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Old 03-10-2008, 09:39   #1
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crazy idea for those with deep pockets, spectra (dyneema) anchor line

Some of the largest controversy on how much anchor chain versus rode to carry has to deal with several things, one is the obvious superior chafe resistance of steel versus trying to decrease the weight of an all chain rode. Some have suggested getting around this by have a significant length of nylon rode and attaching floats so it can't be cut quickly by coral heads. Ok, now for the crazy expensive idea, why not use something like 50 ft of high test anchor chain to help set the anchor coupled with 3/8 spectra rode. The 3/8 spectra Amsteel has a working load of 15,500 lbs, a couple hundred feet would cost $500 (but we are talking about no holds budget Rope Inc. Catalog Spectra 12 Strand, Purple Plasma Rope), spectra floats so it would stay away from the coral heads without the need for additional floats and spectra is 15 times more abrasion resistant than carbon steel (Ultra high molecular weight polyethylene - Wikipedia, the free encyclopedia). Thinking about it you might want to weigh it down to prevent trapping a passing dingy. Granted, you would need to impliment a rolling hitch nylon snubber for some elasticity just as you would chain, but that's hardly a big deal.

I'm assuming because I've never heard anyone even mention this as a thought that it's crazy, but I don't understand why....
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Old 03-10-2008, 09:56   #2
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Quote:
Originally Posted by schoonerdog View Post
Some of the largest controversy on how much anchor chain versus rode to carry has to deal with several things, one is the obvious superior chafe resistance of steel versus trying to decrease the weight of an all chain rode. Some have suggested getting around this by have a significant length of nylon rode and attaching floats so it can't be cut quickly by coral heads. Ok, now for the crazy expensive idea, why not use something like 50 ft of high test anchor chain to help set the anchor coupled with 3/8 spectra rode. The 3/8 spectra Amsteel has a working load of 15,500 lbs, a couple hundred feet would cost $500 (but we are talking about no holds budget Rope Inc. Catalog Spectra 12 Strand, Purple Plasma Rope), spectra floats so it would stay away from the coral heads without the need for additional floats and spectra is 15 times more abrasion resistant than carbon steel (Ultra high molecular weight polyethylene - Wikipedia, the free encyclopedia). Thinking about it you might want to weigh it down to prevent trapping a passing dingy. Granted, you would need to impliment a rolling hitch nylon snubber for some elasticity just as you would chain, but that's hardly a big deal.

I'm assuming because I've never heard anyone even mention this as a thought that it's crazy, but I don't understand why....
Hallo Doug

Dyneema has got very limited stretch ( 1 % ) , as you know I am all for saving weight but a weighted line following the anchor chain is the better Idea I think , the weight gives a suspension in the chain and weighted line and this is more pleasant since wave action can be absorbed in this suspended chain line combination.
The weighted lines also have stretch up to 10 5 that absorbs shocks.
In a coral or stony anchor ground I would ideally use at least 50 meters of chain (165 ft) followed by 50 meters of weighted line all depending on depth off course the 1 : 3.5 depth to anchor chain ratio as a minimum

