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Steering with twin engines: Differential Throttle Control
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Kushtaka



Joined: 17 Dec 2013
Posts: 648
City/Region: Cordova
State or Province: AK
C-Dory Year: 1993
C-Dory Model: 22 Cruiser
Photos: Kushtaka
PostPosted: Thu Oct 15, 2015 7:13 pm    Post subject: Reply with quote

beermanPDX wrote:
Kushtaka wrote:
In forward your boat pivots from near the stern, in reverse it pivots closer to the bow


Isn't it the other way around? Unless by "pivots from" you mean the end that swings more.


Yup. Backwards. Sorry. I shouldn't have used the word pivot. In my defense, I do have a fever. The actual axis is usually about 2/3 of the way forward, with the stern swinging in forward, and about 1/4-1/2 of the way forward in reverse, Most larger boats will pivot from the center, or can if you adjust the throttles a bit as you rotate.

Dr. Bob is right on as usual. The coolest thing out there these days are the computerized helms that turn each outdrive independently. I've played with a Volvo Penta IPS system. If there were ever anything to make me start using i/o engines and drives, it's this. Good thing I can't afford it!!!
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Hunkydory



Joined: 28 Mar 2005
Posts: 2652
City/Region: Cokeville, Wyoming
State or Province: WY
C-Dory Year: 2000
C-Dory Model: 22 Cruiser
Vessel Name: Hunkydory
Photos: Hunkydory-Jay-and-Jolee
PostPosted: Fri Oct 16, 2015 3:19 am    Post subject: Reply with quote

Having now operated our CD 22 with twins since spring 2003, I agree that twins do help maneuvering in tight places with moving the controls much like you would do when operating any tracked vehicle on land. For a long time I made it harder on my self wth not knowing the motors should be centered. In the last couple years, I have spent quite a few hours practicing doing this at remote docks & while underway. While it works well for me in very calm wind & current & can be a help at times when not, the steering control using only the prop controls with the close set twins & non counter rotating props on the CD 22 can be overcome by wind & current, that is not very strong or at least with me at the controls it can. I'm hoping to be proved wrong in this by Harvey or someone else by watching them sometime bring their CD 22 into the dock using only the controls with a strong wind blowing directly off it. In this kind of condition I've only been able to do this maneuver by using the helm & making the approach to the dock at a speed higher than I would liked to have hit it, at about a 45 degree angle & just before bow contact go into reverse while using the helm & momentum to bring the stern toward the dock. If done well the boat will ease up smoothly to the dock & square with it & you have a very short time to get from the boat to the dock with both lines in hand to secure before a strong wind or current takes the boat back away. Of course if not done well some new marks will be put on the boat or the distance from the dock to boat gunnel will be to far to get off & secure it & another try must be made or a better place to dock or anchor found. I have watched boats with wider spaced motors & counter rotating props such as the Glacier Bay cats at Elfin Cove, Alaska do amazing to me maneuvers when docking.

Bottom line is, I believe it best for a CD22 owner/operator with twins to be proficient in using both the helm & motor controls for steering.

Jay

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hardee



Joined: 30 Oct 2006
Posts: 12632
City/Region: Sequim
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Sleepy-C
Photos: SleepyC
PostPosted: Fri Oct 16, 2015 3:43 am    Post subject: Reply with quote

Jay, you are right that one should be proficient in both processes. I have practiced the wheel rotation method and can do it, but the other is so much easier for me.

Your mention of wind and current making it difficult or impossible brings up a good question. How much throttle is safe to apply in the differential system, when, with a 22, the OB's are pretty close together. With my 40's, which are not counter rotating, I have limited it to about 15-1700 and that for only a very short burst. Most of the time idle speed or just above, maybe 1000 is usually plenty adequate.

Harvey
SleepyC Moon


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Though in our sleep we are not conscious of our activity or surroundings, we should not, in our wakefulness, be unconscious of our sleep.
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Switters



Joined: 09 Oct 2015
Posts: 12
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1990
C-Dory Model: 22 Cruiser
Vessel Name: Geturah
PostPosted: Fri Oct 16, 2015 5:03 pm    Post subject: Seamanship Reply with quote

Does anyone know the technique called "walking" The vessel? It is a simple technique used mostly with conventional twin screw tugboat. As captain of a tugboat, I use this technique whenever I am in a tight spot. Walking the vessel refers to moving the vessel perpendicular from its fore and aft orientation with little or no forward or aft movement. It is done by using a combination of ahead and astern propulsion with hard rudder. You could use this technique to get into some really tight spots or between two other vessels. All you need is just enough room for your boat. Here is a quick step by step:

Port side landing:

1) approach the dock at a slow speed (about two knots) and about a 30 degree angle.
2) when close to perpendicular to your desired position, turn your wheel hard right and simultaneously go slightly ahead on your port throttle and astern on your starboard throttle. You will have to go a little harder astern to get the vessel to stop its forward motion.
3) once your bow starts swinging to the starboard, shift the position of the throttles. Ahead on the starboard throttle and astern on the port throttle. Keep the wheel hard starboard. You will now start to move perpendicular toward the dock.
4)adjust your fore and aft motion by using the throttles. If you are moving foward slow your starboard (ahead) and increase your port (astern). If your are creeping astern, slow your port (astern) and increase your starboard (ahead). You will have to practice this until you can find the right balance. Wind and sea condition will be a factor as well.
5) when you are a few feet from the dock, put your throttles in neutral and watch your friends faces as you drift slowly and perpendicular to the dock for a perfect landing in an impossibly tight spot.

