Post deleted by danfoley

[extravert]

Re: Liver Lilied Sailors

I agree with you although I was not brave enough to 'come out' in my opinions on the RCD. Looking at it the other way I would be surprised if there were no standards for products like sea going boats for which proper design and construction has such a direct bearing on safety.

I agree with everyone that good seamanship also has an important part to play, but I also want to be sure that a boat has been designed and built right as well.

Look at other vehicles like cars. Because there are standards we can be pretty sure that a new vehicle has been built properly. (Brakes work. Seatbelts work. Wheels stay attached). We all still know though that driving stupidly is unsafe, even in the best cars. However, if they were allowed to be built unsafe, then everyone would be at risk, including the best drivers. Looking at a new car in a showroom, I can't really tell myself if it has been built properly. I don't suppose most people (including me) can tell for all boats either.

 

[Viking]

Re: Liver Lilied Sailors?

I dont think anyone said that the Oceanis 390 was a bad boat. It became the 'wrong' boat to be in the extrame weather 'Ocean Madam' found herself in, also it may have been handle badly or incorrectly.

Most of us take 'risks' went sailing, Sailing on the seas is a risk. But usely the 'risks' we take are measured and manageable, with safety for ourselves and loved ones in mind, along with the risks others may have to take who may have to come to our aid.

I think, the prolification of boats, even from the days of the famous cruising folk who have been our pathfinders. Some measure to help people judge what type of boat is most suitable for the propose they intent to use it, is no bad thing. Saves time looking at the wrong boat.

Lily livered? You would stop the idiot who jumps in a 'bathtub' and set off across the Alantic. In fact, would you do it? and if you wouldnt, do you class yourself as 'Lily livered' because thats what your saying.

 

[Mirelle]

Re: Steady on!

My last brush with F9, in the North Sea a few years ago, was caused by skipper (the undersigned) getting bored with waiting on weather and shoving off into the first suitable break in the weather, with a forecast F6 which brewed up very promptly into an actual 9. Had I not been in such a tearing hurry, due to running out of holiday, I would have listened to the forecast for western areas and realised that was likely to happen, but....anyway, we tested the cockpit drains a bit.

Wanderer 3 has a selfdraining cockpit; Wanderer 2 had a cockpit that could be made watertight, but was not self draining. Did'nt realise Taliesin's hatch is off centre - so were the forehatch and often the skylight on Bristol Channel Pilot Cutters (the real ones).

I took the lifelines off last year, recognising belatedly that they were more likely to speed the passing guest by catching him/her at the back of their knees, to make recovery more difficult and to cause one to go OB when boarding from a dinghy. Have'nt missed them.

My heavy weather sailing skills are brilliant in fine weather and even better when behind a keyboard, but they deteriorate fast when it gets nasty ("do I really need to reef again / change down to the storm jib / hand the mainsail" etc.)!

 

[AndrewB]

Good posting.

And bound to stimulate reaction.

The main concern about the RCD has not been with standards or safety, but with the protectionist aspect, creating a playing field which favoured the largest builders, and created obstacles to buying cheaply outside Europe.

Even so, there has still been uneasiness about the standards that the RCD de facto establishes. Build standards are not new - before there was the highly respected Lloyds 100A1 for example.

It is not that RCD standards are inadequate. But when the RCD was announced, the fear was that it would create a situation where builders had an incentive would 'build down' to the standard. A bit like the type of rule cheating that we were already accustomed to with IOR racing, designs built to attempting to find loopholes in the standard, though this time in the interests of cutting costs rather than winning races.

And that has happened. The yachts are built and equipped to a reasonable standard, as you say. But RCD does not specify such things as hull strength in any rigorous way. Nor is it concerned with overall design. Though a boat build to cat. A standards may be capable of coping with very heavy conditions, specially in the hands of a strong crew, that does not necessarily make it suitable for use where such conditions must be routinely expected, as in short-handed ocean cruising. But the marketing guys have glossed over that distinction, particularly with inexperienced buyers.

