All chain vs 100'

[noelex 77]

Originally Posted by Lodesman

In my own observations, I've sat out at anchor in over 20-25G30 and never saw my chain go taut, with 160' of 3/8" chain in about 15' of water.

You won't see the chain lift off the bottom near the anchor in only 20-25 knots of wind but this is not the sort of windspeed where you should be concerned about dragging.

[RaymondR]

Another matter to consider is the weight of all that chain when retrieving the chain and anchor in deep water. The DC motors on anchor winches do not have cooling. Enough chain to keep the rope rode above the nasties and rope back to the boat is a lot less load to retrieve.

[JPA Cate]

Originally Posted by RaymondR

Another matter to consider is the weight of all that chain when retrieving the chain and anchor in deep water. The DC motors on anchor winches do not have cooling. Enough chain to keep the rope rode above the nasties and rope back to the boat is a lot less load to retrieve.

And, an excellent reason to service the windlass, more heat being accrued when then is more friction. What Jim has always done, has worked so well for us, I would not be eager to add rope rode. The chain, so far, has always been retrievable, the windlass maintained, and it all just works.

Ann

[Kenomac]

Originally Posted by RaymondR

Another matter to consider is the weight of all that chain when retrieving the chain and anchor in deep water. The DC motors on anchor winches do not have cooling. Enough chain to keep the rope rode above the nasties and rope back to the boat is a lot less load to retrieve.

It's a good idea to size the windlass and chain accordingly. A manual windlass probably not such a good idea in deep water. Rope rode... never a good idea.

For those folks promoting the idea of a mostly rope rode, they'll change their minds the first time the rode gets cut or they pull it up partially worn through. I know I did. The first time I saw the rope half way worn through on our previous boat, went down the next day and purchased an extra 100ft of chain.

These chain vs rope rode discussions always remind me of some idiotic debate where one group will steadfastly argue that somehow it would be more advantageous to be in a traffic accident inside a Smart car vs a Hummer.

[crazyoldboatguy]

So, even this old Great Lakes sailor has come to the logical conclusion that all chain is best and, if traveling far, 300' seems the best bet. I have no problem with that. However, I also read that one should avoid connectors. Therein lies a problem. With my size boat, 3/&" chain will be the best bet (47' LWL, 36,000 lbs displacement ketch rig). When I look at suppliers - all of them sell half barrels (200') or full barrels (400'). Does that mean I have to buy 2 full barrels, use only the 300' from each and toss 2 100' lengths of perfectly good chain every time I replace it? Are there no connectors up to the task? If so, which ones?

[Matt Johnson]

Originally Posted by crazyoldboatguy

So, even this old Great Lakes sailor has come to the logical conclusion that all chain is best and, if traveling far, 300' seems the best bet. I have no problem with that. However, I also read that one should avoid connectors. Therein lies a problem. With my size boat, 3/&" chain will be the best bet (47' LWL, 36,000 lbs displacement ketch rig). When I look at suppliers - all of them sell half barrels (200') or full barrels (400'). Does that mean I have to buy 2 full barrels, use only the 300' from each and toss 2 100' lengths of perfectly good chain every time I replace it? Are there no connectors up to the task? If so, which ones?

Crosby's Missing Link tests at about the same strength as chain. We felt fine using one backed-up with a loop of dyneema.

Matt

[Lodesman]

Originally Posted by noelex 77

This is a commonly used formula that indicates when the last link of chain will just lift off the bottom:

F= W(L^2 - D^2)/2D
...
This visually shows there is very little sag or catenary.

Where did you source that formula? I've seen other discussions that have used other equations, that didn't quite fit, so I'm curious if this is truly applicable to anchor chain geometry?
Assuming it's correct, then it demonstrates the progressive effect on force required to overcome the catenary when more chain is put out - ie. doubling the amount of chain, quadruples the force required to lift it off the ground. Adding essentially weightless nylon will not do that.

It's a curious graph - while a 6:1 scope (48m of chain) is certainly sufficient for benign conditions, it is in no way suitable for 50 kt winds. Even as such, the cable is not bar taut and it seems obvious that adding chain at this point will see the catenary reappear.

Originally Posted by noelex 77

You won't see the chain lift off the bottom near the anchor in only 20-25 knots of wind but this is not the sort of windspeed where you should be concerned about dragging.

You've omitted the gusts, which were fairly long and actually hits peak speeds well above 30. In an open roadstead, with a sizable chop. The point was that it didn't even pull the last 40' out of the sand. Sorry I haven't anchored in a hurricane, but if I do, I'll be putting out the other 160' of chain, not sitting at 6:1 scope.

