Cruising Anchor Chain Length

[evm1024]

Originally Posted by navman

I sat out Hanna in 2008 in the Bahamas at Anchor, and the deck hardware (very robust installation on an S&S yacht) took a beating, and I had lines led aft to the primaries from the deck cleats.

In the gusts we would surge aft noticably, and I am thankful that chain made up only a small percentage of the overall combination which began with a 90lb anchor, which held without dragging. It was so well set after the storm I had to dive on it to dig it out.

Had I used all chain I am confident some of the stronger gusts would have produced peak loading on the deck hardware that would have either damaged it, or damaged the deck. As you know, S&S yachts are not built by yards that skimp on build quality, and Rod was maniacal about engineering the related structures.

Yes, it is common practice to use a snubber with an all chain rode.

[navman]

Originally Posted by evm1024

Yes, it is common practice to use a snubber with an all chain rode.

I suggest you ride out a hurricane at anchor and see if the snubber lasts more than 15 seconds.

I've been crossing oceans for more than three decades under sail, and have anchored more times than I could ever recall, and frankly the thought that a snubber could provide any benefit on a yacht displacing 10+ tonnes in winds over 30 knots is absurd.

In light to moderate conditions a snubber will keep the roller from waking you, but beyond that any practical benefit in high winds is purely imaginary.

The best practice in my experience is a rode which uses a combination of chain and high elsaticity rode to eliminate shock loading both anchor and deck hardware.

[evm1024]

Originally Posted by navman

I suggest you ride out a hurricane at anchor and see if the snubber lasts more than 15 seconds.

I've been crossing oceans for more than three decades under sail, and have anchored more times than I could ever recall, and frankly the thought that a snubber could provide any benefit on a yacht displacing 10+ tonnes in winds over 30 knots is absurd.

I have no intentions of riding out a hurricane if I can avoid it. And if I were to try to ride out a hurricane it is very likely that I would have a snubber of a length in relation to the forces expected. Please do not assume what kind of snubber I might use.

Oh and by the way you did have a snubber - You had 90' of chain out and a robust snubber for the rest of the length of your rode. You may not think of it of a snubber but that is what it was. Surely it was not there only for scope.

[navman]

Originally Posted by evm1024

Oh and by the way you did have a snubber - You had 90' of chain out and a robust snubber for the rest of the length of your rode. You may not think of it of a snubber but that is what it was. Surely it was not there only for scope.

You have a wonderful talent for the almost obvious, but a snubber is a secondary device, not a properly engineeded single anchoring system designed to incorporate sufficient elasticity.

When providing advice to people like the OP it's important to be specific, because your advice can lead to the loss of their vessel or life. Something I have learned from years in legal command positions on yachts.

A longer snubber, as you mention, complicates the anchoring system, increases the liklihood of fouling, and if not carefully or deliberately secured over a sufficient length of rode, be subject to extreme chafing itself at the attachemnt point in any serious conditions.

Once your snubber fails you're back to an insufficiently elastic anchoring system, and have put your vessel and crew at risk.

No one wants to be anchored in a hurricane, but with climate change, bad things CAN happen to good people.

Read Peter's article, he knows his stuff, and has anchored in conditions along the Patagonia coast that would curl the hair on your back, and has many years desiging anchoring systems that many have relied on with GREAT success.

[evm1024]

Originally Posted by navman

You have a wonderful talent for the almost obvious, but a snubber is a secondary device, not a properly engineeded single anchoring system designed to incorporate sufficient elasticity.

When providing advice to people like the OP it's important to be specific, because your advice can lead to the loss of their vessel or life. Something I have learned from years in legal command positions on yachts.

A longer snubber, as you mention, complicates the anchoring system, increases the liklihood of fouling, and if not carefully or deliberately secured over a sufficient length of rode, be subject to extreme chafing itself at the attachemnt point in any serious conditions.

Once your snubber fails you're back to an insufficiently elastic anchoring system, and have put your vessel and crew at risk.

