Noob question about twin engine

[Fish53]

Prop walk will help you control the stern obviously however on my single screw boats I have used the rudder to control my stern . controlling the bow with prop walk isn’t too effective forward motion will have control over the bow if you have a room for it. As far as twins One in forward and one in reverse using the throttles to control your forward or backward motion works quite well but I guess I’m not as sophisticated as you guys no I don’t worry about damaging the boat on the dock I’ve been running boats for over 40 years you do it your way I’ll do it mine I guess your way is your only way that matters anyways works for me may not work for you don’t know don’t care

I accept your apology.

 

[Scooby5959]

I'm afraid your knowledge of vessel maneuverability is somewhat lacking. I admit I have no experience with pushboats beyond the Mississippi where most use flanking rudders and push 1000ft tows. I won't bore you with a description of those, I'll leave it to you to educate yourself on that. Oil field supply boats are 175 to 300 hundred foot vessels used to, obviously, supply offshore platforms in the oil and gas industry in various places around the world. As the utility of having good maneuverability in confined space seems to have eluded you it would appear the why would be a waste of time. The how it seems is also foreign to you but in a simplified way I'll describe it for you. When a propeller rotates it creates asymmetrical thrust, especially in reverse where the bottom of the rotation effectively moves more water thus creates sideways thrust. This thrust and the resultant pressure against the hull as the blades reach closer to the top of rotation has the effect of moving the boat sideways. Now I know an accomplished seaman such as yourself has no need of such information but many of us mortals do. With a little way ahead on a twin screw supply boat and the judicious use of reverse on the inboard engine and the bow thruster it's pretty simple to walk a boat to the dock. with no fuss. the same goes for pivoting the vessel using bow thruster and opposing engines. I'm confident you can probably do this by using the strength of your will but the rest of us need help. I would suggest some reading material but that doesn't appear to worth the effort. As for your oddly ill-informed comment about "freighters" I'm afraid I don't have time or interest, get back to me if would like to discuss. I'm glad to answer questions or enter into a respectful discussion but when the demeaner of a comment seems more to create contention than conversation I'm afraid my sarcasm demons are lost from my control, please forgive them.

Your description of crop walk is my understanding is correct however he left out at KeyPoint crop walk also knees and ankles propeller so the washroom propeller is directed up towards the bottom of the hall I don’t know because I’m not a licensed push boat captain I don’t know whether you are not I kind of doubt it anyways from the pictures I’ve seen propellers look like there pretty much In line with the surface of the water therefore instead of using prop walk that you find so useful , I hate to remind you that I don’t .they have flanking Rudders to direct the prop wash in the direction that is beneficial to them . i stand by my statement that these boats do not use prop walk for maneuvering of their vessels . however It is true I have a limited experience with commercial push boats. I’ve been on two push Boats . Both were single engine however I’m sure there are great many twins maybe more twins than not . I really don’t know I guess you got me on that one . anyways I don’t care I find prop walk to be a nuisance . Flanking rudders on a recreational boat would be interesting . however I learned how to dock in the Columbia river with a five knot current using my one rudder and lots of throttle I was Taught that by a guy that has a slip with An average of five knot current . He taught me to rely on my rudder and my throttle . Much easier on the gearbox to , not to have to do all that shifting in and out of gear forward and reverse , like I say you do it your way . my way works for me

 

[Scooby5959]

Sorry for the crappy spelling I dictate and I didn’t check it before I posted

 

[psneeld]

It's OK to only understand the very basics. Sure maneuvering a twin doesn't require prop wash, but that is one good aspect of counter rotating props and having them turn outboard...it assists in maneuvering.


If you have a single, it probably has some prop walk and whether you use it or not who cares...for newer boaters, it can help if you understand it and use it. Never met a teaching captain that taught otherwise.


Got quite a few hours operating this one, pushing barges with 750,000 pounds of rock on them for bridge repair. Plus some tight places.

 

[Scooby5959]

It's OK to only understand the very basics. Sure maneuvering a twin doesn't require prop wash, but that is one good aspect of counter rotating props and having them turn outboard...it assists in maneuvering.


If you have a single, it probably has some prop walk and whether you use it or not who cares...for newer boaters, it can help if you understand it and use it. Never met a teaching captain that taught otherwise.


