Cruising Anchor Chain Length

[dfelsent]

Originally Posted by Dockhead

Sleep at anchor with a gale blowing? I don't. Regardless of what kind of chain I'm on.

I slept poorly last night ashore with Moonbeam on her home mooring. Blowing 40 gusts to 50+. And that mooring is heavy, the chain is heavy, and the pendants are heavy. At anchor? Not a chance of good sleep in a gale.
In 25 knots with a good bottom? Like a baby. Except getting up to check position and wind.

[a64pilot]

Ok, there is resting fitfully, and there is being out in the storm trying to raise your anchor and dodging the other boats in the anchorage so you can go try to re anchor a little ways away.
I don’t know about you, but I don’t want to be the one who’s anchor doesn’t hold and I damage someone else’s boat.
However I agree, I’m not comfortable at 3 or 4 to 1, although it will likely hold OK.

[daletournier]

You go out in a dinghy in 40-50knots?

Originally Posted by s/v Jedi

All hands on deck to fend off the draggers, then off with the dinghy saving them, then finally hot coffee and sleep. By that time we go to sleep even if it’s 35kts wind

[Dockhead]

Originally Posted by wingssail

No, size your anchor properly, and that does not mean whatever humungous anchor that will fit, then one size bigger. There are more things to consider on a sailboat than anchoring weight. Many people, and I as one of them, don't want more weight on the bow than is needed. Use any one of many charts for sizing your anchor. Then go up one size if you want to. . . .

You and Jedi are both right. Of course, you're right, that it's not true, and is not intended seriously even, that there is no such thing as a too big anchor. Naturally there are downsides to handling giant anchors.


HOWEVER, Jedi is also right, and what he says is kind of a watchword amongst real anchoring experts. Couple reasons:


1. Larger anchors work better disproportionate to the increase in size. Some effect of soil mechanics I guess. In fact some people say that there is a threshhold at about 100 pounds where anchors start to work quite differently and much better. I have experienced this so I believe it, although I haven't seen any actual scientific research.



2. You can't size your anchor based on best-case seabed conditions. The difference in holding power between a weak bottom and a good one could be 10x. So while a much oversized anchor may be overkill in good bottoms, it may well not be overkill in a poor on, and make the difference between holding or not.


3. You don't always have the choice to use a lot of scope, and there are many cases where it is desirable to use short scope even if you are not forced to (crowded anchorage, foul bottom, no swinging room, etc.). A much bigger than specified anchor will work much better on short scope. Dashew has written that he anchors 90% of the time on 2:1 scope. He can do that because he has a 240 pound or whatever anchor.


Now I don't have a 240 pound anchor nor do I anchor on 2:1 scope, but if your anchor is inadequate to hold you at fairly short scope then in my book it's inadequate period.


All these are really, really good reasons to have a bigger anchor.


My Spade is two sizes bigger than the chart recommends, and I for sure wouldn't want anything smaller. It's 100 pounds so just into the "100 pound magic" range. I did have a 121 pound Rocna before but with the roll bar it was hard to handle and I went down a size when I replaced it with the Spade.


Note that weight on the bow is not, for most people, any kind of consideration. Why? Because it's small potatoes compared to the weight of your chain. I have 750 pounds of chain in my anchor locker; plus or minus 50 pounds in the anchor is meaningless.

[wolfgal]

Originally Posted by s/v Jedi

That’s why we went down to 3/8” but also moved the chain locker 14’ further aft from the bow.
Here’s a picture showing the setup. There’s Treadmaster protecting the deck from the chain.

Ah ha! this is of interest!!!

i've seen folks carry long and heavy chain in the bilge in the main cabin and send it up through a hatch (a bit of hoisting for the both of them) and, since then, have been wondering WHEN i'd see someone make this modification. it makes so much sense to me.


if you have the time, id like to know more...



wolfgal

[jmh2002]

Purpose designed boats often do this, bringing the chain a long way aft, preferably to around the mast if possible and then into a tall vertical locker.

This works better than the bilge itself because the chain self stows better in a tall narrow locker rather than a short wide one.

[wolfgal]

Originally Posted by jmh2002

Purpose designed boats often do this, bringing the chain a long way aft, preferably to around the mast if possible and then into a tall vertical locker.

This works better than the bilge itself because the chain self stows better in a tall narrow locker rather than a short wide one.

thanks!

and yes, it makes sense to opt for a long narrow locker for storage.

[Auspicious]

Originally Posted by Ecos

I can think of some that if you don't have some sort of a plow, you will drag in 25+. It really doesn't matter how big your new gen anchor with a roll bar is.

You're going to have to provide footnotes here. I have yet to encounter or hear of scenario when a new-gen scoop anchor does not set better and hold better than a plow.

Originally Posted by dfelsent

In 25 knots with a good bottom? Like a baby. Except getting up to check position and wind.

I don't get up to check position and wind. I get up to pee. I check lots of things in the process.

[Exile]

Originally Posted by Auspicious

I don't get up to check position and wind. I get up to pee. I check lots of things in the process.

More reliable than an anchor alarm!

[Dockhead]

Originally Posted by Marekaofholland

I don't want to burn my fingers on the topic "what's best". Been sailing since my 20-ies (now 70) and had all kind of anchors. With that experience in mind we now have 100m of 12mm chain, a 35 kg Ultra. If needed 100m of 22mm rope on our 21 tons 49 OysterPH. We are behind anchor 95% of the time in all kinds of weather. how you lay your anchor depends on wind, waves, anchorage, bottom etc. I want to sleep at night so I am conservative....that's why I like oversized anchor, heavy chain and length....

