Rocna anchors
- Thread starter Rob_Webb
- Start date
michael_w
Well-Known Member
No. gimmie my bruce bower, fortress kedge and CQR storm. You are welcome to the others
webcraft
Well-Known Member
And my ancient wooden gaffer, Sou'Wester and octant for navigation . . .
- N
- N
hylass
Well-Known Member
We juste recieved one.. and we did measure the weight distribution
Model : Rocna 20
weight :19,05
weight distribution on the tip: 5,78 30,3 % of the total weight
Weight distribution on the mud palm 10,02 52,6%
Weight distribution on the shank extremity 2,48 13,0%
As expected from the design, the weight on the back part (mud palm or "roll bar") of the fluke is much heavier (nearly twice) than the weight on the anchor tip..
An independant anchor test has just been performed by a Nautical Magazine.. comparing mainly "new generation" anchors and including the Rocna, but as the results have not been published yed, I can't give you the results.
Model : Rocna 20
weight :19,05
weight distribution on the tip: 5,78 30,3 % of the total weight
Weight distribution on the mud palm 10,02 52,6%
Weight distribution on the shank extremity 2,48 13,0%
As expected from the design, the weight on the back part (mud palm or "roll bar") of the fluke is much heavier (nearly twice) than the weight on the anchor tip..
An independant anchor test has just been performed by a Nautical Magazine.. comparing mainly "new generation" anchors and including the Rocna, but as the results have not been published yed, I can't give you the results.
JKay
Well-Known Member
looks a bit Delta'ish with a roll bar on the rear,which could take the weight off the tip
cheers Joe
cheers Joe
branko
Well-Known Member
Hi Hylas,
we learned a lot from your posts - thanks.Would you give me explanation regarding Spade and Delta anchors.What is the best distribution of weight in %( shank - palm)? Where the gravity center have to be for best results?
we learned a lot from your posts - thanks.Would you give me explanation regarding Spade and Delta anchors.What is the best distribution of weight in %( shank - palm)? Where the gravity center have to be for best results?
hylass
Well-Known Member
[ QUOTE ]
Would you give me explanation regarding Spade and Delta anchors.What is the best distribution of weight in %( shank - palm)? Where the gravity center have to be for best results?
[/ QUOTE ]
Thanks also for your comments.. /forums/images/graemlins/blush.gif
The Delta anchor has 26% of the total weight on the tip
The Spade anchor has 47% of the total weight on the tip
The reason is obvious.. for the intitial setting phase, the tip of the anchor has to be as heavy as possible to start the penetration process..
(or said in another way: the gravity center has to be as close as possible to the tip of the anchor)
In "soft" bottoms, the difference is not that obvious as even a light weight will easily penetrate..
but for hard bottoms (Compact sand, coral) and with weed (kelp.. ) if the tip of the anchor is not heavy enough.. the anchor will only slide on the surface and never penetrate..
Would you give me explanation regarding Spade and Delta anchors.What is the best distribution of weight in %( shank - palm)? Where the gravity center have to be for best results?
[/ QUOTE ]
Thanks also for your comments.. /forums/images/graemlins/blush.gif
The Delta anchor has 26% of the total weight on the tip
The Spade anchor has 47% of the total weight on the tip
The reason is obvious.. for the intitial setting phase, the tip of the anchor has to be as heavy as possible to start the penetration process..
(or said in another way: the gravity center has to be as close as possible to the tip of the anchor)
In "soft" bottoms, the difference is not that obvious as even a light weight will easily penetrate..
but for hard bottoms (Compact sand, coral) and with weed (kelp.. ) if the tip of the anchor is not heavy enough.. the anchor will only slide on the surface and never penetrate..
craigsmith
Well-Known Member
I don't like getting into these debates but when you see a competitor actively spreading misinformation about your product, some steps are necessary. Here goes:
A comment on weight distribution on tip
It is important to understand that a high percentage weight on tip (just under 50% for the Spade for example) is not an important factor in the setting performance of any anchor. And in fact, the high tip-weight of the Spade exists for reasons other than M Poiraud would claim.
