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Old 02-06-2007, 22:04   #1
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To swivel or not to swivel

OK, so I have made my plan, purchased my ground tackle, and picked my spot. I have a 22' wide slip, a 14.5' beam and good wind/wave protection at my dock. So, for tropical storms and category one hurricanes(typhoons or whatever your hemisphere) I am leaving her at the dock. For cat two and three I am going to anchor her in a hole somewhere. For cat 4 and 5 I am going to strip her down, anchor her to the bottom, and sink her at the dock. It is the anchoring I have the question about but I am open to suggestion on my overall plan. I have (2) 50' lengths of .5' chain, (1)100' length of .5' chain, (3) 50' sections of .75' nylon twist, (2) 50' spade anchors, and (1) 60' plow anchor. The anchoring plan is to have three anchors with 100' rodes(50' of chain and 50' of line). The central (main) anchor has a 100' chain rode that will be secured around the mast but will have a 50' section of .75' nylon twist spliced in as a snubber. So the all chain rode is only there as back-up if the line snubber fails. With this picture in mind I have two questions. First, do I attach the three rodes to a swivel. I have read two schools of thought. One side thinks the swivel is a weak link, most likely to fail, and that all rodes should be secured directly to the boat. The other side feels that an anchoring system like this absolutely needs a swivel so that the rodes don't tangle when the wind shifts or the boat dances at anchor. I am looking for more opinions. Anyone? Second. What angle should the anchors be set from each other? Thanks for your input.
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Old 02-06-2007, 23:13   #2
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Firstly, why does everyone think swivels are a weak link? The fact is a good swivel is many many times stronger than a bog standard shackle. I think some people need to stop listening to the un-informed people. Yes there is yucky swivels out there but for everyone of those there is 1,000,000 yucky shackles. Grizzle vented.

2, Having owned a mooring servicing company for many years I can assure you swivel failure is very rear. Rope failure is the most common cause of a mooring failing, not by a little, by a lot. CHAFE PROTECTION and overkill it.

3, 3 anchors out at - worse/most wind/waves coming from 12 o'clock - 2 and 10 oclock with the 3rd at 6 oclock. chains from them to a centre spot where the swivel is. It's a storm mooring so don't underize the swivel, 1" plus in plain old black steel. Chains and ropes to the boat.

4, Set-up well and hope like hell keeping in mind you can take every precaution against **** happening but **** will still happen.

5, Did you remember the chafe protection?

Good luck.
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Old 02-06-2007, 23:44   #3
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To add, the length of Rode is a mute question without knowing the depth of water. Normal anchoring calls for a 5:1 Rode/depth and storm forces require significantly more than that again, like 10:1 and even greater. So for instance, 100ft of rode is only good for ruffly 10ft of water.
Here in NZ, we don't get Hurricanes/cyclones where you have a wind direction/eye/oppsoite wind direction. So I can't speak from any experiance like that. But the biggest concern of using multiple anchor sets is the tangle you can end up with when the boat swings to 180degree wind shift. IMO, I would concider tandem anchoring. That is, chain two or three anchors in series. Use your short chains between sets. Once the storm swings 180 deg, then the entire set simply turns and maintains a straight line. This technique is simply stunning in terms of anchoring power as the following anchors rodes are flat on the bottom and so the anchors just dig.
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Old 03-06-2007, 01:58   #4
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Yes, I have considered chafing gear but I have not purchased anything yet. What do you recommend? Hose, cloth, leather, etc. How many layers?

Yes, I forgot to mention the depth at anchor. It is about 8 ft. That is how I came up with the length of the rodes. 10:1 with a little in the bank. GMAC wha tdo you think of Wheels suggestion of putting the anchors in series?

As always, thank you all for your input.
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Old 03-06-2007, 02:00   #5
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Quote:
Originally Posted by salty_dog_68
... For cat 4 and 5 I am going to strip her down, anchor her to the bottom, and sink her at the dock...
Wow, a truly draconian measure ...
I understand that you’re not likely to suffer much structural damage, sunken, but you’re guaranteed to require a significant re-fit when you raise it.
Are you certain your dock (or hidey hole) is untenable in a cat 4?
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Old 03-06-2007, 02:18   #6
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I am not certain of anything. That is one reason that I am on this board looking for advice. My slip does have good wind and wave protection so my biggest concern is storm surge. One of my sailing buddies, a seasoned salt :-) and vetran of a few carib hurricanes, thinks that the boat would be fine at the dock for a cat 2 and that I should only sink it if we were to get hit head on by a cat 5. For me, I guess, it would be a game time decision based on the projected path and the predicted storm surge. This boat rode out Wilma(cat 2) at a slip in Ft. Lauderdale w/o batting an eyelash. Wilma, b/c of her path, was only a wind event in S. Florida. There was no storm surge. So, I have a plan b/c I need one but it is dynamic based on each individual storm.
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Old 03-06-2007, 02:20   #7
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blah..blah...blah. Sorry, I do get to rambling in the wee hours of the morning. I guess what I am trying to say is that I would only sink the boat if it appeared certain that the boat would be a total loss anyway.
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Old 03-06-2007, 09:27   #8
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Quote:
Originally Posted by salty_dog_68
Yes, I forgot to mention the depth at anchor. It is about 8 ft. That is how I came up with the length of the rodes. 10:1 with a little in the bank. GMAC wha tdo you think of Wheels suggestion of putting the anchors in series?
I don't live in hurricane territory, but I have read that the surge and low-pressure effects can raise the sea level quite a few feet. You also need to allow for your freeboard, and the length needed for attaching the rode to the boat. After all this, you may be down to 5:1 scope.

