Tips on docking stern in with twins

admin said:
For example - if you are backing into a slip and your stern is too far to port, all you do is put the sb engine forward and port reverse and the stern will move over to the right towards the slip. If the pivot point was at the bow the bow would move to the left - but is doesn't.
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My bow would move to the left.

Hey Jim, I’ll make you an offer.

Come to Wisconsin and drive my boat.

If you can keep the drives centered and work the throttles / shifters and get the stern to swing as you keep the bow in the same placed you can have my boat.

No lines tied to anything, just floating free in a no current / no wind area.
 
I just took out our 30 Dancer to make sure I am not crazy. Took out my friend with me who is a pretty good boat handler. I spun it around in 2 locations for about 8 rotations at 2500 RPM with zero forward or aft movement. Sitting at the helm you get the impression that the bow is moving. That is because the scenery is flying past the bow rails as the boat spins. Step away from the helm (which I did) and move around the boat to see what is going on and you will realize the bow is not moving much, the stern is doing most of the moving. I figured out 2 ways you can confirm this to yourself. First, the stern makes a small wake off the aft corner the boat rotates with lots of turbulent water coming out from the side the stern is moving away from. The bow is leaving virtually no wake and no turbulent water behind it. (I am not talking about turbulence from the props either. Another cue is the foamy water around the perimeter of the circle. The bow stays just about in the center of the foamy water, the stern is touching up against the foamy water the whole way around each rotation. This means the stern is like the end of a hand of a clock that is nearest the numbers, and the bow is the end closest to the center.

Hope those analogies help you. If you embrace the fact that your stern does the moving it will open you up to all kinds of better looking maneuvers around the dock. A couple of examples of that are:

1 - Pulling away from a T-Head with a boat on the front and back of you along the same T-Head. A typical rookie will do the obvious thing which is to push the boat away from the dock, the pivot so that the bow leaves the space first. As they are pulling away in forward and turning the stern will always get close to the boat ahead of them, and sometimes hit. Add some current or wind and you have a troublesome situation. I see it all the time, the most common docking faux pas. If you are enlightened to the fact that your stern moves, and you are used to handling big boats on your own and making the departure as simple and elegant as possible you will pivot the boat so the bow goes against the dock pilings and the stern moves outward. Once at a 45 degree and you back out of the space. Easy as pie, no chance of damaging your boat or others.

2 - If you have a bow thruster there is a cool trick to make the boat go exactly sideways (if the boat pivoted at the stern this would not be possible). Basically you would again pivot the boat against the dock pilings so the bow is against them and the stern is moving outward. Instead of letting the bow touch the pilings you use the bow thruster to also push the bow away, the boat will move exactly sideways if you are jockey the thruster and throttles correctly.

I understand that there are plenty of people that "think" they can make a boat go exactly sideways without a bow thruster, and there are plenty of people that can use the thruster, then a shifter, then some throttle, then the other shifter, etc to do the same thing. But it is artful to see a good captain do this dance in perfect sync to make it happen perfectly. That is about the only time I think its cool to use a bow thruster :grin: :thumbsup:

I'm not going to go on about this, taken it as far as I can, shoot me an email in a few years when you get it.
 
Hi Jim,

Thank you for taking the time to write the above explanation.

I’m going to try to convince my wife to stand on the dock as I get in a area close to the dock, get the drives straight, put them in opposite gears and do some 360’s as she records it on the video camera.

The idea is to have the camera on the shore so the actual movement should be verifiable.

Again, thank you for the above post.
 
Cool. Get'er done! Prove me wrong and bow thruster companies everywhere will have to shut their doors! Whatever the outcome, make sure you get those RPM's up and have some fun with it :wow: :thumbsup:.
 
When backing into the slip I have seen the stern go to starboard when I put the port in forward and starboard in reverse. I was not under the impression that the boat was pivoting at the bow, but have just learned that the boat behaves this way and use that behavior automatically to line me up in the slip. I thought it was the result of current and/or wind.