No one wants to be anchored in a hurricane, but with climate change, bad things CAN happen to good people.

Read Peter's article, he knows his stuff, and has anchored in conditions along the Patagonia coast that would curl the hair on your back, and has many years desiging anchoring systems that many have relied on with GREAT success.

I'm not really sure where you are coming from - it appears that you are picking a fight. I would rather not be involved in that.

A properly engineered single anchoring system, give me a break. You have a boat and you have what you consider a well engineered system. Fantastic! Please do tell us about your system and why you think it is better than all others. We will listen. We will even listen when you speak as if you have the last word on anchoring and anchor systems.

Do let me correct you - I've not offered any advise on how to anchor to anyone let alone the original poster.

You offer up your professional (legal command et al) history thinking that that gives you a better understanding failing to understand that many of us have had (or do have) Masters Licenses (I've let mine expire, I no longer need or want it).

You offer up Peter as an authority which is well and good. I've read Peter's article and was not commenting on it. But I also remember Peter's comments prior to and after the (shall we say) the Shank debacle.

Funny thing, the other day, I went to a fight and a hockey game broke out. Let's see if we can play hockey.

[noelex 77]

Originally Posted by navman

I've been crossing oceans for more than three decades under sail, and have anchored more times than I could ever recall, and frankly the thought that a snubber could provide any benefit on a yacht displacing 10+ tonnes in winds over 30 knots is absurd.

In light to moderate conditions a snubber will keep the roller from waking you, but beyond that any practical benefit in high winds is purely imaginary.

The best practice in my experience is a rode which uses a combination of chain and high elsaticity rode to eliminate shock loading both anchor and deck hardware.

I don’t understand why you feel “a combination of chain and high elasticity rode” will be superior and produce fundamentally different behaviour when compared to a long snubber and all chain rode.

You seem to feel the elasticity of a snubber cannot provide any benifit, but “high elsaticity rode to eliminate shock loading both anchor and deck hardware” is important.

The major difference I would suggest is that if the rope portion breaks, the boat with the all chain rode and snubber has a backup (the chain). Of course the price for this extra security is considerable extra weight.

[Dockhead]

Originally Posted by FranklinGray

First off, chain never gets bar tight. That is impossible. It may be close to straight, but never straight.

"Bar tight" does not refer to straightness, but to behavior. This was explained above. We talk about an anchor chain's being "bar tight" when the catenary has been pulled out of it to the extent that catenary no longer provides any useful energy absorption. At the same time, the chain will not be sagging enough to provide any benefit to the angulation of the anchor. For all practical purpose, it is like a bar (at least in the pull direction).

Originally Posted by FranklinGray

Example of my boat in 40 knots of wind:

With 70 of chain out, there will be .5 feet of sag. With 200 feet of chain out, there will be 4 feet of sag. That is a big difference. Weight makes a lot of difference. That is the reason my anchor will hold in 35 knots of wind with just 3:1 scope in deep water...my chain has a lot more weight on it so the pull direction is not so bad.

And just for your understanding, my boat will produce 1,800 lbf at 40 knots (40x40 x.00256 x (55x6 (freeboard) + (mast and rigging 30)) x 1.2 (Drag) This is calculated to show the worst, when the boat is exposing roughly 40% of it's hull to the wind.


https://www.spaceagecontrol.com/calc...tton=Calculate

You are applying a static load calculation to a dynamic situation. This is an error. The ABYC formula gives a much better representation of the real life loads, as has been confirmed over and over again by people with load cells. The ABYC formula gives a somewhat but not extremely conservative representation of the peak dynamic loads encountered in real life anchoring, excluding overloads generated by uncontrolled yawing or big wave action.


And even at 1800lbf (816kgf), in your example, do you think you have "catenary"? How much energy can still be absorbed by the chain when it is sagging only 15cm over 21 meters? How much is the angle on the anchor improved? It's behaving already like a bar. And if it were otherwise, you wouldn't need a snubber.