As I said, I've only read about hurricane anchoring, but the surge may be worth considering.

For chafe-protection, I like sections of old firehose. The double-jacket stuff is *really* rugged. You need to lash it (or any chafe-gear) to the rode being protected, or it invariably ends up sliding up or down the rode. Do read up on the issues of line stretch and internal heating/melting.
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Old 03-06-2007, 09:54   #9
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On Catamarans has Anyone consider filling tarps with sea water and tie them off on the bow and stearn using a swivel to keep the wind from flipping them? Dumb or Not?

Keith
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Old 03-06-2007, 10:24   #10
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A swivel is a really bad idea under normal anchoring condition and an extremely bad idea under storm conditions. Those that will tell you there is nothing to worry about with them either sell them or have never experienced the devastation as a result of their failure. Yes there are many out there but most of them have never been tested under serious strain in real world conditions.
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Old 05-06-2007, 20:18   #11
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Old 05-06-2007, 20:20   #12
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Old 05-06-2007, 20:58   #13
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Quote:
Originally Posted by Chuck Baier
A swivel is a really bad idea under normal anchoring condition and an extremely bad idea under storm conditions. Those that will tell you there is nothing to worry about with them either sell them or have never experienced the devastation as a result of their failure. Yes there are many out there but most of them have never been tested under serious strain in real world conditions.
You're not serious are you? Sorry Chuck but it is quite obvious you have limited experiance with them, at best.

AGAIN - A good well made swivel is a good thing in some situations, like moorings. There are plenty out there that have experianced many many real life full on strain situations. I know of over 10,000 and that's just the ones I've used myself (used as in actualy put on moorings with my own hands) over the last 10 years. NOT ONE HAS FAILED as far as I know. I've also sold 1000's for both anchoring and mooring (differant swivels for each by the way) and have only had issues with 1. To me that says "A good swivel is perfectly fine in real life". Now ask how many shackles I've seen fail in both morings and anchor systems and the number is large and the reason my moorings have 32mm shackles on 16/20mm chains. Ask how many moorings have failed due to not having a swivel, well not that many I've seen actually, but still 20 odd times more than those with them. BUT like anything, buy cheap and nasty and the grief is probably not far behind.

Use a BlueLine swivel out of Norway, I think, nicely made batch tested and if set-up right are bloody fantastic even in a real life storm.

As you can see above my comments are purely based on what I have actually done or seen done, not on hearsay or sales pitches. Not to mention there is now way in hell I'll be selling anyone anything, I'm too far away.

Gezz Chuck, you pushed a button there :-)

Chafe protection - leather, reinforced hose (fire one is good), Dyneema/Spectra sleeving, car tyres sliced up, combo of all. Anything that wears well really and lots of it.

Anchors in Tandem? 2 minds on that one even when used for normal anchoring. I definatly wouldn't do it if the wind is doing 180's just in case they don't reset. I would dive and dig them deep which could be tricky. Personally I like the 3 pointer more.

What Wheels is saying is that the tandem way stops your rodes twisting up, which it can. I'm saying you run chain from each anchor to the swivel and then one (or more if you like) from the swivel up to the boat. That way the boat is free to do 180's without twisting anything up. I think Wheels was thinking I mean run all rodes up to the boat.

From your posts above all I'd be tempted to do is find some bigger chain. Used stud link off ships is bloody good. More weight down there the better.

What's the boat?

Alain - time for more photos I think and an explaination of what each is. For example the broken cheap nasty asian made one (shown) that was actually used on a permanent mooring. Reason for failure? The guy who did the mooring was an idiot, simple as that. NEVER use SS in a permanent mooring. Mind you those particular swivels are crap anyway. The other swivel has a small bend in it, so what?? Nothing on your boat has been bent a bit or changed shape in a little way without failing? I'll put money or if you want to get real serious, cold beers, that your anchors have changed from when they left the factory but you're still happily using them :-) My alloy anchor (a design you may know :-) ) has a slight bend in part of it, been there for ages but I still happily use it. It works perfectly fine and is still safe.
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Old 06-06-2007, 00:25   #14
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My comments were in reply to the original poster. I may have had the wrong interpretation, but I assumed Saltydog was describing three seperate rodes to three seperate anchoring systems. This would be a bad idea IMO. Maybe I have not understood.
A correct method is to use three anchors set in a circle divided into 1/3rds. This is called a Bohamina moor. Chains run to the centre of the circle and at that point the rode to the boat is connected. This connection can be a swivel or a shackel. This system is not easy to deploy. And the big drawback of the technique is that you are relying on one anchor out of the three to take the load. Shoould it lift out and does not reset fast enough, the load comes on the other two anchors at the wrong angle and they can also drag till the failed anchor resets. This then means you have three anchors now lying incorrectly. If the storm now blows from the opposite direction, the anchors can be pulled together till they all set and this can end up as a tangle. It is still a good system however and I am not saying it should not be used.
Tandem anchoring for storm tactics is a very good solid way to anchor. Much more unlikely for the tandem set of anchors to pull out, as the load on the rear one is from a flat low down pull from the front anchor. Not like a chain rode that can lift as the load comes on. This tail anchor helps to maintain the front anchor in position as well. The tandem set is not too hard to deploy, nor to hard to retrieve. Unlike the Bohamian moor. I have no testing, nor seen any testing from anyone else, but I do feel the tandem pair give more holding power than the sum of the two independantly deployed.

