Steering with twin engines: Differential Throttle Control

[Wayne McCown]

I prefer to approach with the starboard side of the C-Dory alongside the dock, coming in slowly and fairly parallel, using only the port-side engine. When close to the spot where I want to pull against the dock, I turn the prow sharply into the dock, but before touching, shift into and hit the reverse hard for a second or two. The stern of the boat moves sideways into the dock, allowing me to jump onto the dock from the cockpit, grabbing the front and rear lines as I go (both having been placed at the ready, at the same time as the fenders were hung, before approaching the dock).

 

[thataway]

I may be incorrect, but believe that most 40 and 50 hp outboards are right hand rotation, and that there are no counter rotation outboards in this size range. Thus is would be difficult to do the same maneuvers which can be done in counter rotation motors. The larger the prop, the pronounced the prop walk is.

In Wayne Mccowen's case, this would work the same with either port or starboard engine, since they are both right hand rotation, and it is the prop walk to the starboard which brings the boat to the dock--same as with my single engine boats.

Even some of the Tom Cats have same rotation engines. Mine had Suzuki which were counter rotating, but we mounts them the opposite from the standard set up which is--right hand prop on starboard side, and left rotation on the port side.

 

[Switters]

Foggy

No disrespect meant. I'm new to the c-brats forum, but I thought this was a discussion on the topic of maneuvering with twin engines? I understand it may be boring for you to read about different maneuvering techniques, but I'm sure most of the people reading this thread would disagree. Why else would they be reading and commenting on the subject?

I do agree with you that practice trumps acedimia. Of course that's true. Maneuvering a vessel in a constantly changing dynamic environment is tricky. My philosophy is to use the simplest technique whenever possible. The technique that Wayne described is great and would work most of the time. Only in certain conditions would I need to "twin screw" or "walk" the vessel. The fancier you are trying to be, the more trouble you can get yourself in. Relying on more advanced and difficult techniques makes you more susceptible to disasters due due engine or steering failure. One major problem with "walking" a vessel sideways is that it is difficult to check up your motion once you start walking. It can however be a very valuable skill to master and will get you out of trouble if your proficient at it.

I would suggest that anyone interested in learning how to maneuver a vessel with twin engines first learn how to maneuver a single engine vessel. Treat your twin engines just like it is a single. After that technique is mastered, try using one engine at a time, then move on to twisting and walking. Once you have mastered all these techniques through practice, then you will be able to confidently maneuver your vessel in almost any situation. You will truly become Master of your vessel.

What's boring about that?

 

[Foggy]

Yaaawwnnn... Just my reaction to some posts.
No reflection on others.

Everyone is entitled to their own opinion on any subject.
Every opinion does not work for the better of everyone else.
And, there are many.

This is an online forum where anything from "truth" to
nonsense can be expressed either sincerely, in jest or
ignorance.

Can you predictably tell the difference?

Aye.
Grandma used to say, "You are entitled to your own
opinions but not your own facts."

 

[rogerbum]

Yaaawwnnn... Just my reaction to some posts.
No reflection on others.

Everyone is entitled to their own opinion on any subject.
Every opinion does not work for the better of everyone else.
And, there are many.

This is an online forum where anything from "truth" to
nonsense can be expressed either sincerely, in jest or
ignorance.

Can you predictably tell the difference?

Aye.
Grandma used to say, "You are entitled to your own
opinions but not your own facts."

Yawn. I find the discussion of steering more interesting than this post.

 

[BTDT]

Switters,

I too am new to twin engines (Tomcat 255), and I feel fairly confident that I have saved a significant amount of "on-the-job" training mistakes by listening to those who have been-there-done-that. I find it also interesting how various skilled professionals use varying techniques in approaching the dock with twin engines. Using "foggy's" approach to just do it and don't write about it, I doubt I would have learned about using pivot lines in windy conditions, or trying the parallel approach of one C-brat skilled member, versus a 45 degree approach and than turn away of another C-Brat. I have also added quick attach fender mounts outside my sliding windows per Dr Bob, and cam locks near the entry step to secure front docking lines recommended by another C-brat.

