Lifelines, slack or taught
 

A few months ago, Practical Sailor had a letter concerning whether or
not lifelines should be loose or tight. The argument for loose ones
was something about the force on a tight lifeline would tend to
collapse the stanchion more than the force on a slack lifeline. I
cannot reproduce the argument with any vector diagram I can draw.
Does anybody else have any thoughts on this. Furthermore, there has
been discussion of all rope lifelines instead of wire, any thoughts?


That brings up another useless idea...........

On many boats, the shrouds extend fairly far out toward the toerail
allowing little room to pass between them and the lifelines. On night
sails or in heavy weather, why not simply run lines from about waist
height on the shrouds back to thetop of a stanchion near the stern on
either side. This would effectively provide another lifeline at a
greater height than the existing lower one and would not interfere
with anything. Jacklines would run from bow to stern INSIDE the
shrouds (between shrouds and mast).

Lifelines, slack or taught
 

On 1 Mar 2004 19:22:27 -0800, (Parallax) wrote:

A few months ago, Practical Sailor had a letter concerning whether or
not lifelines should be loose or tight. The argument for loose ones
was something about the force on a tight lifeline would tend to
collapse the stanchion more than the force on a slack lifeline. I
cannot reproduce the argument with any vector diagram I can draw.
Does anybody else have any thoughts on this. Furthermore, there has
been discussion of all rope lifelines instead of wire, any thoughts?

The loose = better argument doesn't make much sense to me. If your
lifeline is free running through eyes at the tops of the stanchions, I
can't see it making much of a difference, other than getting a jerk
when the loose lifelines are pulled taut.

If the lifeline is fixed at the top of each stanchion, you would
definitely want it taut, as pulling on a loose line would mean the
stress is only distributed to the two stanchions immediately adjacent.

..... then again, I don't recall ever hearing of linelines that weren't
free-running along eyes on the stanchions.

Maybe I'm missing something.

-m

Lifelines, slack or taught
 

On 1 Mar 2004 19:22:27 -0800, (Parallax) wrote:

A few months ago, Practical Sailor had a letter concerning whether or
not lifelines should be loose or tight. The argument for loose ones
was something about the force on a tight lifeline would tend to
collapse the stanchion more than the force on a slack lifeline. I
cannot reproduce the argument with any vector diagram I can draw.
Does anybody else have any thoughts on this. Furthermore, there has
been discussion of all rope lifelines instead of wire, any thoughts?

The loose = better argument doesn't make much sense to me. If your
lifeline is free running through eyes at the tops of the stanchions, I
can't see it making much of a difference, other than getting a jerk
when the loose lifelines are pulled taut.

If the lifeline is fixed at the top of each stanchion, you would
definitely want it taut, as pulling on a loose line would mean the
stress is only distributed to the two stanchions immediately adjacent.

..... then again, I don't recall ever hearing of linelines that weren't
free-running along eyes on the stanchions.

Maybe I'm missing something.

-m

Lifelines, slack or taught
 

Parallax wrote:
A few months ago, Practical Sailor had a letter concerning whether or
not lifelines should be loose or tight. The argument for loose ones
was something about the force on a tight lifeline would tend to
collapse the stanchion more than the force on a slack lifeline. I
cannot reproduce the argument with any vector diagram I can draw.
Does anybody else have any thoughts on this. Furthermore, there has
been discussion of all rope lifelines instead of wire, any thoughts?

Tie 2 oz fishing weight in the middle of a 24" piece of string and try
to pull it straight between your hands. You can't do it. As the string
gets straighter the force required goes up as the cotangent of the
angle. At 5º the tension in the line is about 14 times the side force.
At 2º it is more than 28 times. In a straight line the tension would
be infinite. It is not a pure relationship however because even with a
very tight wire the angle increases as the line stretches.

I am not saying that the lifelines need to be slack but they also should
not be guitar string tight.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Lifelines, slack or taught
 

Parallax wrote:
A few months ago, Practical Sailor had a letter concerning whether or
not lifelines should be loose or tight. The argument for loose ones
was something about the force on a tight lifeline would tend to
collapse the stanchion more than the force on a slack lifeline. I
cannot reproduce the argument with any vector diagram I can draw.
Does anybody else have any thoughts on this. Furthermore, there has
been discussion of all rope lifelines instead of wire, any thoughts?

Tie 2 oz fishing weight in the middle of a 24" piece of string and try
to pull it straight between your hands. You can't do it. As the string
gets straighter the force required goes up as the cotangent of the
angle. At 5º the tension in the line is about 14 times the side force.
At 2º it is more than 28 times. In a straight line the tension would
be infinite. It is not a pure relationship however because even with a
very tight wire the angle increases as the line stretches.

I am not saying that the lifelines need to be slack but they also should
not be guitar string tight.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com