Tips on docking stern in with twins

I designed our docking simulator, the pivot point is right about where Turtletone describes so only half of you will find it accurate! :smt089
 
admin said:
I designed our docking simulator, the pivot point is right about where Turtletone describes so only half of you will find it accurate! :smt089
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Why did you put Russo Marine in it? I'm a big fan of them. And, can you make the boats explode please.
 
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admin said:
I designed our docking simulator, the pivot point is right about where Turtletone describes so only half of you will find it accurate! :smt089
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the easiest way to test this "theory" is pull away from a fuel dock. I learned the hard way when I ripped an oar from my dinghy when i tried to pull away by going forward and cranking the wheel away from the dock. then I tried the forward reverse move and ripped the same oar off. Now I turn the wheel away from the dock and reverse.
 
TurtleTone said:
the easiest way to test this "theory" is pull away from a fuel dock. I learned the hard way when I ripped an oar from my dinghy when i tried to pull away by going forward and cranking the wheel away from the dock. then I tried the forward reverse move and ripped the same oar off. Now I turn the wheel away from the dock and reverse.
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Doesn't that rub the bow against the dock when your backing away????:smt101 I'm so confused!!! I'm going to have to re-teach myself how to drive my boat now!!!! Thanks guys... Should have never read this thread....:lol:

Good debate though!
 
I will agree that the stern does move, but not nearly as much as the bow. I think we all assume that the bow is going to swing, so when we acknowledge that the stern moves too (opposite direction), we can begin to refine our docking skills.

The thruster is on the bow so you can use the engines to move the boat where you need it to be instead of sacrificing proper movement of the boat to manage the bow. As it is for me where I dock, I can experience strong winds from the port, bow, or stbd. During winter, they're from the stern, which makes docking very easy.

My Dock faces SW, and I have to enter behind the breakwater from the SE. So, I have to travel NW with rocks to my port and boats (which face the rocks) on my stbd. On days where winds are from the West (normal Summer), I cruise in with the wind off my port bow. Then, I use differential power to swing the bow through the wind.

If the wind is strong, I'll turn 180 degrees so the bow is being held down wind where it wants to be anyway. Then, I'll begin to back toward my slip and use differential power to get the bow swinging into the wind with angular momentum. The goal is to time the boat's alignment with the slip with the bow's rotation stopping, then back in before the wind catches the bow and starts its motion back down wind. Sure, I can use differential thrust to hold the bow up wind, but that will send the stern down wind.

If you can picture the wind trying to blow the bow to port, I use stdb aft and port forward to swing the bow to stbd against the wind. This begins to move the stern to port, so I have to time it to align with my slip. As the bow is almost aligned, I'll put both transmissions in reverse to move back into my slip quickly, then put the port tranny in forward which will hold the bow up against the wind, move the stern slightly to port, and stop the aft movement of the boat in position in the slip.

If I had a bow thruster, I would use that to rotate the bow up wind while using the engines to move the boat back into the slip. Additionally, differential thrust would be used to move the stern UP wind which would tend to SLAM the bow down wind, as it moves a lot more during differential thrust, but that would be countered using the bow thruster.

That's exactly what we did with my buddy's 420 the other day when I helped him take it out for fuel, then to the beach (recent shoulder surgery).
 
Note: I do have some trouble docking in high winds, but I have earned the reputation (mostly undeserved) of being the expert Captain around the docks at my marina. My wife and I laugh about it all the time. We keep hearing the same thing from different sources. Last week, a new guy showed up with a new 310. We had to wait for him to get gas, then he went to dock. After we got gas, he and his son came over to catch us at our slip.

There was some cross wind, but not more than 10 or 12 knots. I backed her in and shut her down. They didn't know what to do. We stepped off and began securing lines while meeting and greeting them. Our boat never touched a piling or dock. They made a couple of comments about it and then began to pick my brain about docking. The Captain asked if we had a bow thruster (nope). After they left, my wife and I joked that the reputation was going to be further cemented. I just hope no one is there to watch my crash landings! (Unless they're able to catch us and save the day.)
 
well it depends on what direction you are going. If you are going forward, the pivot point is near the bow. if you are going backwards, the pivot point moves towards the stern.
 
This is just an issue of semantics, because I understand what you're saying, but once the boat is going forward or reverse, there is no pivot point.

The pivot point only exists when a portion of the boat is "spinning", but not moving on either the X or Y axis.

(back to the finger on a peice of paper analogy)
 
Here is a good explanation of a boats pivot point.

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I can't open that at work, Mike, could you please cut 'n paste it here?
 
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TurtleTone said:
......the great majority of tandem mixed-sex couples paddle with the male in the stern and the female in the bow...... Is there a misogynist mentality lurking in paddlesport, or just a power trip? You tell me.
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Its so you can stare at her butt as you row your arms off.

Its like hanging a carrot on the end of a piece of string from a stick in front of a donkey.
 
All drives and props are not equal and probably have noticable effects when backing in to a slip. Take the B3 for example, counter rotating and neutral vs single right hand props that tend to move the stern
 
Thanks, Mike.

This discussion, regarding the resting pivot point, is assuming a fully symmetrical hull such as a kayak or canoe.

The discussion applies to the amount of hull that touches the water. So, with a Sea Ray, much of the bow is out of the water, and then the forward portion of the bow which is in the water is in shallow when compared to the stern. It's a simple matter of resistance when the boat is not moving forward or aft. With an equal force applied to the side, the stern will resist movement due to two main forces - 1) resistance of the hull in the water with a broad, deep keel, and 2) momentum (mass). The majority of the mass is in the stern due to the shape of the boat, build, and of course, the motors, batteries, transmission, genny...

Take the example of a dart. When thrown sideways, the feathers end up aft and the heavy portion forward for the same two reasons. The feather represents a large keel which resists the movement through the air more than the sleek nose. The heavy nose resists the slowing force of the air due to momentum (mass times velocity). The problem with this analogy is that you are starting with the dart moving sideways and then watching it slow down. With the boat, you are starting with it at rest and then applying forces causing it to move. Also, with a boat in water, the feather (keel) and mass are in the same area, but it helps understand why the boat reacts to the forces the way it does.

The feather analogy explains why the bow swings around in the wind - max wind resistance forward of the pivot point with minimum resistance in the water. It also shows why the stern moves the least in the water - max water resistance, and max mass for the force of the wind to overcome.

Now, consider a new force - differential thrust. Different force, same result. So, the pivot point of the boat is aft of the 1/2 way point of the hull in the water, which is somewhere near the engines. In the case of the stern drives, it is further aft because the weight is further aft and the force applied is beyond the hull of the boat - it's like taking a beam out behind the boat and applying a force to it.
 
my head is about to explode. i think i'll have to use the "unsubscribe to this thread" link. :smt101:smt101:smt101
 
Hampton said:
Now, consider a new force - differential thrust. Different force, same result. So, the pivot point of the boat is aft of the 1/2 way point of the hull in the water, which is somewhere near the engines. In the case of the stern drives, it is further aft because the weight is further aft and the force applied is beyond the hull of the boat - it's like taking a beam out behind the boat and applying a force to it.
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The hull's pivot point without power is one thing. But when docking the point at which it pivots is going to very largely affected by the location of the props and their effects (including prop walk). So while the kayak info is interesting it only tangentially applies here.
 
Any force on a boat afloat, whether exerted by paddle stroke, wind or water, acts to turn the boat around its pivot point.
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The very first statement is FALSE. A force on a boat doesn't have to TURN the boat - around its pivot point or otherwise.

I have to admit though, I hate canoes.
 
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