zoidberg
Well-Known Member
Mantus v Rocna?
Over in NTL they're arguing about Guinness v Murphy's, perhaps more productively.....
Over in NTL they're arguing about Guinness v Murphy's, perhaps more productively.....
Mantus vs Rocna
- Thread starter Nina Lucia
- Start date
NormanS
Well-Known Member
I always thought that that was standard practice. It always has been with my boats anyway.
Neeves
Well-Known Member
Our little bit of string to secure the bitter end is, or are, 3 wraps of 6mm dyneema. Its about 500mm long overall but about 100mm with the wraps and is 'in' the chain locker.
We don't have a capstan - but if push came to shove we could cobble something up and use sheet winches.
One of the advantages of down sizing chain is - its lighter
Not much use then when it was 8mm - but I've invested in the future with our 6mm.
Using your snubbers to take load when you power set is not the most efficient nor effective way of power setting. if your snubber is any good then it will simply stretch and the energy developed by the engine is being used to stretch the snubber and is not setting the anchor. You are also reducing snubber life, which is related to the number of times and the amount you stretch it. You can of course set the revs relatively high and leave the stretched snubber (reducing its life further) and you power set. A strop attached to a strong point or chain lock - so much easier (and cheaper). Equally loading the windlass, its securing bolts and the foam to which your windlass might be attached is also not the best way - some form of chain lock, short strop with hook etc etc is much more sensible. Replacing a short strop is cheap, continuous stressing of bolts, windlass, deck structure is a much more expensive exercise to remedy.
I appreciate a windlass, the bolts, the deck structure should take the stress (though I'm not convinced of the latter when I see some installations on AWBs) - it seems an expensive belief when there is a simple and cheap alternative (that you should have anyway).
I see some installations where the windlass is secured to a glass/foam panel. The holes are drilled and coated , sometimes with epoxy, sometimes with Sika (they are coated to seal not reinforce). The reinforcing are penny washers (which most people never see because they do not look and they are underneath).. On older yachts, not very old - the windlass wobbles because it has been used as a strong point and the foam has crushed. I know it will never happen to you! When we took ownership and I had time to crawl around I went off and bought stainless and aluminium plate and made up fibre glass pads and replaced all our penny washers with something more appropriate. Now, with my fetish I tend only, to be invited to, look at windlass - sometimes I'm impressed, more commonly I weep. Ground tackle lockers are an after thought and incredibly difficult for an installer - get used to it! - if you have a an AWB
. Windlass installation, because there is little space, is very difficult at best inconvenient. However the difficulty pales by comparison when you need to cut the old windlass out with an angle grinder!
It was comforting to read I am not the only idiot that has lost his rode!!
Jonathan
We don't have a capstan - but if push came to shove we could cobble something up and use sheet winches.
One of the advantages of down sizing chain is - its lighter
Not much use then when it was 8mm - but I've invested in the future with our 6mm.Using your snubbers to take load when you power set is not the most efficient nor effective way of power setting. if your snubber is any good then it will simply stretch and the energy developed by the engine is being used to stretch the snubber and is not setting the anchor. You are also reducing snubber life, which is related to the number of times and the amount you stretch it. You can of course set the revs relatively high and leave the stretched snubber (reducing its life further) and you power set. A strop attached to a strong point or chain lock - so much easier (and cheaper). Equally loading the windlass, its securing bolts and the foam to which your windlass might be attached is also not the best way - some form of chain lock, short strop with hook etc etc is much more sensible. Replacing a short strop is cheap, continuous stressing of bolts, windlass, deck structure is a much more expensive exercise to remedy.
I appreciate a windlass, the bolts, the deck structure should take the stress (though I'm not convinced of the latter when I see some installations on AWBs) - it seems an expensive belief when there is a simple and cheap alternative (that you should have anyway).
I see some installations where the windlass is secured to a glass/foam panel. The holes are drilled and coated , sometimes with epoxy, sometimes with Sika (they are coated to seal not reinforce). The reinforcing are penny washers (which most people never see because they do not look and they are underneath).. On older yachts, not very old - the windlass wobbles because it has been used as a strong point and the foam has crushed. I know it will never happen to you! When we took ownership and I had time to crawl around I went off and bought stainless and aluminium plate and made up fibre glass pads and replaced all our penny washers with something more appropriate. Now, with my fetish I tend only, to be invited to, look at windlass - sometimes I'm impressed, more commonly I weep. Ground tackle lockers are an after thought and incredibly difficult for an installer - get used to it! - if you have a an AWB
. Windlass installation, because there is little space, is very difficult at best inconvenient. However the difficulty pales by comparison when you need to cut the old windlass out with an angle grinder!It was comforting to read I am not the only idiot
that has lost his rode!!Jonathan
geem
Well-Known Member
Our little bit of string to secure the bitter end is, or are, 3 wraps of 6mm dyneema. Its about 500mm long overall but about 100mm with the wraps and is 'in' the chain locker.
We don't have a capstan - but if push came to shove we could cobble something up and use sheet winches.
One of the advantages of down sizing chain is - its lighter
Using your snubbers to take load when you power set is not the most efficient nor effective way of power setting. if your snubber is any good then it will simply stretch and the energy developed by the engine is being used to stretch the snubber and is not setting the anchor. You are also reducing snubber life, which is related to the number of times and the amount you stretch it. You can of course set the revs relatively high and leave the stretched snubber (reducing its life further) and you power set. A strop attached to a strong point or chain lock - so much easier (and cheaper). Equally loading the windlass, its securing bolts and the foam to which your windlass might be attached is also not the best way - some form of chain lock, short strop with hook etc etc is much more sensible. Replacing a short strop is cheap, continuous stressing of bolts, windlass, deck structure is a much more expensive exercise to remedy.
I appreciate a windlass, the bolts, the deck structure should take the stress (though I'm not convinced of the latter when I see some installations on AWBs) - it seems an expensive belief when there is a simple and cheap alternative (that you should have anyway).