For a starboard side landing, everything is opposite. Hope you get a chance to try it. It will take some practice, but I'm sure it will work just as well on a small scale as it does on my tug boat. Let me k ow how it goes.
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Foggy



Joined: 01 Aug 2013
Posts: 1518
City/Region: Traverse City; Northern Lake Michigan
State or Province: MI
C-Dory Year: 2014
C-Dory Model: 26 Venture
Vessel Name: Boatless in Boating Paradise
Photos: W B Nod
PostPosted: Fri Oct 16, 2015 6:02 pm    Post subject: Reply with quote

Reading others steering techniques with twin engines makes
quasi boring reading and doesn't replace actual practice in
your vessel.

Not knocking well meaning contributors to this topic (myself
included), but it think it is well established actual in the water
practice trumps academia every time.

So, get out there and do it in every condition you can find.

I have a friend who never sailed until he bought a sailboat and
wanted to sail to Europe. He bought the boat and practiced
by repeatedly going out on the Great Lakes when most others
wouldn't or were coming in to port due to 'bad weather'. He
gained the confidence he needed and ended up doing 2 Great
Circles to Europe and back with his wife and 2 young daughters.

As we know, "We are the sum of our training."

Aye.

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If someone tells you they don't eat cake, unfriend them. You don't need that kind of negativity in your life.
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Wayne McCown



Joined: 11 Jul 2006
Posts: 368
City/Region: Rochester
State or Province: NY
C-Dory Year: 1999
C-Dory Model: 22 Cruiser
Vessel Name: Little Mac
Photos: Little Mac
PostPosted: Fri Oct 16, 2015 6:17 pm    Post subject: Reply with quote

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).
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thataway



Joined: 02 Nov 2003
Posts: 20779
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Fri Oct 16, 2015 10:29 pm    Post subject: Reply with quote

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.

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Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
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Home port: Pensacola FL
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Switters



Joined: 09 Oct 2015
Posts: 12
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1990
C-Dory Model: 22 Cruiser
Vessel Name: Geturah
PostPosted: Fri Oct 16, 2015 10:55 pm    Post subject: Reply with quote

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?
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Foggy



Joined: 01 Aug 2013
Posts: 1518
City/Region: Traverse City; Northern Lake Michigan
State or Province: MI
C-Dory Year: 2014
C-Dory Model: 26 Venture
Vessel Name: Boatless in Boating Paradise
Photos: W B Nod
PostPosted: Sat Oct 17, 2015 9:10 am    Post subject: Reply with quote

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."
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rogerbum



Joined: 21 Nov 2004
Posts: 5922
City/Region: Kenmore
State or Province: WA
C-Dory Year: 2008
C-Dory Model: 255 Tomcat
Vessel Name: Meant to be
Photos: SeaDNA
PostPosted: Sat Oct 17, 2015 10:38 am    Post subject: Reply with quote

Foggy wrote:
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.
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BTDT



Joined: 07 Jan 2011
Posts: 322
City/Region: Grand Lake Oklahoma
State or Province: OK
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: C- Lark Wine Down
Photos: C-Lark
PostPosted: Sat Oct 17, 2015 11:18 am    Post subject: Reply with quote

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". Laughing

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Sunbeam



Joined: 23 Feb 2012
Posts: 3990
City/Region: Out 'n' About
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C-Dory Year: 2002
C-Dory Model: 22 Cruiser
Photos: Sunbeam
PostPosted: Sat Oct 17, 2015 11:47 am    Post subject: Reply with quote

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 Thumbs Up
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Pandion



Joined: 02 Oct 2013
Posts: 274
City/Region: Kenmore
State or Province: WA
C-Dory Year: 2002
C-Dory Model: 22 Cruiser
Vessel Name: Osprey
Photos: Osprey
PostPosted: Sat Oct 17, 2015 12:04 pm    Post subject: Reply with quote

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.
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Gene Stebbs.



Joined: 29 Jul 2015
Posts: 54
City/Region: McMinnville
State or Province: OR
PostPosted: Sat Oct 17, 2015 12:38 pm    Post subject: Reply with quote

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.
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Switters



Joined: 09 Oct 2015
Posts: 12
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1990
C-Dory Model: 22 Cruiser
Vessel Name: Geturah
PostPosted: Sat Oct 17, 2015 3:41 pm    Post subject: Reply with quote

Thanks for the kind greetings.
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