Manson Boss Anchor Trouble

[Graham andClare]

Some very good input from everyone, thank you. Olaf Hart raises a good point I hadn't previously thought of. I can't actually make it drag in normal circumstances i.e. reversing on it even in relatively poor holding. Once it is set it's set. However, I am beginning to think that it may occasionally fail to reset immediately after swinging in the tide. On two occasions we were in rivers where we swung 180º in the tide. The two other occasions being in open bays (Airlie beach and Horseshoe bay, Magnetic island) where the tidal influence is minimal. None of these occasions occurred in very strong winds. The boss is physically very large, having a lot of surface area. It would not be possible to fit a larger one (35#) on our bow roller. I'm beginning to think that a combination of our relatively light weight and the large surface of the fluke maybe the culprit here and failing to reset immediately after the turn of the tide. On one occasion we were not onboard. Upon returning we discovered we had dragged about 40 metres before resetting. Another occasion we were asleep at night then wake up and discover we had dragged about 70 metres but we had reset again. The other two times we were aboard and awake and realised we were moving and physically redeployed the anchor ourselves. I intend to dive on it this afternoon and have a look as we have been anchored here (Glouster island) for a couple of days now. I have now emailed Manson again and await their reply. Thanks again.

Sent from my GT-N8000 using Cruisers Sailing Forum mobile app

[cwyckham]

At least some of your incidents were while you were using the full slot. Which ones? For the two in the open bays, were there wind shifts involved?

[Kenomac]

One more possibility which would also be related to weight vs surface area, but is usually more common with the roll bar anchors, is the anchor being filled with mud, then pulling out backwards with the tidal change. Then, since it pulls out with a big mud clot, it's unable to dig in again. Much like an anchor being unable to reset when clogged with weed. A heavier anchor (proportioned to surface area) might turn easier? But if your anchor pulls up choaked with clay/hard mud, I'm not sure any anchor can reset 100% of the time except for maybe an old style fishermans anchor.

[DumnMad]

Mate, looks like a problem that won't go away until you replace that anchor with.................

[downunder]

At Airlie Beach there is plenty of junk on the bottom. Could you have caugth up with something preventing proper setting?

Just a thought.

[JPA Cate]

OOOOh yeah,

Junk on the bottom can be a major problem. That said, too many tidal cycles and swinging with the tidal stream can foul the chain on the shank, and then, you drag. What the magic number is, I really don't know. We usually recommend to friends who want to anchor up the Brisbane River, for instance, to lift and re-anchor every two days. That said, we've never dragged, off the Botanical Gardens. Nice place to be for Australia Day, too.

[Graham andClare]

Cwyckham, I felt initially that was the problem. The chain sliding down the shank. I checked the locking nut and discovered it was only finger tight. That was after the first two events. Both were in the rivers, Burnett river Bundaberg and Graham creek Gladstone. I still have difficulty thinking that it was sliding down the shank however to eliminate this possibility I tightened the retaining screw with an Allen key to be sure. There was no significant wind shifts that I recall, the breeze blowing predominantly from the sou-east. Kenomac, a good point. I have noticed that whenever we anchor in thick mud or heavy sand/mud it often comes up caked and is difficult to remove. On occasion simply dragging it in the water as we motor out is insufficient to remove it and I have to physically remove it by hand. Downunder, we did pull up some junk from the bottom from Airlie (anchored in front of the sailing club) however on the occasion that we dragged in Airlie, about 7.30am while I was having my morning coffee, the anchor came up clean. This is not to say that it did not become entangled below and cause it to not reset. Doesn't really explain the other events though. If this is the cause that is a lot of coincidence me thinks. Recieved a response from Manson saying that there is not enough information to explain why but to check the locking nut. I'll email them more info and a link to this thread. I'm not here to bag Manson or their product but purely to determine whether I have made an incorrect selection or something I'm doing wrong.

Sent from my GT-N8000 using Cruisers Sailing Forum mobile app

[noelex 77]

There have been a few reports of the bolt that used to block of the slot on the Manson Boss slipping. I would recommend blocking off the slot for overnight anchoring if there is any chance the force will change in direction significantly.

