing (or "ferryboat" landing). Boats with bow thrusters are
the worst culprits on fairtide landings. Instead of thrusting away from the dock, they will insist on
thrusting towards the dock-all wrong when the current is on your stern.
Obviously approaching the dock INTO the current is most preffered method but not always possible.

Anytime you have to dock, try to find something in your favor-either wind or current if possible.
Technology is nice, but use ALL available means to the end (or at least be aware of them).

just my 2 cents worth

Sailor of Fortune wrote:

The one thing that nobody seems to mention that is at least as important as bowthrusters/sternthrusters/jet packs/pod drives and other assorted goodies is ENVIRONMENTAL.
Use the current to your advantage! Get the current on either side of your bow or stern to set yuo into the dock and feather as needed.
I've taught boat handling to many people and the women are way easier to get this concept than men.
Watch at a fuel dock sometime and see vsls approach with current behind them. Instead of tucking their stern in and letting the current set the stern to the dock, they will insist on turning the bow towards the dock ,letting the current grab them (and then yelling at the misses!)
This maneuver is called a fair tide landing (or "ferryboat" landing). Boats with bow thrusters are
the worst culprits on fairtide landings. Instead of thrusting away from the dock, they will insist on
thrusting towards the dock-all wrong when the current is on your stern.
Obviously approaching the dock INTO the current is most preffered method but not always possible.

Anytime you have to dock, try to find something in your favor-either wind or current if possible.
Technology is nice, but use ALL available means to the end (or at least be aware of them).

just my 2 cents worth

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Absolutely everything you say is true, yet so difficult for some to understand, considering all the variables. Perhaps the best way to describe docking is to say you must be aware of all elements of the process, and the physics involved. First, know your boat, and how it functions in static conditions, and then consider all the other factors. And the other thing none of has spent much time talking about is "escape". How do you escape if your attempted maneuver goes bad. If you haven't considered an escape route prior to your attempt, you are asking for trouble. And finally, when close maneuvering, never proceed any faster than you'd like to be going when you strike the boat next to you.*

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-- Edited by Carey on Wednesday 10th of November 2010 01:16:24 PM