Actually the only time I've dragged, it wasn't very windy at all. Tight anchorage, strong reversing tidal current, and fairly scoured bottom: Allans Cay in the Bahamas. Due to proximity of other vessels, only put out 60' (4:1). We rode out the turn to flood OK, but on the switch to ebb started a very slow drag. Put out another 40' and we didn't budge after that. Admittedly, the reduced angle at the joining shackle might have been the deciding factor - I don't know how much that would've been improved if it had been rode instead of chain. Certainly 4:1 scope didn't do my Rocna any favours, especially given the bottom - thin layer of sand over hardpan. Obviously in those conditions, where the anchor can't dig in, the only added hold will come from deadweight and/or friction - something chain provides. But to each his or her own.

[hoppy]

Originally Posted by RaymondR

Another matter to consider is the weight of all that chain when retrieving the chain and anchor in deep water. The DC motors on anchor winches do not have cooling. Enough chain to keep the rope rode above the nasties and rope back to the boat is a lot less load to retrieve.

My 100m of 8mm chain weighs 140kg and with the 20kg anchor, that's 160kg. Not exactly much of a challenge for a 1000w windlass. It's the pulling the boat into a strong breeze or current that will be the challenge for the windlass and that will be pretty much the same whether you have all chain or not



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[cabo_sailor]

Interesting thread, thanks to all. It would seem that my own rig is pretty similar to what many of you have. Since I'm in the middle of a refit, I've also upgraded my ground tackle. Main bower is 200 ft 5/16 G40 chain backed with 100 ft 5/8 in 8 brait nylon. Second bower is 60 ft 5/16 in chain with 200 ft of 8 brait. I carry surplus fire hose for chafe protection and am installing a new Maxwell electric windlass. The Maxwell claims their patented "wave" design gypsy handles chain rope splices seamlessly. I don't worry too much about the weight since the CR 38's tend to squat a bit in the stern.

Common cruising grounds are west Florida and the Keys.


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[zboss]

Fatty Goodlander has an excellent (and cheap) book on anchoring that discusses chain and general rode at length. He addresses how to anchor in really deep pacific waters to avoid picking up mooring balls, how to deploy an anchor in very deep waters, and how to retrieve that anchor without blowing out your windlass.

We currently have a 50/50 mix of chain and rope but we are going 300 feet of smaller size all chain when we move to G70. Based on FG's sound advice from 50 years anchoring, we will be adding two additional 300' chain/rope lengths to our lockers alongside two more very large fortress anchors.

We originally thought that we would not need 300 feet for our anchors in the Bahamas but since we may end up finding ourselves there during hurricane season, we want to be prepared. We would rather have all that secondary chain and rope and never have to use it than not have it when we need it.

[Tinboat]

Originally Posted by Cadence

A winning combination for the east coast. The three strand hurts less when you need to cut loose a fowled anchor. Also don't need bolt cutters in a pinch. With a fin keel an anchor sally is a must with a rope rode. Even without a fin keel a sally take up shock and increases scope. JMHO

I know about a Sally Port, a Sally Lightfoot, Sally Forth, Sally Jessy Raphael, even Eric Clapton's Lay down Sally, but what is an anchor sally ...???

[sanibel sailor]

Originally Posted by Tinboat

I know about a Sally Port, a Sally Lightfoot, Sally Forth, Sally Jessy Raphael, even Eric Clapton's Lay down Sally, but what is an anchor sally ...???

kellet

[Bulawayo]

Originally Posted by Lodesman

While I'll agree that the ideal is a horizontal pull (0º angle at the shank) and that the hold of the anchor is decreased at larger angles, I submit that a few degrees difference between 7:1 and 10:1 scope has a negligible effect on the holding power of the anchor. Do you have test data that compares anchor pull to shank angle? The added weight of chain is more likely to ensure that desired horizontal pull.


I submit if you have most of the chain off the bottom, you're using too little.

