Has anyone ever tried aluminum chain?

[Franziska]

Originally Posted by Lodesman

Well if you use an app, you'd see that with your formula, you can rest assured that all the chain is off the seabed in any wind over 17 kts. At that rate, why bother with chain at all? Get an even bigger anchor and run dyneema at short scope - that should work, right?

Actually, off the seabed does not mean stretched fully straight. Catenary still buffers.

I'd still use at least some chain followed by oversized (to reduce the chafe risk) Dyneema and a reasonably elastic snubber.
Possibly add a riding weight if conditions worsen.

In coral or rock areas, all chain seems the safest option though. You just sleep better with it.

[thinwater]

I'm not understanding the point in Dyneema for yacht rode. Some weight savings over polyester or nylon, but ...

• Very hard to handle. If there is a power windlass, it won't grab the Dyneema. It will be too small and too slippery. Same with capstan (would work if several extra turns are used) or combination gypsy. Very hard to handle manually (slippery and small).
• Single braid Dyneema will be chafed by a combination gypsy. The chafe resistance of single braid Dyneema is widely exaggerated in anything but smooth and-to-end travel (like a low friction ring).
• Single braid Dymeena is less chafe resistant against rock in side-to-side yawing motions than polyester DB, and similar to nylon. Yes, I have tested this with a full scale test rig using a pendulum. Failures of Dyneema lifelines also speak to this. Something hard, like a rock crystal, slices through it like a knife. Because of its low stretch, fibers do not stretch, but rather slice one at a time. Finally, a tight weave with a cover is required for good side-to-side chafe resistance in any material. This is why nylon webbing can be one of the best chafe gear materials. It is the weave, more than the material.
• You give up all stretch. Polyester, for example, still provides some stretch, depending on the weave.
• Attaching a snubber is difficult. Hitches don't like to grab Dyneema and may slip.
• Some of this can be solved with (expensive) Dyneema doublebraid. But you still need a snubber.

If you can't stand nylon for some reason, look at polyester. It is popular for rode in the UK. Steve Dashew has preached its merits for long lengths, where it has advantage over nylon by reducing excessive stretch. Short rodes perform better with nylon, but once you get to over about 200 feet of chain, the stretch becomes less important and the greater fatigue life and chafe resistance of polyester become valuable. The crossover point is not simple to calculate.

But Dyneema just complicates things without enough upside.


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I have experimented with a ~ 20' Dyneema leader with a floating webbing cover on a kedge I was using to stabilize a boat during anchor testing. The lightweight leader made it much easier to take the second anchor out with a kayak or dinghy, since it avoided dealing with chain, and there was no risk of scratching the topsides with chain when repeatedly breaking out deeply set anchors. The webbing easily dealt with the rocks and shells as the Fortress set. It worked very well. But the rest of the rode was polyester. Dyneema had too many handling challenges. With this experience, the leader was a winner, but no way I would use a Dyneema rode for any common purpose.

[Lodesman]

Originally Posted by Franziska

Actually, off the seabed does not mean stretched fully straight. Catenary still buffers.

That wasn't really my point. If the chain is going to be off the seabed anyway, there really is no need for it to be chafe-proof, now is there? And if one is willing to have the rode leave the anchor at any angle, then why not run it at short scope to keep if off the ground and away from chafing hazards? Any takers?

[noelex 77]

Estimating the minimum safe scope requires a lot of difficult and largely subjective judgments. Factors to include into the decision making process:

The expected strength of the wind and to a lesser extent the current
The quality of the substrate
The performance of the anchor
The size of the anchor (in relation to boat size)
The slope of the seabed where the anchor is located
The depth of water
The type of rode
The expected changes in the direction of pull
The consequences of dragging

It obviously important to ensure you always exceed this estimation. Fortunately, in most cases we can use substantially more scope than the minimum safe amount.