Got quite a few hours operating this one, pushing barges with 750,000 pounds of rock on them for bridge repair.

that picture of that push Boat reminded of a push boat i used to see every day it would haul gravel to the concrete plant every morning he passed by It was a single engine to maybe I can find him and ask him if he uses prop walk or does he rely on his rudder and throttle

 

[psneeld]

that picture of that push Boat reminded of a push boat i used to see every day it would haul gravel to the concrete plant every morning he passed by It was a single engine to maybe I can find him and ask him if he uses prop walk or does he rely on his rudder and throttle

If he was single screw and pushing a heavy barge in a lot of current....he was using the wrong technique in my opinion if pushing and trying to turn with rudder. A hip tow and using just forward and reverse is usually a much more maneuverable option than a tiny single tug with just rudder control.


It really helps to understand boat maneuvering when discussing it with people like Fish and others with more experience.


I have a hard time believing a towboat that looks like a box is a single...every one I have seen is a twin. Sure there are small single tugs, but pushboats like in the picture....would enjoy seeing one that is a single...but never want to drive it.

 

[Jeff F]

On a boat with a single engine , and nice big prop, and good prop walk , the boat will have a preferred side to dock. No problem at all.

Agreed. Out of curiosity, which side do you prefer? I now always dock with the reverse prop walk pulling away from the dock, which I guess goes against conventional wisdom.

 

[psneeld]

Agreed. Out of curiosity, which side do you prefer? I now always dock with the reverse prop walk pulling away from the dock, which I guess goes against conventional wisdom.

True it goes against tradition thought, but I also go either side...the walk helps to pull the stern over or I purposely swing the stern in hard and let the reverse and prop walk stop the boat just where I want it and the prop walk stops the swing.

 

[Scooby5959]

True it goes against tradition thought, but I also go either side...the walk helps to pull the stern over or I purposely swing the stern in hard and let the reverse and prop walk stop the boat just where I want it and the prop walk stops the swing.

Now I know for certain you guys are full of baloney Anyways your a push boat captain I’ve never seen a single engine push “boat . the Internet is full of them quiet a few twins to . anyways watch the discovery channel nome gold show they pilot a gold mining barge quite a bit larger than that Single engine that you show in your picture with nothing more than a bucket of a track hoe I could send you pictures of Ocean going to River going to push Boat whatever you guys are a piece of work . Does a barge powered by a track hoe have prop walk oh that’s right just a track hoe

 

[Fish53]

Virtually any boat with a propeller or propellers experiences some prop walk, it's physics for gods sake. It may not be pronounced but unless a propeller is operating in a consistent medium without the proximity of a structure there will be some effect. The exception is a consistent structure such as a Kort nozzle and even there some affect can be realized due to water density at varied depth. What kind of boat is of no relevance to this. Anything that has a predictable affect on a boats maneuverability at least has to be taken into account when maneuvering, whether you choose to make practical use of it or not is up to you. Personally I find great satisfaction in bringing a large, deep draft, single screw vessel to the dock, placing it in reverse and having her lay alongside in perfect form so the deckhands can just drop their lines on a bollard.

 

[FF]

It was no help with prop walk , but back in the day some single engines were set so the shaft angle was offset from the boats center line.

When done right the rudder was amidships during cruise , lowering drag a few percent.

For some reason it is no longer done .

 

[psneeld]

Now I know for certain you guys are full of baloney Anyways your a push boat captain I’ve never seen a single engine push “boat . the Internet is full of them quiet a few twins to . anyways watch the discovery channel nome gold show they pilot a gold mining barge quite a bit larger than that Single engine that you show in your picture with nothing more than a bucket of a track hoe I could send you pictures of Ocean going to River going to push Boat whatever you guys are a piece of work . Does a barge powered by a track hoe have prop walk oh that’s right just a track hoe

Please send some of those pictures of single engine pushboats...I haven't found any after 2 quick searches (there could be some...but few as they would not work well). Single engine is more suited to hip or stern towing...or even Harbor work...seems there is a lot of chatter discussing azipods for pushboats (that may put more in the single category.



Even the smallest seem to have 2 engines for a reason...like the one pictured below.


I showed NO pics of a single engine towboat...the barge with a loader was just an example of the maneuvering necessary that would be pretty crazy with a single. The small twin towboat was the one hooked up in that picture. If I remember, the barge was 120 feet long and we were going into the canal to pick up a small crane that fell off a sunk barge.

