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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #41  
Old 01-23-2008
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Rockter will become famous soon enough
Quote:
Originally Posted by sailingdog View Post
Rockter-

You're a Scotsman... no one would ever claim you're sane. And you sail on a lake with a resident monster...

I would never claim to be sane. I am mad. I ride an old Russian motorcycle too. That means I must be mad.
I don't even sail at night on the Loch because I am all feardy.
I am mad and I was doubly mad when I try to reverse into the dock in even a wee blow.
I got all in a flooster.... all that yelling and jumpy heartbeat.

Mad Rockter.
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  #42  
Old 01-23-2008
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You can get a book by Tom Tursi at the Maryland School of Sailing that explains prop walk and docking very well. Then it is practice.
Rick EP
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  #43  
Old 01-23-2008
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One day you will do it perfectly. And no one will be watching.

It is actually very, very easy. Practice, practice practice. I've been doing it for 12 years now. I've succeeded over four times. I'm really proud of myself.

Cap'n Larry and Saltwater Suzi

Last edited by LarryandSusanMacDonald; 01-23-2008 at 10:23 PM.
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  #44  
Old 01-24-2008
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I think many people have these problems because we rarely try to make our sailboats go backwards. If you get used to it then the rest starts to be natural.

My wife was not having any luck reversing the boat to back down on our anchor. We would go any direction but where we needed to go! One day after stomping back to the stern to show her once again how to reverse, I realized this was not the venue to learn this skill. The next day I cast the dink loose in a large bay and we spent probably an hour and a half just circling the dink. We did figure eights around it and started from a stop with the stern at all different wind angles. She got really good and could do it without thinking about it.

I realized by doing this drill, I got better too even though she was doing the driving by thinking about it for the first time in years. Translating prop walk into straight momentum is a simple technique once you master it. Fear is the hardest thing to get over.

I'm really glad I read this post because I have not taught her to spin the boat. We will this spring. Backing practice made my wife confident enough to dock us at our marina. This raised a few eyebrows!
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  #45  
Old 01-24-2008
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See the link below
http://www.boatsafe.com/nauticalknowhow/backfill.htm
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  #46  
Old 01-24-2008
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Slip,
Good link, thanks for posting it.
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  #47  
Old 01-24-2008
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Larry, you really need medal!!!
I have the same problems with full keel and single 3 blades prop (I guess LH or RH works the same way) on 46' boat. Here is how I dock stern-in if I must to(!):
Since some 30,000 pounds is very dependent on inertia I need to neutralize it as soon as I start backing. Once on reverse gear I will try to back without turning steering wheel and holding it dead center (damn hard not to move the wheel – our brains always think of it as another Cadillac). When the boat starts moving and conditions (wind/current) help to go straight I just keep going until I can throw at least one line to deckhand (not allowing him to pull until I say so) and if successful, I am at the bar! If the boat starts to swing out from the intended course I usually switch to forward and kick hard ahead until I fill that the boat stall, then switch back to reverse (no wheel movement). What will happen is, that the bow will loose momentum to bear off and if lucky boat will start moving backwards - usually under different angle to the dock from the one I originally wanted. Once this happen and boat have low speed, I slowly start turning the wheel to the desire course as needed (no more then 5-10 degrees) and I try to steer into the slip. It will take about 30-60 feet for these maneuvers. Not always works and not always successful, but there is no other way that I know to succeed it. In deed it is widely dependent on the current and wind, which must be accounted into the whole process.
Much more easily is to turn on the “dime”. Many times I was able to turn around 40-50’ boat in 60’-70’ wide channel. I stay within about 2/3 of the channel turn the wheel hard to port/starboard and hold it. At the same time for few seconds I will kick forward to about 3/4 RPMs and when the boat is turning fast I will switch to reverse gear with high RPMs (still holding the wheel hard to). This technique has to be repeated several times and no turning the wheel at all, until the boat is facing the other way of the channel or desire course.
If you want to practice it, try it and see if it works for you. It did work for me although I hate to back my boat at all – turning on a “dime” is actually fun and I kind of like to do this.
Ahoy
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  #48  
Old 01-31-2008
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Getting your boat to behave exactly how you want it too is mostly just down to practice, but understanding exactly what prop walk is, can help.
Most people do not know why the boat moves sideways in reverse other than it is something to do with the prop.

The truth is, it is nothing to do with the prop itself. It is caused by the downward angle at which the prop shaft leaves the boat and the hull shape around it.
Yachts with a sail drive experience almost no prop walk as the prop shaft is aligned horizontally.

Lets take a yacht with a prop shaft sloping downwards as it exits the boat.
When the prop spins, a rapid flow of water is forced away from the blades. The flow of water is not contained so the spinning blades results in the flow twisting and rotating out at the edges.
When in forward, this heads off on a slight downward angle towards the rudder and has no effect on the boat.
When in reverse, this flow is sent up towards the hull. The flow of the water on one side of the prop shaft is twisting off away from the hull towards the deep and on the other side is twisting up into the hull. This results in a greater force and flow of water over one side of the hull causing the boat to move sideways.

It is important when controlling a boat under engine to only use bursts of intense throttle and then back to neutral. Do not leave the engine ticking over in drive, forward or reverse. You should be drifting or adjusting.
This means you limit the time the rush of water is pushing the hull sideways in reverse and gives you a kick across the rudder in forward to spin the boat without it moving forward.
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  #49  
Old 01-31-2008
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Quote:
Originally Posted by AndrewScullion View Post
It is important when controlling a boat under engine to only use bursts of intense throttle and then back to neutral. Do not leave the engine ticking over in drive, forward or reverse. You should be drifting or adjusting.
This means you limit the time the rush of water is pushing the hull sideways in reverse and gives you a kick across the rudder in forward to spin the boat without it moving forward.
Thank you Andrew for that note, it is the missing link in how to back into the slip. Very important!!

captkris
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  #50  
Old 01-31-2008
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My shaft line comes straight out and I still get prop walk. All the single screw ships I have driven also get propwalk, to some degree, regardless of the angle the shaft left the hull.

It is always difficult, especially when there is wind and current. That's why they invented tugs. When I was Captain of a 100 ton classic yacht I always had a dinghy in the water to check the swing from prop walk, wind or whatever because it was often unmanageable and always different. The only thing you know for sure is that it isn't going to go straight

There is no pat solution. Each day is different even at the exact same dock. Each boat is different. Just keep practicing but as some one here says in their signature block. Only go as fast as you want to hit ....

Gaz
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There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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