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Old 11-08-2010, 01:11 PM   #1
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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
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Old 11-08-2010, 01:22 PM   #2
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RE: Moving a twin engine boat sideways(?).

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
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Old 11-08-2010, 02:18 PM   #3
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-08-2010, 02:27 PM   #4
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-08-2010, 02:45 PM   #5
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RE: Moving a twin engine boat sideways(?).

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).
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Old 11-08-2010, 03:30 PM   #6
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RE: Moving a twin engine boat sideways(?).

Quote:
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.

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. *

*
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Old 11-08-2010, 06:27 PM   #7
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Moving a twin engine boat sideways(?).

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
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Old 11-08-2010, 09:01 PM   #8
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-08-2010, 09:25 PM   #9
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-08-2010, 09:50 PM   #10
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RE: Moving a twin engine boat sideways(?).

Quote:
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...
"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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Old 11-08-2010, 10:02 PM   #11
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-08-2010, 10:14 PM   #12
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RE: Moving a twin engine boat sideways(?).

Quote:
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...
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!
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Old 11-08-2010, 10:17 PM   #13
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RE: Moving a twin engine boat sideways(?).

Quote:
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Marin: keep trying.
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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Old 11-08-2010, 10:27 PM   #14
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Moving a twin engine boat sideways(?).

Quote:
hollywood8118 wrote:...using the rudder turned away from the dock to push the stern to the dock .. while bow thrusting to the dock...*
*
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.

*


-- Edited by Marin on Monday 8th of November 2010 11:31:13 PM
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Old 11-08-2010, 10:28 PM   #15
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-09-2010, 12:54 AM   #16
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RE: Moving a twin engine boat sideways(?).

Right, tomorrow afternoon I'm going to try it.Things may get ugly.
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Old 11-09-2010, 04:53 AM   #17
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-09-2010, 08:19 AM   #18
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RE: Moving a twin engine boat sideways(?).

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.
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Old 11-09-2010, 09:35 AM   #19
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RE: Moving a twin engine boat sideways(?).

Quote:
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.*
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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Old 11-09-2010, 10:35 AM   #20
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RE: Moving a twin engine boat sideways(?).

Quote:
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.
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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