I found another great source of docking and mooring info in 'youtube' videos. Some of the videos appear to be off the mark but many are by been-there-done-that professionals. This past weekend I spent several hours experimenting with the varied maneuvering recommendations on C-brats and youtube, and deciding on which ones I liked the best. I'm now waiting for a nice windy day to do some more 'training/playing'.

FWIW - As a Vietnam era helicopter pilot I found that learning-before-doing can often increase your life span. As an old aviation saying goes 'there are old pilots and their are bold pilots, but there are no old-bold pilots'

On a side note- I especially liked Foggy's signature line of "Try being kind rather than being right". :lol:

 

[Sunbeam]

Switters,

Welcome to the forum!

I don't even have twins and I found your post (and the whole discussion) interesting. Never know what I might learn. Thanks for taking the time to write it up :thup

 

[Pandion]

Doubtless, practicing is a crucial part of seamanship. But without some advance understanding of what you're about, you're not really practicing. You're experimenting.

 

[Gene Stebbs.]

On every forum of every type I have been on in the last 20+ years, there is always a number of folks who grow weary of repeat questions and openly express their level of boredom to one degree or another, as always to each their own, it is best not to take any of it personally, and this post is not intended to offend anyone, or directed at anyone, just sharing years of cyber observation and human behaivior in general. My best wishes to all and thanks again for all the help given me so far. I am certain that much of it has been gone over scores of times before....GREAT bunch of folks here.

 

[Switters]

Thanks for the kind greetings.

 

[brooks&judy]

Thanks for that using twin engines post, Harvey, and for the kind words on my little R2AK ditty. I've been backing & filling my 22's port & st'b'd engines to get into and out of the very narrow channel to my "undesirable berth" in Port Townsend. It's the only way I can turn tightly enough to miss the sharp rock rip-rap lining this 12' wide course. The other side of this 300 yard channel is lined with boats side-tied to the floating dock, and the opening between floats to get out is maybe 14' wide. Several knots of wind is often blowing up or down the course.

I find when leaving, doing three knots, it's good to put the st'b'd engine in reverse about a boat-length before the opening I've got to turn right into, running it up to around 2,500 rpm, then goosing up the port engine to perhaps 3,500 rpm ahead to make the boat turn smartly, with a touch more reverse on the st'b'd engine if it looks like I'll run wide. Taking the st'b'd engine out of reverse & into forward straightens the boat's course promptly.

You're sure right about keeping the helm straight ahead, though it's against my instinct. I've got to remind myself not to turn the wheel or I screw it up.

Returning to my 'cheap' berth is the same evolution, just opposite engines put ahead & astern. It might be possible to come & go through this slot & right-angle turn with single-screw, but I'd prefer not to try it. It would mean lots of wheel cranking and goosing it in forward & reverse.

Twin engines do seem the ticket on C-Dorys, which tend to handle like a bar of soap. I second your comments! And thank you for the education on our hydraulic steering systems! Good stuff to know.
~ Bt

 

[thataway]

One of the reasons that topic are often repeated, and tips are also repeated, is that we have a number of new C Dory owners. The boats handle a bit differently than many other boats. We should never discourage questions and learning by new members.

A couple of other thoughts: Always stop and shift the boat before coming into a tight situation. (That is one I learned from experience, when I had the shifter cable securing clip come off of the transmission in a 65,000 #, 62 foot boat!--fortunately no damage, but a lot of sweat!)


A trick I have often repeated is to practice away from a dock. Tie two fenders to a boat hook, and drop it over the side. practice "docking" along side the two fenders--both sides, stern too, and bow too. Also you can set up a slalom course with several fenders if you need to practice short turns. Set up several fenders in shoal water, with weights holding the fenders in place.

Also there are going to be times, when it is better to back into a slip. Especially when you have to go into the wind--the bow will fall off, and the boat can be more accurately steered in reverse.

One other trick not mentioned in docking, is the use of spring lines.

A comprehensive book on docking is by Charles T Low (MD). The book is out of print, but copies are still available on Amazon. Here is a link of an article by Dr. Low,:

http://boatsafe.com/nauticalknowhow/bdock.htm

Although many of the books are written for inboards, there are many common maneuvers which are similar with outboards.

Over 90% of my personal docking experience is with inboard sailboats, where a big rudder is a real advantage.

