crazy idea for those with deep pockets, spectra (dyneema) anchor line

[schoonerdog]

DSM Dyneema fiber. Faster ropes sells dyneema rodes specifically for tugs and ships. In this case study they talk about dyneema anchor rodes specifically being used to anchor larger vessels and it's cost effectiveness due to longer service life. http://www.fasterropes.com/casestudy.pdf

Regarding specifically your cons against.

One very slippery SOB (coating helps but not that much. Almost all are coated to some degree), that's true, but I would think the 12 braided material should have some texture to it and ability to hold on. Typcially when retrieving a nylon rode you simply motor up to relieve tension and then hand pull it in. I've even done that in hurricane, single handed, so I'm not too worried about that per se.

Price but not really a biggie, as you said, it's not really that big of a cost difference.

Weight, it's light and the wind will blow it around which maybe annoying at times. It's only a few lbs lighter than nylon, not that big of a deal. It also may be an advantage in coral heads as it would allow the rode to not sit on top of the coral heads (that would be a weird anchorage, because with 60 feet of chain I'd need to be anchored in deep water surrounded by shallow coral heads).
Zero elasticity - true, neither has chain. So the disadvantage versus an all chain rode is negligible. I would cope with it in the same manner, nylon snubbers.
Handling, a very small rope with the boat loaded on it and you'll be very lucky if you can hang onto it. That's more or less redundant with the first.
Cutting, not quite the same as chafe (rubbing). Dyneema will cut easily if hit in the right place with something sharp especially when under load. OK, that's the one deal breaker. The sole reason for choosing it would be dyneemas superior chafe resistance to nylon (which is indesputable) and superior ability to resist cuts, which you say it's not. So if true, it's not a good idea.
Zero failure warning, it just goes bang. Nylon really doesn't advertise itself well either. Granted strands MAY show breaking before the whole thing breaks, if you happen to pull up the nylon rode before the entire things goes, which would be unlikely.
Minimal drag through the water, it does help towards slowing sailing at anchor.
Bloody noisy when loaded. I'd think it would vibrate like hell if nicely loaded especially if any tide is running. nylon anchor line is going to provide zero drag assistance too, but I would be thinking of this as a chain/rode combination. 60 ft of chain with dyneema rode after that. I typically anchor in 6 to 7 feet of water so most of the time I would be using all chain. In deep anchorages I'd still have 60 feet of chain out plus whatever rode the situation called for.

A 5/8" nylon is a lot more robust, abuse capable and forgiving rope than a 1/4" dyneema. It would be thicker, but less strong, nylon losses strength when wet where dyneema does not, dyneema would be more chafe resistant than the chain let alone the nylon rode...on to the cutting test!

[GMac]

Dyneema is tuff stuff and you can rub the hell out of it and be fine generally and it is not the easiest to cut but under load things change. I lot easier to cut. I'm talking quite high loads so more the load you have when you do want to be happy your rode will hold up.

But I do like your idea and as I do like to play....... stand by

[schoonerdog]

I picked up a couple feet of 7/16" of Sampson Ropes Warp Speed Endura braid, breaking strength of 14,000 lbs and a couple feet of 3/4" nylon rode. My cutting test was simply me sitting at a table with a leatherman using the serrated cutting blade while trying to use equal force with each stroke to cut each piece of rope. My expectation was that the Dyneema would be much harder to cut than the nylon rode, in fact I thought I'd have a very hard time cutting it. I was wrong. Counting the strokes it took to cut through each it was just about the same amount of cutting effort. So the Dyneema failed the test of being a suitable replacement for chain after the first 60 feet or so because it had the same susceptability to being cut as 3/4 inch nylon. So I'm going back to the traditional 150 ft of 5/16" high test chain followed by several hundred feet 3/4" nylon. In 99.9% of anchoring situations I'll be using in effect all chain. Frankly in researching a location as well if it requires a very deep anchorage, than I'll probably skip that particular locale. So conventional wisdom applies, give one to the tried and true.

