strength of cow-hitch

[avramd]

Hey everyone,

Does anybody have a link to a really good chart of knots and their associated reduction in strength of the rope they are on? I've done a fair bit of googling, an the particular knot I'm questioning isn't showing up on anything I've found. Perhaps it goes by another name though, please advise

The knot is a cow-hitch. Which is a term I only learned here recently, in the thread about headsail sheet knots - so let me make sure I hav it right: My understanding is that a cow-hitch is when you take a bight in a line, put it through something, and then pull both standing parts of the line through the bight, and cinch it up. Although my particular application of this may cause it to have a different name...

Here's why I'm asking: On the F-22, and I guess other modern lightweight trimarans, there are eye splices everywhere, and a seeming obsession with avoiding hardware at all costs. One frequent example of this is the bow sprit whisker stays. Both had a dyneema eye that was then cow-hitched to an eye-strap. I have to ask - is it defeating the purpose of putting an eye in a line if you then cow-hitch it to something? Or is a cow-hitch in this application still stronger than any loop knot, so the eye has a real purpose, and it's not just showing off/aesthetic?

I realize that the load is on both sides of the hitch, so that seems like it would be stronger than when used for a sail clew. But I still wonder if splicing an eye to use as a cow-hitch is gilding a lily.

[Panope]

Avramd

As you implied, the cow hitch is "doubled" vs. the single working part. Even if the cow hitch kills strength by half, you're still good.

Chafe (at the fitting) is also spread over two lines instead of one.

Steve

[BeauV]

Avramd,

You could look up "Luggage Tag Hitch" or "Girth Hitch" as another name for the knot. (It isn't really a knot) Here are additional names: Girth Hitch, Lark's head, Lark's foot, Girth hitch, Ring hitch, Lanyard hitch, Bale Sling hitch, Baggage Tag Loop, Tag Knot, Deadeye hitch, Running eye. See: Wikipedia Here

In This Link the author makes a differentiation between a cow hitch and a girth hitch (when you have an eye it's technically a girth hitch). The girth hitch is substantially stronger as you're using both sides of the hitch equally. They don't provide absolute strength numbers here.

There's more info here and on other climbing sites, but it's mostly about ropes and less about knots. Climbers always make a big deal about using specific knots we don't use sailing.

Finally, with Dyneema the rope is almost always sized to reduce creap and operates nowhere near its safe working load (SWL). I'd be surprised if there was any risk of the girth hitch knot failing. Most of the time on MAYAN we're operating Dyneema at about 10% of SWL to reduce creap.