Manson seem to show two different designs of the slot. It is not clear if one design is newer than the other, or perhaps they use a different design on bigger and smaller models.

However, with both options it would appear using an oversized bolt, or shackle (not the standard Manson bolt ) would eliminate any chance of slipping. It would simply be too big to slide forward.

With a 180 degree wind shift there is a lot of force from the chain trying to pull the attachment point forwards I cannot imagine that a simple friction fit would be enough to hold in all circumstances.

[Draikhyan]

Originally Posted by LakeSuperior

I've had great service with a Rocna!!!!!

Same here. Excellent anchor.

[DumnMad]

[/QUOTE]
Wrong picture

When I look at that picture I see a sledge and toe-bar.

Maybe if you attach 10m of heavier chain to the anchor the Cat will keep the shank down so it can dig in more easily.

[cwyckham]

Originally Posted by noelex 77

There have been a few reports of the bolt that used to block of the slot on the Manson Boss slipping. I would recommend blocking off the slot for overnight anchoring if there is any chance the force will change in direction significantly.

Manson seem to show two different designs of the slot. It is not clear if one design is newer than the other, or perhaps they use a different design on bigger and smaller models.

However, with both options it would appear using an oversized bolt, or shackle (not the standard Manson bolt ) would eliminate any chance of slipping. It would simply be too big to slide forward.

With a 180 degree wind shift there is a lot of force from the chain trying to pull the attachment point forwards I cannot imagine that a simple friction fit would be enough to hold in all circumstances.

There is a notch that the locking nut fits into (the sketch you show). It isn't a friction fit.

The OP seems to be saying that he found the nut to be a bit loose, but it was still in place, so the shackle couldn't possibly have been sliding up the shank.

Honestly, I'm completely baffled. If you take any anchor at all, no matter if it is undersized or of poor design and you set it well, proving the set with half to full reverse. Then you sit on it for a few days. Then it suddenly releases even though there was no wind increase and no change of direction (the two cases in the open bays)?

That makes no sense to me at all. Not in sand or mud. Only in rock could I see that happen. Then it drags for 40 meters or so and re-sets itself. What the heck is going on here? I just can't picture what is happening on the bottom to have this happen to any anchor.

[zboss]

The reason I asked about tidal issues is that here in the Mantazas river in St. Augustine anchors that have been set really well for months also just suddenly decide to break free; the area's primary characteristics are swift currents and regular 180 tidal shifts.

This area is mud/sand.

[cwyckham]

Originally Posted by zboss

The reason I asked about tidal issues is that here in the Mantazas river in St. Augustine anchors that have been set really well for months also just suddenly decide to break free; the area's primary characteristics are swift currents and regular 180 tidal shifts.

This area is mud/sand.

Interesting. That might explain the two drags in reversing current. I don't understand the two in the large open bays yet, though.

[Graham andClare]

Yes, I can understand the two in the rivers also. After reading the posts here and talking with other cruisers the most likely explanation I think is that the large concave flukes are filled with mud. When we swing, the anchor is unable to reset immediately until the mud/sand build up has been removed. I understand there is no such thing as the perfect anchor and to some extent they all are a compromise, all having their particular strengths and weaknesses. I have emailed Manson again and alerted them to this thread. I hoping they may be able to shed some more light on the situation. Thanks again for everyones input.

[DumnMad]

Originally Posted by Graham andClare

Yes, I can understand the two in the rivers also. After reading the posts here and talking with other cruisers the most likely explanation I think is that the large concave flukes are filled with mud. When we swing, the anchor is unable to reset immediately until the mud/sand build up has been removed. I understand there is no such thing as the perfect anchor and to some extent they all are a compromise, all having their particular strengths and weaknesses. I have emailed Manson again and alerted them to this thread. I hoping they may be able to shed some more light on the situation. Thanks again for everyones input.

I think that in the particular ground conditions the flukes are acting as a sledge and the shaft angle is too parallel to pull the point into the seabed.

Its an odd design IMHO