[fastcat435]

Originally Posted by schoonerdog

I picked up a couple feet of 7/16" of Sampson Ropes Warp Speed Endura braid, breaking strength of 14,000 lbs and a couple feet of 3/4" nylon rode. My cutting test was simply me sitting at a table with a leatherman using the serrated cutting blade while trying to use equal force with each stroke to cut each piece of rope. My expectation was that the Dyneema would be much harder to cut than the nylon rode, in fact I thought I'd have a very hard time cutting it. I was wrong. Counting the strokes it took to cut through each it was just about the same amount of cutting effort. So the Dyneema failed the test of being a suitable replacement for chain after the first 60 feet or so because it had the same susceptability to being cut as 3/4 inch nylon. So I'm going back to the traditional 150 ft of 5/16" high test chain followed by several hundred feet 3/4" nylon. In 99.9% of anchoring situations I'll be using in effect all chain. Frankly in researching a location as well if it requires a very deep anchorage, than I'll probably skip that particular locale. So conventional wisdom applies, give one to the tried and true.

Hallo Doug

why not go for 150 ft of 8 mm duplex stainless chain with a working load of 5800 kilo and a weight of 1.4 kilo per meter length , less than half the weight of the 10 mm chain and the same or even better strength than the 10 mm galvanized.followed by 150 ft of Dyneema 16 mm ?

A total weight of 70 kilo for the chain and another 11 for the rope or a total of 81 or 178 lbs

Greetings

Gideon

[schoonerdog]

I'll definitely be doing the 150 ft of 8mm duplex high test chain and then 3/4" 3 strand nylon. The 3/4" nylon has the same breaking strength and as it's no less cut resistant than thinner spectra, I'd rather have the far cheaper and more easily worked with nylon rode that I can very easily splice.

[GMac]

Originally Posted by fastcat435

why not go for 150 ft of 8 mm duplex stainless chain with a working load of 5800 kilo

Because it doesn't exist is one reason I can think of
I think you mean break load of 5800kg.

If you putting it in an anchor winch you may want to check you size matches Schooner. I don't know of any of the auto rope/chains that will run that match successfully.

[Evan]

Doug,

It's not a bad idea at first glance. But the weight of the rope isn't the big deal; it's the weight of the chain that really adds up.

Compare 200' of 3/8" Spectra to 200' of 5/8" nylon (or whatever you are going to use). 200' Spectra = 11 lbs, 5/8" nylon 3 strand = 22 lbs. For a savings of 11 lbs you have a system that you can't handle with a windlass. Save weight somewhere else. Get rid of a couple pairs of Cindy's shoes and a couple of Zach's books when he's not looking!

I've been pondering the right length of chain for cruising in coral heads in Fr. Polynesia. 150' is sounding about right + whatever rope spliced on.

Picture this: it's blowing the dogs off the chains, you're in a suddenly lee shore anchorage with 3 or 4' breakers rolling in. You don't like the anchorage much any more and you need to leave.

Now you're trying to motor up to the anchor to weigh it by hand. As the boat sheers about, and you come up the anchor, it is alternately going slack and loosening enough to haul in a little more. I don't like handling loaded lines too much, and having a anchor rope of only 3/8" means it's hard to handle anyway. Add a slippery rope like Spectra and you're really having fun.

When I anchored in a river with a 5 knot current, it was really exciting to haul up the rope part of the anchor by hand. The anchor was well set and I had to let go the rode several times when it came taught as we over ran it.

[fastcat435]

Originally Posted by GMac

Because it doesn't exist is one reason I can think of
I think you mean break load of 5800kg.

If you putting it in an anchor winch you may want to check you size matches Schooner. I don't know of any of the auto rope/chains that will run that match successfully.

You are right
the breaking load is 5800 kilo and the right match for a windlass is a 16 mm rope for the chain rode combination.
We work with a windlass from Muir and it works fine

Greetings

Gideon