 

[BTDT]

Dr. Bob,

The previous owner of my 2007 Tomcat had passed away in the boat, and no one in the family had ever driven, so it has been what you might say a true 'learning experience'; to include driving it on to the trailer for my first time at the wheel (after spending an hour looking for circuit breakers to turn-on the Morse dual controls ).

I have spent many days scouring the c-brats and other forums, and can't begin to express my appreciation to all the C-brats who post here.

Now for my question - My Tomcat has 150 Honda's that I assume are counter rotating. In my hands on practice, the one thing I found most challenging was trying to walk the Tomcat sideways. I have used the technique on my friends dual inboards with great results but on the Tomcat no luck. Am I missing something?

I also look forward to meeting you and Marie at Apalachicola.

 

[thataway]

No you are not missing something. The issue with the Tom Cat,, and walking, is that the hulls work as "keels" because of the sharp chine, and make it much harder to walk. Also the outboards work differently than the inboards (see rudder effect). Under some ideal conditions it can be done. A lot depends on the props and the way the engines are set up.

The conventional technique does not work as well with outboards set the opposite from inboards. The larger inboard props have more walking torque. With both engines set to turn inboard -conventional set up--this is what you are normally encountering with a twin screw boat.

One of the differences in an I/O or outboard boat is that you are using prop wash against the rudder in an inboard boat--there is no such effect in an outboard boat. It is the direct stream of the prop wash, not deflected by a rudder. Trimming the motor up and down, can alter this sideways effect also.

Same is true in maneuvering a single inboard boat with a large rudder, you are pushing the stern to one side or another with the thrust of the prop wash against the rudder. (Of course single screw boats turn better to one direction than to the other, because of the prop walk effect.

Even in the C Dory 22, I prefer to dock starboard side too--prop in reverse pulls you over that way more, plus the starboard side is easy to reach the dock and get a line on a cleat or piling form the helm.

 

[Robert H. Wilkinson]

One other trick not mentioned in docking, is the use of spring lines.

I find a spring line is the best initial point of attachment when coming to a dock with the wind blowing you off. I made up a line the exact length to reach from the mid cleat to the stern cleat. The pre spliced end I attach to the mid cleat and on the other end I made a larger loop that I drop over the dock cleat where I want my stern to end up. When the line comes tight from the boats forward momentum I turn the helm off the dock and any prop thrust will keep the boat tight and parallel to the dock overcoming the wind trying to blow you off.

The beauty of having the line this exact length is - if you are coming into a finger dock you know you can keep your forward momentum until the line comes tight without fear of hitting the main dock with the bow. Also it leaves your stern at exactly the right place for you to easily attach the stern line without having to reach or step off.

Regards, Rob

 

[hardee]

Doubtless, practicing is a crucial part of seamanship. But without some advance understanding of what you're about, you're not really practicing. You're experimenting.

Andy, Right On :thup :thup

Believe it or not but some of the Physics principles from HS physics actually stuck.

Switters said:

"I do agree with you that practice trumps acedimia. Of course that's true. Maneuvering a vessel in a constantly changing dynamic environment is tricky. My philosophy is to use the simplest technique whenever possible."

I could not agree more. The idea for the OP came from watching so many operators struggle with side currents, windage, and tight spaces.

Harvey
SleepyC :moon

 

[brooks&judy]

Reading the other posts on this thread brought a couple things to mind re. maneuvering a twin-screw monohull C-Dory.:

Coming to a complete stop, as was suggested, before reversing one engine and going ahead on the other seems like more caution than I think necessary if your equipment is kept in good order. By reversing the engine on the side you plan to turn into while moving slowly anticipates its bite. The boat going 3 knots won't turn immediately, it will begin to turn in a second or two after one engine is reversed. Practice in a safe place is good advice here.

If there's significant wind or current, having weigh on may be the only way to keep control and avoid being blown into something, or as likely a help as having no weigh, depending on your situation, which in a boat is always, ah, fluid.

My reported RPMs, I realized may not be accurate. They were based on guessing by the sound, not observation of the tachs, but I do tend to use a fair number of revs briefly to pivot the boat smartly. Fewer rpm would mean a turn too sluggish to be effective for my described need.

Thanks to whomever for the reminder on springline use for coming alongside an upwind dock.

