sighmoon
Well-Known Member
That's not going to change - a bad review cost Yachting World £1.4m in a libel case.
Misleading stability
- Thread starter Polux
- Start date
That's not going to change - a bad review cost Yachting World £1.4m in a libel case.
Seajet
...
In a perfect or even vagueley adequate world, one might hope that someone handing over their boat for a review is prepared to take any critiscm on the chin; at this rate the magazines may just as well run larger advert's or reproduce brochures.
doug748
Well-Known Member
"What a sham modern yachting is. Seems to me everyone is in bed together scratching each others backs. All wrapped up by a group of EUcrats who are happy to write anything for their jobs. Further compounded by the numbers that have bought in to the modern system and it has got to be perpetuated to ensure their investment is acceptably secure.
Wouldn't it be lovely to read some indepth review of a product that was comprehensive in its testing and was related to the experince of the testers. Seems to me most articles are written with only the positive and you have to guess the spaces."
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"I think you will find that over the years the subject has been well covered by YM and YW in particular and all the issue raised by the OP have come up. Also the RYA has regularly published updates on developments.
The reality is that for most people this is a non-issue"
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Two conflicting views there.
I must admit that I have never been captivated by the coverage of the topic in the Yachting Press.
It seems rum to me that manufacturers can get away with not publishing data - and the DIY nature of the testing regime.
Wouldn't it be lovely to read some indepth review of a product that was comprehensive in its testing and was related to the experince of the testers. Seems to me most articles are written with only the positive and you have to guess the spaces."
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"I think you will find that over the years the subject has been well covered by YM and YW in particular and all the issue raised by the OP have come up. Also the RYA has regularly published updates on developments.
The reality is that for most people this is a non-issue"
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Two conflicting views there.
I must admit that I have never been captivated by the coverage of the topic in the Yachting Press.
It seems rum to me that manufacturers can get away with not publishing data - and the DIY nature of the testing regime.
Tranona
Well-Known Member
You have to go back to the late 90's when the RCD came in. Both mags -and the others to a lesser extent ran a series of articles on both the standards and their implementation. There were also articles of a quite technical nature on stability. The OPs observations are not new - right from the start there were concerns about the robustness of the standards asnd measurement methodology - indeed from recollection the RCD was introduced when some of the proposed standards were still in draft form.
The reason I suggest it is a non-issue is that there have been very few cases of defective boats because of either a failure to meet the standards or the standards being inadequate. Individuals can huff and puff about things they see as not being right, but that is a long way from justifying change. There has to be clear evidence that wrongs are being done to generate enough political will to tackle whatever the problem is (or is seen to be).
This argument reminds me somewhat of the concern about the mismatch between fuel consumption figures fom the standard test and what is achieved in practice - the difference between stabilty calculated according to a formula in as designed conditions and how a boat behaves in use.
If there is a case for change then it must be based on a clear articulation of where the deficiencies lie (in the standard, in the methodology or the enforcement) - what the negative impact is and a firm proposal for improvement. At present all that seems to be apparent is some concern about deficiencies, but no clear articulation of the impact or new proposals.
The reason I suggest it is a non-issue is that there have been very few cases of defective boats because of either a failure to meet the standards or the standards being inadequate. Individuals can huff and puff about things they see as not being right, but that is a long way from justifying change. There has to be clear evidence that wrongs are being done to generate enough political will to tackle whatever the problem is (or is seen to be).
This argument reminds me somewhat of the concern about the mismatch between fuel consumption figures fom the standard test and what is achieved in practice - the difference between stabilty calculated according to a formula in as designed conditions and how a boat behaves in use.
If there is a case for change then it must be based on a clear articulation of where the deficiencies lie (in the standard, in the methodology or the enforcement) - what the negative impact is and a firm proposal for improvement. At present all that seems to be apparent is some concern about deficiencies, but no clear articulation of the impact or new proposals.
doug748
Well-Known Member
Aye good point, why have the truth when you can a load of old bull.
The argument reminds me of something too. Vested interest. Ah, I still miss the scare stories about cigarettes.
"There we have it, British American Tobacco have done their own research and there is nothing to worry about."
"Fancy a smoke" "Don't mind if I do"
Tranona
Well-Known Member
I think you have to live in the real world - which for the European boat building business is survival at the moment.
For all the concerns from individuals about the inadequacies of the standards, I have yet to see any credible argument of harmful consequences or viable alternative. Seems to me that much of the argument is that modern boats are not like old boats and nobody makes boats like old boats anymore - which is hardly surprising because many old boats simply would not meet modern standards.
As to "truths" there are so many to choose from, which do you want? Like most people I suspect you would choose the ones that match your prejudices most closely!
For all the concerns from individuals about the inadequacies of the standards, I have yet to see any credible argument of harmful consequences or viable alternative. Seems to me that much of the argument is that modern boats are not like old boats and nobody makes boats like old boats anymore - which is hardly surprising because many old boats simply would not meet modern standards.
