We’ve been experimenting with Dyneema line lately. Technically known as ultra-high molecular weight polyethelene (UHMWPE), the stuff is stronger than steel, yet soft and light. It’s been around for a while and is gradually replacing wire rope in industrial applications. Relatively new for recreational use, it is becoming more prevalent for low-stretch halyards, lifelines, and is even growing in popularity for standing rigging (ie. holding up the mast) on performance-oriented boats.
We already have Dyneema-cored halyards and jib sheets, and when we replaced our running backstays a couple years ago, we switched from wire to Dyneema there. Eventually we’re going to change our lifelines over, and probably our lazy jacks, too. In a couple years we’re going to need a full rig replacement, and I hope to be able to make a good decision between staying with wire or going all synthetic.
Another use for Dyneema is replacing steel shackles, and this has been the focus of our recent experimentation. Soft shackles, as they’re called, are easy to make and there are many sites online that show you how. Sarah can do one in about 30 minutes with $3 of materials, and yet they typically sell for $20-30. She has already realized that the profit margin splicing rope beats the heck out of a lemonade stand.
What we want now is to break a few of them to confirm their theoretical strength. But it’s not that easy to do. I think that loop pictured above might take 12,000 pounds.
Ultimately, I want to use Dyneema shackles to attach our anchor bridle to the chain. Currently we tie the bridle legs on with rolling hitches, but that takes time to do and undo, and is failure prone. Chain hooks don’t do it for me either. I like to sleep at night and a Dyneema shackle a couple times stronger than the chain will do nicely, especially when I can throw on a backup for a few bucks and some child labor.