Has anyone ever tried aluminum chain?

[noelex 77]

Originally Posted by wholybee

In my example, that shown in your picture won't happen, because the chain is on the ground, and the rope is not. So, you could imagine the chain transitioning to rope just outside the picture frame, and would be fine.

I do agree with your comments about modern oversized anchoring gear having adequate holding power at shorter scopes, but unless you are restricting the rope length to not much more than the depth of the water I think you are being optimistic expecting the rope to never touch the bottom. In light or even moderate winds at least the rope near the rope chain splice will be on the bottom. Note the angle of the chain in the photo. The rock was close to the bow of the boat. The length of chain between the rock and the boat was little more than the depth of water

Strong wind is not always constant. In some parts of the world, squalls are common with periods of little wind followed by strong wind. Suitable scope for the stronger wind needs to be deployed, especially when leaving the boat. Most of the rode, even if rope, will be on the bottom during the lulls. Likewise, if the wind direction alters significantly, especially if it switches 180°. This is prime time for the rode to become caught on debris or under rocks.

Keep in mind that if the rope rode is cut, the resultant drag will be very rapid. There is no longer an anchor or even any chain to slow the boat down. It can be difficult to recover from this situation in time to prevent damage.

On some small and lightweight cruising boats it is necessary to use rope rode, but it does impose some extra risk. All chain rode is the default standard on cruising boats for good reason.

[s/v Jedi]

The weight of the rode is not important: weight must be put into the anchor, not the rode.

But abrasion resistance is very important and this is where steel chain shines.

So the best choice would be the lightest steel chain, which is why G7 is popular now. There was a time that you couldn’t just buy galvanized G7, we have had to special order that. It was the demand for it to be used as anchor rode that convinced manufacturers to start selling it galvanized.

But there’s another point to consider and that is how to connect it to your anchor. Because you go down in size, the shackle won’t fit anymore. For this reason I special order the rode with enlarged end-links (both sides so the chain can be turned end for end).

I recommend a Crosby shackle and a Chicago Hardware swivel. Both from galvanized steel, both available from Defender. This is what pro’s use instead of precious shiny thingies.

[Lodesman]

Originally Posted by sailingharry

Assuming that somehow the catenary is important, he would have a hundred feet of chain out. He would have more chain and more of that effect with 100 ft of chain and 100 ft of dyneema then he would when anchored in 10 ft of water and only 75 ft of chain out.

A big part of why I don't really subscribe to the catenary shock absorbing effect is anyone who uses chain has to put in 20 to 30 ft (or more) of nylon snubber to reduce the impact and jerk associated with an all chain rode. If the catenary really reduced the impact load, you wouldn't need the nylon. The jerk comes when the catenary is essentially gone.

One of the advantages of using nylon in a mixed rode, is that it has elasticity and provides that shock absorption, so a snubber isn't required.

Originally Posted by rslifkin

In deep water catenary is definitely a factor. In shallower water you can pull an awful lot of chain fairly straight in any decent breeze.

I use all-chain, and no snubber. I secure the anchor chain to the forward cleats with short but fairly stout nylon strops, that allow about a foot or so of stretch. Between catenary and the shock-absorbing effect of the nylon strops, I've not experienced impacts or jerking. Now I haven't weathered a hurricane, but have sat comfortably through 40 kts sustained with gusts to 50 or so.

With a suitable length of chain out, there is virtually no way that catenary would be gone, even in shallow water. In shallow water, the chain is sitting on the bottom, but as tension increases, the hanging chain basically grows to meet the demand. In effect, gravity is doing the job of the catenary.

This goes back to my original point - if you know the anchor chain is still on the seabed at the anchor, then there is catenary in the hanging part of the chain. After the point at which the chain entirely lifted off the seabed, the catenary will reduce until it is essentially incapable of absorbing the shock loads, and then you'll feel the impacts and jerks.

[rslifkin]

Originally Posted by Lodesman

One of the advantages of using nylon in a mixed rode, is that it has elasticity and provides that shock absorption, so a snubber isn't required.



I use all-chain, and no snubber. I secure the anchor chain to the forward cleats with short but fairly stout nylon strops, that allow about a foot or so of stretch. Between catenary and the shock-absorbing effect of the nylon strops, I've not experienced impacts or jerking. Now I haven't weathered a hurricane, but have sat comfortably through 40 kts sustained with gusts to 50 or so.

With a suitable length of chain out, there is virtually no way that catenary would be gone, even in shallow water. In shallow water, the chain is sitting on the bottom, but as tension increases, the hanging chain basically grows to meet the demand. In effect, gravity is doing the job of the catenary.

This goes back to my original point - if you know the anchor chain is still on the seabed at the anchor, then there is catenary in the hanging part of the chain. After the point at which the chain entirely lifted off the seabed, the catenary will reduce until it is essentially incapable of absorbing the shock loads, and then you'll feel the impacts and jerks.

Judging by the angle of the rode, when I power set my anchor a few days ago in 21 feet of water (add another 6 for freeboard) with 90 feet of chain and 20 feet of nylon out, the rode was pulled damn near straight, and adding a little extra power couldn't straighten it much more. Now mind you, my typical power set is equal to at least 30 kts of wind. The 15 kts we actually had left plenty of chain on the bottom.

If you're never pulling the rode tight and not getting shock loads, either you're always anchoring in deep water or you're using a crazy amount of scope and would never fit reasonably into an anchorage with other boats.

