Mantus Anchor Swivel Break

[EmeraldCoastSailor]

Gotta love posts related in anyway to anchoring. I stopped using swivels a few years ago because my perception of minimal benefit vs fear of side loading; my anchor comes up pretty straight. I see the logic of a few chain links between anchor and swivel to eliminate side loading but question the addition of another point of failure, especially considering the comments about swivels being stronger than shackles. Always something to think about.

[pdenton]

Very bad form inasmuch as the title leaves the impression that a Mantus swivel has broken. Mantus products are top of the heap. None better. Surperb engineering. Be a gentleman and issue an apology.
Ann, its this kind of thing which perpetuates my bad mood.
pdenton

[pdenton]

Well said.
pdenton

[zboss]

Originally Posted by pdenton

Be a gentleman and issue an apology.

umm. no.

[blueazimuth]

The Mantis swivel does not have a "break" reputation (but at least one has broken) and it looks beautifully built, but I don't feel good about the design, so I won't use one. A traditional galvanised shackle, properly moused down is, IMHO, the only way to go. Sometimes a traditional shackle may not easily go through the bow rollers, where the Mantis may, but that's no reason to use it.
As somebody else said "it looks wrong - it has too long a leverage" and I agree.
A short piece of chain between it and anchor may work better but .... it's still a Mantis swivelling shackle.
I just sleep better on traditional equipment

[wsmurdoch]

I used a ACCO galvanized swivel for a couple of years with a bit of chain between the swivel and the anchor. I still have it, but I don't use it. It did not break. Its real fault was that it did not swivel and let twists out of the chain.

Under a load, it just locked up and did not twist. There was no way. The bearing surfaces were rough galvanizing. Any twist in the chain made the chain jump the wildcat as it was brought in moving the twist into the chain locker. When deployed the next time much of the twist stayed in the locker eventually moving to the nylon rope just past the chain-to-rope splice. That bulked up the rope and kept it from feeding out of the chain locker.

I've looked at the fancy stainless steel swivels. They are expensive, and I don't think stainless/stainless is a particularly low friction bearing pair. I've not seen a stanless/bronze swivel or a swivel with a proper ball bearing. (The fishing guys have them for their heavy tackle.)

I'd like to see a testing of swivels to see which ones actually swivel under load. Maybe put each under a 250 lb load and measure the torque required to make the thing turn. It should not be too hard to do.

Many worry about swivels breaking. For me, swivel failure is a failure to swivel.

[Fuss]

Originally Posted by Dockhead

I just don't know about that. According to your website, the biggest Powerball which would fit my setup with 12mm chain, the 10/13mm model, has SWL of 1600 kg and BL of 6400 kg, far less than G40 chain (about 2000 and 8000), much less high test G70. And far less than the Wichard HR 12mm shackle, at 3600kg SWL and 10 000 kg BL.

But in any case, the straight line strength is not the issue -- it's SIDE LOADS which have broken Kongs and which are of concern with swivels. You have quite a lever arm there, which will magnify the loads in a side loading situation, the PowerBall much more than other swivels.

Kong publishes ratings for their swivels in side loading conditions -- typically 1/3 of the straight pull rating. The 12mm model (the one I used to have and use with my old Rocna) is rated at 3000 kg SWL and 9500 BL in a straight pull, and 3000 kg BL in a side pull.


On the basis of the data I was able to google up just now, it's really hard for me to see a case for using a swivel for the sake of strength. If you need the swiveling, of course, then that's a different matter.

So far, there has not been 1 reply with a real world example. Real world example coming later.....

I too am worried about good swivels breaking and also chain breaking.
I have a wasi swivel as the genuine bugel anchor cannot be used without one as its part of the design, the hole in the shank is round, not oblong. This stops the swivel jamming on the shank in an up or down position. If you have an oblong hole in your shank then it is not designed to have a direct swivel connection. (However, to a good quality swivel, this probably does not matter much)

If there is examples of Kongs breaking then I would not use one. is there a real world example as I never saw one???
Is there really an example of a broken Kong, can we see it???

There is not a single instance of a Wasi swivel breaking that I know of...is there one???

Ok, now on to the only real world example in this thread so far......

My shank is 23mm wide with a directly connected Wasi Powerball. In a bad storm my anchor shank bent maybe 45 degrees but no damage occurred with my swivel. Thats why I say that good quality swivels will not bend before the shank in a sideways pull.

If you look around the yards they are littered with poor quality swivels with splayed forks....no-wonder everyone goes on about swivels.

[Fuss]

Originally Posted by grantmc

There have been quite a number of cases where the swivel fails. It's caused by fitting the swivel directly to the anchor (wrong) and when side load is applied voila, broken swivel.

There should always be a few (3-4) links of chain BETWEEN the anchor and swivel, to ensure it can't get side loading when the boat swings around the anchor.

