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Old 17-08-2019, 13:56   #1
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Mantus swivel? Design flaws? Or no swivel at all?

I've got a mantus swivel here . Looks like a pretty nice design. However I'm not liking the dependence on the wire for the collar and the backwards bolt shackle. The through bolts suposed to have a nut on the other side where the threads are. That's where you mouse it off. And the collar seems heavily dependent on the tie wire when that goes so will your anchor. Seems to me in theory it's a great swivel but with real world design flaws? The bolt shackle I'd say not so much because it has some redundancy with the tension on the threads. But the mousing wire on the collar if that fails it's over. There is a race for the wire to sit in but it's still wire. I believe that ought to be a through bolt. And the shackle a proper bolt type shackle. Any one care to elaborate on this? I think I'm better off with out the swivel at all?
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Old 17-08-2019, 14:19   #2
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Re: Mantus swivel? Design flaws? Or no swivel at all?

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I did not like the wire holding it together so I used a large cotter pin.
Very happy with it.
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Old 17-08-2019, 15:18   #3
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Re: Mantus swivel? Design flaws? Or no swivel at all?

Major improvement with that cotter pin I'd say. I've got a s1 for 5/16 grade 40 ht chain. The chains rated at safe working load of 3900 lbs the swivel is rated at 1.5t and 15000 lb break strength. So seems to be just what the doctor ordered. How accurate are these numbers I don't know.... that whole cotter pin/tie wire and backwards shackle bolt, makes me wonder about the design.
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Old 17-08-2019, 17:08   #4
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Re: Mantus swivel? Design flaws? Or no swivel at all?

We never use a swivel. That would allow the anchor to come up bass ackwards or sideways. Our anchor comes up correctly for stowage every time, thanks to a grooved roller.
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Old 17-08-2019, 17:16   #5
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Re: Mantus swivel? Design flaws? Or no swivel at all?

I've got a grooved roller also just wondering about behind anchored for extended periods and swinging w the tide and wind twisting up the chain
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Old 17-08-2019, 17:25   #6
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Re: Mantus swivel? Design flaws? Or no swivel at all?

You want a swivel when the wind or tide turn the boat round a lot. And if your boat is big (= big anchor winch and big chain). Yes.


Swivel is not required if you have no winch, if the winds are stable, if the boat is quite small.


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Old 17-08-2019, 18:20   #7
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Re: Mantus swivel? Design flaws? Or no swivel at all?

Quote:
Originally Posted by Eastward ho 24 View Post
I've got a grooved roller also just wondering about behind anchored for extended periods and swinging w the tide and wind twisting up the chain

Is 21 years an extended time? We have been at anchor in all sorts of conditions 24/7/365 except those years, every 7 or so when we haul out, and possibly a week or two either side of that.

In West Palm Beach, we had to make sure that we swung and re-swung with change of tide to not twist up, but we had 4 anchors out. In Port'd Andratx Mallorca, we used a mooring, with a big ass swivel. The rest of the time, any twist set up by tide changes was released as soon as the anchor left the bottom, and by the time it arrived at the roller it was correctly positioned, and in the odd case when not, like 90 or 180 degrees out, I used a large screwdriver to pop the chain over in the grooved roller and the anchor followed it.

A swivel allows it to come up any which way, then you have to poke it with a boat hook and bad language.


Oh, In the Kourou river in French Guyana, we had to re-anchor every week to stop the anchor digging down into the depths of the mud and become irretrievable.
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Old 17-08-2019, 19:05   #8
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Re: Mantus swivel? Design flaws? Or no swivel at all?

My Mantus. Anchor always pops around to the correct orientation when it hits the roller. As far as mousing goes - you should have two separate loops holding it in. I over tightened one of them and it broke - it would have still held the barrel even if was the only loop.
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Old 17-08-2019, 20:18   #9
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Re: Mantus swivel? Design flaws? Or no swivel at all?

