No Interest in the AC?

Discussion in 'Multihulls' started by RHough, Nov 30, 2009.

  1. jehardiman
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    jehardiman Senior Member

    I disagree here. Multihulls are more heavily loaded per structural pound due to thier geometry than comperable monohulls. It is this higher loading that gives them thier performance advantage, and is the root of thier structural problems. Worse, as force on the rig goes up, the hullform of a multi increases the structural loading factor faster than a monohull. Given the same strength and quality of construction, one would expect multis to have proportionally more failures simply because the factored loads are higher.

    Yes, I have considered that and comparatively the numbers are still 3:4 basted on the total number of yachts.

    If you look at the just run Jacques Vabre, you will see that in the first week (where the majority of the structural failures occured and the wind was on the nose) that the mono's as a group made more distance to finish than the multis. Absolute speed is meaningless if you aren't making good towards the finish. It is important to point out that with the exception of Crepes Whaou, all the multi lost so much distance in those first two weeks that they were unable to catch any of the monos regardless of thier supposed speed advantage. Similiar occurances can be seen in the previous two Route du Rhum's. WHEN multis get the conditions they excell in they are fast, and IF thoses conditions are favorable then they MAY be able to set records...IF records without thought to practicality is your measure. Too many conditionals for me to proclaim them the best type of vessel.... Shrug... different horses for different courses.

    As I pointed out in my comment to Doug, it is technical rerason why multis fail more, not bais as you contend. Given two vessels engineered and built to the same standards, the multihull will be expected to break first due to the acceleration of loading factors during the loading event. It must be remembered that it is the stoichastic event that is just over the design envelope that causes damage. Wether it be an airplane, car, ship, or racing sailboat, the structure survives or not based on the accretion of factors marginally in the designers control. When it comes to the final analysis, this accretion is occuring more slowly on a mono hull than on a multi which makes the chance of failure statisticly less probable for the mono.

    Additionally, it appears that in order to make a competitative sailing ocean racer , a loss rate of 20-30% for monos and 30-40% for multis is acceptable to the designers and sponsors. Similarily, to win the 33rd AC, the designers must limit the vessels to sailing in weather that apparently disgusts most sailors. Just like the loss of the two IACCs to structural failure, if one of the multi's in this race is lost, blame the race rules. But the fact will still stand that the loss of 2 out of 30(?) is a better survival rate for the monos than a 1 out of 2 for the multis.

    My prediction for the next RdR is that it will be the same as it has been in the past few years : the precentage loss ratio between the all the mono's and all the multi's will be the expected 1:1.3 (i.e. the % multis lost/withdrawn will be 1.3 times the % monos lost/withdrawn).
     
  2. RHough
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    RHough Retro Dude

    A design that is more heavily loaded per structural pound is more likely to fail. Fine, that makes sense.

    Are you saying that a multi-hull will NOT have an advantage if built to the same weight of structure to load ratio as a mono?

    That is where your arguments dis-connect for me.

    When a multi is 15-20% faster over the same water as a mono built for the same purpose, is it your contention that the increase in speed is solely due to higher loading of the structure?

    Just haw much weight of structure would you need to add to make a big multi as slow as a Volvo 70?

    "Given the same strength and quality of construction, one would expect multis to have proportionally more failures simply because the factored loads are higher."

    WTF? This statement makes no sense to me.

    If the factored loads are higher, then the strength as a margin of error/safety is lower.

    Given the same quality of construction and the same error/safety margins the higher loads of a multi should require that multi's are heavier than mono's. Are you saying that given that equality a multi would be no faster than a mono? That is to say that a vessel where 100% of the weight can be structural should be slower than a vessel where 40-60% of the weight is ballast (and not structural).

    That is a conclusion that is very hard to buy.

    R
     
  3. Doug Lord
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    Doug Lord Flight Ready

    ===========
    Seems to me that you may be omitting the designers skill from the comparisons you make. It would seem to be a "given" that highly trained ,competent designers and engineers would take into consideration the points you make above.
    The problem is, in my opinion, that the bar for this particular America's Cup is set too low: I'm convinced that the extremely talented people in both camps
    could design multihulls that would sail in much tougher conditions than the parameters set for this Cup. That means that the problem is not at all with multihulls but with the setting of such a narrow range of sailing limits-and that is one of the profound lessons of this Cup.
     