Sorry, but these types of swivels are not strong enough, you have to use something like a Kong, Mantus or Wasi.
See my post above.

[Dockhead]

Originally Posted by Fuss

. . . If there is examples of Kongs breaking then I would not use one. is there a real world example as I never saw one???
Is there really an example of a broken Kong, can we see it???

Yes, there are a few cases of Kong swivel failures.

This guy did destructive testing of some different swivels and shackles: https://coxengineering.sharepoint.co...onnectors.aspx

If you don't know him, his website has a wealth of great stuff on it.

Despite the reports of failures (I think the design has been changed since then), my judgement is still that the Kong is the best. I am intrigued by the Mantus, which might be superior to the Kong in several ways, but for the cover being secured by wire, which makes me nervous.

Originally Posted by Fuss

My shank is 23mm wide with a directly connected Wasi Powerball. In a bad storm my anchor shank bent maybe 45 degrees but no damage occurred with my swivel. Thats why I say that good quality swivels will not bend before the shank in a sideways pull.. . .

I would not want the swivel, to bend my anchor shank. That's also a failure.

As others have stated, I don't like the long lever arm of the WASI. It will weaken the swivel itself, and besides that, will magnify the force of a side pull and make it more likely that the anchor shank will be bent. It's like putting a crow bar on the anchor shaft.

I also just don't see the point to the whole construction of the WASI. What benefit does the small amount of flexing bring? It's only 20 or 30 degrees. To get that small amount of flexing, the whole construction is probably double the length, which is definitely bad, weakening the swivel itself and also tending to bend the shank of the anchor.


If I ever need a swivel again, I think I will put a couple of links of chain between it and the anchor as is widely recommended. The only drawback is adding one shackle to the system. On the plus side, no side pull at all on the swivel, no exaggerated side pull on the shank of the anchor, and it should go over the bow roller more smoothly.


One very cool thing about the Mantus swivel is that the body of the swivel is not attached to the anchor shaft, so there is no lever arm at all. In this it is superior also to the Kong.

I just wish the cover (which retains the pin) were attached in a more secure manner. If it just screwed down onto the body of the swivel, so that the safety wire merely preventing it from unscrewing, it would probably be perfect.

[Kenomac]

Like this. No protruding bolt, no wire required, massively overbuilt, no extra piece of chain required and the anchor comes up correctly every time.

[a64pilot]

Originally Posted by Dockhead

I just wish the cover (which retains the pin) were attached in a more secure manner. If it just screwed down onto the body of the swivel, so that the safety wire merely preventing it from unscrewing, it would probably be perfect.

That is the sole function of the wire, it is there solely to prevent rotation of the barrel.
I took two wraps on each side of the barrel, to allow the barrel to loosen you would first have to bust both pieces of safety wire, if you were really paranoid, you could make it four individual pieces so that all four would have to bust, the groove is deep enough to allow that.
You could drill and tap a hole through the barrel into the body of the thing as well and install a locking screw, but I do not think its necessary.

[Recy]

https://coxengineering.sharepoint.co...onnectors.aspx

You are right this site is a goldmine.

[wsmurdoch]

Originally Posted by CarlF

I've had several West Marine shackles break for no good reason and now only buy US made Crosby shackles to have some confidence. A 7/16" Crosby 209 has a 1 ton rating with a 1:6 safety ratio (12,000lbs). The harder to find 209A "High Test" is 2.6 ton (31,000lb) 7/16" is the "up one size" from the chain size that many recommend for 3/8" chain.

The Crosby high test shackles are not too hard to find. Defender keeps Crosby G-209A shackles which are the fully galvanized kind, pin and all:
Crosby G-209A Series Forged Alloy Anchor Shackle
It is what I use.

They also keep Crosby galvanized swivels, but the description says "G-402 Swivels are positioning devices and are not intended to rotate under load". Why else would I want them?

[SVNeko]

Originally Posted by Dockhead

This guy did destructive testing of some different swivels and shackles: https://coxengineering.sharepoint.co...onnectors.aspx

That data show that the quality swivels have about the same strength as the chain, so not the weak link. We use the Ultra swivel 2x oversized, so it is much stronger than the chain. We were anchored (and horrifyingly) on the boat for an hour of 55kn sustained winds at anchor and there was no noticeable effect on chain or swivel.

[Smokeys Kitchen]

I pulled this up two days ago and then worked on it while we were in Oak Bay. One of the wires had busted where it was twisted together. I removed both wires, re-wrapped it in teflon tape, put 2 new wires on it as instructed then put on one extra wire going over the top and a zip tie going over the top. I used the wire that I had, .032, and we had anchored in some rocky areas.

I still like the swivel, but will monitor the wire fastenings very closely. The enclosed pictures are the break and 2 of the replacement wire/zip tie arrangement.