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  #31  
Old 05-23-2010
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Quote:
Originally Posted by RhythmDoctor View Post
Actually, I had been jokingly thinking of something similar. If I were to try this, I would also need to warn people not to stand directly behind either cleat, since if the line had any flex it could fling like a bungee cord. Another potential problem is if the manufacturer of the line reports 50 lb breaking strength, but actually has built in a "safety factor" to account for deterioration over time, and the actual strength of new line is 200 lb.
The actually breaking strength would be easy to check.
A tree limb and a couple of weights from a weight set.

I was also thinking that on the boat end one of the rubber snubber cords where you wrap your dock line around a long rubber tube would give it more of a yank than a snap.
The snap back would be minimal as their would be no weight at the dock end of the line. They did a test of this on myth busters and it was not as much of an effect as expected.

Also you could put the dock line on the west side of the finger pier to give you a couple more degrees angle.

The real challenge would be to have the cahunas to come blasting out fast enough so that the angles would work out. If the stern gets blown west too much and you have no angle you would have no effect.

I can't belive we are talking seriously about this.
You are only 4 hours away from CT what weekend do you have in mind?

In fact we just invented a whole new genre of sailnet videos.
We travel to each others boats and do stuff we would never have the nerve to do on our own and really push the envelope of sailing.
Call it sailnutter.com

Last edited by davidpm; 05-23-2010 at 05:28 PM.
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  #32  
Old 05-23-2010
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Quote:
Originally Posted by davidpm View Post
The actually breaking strength would be easy to check.
A tree limb and a couple of weights from a weight set...
Actually not quite that simple. The rate of deformation greatly affects the breaking strength, especially for synthetic lines. Fast deformation (like you propose for the boat) would cause breakage at a lower tensile stress. The line would be more brittle, and could be confirmed by microscopic observation of the fibers, where a 45 degree spiral characteristic of brittle fracture would be observed. Slower deformation (like with the tree) would cause breakage at a higher tensile stress. The microscope would show "necking" at the fracture points characteristic of ductile breakage. Temperature could have a big effect too - lower temp means more brittle. I'm a polymer guy, so I know a little about these things.

Quote:
Originally Posted by davidpm - definitely not by RhythmDoctor View Post
...I can't belive we are talking seriously about this.
You may be - I am not!
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Formerly posted as "RhythmDoctor"
1998 Catalina 250WK Take Five (at Anchorage Marina, Essington, on the Delaware River)
1991 15' Trophy (Lake Wallenpaupack)
1985 14' Phantom (Lake Wallenpaupack)

Last edited by TakeFive; 05-23-2010 at 07:30 PM.
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  #33  
Old 05-23-2010
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Lessee... 2 really long bungees.... a winch on dock rear and center of your slip... a quick release trigger...oh.. and a tire on the bow... and oh darn.. 2 more bungees in the reverse direction...
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Last edited by deniseO30; 05-23-2010 at 07:05 PM. Reason: too much time on her hands
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  #34  
Old 05-23-2010
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Quote:
Originally Posted by RhythmDoctor View Post
Actually not quite that simple. The rate of deformation greatly affects the breaking strength, especially for synthetic lines. Fast deformation (like you propose for the boat) would cause breakage at a lower tensile stress.
Of course you are correct. I thought of that after posting.

What you are doing to come into the slip is a modified version of "ferry gliding". You may find it interesting to read up on the technique on the forum and others.
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  #35  
Old 05-23-2010
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I installed my simplified hard link today. Weather was too unstable to take it out for a test run. Here are some pics:

Here are the mounting pins without the link attached:


Here is the link. I cut several inches off from the way it was supplied by Stearns. Note that I have prepared the link for the inevitable drop in the water:


This is the view from behind the transom. (If anyone knows where I can find an exact replacement for the fuel box cowl vent please let me know.) Note at the bottom of the aluminum top-of-rudder assembly I have used some adhesive pads with interlocking fingers to secure the base. Without this the assembly has a bit of a tendency to pivot forward and back under the slight torque when turning the motor. Using the pads and a wing nut makes it easily removable in case I need to use the emergency tiller:


Starboard motion is somewhat compromised by the parallax problem of having the link mounted diagonally. I could alleviate this somewhat by moving the pintle more toward port (and adjust the link longer) - then the pintle would move toward the stern when turning starboard. I might also mount a short extension pushing the pintle back a little. But a long extension to make the rod directly from left to right is WAY too much lever arm and would limit the motion of the rudder when the motor reached its limit:


This is the port position. Here I need to be careful not to pivot the motor too far...


...due to close clearance between the shift lever (shown here in forward) and the starboard edge of the motor well:


In order to facilitate the use of the link I reduced the turning friction. As a result, when I tilt the motor it wants to flop to one side. Flopping to port makes it rest harmlessly against the helm seat and railing. There is a little bit of play in the motor housing seal which I plan to eliminate by using some self-adhesive weatherstrip material around the bottom edge of the housing:
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Last edited by TakeFive; 05-23-2010 at 09:05 PM.
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  #36  
Old 05-23-2010
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Very impressive! (better then bungies too!) Now.. if the controls were on the helm...
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  #37  
Old 05-23-2010
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Quote:
Originally Posted by deniseO30 View Post
Very impressive! (better then bungies too!) Now.. if the controls were on the helm...
That is a huge job, and might require a different motor. The pull-pull cable pully system for the tiller/throttle does not look like it would readily convert to a push-pull linkage. I might talk to a dealer, but it's definitely not a DIY job, and I don't want to take the boat out of commission during the season. My wife has done a good job tending the throttle/transmission, so we'll continue with that for now. She bailed me out last time by throttling up at the perfect time to prevent us backing into the dock, so she's getting pretty good at it.
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1991 15' Trophy (Lake Wallenpaupack)
1985 14' Phantom (Lake Wallenpaupack)
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  #38  
Old 05-29-2010
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Quote:
Originally Posted by RhythmDoctor View Post
...Starboard motion is somewhat compromised by the parallax problem of having the link mounted diagonally. I could alleviate this somewhat by moving the pintle more toward port (and adjust the link longer) - then the pintle would move toward the stern when turning starboard. I might also mount a short extension pushing the pintle back a little...
I made this revision tonight. By relocating the pin in a way that the rod comes in tangential to its arc of rotation, it provides much more even rotation to both port and starboard - exactly what I was looking for. Increasing the rotation to starboard was very important because of the orientation of my slip, and it was also needed to negate some of the prop walk effect in the opposite direction. Unfortunately this evening there was still too much thunderstorm threat to take it out for a trial. Hopefully this weekend:





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Formerly posted as "RhythmDoctor"
1998 Catalina 250WK Take Five (at Anchorage Marina, Essington, on the Delaware River)
1991 15' Trophy (Lake Wallenpaupack)
1985 14' Phantom (Lake Wallenpaupack)
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  #39  
Old 05-29-2010
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Pretty slick! see you at 5pm at the deck?

I'm having a dock party at my boat Sunday.
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  #40  
Old 05-29-2010
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Lori and I will be there at 5!
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Formerly posted as "RhythmDoctor"
1998 Catalina 250WK Take Five (at Anchorage Marina, Essington, on the Delaware River)
1991 15' Trophy (Lake Wallenpaupack)
1985 14' Phantom (Lake Wallenpaupack)
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