The main consequence of the Ocean Madam case has been to address the concern that yacht purchasers did not appreciate the stability implications of the RCD. Hence the effort to clarify this with STIX numbers (which must now be presented with every new yacht), the RYA booklet on stability, advice in the yachting press, etc. So, hopefully, more people do not find themself in the same position as Stingo.

My guess is that sooner or later similar steps will be taken with respect of (a) strength and (b) durability issues in economy yacht construction. Cases like the yacht lost due to the rudder failure in the recent ARC will serve to focus on the former.

 

[Guest]

Re: Me neither.

Despite having worked with them for what seems like 400 years, I still don't understand computers!

At work, going through the office internet link, it didn't show up.

Now I'm back at home it does!

Well there's a funny thing.

Mark

and what a lovely looking boat it is too

 

[Jacket]

Re: Good posting.

The only point I'd argue about is your statement that the RCD will cause builders to 'build down' to the standard. Sure, some may do that, but if the RCD wasn't there they'd build down to an even lower level.

Boat builders of that mentality are not trying to cheat a rule just for the sake of it, but to produce the cheapest boat that will sell (even if it does fall appart a few years later). The RCD may not be perfect, but at least it goes some way to protecting the public from boats that are unsafe due to cost cutting by the builder.

 

[extravert]

Re: Good posting.

I was under the impression that it was some of the non-European foreign builders who pressed for a Europe wide standard in the first place. They had difficulty meeting a wide range of different rules for different countries. This hardly backs up your protectionist claim. Also for our small volume builders hoping to export to other European countries, doesn't it make it easier for them as well; a single well known standard?

As for building down to a standard, I would rather that than building to no standard at all, and the non-expert purchaser being completely in the dark as to what standards a boat was built to. If you want to see some truly awful US boat design and construction to no standards, have a look at David Pascoe's Yacht Survey site.

You say hull strength is not stipulated rigorously in the RCD. In practice does that matter too much? It's not often hull failures that is causing loss of life. Like in Ocean Madam's case, it's poor stability, loss of water-tight integrity and inappropriate use that is causing fatalities. When did someone last die on a BenJanBav because of a catastrophic hull failure?

 

[Mirelle]

Not so sure

In any field, certainly in mine (merchant shipping) attempts to thus "level the playing field" always do result in "building down to" the lowest common denominator, and in general ship designs are now optimised ("over-optimised", according to a recent President of the RINA) at that point, with any superfluous strength eliminated. In series production, this is big bucks.

Take, for example, Stingo's conversation with Beneteau about adding lead to his keel - they said he could certainly add 200kg but did not want to put that in writing.

We can guess why that might be, of course - the strength of the keel/hull joint and the associated floors have been calculated on the basis of the righting lever exerted by the designed keel.

Conversely, take any design of 30-40 years ago and you could add half a ton to the keel without a second thought.

 

[Jacket]

Re: Not so sure

In any market, there are two types of builders, and people always seem to forget this.

There are those who are out to build high quality products. For these people standards such as the RCD are largely irrelevant as there boats will naturally always meet or exceed what is expected from the standards.

The other sort are those out to make as much money as possible (and no, I'm not saying that this is a bad thing). However this does require building down as low as possible. A standard, as I said in an earlier post, does not cause people to build down. It does something very different- it inserts a level which stops them building as low as they would otherwise do.

Yes, this can fall appart if the standards are set too low, as builders could build to the rule and when a boat fails they could claim it wasn't their fault as they'd met the rule. However, standards are rarely set too low (normally they're made increadibly conservative).

Of course tankers are built down to a level- oil companies are out to make money after all. Remove the standard, and I bet the tankers would be built to an even lower level. I remember reading that at the turn of the last century many ships were built to survive 10 voyages- this was enough to pay of the cost of construction. If they survived more voyages, this was your profit. However, many didn't survive much beyond 10 voyages and broke up at sea. At least standards mean we are in a better situation than that!

As for your comment about older boats being able to take extra weight in the keel. This isn't because boats were better built in those days. It was just a case of design methods not being as good in those days. Boats were still built with as little material as possible (cheaper and produced a faster boat) but with no real way of estimating the stresses on a boats structure, you had to err towards conservatism and so boats were usually overbuilt.