  4. Chris Ostlind

    Chris Ostlind Previous Member


    That's a prediction of supposed attrition rates, based on a slice of averages (which will wander all over the landscape, or it wouldn't be an average) not a winner. You know, as well as I, that generic predictions are just that, generic in nature and not specific at all. If your analysis holds, there wouldn't be a purpose in betting on any contest of technology and skill. There would be less of a purpose for sponsors to spend millions, suspecting that their boat would be dunced-out in the first two days of such an event.

    In short, the whole thing never abides by generic predictions. It abides by the moment and about ten million variables which can not be predicted.

    Conditions which prefer monohulls?... when all the boats, including monohulls, are principally designed to run downhill? You're going to have to explain those conditions to the designers of the craft if you have any notion of it being applicable. These guys also look at trendings, weather patterns in specific areas of the globe and skipper skill sets to come up with a boat that will work best for the vast majority of the time and produce the best results. When you say this, you are saying that multihull designers haven't a clue as to how to design for upwind possibilities, or tougher sea states.

    I'm rather more inclined to believe that the skippers are the ones who get their boats into compromising positions that exceed the design potential and not the designers. These choices are driven by the need to compete far more than the need to hang around in safe waters and then compete later when it suits them.

    Each and every report that I've gotten about these monohulls, be it Volvo 70's Open 60's, whatever, the skippers all say that they got the crap kicked out of them while driving uphill incessantly... until the conditions changed to something more favorable... like doing the bad thing on a reach with the skimming hull minimized for wetted surface and a committed hope that the swinging keel holds together until they arrive and the mast doesn't get shaken to pieces from the pounding.

    Again, there are too many variables to offer any more than a studied guess as to why certain boats did not fair well and others did. Did they start at the same time and in the same conditions, did they move away from the start point, looking for the same point of sail, relative to on-coming conditions, and on and on the analysis would go. Interestingly enough, at no point do you assign the simple function of dumb luck in the equation. It's as if all these events can be categorized by some pre-determined formula and it's just a matter of running the numbers. I do not happen to agree with that methodology.

    So, here's what I want to know from the analysis process you prefer... Can you predict a winner... you know, the only real prediction that matters to racers.
     
  5. TollyWally
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    TollyWally Senior Member

    "I disagree here. Multihulls are more heavily loaded per structural pound due to thier geometry than comperable monohulls. It is this higher loading that gives them thier performance advantage, and is the root of thier structural problems. "

    I don't fully grasp this yet but intuitively it makes some sense to me. I am assuming that generally speaking, a large part of the load experienced is a product of the forces that provide propulsion. When unexpected forces are encountered, designs near the outer edges of the strength envelope would have a higher risk of failure. LOL, aint no free lunch!
     
  6. jehardiman
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    jehardiman Senior Member

    Lets look at two "comperable" boat classes, the IMOAC 60 and the Multi 50 which just raced head to head in the Jacquas Vabre. I use these two classes because they do race the same courses and generaly finish together.
    Typical IMOAC 60 length 18.2m, beam 5.7m draft 4.5m disp 8.5t upwind SA 300m^2 downwind 600m^2
    Typical Multi 50 length 15.2m beam 15.2m dradt 3.5m disp 4.2t upwind SA 175m^2 downwind 241m^2

    So comparing SA/D IMOCA 60 upwind = 72, downwind = 143, the Multi 50 numbers are 67 upwind, 92 downwind. Likewise D/L IMOCA 60 = 39, Multi 50 = 34, so not much to chose between the two as one carries more SA for it's displacement (the mono as expected due to the stability requirements) and the other is lighter for it's length (the multi...again as expected due to stability tradeoffs)

    The big difference is in the ability to carry sail, which is proportional to the beam squared/ disp^2/3 IMOCA 60 = 8, Multi 50 = 89. Even if we assume that the canting bulb is 50% of the weight of a IMOCA 60, the IMOCA 60 would still only have a sail carrying factor of 20 or 1/4 the Multi 50.