John on Morgan's Cloud calculated that by about one tonne of force on a 60 meters of 3/8" chain, catenary is absorbing even less energy than the elasticity of the steel. https://www.morganscloud.com/2018/12...hen-it-doesnt/


And as Peter Smith said in "Catenary & Scope in Anchor Rode":



"The catenary from the chain is often assumed to be a good shock absorber, in addition to lowering the angle of pull on the anchor, as it takes some time to straighten. However, this is a fallacy, as this quasi 'spring' disappears in bad conditions when it is most needed. A proper shock absorber is a nylon snubber or similar. On larger boats it may not be necessary in all conditions, while on smaller boats it is almost always advisable."


https://www.petersmith.net.nz/boat-anchors/catenary.php

[Dockhead]

Originally Posted by noelex 77

I don’t understand why you feel “a combination of chain and high elasticity rode” will be superior and produce fundamentally different behaviour when compared to a long snubber and all chain rode.

You seem to feel the elasticity of a snubber cannot provide any benifit, but “high elsaticity rode to eliminate shock loading both anchor and deck hardware” is important.

The major difference I would suggest is that if the rope portion breaks, the boat with the all chain rode and snubber has a backup (the chain). Of course the price for this extra security is considerable extra weight.

I was also puzzled by this.

Using a snubber on an all-chain rode is better practice than using a mixed rode, although of course plenty of people use mixed rodes with good results.

The main reason why it is better practice is chafe. In really bad conditions it becomes more or less impossible to ensure that the elastic part of the rode doesn't chafe through or fail due to cyclic loading (as nylon notoriously does). Whoever has had a nylon snubber or nylon anchor rode fail in a storm, hold your hand up (I've got both hands up). If you're on a mixed rode without a snubber, this results in losing the ground tackle. If you are on all-chain with a snubber, you can rig TWO snubbers, which is what I do, and you can change them one by one as they chafe through or fail.

Best practice of all would be to provide the snubbers with dyneema leaders so that the nylon doesn't touch any part of the boat. I've never actually seen that in practice, but I seem to remember that Evans Starzinger had a setup like that.

And as you say, if the elastic part fails and it's a snubber on all-chain rather than a mixed rode, you're still attached by the chain and you might have a chance to get a new snubber on, rather than losing your ground tackle and perhaps your boat, if that happens with a mixed rode.

Further, the rope part of a mixed rode might not run perfectly through your windlass.

Using a snubber on all chain is better practice. IF of course you can carry that much chain. The only good reason to use a mixed rode in my opinion is to form a long enough rode when you can't carry enough chain.

And lastly: If you do have a mixed rode, you shouldn't have nylon in it anyway. Nylon is notoriously vulnerable to chafe and sudden failure due to cyclical loading, and loses strength when wet. Here's is Dashew's warning on using nylon in the anchor rode: https://www.petersmith.net.nz/boat-a...right-rode.pdf. My rope rodes are all polyester.

[jmh2002]

As soon as I saw someone write "First off, chain never gets bar tight. That is impossible" I sighed but didn't really have the energy to bother countering this.

Thanks Dockhead for setting the record straight, as well a reminder to everyone that using more than one snubber is possible too.

I used to do this often as soon as a bit of a blow was forecast. It just seems like normal good seamanship to double up and spread the load, as well as giving options in case of a chafe, a failure, etc.

[Exile]

Yes, thanks Dockhead and others for the clarity of the recent responses. And for getting back to hockey.

One minor clarification: I assume when you guys recommend two snubbers in strong/difficult conditions you're referring to a bridle set-up? That's what I've used anyway (along with chafe guards where the snubbers pass through the bow chalks) during the several times I've experienced such conditions thus far.

[Group9]

Originally Posted by navman

I suggest you ride out a hurricane at anchor and see if the snubber lasts more than 15 seconds.

I've been crossing oceans for more than three decades under sail, and have anchored more times than I could ever recall, and frankly the thought that a snubber could provide any benefit on a yacht displacing 10+ tonnes in winds over 30 knots is absurd.