As for shackles vs swivels....I don't think either is any better or worse, but personly, I do not like Swivels. Just personal, but I like a good meaty shackle.
Also IMO, I don't trust SST under water. But as pointed out, there are SST's and then there are SST's, plus there area shackles/swivels and then there are shackles/swivels. The only swivels I would consider using are so damn expensive, I wouldn't consider using. A shackle is far cheaper and I feel much safer using a tested and rated galv shackle of larger size than the chain is.
I also don't belienve you should swivel on an anchor. I would rather see the anchor being turned while set. The anchor I have remains set while being turned. Using a swivel will allow the boat to trunt he full 180 deg and then when the load comes on, the anchor will pull out and then have to compleatly reset.

In a severe storm, I would never rely on just rope rode. I want a solid chain connection to the boat. Actually, I use chain all chain no matter what the conditions, but....
Then a good bridle (is this what some call a snub??) from each side of the bow to the chain for shock loading. It also stops the boat from fishtailing so much.
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Old 06-06-2007, 14:54   #15
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Alain - time for more photos I think and an explanation of what each is. For example the broken cheap nasty asian made one (shown) that was actually used on a permanent mooring.

Hi, GMac,

You know that I usually agree with 99,99% of your comments and that I respect your professional experience.. but.. I do not agree with your comments about the swivels..

If a professional can select the best gear, do you think that a common sailor, like myself, can make the difference between a good swivel and a low quality “China made” one?? When new, they are all looking the same..

Try the following experience (At least in France) go to any ship chandler and ask for either a swivel or “thing” to attach two lengths of chain.. and look at the goods they will propose you, ask them the question?: “will it be strong enough??” and listen to the answer..

Unfortunately all chandlers are not good professionals as you are.

About the photos I have previously published, both have been on anchor chains, not on permanent moorings.
- The first swivel was certainly strong enough for a straight pull, but not for a side pull. It seems to have only a small bend in it, but was ready to break out.
- The second one was attached on the anchor of the French boat “Aspirine” and broke with a wind not higher that 25 / 30 knots
And when new, both have been looking like good swivels..

Hi Alan Wheeler

Tandem anchoring for storm tactics is a very good solid way to anchor.- I have no testing, nor seen any testing from anyone else, but I do feel the tandem pair give more holding power than the sum of the two independantly deployed.”

I did test Tandem anchoring, in the Med water where the water is crystal clear and warm enough to dive..

In about 62% of the cases, only one anchor was set.. it is the technique I call “Russian Roulette anchoring”.

Here is a letter from Jean Louis GOLDSCHMID (Former technical manager of the very famous French sailing school “Nautical Center of Glénans”) published in N° 114 of Glénans news letter (August 83) (“badly” translated from French)

<< The Tandem set technique it is a very good technique with Fisherman anchors and I personally made some experiment at time when the Glénans’s boats only had this type of anchors on board.

On the other hand,. I began one day to have doubts while seeing tandem set anchored boats dragging.
I thus carried out a series of measurements of traction with a motor boat. Almost all the tests gave the same results: one needed 200 rpm less to drag 2 tandem set anchors (CQR or Fluke anchors) than only one of these anchors alone. I thus checked what occurred, with small anchor on the dry maërl beach of “PEN MARYSE” in the Archipelago of Glénans, pulling by hand.

First problem with the CQR:, it doesn’t have any fixation hole to attach the second anchor (that should have been a sufficient reason for not using this technique), I thus tested the bar, the trip line hole, the elbow of the shank. On these 3 points. the effect is the same one: the articulation plays badly, the plow cannot dig in. Remain the extremity of the shank, but it is not better. Almost each time, the chain comes to obstruct the plow The whole system does hold only on the most distant anchor. If this one is smaller, it holds less than only the large anchor one. I noted too that an anchor holds very badly in the furrow of another.

With the “Fluke” anchors: this is again the same problem of devoted fixation, and it does not have there anything which can be used except sometimes the trip line rings which are usually not strong enough. However, from time to time y obtained results comparable with the holding of only one anchor.

I thus concluded from it, that I had sufficiently poisoned my life by re-installed useless scrap heap to definitively give up the tandem set technique.

If your single anchor isn't working on its own or you don't feel you can trust it in average to strong conditions, then maybe it is time to consider replacing it rather than chucking various complicated arrangements of ironmongery at the problem.

Alain
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