I hate to do this...but

Scotty, that anagram list is very funny. I promise I had no idea when I wrote the original phrase. I think I like "Conduct Science Incests" best. :D

It surely beats anchor-rankling. Or, 'boring-mooring-jawing'?



Normal service may be resumed. But it needn't be... :)
 
vyv_cox said:
My mistake, Boron, not Bismuth. Must be some reason why they didn't want to call it Boronalloy. :)
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Boringalloy?

I don't want to sound like I am stalking you Mr. Cox and picking on your posts, but I do want to suggest a correction to something else you said.

You correctly pointed out that the strength of the chain is nearly always less than the tensile strength of the shank of an anchor, whatever the shank is made of and that is certainly true. And, if the only load on the shank was a straight pull, then that would be the end of it, but that is not how loads are placed on anchor shanks, at least sometimes. When side loading occurs, the shank acts as a lever, multiplying by many times the effect of the force applied in the side load. Bend a 1/2" bolt 2" long with your hands and compare that to bending the same 1/2" bolt that is 6 feet long by way of illustration. With side loading, the quality of steel and its yield strength, that is, the force required to permanently deform the shank is of great importance, with the difference between 500 MPa and 800 MPa sometimes being the difference between failure or non failure. Would you agree?
 
Delfin said:
Boringalloy?

I don't want to sound like I am stalking you Mr. Cox and picking on your posts
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I disagree

Delfin said:
With side loading, the quality of steel and its yield strength, that is, the force required to permanently deform the shank is of great importance, with the difference between 500 MPa and 800 MPa sometimes being the difference between failure or non failure. Would you agree?
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The force required to bend a Rocna 15 with 800 MPa steel is 427 kg. For a Rocna 15 with 450 MPa steel, same section shank, it is 263 kg.

I have some measurements of wind forces made by the Anchorwatch load cell, a force 9 wind in a sheltered anchorage, no swell, generated 125 kg. ABYC predicted theoretical loads are far higher but many people believe them to be unrealistic. I have some other information based on Alain Fraysse's calculations that predicts 300 kg in 35 knots, open water.
 
vyv_cox said:
I disagree



The force required to bend a Rocna 15 with 800 MPa steel is 427 kg. For a Rocna 15 with 450 MPa steel, same section shank, it is 263 kg.

I have some measurements of wind forces made by the Anchorwatch load cell, a force 9 wind in a sheltered anchorage, no swell, generated 125 kg. ABYC predicted theoretical loads are far higher but many people believe them to be unrealistic. I have some other information based on Alain Fraysse's calculations that predicts 300 kg in 35 knots, open water.
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Non responsive, but that's fine.
 
I am always a bit cynical about calculated theoretical loads. In the past i severely bent the shank on a Danforth in quite light winds. It had dug very deeply into sand and I had to rely on wave action to break it out.

Size for size the shank cross section on the Manson Supreme is about the same as a Rocna. Do we have reports of Manson shanks bending? If not perhaps the difference in steel is important. If they are also bending perhaps the mild steel shank does not matter?
 
Having made a special journey yesterday to collect my new purchase( imported from a well-known New Zealand company) I got it home and unwrapped it. I must say it did look the part but I had more pressing matters. I dug out a hammer and centre punch and initially used it on the shank of my Manson as a basis for my test and saw no visible results.
I then hit the shank of my new purchase and could not believe it when it left a huge indentation.
I am not sure of the Bisalloy rating but I do know it is pretty poor.
What to do now. Do I take my lamb shank back to the butcher and complain or just accept it and cook it?
 
Nostrodamus said:
Having made a special journey yesterday to collect my new purchase( imported from a well-known New Zealand company) I got it home and unwrapped it. I must say it did look the part but I had more pressing matters. I dug out a hammer and centre punch and initially used it on the shank of my Manson as a basis for my test and saw no visible results.
I then hit the shank of my new purchase and could not believe it when it left a huge indentation.
I am not sure of the Bisalloy rating but I do know it is pretty poor.
What to do now. Do I take my lamb shank back to the butcher and complain or just accept it and cook it?
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You've purchased a product that the designer says must have a shank with a certain tensile strength to be safe and the product doesn't meet that standard. From the Rocna User's Guide that came with my purchase of a Rocna 10: "The Rocna was designed to address the limitations shared by all older and most newer anchors available. These designs suffer from varying combinations of the following issues:

The pertinent 'issue' the Guide refers to in this case is cited as:

"insufficient strength in the shank or other load bearing components."

