Keeping our pants up, when a new design goes wrong

Michael, maybe it is studied by those who are into ocean engineering. I know that they are the ones who plotted where rouges waves are more likely to be and the average wave heights that can be found anywhere the sea. It is a branch of Naval Architecture or probably a masteral or doctorate degree.

 

Dont know. The IMOCA 60 Cheminees Poujoulat just broke in half.

I would think that this boat has superb engineering and build.

 

Interesting replies. All is never quite as it seems..

The boat i meant was indeed Team Phillips . Got it mixed up. However the media reports kept on saying Irens, maybe because he is from Cornwall. I should have known better than trust anything said on tv.

Here is a link to the boat;
http://www.telegraph.co.uk/sport/2994396/Yachting-Goss-dream-dashed-by-cruel-blow.html

 

Ilan, so that means commercial boats which pass class standards are "risk free" for the ME, am i right?

Lawsuits in the US makes one think it may be worth being picky about US clients..

With the Team Phillips boat, my impression is that there was no realistic way of creating such a high load structure at that scale. Scaling laws determine that as dimensions go up it gets harder and harder to manage the forces involved. That design would have been fine at 12 M say (~1/3 scale) not at that size. The fact that as soon as they fixed the bow issue the problems moved to the mast bases seems to confirm my idea on that.
I think also there may have been some serious underestimation of the effects due to converging/diverging fluid flow lines when sailing over waves, which ended up pulling the bows apart or collapsing them towards each other.

 

Michael, the last (old) news I got from France mentioned that Nigel Irens was working on a new very exciting project. A google search gives a site under construction and a lot of references. He works often with Cabanel.

The sinking of Cheminees Poujoulat is very recent and little is known. I do not know the NA but the Swiss builder is a very able one... The storm Dirk was strong and it seems that the sea was enormous. What they were doing there? The storm was announced long before.
The problem with these monohulls is they have a lot of "holes" in the hull for the daggerboards and keel, add a low freeboard on a wide boat with a light deck and the hull can "explode" by failing of the deck in compression or rupture of the bottom of the hull in tension. The openings give the start of the rupture, often at one corner, where the stresses are higher.
The tri Laiteries Mont St Michel lost its bow in late 80's because a square opening in the deck. The sistership Fujicolor never had problems because we made a round opening (deck hatch) with some UD carbon.
Remember the plane Comet failing in the 50's because of its square windows. Beware of the corners in a structure...

Team Philips had several flaws in design and badly built in a barn, so its fate was announced long before. Any NE knowing composites could tell that after short calculations made by hand on a sheet of paper...not enough inertia for the bows. A part Parangon, most Thomsom designs were (structural) failures. For Team Philips T cubed, you are right.

There is plenty of data (not in Internet...) about the stresses on sailboats (mono and multi), the engineers have now good reliable basis for the calculations, you have just to pay for. I point that the multis designed by a good NA, well calculated and built by an experienced shipyard are very reliable. Idec 2 for example, designed by Irens and Cabanel, calculated by a team of top NE, built by Marsaudon Composites is light but as strong as a tank.

Yes T cubed, in working boats if the NA and NE follow the (multiple) rules, they are covered. In case of drastic innovation, a lot of consultants will work on the project...Sometimes rules have to be changed: after the MS Estonia disaster in 1994, all the rules for ferries had been modified.

 

Cheminees Poujoulat was designed by Juan Kouyoumdjian and built by Decision SA. It has been reported she broke just aft of the daggerboard slots. Again these projects are complex and structural engineering could be by a third party with oversight by a fourth.

 

I think it is pointless to discuss designer's responsibility for extreme racing machines. Those are designed to push the boundary in terms of weight, speed, structural loads; sometimes the designer works with unknowns. They are operated by professional crews who accept the risks. This is like surgeons - some of them will take risky cases and try to do something where not much is possible.

On other side, there are commercial and pleasure craft where 'civilians' are on board. Those are much more strict in terms of safety and here reputation of designer counts. I would say smart design is not only in following the standards, but also in applying good engineering practices where features of craft are not covered by regulations. Say, basic - don't make upper deck too big, so it wont get overloaded by careless/greedy operator exceeding specified number of passengers.

There are other important points; the builder-designer relations is one of them. Some builders I would call 'modifiers'; they demonstrate itchiness to 'improve' some design features of the craft often without understanding all consequences. So they added air intakes on cabin sides below calculated down flooding point - 'yes, shouldn't be a problem'? They replaced all 400g/m2 UD E-glass in laminate by bidirectional 200g/m2 carbon tape, because they thought it is carbon and thus 'stronger' - 'why not'?
Good builder will follow designer's advise and ask confirmation for every doubtable change or detail...

So, talking about any failure try to look at what has been designed and what has been built. Sometimes 'improvements' cause the problem.

We always make a note in design contract that the Designer only guarantees correctness of his calculations/drawings according to specified standards, assumed loads and to achievable engineering accuracy. The Builder is responsible for matching the build with the design, including weights, its distribution, content of resin composite structures, etc. Safety of boat navigation and any other operations with the boat are not under Designer's responsibility, at least in our design agreement. Say, under ISO Small Craft/RCD the 8m planing powerboat can get category 'B', but would one believe it is safe to operate such boat on 4m wave? We not even guarantee the speed as it is affected by many factors, including engine performance and selection of propeller supplier; yes we do careful calculations of speed and that's it.

The designer and builder often can not access to objective information on how the boat was operated and what caused the failure... There are many stories.