Nowadays, with improved design tools (Finite element analysis and the like) and with more reliable materials (one batch of GRP is much like the next, unlike wood) it is possible to design in the strength more accurately. after all there is no need to design a boat stronger than is required, as it costs more, adds extra weight (and also a thicker hull does not necessarily mean a stronger boat).

Of course Beneteau wouldn't put anything in writing. The boat wasn't designed to take more weight in the keel, so without going back through all the original design calcs there's no way of being sure. I'll bet the builders of boats built 30-40 years ago wouldn't have put anything in writing either (at least they wouldn't if they lived in these days of everyone sueing everyone else).

 

[Mirelle]

Still not sure

in consumer durables like yachts and cars there is a luxury market. In ships and prsumably bridges there is not (except for the Millenium bridge, maybe?) so there is only one type of builder, who in shipping at least is not making loadsamoney but cutting every cent off his price in order to offer what seems the same product slightly cheaper, and thereby stay in business.

You see optimisation through finite element analysis as a good thing; conversely it gives me kittens. My point about Beneteau's response was that 200kg is neither here nor there as a weight of ballast, i.e. the design is well optimised, as indeed one would expect from Europe's largest production boat builder.

There is a story about one of the early astronauts being asked what he thought about, strapped to his couch on top of hundreds of tons of highly inflammable fuel and oxygen, as he prepared to blast off. The reply was, "Every component of this thing has been built by the lowest price contractor!"

Rather a lot of people have stood on the bridge of a fully laden Capesize bulk carrier with 160,000 tons of iron ore aboard, heading into a North Atlantic storm, and thought "Every component of this ship has been precisely optimised by finite element analysis!"

 

[Jacket]

Re: Still not sure

I have to admit that you're argument about tankers is confusing me. You agree that tankers will always be built as cheaply as possible, yet don't seem to like the standards that prevent them being built unsafe.

OK, you may think that the standards are set too low (too small a safety margin) but thats not really an arguement against having standards.

As for optimisation, I probably didn't explain myself very well. In real structures its not possible to know what the REAL stresses in that structure are. Instead we use the "upper bound method" in which the stresses you calculate as being present in the structure are higher than the stresses that really are in the structure. So if you design to these calculated stresses the structures strong enough, as the real forces are less than this.

The problem comes in that you don't know by how much you've overestimated the stresses in the structure. Older less accurate methods overestimated the stresses by (say) 5 to 100%. Modern, improved methods overestimate by (say) 5 to 20%.

As failure of a structure (boat, tanker etc) fails when the weakest part fails, both the old and new design methods are just as safe, as the "weakest" elements are both designed with a 5% margin of safety.


Another thoughts just occured to me. Could it be argued that the fact that yachts are arguably getting weaker is nothing to do with the RCD or new design methods but because yachtbuilding companies are getting bigger? In the old days of small builders, it wasn't economically feasible to go into detailed strength calculations, and so you just added lots of material to the design in the hope that it is strong enough. This is worse than building a design down to a limit, as no matter how much material you add to a design, unless you add it in the right place stress concentrations can still occur.

Think how many secondhand boat reviews on older boats you've read where there's been comments along the lines of "on many boats the chainplates/ keel floors/ rudders have had to be strengthened by owners after a few years." Bet this wouldn't have happened if proper strength analysis had been carried out.

 

[qsiv]

Re: Liver Lilied Sailors

Just for a moment I thought you were being cynical, but maybe not.

I do have concerns that nowhere in the RCD does it take any account of the 2nd moment of inertia of the direction correction armature (historically known as the tiller). It concerns me as such armatures could be made of a wide range of materials some of which could, under certain extreme seastates fail in a number of ways thus making the said armature inoperable. What is worse is that they completely fail to take account of the varying moisture content of these devices, nor of the degradation due to exposure to either ultraviolet rays or to brine. Some of these devices have aftermarket alterations that could also render hem as being unfit for purpose and the alterer liable to prosecution.