I see some installations where the windlass is secured to a glass/foam panel. The holes are drilled and coated , sometimes with epoxy, sometimes with Sika (they are coated to seal not reinforce). The reinforcing are penny washers (which most people never see because they do not look and they are underneath).. On older yachts, not very old - the windlass wobbles because it has been used as a strong point and the foam has crushed. I know it will never happen to you! When we took ownership and I had time to crawl around I went off and bought stainless and aluminium plate and made up fibre glass pads and replaced all our penny washers with something more appropriate. Now, with my fetish I tend only, to be invited to, look at windlass - sometimes I'm impressed, more commonly I weep. Ground tackle lockers are an after thought and incredibly difficult for an installer - get used to it! - if you have a an AWB
It was comforting to read I am not the only idiot
Jonathan
Thats interesting. Our snubber is three strand nylon. Not expensive stuff. Current one is two years old but who knows how much life it has left. I always set the anchor with the snubber on. I often dive on the anchor and its always set after I have given ot some revs. Surely once the snubber has stretched the load on the anchor is the same as if I was pulling with the chain assuming I didnt give it a load of revs in reverse prior to the anchor chain going tight? A snatch load would not be good for the windlass.
In a previous life I used to race four wheel drive buggies. We used kenetic energy recovery ropes. The idea was to use the weight of the tow vehicle to extract the stuck vehicle. You would go at full pelt with a slack rope and the stuck vehicle would easily exit the mud with no snatch or jerk due to the stretchy nylon rope. The full load of the tow vehicle plus the velocity of the tow vehicle did the work. Apply this to snubbers, heavy boat on the end and you have a lot of kinetic energy to set your anchor. There is no way that setting an anchor with the snubber on is detrimental to the set. I would say from my experiemce it would enhance the set.
Neeves
Well-Known Member
With snatch retrieval you are using the energy of the 'free' (not bogged) vehicle and the energy stored in the elastic rope to free that which is bogged (you would usually also use the drive of the bogged vehicle as well). So you get 2 or 3 bites at the cherry, all at once. If you do not, or did not need that potential energy, stored energy, in the elastic rope (I think they are called snatch ropes here) then you could use a bit of dyneema. The reason to use elastic is that you transfer some of the energy to the rope (and store it there - as 'stretch') once the energy in the rope and the energy of the engine and the momentum of the free vehicle (and some from the bogged vehicle) are added together you hopefully have enough to free the bogged vehicle.
Its the basis of using a snubber on a rode - the yacht develops momentum, kinetic energy as it moves through veering or horsing (or both). When the yacht reaches the end of its tether (the rode) that energy (or momentum) has to go somewhere - it can be transmitted down the chain (which might effectively be a steel rod) to the anchor - and the anchor gets a kick up the backside from the yacht - in the worst case scenario it pops out and drags. The alternative is to transfer that kinetic energy of the moving yacht and 'store' it in the snubber (and in the catenary) - as potential energy. Usually the potential energy is released as the yacht is 'pulled back' by the elasticity.
If you use a snubber the catenary and snubber share the duty but the chain has a finite limit and its effectiveness (or its ability to store energy) reduces as the chain straightens. The snubber's elasticity, its ability to store energy, is roughly linear where as the catenary can store less and less energy as the catenary straightens.
What you do is neatly illustrated here:
https://www.google.com/search?clien....197.197.0j1......0....1..gws-wiz.Kg5ob4ic3RM
As the engine is run in reverse the energy you want to utilise to set the anchor is actually divided, some is setting the anchor but some is stretching the snubber (and in this case some is being used to drive the yacht backwards. The anchor does set - but its inefficient and not using the full reverse of the engine (some is balancing the snubber and some is driving the yacht backwards (as the chain runs out) . The alternative is to use a hard securement and then all the energy of the engine goes to straightening the catenary or to the anchor, no stretch and the only movement backwards is from the catenary straightening (remember as it straightens it can absorb less and less energy). There is no snatch load, revs are increased gently.
There i nothing wrong with using a snubber - it just not efficient and reduces snubber life.
But going back to the OP:
The video also illustrates 2 issues
Most modern anchors (and some of the older designs) when they set bury both the toe and the shackle at the same time. This then results in the shackle and some chain being buried. Anchor's dragging appears to be due in part to a yacht moving, yawing and horsing - and some of this movement is blanketed or reduced if the chain is buried. If no chain is buried then any movement of the yacht is directed directly to the anchor as there is no buried chain - and it will be more prone to dragging from yawing. Because of the way a Mantus sets - chain is not quickly, nor deeply, buried (if buried at all).
If you don't believe this lay chain on the seabed and pull it sideways. Now tie it to a buried stone so that. say, 1m is buried - how easy is it to move the chain?
There is a bit more to it than this - but this will suffice, just now
The second issue is that with a Mantus if the 'long' of shank is horizontal the fluke is at an angle to the seabed of 16/18 degrees. (look at a drawing of a Mantus and measure the angle between 'long' of shank and fluke - its 16/18 degrees). Look at, say, a Rocna (work out how to measure the angle) and you will find its fluke will be at about 25/35 degrees to the seabed. Now simply think which one looks to have more hold, one at 16 degrees (almost flat) or one at 30 degrees. The difference in hold is a factor of 2.
That 16/18 degree for a Mantus is amazingly consistent. For some reasons other anchors are more variable, I've measured Rocna between 25 and 35 degree, but they average about 30 degrees.
Here is another video illustrating the constancy of the 16/18 degree set of the Mantus - and there is a whole album of stills, or there was, showing the same thing.
https://www.youtube.com/watch?v=LDC0g1GzdUc
Look at the amount of buried chain in the video, effectively none.
When you look at a set Rocna - look at the amount of buried chain.