Let's consider an example of a 20Kg anchor - equivalents would be a Rocna 20 or a Spade 100. The Rocna at 30% puts 6Kg of equivalent weight force on its tip; the Spade something around 9.5Kg.
Now consider the fact that neither anchor will set itself when sitting stationary on the bottom. Thus clearly the tip-weight alone is not enough to set the anchor.
What does set the anchor is the dynamic interaction between the anchor and the seabed once your boat starts to pull on the rode. And this force will exceed hundreds of kilos weight-force - dwarfing the forces present due to gravity. Therefore, a difference between any two anchors of a few kilos weight force on the tip is entirely insignificant.
Furthermore, M Poiraud is a tiny tiny bit hypocritical here, as his Oceane anchor (the Spade's little brother) has a tip-weight measuring less than that of the Rocna!
jkay
The roll-bar is completely hollow and weighs very little. As such it does not negatively affect that anchor's dynamics at all.
But you are correct, we have taken weight out of the tip. This is inefficient weight, such as the lead insert, that does not need to be there, and is much better put to use in other areas of the anchor, such as effective fluke area and shank strength, which translates to better holding power and durability.
The roll-bar takes care of orientating the anchor to the correct setting attitude when it lands on the seabed, which is the main objective of the lead tip-weight in any anchor that features it.
branko
As you can see from the points above, there is no real "best distribution of weight". Obviously the mathematical ideal would be 100% weight on tip, but the point to note is that this is really a nefarious argument. The dynamic behavior of the anchor is much more important. In the overall equation, setting behavior comes down to 1% tip-weight and 99% dynamics.
Okay, I hope I haven't offended anyone. I aim merely to clear up a bit of the confusion evident in the above posts. I will be happy to address any queries wrt the Rocna.
A comment on weight distribution on tip
It is important to understand that a high percentage weight on tip (just under 50% for the Spade for example) is not an important factor in the setting performance of any anchor. And in fact, the high tip-weight of the Spade exists for reasons other than M Poiraud would claim.
Let's consider an example of a 20Kg anchor - equivalents would be a Rocna 20 or a Spade 100. The Rocna at 30% puts 6Kg of equivalent weight force on its tip; the Spade something around 9.5Kg.
Now consider the fact that neither anchor will set itself when sitting stationary on the bottom. Thus clearly the tip-weight alone is not enough to set the anchor.
What does set the anchor is the dynamic interaction between the anchor and the seabed once your boat starts to pull on the rode. And this force will exceed hundreds of kilos weight-force - dwarfing the forces present due to gravity. Therefore, a difference between any two anchors of a few kilos weight force on the tip is entirely insignificant.
Furthermore, M Poiraud is a tiny tiny bit hypocritical here, as his Oceane anchor (the Spade's little brother) has a tip-weight measuring less than that of the Rocna!
jkay
The roll-bar is completely hollow and weighs very little. As such it does not negatively affect that anchor's dynamics at all.
But you are correct, we have taken weight out of the tip. This is inefficient weight, such as the lead insert, that does not need to be there, and is much better put to use in other areas of the anchor, such as effective fluke area and shank strength, which translates to better holding power and durability.
The roll-bar takes care of orientating the anchor to the correct setting attitude when it lands on the seabed, which is the main objective of the lead tip-weight in any anchor that features it.
branko
As you can see from the points above, there is no real "best distribution of weight". Obviously the mathematical ideal would be 100% weight on tip, but the point to note is that this is really a nefarious argument. The dynamic behavior of the anchor is much more important. In the overall equation, setting behavior comes down to 1% tip-weight and 99% dynamics.
Okay, I hope I haven't offended anyone. I aim merely to clear up a bit of the confusion evident in the above posts. I will be happy to address any queries wrt the Rocna.
hylass
Well-Known Member
No Craig you don’t offend anybody.. 
But I only suppose that the one who is spreading misinformation would be myself??
So, about the importance of the TIP weight for the initial setup, just have a look at the following figure.. if somebody will see any “misinformation” on it, please let me know..