Greetings

Gideon

p.s. Dyneema actually floats
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Old 03-10-2008, 10:22   #3
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correct, chain has zero stretch as well, so this could be thought of as a replacement of chain with a light weight chain so to speak, with a nylon snubber adding your needed elasticity just as you would with chain. Also regarding the catenary effect of chain I would think have something like 50 ft or so of chain would help in wave and low wind conditions and in very high winds the chain would be straight with little or no catenary effect so again you would be relying on a a long nylon snubber to cushion the impact, just as you would with an all chain rode. I get the impression with catenary effect that really the first 50 ft of chain give you the most benefit and additional chain beyond that first 50 feet the advantages fall of fairly quickly. For Rocna anchors they seem to work equally well on all chain versus chain rode combinations. The spectra provides far lighter weight than chain, far better chafe resistance than nylon (according to wiki better than carbon steel), shares the same non stretch of chain but almost all blue water sailors are very unconcerned about that aspect of chain as the nylon snubber helps lessen the impact and if you were willing to carry 165 feet of chain in most anchoring situations in a catamaran you would pretty much have all chain down anyway. It still seems to have more advantages than disadvantages.
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Old 03-10-2008, 10:42   #4
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Even regarding cost it's not that unreasonable, it's about $1 more per ft than the 3/4" nylon it would typically be replacing. I'm really not seeing this as crazy. In most anchorages you could simply retrieve the rode by hand till you started pulling up the chain, then use a couple wraps of the rode around the windlass and heave up the chain, then use the chain to heave up the anchor. It's very workable, certainly seems safer than other rode chain combinations due to the chafe resistance of dyneema/spectra, it's not cost prohibitive, it seems pragmatically doable for anchoring, and I haven't run the math for the catenary loss of more chain, but I would imagine it's not that great when you run the numbers. What am I missing?
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Old 03-10-2008, 10:50   #5
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Originally Posted by schoonerdog View Post
correct, chain has zero stretch as well, so this could be thought of as a replacement of chain with a light weight chain so to speak, with a nylon snubber adding your needed elasticity just as you would with chain. Also regarding the catenary effect of chain I would think have something like 50 ft or so of chain would help in wave and low wind conditions and in very high winds the chain would be straight with little or no catenary effect so again you would be relying on a a long nylon snubber to cushion the impact, just as you would with an all chain rode. I get the impression with catenary effect that really the first 50 ft of chain give you the most benefit and after that the advantages fall of fairly quickly. For Rocna anchors they seem to work equally well on all chain versus chain rode combinations. The spectra provides far lighter weight than chain, far better chafe resistance than nylon (according to wiki better than carbon steel), shares the same non stretch of chain but almost all blue water sailors are very unconcerned about that aspect of chain as the nylon snubber helps lessen the impact and if you were willing to carry 165 feet of chain in most anchoring situations in a catamaran you would pretty much have all chain down anyway. It still seems to have more advantages than disadvantages.
In order to have less weight on board we went from 10 mm galvanized to 8 mm stainless duplex chain on board saving 1.4 kilo per meter or 1 lbs per ft.
Having a minimum length of chain will help settle the anchor. it also prevents from chafing . In African Innovation we started out with 50 ft of chain ( 8 MM stainless ) followed by 50 meters ( 165 ft ) of weighted line but when anchoring in front of St Helena it was not enough
we now equip all FastCats with 25 meters or 84 ft of chain ( duplex ) and the same 50 meters of weighted line. we use the 25 kilo Rocna anchor as the standard and a 15 kilo unit as a spare anchor that can also be used in tandem with the 25 kilo version .
I will look into the Dyneema line as following the anchor chain. for a total of 75 meters standard.
The right type of Dyneema would be the Liros D pro XTR made for running back stays but also very suitable for anchor lines
I will call them Monday to see how they feel about it.

Seil- und Flechttechnologie von LIROS - Rosenberger Tauwerk GmbH

Have a good weekend

Gideon
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Old 03-10-2008, 11:11   #6
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Originally Posted by schoonerdog View Post
Some of the largest controversy on how much anchor chain versus rode to carry has to deal with several things, one is the obvious superior chafe resistance of steel versus trying to decrease the weight of an all chain rode. Some have suggested getting around this by have a significant length of nylon rode and attaching floats so it can't be cut quickly by coral heads. Ok, now for the crazy expensive idea, why not use something like 50 ft of high test anchor chain to help set the anchor coupled with 3/8 spectra rode. The 3/8 spectra Amsteel has a working load of 15,500 lbs, a couple hundred feet would cost $500 (but we are talking about no holds budget Rope Inc. Catalog Spectra 12 Strand, Purple Plasma Rope), spectra floats so it would stay away from the coral heads without the need for additional floats and spectra is 15 times more abrasion resistant than carbon steel (Ultra high molecular weight polyethylene - Wikipedia, the free encyclopedia). Thinking about it you might want to weigh it down to prevent trapping a passing dingy. Granted, you would need to impliment a rolling hitch nylon snubber for some elasticity just as you would chain, but that's hardly a big deal.