    Given that loads are proportional to SA/D and sail carrying ability then the multi 50 loads would be 4 times ((67*89)/(72*20)) the IMOCA for the same windspeed. But the available material weight for structure is nearly identical 4.2t ~= 8.5t/2, even less if you consider the additional shell plating on the multi and the inherent efficency of a monolithic hull. You would need to make the structural weight of a multihull 4 times the necessary weight of a monohull to reduce the stress to the same levels...(yeah, lots of assumptions and generalizations going on here, but pretty much the structural problem).

    What it boils down to is that the rig moment in a multi must be reacted out through the crossbeams, specificly through the crossbeam to ama connection. This is a structural load concentrator that multiplies the already high transverse moment given the wide dispersed nature of the multi-hull design, this is the "stress concentration factor". In a condition which the loads reach overload, either from stoichastics or damage, this multiplier will quickly increase the stress in the joint faster than the proportioned overload, this the 'factored load". Given that structure weight and material strength is limited you cannot just continue to beef up the joint or surrounding structure ad infinitum. There is a point that the designer decides that he can no longer increase the structural weight without compromising the design. FWIW, monohulls also have stress concentrators, such as the keel flange, but the load carring factor of a monohull decreases in proportion as the hull is loaded, in contrast to the multi...see the discussion from years ago in the http://www.boatdesign.net/forums/multihulls/canting-keel-monos-vs-multihulls-13511.html thread.

    I cannot give you a structural design course over the internet. You need to do some detailed non-deterministic design of multi-hull structures to make the structural problem readily apparent.
     
  7. jehardiman
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    jehardiman Senior Member

    Actually I am considering designer skill, but as I pointed out in my response to RHough, the transverse stress for the same design conditions are significantly higher just to the inherant geometry of a multi. Or are you implying that multi-hull designers can make joints 4 times more efficient that monohull designers given the same materials... that I find had to believe.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Cayard on the AC

    From Scuttlebutt:
    NOT PUTTING OUR BEST FOOT FORWARD
    By Paul Cayard
    The sentiment around the media center is that the first race (for the 33rd
    America's Cup) will be held on Sunday. Many feel the forecast for Friday is
    poor also. I would say that the weather is too variable to predict
    accurately and with the criteria for racing requiring both wind and wave
    accommodation, the acceptable window is quite small.

    With these delays, we are losing some media and fans I imagine. It is
    getting difficult to keep the energy up and to create content for
    television. There are only so many stories that can be written about the
    cool technology contained in these two boats. After a certain point, the
    people want to see a race. Eurosport (television, for whom Cayard is working
    for) will cover the race on Friday if there is one but today's cancelation
    means that we won't be here to cover the final race, as the team is leaving
    for Vancouver on Saturday. I am heading to Dubai Friday night for the RC 44
    event there.

    I am very frustrated by all this as I feel we are not putting our best foot
    forward as a sport. Obviously, February in Valencia is going to be tough
    with the weather criteria as tight as it is for these boats. Maybe Alinghi
    and BMW Oracle should agree to postpone racing until May. That would allow
    for better weather and therefore a higher likelihood of racing when
    scheduled, and more time for sponsors to organize their visits and
    hospitality. Considering that they haven't agreed on one thing yet, this is
    not likely to happen. --
    http://www.cayardsailing.com/cs_Reports.cfm?evtID=115&csRpt=886
     
  9. jehardiman
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    jehardiman Senior Member

    Because of the variables, in a single race, it is impossible to predict a winner because it is all fate. Just like poker, the cards have no spots till you turn them over. Given that weather and waves are a stoichastic process, it is never certian that the best boat or better sailors will win. Just look at the 16th cup in '34 when Vanderbilt went below to drink while the crew sailed Rainbow around the hole that swallowed Endeavour. Nothing is ever certian in a single die throw, otherwise, there wouldn't need to be a dice at all.

    However, stoichastics works on many throws of the die. While I cannot predict which die will roll a "6"...odds favor at least one die comming up with those spots in a throw of 6 dice.
     
  10. Willallison
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    Willallison Senior Member

    Crikey! There's more analogies in this thread than a politician's election speech!
    The problem as I see it, is that the AC has failed to capture the imagination of those who aren't particularly interested in sailing. When Oz 2 won in '83 and then defended in '87 and entire nation was 'behind' the campaign. But more than that, the David vs Goliath battle drew in a world-wride audience that had probably never watched a yacht race in their life.
    Sadly, the farce that has contiued since then has ensured that they probably never will watch another again....