I still pretend (and it seems so obvious to me) that to penetrate any tool, you must exert pressure on it, and heavier the tip of the tool.. better the penetration. And I consider it as an IMPORTANT factor..
“ And in fact, the high tip-weight of the Spade exists for reasons other than M Poiraud would claim ”
???? I will be very interested to learn what are these “ reasons other than M Poiraud would claim ” ???
Why is the Spade the only anchor to have such a massive block of LEAD on the tip.. and the only one to have as much as HALF the total anchor weight on the tip?
Only to improve the penetration..
“ What does set the anchor is the dynamic interaction between the anchor and the seabed once your boat starts to pull on the rode.”
Except that, if the initial setting due to the weight distribution on the anchor tip doesn’t exist.. when the boat start to pull on the rode.. the anchor will just slide on the bottom surface.. (see the previous figure)
Only when the anchor has started to dig in, due to its static penetration (weight on the tip) then the dynamic penetration due to the boat pulling on the rode, will continue the penetration..
“ M Poiraud is a tiny tiny bit hypocritical here, as his Oceane anchor (the Spade's little sister) has a tip-weight measuring less than that of the Rocna!”
Obvious.. as the Oceane is like the Rocna, an UNBALASTED anchor.. but interestingly the Oceane doesn’t need any cumbersome “roll bar” at the back of the fluke to right itself in the anchoring position..
So your comments “ which is the main objective of the lead tip-weight in any anchor that features it.” are wrong.. and I will be interested to know who is realy spreading misinformation??
But I only suppose that the one who is spreading misinformation would be myself??
So, about the importance of the TIP weight for the initial setup, just have a look at the following figure.. if somebody will see any “misinformation” on it, please let me know..
I still pretend (and it seems so obvious to me) that to penetrate any tool, you must exert pressure on it, and heavier the tip of the tool.. better the penetration. And I consider it as an IMPORTANT factor..
“ And in fact, the high tip-weight of the Spade exists for reasons other than M Poiraud would claim ”
???? I will be very interested to learn what are these “ reasons other than M Poiraud would claim ” ???
Why is the Spade the only anchor to have such a massive block of LEAD on the tip.. and the only one to have as much as HALF the total anchor weight on the tip?
Only to improve the penetration..
“ What does set the anchor is the dynamic interaction between the anchor and the seabed once your boat starts to pull on the rode.”
Except that, if the initial setting due to the weight distribution on the anchor tip doesn’t exist.. when the boat start to pull on the rode.. the anchor will just slide on the bottom surface..
(see the previous figure)Only when the anchor has started to dig in, due to its static penetration (weight on the tip) then the dynamic penetration due to the boat pulling on the rode, will continue the penetration..
“ M Poiraud is a tiny tiny bit hypocritical here, as his Oceane anchor (the Spade's little sister) has a tip-weight measuring less than that of the Rocna!”
Obvious.. as the Oceane is like the Rocna, an UNBALASTED anchor.. but interestingly the Oceane doesn’t need any cumbersome “roll bar” at the back of the fluke to right itself in the anchoring position..
So your comments “ which is the main objective of the lead tip-weight in any anchor that features it.” are wrong.. and I will be interested to know who is realy spreading misinformation??
branko
Well-Known Member
It would be fantastic that we have such competitors " fighting" for all ship equipment. We have a credit from it!
From your posts I can read that both of you are in right.
Surely Dinamic force is much higher than static force (anchor weight ), ...but anchor with higher tip weight will penetrate to bottom better . Vertikal Force will help to better penetration during period of dragging. Am I in right?
From your posts I can read that both of you are in right.
Surely Dinamic force is much higher than static force (anchor weight ), ...but anchor with higher tip weight will penetrate to bottom better . Vertikal Force will help to better penetration during period of dragging. Am I in right?