Jonathan
Its the basis of using a snubber on a rode - the yacht develops momentum, kinetic energy as it moves through veering or horsing (or both). When the yacht reaches the end of its tether (the rode) that energy (or momentum) has to go somewhere - it can be transmitted down the chain (which might effectively be a steel rod) to the anchor - and the anchor gets a kick up the backside from the yacht - in the worst case scenario it pops out and drags. The alternative is to transfer that kinetic energy of the moving yacht and 'store' it in the snubber (and in the catenary) - as potential energy. Usually the potential energy is released as the yacht is 'pulled back' by the elasticity.
If you use a snubber the catenary and snubber share the duty but the chain has a finite limit and its effectiveness (or its ability to store energy) reduces as the chain straightens. The snubber's elasticity, its ability to store energy, is roughly linear where as the catenary can store less and less energy as the catenary straightens.
What you do is neatly illustrated here:
https://www.google.com/search?clien....197.197.0j1......0....1..gws-wiz.Kg5ob4ic3RM
As the engine is run in reverse the energy you want to utilise to set the anchor is actually divided, some is setting the anchor but some is stretching the snubber (and in this case some is being used to drive the yacht backwards. The anchor does set - but its inefficient and not using the full reverse of the engine (some is balancing the snubber and some is driving the yacht backwards (as the chain runs out) . The alternative is to use a hard securement and then all the energy of the engine goes to straightening the catenary or to the anchor, no stretch and the only movement backwards is from the catenary straightening (remember as it straightens it can absorb less and less energy). There is no snatch load, revs are increased gently.
There i nothing wrong with using a snubber - it just not efficient and reduces snubber life.
But going back to the OP:
The video also illustrates 2 issues
Most modern anchors (and some of the older designs) when they set bury both the toe and the shackle at the same time. This then results in the shackle and some chain being buried. Anchor's dragging appears to be due in part to a yacht moving, yawing and horsing - and some of this movement is blanketed or reduced if the chain is buried. If no chain is buried then any movement of the yacht is directed directly to the anchor as there is no buried chain - and it will be more prone to dragging from yawing. Because of the way a Mantus sets - chain is not quickly, nor deeply, buried (if buried at all).
If you don't believe this lay chain on the seabed and pull it sideways. Now tie it to a buried stone so that. say, 1m is buried - how easy is it to move the chain?
There is a bit more to it than this - but this will suffice, just now
The second issue is that with a Mantus if the 'long' of shank is horizontal the fluke is at an angle to the seabed of 16/18 degrees. (look at a drawing of a Mantus and measure the angle between 'long' of shank and fluke - its 16/18 degrees). Look at, say, a Rocna (work out how to measure the angle) and you will find its fluke will be at about 25/35 degrees to the seabed. Now simply think which one looks to have more hold, one at 16 degrees (almost flat) or one at 30 degrees. The difference in hold is a factor of 2.
That 16/18 degree for a Mantus is amazingly consistent. For some reasons other anchors are more variable, I've measured Rocna between 25 and 35 degree, but they average about 30 degrees.
Here is another video illustrating the constancy of the 16/18 degree set of the Mantus - and there is a whole album of stills, or there was, showing the same thing.
https://www.youtube.com/watch?v=LDC0g1GzdUc
Look at the amount of buried chain in the video, effectively none.
When you look at a set Rocna - look at the amount of buried chain.
Jonathan
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geem
Well-Known Member
Neeves
Well-Known Member
Actually you cannot do as you suggest.
Whether you use all chain or chain and an elastic snubber.
In both cases the engine provides the energy, the yacht moves aft and develops kinetic energy which is greater than the energy provided by the engine (call it momentum if you like). The catenary 'straightens' and the snubber stretches and both have potential energy which at some point, the momentum will decrease (the speed will reduce). and the potential energy will become greater than the energy (constant) provided by the engine - the (larger) potential energy will be transferred to the yacht and it will yo-yo forward. You can increase revs - but the same will happen. For an instant the tension will reach a maximum (and as you say, tension is tension) and then the yacht moves forward the tension will decrease. You can do this any number of times you like - but you will achieve a similar tension with simply using the chain (no snubber). All you achieve is a reduction in snubber life - which may not be significant, you will not know. Tensioning the chain will have minimal impact on chain life (or if it does have impact - you have the wrong chain ).
But a prematurely failed snubber at 1am is a real nuisance (and unnecessary).
Snubber life is a function of usage and your method ages snubber 'life' unnecessarily. Using chain (and a chain lock) costs nothing 'extra' - so why do it. You need the chain lock (or short strop) to protect the windlass - so you have them, or it, anyway.
I am not suggesting taking a run, backwards, and snatch loading the anchor nor snatch loading the deck gear. A gentle increase in reverse so that the rode lifts and straightens.
I simply see no benefit to using a snubber but I do see downsides.
Your way works - but it has no advantage and does not set the anchor any deeper.
Maybe I'm too parsimonious and should not worry about snubber failure
Jonathan
I appreciate I am part cause - but we have been slightly guilty of thread drift
J
Whether you use all chain or chain and an elastic snubber.
In both cases the engine provides the energy, the yacht moves aft and develops kinetic energy which is greater than the energy provided by the engine (call it momentum if you like). The catenary 'straightens' and the snubber stretches and both have potential energy which at some point, the momentum will decrease (the speed will reduce). and the potential energy will become greater than the energy (constant) provided by the engine - the (larger) potential energy will be transferred to the yacht and it will yo-yo forward. You can increase revs - but the same will happen. For an instant the tension will reach a maximum (and as you say, tension is tension) and then the yacht moves forward the tension will decrease. You can do this any number of times you like - but you will achieve a similar tension with simply using the chain (no snubber). All you achieve is a reduction in snubber life - which may not be significant, you will not know. Tensioning the chain will have minimal impact on chain life (or if it does have impact - you have the wrong chain
). But a prematurely failed snubber at 1am is a real nuisance (and unnecessary).