Another consideration for my boat is that the engine in forward always has more torque at the same RPM than the one in reverse. If I put one in forward and one in reverse at the same RPM my boat would do a very tight circle. If I increase the reverse engine RPM I would get closer to what would resemble a pivot in place. Not exactly sure where the pivot point is, maybe the bow, maybe the center. I'll have to try it again.
 
admin said:
I just took out our 30 Dancer to make sure I am not crazy. Took out my friend with me who is a pretty good boat handler. I spun it around in 2 locations for about 8 rotations at 2500 RPM with zero forward or aft movement. Sitting at the helm you get the impression that the bow is moving. That is because the scenery is flying past the bow rails as the boat spins. Step away from the helm (which I did) and move around the boat to see what is going on and you will realize the bow is not moving much, the stern is doing most of the moving. I figured out 2 ways you can confirm this to yourself. First, the stern makes a small wake off the aft corner the boat rotates with lots of turbulent water coming out from the side the stern is moving away from. The bow is leaving virtually no wake and no turbulent water behind it. (I am not talking about turbulence from the props either. Another cue is the foamy water around the perimeter of the circle. The bow stays just about in the center of the foamy water, the stern is touching up against the foamy water the whole way around each rotation. This means the stern is like the end of a hand of a clock that is nearest the numbers, and the bow is the end closest to the center.

Hope those analogies help you. If you embrace the fact that your stern does the moving it will open you up to all kinds of better looking maneuvers around the dock. A couple of examples of that are:

1 - Pulling away from a T-Head with a boat on the front and back of you along the same T-Head. A typical rookie will do the obvious thing which is to push the boat away from the dock, the pivot so that the bow leaves the space first. As they are pulling away in forward and turning the stern will always get close to the boat ahead of them, and sometimes hit. Add some current or wind and you have a troublesome situation. I see it all the time, the most common docking faux pas. If you are enlightened to the fact that your stern moves, and you are used to handling big boats on your own and making the departure as simple and elegant as possible you will pivot the boat so the bow goes against the dock pilings and the stern moves outward. Once at a 45 degree and you back out of the space. Easy as pie, no chance of damaging your boat or others.

2 - If you have a bow thruster there is a cool trick to make the boat go exactly sideways (if the boat pivoted at the stern this would not be possible). Basically you would again pivot the boat against the dock pilings so the bow is against them and the stern is moving outward. Instead of letting the bow touch the pilings you use the bow thruster to also push the bow away, the boat will move exactly sideways if you are jockey the thruster and throttles correctly.

I understand that there are plenty of people that "think" they can make a boat go exactly sideways without a bow thruster, and there are plenty of people that can use the thruster, then a shifter, then some throttle, then the other shifter, etc to do the same thing. But it is artful to see a good captain do this dance in perfect sync to make it happen perfectly. That is about the only time I think its cool to use a bow thruster :grin: :thumbsup:

I'm not going to go on about this, taken it as far as I can, shoot me an email in a few years when you get it.
Click to expand...

Well it turns out I was leaving the dock wrong. Thanks!
 
Guys,

I'm on the band wagon here. Jim, I respectfully disagree. With my inboards, I can swing the bow of the boat around agressively, and the stern will move slightly opposite. I'm of the belief that an inboard pivots just forward of the engines, and an I/O pivots behind the engines.

Now, take an I/O and turn the wheel, and I agree with everything Jim says, but that's not what he means to say. I simply disagree.
 
I can only speak for my 300DA with stern drives, but my bow is extremely sensitive to movement in the forward/reverse position. As I enter my slip without current or wind issues, I can get my bow to move without the stern moving while the shifters are in the for/rev position. Logic would tell me that this is only possible because the pivot point on my boat is at the stern. It is difficult to rotate the stern only and I find it requires an opposing force at the bow on a stationary object. This is how I exit a dock with boats fore and aft, but it is the force at the bow that pushes the stern away from the dock. No expert here.....just my experience.
 
