Maxi Canter, Rambler, capsizes in Fastnet Race

Discussion in 'Sailboats' started by Hussong, Aug 15, 2011.

  1. Doug Lord
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    Doug Lord Flight Ready

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    Check out the 140' Mari Cha IV here: http://www.cariboni-italy.it/public/caritec/products/datasheets/CantingKeel.pdf
     
  2. Doug Lord
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    Doug Lord Flight Ready

    =========================
    The fact is that a canting keel that is well designed, well engineered and well built can have as long a life as any other similarly well designed, well engineered and well built major component of a modern race boat.
     
  3. CutOnce

    CutOnce Previous Member

    You are arguing with physics, not me. This component is subject to greater stress (higher speeds, higher wave frequencies), unavoidable problematic conditions (bulb/CG offset from centerline for greater RM augmentation) and more demanding physical constraints (low drag, thin minimal lift foil section, long span, high bulb weight). Fixed keels encounter none of these problems.

    To keep overall boat weight and drag to a minimum, these components are designed to be as close to minimum tolerance as possible. It is certainly possible to design stronger and higher drag parts that won't fail - the challenge is to design one just strong enough at minimum weight and drag. If the canting keel mechanism is to deliver on it's performance potential, it must push these boundaries as much as possible.

    Added mechanical complexity adds more failure mechanisms.

    Due to these more demanding conditions, there is a higher likelihood of failure. This is clearly predictable and all evidence to date in terms of field testing in real race conditions seems to support these conclusions (canting keel failures are much higher proportionally than their fixed keel counterparts).

    It is fine to be enthusiastic about cutting edge technology, but you have to realistically accept the compromises that come with being out there on that edge. Longevity, reliability, duty cycle and strength are all compromised to achieve the highest performance.

    There is a world of difference between spectacular race tires that deliver huge traction for 30 kilometers of use versus those that deliver adequate safety for 30,000 kilometers. What you are saying is that a Formula One car should be able to use retail consumer tires for the same performance. Canting keels are not designed to outlast the fixed keel on a J24 - and no one sensible expects them to. The people racing this class of boat all clearly know by now the risks they are taking - or they are idiots. I'm certain they aren't idiots, and they understand the risks. At this cost level doing Magnaflux and other NDT inspections between every race is a reasonable consideration and certainly within budget.

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    CutOnce
     
  4. Doug Lord
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    Doug Lord Flight Ready

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    I'm not arguing at all-I just presented the fact of the matter in regards to the use of canting keels. Thats why there are so many of them used under the toughest conditions in round the world ocean races by all the fastest race boats and many cruising boats for years and years.

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    Comments from Neville Crichton(owner of AlfaRomeo in 2006)-message written in 2006:

     
  5. CutOnce

    CutOnce Previous Member

    Wrong. How can you logically arrive at this conclusion? Clearly a well engineered and built canting keel does NOT have as long a life as other components of a modern race boat. If it was well engineered, well built and had as long a life as other major components in a modern race yacht, other major components would be failing catastrophically just as frequently.

    Understanding this indicates that leading edge canting keels probably need regular inspection, non destructive testing and preemptive replacement if required to keep a hull competitive and safe. This is a normal conclusion reached in product design and engineering - each component has an expected duty cycle and inspection frequency - and all parts in a product have different requirements.

    Since yacht racing is a self-policing unregulated activity, and there are no scales of economy, owners obviously opt to roll the dice more frequently than you would with commercial aircraft. EPIRBs and Personal Beacons are cheaper than frequent inspections and testing. And yacht racing crew are much more risk tolerant than most people.

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    CutOnce
     
  6. peter radclyffe
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    peter radclyffe Senior Member

    especially dead ones
     
  7. CutOnce

    CutOnce Previous Member

    History changed yet again and Doug is editing already posted material after it has been responded to. I hate this as it makes subsequent responses look like they ignored details that weren't present when the response was made.

    I am not arguing that canting keels are inherently bad or poorly designed. I am stating that evidence indicates they need preventative testing and maintenance or replacement more frequently than is common practice. The analysis Mr. Crichton speaks of in Doug's changed post is exactly the type being proposed here: Years of racing has indicated that catastrophic canting keel failures do occur with notably higher frequency than comparable leading edge fixed keel boats. Once you acknowledge this, it becomes apparent that better testing and inspection between racing activities may prevent failures.

    Rather than posting quotations of emails from 2006 (when there was far less on the water experience with canting keels than today) as evidence of reliability, perhaps we could focus on the state of the issues today. Mr. Crichton's post actually advocates this type of discussion.

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    CutOnce
     
  8. dougfrolich
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    dougfrolich Senior Member

    fundamental to canters is that large positve/negative acceleration lead to load reversal at the fin root--This cyclic activity will lead to failure eventually---This is true of any cantilever beam that undergoes such dynamic loading--airplane wings for example.
     
  9. Cheesy
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    Cheesy Senior Member

    There is a lot of misinformation floating around here and arguing semantics.

    1. All (well almost, there are some amorphous metals but they are not relevant here) metal that you will come across has a crystalline structure.

    2. fatigue failure can (and usually does) occur well below the loads required for any plastic deformation.

    3. There are various fracture toughness values that metals have which will give an indication of when a fast fracture will occur, ie when there is no crack tip blunting and a keel falls off.

    4. Expected fatigue life can be calculated relatively easily, including ESC effects.

    5. Steel (BCC structure) can be designed to have an infinite fatigue life, there is a knee in the SN curve.

    No one here seems to know (or is willing to explain) how these fins are designed
     
  10. dougfrolich
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    dougfrolich Senior Member

    4. Expected fatigue life can be calculated relatively easily, including ESC effects.

    Exactly!
    I suspect that some folks designing fins say "why 8000000 cycles when we can have a much slimmer fin at 50000 cycles"--- as some sort of cutting edge philososphy
     
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  11. Doug Lord
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    Doug Lord Flight Ready

    Rambler

    Here is the best account of the capsize yet. http://www.projo.com/news/content/RAMBLER_100_08-25-11_ERPTQ6F_v18.45b01.html

    small excerpt: Only Isler and another crew member had emergency radio beacons that automatically send out a distress signal with a location. The signal should have been relayed to rescue crews and the Royal Ocean Racing Club, the race organizer who would transmit the alert to the other racing boats. After about 25 minutes in the water, Rambler’s closest Fastnet competitor, ICAP Leopard, sped by, about 400 yards away. Four or five other boats would pass them by as the men shone strobes and flashlights, blew whistles, and screamed. “We knew every minute was critical for the people in the water,” Dawson said.


    Picture-rig recovered-

    click on image:
     

    Attached Files:

  12. sharpii2
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    sharpii2 Senior Member

  13. Doug Lord
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    Doug Lord Flight Ready

    =========================
    Sharpii, heeding the warning and implicit advice in Dougs post below might be a good start:


     
  14. Cheesy
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    Cheesy Senior Member


  15. Doug Lord
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    Doug Lord Flight Ready

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