Walking a Boat

[Tony B]

Can you 'walk' a twin engine recreational boat such as a Mainship 36?

On commercial vessels it is a common practice especially in the oilfields of the Gulf of Mexico - not much space and always have to squeeze between boats.

My definition of 'walking' is making a boat move sideways. Say for instance I need to slide my boat 5 feet to the right. I would turn the wheel all of the way to the right. Then cross my throttles as if to pivot to the left. Lay the hammers down and the boat will slide sideways to the right. On 125 to 150 foot boats the vibration and stress on the hull is quite a bit. The boat feels like it is jumping but it is stressed for this maneuver. It is done everyday many times over and every day of the year. This maneuver is very noisey 'cause the throttles are down all the way and the water is bubbling up from every which where.
I was just wondering if A). this tactic will work on a pleasure boat and B). will it work without overstressing the structural integrity of the boat?
Thanks in advance.

[jeremiason]

Tony,

The short answer is yes... a Mainship 36 or just about any other recreational power boat will walk to a certain degree.

Now with that said, remember it depends on the size of the rudders and if the props are counter rotating. Not to mention as you know, the wind and currents.

I taught power boating on both Mainship 36 & 42 in San Francisco and I could get them to walk to the dock. I also have driven other power power boats from 30 to 160 feet and all could walk to some degree. Again, it depends on the the vessels set up and the conditions.

With smaller recreational vessels, you don't have to power them as hard to prop walk as the large boats you are accustom to. At 36 feet you will feel vibration, but not like a steel 150 motor vessel and it shouldn't cause harm to the drive train or engine as long as you don't get carried away. Just remember you are moving less weight and draught throught the water.

[Dockhead]

A related maneuver on a single-screw vessel with a bow thruster (like mine ) involves thrusting opposite to rudder position with a burst of power. You get prop wash off the rudder moving the stern of the boat sideways, and the bow thruster prevents this impulse from turning into angular motion. The result is the boat moving sideways, off of or onto a dock, usually.

It's the most useful function of a bow thruster in my opinion.

[Tony B]

Thanks for the info.

On a 135 ft aluminum Crew Boat, it will rattle your teeth loose.
The reason for the question is because on the larger boats we normally had 4 to 6 engines and generally only used the outer ones and didn't know how critical the spacing between engines was.
The steel boats that size were usually referred to as Utility Boats or Small Supply Boats. Heavy as they were, they only had 2 small engines and were pigs when it came to steering and control. They are basically steel shoe boxes and a really terrible ride.

[Tony B]

Originally Posted by Dockhead

A related maneuver on a single-screw vessel with a bow thruster (like mine ) involves thrusting opposite to rudder position with a burst of power. You get prop wash off the rudder moving the stern of the boat sideways, and the bow thruster prevents this impulse from turning into angular motion. The result is the boat moving sideways, off of or onto a dock, usually.

It's the most useful function of a bow thruster in my opinion.

Never used a Bow thruster and even if I did, not sure I would have discovered your method of walking.
I found that with a single screw my best option is to plan as I am approaching the slip at a very slow speed and think of it as a one shot deal.

[captain58sailin]

If you propellers are inboard turning, it is easier to walk the vessel, than outboard turning. What can really make it easy is if you have independant rudders so you can cock them in opposite directions.

[Tony B]

Originally Posted by captain58sailin

................. What can really make it easy is if you have independant rudders so you can cock them in opposite directions.

Was a long day at work today and it isn't over yet so maybe I am not understanding this correctly.
How can you have independant rudders with only one steering wheel?

[Sailmonkey]

Originally Posted by Tony B

Was a long day at work today and it isn't over yet so maybe I am not understanding this correctly.
How can you have independant rudders with only one steering wheel?

Think mississippi river pushboat Or even better, DP on a utility boat. Bow thruster, CP props and independent rudders.

[Tony B]

I am still lost on the independant rudder thing. Normally, the rudder is moved side to side by the steering wheel. Wouldn't you need 2 steering wheels or 2 paddle controllers.

[Tony B]

Originally Posted by Sailmonkey

Think mississippi river pushboat Or even better, DP on a utility boat. Bow thruster, CP props and independent rudders.

Now I am really lost.
What does a Mississippi River push boat have to walk a boat?

DP on a utility boat. What is DP?

CP props - what is CP?

How do the independant rudders work?

Forgive me, I haven't been sleeping well. I've been having a toothache now for almost a week. I am offshore, wifey mailed anti-biotics to heliport last week. I havent received them yet. This afternoon, they found my mail sitting in the guard shack. Hopefully, they will fly them out here tomorrow and shoot the incompetant guard that forgot to bring the package to the front office.
Be gentle with this old guy.

Please rush responce so I can get some sleep. The suspence is killing me.

BTW Matt, did you get my reply?

[Tony B]

Originally Posted by jeremiason

.........remember it depends on the size of the rudders and if the props are counter rotating.
....

I assumed that all twin engine boats had Counter Rotating props. Is that a bad assumption?
And since you are familiar with Mainships, do they have CR Props?
I have money down on one with a survey coming up on May 29. Just assumed thay all were Counter Rotating.

Tony B

[IslandHopper]

Originally Posted by Tony B

Now I am really lost.
What does a Mississippi River push boat have to walk a boat?

DP on a utility boat. What is DP?

CP props - what is CP?

How do the independant rudders work?

Forgive me, I haven't been sleeping well. I've been having a toothache now for almost a week. I am offshore, wifey mailed anti-biotics to heliport last week. I havent received them yet. This afternoon, they found my mail sitting in the guard shack. Hopefully, they will fly them out here tomorrow and shoot the incompetant guard that forgot to bring the package to the front office.
Be gentle with this old guy.

Please rush responce so I can get some sleep. The suspence is killing me.

BTW Matt, did you get my reply?

DP = Dynamic Positioning Dynamic positioning - Wikipedia, the free encyclopedia

CP = CPP = Controllable Pitch Propeller Controllable pitch propeller - Wikipedia, the free encyclopedia

Steering Wheel ???? i haven't seen one of those on an AHTS in years...

AHTS = Anchor handling tug supply vessel - Wikipedia, the free encyclopedia

Independent rudders = We have two dials/joysticks that can operate each rudder independently, or throw a switch and the rudders are synchorised on one dial/joystick...

Dial/Joystick = Steering Wheel......

[jeremiason]

Originally Posted by Tony B

I assumed that all twin engine boats had Counter Rotating props. Is that a bad assumption?
And since you are familiar with Mainships, do they have CR Props?
I have money down on one with a survey coming up on May 29. Just assumed thay all were Counter Rotating.

Tony B

Yes the Mainships I drove had counter rotating props...

Some vessels, especially older ones don't

[cal40john]

I don't see that independent rudder control is all that important for normal rudder and propeller recreational boat. You're throwing the propwash onto the rudder from the engine in forward, you're making little or zero forward/backward progress, and the engine in reverse is throwing propwash away from its rudder. Between no propwash and no fore/aft movement that rudder seems to be pretty much irrelevant as far as its positioning.

John

[Sailmonkey]

Originally Posted by cal40john

I don't see that independent rudder control is all that important for normal rudder and propeller recreational boat. You're throwing the propwash onto the rudder from the engine in forward, you're making little or zero forward/backward progress, and the engine in reverse is throwing propwash away from its rudder. Between no propwash and no fore/aft movement that rudder seems to be pretty much irrelevant as far as its positioning.

John

True,

on a recreational vessel independent rudders are about as useful as an orangutan with a drill.