Uh oh, hope no bow thruster companies are reading this :grin: We're breaking the news to them that they've been going about it all wrong! If whatever you are doing works for you guys then stick with it. I must say i am extremely impressed with you guys that can move your bow with the props at the other end.
 
Jim, I think you have just explained why I am having trouble docking my 340 in my very windy slip at home. I have been going with the bow in first. I can never swing the bow around when the wind gets a hold of it. I will try going in stern first to see if I have more control. This is how I used to dock at the marina, before I bought the lake home. I never had any problems there, but I thought it was due to it being relatively sheltered from the wind.
 
teekster said:
Jim, I think you have just explained why I am having trouble docking my 340 in my very windy slip at home. I have been going with the bow in first. I can never swing the bow around when the wind gets a hold of it. I will try going in stern first to see if I have more control. This is how I used to dock at the marina, before I bought the lake home. I never had any problems there, but I thought it was due to it being relatively sheltered from the wind.
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More than likely this is exactly why you're having problems. I'm surprised this seems like 'new' news to many. :huh:

Doug
 
jim
i'm with YOU. when i was in the slip pictured below (thankfully for only a 1/2 season), i had a HELLUVA TIME trying get in because it was a bow-in slip (not enough water to do stern in - as a matter of fact i was standing in ankle deep water when i took this photo). despite the slip being about 18' wide, if the bow was not lined up perfectly and wind not compensated for, i'd have all sorts of trouble correcting to get the nose in. the bow moves LITTLE TO NONE in a boat. the concept is the same when you BACK OUT of a parking space in a parking lot. as you start your turn, you have to watch the front of the car so it doesnt clip the rear bumber of the car next to you. backing a car up is like driving forward in a boat.

funny story as an aside: when i bought this boat, the anchor roller was bent a bit to port. one day, trying to get the nose into this miserable slip, i "missed" and upon backing out to try again, i caught the other side of the roller and bend the damn thing back where it belongs. dumb luck - couldnt have done that if i tried 100 times!


lil'krissyiiia.jpg
 
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The reason the thruster is in the bow is the same reason that the bow moves most in differential thrust is the same reason the wind catches and swings the boat around by the bow. The bulk of the boat, weight wise, is in the stern (mid-cockpit). The bulk of the boat, keel wise, is in the stern (mid-cockpit). The bulk of the sail is in the bow. The bow swings freely due to the lack of anchoring in the water (keel) and lack of momentum (light compared to heavy blocks in stern), regardless of the source of the forces causing the motion.
 
This has been a productive and insightful string. Thanks to all for your input. I think I'm more confused than ever. Thankfully, driving the boat comes somewhat naturally, like riding a bike, motorcycle, and driving a standard transmission car. The vehicle becomes an extension of the body. To some that is a natural thing. To others, it can never be done right or safely. I am of the opinion that only a small fraction of the overall population (single digit percentage) can drive a motorcycle or boat skillfully or effectively. Everyone who posted here has demonstrated that they fall into that population. We seem to be over analyzing what we are doing naturally.

Here's something I need to have explained. As I line my boat up to my slip I look to starboard and see the bow anchors of the three boats to starboard of my slip. They are about 10 feet from my gunwale and I am parallel to them. I begin my reverse direction, working the transmissions rev/for, and keeping the outdrives centered to aim the stern toward the mouth of my slip. I keep looking back, never at the bow because I have plenty of swing room. I get the stern lined up with the slip and the boat in perfect alignment and back it in. I'm not arguing or trying to prove a point, but try to help with my confusion. The question is...

If the pivot point is at the bow, why doesn't my stern just swing into the neighboring anchor pulpit? It is only 10 feet away and my LOA is 31'. The weight is at the rear, the drives resist lateral movement like a keel would. The physics and movement don't support that I'm pivoting at the bow.

