Spectra as rode?

[JPhantom]

Hello All!
I’m outfitting our J/44 to depart to the South Pacific this season. I gifted 500’ of 1” (yes, 1”) breaking strength of 72,000. I would like to save weight in the bow by having 200’ of 5/16 3B chain and 200’ of Spectra. The spectra will work in my windlass. Is there a problem I’m not seeing? Obviously the bitter end will be made fast by easier cutting line. Thanks in advance!
JPhantom

[Jim Cate]

Spectra floats. You really don't want anchor rode floating on the surface when the wind goes light. For me, that would be enough to rule out this usage.

Jim

[Alan Mighty]

Originally Posted by Jim Cate

Spectra floats. You really don't want anchor rode floating on the surface when the wind goes light. For me, that would be enough to rule out this usage.

+1.

I'll add that UHMWPE does not absorb any energy. So you would need to add a snubber. And blowed if I know how you'd get a rolling hitch or a prussic to stay in position on the UHMWPE portion of the rode.

However, that advice might be meaningless. If you've 200 ft of chain, how often is the UHMWPE of rode going to be carrying the load? Only in a few deepwater anchorages. And if that's the case, you've saved carrying a lot of mass and volume of, say, the equivalent heavy and voluminous nylon. Plus you've a ready source of UHMWPE rope for projects!

I'll make two further notes: quite a few of the cargo ships I see are changing from massive polypropylene dock lines to High Modulus/UHMWPE lines. When those cargo ships are berthing at a less protected wharf (one exposed to swell, wash from passing vessels, or exposed to wind gusts, they are using "mooring tails" - a 70 ft (22 metres) or so long nylon rope that is an intermediate link between the UHMWPE mooring line and the bollard on the wharf. Idea is the nylon mooring tail acts as a snubber, absorbing the shock loads from swell surge and wave.

See an example of a mooring tail for commercial shipping: https://www.katradis.com/mooring-tai...-mooring-tails

[Paul L]

There are a number of deep anchorages that you find your self in when cruising the S Pacific. We've been in 70 to 80 feet a few times. Got the anchor hard stuck in 70+ft in Fiji .
The floatiness of dyneema might be a good thing. In the Tuamotus we would add pearl floats to our chain to keep it off the bottom and not snagging bommies. I doubt I would sleep well anchoring deep with coral and dyneema. Saving the weight of another 100ft of chain on the bow would be nice.

[JPhantom]

Thanks! I was thinking along the same lines as Alan, with 200’ of chain onboard there would not be too many occasions where I would need it, but it would be there if need be. The only place I have needed 300’+ was Nuie. I have an idea for a snubber, no knots involved!

[Jim Cate]

Using the floating rode in very deep anchorages is likely OK, for there would be little need to have more than the actual depth in deployed spectra, and then there would be none floating about.

The place that would worry me is using a very long rode to achieve lots of scope in shallower anchorages, anticipating a very strong blow. That's the situation where one could have rode floating on the surface, awaiting a propeller!

We had 85 m of chain plus a lot of nylon on our previous boat. In 17 years of Pacific cruising we only used the nylon a couple of times in Fr Poly, anchoring in 25+ m of depth. We only have 80 m on this boat and rarely need that much.

And Niue was a bitch to anchor in when we were there in 1990... no mornings then!

Jim

[Jim Cate]

Using the floating rode in very deep anchorages is likely OK, for there would be little need to have more than the actual depth in deployed spectra, and then there would be none floating about.

The place that would worry me is using a very long rode to achieve lots of scope in shallower anchorages, anticipating a very strong blow. That's the situation where one could have rode floating on the surface, awaiting a propeller!

We had 85 m of chain plus a lot of nylon on our previous boat. In 17 years of Pacific cruising we only used the nylon a couple of times in Fr Poly, anchoring in 25+ m of depth. We only have 80 m on this boat and rarely need that much.

And Niue was a bitch to anchor in when we were there in 1990... no mornings then!

Jim

[noelex 77]

For our kedge rode we use several 20m lengths of Acera that have eye splices on each end. Acera is an UHMWPE, as is Dyneema and with very similar properties, but it is cheaper. The line can also be used for stern tying to rocks/trees. The light floating line is very easy to swim to shore, or to deploy as a kedge.

The eye splices permit the attachment of snubber to add stretch, or as a convenient means of attaching a small amount of weight to sink the rode if this is required.

However, while high stretch is an extremely important property in a primary anchor rode, there are situations such as recovering from a grounding, or in a stern tie situation, where high stretch is less desirable in an anchor rode. Both of these applications are common roles for a kedge anchor. So these new fibres, while primarily selected for for other properties such as low weight, do add the useful option of deploying a kedge anchor with low or high stretch, the latter using a snubber.

The advantage is the rode is very light and easy to handle, which is important for a kedge. Teamed with a Fortress anchor and no chain it is a very lightweight package for the potential holding power. The combination can even be swum out with a small fender supporting the Fortress until it is deployed.

The system is working well, but has not been used a great deal so proper evaluation will take some time.

However, this is for a kedge anchor. For a primary anchor the advantages are reduced and the drawbacks are more significant. One important potential advantage of UHMWPE line in the primary anchor rode is the reported excellent chafe resistance of these lines. This extra chafe resistance is not universally agreed upon and I think some testing would be helpful. My own guess is that UHMWPE rope that has individual strand coating will have significantly better chafe resistance than traditional rope anchor rode materials, whereas the UHMWPE rope that allows individual fibres to easily separate will only be slightly better.

UHMWPE lines have been available for some time, but the recent reduction in price has opened up new applications. I think it will prove valuable as a Kedge anchor rode, particularly on larger cruising vessels, I am not so sure about its use in the primary anchor system, but he drawbacks in this application, such as the low stretch and buoyancy are relatively easy to overcome. The better chafe resistance (if this is true) helps overcome one of the significant drawbacks of traditional drawbacks of rope anchor rode.