Snubber life is a function of usage and your method ages snubber 'life' unnecessarily. Using chain (and a chain lock) costs nothing 'extra' - so why do it. You need the chain lock (or short strop) to protect the windlass - so you have them, or it, anyway.
I am not suggesting taking a run, backwards, and snatch loading the anchor nor snatch loading the deck gear. A gentle increase in reverse so that the rode lifts and straightens.
I simply see no benefit to using a snubber but I do see downsides.
Your way works - but it has no advantage and does not set the anchor any deeper.
Maybe I'm too parsimonious and should not worry about snubber failure
Jonathan
I appreciate I am part cause - but we have been slightly guilty of thread drift
J
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geem
Well-Known Member
Jonathan. You may yaw yaw backwards and forwards in your lightweight cat but I can assure you it doesnt happen in a 19t boat with a powerful engine. You may get a couple of cycles of bounce but it very quicky settles to a steady state pull. Simple mechanics. The cycling will decrease to zero over a period of time. With a lighter boat with a less powerful engine it may take longer. Having never set my anchor without first setting the snubber and having checked the anchor to see it well set there is no disadvantage to us to set like this. If you have a perfect set anchor how do you improve on this? Like I said little engine light boat may be different. We swing a 22” prop with tremendous pulling power and weight. It works perfectly.
noelex
Well-Known Member
That is a video that I filmed with my wife setting the anchor. This is a better quality copy:
https://youtu.be/Ykoc7UyDezA
In real life it was exactly as it looks with the Mantus anchor setting beautifully despite a shallowish scope of only 3:1 in 4.4 m of water. Notice how quickly the Mantus sets, and how steadily and progressively it buries. No skips or jumps. This was one take only of a typical set from my Mantus, not a manufacturer’s video selected as the best of many attemps
Have a look at the angle of the chain. It is always remarkable to me that an anchor can bury with this type of force pulling the end of the shank upward. I have owned a Rocna and similarly watched many sets. There is no difference in the setting angle between these two anchors.
If you want to know how anchors behave underwater it pays to brave the sharks and take a look
. So far in this thread there has been following statements, just to name a few:
All the above is nonsense. It really doesn’t need refuting. Anyone can look at these two anchors and see the Rocna and Spade flukes and shanks are nothing like each other. Also, they are both concave not convex.
Merry Christmas and happy New Year to everyone. This is sometimes called the “silly season”, but anchor threads are silly enough year around. We don’t need to make an extra effort for the holidays
.
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Neeves
Well-Known Member
Noelex for someone who spruiked an anchor without once mentioning that the anchor in question consistently set with a 16/18 degree fluke/seabed angle where virtually every other anchor sets with a fluke/seabed angle of around 30 degrees - your comments simply lack any credibility. It is a fundamental and glaringly obvious difference - yet you chose to not notice and certainly did not mention it. You have hundreds of images - maybe you looked but cannot see.
There is also the question of hold and why you can double the hold of a Mantus by simply moving the shank to a position used by a number of unweighted fluke anchors. There is also the point that the hold of a Mantus is similar to a similarly sized Delta. Greg Kutsen has known of theses design 'defects' but has never had the courage to make a comparative test (with any independent witnesses) - I wonder why.
You have been quick to criticise other anchors but omitted to mention glaring defects in your Mantus, I again raise the question why. You claim to have been studying anchors for over a decade - precisely what have you learnt because you simply missed 2 key design features
The incorrect location of the shank (Now is the time for you to explain why Mantus bucks other anchors)
resulting in
The low seabed/fluke angle (another opportunity for you to explain why 16 degrees develops hold over 30 degrees)
Holding capacity is a fundamental requirement for defining an anchor's effectiveness. Pictures are very illustrative (if analysed correctly) but they show nothing of performance - why don't you and Mantus make some holding capacity tests, with independent observers, and show me I am wrong.
Anchors are a safety device and your analysis is either some form of trolling of other designs - or you have been unwittingly and grossly misleading the public through simple ignorance. If it were not a safety device it would not matter - but anchors are important.
This is not silly - people have been buying anchors based on your analysis - and your analysis is damningly wrong Independent tests by the US Navy et al show the fundamental flaws in the design and independent tests of Mantus show the results outlined. How do I know, I've checked the tests and I've made my own.
Fortunately the hold of a Delta and similar hold anchors, such as Bruce, have been shown to be 'OK' and there is a trend currently to oversize - so hold of a Mantus is acceptable (and it does set easily and reliably) but kg for kg - buy a Rocna, Spade, Supreme, Excel, Knox - you will get more hold (in fact twice as much) for your kilogram).
It reminds me of the rather neat sentence:
It is easy to fool people, it is very difficult to convince them they have been fooled.
Apologies for mentioning concave instead of convex - correction gratefully accepted.
The plan view of a Spade and Rocna are so similar to be identical, same angles, same proportions. Why don't you lay two of your many images side by side and show me I am wrong. Its almost as if Rocna is a copy, slightly modified to cater for different materials and manufacturing techniques. How do I know they are similar, I checked.
Take a Delta shank and a french curve. Join the corners of the Delta shank, which is similar to a Rocna shank, and you will find a Spade shank. Why don't you do as I suggest, take a couple of your images, join the dots and show me I am wrong. Yes one is hollow - but it does not change the profile. How do I know - I did it.
And why my interest - they are a safety device, Mantus has not been exhaustively tested (and if it has been tested by the manufacturer the results have not been publicised) - but this thread is an example - people think, for what ever reason, that Mantus is on a par with Rocna - it is not. And a thought like that, and I have seen similar, can be dangerous (and at best a waste of money).
Jonathan
There is also the question of hold and why you can double the hold of a Mantus by simply moving the shank to a position used by a number of unweighted fluke anchors. There is also the point that the hold of a Mantus is similar to a similarly sized Delta. Greg Kutsen has known of theses design 'defects' but has never had the courage to make a comparative test (with any independent witnesses) - I wonder why.