I've used the mantus swivel with wire almost everyday for 2 years, haven't had any issues.
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Old 17-08-2019, 20:52   #10
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Re: Mantus swivel? Design flaws? Or no swivel at all?

Took the swivel out three years ago. Full-time at anchor (when not on passage!). Wondering why i ever had a swivel in the first place.
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Old 18-08-2019, 00:23   #11
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Re: Mantus swivel? Design flaws? Or no swivel at all?

I do not use a swivel. Most of the time a simple shackle is fine. However, on rare occasions the chain can become twisted when lying at anchor.

To put a twist in the rode, the boat does not have to swing around the anchor, it only has to spin through 360. The most common situation I have encountered this problem is in weather situations where there is two opposing wind systems. For example a southerly breeze with a local northerly sea breeze. In these situations the boat can do multiple spins in a short space of time as one or the other wind predominates.

At anchor the twists in the chain are not noticeable because they are distributed over the whole length of the rode. However, when the chain is retrieved, the gypsy will not pass the twisted chain so the twists become concentrated in the ever shortening length of chain between the gypsy and the anchor. Chain will only accept a certain number of twists per meter before it starts to hockle.

The torque can be very impressive. On one occasion I was concerned the chain links would be permanently deformed. Once the anchor has broken free the twists will spin out even without a swivel (sometimes very dramatically). But to break out a good quality modern anchor the scope has to be close to 1:1. If the twists become excessive before the rode can be shortened to this scope, the anchor cannot be broken out.

Fortunately, this is very rare problem. I have experienced this issue less than 1 in every 1000 nights at anchor. However, it can be very frustrating to solve and the torque in the chain is potentially quite dangerous.

Not a great photo, but if look carefully you can see the chain start to twist severely. There are even a couple of links lying sideways even though the rode is under a lot of tension.
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Old 18-08-2019, 01:34   #12
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Re: Mantus swivel? Design flaws? Or no swivel at all?

I have Mantus S3 on 70kg Rocna. Unless we are moving backwards, the anchor usually comes up 180 off, and If the anchor is fouled with mud, we will leave anchor just below surface to clean it with forward motion which causes it to point forward, so I need to spin it with boat hook. I take a look at safety wires after raising, so far so good after many drops. We are full time cruising, with hundreds of anchor sets. No issues so far. I think the Mantus swivel is the best available for now.

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Old 18-08-2019, 01:36   #13
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Re: Mantus swivel? Design flaws? Or no swivel at all?

Noelex, All excellent observations and concur as I've also had that concern. How much hockle before deformation would be load induced maths and I've never seen chain specs regarding twist/ load/ UBS. Interesting. All laid out with simple twists is concerning but perhaps ok. A ball with a bad angle not so good. I once had a twist and knot under a corral that caused grief and swivel would never have helped. The twist was from the chain jam and up, anchor was fine. Yanked on it so hard in swell and never had confidence till replacement.
If you have swivel to invert an anchor while nesting that's another altogether. Tight bow roller chain groove is imperative. Even more important when gear gets big as Simi says. No groove and that twist will easily be swallowed by a chain gypsy on retrieval and sent below. You don't even see it happening. Enough knots and the day you decide to unload it all those hockles are inside with no hope to dump it all.
Fun fact.. swivels, oversized chain or any bulk reduces an anchors ability to dive. Effects performance at a measurable loss.
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Old 18-08-2019, 02:42   #14
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Re: Mantus swivel? Design flaws? Or no swivel at all?

The twisting of the chain is exasperated if you are anchored in shallow water as most of the chain is retrieved before the anchor breaks loose. In deeper water of course there is more chain in the water when he anchor breaks free and can easily untwist itself
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Old 18-08-2019, 02:53   #15
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Re: Mantus swivel? Design flaws? Or no swivel at all?

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The twisting of the chain is exasperated if you are anchored in shallow water as most of the chain is retrieved before the anchor breaks loose. In deeper water of course there is more chain in the water when he anchor breaks free and can easily untwist itself
Good point. Maybe snubbers could take some of that.
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