As to "truths" there are so many to choose from, which do you want? Like most people I suspect you would choose the ones that match your prejudices most closely!
Twister_Ken
Well-Known Member
OTOH, the RCD stability standards have yet to be real world tested en-masse with the equivalent of a Fastnet storm. When that day comes it won't be the Eurocrats who are drowned, unfortunately.
doug748
Well-Known Member
Polux
Well-Known Member
This is not about inadequacies of the standards. This is about inadequacies on the global criteria to generate stability curves that generate wrong assesments about a given boat.
This is about all stability curves not being made the same way (contrary of what happens to the ones needed to certify the same boat for ocean racing (ORC) - they don't accept the ones provided by the builders).
This is about this knowledge being public on the techinical levell and nobody doing anything to levell the play.
This is about misleading data that is given to the consumers, agravated because not all manufacturers give misleading data and the ones that give similar information to the one that is obtained by the ORC methodology about the stability performance of their boats, have the consumers thinking their boats perform worse than the ones that offer pimped up performance. We are not talking about 2 or 3º, we are talking about a 10º diference on the AVS and that's huge, so huge that there would be a lot of boats that would not have been aproved as class A boats if the stability data was acessed using the ORC methodology that is the only one based on real inclining experiences with the boat on the water.
This is not about the inadequacies of the standards, this is about the right that the consumers have to have correct and significant data (obtained the same way for all) about the stability of the boat they are going to buy.
Regards
Manuel
Tranona
Well-Known Member
Tranona
Well-Known Member
Boats have been built to these standards for 12 or more years now (and many earlier boats were built to similar designs) and have been in operation all over the world. We have yet to see a rash of founderings because of lack of stability! Almost all losses of yachts through foundering are racing craft which do not have comply. And remember most of the Fastnet yachts were designed to the now discontinued IOR rules.
Polux
Well-Known Member
Let me specify:
red a divergence equal or superior to 8º, Brown, between 5 and 8, Green, 5 or less than 5.
First the ORC AVS, taken with an inclining experiment, last the AVS provider by the builder or the Designer and computer made)
X43 - 115,3 - 119, Arcona 43 -115,3 - 125; Elan 410 - 120,2 - 127; Elan 340 -116,8 - 132; Faurby 424 - 110,3 -118;; Dufour 40 - 109,9 - 122; First 36,7 - 113,3 - 126; First 40,7 - 114,6 - 126; First 44,7 - 107,6 - 130; Dehler 39 -117,6 -118; Hanse 430 - 115,4 -109;; Oceanis 423 - 110,5 -119; Oceanis 473 - 108,5 - 119; ; Swan 56 - 122,0 - 127; Sun Odyssey 49 - 110,1 - 120.
The data (AVS) was taken from the ORC international certificates (net) and from the RYA information on stability, from stability curves (provided by the manufacturers) published in magazines and from stability curves that the manufacturers display on their sites.
Regards
Manuel
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Ubergeekian
Well-Known Member
Am I right in thinking that the ORC AVS is not actually found experimentally? As I understand it they do a load vs heel test for a fairly small angle and then use that to adjust the mathematical model which predicts AVS.
It would be very interesting to know how the experimental results for small angles compare with manufacturers' predictions.
Seajet
...
Uber,
completely agree, seems unlikely such tests involve inverting and pretty much trashing the boats !
Also, I'd be really surprised if the mathematical models include all the stores and kit - and indeed crew - a boat going any distance will have on board ?
As ubergeekian and others will know, when a new aircraft comes along there are usually several development examples, one of which is literally tested to destruction, being subjected to physical loadings and stress to simulate the anticipated life of the aircraft.
Seems to me any boat manufacturer seeking to have their product seriously portrayed as 'offshore' should submit an example for controlled inversion tests, complete with some sort of agreed standard kit / stores fit-out ?
completely agree, seems unlikely such tests involve inverting and pretty much trashing the boats !
Also, I'd be really surprised if the mathematical models include all the stores and kit - and indeed crew - a boat going any distance will have on board ?
As ubergeekian and others will know, when a new aircraft comes along there are usually several development examples, one of which is literally tested to destruction, being subjected to physical loadings and stress to simulate the anticipated life of the aircraft.
Seems to me any boat manufacturer seeking to have their product seriously portrayed as 'offshore' should submit an example for controlled inversion tests, complete with some sort of agreed standard kit / stores fit-out ?
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Ubergeekian
Well-Known Member
I understand that whether windows and hatch are open or not has a huge effect. For wild conditions it may be more accurate to assume that they would be closed: for an unexpected gust that they are open.
Here's the 787 wing being broken
And here - sorry, rather large downloads - are inner and outer views of a DG glider wing tested to destruction. The tip deflections are pretty impressive!