Sounds like your anchor still has that issue, doesn't it?

This is actually emblematic of one of the issues many people have with the Rocna company. Rather that focusing on the value of their product, its quality, their reputation, its engineering, etc., in their 'User's Guide' they spend ink making claims of defects in their competitor's products. It would be an irritating tactic from the perspective of those competitors if Rocna's assertions were correct. Since these claims are frequently not true and their own product fails to meet the standards they say they meet but don't, irritation quickly resolves itself into outrage. Can't really blame them.
 
Delphin,
I have to thank you and others on this thread along with Rocnas refusal to speak that left me with a clear alternative when it came to anchors.
I bought the Manson Supreme which I am delighted with. With all the money left over I could even buy a few New Zeland lambs and as the saying goes!
Hence the lamb shanks. (always worthreading the full post)
 
I'll be out of range to receive/respond items from this forum for the next two weeks. I'll miss you all, too. :D:D:D

I'll be equally pleased and impressed, if this particular thread hasn't moved on when I return...
 
PeterR said:
I am always a bit cynical about calculated theoretical loads. In the past i severely bent the shank on a Danforth in quite light winds. It had dug very deeply into sand and I had to rely on wave action to break it out.

Size for size the shank cross section on the Manson Supreme is about the same as a Rocna. Do we have reports of Manson shanks bending? If not perhaps the difference in steel is important. If they are also bending perhaps the mild steel shank does not matter?
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Peter,
The difference in the steel is critically important.
The Manson and the rocna size for size have pretty much the same thickness of shank.
The beauty of the Bis80 and equivalent materials used is that they flex slightly and return to their original shape ( in layman's terms). It is of particular importance when you consider that both designs are known to dig in and stick without rotating until they are placed under intense pressure.
When they do rotate or break loose they then reset immediately.

So in you consider that you have a blade that sets and stays put and load is placed in a sideways direction on the shank then one of two things are going to happen, either the blade will break loose or rotate or the shank will bend.

If the material is even slightly below the designer's specification then it is more likely that the shank will bend. The blade will usually stay in place as it is designed to do as it is buried deep into the seabed.

A shank material that meets the spec's will not bend but will apply force to the blade in the direction of the pull.

The other critical factor that is missed by most is that each type of steel has a YS ( yield strength) and a TS or UTS ( tensile strength or ultimate tensile strength). If the force applied exceeds the YS then it will bend as the yield strength is the point at which failure of the metal occurs and this happens long before the UTS is reached.
 
dancrane said:
I'll be out of range to receive/respond items from this forum for the next two weeks. I'll miss you all, too. :D:D:D

I'll be equally pleased and impressed, if this particular thread hasn't moved on when I return...
Click to expand...

Perhaps you could invest in a homing pidgeon in order to have someone send you printouts daily:D:D:D:D
 
Due to what has been said on this thread and Rocnas disappearing act I went out and bought a Manson Supreme. It fits well in my bow roller but the pin just butts up against the widest part of the anchor shank.
I spoke to Manson who are happy for me to drill a small hole to allow the pin to go through (They say many others have done it with no reports of problems). If this is done it will be held on as snug as a bug in a rug and will self launch well.
The question is, could this compromise the integrity of the anchor and how many drill bits or what kind will I need to drill through a real high strength anchor shank?
Has anyone else done this with either a Manson or a Rocna?
 
Don't expect we'll hear from Rocna soon.
On the front page of rocna's website (since last week)...
The Rocna office was hit by the freak tornado that swept through Auckland this week. Thankfully no one was hurt, but it has taken down our phone lines and internet access. We're currently unable to receive phone calls or access our emails.

While we expect communications to be restored soon, it will take us a little longer than usual to respond if you've been in touch with us recently. We appreciate your patience while we catch up on things.

We have more details about the tornado in our news section here and video of the tornado in action and pictures of the damage done to our street.
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Don't worry,
There were only a few phone lines affected and they were made in China and put in at the begining of the year. All the othr phone lines are ok though.
 
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