[MHml] Main Halyard

[Creighton Smith]

Paul nudd wrote:
>
> When I got XL2 (1991) it had a 2:1 main halyard of 10 mm kevlar
> (actually 8mm kevlar with a polyester cover). In 1993 or 4 the kevlar
> started breaking (2 or 3 times) so I replaced it with 8mm spectra and it
> was fine. > core could be broken by hand, all the strength being in the 
> cover.

One cautionary note about aramid (kevlar) line.  The fibers in the line do 
not stretch and are very abrasive to one another.  They will break 
internally if they are run over a conventional sheave with an arc contour to 
the sheave.  Kevlar compatible sheaves are flat in contour and large in 
diameter which equalises the ride of the fibers when going over the sheave. 
This failure mode is insidious as there is no indication of its occurance 
and it happens very gradually.
Modern aramid line is usually blended with spectra which is slippery and 
virtually eliminates fiber to fiber abrasion.
Flat contour sheaves are fine for non-kevlar line.
Creighton