Twin diesels vs. single on a Mainship

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I don't recall any mention of speed as it relates to steering in reverse, in this thread. Steerage in a power boat is most often influenced by prop wash being directed by the rudder that is located behind the prop. In reverse, the rudder is located in front (facing in the direction of motion) of the prop, so gets no influence whatsoever from the prop wash. In order to get any help from the rudder, while in reverse, speed through the water needs to be high enough to allow the rudder to get a good bite into the water flowing past it, more than enough to counteract the walk that the propeller is also creating as a sideways force.
As I have observed on my own boats and many others, trouble comes often to the meek, those unwilling to use enough throttle to develop enough speed to give the rudder that good bite.
Of course having twins eliminates this factor, or allows one to use it to your advantage.
 
Nomad Willy said:
Mark,
You said propwalk is to stbd. Most people talk about their propwalk in reverse.
Assuming you have a left hand prop ..........

The prop wash that moves the boat to L or R comes off the top of a prop. Water being “slung” off the prop w a left hand prop from the lower part of the prop mostly gets slung downwards and has little effect pushing the boat sideways. But at the top of the swing the proximity of the hull impedes the likelihood of the water getting slung upwards. So the prop blade and the hull bottom work together (w a LH prop) to sling the water to port and thus pushing the boat to stbd.

If you have a left hand prop try this ... while taking up your lines gently push or pull a bit to keep your boat in position then after the last line is untied get aboard and push the stern out about a foot. While it’s slowly moving to port go directly to the helm and put the gear in reverse. Give it 1200 - 1500rpm. As you back the boat will try to walk to stbd but since it’s a bit to port and w a bit of momentum it will back just about straight.

I did this over 100 times in Alaska in a slip like yours.
When you get some way on like 2-2.5 knots you may be able to steer in reverse depending on your rudder.
Also you can set the rudder before backing left or right (try right first) or you can back w/o any rudder. But if the rudder is not hard over (to either side) you should hold the rudder firmly so it won’t slam up against the stops or to the end of your hydraulic cylinders range. Possible damage.

Of course if you have a right hand prop you’ll need to find a port tie slip to practice on. And of course you’ll need to change numerous lefts to right ect. Should be obvious what to change and which way.

Once you have some tools in your box like the above you’ll be able to make numerous maneuvers gracefully. At least good enough so you can throw out a good save when needed.
Click to expand...

I would respectfully like to make an addition Eric. Prop walk is the result of propeller blades having both slightly denser water and cleaner flow at the lower portion of their rotation. As I stated earlier prop and rudder size have major influence on this. Boats such as yours and mine with relatively large props and rudders and minimal underbody experience this to a greater degree than say a fairly standard semidisplacement Chinese trawler.
 
Amazing thread drift......


Getting back to the OP original question, the Mainship is a coastal cruiser and is unlikely to be venturing far out of sight of land or Sea Tow.... thus a single would be totally appropriate.


With a captain of one skill level, he'll get more maneuverability with the twins. However, with my limited experience of over a 1000 hour in the single, I've rarely found a docking situation the I couldn't get into or out of (maybe not pretty....). The worst is a cross wind or current into a slip where the twin a pivot off a piling which doesn't work with a single.



As for steering in reverse, yes the Mainship can be steered with the rudder somewhat.... slow speed and coasting a bit will favor the direction of the rudder. I do that several times a week to and from my dock.
 
Seevee said:
Amazing thread drift......


Getting back to the OP original question, the Mainship is a coastal cruiser and is unlikely to be venturing far out of sight of land or Sea Tow.... thus a single would be totally appropriate.


With a captain of one skill level, he'll get more maneuverability with the twins. However, with my limited experience of over a 1000 hour in the single, I've rarely found a docking situation the I couldn't get into or out of (maybe not pretty....). The worst is a cross wind or current into a slip where the twin a pivot off a piling which doesn't work with a single.




As for steering in reverse, yes the Mainship can be steered with the rudder somewhat.... slow speed and coasting a bit will favor the direction of the rudder. I do that several times a week to and from my dock.
Click to expand...


Yeah, that's my experience as well.


My current slip would be difficult but not impossible in most singles. I'm at the very dead end of a canal that is about 400 feet long. The canal is too narrow to allow a boat over maybe 20 feet long to turn around, so you have to either back in or back out. Its got a little dog leg right at the entrance caused by a little mangrove islet. When I'm backing in I have about 5 or 6 feet of room on each side of the boat. Along the dock on my side there is a 52 foot Grand Banks, a 60 something princess and a 60 ish Buddy Davis Sportfish. Grand Banks has their international offices on the other side of the canal so there are always large and/or expensive boats on that side as well. Not a place you want to screw up. I'm happy to have a twin in this scenario.


When I've run singles I've used a short spring line from the outside piling to the aft cleat on the same side to pivot into a slip, it works well. I've done the same thing a couple of times with a twin when I had a strong cross current in a river. Hard to do single handed though.
 