This namby pamby nonsense is quite awful. My father was always of the opinion that certain foreigners, who had never got over coming second at Copenhagen, Trafalgar, Waterloo, Tobruk and other locations, had resolved never to confront but simply legislate us out of existence. Naturally I think he is wrong and they are all jolly fine chaps, and we should commend their efforts to protect us from ourselves.

 

[Mirelle]

Re: Still not sure

Your last point - that improved optimisation is the result of a few large builders rather than many small ones - is certainly right. Large builders can use the economies of scale presented by optimisation. They invest in the calculations needed to achieve it because they will save this in materials cost over a long production run.

Now, let me try and explain the shipping case to a bridge builder (this is quite interesting!)

What has happened with us has been that we have had minimum standards for a very long time. They are defined by two bodies of rules - the international safety rules established by international conventions - eg the Load Line Convention says that hatch covers must withstand 1.75 metres water head - and the detailed Rules of the Classification Societies. To a considerable extent, the latter are the detailed means of interpretation of the former.

There used to be a third set of rules - those established by national governments - but these have been "competed out" - eg Britain used to have higher specifications, but this just meant no more British ships, so they have been repealed.

There has been terrific competition for market share between the Class Societies. This caused what one might term competitive rule making, with progressive reductions in scantlings. The societies are now getting a grip on this, but we have seen a tremendous reduction in scantlings, and in some cases (see below!) the results have been unhappy.

There is one way to find out what the real stesses in a real structure are. That is when it breaks in service. When seven year old bulk carriers started disappearing without trace, i.e. breaking up so fast that no distress message could be sent, just a few years ago, we realised that we had taken optimisation of structures too far, because the only possible cause was massive sudden structral failure. When a few ships broke up slowly enough for the odd survivor to be picked up, and wrecks were looked at, we found that we were right in our diagnosis. Unfortunately rather a lot of people (about a thousand) are now dead, in order to prove that many designers had under-estimated the stresses in their structures.

Oddly enough tankers are much less highly stressed, particularly the "bad" old single skin ones, which are longitudinally framed on the Isherwood system with stringers and ring frames, and divided into an egg box structure with two longitudinal bulkheads and many transverse ones and a structurally complete deck. Container ships, which have not really got a top to their girder in the form of a deck, and bulk carriers, with wide hatch openings and very dense cargoes, are far more stressed, although we have some interesting problems with the double hull tankers too.

Progressive optimisation, driven my cost reduction, continues until widespread failure occurs - I will hazard a guess that bridge design is a far more conservative business than ship design is, structurally speaking, because a bridge failure might kill a lot of voters, whilsy a ship failure just kills the crew.

Old style yacht design like old style ship design was built upon masses of experience - empirical data assembled and hoarded. "We know this works". Hundreds of thousands of simple carvel planked hulls were built, all remarkably similar because that was what worked. Simple methods for simple men.

Enter finite element analysis and cost reduction and things change fast.

In yachts we have seen cases of keels falling off, being driven up through the hull on grounding, etc. Not many, yet, but watch this space....

 

[AndrewB]

Re: Good posting.

To answer your points in turn:

1) I believe you are correct that some of non-EU manufacturers were in favour of the RCD, mainly because independent standards were evolving separately in each European country and it would have been a nightmare designing yachts to satisfy all of them. But only a few of the largest overseas companies have found it worth their while to make their yachts compliant with the RCD. The others we can no longer buy, neither new nor second hand, unless we are prepared to foot the cost of having them tested. So the RCD creates obstacles. Maybe it is just coincidence that the RCD was introduced at a time when second-hand yachts in particular were significantly cheaper overseas.

2) The criticisms on David Pascoe's site regarding cored hull construction could apply with equal force to the economy boats currently contructed under RCD. Indeed, Hunter/Legend in particular, one of the first US builders to comply with RCD, have been regularly criticised for hull quality in the US.

I am convinced that the average build quality of production UK yachts prior to the RCD was much greater than that of the economy yachts being sold today. Indeed, in the wake of the Fastnet Disaster enquiry, they were over-engineered to sell to a particularly cautious market. This is part of the reason for the demise of the UK industry under RCD.

