Mantus Anchor "Resetting"

[Andrew Troup]

Originally Posted by Stu Jackson

Andrew, isn't this essentially a kellet or sentinel?

three things

1) Those words have recently acquired a veneer of unrespectability, along with and for the same reasons as the word beginning with cat and ending with enary.

2) My approach is intended to be more flexible: both in passing with less intervention over the bow roller, and in conforming to the bottom in order to provide more frictional drag. Whilst remaining relatively snag-free because of their shape.

3) Smaller instances of ballast, meaning they are easier to handle, and can (under other circumstances) be distributed along the rode,

with the added possibility of interspersing weights with floats (Z-rode, for unattended and durable self-snubbing in shallow water)

I forgot in my last post to mention a labour-saving enhancement for the 'Tail' of each shot: a cord or a sling with a toggle fitted at right angles, which can be poked through a link of the chain at the trailing end (the leading sling still being cow-hitched to the chain, for security)

[JonJo]

Andrew,

Can you clarify - your 30mm chain links - you are attaching them to the chain at or near the shank?

Jonathan

[model 10]

Originally Posted by Andrew Troup

Spoken like a Luddite.

These are trivial, pedestrian concerns.

Man's need for speed is unquenchable !

<insert ironic emoticon - I am paraphrasing
how this prognosis might have been received
when Concorde was the last word in modernity>

Au contraire sir! I am all about faster higher more efficient (louder is OK sometimes) more powerful, bigger engines, (liquid fuel rocket motors rule.) Hyper-sonic ram jets are the way to China. No, the Concord was like one of those primitive helicopters, way too prototype. And, get this, they knew the lower surface of the wing was vulnerable to FOD. They had a plan to install some sort of shield on the fuel tank but had not done so.
This is the era of Priuses, with no muffler and Beneteaus.

[Blue Crab]

Originally Posted by JonJo

Andrew,

Can you clarify - your 30mm chain links - you are attaching them to the chain at or near the shank?

Jonathan

And are they HT?

[Andrew Troup]

Originally Posted by Guy

Au contraire sir! I am all about faster higher more efficient (louder is OK sometimes) more powerful, bigger engines, (liquid fuel rocket motors rule.) Hyper-sonic ram jets are the way to China. No, the Concord was like one of those primitive helicopters, way too prototype. And, get this, they knew the lower surface of the wing was vulnerable to FOD. They had a plan to install some sort of shield on the fuel tank but had not done so.
This is the era of Priuses, with no muffler and Beneteaus.

You misunderstand the thrust of my post, but that's OK.

I think I understand yours.

And there seems little doubt that you are on the winning side, in the sense that those who share your enthusiasms shall inherit the earth

(albeit, probably, briefly)

[JonJo]

Originally Posted by Blue Crab

And are they HT?

Very droll - but it was a completely serious question, are the 30mm short lengths of chain attached at or near the shackle for the shank. (Round here they use such chain as part of the assembly for swing moorings).

Jonathan

[Andrew Troup]

Seeing the discussion is ranging so widely, I'll trespass further on the OPs goodwill (I promise to supply the beer when and if we ever share an anchorage, N77!)

To me the best thing about Concorde was that it got the French and English working together.

A family member shared a flat with someone who was working in the design office at Aérospatiale at the time, and his territory was the interface between the British and the French-built modules. The hydraulic fittings passing through the bulkhead at that station all had BSP threads at one end and metric at the other!

The French are a proud people, with some justification, and it was very hard for them to forgive the Poms for holding the bridge when they caved in under the jackboot. I remember a great headline (from "Life" magazine, perhaps?)

Entente Concordiale !

It didn't take hold immediately, though.

For instance I'll never forget David Frost announcing in the 70s that the English PM and the French President were about to jointly open the mid-channel lift (US=elevator) connecting the French cross-channel bridge to the English cross-channel tunnel (or was it vice versa?)

However I was struck, just today, to hear that the next Tour de France will start in -- wait for it -- Yorkshire ! Yay ! ! ! !

I remember hearing with disbelief about a search party, despatched to find a competitor in the Paris-Dakar rally a few years ago. The names of the places they were searching were strangely familiar to me, from a recent trip to South America !

I wondered, until I found out the real situation, if the 'navigator' had fallen victim to the good old "typo when entering GPS destination" syndrome.

[sabray]

If you anchor enough you kind of know your set well or not. I swear I can feel the bight even hear the sound of hard pan through the chain. If it's good you will know it. How you apply that to a graph or anchor test I don't know. I just know when I set it well it's good. How I know without a camera or diving is just voodoo and experience. You will know if someone has a voodoo doll of you and is wanting to fill you with pins. Just like you will know your set well.if you start thinking about pins and needles you should move a bit and try again.


Sent from my iPhone using Tapatalk

[noelex 77]

Originally Posted by Andrew Troup

I had another thought the problem of those anchors which might need a bit of encouragement to remain set, while simply shuffling about.

A key to that is avoiding (to the extent possible) uplift of the shank. That's particularly hard to avoid in shallow anchorages, where catenary due to chain weight is little help.

Overall I am fan of putting the maximum weight in the anchor and minimising the weight in rode (providing the rode is sufficiently strong and abrasion resistant) as the way to get maximum performance from the weight of anchor gear.

However, that does not mean there are no advantages to extra weight in the rode. Helping the anchor reset in the most stable buried condition is an situation where there is an advantage, in some circumstances, to heavier chain.

The earlier the photographs of the Mantus rotating, in a very stable fashion, were taken with my slightly lightweight (for the size of the boat) G7 chain. So the anchor made the rotation with less help from catenary than most cruising boats (that usually anchor with all chain) would have given the anchor. (The scope was a moderate at 4:1, then later 5:1. I let out a bit more snubber when things got gusty).