One last thing: For new C-Dory drivers, beware of letting folks on docks take your lines. Our boats are featherweight compared to most. When I've allowed strangers to our boats to take a line, they've too often pulled far too hard, slamming the boat to the dock so its fenders abruptly bounce it off and leave you out of shape. Best to learn to put it alongside any dock in any condition yourself(s). Even in heavy-displacement boats, I learned it's best not to accept line help from dockwalkers after having the well-intentioned pull or even cleat a line prematurely and ruin my approach.

~ Bt

 

[Hunkydory]

Rob, not to put down any of the other informative post in this thread, but yours for me was worth more than all the rest combined. I have tried many variations of what you described on our CD22 when trying to dock into the wind, but never from the forward cleat of the boat to a dock cleat that would stop the boat, so as the rear cleat of the boat would match that dock cleat. I can see how this would have worked well in so many difficult docking we have made into a strong wind. Rob, thanks for your informative post & Harvey for you starting this thread.

Jay

 

[hardee]

Rob, not to put down any of the other informative post in this thread, but yours for me was worth more than all the rest combined. I have tried many variations of what you described on our CD22 when trying to dock into the wind, but never from the forward cleat of the boat to a dock cleat that would stop the boat, so as the rear cleat of the boat would match that dock cleat. I can see how this would have worked well in so many difficult docking we have made into a strong wind. Rob, thanks for your informative post & Harvey for you starting this thread.

Jay

Jay, the process Rob described is very similar to what I have used, (and was told it was called a "ferry tie"), by tying of the stern cleat to the dock cleat and leaving the outside OB in forward idle, pulling the bow to the dock. His system is using a forward or midship aft spring line, mine only uses the aft mooring line. Both will do the same job, so it becomes a preference thing I think. I don't have the extra line, cut and spliced for the right length so my stern mooring line does the job.


Brooks said:

"Coming to a complete stop, as was suggested, before reversing one engine and going ahead on the other seems like more caution than I think necessary if your equipment is kept in good order. By reversing the engine on the side you plan to turn into while moving slowly anticipates its bite. The boat going 3 knots won't turn immediately, it will begin to turn in a second or two after one engine is reversed. Practice in a safe place is good advice here.

If there's significant wind or current, having weigh on may be the only way to keep control and avoid being blown into something, or as likely a help as having no weigh, depending on your situation, which in a boat is always, ah, fluid.

I agree. I wonder if Bob meant that the engine should be given time to come to zero RPM before switching gear from forward to reverse. I could see that as being less hard on the transmission shifter and linkage.

Harvey
SleepyC :moon

 

[Hunkydory]

Rob, not to put down any of the other informative post in this thread, but yours for me was worth more than all the rest combined. I have tried many variations of what you described on our CD22 when trying to dock into the wind, but never from the forward cleat of the boat to a dock cleat that would stop the boat, so as the rear cleat of the boat would match that dock cleat. I can see how this would have worked well in so many difficult docking we have made into a strong wind. Rob, thanks for your informative post & Harvey for you starting this thread.

Jay

Jay, the process Rob described is very similar to what I have used, (and was told it was called a "ferry tie"), by tying of the stern cleat to the dock cleat and leaving the outside OB in forward idle, pulling the bow to the dock. His system is using a forward or midship aft spring line, mine only uses the aft mooring line. Both will do the same job, so it becomes a preference thing I think. I don't have the extra line, cut and spliced for the right length so my stern mooring line does the job.

Harvey
SleepyC :moon

Harvey, I have tried the way you describe, with & without a loop at the end of the line to slip over the dock cleat. The problem we found is if the line is long enough to easily go over the dock cleat it allows the boat to go forward to far & without a loop, attaching to the cleat can take more time than the wind allows. That combined in the case of where we like to dock at Yellowstone Bridge Bay, with the strong afternoon winds pushing the bow into the electrical box mounted directly in between the two boat slips or another boat in the same two boat slip makes docking on the down wind side impossible for us especially with our large Manson Boss anchor. Rob's method of coming off the forward cleat using a measured line with a loop on the end could make docking where we prefer there possible under the normal afternoon southeast windy conditions. Docking on the other side of these two boat slips is easy with the wind holding the boat where it's wanted, but then if someone else has the other side veritably they will be hitting our boat in the process of their trying to dock.

Jay