3) Hull strength is very valuable for ocean cruising, particularly in areas of coral. A self-sufficient cruising yacht should be able to survive ramming an underwater object at reasonable speed, an exposed grounding in moderate conditions, collisions with other yachts and fishing boats, and falling off the tops of waves in steep seas.

Sudden failures occur more commonly in keel joints and rudders, rather than in the hull itself. There is no shortage of examples. These no longer cause loss of life because the communications revolution has made rescue services infinitely better than in the past. But we cannot be sure as there are still regular reports of ocean cruising yachts having vanished without explanation.

 

[gjeffery]

Re: Steady on!

My post could not have been clear with regard to mooring and the provision of a samson post on a boat that is RCD compliant. My reference to the RCD was partly cynical, suggesting a tendency to design down to what is required by the RCD - rather than to provide solutions that are the best available.

I have two concerns. Firstly, if an RCD coded boat is modified in a material way, does this void the coding, and is there an issue when the boat is subsequently sold? I don't know the answer, but I am happy to query points that draw attention to the very lose way in which the Recreational Craft Regulations are written.

Secondly, if a modification, however well designed fails in proper use then liability could be attributed to the person who made the modification, and who has a duty of care. If the RCD compliant design fails then liability should be deflected to the agency who certified the design.

Finally, the designer presumably made use of an FEA model to optimise the hull structure, and the stresses induced within the hull. It may be simplistic, without knowledge of the design processes adopted, to assume that such structual elements may be bolted directly to a GRP deck with only local reinforcement.

 

[Jacket]

Re: Still not sure

As far as I can see, its still a case of the design standards being set too low, rather than the standards making people build ships weaker than they would otherwise do.

As for modern design methods making designs less safe, it doesn't. It makes them safer in that you have a more accurate idea of the forces for which to design to. What appears to be changing is that the safety factors that are then added to the calculated forces are being reduced. These safety factors are there, amoung other reasons, to allow for the fact that the ship will get weaker with time- corrosion, fatigue cracking, holes cut in bulkheads to allow extra equipment to be fitted, and so on.

From what you say (7-year old ships sinking) it does sound like a case of reduced safety factors being the problem. If it was a flaw with the basic design method, the ship would break up the very first time it experienced bad weather. Failure 7 years in sounds like fatige or corrosion problems, which are due to the reduced safety factors.

 

[pugwash]

Who needs a double hull anyway?

I'm not sure you're right that ships are invariably built to the lowest and cheapest spec. Plenty of well-found ships are built to higher specs because the owner can't afford the luxury of building cheaper -- the penalties of a calamity being so enormous. A lot of the well-built tankers with single hulls could outlast the new double-hull tankers. WHen the latter get old, many professionals believe they will be more dangerous than single-hull ships because there is no way of de-gassing the many inaccessible spaces between the hulls. A senior pilot and chairman of a sea-safety group said to me only today: "These ships will be floating bombs." We'll see.

 

[Mirelle]

Precisely

No-one is in any doubt that reduced safety factors were the problem, and that fatigue and corrosion were to blame. They usually are! Extensive and inappropriate use of higher tensile steels, reduced scantlings due to this and to over-reliance on improved paint systems, under-estimation of cyclic stress reversals, modification of detail design to permit more automated construction and so on.

Now the real point is that all this was and is justfied with the words, "....but now, using FEA, we can....."

Shipyard detail books built up over, in some cases, a century or more of actual experience were chucked out wholesale....and the proces is still going on. I can think of at least one firm of naval architects with a staff of over 20 who are solely employed in optimisation to reduce steelweight whilst still complying with the Rules.

 

[Mirelle]

Not plenty

a handful of ships are built to higher specifications. I'm in a position to know roughly how many, and perhaps even to name most of the owners who order such ships. The vast majority of "commodity" ships are not.

All yards start with a basic spec. pared to the bone. Everything on top of that is an extra. How much more you get depends partly on where you are, partly on who you are, and of course always on how much you are willing to pay.

 

[Col]

Re: Help please

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