[Paul L]

In the OPs application, South Pacific cruising, I doubt the better chafe resistence is relevent. Pulled tight on a coral bommie and I doubt it will survive. Maybe longer than other rope materials, but not enough to feel good about.

[tkeithlu]

These "specialty" fibers were developed in part to overcome the elasticity of nylon. If you are not using the chain rode to take up shock, I would be concerned about the increased shock load on your anchor and your boat in a blow.

[Breaking Waves]

Seems like the OP is really asking two separate questions:

#1 Is 200' of chain plus some rope a satisfactory solution for the south pacific?

and

#2 If so, is UHMWPE satisfactory rope for the purpose.

As to the first - the answer would seem to be "Yes, IF you fully understand the limitations of what you are doing". We know a number of experienced and knowledgable people who have done the Pacific with that sort of solution and understood its limitations and were just fine. We also know a couple of people who tried it, and were less appreciative of the limitations and had their rope cut by coral heads .

For the second question, there are two aspects. (a) is the floating nature of UHMWPE - which I personally think is a big positive if using rope anywhere near coral heads. It at least has some chance to be floating over them rather than sawing on them. Low budget (most French) cruisers have long used a "polypro plus fishing floats" solution, around coral with decent success, and UHMWPE would be better than that. (b) second is the question of elasticity/shock absorption - in theory, you have a system with extremely small elasticity. In practice, if you have 200' of chain out, you will have some decent chain cantiary to absorb day to day shocks. Much of that will go away in strong winds, and you will need to be able to add some sort of snubber/elasticity in that situation.

I would personally wonder if the weight saving of UHMWPE vs nylon was worth the hassle of the need to set up a snubber on the UHMWPE.

[parkstone bay]

Spectra is non-stretch, I believe? In which case, the answer is No, NO, FECKING NO!! Spectra is completely unsatisfactory as an anchor or mooring line. ALL mooring or anchoring lines MUST have stretch available - that's why some 8-plait is called "Anchorplait" or similar. (But you wouldn't use it for a halliard or a spinnaker guy (brace to our cousins!) just because it does stretch).

[GrowleyMonster]

Either chain, or chain/nylon. High mod line is first of all expensive, and that money could be better spent on something else. Weight reduction? What is the weight difference between 200 feet of spectra and 200' of twisted nylon? With 200' of chain, you would usually be anchoring in at least 40 feet of water before you would be concerned with rope vs coral. In deeper water, when the wind dies and the rope rode sags to the bottom, take some in. Simple enough. A net float seized or zip tied to a point about half the water depth from the chain ought to keep you out of trouble, and the chain should keep it from floating to the surface if you do your part and select the size float that does the job. I would go with nylon, if all chain is out of the question. It stretches. It is (relatively) inexpensive. It is dog simple to splice and knot and stopper. When worn and replaced, it can be repurposed into dock lines or rope fenders or other uses. The high mod rope could be used for rode but I personally think nylon would be the better choice. All respect to differing opinions, of course. This is perilously close to an anchor "discussion" LOL.

[noelex 77]

Originally Posted by parkstone bay

ALL mooring or anchoring lines MUST have stretch available - that's why some 8-plait is called "Anchorplait" or similar.

High stretch is an important characteristic of a primary anchor rode. When a gust or wave hits, the stretch in the rode will help average out the force, reducing the peak load on the anchor. Because the rode stretches, the boat moves back a few metres during these peak loads. Most of the time this small movement is of no consequence providing it is the rode stretching not the anchor moving.

However, it is wrong to believe high stretch in the anchor rode is always desirable. There are anchoring situations where the small movement backwards is undesirable. One is when trying to kedge the boat off a grounding. Another example is some situations when Med Moored with a concrete wall or rocks just behind the stern.

If using a low stretch rode such as Spectra, more of the peak load will be transferred to the anchor. With no stretch the low and high anchor loads are not dampened or averaged. Thus the anchor has to have enough holding power to remain stationary with the maximum peak load otherwise the anchor will start to drag. However, if the holding is sufficient the low stretch option can sometimes be an advantage in the less common anchoring situations when movement backwards is detrimental or even damaging.

I don’t want to cause confusion. Most of the time, high stretch is an important property of a good anchor system, but there are exceptions to this general advice. High stretch is usually, rather than always, beneficial. A low stretch rode rode can be easily converted to high stretch with the addition of a snubber, so a low stretch rode such as chain or Spectra covers both situations.

[CarlF]

As long as you intend to use a good nylon snubber that is long enough (20-30ft), there's no problem having the rest of a rope rode non-stretch.

In fact, very long rodes of nylon are dangerous. The line stretches so much (a 300ft rode can stretch 100ft) that it increases the amount the bow tacks at anchor. There are two problems with tacking at anchor:

a) The side of the boat presents much more windage than the bow. The more the boat points away from the wind the worse the loading on the anchor system.

b) When the bow reaches the end of a deep tack and turns back, a very large load is put on the rode. You can easily observe this on your own bow.

The amount of stretch you want is a function of wind speed and wave not water depth or scope. A good snubber will give the same stretch regardless of water depth.

While I'm at it, many people don't have a snubber with enough stretch. It's either too short or made of too thick nylon. I use a 30ft 7/16" piece of nylon as my daily snubber on my 25 ton boat (the anchor rode is 1/2" chain and 3/4" line). if there's a chance of high winds, I rig a 2nd 5/8" snubber tied 6" looser than the other. In moderate conditions the first will stretch easily reducing shock loading. In heavier conditions the first will stretch enough that the 2nd comes into play long before the first breaks.