[Lodesman]

Originally Posted by rslifkin

Judging by the angle of the rode, when I power set my anchor a few days ago in 21 feet of water (add another 6 for freeboard) with 90 feet of chain and 20 feet of nylon out, the rode was pulled damn near straight, and adding a little extra power couldn't straighten it much more. Now mind you, my typical power set is equal to at least 30 kts of wind. The 15 kts we actually had left plenty of chain on the bottom.

If you're never pulling the rode tight and not getting shock loads, either you're always anchoring in deep water or you're using a crazy amount of scope and would never fit reasonably into an anchorage with other boats.

Do you use any rode apps? I don't know your parameters, but using my boat's parameters with your numbers above - the diagram at setting shows the nylon dead straight with a small curve in the chain. So there is catenary, but it's essentially useless with an angle over 12º above horizontal from the anchor. But for the 15 kts of wind, it is pretty close to being the optimal rode length. Assuming 'optimal' means not putting out more chain than is absolutely necessary for the conditions. That doesn't provide a "safety factor."

I don't get this idea that 150 ft is "crazy amounts of scope." If you're anchoring closer than that to other boats, you have to accept a lot of additional risk. Me, I prefer to anchor further away from the crowds.

[rslifkin]

Originally Posted by Lodesman

Do you use any rode apps? I don't know your parameters, but using my boat's parameters with your numbers above - the diagram at setting shows the nylon dead straight with a small curve in the chain. So there is catenary, but it's essentially useless with an angle over 12º above horizontal from the anchor. But for the 15 kts of wind, it is pretty close to being the optimal rode length. Assuming 'optimal' means not putting out more chain than is absolutely necessary for the conditions. That doesn't provide a "safety factor."

I don't get this idea that 150 ft is "crazy amounts of scope." If you're anchoring closer than that to other boats, you have to accept a lot of additional risk. Me, I prefer to anchor further away from the crowds.

150 feet isn't crazy in 20 or 25 feet of water. But in 10 feet it's a whole lot more than anyone else will have out.

In the example I gave, the anchor set fine and held a pull equal to at least 30 kts (probably closer to 35 or 40) despite the rode angle. So for the expected weather it was more than good enough with plenty of safety margin. I'm sure I could have given the engines a bit more throttle and still held, I just didn't have a reason to.

[Lodesman]

Originally Posted by rslifkin

150 feet isn't crazy in 20 or 25 feet of water. But in 10 feet it's a whole lot more than anyone else will have out.

Has the same swinging circle. Why would I care what anyone else will have out? Just how close to other vessels, do you want to anchor?

[s/v Jedi]

You don’t need apps

Up to 20’ depth use 5:1 scope with a minimum rode length of 60’. Between 20’ and 40’ depth use 4:1 scope. Above 40’ use 3:1 scope unless your 400’ rode is the maximum.

Any decent anchor will perform good with this setup. Better anchors can be lighter than old school anchors but scope will work for all.

If the seabed provides good holding or the weather is settled, you can reduce scope. Experience will show how much.

[boatpoker]

Surprised that no one has pointed out that aluminum sitting in the bottom of a wet anchor locker will rapidly corrode due to poultice corrosion. It will fail before you get a chance to stress test it.

[s/v Jedi]

Originally Posted by boatpoker

Surprised that no one has pointed out that aluminum sitting in the bottom of a wet anchor locker will rapidly corrode due to poultice corrosion. It will fail before you get a chance to stress test it.

Except of course when the anchor locker is made of fiberglass or some other non-porous material. I have seen aluminum (not chain) do great when set on Treadmaster.

[boatpoker]

Originally Posted by s/v Jedi

Except of course when the anchor locker is made of fiberglass or some other non-porous material. I have seen aluminum (not chain) do great when set on Treadmaster.

Perhaps in a well designed, well drained rode locker but certainly not if the chain is lying on wet rope, rags or the wet dirt and weeds I see in the vast majority or rode lockers.

[fgd3]

What do you guys think about this? It's even lighter than aluminum and has superior corrosion resistance. It costs a lot less, too.


https://www.homedepot.com/p/Everbilt...E&gclsrc=aw.ds

[Karanga]

Originally Posted by fgd3

What do you guys think about this? It's even lighter than aluminum and has superior corrosion resistance. It costs a lot less, too.


https://www.homedepot.com/p/Everbilt...E&gclsrc=aw.ds

Yup - that nicely takes the idiocy of this discussion to its logical extreme.
Thank you.
It might even float, and therefore there's little risk of abrasion from pesky rocks and coral.

[thinwater]

Originally Posted by fgd3

What do you guys think about this? It's even lighter than aluminum and has superior corrosion resistance. It costs a lot less, too.


https://www.homedepot.com/p/Everbilt...E&gclsrc=aw.ds

I was in a refinery once, where they used that for safety chains on catwalks, WAY up in the air. . Even weaker once the UV got to it. Lean against it and you die.

[Lodesman]

Originally Posted by s/v Jedi

You don’t need apps

Up to 20’ depth use 5:1 scope with a minimum rode length of 60’. Between 20’ and 40’ depth use 4:1 scope. Above 40’ use 3:1 scope unless your 400’ rode is the maximum.

Any decent anchor will perform good with this setup. Better anchors can be lighter than old school anchors but scope will work for all.

If the seabed provides good holding or the weather is settled, you can reduce scope. Experience will show how much.

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?