I would not call 35kg for a 19 tonne boat particularly oversized. I sure wouldn't want anything smaller. We use a 45kg Spade on a 20 tonne boat, and previously had a 55kg Rocna. I would not have downsized from the Rocna except that it was truly hard to handle. I would probably want something more like 45kg on your boat, if I were you. I know the Oyster 49PH somewhat (looked at buying one 10 years ago) and remember the very good, stoutly built bow roller and stem fittings. I believe you have the same windlass as I do (Lewmar Ocean 3). I bet you could easily handle a 45kg Ultra or Spade or whatever.

[a64pilot]

The interesting thing to me is we all rate anchors according to their weight, when it would seem that surface area is at least as important.
Yes weight does help it set particularly in weed, but it can’t be the end all of everything or aluminum anchors wouldn’t work, and of course they do.

[noelex 77]

Originally Posted by wolfgal

if you have the time, id like to know more...

It is unfortunately not a common idea.

Most of the groundtackle weight is in the chain not the anchor. People see the anchor on the bow if you tie up in a marina, but the real weight is hidden below in the chain locker. Even a slight change to chain diameter or even chain length will add or reduce the weight far more than upsizing the anchor even several sizes.

By locating the chain further back the boat can carry much more and thicker chain as well as a larger anchor and still have less bow weight than an otherwise identical boat with the more common arrangement where all the chain is stored in the bow.

There are two slightly different systems:
1. The chain locker is located well back from the bow, but the chain is still stored just above the waterline. This is the system we have. The large storage area at the bow is kept unfinished in raw aluminium further saving bow weight. The area is large enough to climb into and stand up in. This area is used for storage of wetter items such fenders, lines, sails etc. It also houses the bow thruster and transducers. There is a watertight bulkhead separating this from the rest of of the boat, so if bow thruster or transducers ever leak there is no danger of sinking the boat.
2. The chain locker is located well back from the bow (often further back than option 1) and the chain is fed down below the waterline. This system has been used by some centreboard yachts (Boreal and Garcia). These yachts have an unweighted pivoting centreboard so it is vital that all heavy items are stored as low as possible to maintain an acceptable stability curve. The drawback is water and mud etc in the chain locker has to be pumped out. It also important the design is air tight relative to the accomodation otherwise smell from the chain can permeate the living space.

[s/v Jedi]

Originally Posted by Breaking Waves

J,

I also like the Bruce. Have also used it alot at 3:1 scope. Did some anchor testing and it did better at short scope than the 'usual next-gen suspects'

I dont know where you got your copied text - but just be aware that the commercial-sized Bruces are often a somewhat different shape than the recreational size ones. I would be careful about assuming comments/tests on the one carry to the other.

Here is a pic I just copied off the Bruce 'products' page - Attachment 201672

Yes, those are the anchors used to secure oil platforms etc. These are easily 30’ long (!!!) and thus can’t be cast from one piece although I did see a couple real big ones so it’s probably just too expensive to do so.
The info I posted is specifically for the original Bruce anchors for yachts as were produced in Belgium

[s/v Jedi]

Originally Posted by daletournier

You go out in a dinghy in 40-50knots?

Yes. Well, it may not have been all of 50kts but 40-45kts on a regular basis. Over the years we have helped secure hundreds of yachts, organized hospital transports for sailors as well as local people, functioned as escort boat for flotillas of hurricane damaged boats moving to safer places etc. It’s what you do when your boat is named Jedi ;-)

[Dockhead]

Originally Posted by noelex 77

It is unfortunately not a common idea.

Most of the groundtackle weight is in the chain not the anchor. People see the anchor on the bow if you tie up in a marina, but the real weight is hidden below in the chain locker. Even a slight change to chain diameter or even chain length will add or reduce the weight far more than upsizing the anchor even several sizes.

By locating the chain further back the boat can carry much more and thicker chain as well as a larger anchor and still have less bow weight than an otherwise identical boat with the more common arrangement where all the chain is stored in the bow.

There are two slightly different systems:
1. The chain locker is located well back from the bow, but the chain is still stored just above the waterline. This is the system we have. The large storage area at the bow is kept unfinished in raw aluminium further saving bow weight. The area is large enough to climb into and stand up in. This area is used for storage of wetter items such fenders, lines, sails etc. It also houses the bow thruster and transducers. There is a watertight bulkhead separating this from the rest of of the boat, so if bow thruster or transducers ever leak there is no danger of sinking the boat.
2. The chain locker is located well back from the bow (often further back than option 1) and the chain is fed down below the waterline. This system has been used by some centreboard yachts (Boreal and Garcia). These yachts have an unweighted pivoting centreboard so it is vital that all heavy items are stored as low as possible to maintain an acceptable stability curve. The drawback is water and mud etc in the chain locker has to be pumped out. It also important the design is air tight relative to the accomodation otherwise smell from the chain can permeate the living space.

In my opinion both of these approaches are good. Slightly above vs slightly below the waterline is not really a big deal for stability, I think, if you put numbers to it. If you could get the chain way below the waterline that might be different. In that case, more chain is actually useful as ballast, so you could carry a bunch more chain without issue. I would like to have 150m of chain on board, to be honest, for some of the places I've anchored.



I don't know why pumping out the anchor locker should be such a big deal. I'd just put a grille a few cm above the floor to keep the chain off the floor, with a sump drained by a diaphragm pump. Put in a powerful deck wash to break up the mud. Making such a chain locker air tight is trivial (watertight = air tight). I think the real problem with this approach, and the reason you don't see it much, is simply the headaches it gives designers in laying out accommodation.