2nd Wind
Active Member
Was lent one of these anchors in February for a presentation. Unfortunately due to time constaints was not able to show it but thoughts were :-
How and where would it stow, it seems rather bulky
Lots of flat surface area to catch waves if left on bow fitting
It did however look like a decent bit of engineering so I offered to give it a try over this season on the school boat and report back on effectiveness. This very tempting offer was refused so at £300 ish I gave it back and so look forward to seeing how it performed in the tests when the results are published.
For now sticking with trusty CQR. [Only broke one so far!!]
How and where would it stow, it seems rather bulky
Lots of flat surface area to catch waves if left on bow fitting
It did however look like a decent bit of engineering so I offered to give it a try over this season on the school boat and report back on effectiveness. This very tempting offer was refused so at £300 ish I gave it back and so look forward to seeing how it performed in the tests when the results are published.
For now sticking with trusty CQR. [Only broke one so far!!]
machurley22
Well-Known Member
Have to agree with Branko (syntax, grammar and spelling notwithstanding!) and it does my old heart good to see manufacturers arguing so passionately for the technical merits of their products. Long may it continue since it will eventually benefit even those (like myself) who use copies of the "best" anchors of their (the copies) time as acquired with our very second-hand craft. /forums/images/graemlins/grin.gif
craigsmith
Well-Known Member
Thank you Branko, although as I said I dislike getting into these debates. It is only M Poiraud's frequent attacks on his competition that necessitates it. However I assume that readers are sensible enough to take what one manufacturer with a vested interest says about any anchor with a grain of salt.
You are mostly correct, although again a difference of 10 or 20% in terms of tip-weight will make no appreciable difference to the setting performance of the anchor. Indeed the Buegel has a very low tip-weight, around 16%, yet owes its popularity in the Med to its ability to set in weed and grass, which is the most difficult to penetrate.
Then there are other issues. Apart from the presence of dedicated tip weight occupying a great deal of weight that is inefficient as I outlined in my earlier post, this weight occupies physical space that increases the profile of the fluke. This means that although the Rocna has a little less tip-weight, it is placing this weight on a sharper edge, whereas the Spade must dig in its triangular fluke.
Furthermore, it should be clear from Poiraud's little image above that my arguments about tip-weight alone setting the anchor are correct. If you examine the graphic above, one can imagine the case where forces "P" and consequently "D" are removed. "T" remains, so the graphic is saying that the tip moves down and the anchor magically sets itself? /forums/images/graemlins/confused.gif This cartoon is far too simple.
But since Poiraud again necessitates it, here is the original version of his little graphic:
Again a bit of a simplification, but it illustrates the forces really involved.
[ QUOTE ]
2ndWind said:
Was lent one of these anchors in February for a presentation. ... It did however look like a decent bit of engineering so I offered to give it a try over this season on the school boat and report back on effectiveness. This very tempting offer was refused so at £300 ish I gave it back and so look forward to seeing how it performed in the tests when the results are published.
[/ QUOTE ]
2ndwind who are you; I remember no such offer?
You are mostly correct, although again a difference of 10 or 20% in terms of tip-weight will make no appreciable difference to the setting performance of the anchor. Indeed the Buegel has a very low tip-weight, around 16%, yet owes its popularity in the Med to its ability to set in weed and grass, which is the most difficult to penetrate.
Then there are other issues. Apart from the presence of dedicated tip weight occupying a great deal of weight that is inefficient as I outlined in my earlier post, this weight occupies physical space that increases the profile of the fluke. This means that although the Rocna has a little less tip-weight, it is placing this weight on a sharper edge, whereas the Spade must dig in its triangular fluke.
Furthermore, it should be clear from Poiraud's little image above that my arguments about tip-weight alone setting the anchor are correct. If you examine the graphic above, one can imagine the case where forces "P" and consequently "D" are removed. "T" remains, so the graphic is saying that the tip moves down and the anchor magically sets itself? /forums/images/graemlins/confused.gif This cartoon is far too simple.
But since Poiraud again necessitates it, here is the original version of his little graphic:
Again a bit of a simplification, but it illustrates the forces really involved.