You have been quick to criticise other anchors but omitted to mention glaring defects in your Mantus, I again raise the question why. You claim to have been studying anchors for over a decade - precisely what have you learnt because you simply missed 2 key design features
The incorrect location of the shank (Now is the time for you to explain why Mantus bucks other anchors)
resulting in
The low seabed/fluke angle (another opportunity for you to explain why 16 degrees develops hold over 30 degrees)
Holding capacity is a fundamental requirement for defining an anchor's effectiveness. Pictures are very illustrative (if analysed correctly) but they show nothing of performance - why don't you and Mantus make some holding capacity tests, with independent observers, and show me I am wrong.
Anchors are a safety device and your analysis is either some form of trolling of other designs - or you have been unwittingly and grossly misleading the public through simple ignorance. If it were not a safety device it would not matter - but anchors are important.
This is not silly - people have been buying anchors based on your analysis - and your analysis is damningly wrong Independent tests by the US Navy et al show the fundamental flaws in the design and independent tests of Mantus show the results outlined. How do I know, I've checked the tests and I've made my own.
Fortunately the hold of a Delta and similar hold anchors, such as Bruce, have been shown to be 'OK' and there is a trend currently to oversize - so hold of a Mantus is acceptable (and it does set easily and reliably) but kg for kg - buy a Rocna, Spade, Supreme, Excel, Knox - you will get more hold (in fact twice as much) for your kilogram).
It reminds me of the rather neat sentence:
It is easy to fool people, it is very difficult to convince them they have been fooled.
Apologies for mentioning concave instead of convex - correction gratefully accepted.
The plan view of a Spade and Rocna are so similar to be identical, same angles, same proportions. Why don't you lay two of your many images side by side and show me I am wrong. Its almost as if Rocna is a copy, slightly modified to cater for different materials and manufacturing techniques. How do I know they are similar, I checked.
Take a Delta shank and a french curve. Join the corners of the Delta shank, which is similar to a Rocna shank, and you will find a Spade shank. Why don't you do as I suggest, take a couple of your images, join the dots and show me I am wrong. Yes one is hollow - but it does not change the profile. How do I know - I did it.
And why my interest - they are a safety device, Mantus has not been exhaustively tested (and if it has been tested by the manufacturer the results have not been publicised) - but this thread is an example - people think, for what ever reason, that Mantus is on a par with Rocna - it is not. And a thought like that, and I have seen similar, can be dangerous (and at best a waste of money).
Jonathan
Neeves
Well-Known Member
geem,,
I owe you an apology that I should have sent earlier.
It was unintentionally implied that your stated anchor/rode/snubber arrangement/deployment was an example of bad seamanship. I had read your posts, previous to when I made the implication, to mean that you used a snubber and relied on the windlass clutch to secure the chain. I think such a practice is wrong as if the snubber fails the tension is then directed to the windlass. Windlass shafts are fairly indestructible but bearings, seals and gearboxes are less robust and the installations I sometimes see on modern yachts looks, sometimes, questionable. I try to let people consider moving any tension to a strong point (not the windlass), chain locks, short strops with a claw etc.
However later you mention you also use a lock - and thus my implication you were demonstrating poor seamen ship was wide of the mark.
Moreover you appear to be located in a more exotic part of the world - and to get there - no-one least of all me can question your seamanship.
Please accept my abject apologies for any offence caused.
I was also unaware that your vessel is 19t - and I must confess most of what I say is aimed at significantly smaller yachts (commonly and affectionately called AWBs). I'm amazed that you might suffer from either yawing or horsing with a yacht that size - but it, yawing, horsing, would commonly, deleteriously impact yachts used by many on this forum. There are a few using larger yachts (the sort I would want to be on if crossing oceans) but most of us sail something slightly smaller with different equipment (including ground tackle) demands (to the demands of 'real' yachts ).
Our experiences are both valid, yours must certainly be, but from opposite ends of the spectrum, our 7t (cruising weight, fully stocked), high windage cat, and your 19t ocean greyhound.
It is difficult to cater for every yacht and I am very guilty of not qualifying may statements - that I'm commonly focussed at the 20'-45' AWB, - or if you like 'plastic fantastics'.
Jonathan
I owe you an apology that I should have sent earlier.
It was unintentionally implied that your stated anchor/rode/snubber arrangement/deployment was an example of bad seamanship. I had read your posts, previous to when I made the implication, to mean that you used a snubber and relied on the windlass clutch to secure the chain. I think such a practice is wrong as if the snubber fails the tension is then directed to the windlass. Windlass shafts are fairly indestructible but bearings, seals and gearboxes are less robust and the installations I sometimes see on modern yachts looks, sometimes, questionable. I try to let people consider moving any tension to a strong point (not the windlass), chain locks, short strops with a claw etc.
However later you mention you also use a lock - and thus my implication you were demonstrating poor seamen ship was wide of the mark.
Moreover you appear to be located in a more exotic part of the world - and to get there - no-one least of all me can question your seamanship.
Please accept my abject apologies for any offence caused.
I was also unaware that your vessel is 19t - and I must confess most of what I say is aimed at significantly smaller yachts (commonly and affectionately called AWBs). I'm amazed that you might suffer from either yawing or horsing with a yacht that size - but it, yawing, horsing, would commonly, deleteriously impact yachts used by many on this forum. There are a few using larger yachts (the sort I would want to be on if crossing oceans) but most of us sail something slightly smaller with different equipment (including ground tackle) demands (to the demands of 'real' yachts
). Our experiences are both valid, yours must certainly be, but from opposite ends of the spectrum, our 7t (cruising weight, fully stocked), high windage cat, and your 19t ocean greyhound.
