On Sun, 19 Sep 2004 02:24:40 GMT, "Calif Bill"
wrote:


"Short Wave Sportfishing" wrote in message
.. .
On Sat, 18 Sep 2004 20:14:34 -0400, "NOYB" wrote:


"Gene Kearns" wrote in message
.. .
On 18 Sep 2004 21:15:33 GMT, (JAXAshby) wrote:

What happens during the interaction of forces on the rode would be
most fascinating.

a way to simplified look at it is to consider the chain/rode/line to
have
zero
weight pulled between two points (say 100 feet apart), then hang a 1#
weight in
the center point and check how much strain it put on the end points
when
the
weight hangs 20 feet, then 10 feet, then 5 feet, then 1 foot, then 1
inch, then
1/10th inch. Just use trig to figure the forces.

So.... we just used intuitive trig to figure out why (1) we use scope
with an anchor and (2) why we don't tie boats to the dock with chain.
Now *that* is some real science......

And your "simplified look" does not apply.... an anchor rode does not
employ both ends at the same "Y" value.... therefore assumptions of
Y=Y'=0 do not obtain and is, therefore, the root cause of your lack
of understanding in this area. There isn't *anything* *attached* to
the middle.


the forces get out of hand ********VERY******** quickly. Even worse,
is
that
the weight in the middle (or chain) has momentum as the boat rocks, so
the
"natural" position of the weight overshoots and makes for seriously
high
g-loads.


There is no weight "in the middle" (other than the weight of the rode)
.... so you put two anchors on the same rode? Odd.

Also, in jaxassby's example, the points can't always be 100' apart if the
weight is hanging further and further down each time...unless he has an
extremely elastic line and there's a large amount of stretch. I assume
that
jaxassby meant to say "using a 100' rope".

The main definition of catenary is that of a curve formed by a
perfectly flexible, uniformly dense, and inextensible cable suspended
from its endpoints. It would look a lot like hyperbolic cosine if you
graphed it out. Which, now that I think about it, wouldn't look a lot
like an anchor rode as much as a tow line.

I'm more curious about strain towards the middle of the curve. That
would be fairly easy to measure at either end, but if you have two
opposing forces of two different weights, say as in a barge tow, the
center strain would constantly move towards one or the other depending
on the weights.

How would you determine that mathematically?

The end points are not at the same elevation.

True, but then a hyperbolic curve does not necessarily have to have
equal level end points (in this case, height). It only has to have a
90º tangent at some point along the curve.

I think I'm getting one of my headaches again. I retired to get away
from all this stuff. :)

Later,

Tom
-----------
"Angling may be said to be so
like the mathematics that it
can never be fully learnt..."

Izaak Walton "The Compleat Angler", 1653