In light to moderate conditions a snubber will keep the roller from waking you, but beyond that any practical benefit in high winds is purely imaginary.

The best practice in my experience is a rode which uses a combination of chain and high elsaticity rode to eliminate shock loading both anchor and deck hardware.

I've anchored our boat (and helped anchor friends boats) in several hurricanes. There is no reason for a snubber to fail in Cat 1,2, or 3 winds if it is of the proper size and, most importantly, has proper chafe protection.

Cat 4 and above? It's all mostly luck after that, anyway, IMHO and experience.

[s/v Jedi]

On snubbers, y’all did not pay enough attention so here it goes again:

Nylon 3-strand stretches about 20% at a load of 50% of it’s breaking strength. This means that if you have 15’ of snubber between chain and cleat, it will stretch more than 3’ before it breaks. (with 5m snubber, it stretches more than 1m)

So, here’s how to deploy the snubber after setting the anchor: attach it to your chain and let out more chain until you have 15’ (5m) out. Then tie the snubber to a bow cleat. Now, feed 3’ (1m) extra chain out, then engage the chain stopper.

That’s it, no more worries. The snubber will work 100% but not break unless it is worn out. Checking for chafe etc. and replace in time. Don’t bother with chafing gear, the snubber itself is the chafing gear, the disposable component of the system. You need to replace it periodically anyway, before it has become stiff and lost it’s stretch. Without stretch it doesn’t work. Too large a diameter or too old and it’s a fail. Get it right

[daletournier]

Originally Posted by Exile

Yes, thanks Dockhead and others for the clarity of the recent responses. And for getting back to hockey.

One minor clarification: I assume when you guys recommend two snubbers in strong/difficult conditions you're referring to a bridle set-up? That's what I've used anyway (along with chafe guards where the snubbers pass through the bow chalks) during the several times I've experienced such conditions thus far.

I've only recently started using the bridle type arrangement, attaching it with a soft shackle.

I find it limits the yawning quite abit which can be quite alot on my boat.

I still just use a single line snubber if in a calm or short stay Anchorage.

My only dislike with the bridle setup is when theres no load it can rub against the antifoul .

[jmh2002]

You could say that my description in effect acted as a bridle but it was 2 separate components (and in case of some problem, you can always just add another).

So each snubber could be set, adjusted, removed, etc, individually.
NB: also they could both be set on one side of the bow too if conditions were causing the boat to always lay or blow off to a certain side. This also just might work better on some boats where an asymmetrical bow layout is causing an issue.

And in my case they were also different materials too (actually I had a few different snubber lines for different use cases).

I found it useful for comfort in certain conditions to have the initial 'soft take up' of the single every day weight snubber, but then as an extra big gust came through and the every day weight snubber stretched out some of the load was then transferred onto the heavier 'windy weight snubber'.

This avoided most the uncomfortable jerking and snatching that can sometimes occur but still ensured that the heavier loads were considered too.

In both cases this was before the slack bight of chain (as mentioned by Jedi) took any load.

All of this could be adjusted for preference though, because it was 3 individual 'lines'.

- every day snubber
- windy weight snubber
- chain

NB: in hurricane type conditions different snubbers again would be used.

I think that snubbers are easy and light to carry and you can mix and match them to the conditions and the situation as necessary.

[Auspicious]

Well jeepers. It's Boat Show time here in Annapolis so I'm not keeping up. Once again, get yourself a drink of choice and perhaps a snack. *grin*

Originally Posted by Dockhead

Going out to sea and heaving to is not an option, because there is ice in the water.

I take issue with this. You got it. Why can't you get out? There was ice in the water when you entered the fjord, there is ice in the water when you leave (unless you're there so long there are seasonal issues, or a REALLY long time climate change issues *grin*).



That is not to say that slowing down to increase available reaction time is not good seamanship. How fast are you going hove to? Less than one knot?



I follow and agree with the rest of your post, but not with this. "When in doubt, go out."