It is difficult to cater for every yacht and I am very guilty of not qualifying may statements - that I'm commonly focussed at the 20'-45' AWB, - or if you like 'plastic fantastics'.
Jonathan
geem
Well-Known Member
geem,,
I owe you an apology that I should have sent earlier.
It was unintentionally implied that your stated anchor/rode/snubber arrangement/deployment was an example of bad seamanship. I had read your posts, previous to when I made the implication, to mean that you used a snubber and relied on the windlass clutch to secure the chain. I think such a practice is wrong as if the snubber fails the tension is then directed to the windlass. Windlass shafts are fairly indestructible but bearings, seals and gearboxes are less robust and the installations I sometimes see on modern yachts looks, sometimes, questionable. I try to let people consider moving any tension to a strong point (not the windlass), chain locks, short strops with a claw etc.
However later you mention you also use a lock - and thus my implication you were demonstrating poor seamen ship was wide of the mark.
Moreover you appear to be located in a more exotic part of the world - and to get there - no-one least of all me can question your seamanship.
Please accept my abject apologies for any offence caused.
I was also unaware that your vessel is 19t - and I must confess most of what I say is aimed at significantly smaller yachts (commonly and affectionately called AWBs). I'm amazed that you might suffer from either yawing or horsing with a yacht that size - but it, yawing, horsing, would commonly, deleteriously impact yachts used by many on this forum. There are a few using larger yachts (the sort I would want to be on if crossing oceans) but most of us sail something slightly smaller with different equipment (including ground tackle) demands (to the demands of 'real' yachts
Our experiences are both valid, yours must certainly be, but from opposite ends of the spectrum, our 7t (cruising weight, fully stocked), high windage cat, and your 19t ocean greyhound.
It is difficult to cater for every yacht and I am very guilty of not qualifying may statements - that I'm commonly focussed at the 20'-45' AWB, - or if you like 'plastic fantastics'.
Jonathan
Jonathan, no problem. Lots of far worse things get said on this forum, but thank you anyway.
I always read your posts with interest. Most if not all of what you write relates to our boat in some shape or form. We dont yaw like many AWB as we have the windage of the mizzen mast. In gusty 40kt conditions with a small hill in fron of us, we have seen wind veer through more than 90deg. This does lean us over as the full force of the wind hits on or near to the beam. The snubber takes the strain in these conditions. I have set a shorter snubber with the longer snubber as well should the longer one break. It hasnt yet. Long snubber is 9m, short snubber is 5m. If the longer snubber was to break I would still have some snubbing going on before I got to fit a new long snubber. A very short line in these conditions as a back up would not be great with minimal snubbing and lots of load on that deck fitting. Most of the time the loads on the long snubber are not significant but they do make life onboard more comfortable and quiter.
Keep up the good work
thinwater
Well-Known Member
1. I did some test in shallow water, setting anchors by using momentum, using bot polyester (non stretch) and nylon (stretch) rodes. Te nylon resulted in considerably deeper sets and less tendency to rip the anchor out during setting. I tested in both fine sand and soft mud. Unlike driving a nail into wood or stabbing a straw through a potato, the bottom is a viscus material, and thus time and force both matter. I'm sure this varies with the bottom material, since some are not viscus in this way. Consider the difference between silly putty (rheopectic) and paint sag preventers (thixotropic). That said, I would love to see others test this, side by side, and see what they learn. I'm guessing "it depends."
2. I wonder why none of the anchor manufactures in question has sponsored side by side testing. There are some good reasons. (1) It is very expensive and they may not have the budget--I'm pretty sure that's the reason magazines don't do this often. (2) They might not come out on top on any given day, since the bottom is a huge variable. That would be embarrassing. (3) A single test may carry no more weight than internet hype. This actually makes some sense, since straight line holding capacity is only one factor, although among those we are considering, they do pretty well all-around.
3. Is it about average holding capacity in good bottoms (which is very high in all cases), or is it about the the outliers? (1) Should you report the average, the best, or the worst that would have felt like it set? (2) How well do they tolerate trash in the bottom? It's hard to set up a test, but I did a lot of testing in trashy mud, and how an anchor reacts to a buried stick, shells, or leaves can be the main thing. Some have moments of brilliance but not consistently, while others are consistent (I refuse to name-names in this thread--that discussion would require a chapter). (3) Difficult bottoms. Yes, you could move, but even in good sand there are bad spots you did not see. There can be hardpan under the sand, deep enough to withstand a power set, but not enough for a storm. Or a patch of trash.
(4) Most will buy based on either fashion, price, or tradition. We've seen some of those on this thread. Perhaps their old anchor is sized big enough to work, so many are fine just as they are. Some will buy what everyone has or what everyone is talking about (which is different every year). You attract these with low prices and advertising, not testing, which they will never see. So spend the money on advertising and pricing.
All things considered, if I had a good design I'd focus on marketing. I'd give anchors to prominent sailors.
Very complicated. I would not want to pick a "best all-around." Heck, one of my favorites is an 80-year old design (not CQR) I've used on three boats.
2. I wonder why none of the anchor manufactures in question has sponsored side by side testing. There are some good reasons. (1) It is very expensive and they may not have the budget--I'm pretty sure that's the reason magazines don't do this often. (2) They might not come out on top on any given day, since the bottom is a huge variable. That would be embarrassing. (3) A single test may carry no more weight than internet hype. This actually makes some sense, since straight line holding capacity is only one factor, although among those we are considering, they do pretty well all-around.
3. Is it about average holding capacity in good bottoms (which is very high in all cases), or is it about the the outliers? (1) Should you report the average, the best, or the worst that would have felt like it set? (2) How well do they tolerate trash in the bottom? It's hard to set up a test, but I did a lot of testing in trashy mud, and how an anchor reacts to a buried stick, shells, or leaves can be the main thing. Some have moments of brilliance but not consistently, while others are consistent (I refuse to name-names in this thread--that discussion would require a chapter). (3) Difficult bottoms. Yes, you could move, but even in good sand there are bad spots you did not see. There can be hardpan under the sand, deep enough to withstand a power set, but not enough for a storm. Or a patch of trash.