 

Alik, I agree...race boats are special cases. On commercial ships the inspectors of the Lloyds, DNV or other society will stop any "improvement itch" from the shipyard as the certification is mandatory, so the ships are strictly built to the specifications and plans. The financial stake is to high for taking any risk.
On warships technological risks are taken and accepted. So you can have great successes and spectacular failures but generally that do not transpire to the ordinary citizen for whom the warships of his country are always the summit of technology and evidently the best of the world, able to wipe out magically any enemy (here you can add your preferred; from castrist barbudos to tiger of paper occidentals, the choice is wide).
There are some surprises when the official "propaganda" appears to be only plain propaganda, ie a mix of 10% of truth with 90% of unproven assertions. Sometimes is flatly ridiculous like the stealth boats, but more it looks improbable more they will believe it like said long time ago by Herr Doktor Goebbels, or maybe it was by Kamarade Beria. But that's another story.
On yachts I have no personal experience but some colleagues working in this field told me some stories of failures where the attribution of responsibilities between the NA, the builder, any contractor and the user, can be pretty hard.

 

This kind of monohulls has a long story of unreliability and failures. It seems that at the actual state of boatbuilding it's a very difficult task to design, calculate and build such boats with the weights they want to obtain.
I suspect that the boat broke in the very steep short seas usual in the entry of the Channel zone when the tide is against the wind. That can be harder for any structure that an ocean swell even in the South Pacific. I can tell by personal experience that a hard sea in the Ouessant zone is a bone breaker compared to a big sea in North Atlantic, you can feel the difference even on a 300 feet aviso.
Maybe also the boat was tired and worn so it was the stress too much.

 

Yes , those much hated "improvements". Oh boy. I had one and just could not talk him out of his changes (mid build) . It still turned out good, but would have been even better had he not messed around with it. What's really irksome is that nobody looking at the boat knows what the unaproved mods were, so it can reflect really badly (and unfairly) on the designer.

Alik, any chance you could point me in the right direction so i can have a look at a typical design contract?
I just finished designing a series of five boats that should start coming into production early next year (2014) and realized i've got to bring my game up to the next level. One of those things, pretty important, is a formalized contract. Any help/pointers would be greatly appreciated.

 

There are few types of builders from what I call 'curious paranoiaс' (asking detail drawing for every bolt, and often using absence of such drawing as a reason to delay the build) to 'creative modifier' (changing whatever he wants without asking; sometimes it comes from too experienced foremen and sometimes is the policy of the builders company). It is important whom are You dealing with to imagine possible consequences and control measures; for remote builds we often require in the contract that photos of the build should be sent on Designer's request. Anyway, changes happen in many builds - from shifting or adding tanks around the boat (oops, 'where the trim comes from?') to changing the exterior where change of window shape is the best way to destroy the beauty of appearance... strange things happen. Now less then before, as builders like to use our name for marketing and would thus respect the designer's work.

Send me an email via PM; I will send You our contract.

 

Too true!

I find the most common is the "beef-it-upper" («can't hurt» he thinks) , not realizing that the heavier it is, the greater the loads, cancelling much of the supposed strengthening, as well as messing trim, lwl, speed, fuel consumption and plenty other things. Also it can create unintended discontuinities in strain actually making it weaker!

They pay us to do the work of figuring it all out, but then want to do it anyways..

Just the other day a potential client came in and started with « i want a boat like X's..» . Bad start. I felt like saying « why don't you just get a boat by X then?» . I know i'm not interested in copying anyone. Inspired by, certainly, but not "like" ....

He wants a sedate centerboard cruising boat type of deal, then starts informing me how hard chines are the thing now because they help get the boat on a plane and all the vendée boats now have them yadi yada

Oh well , you get all sorts. I guess one has to be able to humour them too, to a certain extent whilst keeping one's pants firmly buckled up.

 

@ M Pierzga; «Scientific instruments were fitted to record panel deflection from slamming. The results were far in excess to what was anticipated.»

I think this is a very very common thread, dynamic load considerations are badly underestimated. The mathematical modelling of dynamic loads is not analytically solvable, so there is a big fudge factor there. The best one can do (barring extremely complex computer simulations) is to linearize the largest terms and put on a reasonable FoS, plus a large helping of experience. Also there are a lot of designers who don't actually have that much experience on the oceans to develop a kind of 'intuitive' approach.

Take the classic hydrostatic stability calculations for example; who cares about n decimal places when the moment the boat in in dynamic waves the stability will be altered instant by instant. Hydrostatics is just a guide, after that one has to know what are all the other factors affecting stability in a real dynamic situation, which is hard to quantify in a very precise way, hence large possibilties for unintended outcomes.

 

It was about 20 years ago, maybe more, in the Seattle area I believe and it was the stability test for a rescue boat being built for the Coast Guard. It didn't sink, but failed to right itself and then capsized, so it didn't pass the test. Perhaps this boat was the catalyst for the window improvements you mention.

 

The big mistakes Ive seen occur at the interface of ... As designed ....and ...as built.

Not long ago I was involved with a boat , who during the build phase , changed from fixed keel to lift keel. The lifting mechanism required that a frame be eliminated and that the lifting mechanism act as the new frame....it didnt work.

The boat oil canned amidships, cracks developed on the lifting mechanism frame, the boat was inspected and failed survey. This was a one year old boat built by a topclass shipyard.

Lawsuits put the blame on the shipyard...not the designer.