Originally Posted by conachair

Remember the catenary effect works different at different depths

Not true at all. The equations are just the same. The implications of the numbers to seamanship may be different (less scope at deeper depths). Catenary works the same both statically (like power lines) and dynamically (like anchor rode).

Originally Posted by conachair

https://www.desmos.com/calculator/mpbs9et8ta.

Yet another improper use of scope. I haven't checked the math in the spreadsheet, but frankly anyone that uses water depth as the independent variable is off base - it's water depth plus height of bow roller. In really deep anchorages it doesn't matter so much but for common water depths it matters a LOT.

Originally Posted by dadster3

The really serious cruisers I have talked to--and by serious I mean those who cruise full time, many of whom make their living writing, teaching or consulting about cruising--I don't think I have met a single one that carries less than 300 ft. of G4, usually 3/8" or 1/2". If you are a local weekender or occasional sailor, that's probably overkill. It's a lot of weight--300 ft of 3/8 weighs over 600 lbs.--but that extra weight adds to the holding power at anchor. It keeps the chain on the sea floor and the pull on your anchor more horizontal.

Dockhead among others have gone over this a number of times, with footnotes. The weight of chain is really not relevant. Look at the work of Alain Fraysse. If you're going to add weight, add it at the anchor. Not the chain. Not with a kellet.



The whole point(s) of chain are simple: chafe resistance, good mechanical grip for windlass gypsies, corrosion margin over time. As S/V Jedi said the issue is strength not weight. Here is the good news - for once the best system is the simplest.

Originally Posted by Black Eagle

Does it works without problems on gipsy?
If yes it's realy great!

Without problems? No. As S/V Jedi stated you have to slow down and watch it. In addition the use of such chain splices adds weight (ha!) to his preference for vertical windlasses. The increased engagement in the gypsy makes getting the chain splice around less troublesome.

Originally Posted by FranklinGray

First off, chain never gets bar tight. That is impossible. It may be close to straight, but never straight.

Okay. I'll pile on. No. You are correct that it isn't straight. You are not correct that the deflection makes any difference whatsoever. At the point you describe there is more elongation and therefore shock absorption from the chain stretching (look up Young's modulus) than from catenary.

Originally Posted by FranklinGray

And just for your understanding, my boat will produce 1,800 lbf at 40 knots (40x40 x.00256 x (55x6 (freeboard) + (mast and rigging 30)) x 1.2 (Drag) This is calculated to show the worst, when the boat is exposing roughly 40% of it's hull to the wind.

Unless you have a lot more discipline than most cruisers you are grossly underestimating windage. Jugs? Dinghy? Davits? Radar? Jib furled tightly? Main tied down really well? That dodger you added? Bimini? Flag halyards? All the extra electronics like sat phone antenna, WiFi antenna, AIS antenna? Outboard on the pushpit? Life saving items? That stuff adds up and has real world effects.

Originally Posted by navman

I suggest you ride out a hurricane at anchor and see if the snubber lasts more than 15 seconds.

Both the numbers and real world practical experience do not bear you out. Chafe protection is just as important on a mixed rode as with a snubber and the failure modes for a mixed rode--as others have noted--is more catastrophic than a snubber failure.

Originally Posted by s/v Jedi

So, here’s how to deploy the snubber after setting the anchor: attach it to your chain and let out more chain until you have 15’ (5m) out. Then tie the snubber to a bow cleat. Now, feed 3’ (1m) extra chain out, then engage the chain stopper.

I do mine a little differently but the concepts are the same. When heavy weather is expected I use two snubbers. I cleat them one on each side but as others have noted putting both on the same side is fine. I put the first about 1'(25 cm) further down the chain than the second. The first one is set up about a meter or two longer than the second. My boat does hunt (or sail) at anchor and I find hanging off a snubber to one side reduces that. If my chafe protection on the short snubber the long one picks up. If that fails I hang on the chain until I have a chance to respond and rerig. I have a plan for that but won't waste your time; it's never come up despite four or five hurricanes.