I'm assuming because I've never heard anyone even mention this as a thought that it's crazy, but I don't understand why....
This has been done on some deep anchoring commercial ships, such as research vessels that want to stay on station in 600 ft of water. One issue is in handling the slippery Amsteel. When using a spool, it can slide into itself under pressure and be difficult(!) to get to loose again. I doubt you could use a standard windlass with it.

Paul L
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Old 03-10-2008, 11:56   #7
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Thanks to both. I'd be very interested to hear what they end up saying Gideon. I think the amsteel is urethane coated, so it would be the urethane coating which would be "slippery". I think in most situations though, you would simply motor forward pulling the line in as you go with your hands and feeding it down the anchor locker. In just about every situation you would just be lifting a few meters of chain before you could get that chain onto the anchor windlass and start lifting the rest of the chain and ultimate the anchor via chain on the windlass. I'm still not thinking crazy...I probably should be....it's a bizarre concept that something that's only 3/8" big could carry more weight than a heft 3/4 inch line and still be far more chafe resistant.

Quote:
Originally Posted by Paul L View Post
This has been done on some deep anchoring commercial ships, such as research vessels that want to stay on station in 600 ft of water. One issue is in handling the slippery Amsteel. When using a spool, it can slide into itself under pressure and be difficult(!) to get to loose again. I doubt you could use a standard windlass with it.

Paul L
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Old 03-10-2008, 15:11   #8
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Ideas

Dyneema and Dux as an anchor line is a great question.

First thing I think of is the situation where you have all chain, and in a big blow you loose the cantetary. At that point you have a serious snubbing problem. All chain will do this. The shock loads at that point can be damaging as you are punching through waves and have no "give" with all chain.
I bring this up because you have the same situation with Dyneema. Except the situation will arrise much sooner as it has no weight. It will not stretch. It will cause the same or similar damage as chain in that situation. I have seen this stuff crack drums on winches from shock loading. It is amazing stuff, but using it can cause a number of interesting new problems to figure out. Any sharp snubbing and you will be damaging your boat or pulling your anchor out. Not so good.
The natural thought is to attach a snubber of nylon. Well.....how to attach it...?...any knot in Dyneema will weaken it %50 or more. Perhaps a hitch. Not sure. On our multi hulls you can use a nylon bridle, but you still have to think how to attach it to the Dyneema. You could easily splice an thimbled eye in the Dyneema, but you are restricted to using just that length then. A cow hitch is used often on our fishing boat
I have played with a shock cord buried inside the Dyneema as a "core". It makes for a very stretchy line with ultimate strength.
I would love to lighten up my boat with synthetics any place I can. 7mm Dynex Dux has a breaking strength of 15,000 lbs. My boat weighs 7k total. Would be great to us 7mm. I can see it being very hard on the hands though to pull. Just some random thoughts.
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Old 03-10-2008, 15:40   #9
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When we were cruising we had a PDQ cat which had it's anchor roller coming off a single bow instead of the middle of the boat as most cats do (including our present one). I found that making a taught line hitch with another line going to the opposite bow would center the anchor rode and prevent the boat from walking around it's anchor. I would always use this 'taught line hitch' with at least 7 turns and found it really did the job. When I want an actually did a bit more research I found what I had done was "reinvented" an icicle hitch. Either way it's arguably the best hitch for this, it works very very well as line hitch I never had a problem with it slipping. Now my current boat has a centered anchor roller and I use two snubbers coming to each bow and secure each side with an icicle hitch onto the chain or rode, depending on scope and depth. As I'm very familiar and used to doing these hitches, to me hitching a nylon snubber to a dyneema/spectra rode sounds perfectly reasonable. On my present boat I think these snubbers are around 30 ft each. Since this is being tied AROUND the rode rather than into the rode, it doesn't weaken your rode at all.