I made the transition to lightweight G7 a couple of years ago while regularly observing my Rocna anchor and noticed no practical difference in its resetting appearance before and after the transition. This suggests to me that the benefits for heavier chain, on an anchor that rotates well would probably be small, but perhaps I should have paid closer attention to looking for a subtle difference in this aspect of anchor performance.

There is quite a variation in the ability of different anchor designs to remain well buried and set during the rotation phase. For those anchors that struggle, heavier chain or a kellet may be a significant benefit in improving the rotational performance when this occurs at a moderate windspeed. If the anchor remains set and stable it is in a better position to subsequently manage stronger winds.

It is worth rembering that extra scope always works to reduce the shank angle even at high windspeeds so this is always the preferred option, but it is not always possible.

Rather than heavier chain overall (or a short length of heavy chain close to the anchor) I still think placing that same weight in the anchor itself would improve the anchor performance more, but it is conceivable for those anchors that have a weakness rotating the opposite may be true.

It also might be worth considering as storm tactic for situations where the anchor has to be set in opposite direction to a strong wind that is predicted to arrive later. It is an application where a kellet close to the anchor could be beneficial especially for an anchor that is not very stable during the rotation. A kellet can at least be stored low down close the centre of the boat minimising the weight impact compared to adding the same weight to the anchor.

It should be remembered that thicker chain close to anchor has been shown to inhibit the anchors ability to dive. A bulky kellet close to the anchor could do the same thing if not placed carefully. The effect of these competing factors are difficult to balance. I will keep watch out when diving on those anchors that rotate poorly and see if I can detect any difference in rotational performance between those boats with heavy (for their size), or light chain. It is an aspect I had not considered before.

[Factor]

Originally Posted by Coops

Your life on the last flight.

If my post was in error then it all shows then that it depends what you read and where you get your information from as to how accurate and factual any comment is on any subject. Unless you have done it yourself of course.

Coops.

Really good point, and one which many folk who pass opinions should keep in mind.

Off at a tangent and FTR I have been supersonic a few times, have no idea how much fuel it was using, I was just along for the ride. Way Cool, Way Way Way Cool.

[noelex 77]

As a side issue, I have tried setting the anchor against the prevailing wind direction on occasion (using older anchors, I have not yet tried this with the Mantus).

If you are expecting a strong wind from a different direction to what is blowing when you arrive at the anchorage, using the motor it is possible to set the anchor in the direction of the expected strong wind, rather than the direction of the prevailing wind at the time of dropping.

This can only be done when the prevailing wind is reasonably light. As soon as you cut the motor the boat will swing around towards the prevailing wind and unless the wind is very light the boat will drag some, or all, of the chain around so often you will lie in essentially in the same position as you would if the anchor was set normally.

It takes a reasonable wind strength to rotate the anchor around so the anchor will stay set in the correct direction for the strong wind, providing the prevailing wind stays light to moderate.

Be prepared for some strange looks from your neighbours if you try this tactic . Do consider if the wind is not strong enough to stretch out the chain your anchor may not be where other boats assume it is.

Basically I have given up on this tactic for a couple of reasons:

1. I have discovered my anchor rotates around in a very stable and well set manner (this was experience with the previous Rocna, some of my older anchors were not as good. The Mantus is too new to tell, but this was an excellent first performance)

2. The anchor does not set as well when set "upwind or crosswind" (when observed underwater). I think this is partially due to reduced set force (setting normally you have the engine force plus the wind force, setting against the wind you have engine force minus the wind force).
Probably the biggest detrimental factor is that when setting you are not steadily setting in the same direction. The combination of prop walk and/or crosswind means the the boat is rotating while applying reverse power so you are applying power in a curve as the anchor is trying to dig down. (The rudder has no effect in reverse when the the water flow over the rudder stops)

However, it is a tactic worth considering if the wind is close to non existent, or if the crosswind component and the prop walk cancel each other out and you can set in straight line especially if your anchor does not rotate well as the wind direction changes. It may be more successful in a boat with a bow thruster, or little prop walk when setting directly upwind.


Thoughts? Does anyone else use this tactic?

[noelex 77]

Here are another couple of photos from a different location showing the Mantus rotating to a change in wind direction of about 40 degrees. You can see the anchor has remained totally set and simply rotated about the one point.

Some anchors develop a very high list while rotating and then one fluke sticks up in the air. This is much less secure and the anchors concerned will occasionally break out. Most of the time they don't, but it is disconcerting to watch.

The Rocna was very good in this regard only developing a slight list. On the few occasions I have seen so far the Mantus has looked excellent, remaining even flatter than the Rocna typically does.

In the first photo you can see the chain at the bottom of the photo leading off at a 60 or 70 degree angle. The anchor has just started to rotate and you can see the scrape mark where the fluke has started to gouge away the sand as it rotates.

I have circled a small lump of weed on the photo to act as a reference mark.

[noelex 77]

The second photo shows the anchor rotated about 45 degrees. You can even see the trace in the sand where the roll bar has scraped around. The anchor has remained very flat and secure.

(My wife took both of the photos. Thanks )

[noelex 77]

Another example of an anchor shuffling rather than breaking out, rotating and then hopefully resetting.

This was a 180 degree wind shift with the Mantus.
The first photo is the original set, followed by a photo with 60 degree rotation. Followed by a 110 degree rotation.
Unfortunately I left the anchorage before the full 180 degrees, but from the final photo the rest is easy.

The anchor remains set and reasonably level while it is rotating:

[Factor]

I think it is relatively clear that the sandy desert bottom you are in is a contributor to shuffling rather than resetting, as I have experienced break ou with Supreme and Rocna.