My pic below is not my slip.
 
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JuliaValentine said:
The question is...

If the pivot point is at the bow, why doesn't my stern just swing into the neighboring anchor pulpit? It is only 10 feet away and my LOA is 31'. The weight is at the rear, the drives resist lateral movement like a keel would. The physics and movement don't support that I'm pivoting at the bow.
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Exactly, because you don't!

Imagine a grandfather clock... if the boat is equivalent to the pendulum, there is no way a boat pivots at the bow. End of story.

If your boat pivoted at the bow, when one stick was in forward and the other was in reverse, your bow would be pinned and your stern would draw a circle around the bow. This just isn't the case.

Doug
 
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One reason why so many Sea Ray owners don't realize the pivot point is near the bow is because the waterline portion of the bow is so far back from the deck portion of the bow. The stem is so raked on a Sea Ray that this might contribute to why you think the boat pivots at the back.

Hampton, of course the bow is what moves around the easiest in regards to wind and whatever else. My point is if it so easy to move the bow back in place using shifters then there would be no need for a bow thruster. Who would ever invest in a bow thruster if you just had to move the shifters to move the bow? That whole industry would not exist, everybody would buy stern thrusters to move the stern.

In all the instruction I have done to new boaters on operating their newly acquired twin screw boat I have never seen people make such a leap in confidence as when they finally realized they have been looking at everything all wrong. Once people learn the stern is what really does the moving they progress much faster and feel much more confident around the docks. Seems a few in this thread have seen the light. The others...well you will...until then just keep doing what works. I also said in one of my first posts on this thread that an I/O boat makes a lousy platform to practice twin screw handling, most of the naysayers have I/O's it seems, so it would be hard to really understand how a twin screw inboard behaves. Anyway..... all is good, a fun debate.
 
admin said:
One reason why so many Sea Ray owners don't realize the pivot point is near the bow is because the waterline portion of the bow is so far back from the deck portion of the bow. The stem is so raked on a Sea Ray that this might contribute to why you think the boat pivots at the back.

Hampton, of course the bow is what moves around the easiest in regards to wind and whatever else. My point is if it so easy to move the bow back in place using shifters then there would be no need for a bow thruster. Who would ever invest in a bow thruster if you just had to move the shifters to move the bow? That whole industry would not exist, everybody would buy stern thrusters to move the stern.

In all the instruction I have done to new boaters on operating their newly acquired twin screw boat I have never seen people make such a leap in confidence as when they finally realized they have been looking at everything all wrong. Once people learn the stern is what really does the moving they progress much faster and feel much more confident around the docks. Seems a few in this thread have seen the light. The others...well you will...until then just keep doing what works. I also said in one of my first posts on this thread that an I/O boat makes a lousy platform to practice twin screw handling, most of the naysayers have I/O's it seems, so it would be hard to really understand how a twin screw inboard behaves. Anyway..... all is good, a fun debate.
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It's funny because I thought we were talking about the same thing until I read this post. I had to go back and reread your post on the previous page and noticed you said the bow barely moved. I totally agree it's the stern that moves, but the piviot or pinned point is not the bow. The pivot point is closer towards the center of the boat (probably 1/3 of the way back from the bow).

Doug
 
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What I was taught was that the pivot point on my boat was right about where the front of my windshield was. Because of where the cockpit seat was, it seemed like the bow was moving much more than the stern, but when you positioned yourself correctly you could see that the stern was moving. In wind, If you let it go, you think that the bow is moving much more than the stern but the boat is pivoting about 3/4's the way up from the back and follows a straight line in the wind from the pivot point as it swings around.

get in some open water and point the bow into the wind, put the engines in neutral and stand on the door of the walk through windshield and watch the boat pivot.
 
Anyone play with the docking simulator in CSR? Love going full throttle into the other boats.
 
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