Lodesman,
I agree with you. The more chain, under adverse conditions, the better. There is no getting away from the fact that the weight of the chain helps the catenary and whilst it is accepted that even the chain can pull taut, just like the warp can, what is being overlooked is that the physical weather conditions need to be more severe to achieve this. In other words, stronger wind/waves. We also often meet people that ask us about our alleged oversized anchor. On our 45ft cat we have been using an 85lb Mantus which is what the manufacturer ID'ed as a storm anchor for our boat. (We usually bring this back to the sail locker when off-shore) We have never understood why many other cruisers only bring their storm anchor out when actual conditions warrant it? We have been peacefully snoozing at anchor when a squall has hit without us being aware of its approach. When you go from 15knots of night breeze to being clouted by 60-80knot blasts without warning it is as scary as it gets. Seeing other boats dragging and talking with their skippers afterwards and hearing their stories would take up many pages. Having experienced this a few times we routinely use an anchor sized for 'storm' use. How much fun is it to try and set a storm anchor in the middle of such conditions? Just about impossible in reality, besides the fact you might be dragging already. This also required us to upgrade our windlass. To us, having a long chain and good anchoring gear is a lot less hassle than an insurance claim (a lot of cruisers where we have been are not even insured).
As we are presently looking for our next cat, we shall be increasing our main chain to 300ft as we hope to finally make it into the Pacific, but shall still adopt the storm sized anchor as our main hook.

[Bulawayo]

Originally Posted by noelex 77

I am not sure why 7:1 and 10:1 are specifically being discussed. The general principle of increasing an anchor's holding power as you let out more rope (or chain) rode, is true irrespective of scope. This is contrary to your suggestion that letting out more rope "does nothing to improve the holding power of the anchor and only increases the diameter of your swinging circle."

The law of diminishing returns starts to take effect at larger scopes and once the angle of gets around 5° the benefits become very slight. So most feel there is little practical benefit over around 10:1 to 14:1 depending on who you believe.

To answer your specific example, several anchor manufacturers suggest the holding power increase from 5:1 to 7:1 is about 15%. I have no way of verifying these numbers, but they seem a reasonable ball park figure to me.

I am curious to understand that while you believe "a few degrees difference between 7:1 and 10:1 scope has a negligible effect on the holding power of the anchor". You nevertheless feel that the very small change in angle from chain catenary seen in strong wind and moderate depths is so essential.

If anchored at 10:1, which would be reasonable in strong wind, the maximum change in going from rope with zero weight to a hypothetical infinitely heavy chain would be only 5.7° and this theoretical maximium is independent of all factors apart from bottom slope.



It would be nice to keep the chain on the bottom and the pull on the anchor at 0° relative to the seabed, unfortunately that is just not practically possible in strong wind. This can be shown by theoretical calculations or practical observation.

It is possible in light to moderate winds, but holding in these conditions with a good anchor is not normally an issue.

You are blurring the most obvious fact. Much of what you have written is in direct contrast to what 'Practical Sailor' have published. Writing hypothetical equations does not make them fact. The blurred issue is that to straighten a chain takes worse weather conditions that it does to straighten a rode; all matters being equal, of course. The physics of this you shall undoubtebly be aware of - but this seems to have been overlooked.
Not withstanding, of course the swinging circle shall also increase with the longer rode length and the vulnerability of the line cannot be overlooked.
Let me ask you a question, please. What do you have on your boat and what are your cruising area's? Perhaps that influences your statements?
We have never made it as far as the Pacific, but we have been reliably informed that is wise to have (circa) 300ft of chain. This we intend to have on our next cat. We shall still have 30-50 meters of warp backing that up as well.

[noelex 77]

I use all chain. I have 100m (330 feet).

I think for a long distance cruising boat, all chain is far more preferable. There is too much risk of abrasion from rock, coral and man made debris. See my post #24. It is also important in crowded anchorages to swing like your neighbours and these are likely be on all chain rode.

However, I don't believe the chain contributes much to my anchor's holding ability. This can be shown mathematically or shown practically by observing the rode in strong wind conditions. The effect of catenary is largely lost in strong wind unless the anchorage is deep.

That is not stay the chain weight is totally useless in assisting the anchor's holding ability. It does help in the initial setting phase of the anchor, it also makes a practical contribution in deep anchorages and especially if you are forced to use a short scope when the upwards pull of rope ride would be significant. Finally, if the substrate is very poor and there is a risk of dragging in light or moderate conditions once again chain is of practical help. However, even with these exceptions, the heavy weight of chain gives a very poor rate of return in terms of the extra holding power for the additional weight.

The 200 + kg of my chain is earning its keep in terms of abrasion resistance, but not in terms of holding ability.

Because chain is far preferable for abrasion resistance this can perhaps be viewed as largely academic argument, but it does have practical implications. The best practice is for boats to use chain as thin as possible providing it meets the required strength, adding some of the weight savings to the anchor. This is still resisted by those who feel chain weight is essential for good holding.