It is worth cultivating the ability to estimate the minimum safe scope. Diving on the anchor and observing the performance at various scopes and in different types of seabeds is very useful, but even if this is not practical, you can determine at what scope you can drag the anchor with full reverse thrust (assuming a sailboat). On most sailboats the force on the anchor with full reverse thrust is similar to around 25 knots wind. Therefore this provides one (albeit rough) data point of the required scope (in that substrate and conditions) to be able to hold in this level of wind.

Taking all these factors into account is much better than blindly following a blanket rule or rules. These rules invariably ignore important parameters that have a significant effect on the required scope.

[s/v Jedi]

Originally Posted by Lodesman

Well if you use an app, you'd see that with your formula, you can rest assured that all the chain is off the seabed in any wind over 17 kts. At that rate, why bother with chain at all? Get an even bigger anchor and run dyneema at short scope - that should work, right?

My formula is well proven (20 years, 3 hurricane hits up to 120kts sustained wind), as is the whole viewpoint that weight must go into the anchor and not the rode.

I’m sure that your claim that the whole chain is lifted off the seabed is true when you test for the extreme end of my formula, but nowhere did I ever recommend to do away with chain, those are your (radical) words that you try to put in my mouth. Won’t work.

Here is why your idea is flawed: at some point the chain will lift off the seabed, also with your formula, whatever an app tells you. When this happens, conditions are worse than when it gets lifted earlier on with my formula. As the anchor must hold in that worse condition, it will automatically also hold in the lighter conditions. I don’t know why this is hard to grasp.
When you read the Cruising Encyclopedia from Steve and Linda Dashew, which is what, 30 or 40 years old, you can already read how this works. It isn’t anything new; it’s just unknown to many cruisers who think an app will save them

[Lodesman]

Originally Posted by thinwater

I'm not understanding the point in Dyneema for yacht rode. Some weight savings over polyester or nylon, but ...

Very good points. I'm not actually pushing for peeps to use Dyneema. If they want to go with a mixed or all-rope rode, they should use whatever material and braid suits them.

My question is to the "use a massive anchor and short scope" proponents, is why they don't eliminate the chain altogether? They see no purpose for the chain within the 'anchoring system', so why take on useless weight? Why don't they put that extra weight into the anchor and run the suitable line of their choice directly to the anchor at a short-enough scope to keep it from chafing on the ground?

[Franziska]

All this is very scientific. Its not that complicated in reality is it.

How about some real-life examples?

35ft cat about 4.5 tons.
Anchor is a 20kg Spade and a 14kg Kobra2 as backup.

In practical terms, our 80ft (25m) of 8mm chain worked perfectly for us.
At the aft end, there are two 4m poly snubbers to each bow.

Between northern Europe and the Med we anchored about 320 nights since last year, had occasionally up to 50kn of wind, and tend to anchor in 3-5m depth. If possible, in sand.
Avoid waves as the plague. Always be aware of the weather. If in doubt, move early.
Try to be the boat furthest in if there is an offshore breeze forecast. That way no-one can drag into you.
Try to have no rocks behind you if you can.
I know this is not possible everywhere, like in the Balearics, but there is usually more than one anchorage to choose from.

Never dragged, usually have enough space to throw the 80ft of chain in.

We never needed the 300ft (roughly 100m) three stranded rope.

Stil, I'd get possibly 100ft of chain when it's due to replacement.

[s/v Jedi]

Originally Posted by Lodesman

Very good points. I'm not actually pushing for peeps to use Dyneema. If they want to go with a mixed or all-rope rode, they should use whatever material and braid suits them.

My question is to the "use a massive anchor and short scope" proponents, is why they don't eliminate the chain altogether? They see no purpose for the chain within the 'anchoring system', so why take on useless weight? Why don't they put that extra weight into the anchor and run the suitable line of their choice directly to the anchor at a short-enough scope to keep it from chafing on the ground?

I am a proponent of a big anchor, but I consider my formula with a minimum of 60’ rode and a 5:1 scope not at all being a proponent of short scope.

The fact that I propose shorter scope as depth increases is completely normal, the consensus of all long time cruisers with ample experience.

