Sampson Warpspeed & cover parting
 

One of my favorite lines was Sampson Warp speed. It runs well, last and splices well. On my J/24, I had a temporary 1/4" Warp speed halyard tied to a shackle. The cover parted at or near the cleat on the mast. The core remain in tact, however it was too small and slippery for the Harken 150 cleat. In your option, why might the cover on the Warpspeed had parted. It looks as if someone had cut around the core with a pair of scissors; a very even separation

Possibilities
 

Hello,
What is the knot? What was the application? Under sufficient load, the HM core can crawl right out of most knots, putting the load on the core. After that, the best stress riser wins.
Or, it is possible that the cover and core weren't balanced at the factory. It happens. In this case, the cover would again take all the load at the cleat.
Or, the cleat itself, and/or how you belayed to it, might be the culprit. Or all of the above.
Fair leads,
Brion Toss

knot
 

Brian,

Thank you for your post.

The line was knoted to a shackle with a bowline. After the cover broke, teh know was still intact with the core and cover still aligned.

The core and cover being balance seems to be a plausible cause. Is there a good technique to ensure a line (core and cover) is balanced? Does running teh line with a bungy help balance the line?

Alan