An icicle hitch

By the way, I'm amazed at how simply knowing how to tie a good knot improves cruising. I trust my knots far more than I trust a lot of other hardware.
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Old 03-10-2008, 16:30   #10
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An icicle hitch

By the way, I'm amazed at how simply knowing how to tie a good knot improves cruising. I trust my knots far more than I trust a lot of other hardware.
Great knot!
But the pull on your first link and the following link (the gripping sailors hitch) seem to pull from opposite ends of the "wrap".

??
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Old 03-10-2008, 17:03   #11
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Thanks SchoonerD, I'm gunna give that icicle a try, also some caution on staino chain, great idea but good house keeping must prevail, I've seen serious crevice corrosion where its been flaked for prolonged periods with bottom mud in the chain locker. All the best from Jeff.
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Old 03-10-2008, 17:51   #12
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Great knot!
But the pull on your first link and the following link (the gripping sailors hitch) seem to pull from opposite ends of the "wrap".

??

I just looked again.

Never mind...................
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Old 04-10-2008, 00:06   #13
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We used to use that hitch to tie nets to float ropes and lead ropes. It works well.
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Old 04-10-2008, 23:59   #14
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Interesting thread.

I play with Dyneema/Spectras all day, I'm not too sure it would be a good thing for an anchor rode.

Fibre Pros -
Weight saving = huge
Strength
Storage
Chafe resistance

Fibre cons -
One very slippery SOB (coating helps but not that much. Almost all are coated to some degree)
Price but not really a biggie
Weight, it's light and the wind will blow it around which maybe annoying at times.
Zero elasticity
Handling, a very small rope with the boat loaded on it and you'll be very lucky if you can hang onto it.
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.
Zero failure warning, it just goes bang.
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.
A 5/8" nylon is a lot more robust, abuse capable and forgiving rope than a 1/4" dyneema.
Spooky to look at. Imagine you are standing on your bow at 4am and it's blowing it's tits off. Even knowing it is strong stuff what will your eyes be seeing and subconscious be thinking. Not much feel good factor in there.

And I certianly wouldn't use Dynex Dux or other heat treated UHMWPE ropes, less flex fatigue resistance. Normal Dynex (the grey stuff usually), Amsteels (inc the 'blue') and a few other aren't heat treated and I'd think the better choice. Almost all of these ropes are SK75 these days so are all very similar even if some of the marketing would suggest otherwise.

We have made a few Dyneema anchor rodes but they were all for full race yachts and we also jacketed them in Vectran to stop the cutting and for UV. They were never intended to be used in real vengeance, more just rule pushers.

Someone asked me for some just last week to use in a Jordon Series drogue instead of nylon. I'm still not to sure about that either but I think I like it in the drouge more than I would in a anchor rode.
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Old 06-10-2008, 10:38   #15
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GMAc, thank you for responding! It does sound like you've got some great experience. Maybe you can resolve this then.

The specific rode I'd be thinking of would be something like 3/8" spectra replacing 5/8" Nylon. Regarding cutting resistance, that's actually the main reason I would considering spectra. I've got no personal experience with it, but I see that Spectra is used specifically for "cut resistant" gloves, cut resistant racing suits, cut resistant liners on coats from knife attacks, and where thick enough in think gloves it has the hightest standard cut resistance of 4 (whatever that means). It's used for those who would be picking up dirty needles, handling knife edges on commercial food processing machines, law enforcement replacing kevlar with more cut resistance for a given weight.

So you're saying that it would take less effort to cut 3/8" spectra under strain than it would 5/8" nylon? You may be right, I frankly don't know. Since you do "deal with this stuff all day", could you rig some sort of test with some scraps? Weigh a 3/8" spectra line with a couple hundred lbs to make it taught and a 5/8" nylon with the same and then try to cut each with the same amount of force? Hell, post it on Youtube!

Spectra*Cut Resistant
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