How much chain..really?

[Dockhead]

Originally Posted by s/v Jedi

No need to feel like that... it was the old school thought for a long time. Steve Dashew, the designer of our boat, was one of the first to change over and reduce chain weight while increasing anchor weight. We have a 176lb anchor on 3/8” chain

When you search the forum there are hundreds of threads where this comes up. Here is some other info: https://www.petersmith.net.nz/boat-anchors/catenary.php

That's what I believed for years, but I think we have discovered that reality is more complicated than that.


Some ground-breaking work has been done on this subject just recently, discussed in great detail here, with mathematical proofs: https://www.cruisersforum.com/forums...pe-235053.html


Bottom line -- you certainly want the BFA (as Dashew calls it) -- no question that he's right about that. Don't make the anchor lighter in favor of the chain.


HOWEVER, it is not after all true, that catenary necessarily disappears in extreme conditions. It is more useful than the Peter Smith article simplistically implies. Catenary is very effective in deep water with heavy-ish chain even in extreme weather. After all. The effect declines with scope, so you should be in deep enough water that the scope is not extreme. Is it any coincidence that Dashew likes to anchor in very deep water on small scope? I think not, even if he doesn't himself understand why.



I myself had wondered for years why I felt so secure in 100 feet of water on 3:1 scope, much better than in 30 feet and 10:1. Now finally we know why.



Catenary is not effective in shallow water on large scope -- Peter Smith correctly describes that condition. But not others.

[introverted]

Most importantly, a big heavy anchor. I prefer one over sized for the boat. and enough chain to accommodate 7:1 scope in any anchorage you might visit. I have 200 ft of chain and a Vulcan 33. So, its easy to see how 300-400 ft of chain can be found on yachts that travel the world. even at 20 ft. depth (about the deepest anchorage in my area) + 5ft of freeboard I wouldn't even be able to put out 5:1 scope... another reason I prefer an over sized anchor vs one that is sized right. I'd rather have a big fat anchor than 10:1 scope. I anticipate I'll have at least 300ft of chain at some point.

[Dockhead]

Originally Posted by introverted

Most importantly, a big heavy anchor. I prefer one over sized for the boat. and enough chain to accommodate 7:1 scope in any anchorage you might visit. . .

I certainly agree about the big heavy anchor. We've been debating that recently in another thread. I'm firmly in Dashew's camp on that. The biggest and heaviest one you can practically carry and handle.



Plenty of chain, but don't fetishize scope. You don't really need 7:1 except in shallow water or if you are using rope rode.



"Plenty of chain" for most long distance cruisers means at least 300'. One day you will have to anchor in 30 meters of water; you need about 300' for that.

[thomm225]

Originally Posted by barnakiel

I hope you will be able to head S soon and we will be able to cross to your side too. It would be fun to meet somewhere in the glorious Windwards. We could then be comparing our anchors ... for a moment ... and spend the rest of the season sipping rhum. !



Cheers,
b.

That would be great, but it would most likely be late Fall as we are having temps here in the mid 90's now. It must be sweltering further South this year.........(my Jeep's thermometer said 102 yesterday when leaving the marina. They just put down a new black top parking lot)

Mid-September or later used to be nice in Pensacola,FL but that is prime hurricane season.......

[rslifkin]

Originally Posted by Dockhead

Plenty of chain, but don't fetishize scope. You don't really need 7:1 except in shallow water or if you are using rope rode.

Personally, I target based on 5:1 on the deepest water I plan to (or want to) normally anchor in. And the ability to go to 7:1 if needed without having to go too shallow if I ever needed for a bad storm. That provides enough rode that I should never end up wishing for more. With my current setup (about 375 feet usable at the roller), that gives me 5:1 in about 70 feet of water (about 5.5 feet of freeboard at the bow) and 7:1 in 48 feet.

[s/v Jedi]

Originally Posted by rslifkin

Personally, I target based on 5:1 on the deepest water I plan to (or want to) normally anchor in. And the ability to go to 7:1 if needed without having to go too shallow if I ever needed for a bad storm. That provides enough rode that I should never end up wishing for more. With my current setup (about 375 feet usable at the roller), that gives me 5:1 in about 70 feet of water (about 5.5 feet of freeboard at the bow) and 7:1 in 48 feet.

It doesn’t work like that, you need to use absolute numbers. Example: someone can plan or want to anchor in 20’ at most and that would be possible with your 5:1 min and 7:1 max rule of thumb. But when someone has to deal with 75’ deep anchoring, then the minimum of 5:1 immediately puts one at 400’ of chain minimum length. Even we have 400’ as maximum length and whenever anchoring in 50’ or more, 3:1 is more secure than 7:1 in 8’ water.

[daletournier]

Originally Posted by Dockhead

I certainly agree about the big heavy anchor. We've been debating that recently in another thread. I'm firmly in Dashew's camp on that. The biggest and heaviest one you can practically carry and handle.



Plenty of chain, but don't fetishize scope. You don't really need 7:1 except in shallow water or if you are using rope rode.



"Plenty of chain" for most long distance cruisers means at least 300'. One day you will have to anchor in 30 meters of water; you need about 300' for that.

I carry 90m of chain and habe had to anchor in 20-25m at times, in places like west Papua.