Sailors who use more than 5:1 scope simply have an anchor that is not fit for service aboard their boat. Often old tech, worn out, knockoff models or simply too light.

[Lodesman]

Originally Posted by s/v Jedi

My formula is well proven (20 years, 3 hurricane hits up to 120kts sustained wind), as is the whole viewpoint that weight must go into the anchor and not the rode.

You didn't put out any extra chain for the hurricanes?

I’m sure that your claim that the whole chain is lifted off the seabed is true when you test for the extreme end of my formula, but nowhere did I ever recommend to do away with chain, those are your (radical) words that you try to put in my mouth. Won’t work.

Extreme end? WTF are you talking about? Use a typical water-depth and calculate it yourself. A number of the more well-known texts on anchoring give the formulae for determining when the anchor is completely aloft.

Here is why your idea is flawed: at some point the chain will lift off the seabed, also with your formula, whatever an app tells you. When this happens, conditions are worse than when it gets lifted earlier on with my formula. As the anchor must hold in that worse condition, it will automatically also hold in the lighter conditions. I don’t know why this is hard to grasp.
When you read the Cruising Encyclopedia from Steve and Linda Dashew, which is what, 30 or 40 years old, you can already read how this works. It isn’t anything new; it’s just unknown to many cruisers who think an app will save them

It's a lot less likely that I'm going to be surprised by unforecast winds over 35 kts. The chance the winds will go into the high teens however...
If I'm expecting to weather a storm, I'll put out even more chain. And yes that doesn't eliminate the possibility that all the chain could be lifted, but it will ensure the pull at the anchor remains close to, if not, at the horizontal; so if it drags, it should dig in deeper and provide more hold.
I don't know why you automatically assume your anchor "must hold in that worse condition"? Particularly if you're going to set the conditions that could have the rode at near 20º off the seabed, under those worse conditions.

[s/v Jedi]

Originally Posted by Lodesman

It's a lot less likely that I'm going to be surprised by unforecast winds over 35 kts. The chance the winds will go into the high teens however...
If I'm expecting to weather a storm, I'll put out even more chain. And yes that doesn't eliminate the possibility that all the chain could be lifted, but it will ensure the pull at the anchor remains close to, if not, at the horizontal; so if it drags, it should dig in deeper and provide more hold.
I don't know why you automatically assume your anchor "must hold in that worse condition"? Particularly if you're going to set the conditions that could have the rode at near 20º off the seabed, under those worse conditions.

When I prepare the boat for hurricane conditions, much depends on the expected windspeed, fetch, storm surge etc. For the last hurricane we anchored in between Crab Cay and Manjack Cay in the Abacos, Bahamas. We expected 70kts sustained wind and less than 4’ storm surge, no fetch as I was directly in the lee. The water was 14’ deep, hard sand bottom with some grass. Considering our 5’ freeboard and the expected storm surge, I set 120’ of 3/8” G7 chain, locked in a Maxwell chain stopper, plus a 3/4” diameter nylon snubber that caused about 10’ of the chain to hang down in a loop.
We had 70kts wind for more than three hours, followed by a period of 40-50kts wind as the eye passed between us and Florida, then again 70+kts wind for a straight 6 hours and 40-50kts for the 12 hours after that.
The anchor didn’t move an inch, everything was fine.

I knew it would be fine because we went through much worse before, so I didn’t even bring a single line ashore, nor deployed any of the storm anchors we have aboard.

Looking back at this: 14’ depth + 5’ freeboard + 4’ storm surge = 23’. 120’ rode / 23 = 5.2 : 1 scope.

Edit: also, your idea about the pull staying horizontal is flawed. The direction of pull is determined by scope as the chain will be bar tight. The argument of it being impossible of being completely straight is theoretical and plays no role in practice.

[Lodesman]

Originally Posted by s/v Jedi

Looking back at this: 14’ depth + 5’ freeboard + 4’ storm surge = 23’. 120’ rode / 23 = 5.2 : 1 scope.