I had my concerns of switching from two engines to one. I can do almost everything I previously could, it just takes a little longer. It’s only been 1.5 years on the single, so I definitely have room for improvement. I think it’s a fair statement to say that twins are more maneuverable than a single for us recreational boaters.

This debate will be alive and well, when we are all dead and gone.
 
Single engine this mainship SD model, twins is beter planing hull boats, If you like run fast.

Over all i like single main engines, i dot have never broblem docking or etc. Keep fuel line, engine and saft lines good conditions and you have nice cruising all weather conditions.


I've been practicing my tug manage without the bow / stern truster and it obeys the well and, if necessary, the boat turns in place using the help trusters, but why would I want to a round sircles when i docking boat?

Read this articel single engines trawler men life...

https://www.dailymail.co.uk/news/ar...ves-brave-crew-carry-dangerous-job-world.html

NBs
 
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Dougcole said:
..........


When I've run singles I've used a short spring line from the outside piling to the aft cleat on the same side to pivot into a slip, it works well. I've done the same thing a couple of times with a twin when I had a strong cross current in a river. Hard to do single handed though.
Click to expand...


Doug,
I've tried similar with mixed results. Guess I need more practice.


Assume you're using the upwind, furthest out piling? And you're bow into the wind?


If so, I find it really tricky if the bow gets away with the wind or current and tries to turn the boat around.



Need some help with this one.....
 
On a single with no thruster you basically have no control over the bow. But you have full control over your stern.

So I prefer to control the bow with a warp to an upwind lateral piling. Wrapped around your capstan, you now have full control. Obviously this is best with one deckhand.
 
Seevee said:
Doug,
I've tried similar with mixed results. Guess I need more practice.


Assume you're using the upwind, furthest out piling? And you're bow into the wind?


If so, I find it really tricky if the bow gets away with the wind or current and tries to turn the boat around.



Need some help with this one.....
Click to expand...


I used to use that technique for a slip I had in a river, there was more cross current than wind. For me having the line the correct length is a big deal. So I kept a line rigged on the outside up current piling that was tied to the correct length.


It helps a ton, obviously, if your boat backs to port if you are entering a slip on your port side. Or vica-versa for a boat that backs to stb. Doesn't really matter with twins (but let's not start that again, lol).


I would approach from down current then lay up against the piling midships, and have my crew use the boat hook to grab the line, then drop the eye of the line over the port aft cleat. Reverse against the line with your rudder (s) hard port. You have to give it a little more juice than you would expect. Surges help. The stern will pivot around the piling.


After I'm lined up I have the crew release the line, pulling a bit fwd if needed, then back straight in.


For me, the pivot line was also the right length to use as my midship spring so it was convenient.


If you have a quick enough crew (or two of them) you can also have them grab the bow line at the same time as the pivot line, and get it on the bow cleat when they can. This will keep the bow from swinging too far downstream. But this can be dangerous for the line handler if they can't get it looped before it comes under load, so be careful.


Hope that helps. I learned that trick from a commercial grouper guy I knew in the same marina, he was great at it.
 
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makobuilders said:
On a single with no thruster you basically have no control over the bow. But you have full control over your stern.

So I prefer to control the bow with a warp to an upwind lateral piling. Wrapped around your capstan, you now have full control. Obviously this is best with one deckhand.
Click to expand...

But first you have to get the bow over so you can get the line on the piling, and, the bow has to be pointed into the wind... each situation has its nuances, so hard to generalize.
 
Interesting (although somewhat predictable) discussion - articulating the various pros and cons is helpful. Can I ask the OP, Hammer, for an update?
 
OldDan1943 said:
Read this articel single engines trawler men life...

https://www.dailymail.co.uk/news/ar...ves-brave-crew-carry-dangerous-job-world.html

Someone duct tape me in bed. I wont be having dinner tonight or maybe never again.

Two point to consider, we are assuming a single engine. "state of the art", maybe 2 engines?
Might as well stay out because it wont be any better while returning to home.
Click to expand...

Hi,

Typically, the Nort sea / Baltic sea trawler is almost always one main engine and a few generators to handle fish processing and refrigeration under the deck, surely there are exceptions.


Exaple:

https://www.maritimesales.com/ARG10.htm
 
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North Baltic sea said:
Hi,

Typically, the Nort sea / Baltic sea trawler is almost always one main engine and a few generators to handle fish processing and refrigeration under the deck, surely there are exceptions.


Exaple:

https://www.maritimesales.com/ARG10.htm
Click to expand...

The vast majority of commercial fishing vessels have a single engine, twins are only used where some specific mission requires their use. Very few oil field vessels are singles mostly because time is an object and money isn't. My preference for single engine is based on my desire for economy and simplicity. I've covered enough miles in singles to not be concerned about the need to carry a spare engine. I'm a decent diesel mechanic and I enjoy handling a single more than a double so for me personally the choice is easy.
 
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