On Sun, 3 Jul 2005 07:55:53 -0400, "Charles T. Low"
[withoutUN] wrote:

So, I follow your theory, but i) do you have a reference and ii) do you have
any experience or knowledge of lines actually sustaining heat damage under
prolonged load/unload cycles.

Rusty has it right, but it's a little extreme.

Friction generates heat energy which transforms materials into other
states - that much is absolutely true.

Ropes have to be placed under extreme loads for internal heat to rise
enough to cause fiber melting. Under normal load/unloading cycles
you'd be hard pressed to create the heat necessary to cause fiber
degradation and melting.

For example, nylon has a critical temp point (call it transition) of
350ºF. 350ºF is the point at which the individual fibers start to
transform. It's melting point is 460ºF - it's a fairly large distance
from 350º to 460º.

Add to that factor, the strength needed for the job it's intended for.
If you are tying up a 52 foot Hatteras with 1/4' inch nylon, you can
expect those sort of stresses which would cause nylon to melt. If you
use 5/8' to 3/4' the chances of it occurring is minute.

In short, line is more likely to break from stress than melt. Now can
repeated load/unload cycles degrade line to the point where it can
"melt"? Yes, but again, the stress is more likely to break the line
than melt it.

Consider this - when was the last time, if ever, that a manila line
burst into flames from internal heat? Ever hear of one?

Manila has a critical point of 180ºF, but it's "melting" point is
350ºF - melting in this case means flames. :)

It's not a likely occupance.