 

[Fish53]

Now I know for certain you guys are full of baloney Anyways your a push boat captain I’ve never seen a single engine push “boat . the Internet is full of them quiet a few twins to . anyways watch the discovery channel nome gold show they pilot a gold mining barge quite a bit larger than that Single engine that you show in your picture with nothing more than a bucket of a track hoe I could send you pictures of Ocean going to River going to push Boat whatever you guys are a piece of work . Does a barge powered by a track hoe have prop walk oh that’s right just a track hoe

I have to wonder if your comments are intended to be annoying? Nonetheless You're obviously unfamiliar with the subject at hand. I used to run a 6000hp single screw tug that we primarily towed a 400ft fuel barge with. I can assure you I used prop walk when maneuvering both pushing and on the hip. I've tried to help you understand but as you refuse to try I surrender the effort. Because you can't understand something doesn't mean someone else is wrong. These folks on here are a wealth of knowledge that you can access for free and I invite you to do so, just don't tell them they're wrong or your welcome will be worn quite thin.

 

[Fish53]

It was no help with prop walk , but back in the day some single engines were set so the shaft angle was offset from the boats center line.

When done right the rudder was amidships during cruise , lowering drag a few percent.

For some reason it is no longer done .

It still is on custom boats, some have the driveline slightly angled for the reason you cited, some twins have the engines and drivelines at opposing angles in order to fit larger engines into the deeper part of the bilge. I don't know or believe many production boats would have this feature.

 

[Fish53]

True it goes against tradition thought, but I also go either side...the walk helps to pull the stern over or I purposely swing the stern in hard and let the reverse and prop walk stop the boat just where I want it and the prop walk stops the swing.

I always tie up on the starboard side, which is why I have a lefthanded wheel. Almost every fishing boat I ever ran offloaded on the starboard side so I can't help myself.

 

[mvweebles]

I have to wonder if your comments are intended to be annoying? Nonetheless You're obviously unfamiliar with the subject at hand. I used to run a 6000hp single screw tug that we primarily towed a 400ft fuel barge with. I can assure you I used prop walk when maneuvering both pushing and on the hip. I've tried to help you understand but as you refuse to try I surrender the effort. Because you can't understand something doesn't mean someone else is wrong. These folks on here are a wealth of knowledge that you can access for free and I invite you to do so, just don't tell them they're wrong or your welcome will be worn quite thin.

There is an explanation for trolling: ignorance, arrogance (e.g. 'smartest guy in the room'), or simply being a contrarian, perhaps fueled by alcohol. Anyone who has hung around boats for even a short period and thinks prop walk is some sort of myth ticks at least one of these boxes.

In short: don't feed the trolls.

Peter

 

[rslifkin]

I always tie up on the starboard side, which is why I have a lefthanded wheel. Almost every fishing boat I ever ran offloaded on the starboard side so I can't help myself.

It's funny what reasons some of us have for how we dock. With my boat, even though it has twins and docks just the same to either side, I always dock port side to unless I have a good reason to do otherwise. But that's for boat layout reasons (power inlets are on the port side and I have both center and aft rail gates to port, only an aft one on the starboard side).

 

[psneeld]

I always tie up on the starboard side, which is why I have a lefthanded wheel. Almost every fishing boat I ever ran offloaded on the starboard side so I can't help myself.

My trawler goes to starboard too, but unless conditions are poor, or strongly favor a port tie...then I switch and my setup can be done either way using prop walk like a weak stern thruster in either direction. I am sure with your experience (and others) could easily do it too.


My assistance tow boat was single screw but the long keel, giant prop and tiny rudder...plus either good wind or current made that boat really squirrely as to which direction it was going to back. Prop walk was certainly there, but predictability wasn't. So that was a barrel of laughs....

 

[Fish53]

There is an explanation for trolling: ignorance, arrogance (e.g. 'smartest guy in the room'), or simply being a contrarian, perhaps fueled by alcohol. Anyone who has hung around boats for even a short period and thinks prop walk is some sort of myth ticks at least one of these boxes.

In short: don't feed the trolls.

Peter

You're right Peter, thank you

 

[Dougcole]

I mostly split the gears on our boat. The key to subtle docking in a twin though is throttle control. I seldom have both motors operating at the same rpm when docking. And sometimes one engine is in neutral.