Edit: also, your idea about the pull staying horizontal is flawed. The direction of pull is determined by scope as the chain will be bar tight. The argument of it being impossible of being completely straight is theoretical and plays no role in practice.

Punched your numbers into the app - your chain would have been 'bar taut' with essentially no catenary left, and departing the anchor at 8º above the horizontal.

For 70 kts, it suggests an optimal scope of 106.1 m (given the windage, mass, etc of my boat) - my 90 m (300 ft) of available chain would leave the anchor at 1º above horizontal, with plenty of catenary still left in the chain.

Out of curiosity, how much chain did you have available?

[s/v Jedi]

Originally Posted by Lodesman

Punched your numbers into the app - your chain would have been 'bar taut' with essentially no catenary left, and departing the anchor at 8º above the horizontal.

For 70 kts, it suggests an optimal scope of 106.1 m (given the windage, mass, etc of my boat) - my 90 m (300 ft) of available chain would leave the anchor at 1º above horizontal, with plenty of catenary still left in the chain.

Out of curiosity, how much chain did you have available?

The 8 degree angle is perfectly fine, as demonstrated by thousands every squall that comes through.

My primary rode is 400’ of 3/8” G7 chain.

If you require catenary and a maximum of 1 degree angle above horizontal, your anchor is a joke. Sorry, but that is how it is. Under real world circumstances, you can’t put out 100 meters of chain because there are dozens of boats all around you preventing this. If your anchor can’t hold on 5:1 scope, you need to tie to shore, run for the mangroves.

My anchor is 176lbs. I just go to sleep with 50kts.

[noelex 77]

Originally Posted by Lodesman

Well if you use an app, you'd see that with your formula, you can rest assured that all the chain is off the seabed in any wind over 17 kts. At that rate, why bother with chain at all? Get an even bigger anchor and run dyneema at short scope - that should work, right?

That calculation is not correct. All the chain will not typically be off the bottom in 17 knots of wind in, for example, 20 feet of water with a 5:1 scope using all chain rode.

Just dive and take a look.

[rslifkin]

Even if all of the chain is lifted, you still need chafe resistance. You have to account for debris sticking up, lulls in the wind, direction changes, etc. that could all allow the rode to snag the bottom.

If the primary purpose of chain were for weight, we'd all be using the biggest, heaviest chain we could carry, rather than a long length of light, high strength chain.

[Kettlewell]

Ha! A thread about aluminum chain has morphed into the endless anchoring debate, so of course I must join in. Put me in the camp with Jedi on practical, real-world anchoring advice that just works, though it must be noted I have used "only" a 45-lb main anchor on my 38-footer. IMHO one of the key factors is to make sure the anchor is properly set and holding at 5:1 before considering lengthening scope in a blow or shortening scope if there is a swinging problem. In many places I anchor you can't hang on more than 5:1 without causing problems for your boat or others around you. I have used second anchors (Fortress and Danforth) on all-nylon rode or with short 6-foot chain leaders many times and they hold just fine up to hurricane force. The other day I was anchored near a classic schooner that dropped a big Spade anchor over the side (no roller) on an all nylon rode then proceeded to weather a minor overnight blow that sent several all-chain rode guys whistling off into the mooring area at Cuttyhunk. Similarly, I observed a bunch of the draggers had modern anchors, while several of the boats that held were on rather small looking Danforths. The most popular anchoring mistake I observe is not due to too little chain or a crappy anchor--it is due to not anchoring carefully by lowering the anchor, then paying out rode gradually, snubbing periodically to make sure the anchor is digging in and everything is in alignment. Then make sure you back down at around 5:1 before possibly shortening up if needed. Most people with windlasses just drop the anchor with a pile of chain, then half-heartedly back down eventually when they reach the end of the chain. Often this results in dragging the anchor a bunch until it orients itself and the chain straightens out, and then the boat is in the wrong place with a pile of weed balled up on the anchor. A lot of people just leave it like that if they aren't dragging at the moment, which can mean an unpleasant awakening at 2am when the wind pipes up in a thunderstorm.