Tranona
Well-Known Member
To have some understanding as to why this happens perhaps you need to go back to basics. AVS is an artificial construct that is intended to represent a phenomenom that is dynamic and complex. It does not exist independently, but only as a calculation of the relationships among a number of variables. For convenience these measurements are turned into a single number for comparison. It has no other real meaning. It is clear, therefore that different methods of calculating a representation of something that is not in itself absolute will result in different outcomes. The numbers themselves will be PRECISE if the numerical manipulation is correct, but they will not necessarily be an ACCURATE representation of what you are trying to measure.
You may well be right that one particular method may be more accurate than another but it will still be only an estimated representation that might be just as misleading - but at a different numerical level.
Debate about the value of numbers as representations of constructed phenomena is (or should be) a major topic in any serious Research Methods course. It certainly was when I taught the subject. Always very illuminating to see peoples' reactions when they are first faced with the proposition that the meanings of numbers can be just as variable as that of words - particularly those from an engineering or science background wanting to become managers! Many recognised the significance of my allocated car parking space being numbered 42.
I am reminded of this dilemma as I am currently marking exam papers where one of the questions requires the calculation of the value of a business using 4 different methods - but all based on the same raw data. The calculations are relatively simple, but each method gives a different answer. Half of the marks in the question are for explaining what they mean and why they are different.
Which brings me onto the second point which is to explore the value of using a single value as a determinant of category. In my exam paper, 1 mark can be the difference between a pass and a fail. One mark can be the difference between a First Class degree and a 2:1. Tiny differences in one (dodgy) measure makes a huge difference in outcome. One degree difference in calculated AVS moves a boat from category B to Category A (all other things being equal). Given the consquences of categorisation is it any wonder that a huge amount of effort goes into maximising AVS at the margins? In just the same way that my judgement on whether giving a mark to a marginal answer will be irrelevant for a student that already has enough marks to pass the abrbitrary pass level, or could be the difference between a pass or fail for another student.
So the "misleading" is not in the actions of the designer (in the case of boats) or the marker (in the case of an examination), but the belief that numbers are a neutral and accurate representation. This comes about because our society is obsessed with measuring things and placing them into categories as a way of helping people make sense of complex issues and choices. It has the added advantage when, as in this case, the numbers are "official" of removing personal responsibility for a decision.
So I can now go back to my marking determined to be as neutral as I can when I decide to award a mark - or not!
Seajet
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Tranona,
I agree completely that if one were to come up with a simple figure - and the AVS may well be an example of this, even if all boats were tested to the same parameters; I think the whole point the OP was making is that they are not, so it is even more meaningless - it would be of little use.
If a figure was given, "this is an 8 rated boat" it would be useless to a potential buyer, maybe an agreed testing regime could provide a short report, ideally in a way that is intelligible to novice and seasoned veteran alike ?
I agree completely that if one were to come up with a simple figure - and the AVS may well be an example of this, even if all boats were tested to the same parameters; I think the whole point the OP was making is that they are not, so it is even more meaningless - it would be of little use.
If a figure was given, "this is an 8 rated boat" it would be useless to a potential buyer, maybe an agreed testing regime could provide a short report, ideally in a way that is intelligible to novice and seasoned veteran alike ?
Tranona
Well-Known Member
Please read what I said. Using a different measure may improve comparison between boats, and may be a more accurate representation but might be just as misleading.
You are just falling into the same trap believing that there is a "simple" way of representing complex things. There isn't because it has to be qualified by such words as "using standard XYZ....". You see it on fridge doors, energy reports on houses, car windshields and so on. All simplifications and open to interpretation, never mind the "manipulation" that goes on before you see it!
Seajet
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I did read it, and am used to such things having worked in aircraft instrument calibration !
I'd say if using different testing methods, they should be at least inter-related and each in their area apply to similar types of boat.
I certainly never thought or said a subject which is complex in itself and subject to financial and no doubt political influence would be easy !
An example of school / examiner types assuming no-one else has a brain while wishing to display theirs, again ?!
I'd say if using different testing methods, they should be at least inter-related and each in their area apply to similar types of boat.
I certainly never thought or said a subject which is complex in itself and subject to financial and no doubt political influence would be easy !
An example of school / examiner types assuming no-one else has a brain while wishing to display theirs, again ?!
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Tranona
Well-Known Member
Not sure why you are making that statement. I make no assumptions - just trying to explain things as I see them. You either accept of reject as you see fit.
However, your suggestion is no different from the existing position. Boats have to meet a number of standards on design and construction, a report provided and a declaration made. Then it is allocated a category to make it "simple". The only issue that the OP raises is whether one of the measures is reliable. And all I am saying it is not necessarily more or less reliable because the whole idea of a single measure representing a complex phenomenom is fraught with problems - some of which I have mentioned. However, if you really want to I can go much deeper into the topic, but not sure it would add anything, which is why I kept it at this level.