(4) Most will buy based on either fashion, price, or tradition. We've seen some of those on this thread. Perhaps their old anchor is sized big enough to work, so many are fine just as they are. Some will buy what everyone has or what everyone is talking about (which is different every year). You attract these with low prices and advertising, not testing, which they will never see. So spend the money on advertising and pricing.
All things considered, if I had a good design I'd focus on marketing. I'd give anchors to prominent sailors.
Very complicated. I would not want to pick a "best all-around." Heck, one of my favorites is an 80-year old design (not CQR) I've used on three boats.
MM5AHO
Well-Known Member
The late Prof. John Knox did "side by side " testing before he designed his own anchor. The results of that testing (to which he later added the Knox anchor) are available in various places. Rocna even lauded that testing as being "scientific" (although as other rightly point out, "it depends" - bottoms and anchors and conditions are so variable that like for like comparison is very difficult). His testing showed consistent results that there's a lot of difference between same sized, but different design anchors in the same substrate on the same day. Nearly as much as 10 to 1 difference.
His test design was a bit more complicated than just measuring the pull required to cause dragging.
His test design was a bit more complicated than just measuring the pull required to cause dragging.
thinwater
Well-Known Member
Do you mean the PBO article? If there is more information, please direct me to it. I am interested.
I see three gaps in the testing. These are NOT intended as criticisms. I have a great deal of respect for John Knox. They are more in the way of questions and clarifications.
1. Infinite scope. Some anchors are impressive at short scope (Fortress--in fact, they can be a bugger to recover at 1:1 scope--can't have it both ways!) and some are not (Delta, certain NG). Something like 5:1 or 7:1 is more relevant, though testing at constant scope is quite difficult in a practical sense.
2. Only one bottom. Additionally, exposed flats are different from constantly submerged bottoms (I've tested on both). Some anchors excel in firm sand, others excel in soft mud, and a very few in both. That which does best in both (Fortress) can be challenged by trash and reset. And then ther eis the whole business of performance in rock and weed, where we actually have trouble.
3. Steady holding vs. dynamic holding--both are part true. The reason is that only the most severe gusts will challenge the static holding capacity, resulting in a few cm of movement, and often times, deeper setting. The second problem is an artifact of the test method; he did not leave the anchors set at static holding long enough for the soil to consolidate around the new position, as it often will. He soon restarted the winch and it apears the anchor moving, but note that initially the curve line is very steep (particularly evident wit h the Spade). What you are actually seeing is increased stretch in the polyester line, as it loads up to the new, increased static holding capacity of the anchor. If he had jogged the winch for only a few seconds, or increased the tension very slowly, he would have seen tension increase and then hold at a higher level, with NO anchor movement. I have seen this in testing. The truth lies between the static and dynamic values, because he did not wait and then retention the anchors. This is complicated and I understand why he simplified it. It probably has very little effect on final rank ordering. However, it explains how apparently poor anchors out hold their test results.
Neeves
Well-Known Member
You need to be careful of some of John's (Knox) work (and some of the conclusions). As Thinwater points out he had stretch in his polyester line - and the issue is - he varied the rode. From memory he defined the rode he used but he used different rodes for different tests. You can compare one anchor with another in one test but not, necessarily, compare one batch of testing with another batch. The order of excellence might be the same but the overall values cannot, always, be used.
He was not hiding anything - the detail was always there.
And referring again to something Thinwater mentions - you really need multiple pulls of an anchor to develop any decent significance. There are simply too many variables to reply on one pull. Testing one anchor, alone, is obviously a waste of time so you need multiple anchors. After all if you make anchor 'X' why would you spend time testing anchor 'Y' made by a competitor if it turns out to be better (no point in marketing a competitor's anchor!). So its all a very expensive exercise and very labour intensive - and that's just one seabed.
Fortress have done this a number of times and there is, somewhere, a wealth of information. The 2006 West Marine testing was as good as you will get and Voile et Voileurs have similar good results. Testing has gone out of fashion other than the Fortress Chesapeake tests, maybe costs) and there are now a couple of anchors (at least) that have not enjoyed testing Mantus being one, but also Vulcan. We have the Lewmar anchors waiting in the wings and I know of at least one new, and completely original design 'possibly' coming out of the US - maybe we will see a new batch of testing.
What is odd, or I find it odd, after the 'Anchor Wars', which were about hold and at the time everyone agreed that hold is fundamental - people are happy to buy anchors with basically no hold data, Mantus and Vulcan (and maybe others). As Thinwater says - focus on marketing you will get more bang for your buck (or more sales) given that both anchors appear to be sold without any hold data.
It is easy to fool people but difficult to convince them they have been fooled - but there again, maybe they are not fooled,
The other issue is bias - you really need some form of independence, impartiality - and that's difficult (how many people want to stand around getting cold wet and muddy for an anchor maker?). Though even partiality seems acceptable to some, but not others.
The other major factor on anchor testing is that though holding capacity data on a decently, or appropriately, sized anchor can be good the anchor might still drag. 'Fouling' of the toe: shell, wood, seaweed can destroy an anchor's hold (as Thinwater mentions) but the frequency of dragging suggests there is more to it (and I point to yawing and horsing - and yawing is one reason we use a 'V' anchor arrangement at times and why we want to bury chain, as well as the anchor). Yawing and horsing have nothing to do with the anchor per se (they are a characteristic of the yacht and conditions) but having an anchor more resistant to yawing/horsing is something that has not been defined (and I'm not sure how one might develop a test).
