I just ran comparative tests, and cotton wins.

The reason?

I was using short lengths of string to tie a whistle and compass together. Split rings wouldn't work in this case. The nylon string came undone every f****** time, no matter how tightly I tied the knot. The cotton string stayed tied and is still tied.

what knot were you using? Nylon is slipperier than cotton but there are knots that don't depend upon friction to hold.

A plain old ordinary square knot. The nylon string is more slippery than Osama is.

Sure you got a square and not a granny? Try a sheet bend knot or adding a couple of 1/2 hitches, one for each tag-end. Sure nylon is slippery but it is still stronger, less vulnerable to water or abrasion. Depends on what you are trying to accomplish.

Was the construction of the nylon string laid (i.e., twisted), braided, or kernmantle (braided sheath w/full-length filaments inside--like 550 paracord)? If laid construction, a square won't hold well at all; it's too slippery. Braided or kernmantle seem to hold better, though still can be slippery.

Try tying a figure-8 knot, instead. Even then, if space, usage, & cord permit, a couple of half-hitches on the free ends are a good idea.

I use braided nylon "accessory cord" for small lanyards, & have no problems if I use a figure-8 knot.

Good luck.

David

It was an ordinary twisted type. I have a knot book somewhere...

Ummm...no I'm not sure. I should try it again.

A square knot. I was juggling the cat at the same time, but I think it was a square knot.

Maybe Craig had some of the Elven rope given to the Hobbits by the Lady of the Wood? Sorry, I;'ve been watching the Two Towers DVD.

This sailor recommends using a single or double becket bed.The knot is also known as a sheet bend.
BOATMAN