In the deep anchorages I'm not to worried about 5:1 ,I'm more concerned about having greater scope in the shallow anchorages. 3:1 or 4:1 has been enough for me in those 20m + anchorages.

I'm in the bigger anchor is better camp. Sometimes you just cant let out the scope you want due to swing room, it's like this in Tahiti right now. I'd like 5:1 out here BUT if we all did that here there would be problems thus I compensate with a oversized manson Supreme.

[Dockhead]

Originally Posted by s/v Jedi

It doesn’t work like that, you need to use absolute numbers. Example: someone can plan or want to anchor in 20’ at most and that would be possible with your 5:1 min and 7:1 max rule of thumb. But when someone has to deal with 75’ deep anchoring, then the minimum of 5:1 immediately puts one at 400’ of chain minimum length. Even we have 400’ as maximum length and whenever anchoring in 50’ or more, 3:1 is more secure than 7:1 in 8’ water.

Indeed!


It's really important not to fetishize scope; scope works differently in different depths. I was taught wrong by my Father in childhood -- in typical scope-fetish fashion, he believed that it's better to actually seek out shallow water in order to get up to at least 7:1, and in shallow water catenary doesn't work and anchoring is altogether less secure and less comfortable. It took me years to unlearn that crap.



Another thing is once you get to 400' of rode you very often get into really difficult issues of swing room too. In 75' of water 3:1 is absolutely fine. You start to need more than 100 meters of chain only in fairly rare circumstances.

[Pelagic]

Originally Posted by Dockhead

Indeed!


It's really important not to fetishize scope; scope works differently in different depths. I was taught wrong by my Father in childhood -- in typical scope-fetish fashion, he believed that it's better to actually seek out shallow water in order to get up to at least 7:1, and in shallow water catenary doesn't work and anchoring is altogether less secure and less comfortable. It took me years to unlearn that crap.



Another thing is once you get to 400' of rode you very often get into really difficult issues of swing room too. In 75' of water 3:1 is absolutely fine. You start to need more than 100 meters of chain only in fairly rare circumstances.

So true..... What you learn at basic boating levels is so different from what experience teaches you.

I've never understood the desire to anchor in shallow waters close to shore for comfort, catenary, privacy, and insect reasons, unless you had very limited land protection.

I think some force themselves into that situation by choosing too small or underpowered a tender that will not get onto a plane.

They then tend to crowd in close to the beach to make shore runs short, rather than anchor where you have room, privacy and plenty of depth.

[sailorboy1]

Originally Posted by NorthernMac

So I see posts for boats for sale, and folks talking about operations who have miles of chain

But really why?

I get it’s less likely to be compromised by a rock, but 200’ of chain? Weight/cost to benefit?

What’s the average depth, 7 scope, how much chain does one really need?

Doing the weight and balance of my cutter, I need more weight forward, but sail to displacement is a concern, if I could have less chain and have a water maker and AC/heatpump that seems like a better deal.

So outside of belt and suspender status, how much chain does one REALLY need for most ops, presume 30-50’ boat?

Also what about dyneema after chain?

You get the answer you hoped for yet

[AndrewA2]

Great post. And great links to other discussions.
However there is are a LOT of posts to wade through with miss information clearly being debated.
What is the general consensus?
To anchor in deeper waters with less scope and with a bridle to absorb the harsh jerking loads ?

[sailorboy1]

Originally Posted by AndrewA2

What is the general consensus?

mostly that anchors and chain sink

[AndrewA2]

Originally Posted by sailorboy1

mostly that anchors and chain sink

[darylat8750]

Originally Posted by JebLostInSpace

Wow, that was a fascinating read! It's suddenly perfectly clear that the benefits of heavy chain all disappear as soon as the rode is yanked tight - which of course is the only time you really care. Time to re-think my ground tackle approach again...

Welcome aboard! I too had to be dragged to this position. My boat was snatching the 200 foot chain to bar straight every wave one day and dragging the anchor a few feet with every slam. Finely got the bridle on to absorb the shock and we stopped dragging. Catenary just doesn't work when you really need it.

[darylat8750]

Originally Posted by Pelagic

Exactly!
The bottom line (pun intended), is to carry as much chain as the chain lockers will accommodate.

In the Pacific you have deep anchorages, same in Indonesia & PNG

You will need that ground tackle.

Also consider a deep water emergency drifting onto a Lee shore in moderate seas. (Example a jammed rudder hard over)

I have a joining link ready to attach the bitter ends of both anchor chains together.
You put out your primary anchor then join bitter end to the secondary so that all chain is let out on one anchor as you drift towards the Lee shore.

Extreme scenario but worth remembering and preparing for that option

"Also consider a deep water emergency drifting onto a Lee shore in moderate seas. (Example a jammed rudder hard over)"

I think this is not often given enough consideration. My friend was motoring up the coast near the Belieze / Mexico boarder in dead calm but with an onshore swell. Bad fuel went through all his spare filters. The water was deep enough that his anchor would not touch the bottom with all hi rode out. The swell was setting him slowly toward a reef. Neither the Belize or Mexican navy had any desire to help him but he eventually got the Belize guys to come help him. He would have given a lot for a couple hundred more feet rode.