I know that burying chain and anchoring in a 'V' reduces the impact of yawing - because it can be measured (and I have measured) but whether one anchor resists the deleterious impact, in comparison to another anchor, of yawing and horsing - I don't know. Fortress always said a deep set Fortress would be reliable ( and as Thinwater mentions a deep set Fortress is a devil to retrieve) - so deep setting seems appropriate (with the retrieval compromise) - and a shallow set anchor will, obviously , be more prone to 'upsetting' than one that is deep set.
Hold is important, and still recognised by some (I think consciously or subconsciously that is why people are replacing old styles with NG) - but there is much, or a little, more to it. - including easy of setting, is it in the chandlers, does it fit on the bow roller (and maybe more important than is necessary - is it popular), and how much does it cost etc, etc and etc.
Jonathan
He was not hiding anything - the detail was always there.
And referring again to something Thinwater mentions - you really need multiple pulls of an anchor to develop any decent significance. There are simply too many variables to reply on one pull. Testing one anchor, alone, is obviously a waste of time so you need multiple anchors. After all if you make anchor 'X' why would you spend time testing anchor 'Y' made by a competitor if it turns out to be better (no point in marketing a competitor's anchor!). So its all a very expensive exercise and very labour intensive - and that's just one seabed.
Fortress have done this a number of times and there is, somewhere, a wealth of information. The 2006 West Marine testing was as good as you will get and Voile et Voileurs have similar good results. Testing has gone out of fashion other than the Fortress Chesapeake tests, maybe costs) and there are now a couple of anchors (at least) that have not enjoyed testing Mantus being one, but also Vulcan. We have the Lewmar anchors waiting in the wings and I know of at least one new, and completely original design 'possibly' coming out of the US - maybe we will see a new batch of testing.
What is odd, or I find it odd, after the 'Anchor Wars', which were about hold and at the time everyone agreed that hold is fundamental - people are happy to buy anchors with basically no hold data, Mantus and Vulcan (and maybe others). As Thinwater says - focus on marketing you will get more bang for your buck (or more sales) given that both anchors appear to be sold without any hold data.
It is easy to fool people but difficult to convince them they have been fooled - but there again, maybe they are not fooled,
The other issue is bias - you really need some form of independence, impartiality - and that's difficult (how many people want to stand around getting cold wet and muddy for an anchor maker?). Though even partiality seems acceptable to some, but not others.
The other major factor on anchor testing is that though holding capacity data on a decently, or appropriately, sized anchor can be good the anchor might still drag. 'Fouling' of the toe: shell, wood, seaweed can destroy an anchor's hold (as Thinwater mentions) but the frequency of dragging suggests there is more to it (and I point to yawing and horsing - and yawing is one reason we use a 'V' anchor arrangement at times and why we want to bury chain, as well as the anchor). Yawing and horsing have nothing to do with the anchor per se (they are a characteristic of the yacht and conditions) but having an anchor more resistant to yawing/horsing is something that has not been defined (and I'm not sure how one might develop a test).
I know that burying chain and anchoring in a 'V' reduces the impact of yawing - because it can be measured (and I have measured) but whether one anchor resists the deleterious impact, in comparison to another anchor, of yawing and horsing - I don't know. Fortress always said a deep set Fortress would be reliable ( and as Thinwater mentions a deep set Fortress is a devil to retrieve) - so deep setting seems appropriate (with the retrieval compromise) - and a shallow set anchor will, obviously , be more prone to 'upsetting' than one that is deep set.
Hold is important, and still recognised by some (I think consciously or subconsciously that is why people are replacing old styles with NG) - but there is much, or a little, more to it. - including easy of setting, is it in the chandlers, does it fit on the bow roller (and maybe more important than is necessary - is it popular), and how much does it cost etc, etc and etc.
Jonathan
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Neeves
Well-Known Member
If you want to know how anchors behave underwater it pays to brave the sharks and take a look
The Whitundays are home to Australia's greatest concentration of charter yachts and a very popular destination for many of our cruisers in winter.
https://www.theguardian.com/austral...tack-woman-and-child-bitten-in-shallow-waters
Its great to have encouragement.
Jonathan
edit,
I'm not sure it make any difference when you are bitten (when examining your anchor) - but there are now suggestions that recent bites might have been toads fish.
close edit
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zoidberg
Well-Known Member
Toadfish, now....??
https://www.wikiwand.com/en/Common_toadfish
'Just when you thought it wa safe to get back in the water'
https://www.wikiwand.com/en/Common_toadfish
'Just when you thought it wa safe to get back in the water'
Neeves
Well-Known Member
Safe in the water?
We have not mentioned stone fish yet (which ha nothing to do with stone soup).
https://en.wikipedia.org/wiki/Synanceia
We have not mentioned stone fish yet (which ha nothing to do with stone soup).
https://en.wikipedia.org/wiki/Synanceia
MM5AHO
Well-Known Member
In reference to the John Knox testing. I wasn't there, but I do have the original files of his notes. (massive tomes of paper). I note that most of the testing was done using steel cable, not elastic ropes. Presumably to take out another variable, and to be able to measure force that is applied to the anchor from the other end of the rode.
On scope, as most numerical testing was done at an angle equating to high scope, (>5), short scope effects were only included in the boat testing later.
On independence, at the time of the testing he hadn't invented his anchor. It was his opinion that the disappointing results required some design thought, and that led to the anchor development. There was a lot of subsequent testing on various iterations of the design, mostly using the same measurement rig used in earlier comparative tests.
Not all the testing was published, but a few still existing reference (web based) are listed on the website.
On scope, as most numerical testing was done at an angle equating to high scope, (>5), short scope effects were only included in the boat testing later.
On independence, at the time of the testing he hadn't invented his anchor. It was his opinion that the disappointing results required some design thought, and that led to the anchor development. There was a lot of subsequent testing on various iterations of the design, mostly using the same measurement rig used in earlier comparative tests.
Not all the testing was published, but a few still existing reference (web based) are listed on the website.
Other threads that may be of interest