[ QUOTE ]
2ndWind said:
Was lent one of these anchors in February for a presentation. ... It did however look like a decent bit of engineering so I offered to give it a try over this season on the school boat and report back on effectiveness. This very tempting offer was refused so at £300 ish I gave it back and so look forward to seeing how it performed in the tests when the results are published.
[/ QUOTE ]
2ndwind who are you; I remember no such offer?
Gypsy
Well-Known Member
Why do you feel it is necessary to denigrate somebody's written English on this forum which is used by many people, including Branco, whose first language is not English. He should be congratulated for his participation.
Ray
Ray
hylass
Well-Known Member
[ QUOTE ]
If you examine the graphic above, one can imagine the case where forces "P" and consequently "D" are removed. "T" remains, so the graphic is saying that the tip moves down and the anchor magically sets itself? /forums/images/graemlins/confused.gif This cartoon is far too simple.[/ b]
[/ QUOTE ]
I suppose Craig, that you never heard about the Dor-Mor anchor??
(http://www.navbuoy.com/moorings/dor-mor-anchors.html)
This anchor penetrate only by its own weight ("T") and not by any "magical" action..
If you feel this cartoon too simple?? it is perhaps because you miss a little bit of experience?? /forums/images/graemlins/grin.gif
If you examine the graphic above, one can imagine the case where forces "P" and consequently "D" are removed. "T" remains, so the graphic is saying that the tip moves down and the anchor magically sets itself? /forums/images/graemlins/confused.gif This cartoon is far too simple.[/ b]
[/ QUOTE ]
I suppose Craig, that you never heard about the Dor-Mor anchor??
(http://www.navbuoy.com/moorings/dor-mor-anchors.html)
This anchor penetrate only by its own weight ("T") and not by any "magical" action..
If you feel this cartoon too simple?? it is perhaps because you miss a little bit of experience?? /forums/images/graemlins/grin.gif
branko
Well-Known Member
....... "Branko (syntax, grammar and spelling notwithstanding!)"
Sorry for my syntax, grammar and spelling faults. It seems that I spent too much time in my life to learn another 3 languages I speak (with faults also!). /forums/images/graemlins/confused.gif
Sorry for my syntax, grammar and spelling faults. It seems that I spent too much time in my life to learn another 3 languages I speak (with faults also!). /forums/images/graemlins/confused.gif
2nd Wind
Active Member
Sorry for the confusion Craig.
The anchor was lent by a chandlery and the offer made to them so you are right to question me. The offer still stands though as the quick look I had does seem to indicate that the Rocna will do what it says on the tin, as it were.
The anchor was lent by a chandlery and the offer made to them so you are right to question me. The offer still stands though as the quick look I had does seem to indicate that the Rocna will do what it says on the tin, as it were.
hylass
Well-Known Member
Since several thousands of years, poeple have trust on WEIGHT to digg in their anchors...
...but your are the FIRST to pretend that " the dedicated tip weight occupying a great deal of weight that is inefficient "...
Congratulation for this new and very interesting theory..
(or is it again misinformation?? )
...but your are the FIRST to pretend that " the dedicated tip weight occupying a great deal of weight that is inefficient "...
Congratulation for this new and very interesting theory..
(or is it again misinformation?? )
machurley22
Well-Known Member
Absolutely no criticism implied Branko, and unreserved apologies if it came over as such. If you look at my history you'll see that I frequently post in gibberese (or Scots as I like to think it) and am therefore in no position to lecture anyone else. The remark was supposed to be a humourous aside (hence brackets and exclamation mark!) and was a result of posting while pished.
Phoenix of Hamble
Well-Known Member
Hylas,
That arguments a bit thin isn't it?....... for sure that picture shows an anchor where weight is important..... its at the same time that people also used candles to light their navigation lamps........ times have moved on a little...
FWIW.... I have a CQR, so no vested interest here..... just interested in teh science behind what works and what doesn't
That arguments a bit thin isn't it?....... for sure that picture shows an anchor where weight is important..... its at the same time that people also used candles to light their navigation lamps........ times have moved on a little...
FWIW.... I have a CQR, so no vested interest here..... just interested in teh science behind what works and what doesn't