 

[oscar]

I mostly split the gears on our boat. The key to subtle docking in a twin though is throttle control. I seldom have both motors operating at the same rpm when docking. And sometimes one engine is in neutral.

Really? How about subtle use of the transmissions? One or the other, twist etc.....I NEVER touch the throttles docking. Bump it in gear and be ready to pull it out. Things happen quickly. Most of the docking horror shows I see start or culminate in frantic revving of engines. Must be a REALLY bad current or wind before I touch the throttles.

I dock SB at the home port. I try to dock Port side away so I can wash that side......

 

[psneeld]

Diesels less so, but many, maybe most gas boats usually need a little throttle to accomplish snappy maneuvering, necessary in wind and current.

 

[Fish53]

There's more than one way to skin a cat, and even more to land a boat. One thing I almost never see on here is a mention of springlines? Perhaps most of these boats are too small for their use or "crew" isn't up to the job? I would think that at least a basic working understanding of springlines may be of use someday. Perhaps landing in high wind or strong current, maybe after the loss of one engine? Seems a simple enough skill, but then I thought that about prop walk also?

 

[koliver]

Really? How about subtle use of the transmissions? One or the other, twist etc.....I NEVER touch the throttles docking. Bump it in gear and be ready to pull it out. Things happen quickly. Most of the docking horror shows I see start or culminate in frantic revving of engines. Must be a REALLY bad current or wind before I touch the throttles.

I dock SB at the home port. I try to dock Port side away so I can wash that side......

I think you meant to say "ALMOST NEVER" somewhere in that post.

Every docking requires a plan, then a modification to that plan, then another modification, all as the wind and current change as your progress towards your docking advances.
Some of those changes will require more rudder, some will require more or less throttle, some will require changes of gear. With twins, there are twice as many possible changes to consider.
With experience, you get to know what works best, so that will be tried first, but when it isn't enough, or is doing to your progress, something that has now to be corrected, a different approach will be required.

 

[psneeld]

Springs are occasionally discussed, many suggest using a midship line, but other ones are discussed, usually when an individual has a tough slip to get into.

 

[rslifkin]

Really? How about subtle use of the transmissions? One or the other, twist etc.....I NEVER touch the throttles docking. Bump it in gear and be ready to pull it out. Things happen quickly. Most of the docking horror shows I see start or culminate in frantic revving of engines. Must be a REALLY bad current or wind before I touch the throttles.

I dock SB at the home port. I try to dock Port side away so I can wash that side......

I've got enough idle thrust that I rarely touch the throttles in calm conditions or a mild breeze, especially on and off a side tie. But as the wind picks up, sometimes more throttle is needed. Especially when making the turn to come in or out of a slip when it's windy.

 

[Scooby5959]

Diesels less so, but many, maybe most gas boats usually need a little throttle to accomplish snappy maneuvering, necessary in wind and current.

I don’t think the propeller really cares weather it gas or diesel however I don’t get much useful information from this website . I don’t seem to agree with most of what is posted hereI won’t be posting any more or reading it’s ridiculous statements all it does is frustrate me I don’t drink if I continued on with this website I will probably have to start you can post a sarcastic reply but it won’t be read by me . There are some here that have common sense . the ones that don’t that drive me crazy

 

[oscar]

I think you meant to say "ALMOST NEVER" somewhere in that post.

Every docking requires a plan, then a modification to that plan, then another modification, all as the wind and current change as your progress towards your docking advances.
Some of those changes will require more rudder, some will require more or less throttle, some will require changes of gear. With twins, there are twice as many possible changes to consider.
With experience, you get to know what works best, so that will be tried first, but when it isn't enough, or is doing to your progress, something that has now to be corrected, a different approach will be required.

I think the disclaimer was in the latter part of the post. That said I REALLY NEVER touch my rudders. Centered below 3 knots. They're about the size of a pizza box and don't do squat until I get some way on.

 

[psneeld]

Even small rudders do more when you touch the throttles and give them a pop.


Same technique as maneuvering a straight inboard single.


Again, gassers usually need more of this and that to react quickly.

 

[rslifkin]

The gas vs diesel thing comes from this: gassers usually rev higher relative to their idle speed. So for an equal total power, idle thrust is typically a lower percentage of that. So you're more likely to need to add throttle.