    And whoever it was that said some pages back that people who know cars watch Nascar, whilst those who know nothing watch F1 was a dill. No offense intended!
     
  11. CT 249
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    CT 249 Senior Member

    Randy-

    1- The US courts found, after all the vast barrage of evidence in the Mercury Bay hearings, that the reason that the writers of the DoG did NOT ban multis was because they could not conceive of an AC multi - not because they wanted the Cup open to anything. To quote a judgment in Mercury BAY, 'the Cup donors—
    the record clearly shows—never conceived of a catamaran as a vessel that might be entered by either a challenger or defender in America's Cup competition.'

    Note that Herreshoff wrote that "the catamaran is a perfectly distinct variety of vessel" (compared to a normal ie mono yacht of his day). Who better than the AC and cat expert of the time to listen to?

    2- It's not really worth responding to your claims that sailing has not adopted changes like golf and motor racing have, because those claims are simply incorrect, as the most basic look at a 12 and an IACC boat, and at the rules of golf and motor racing, will show.

    3- Although you never address the point in your haste to criticise those who want mono to race mono (and windsurfer to race windsurfer, kite to race kite) almost ALL sports have separate disciplines; no one criticises when snowboards are given separate competitions to skis, streamlined recumbent bikes are banned from the Tour de France in favour of conventional bikes, Le Mans Sportscars are given different races to Stock cars and F1 cars and giant trucks and motorbikes and sidecars and the Thrust SST rocket car, etc etc etc.

    Dunno how you keep on criticising the sport some of us love, for something all other sports do for the same good reasons. Other sports recognise that if you allow everything in, you lose the appeal of contest between similar equipment. You lose the appeal of people sharing the same challenges.

    This is demonstrated by the fact that at most mixed fleet regattas, people drink with people from their own sailing class. As someone who sails all types, I have seen very strongly that people hang with those who have raced the same craft, facing the same thrills and challenges. You take a LAser to a mixed regatta, you tend to hang with the LAser sailors. You take a cat to the same mixed regatta next season, you drink with the cat sailors - and you notice the other class-hoppers do the same thing.

    When you have craft that are too disparate that fellow feeling can often be lost, so you get fewer sailors - not to mention the logistical and other issues. If some events like to mix, then good on them - but they should allow other events to have different ideas and respect their diversity and opinions instead of insulting them.

    4- As someone who has competed in singlehanded cats, tris, singlehanded dinghies, skiffs, team racing, two handed dinghies, freestyle windsurfers, racing windsurfers (development and one design), off-the-beach two-person cats, Open 60s, wavesailing windsurfers, match racing, speed-sailing windsurfing, power-ballast maxis, IOR boats, RORC rule boats, IRC boats, JOG boats, offshore one designs, level raters, inshore day-racing keelboats, singlehanded offshore yachts, offshore racing cats, heavy displacement leadmines, lightweight monos, three-handed dinghies, 12 Metres, gaffers, old maxis, sailing canoes and more, I can assure you that I'm NOT against diversity, which is one of our wonderful sport's greatest assets.

    Those of us who would like to normally have separate races for different types are FOR diversity, not against it. You don't get diversity and numbers unless you have restrictions. You won't get the wonderful old gaffers racing if you put them against windsurfers or Farr 30s and tris each week. You won't get a huge Laser turnout if they have to chase long-gone A Class cats around the course on Saturdays. You won't get strong PHRF fleets if heavy Catalinas are expected to race Formula 40 cats or Farrier tris.

    Yes, monohulls differ in performance, but by nowhere as much as they differ to multis. And just because a few canters are messing up mixed-fleet racing (according to the feelings of many) is no reason for more boats with more variation to mess it up even worse.

    And the very reason that many people use for allowing multis into the AC - that they are faster, therefore they are better, therefore they should be in the biggest race - undermines that wonderful diversity, because it devalues the slower boats (Lasers, Snipes, Hobies, Windrush 14s, Catalina 22s, 470s, J/105s, etc) that make up the bulk of our fleets. The thinking "faster=better" is actually a direct attack on diversity, because it devalues and therefore discourages the millions of slow boats that give the sport its accessibility, economy and diversity.

    5- And finally, one reason I tend to argue hard in this sort of discussion is that the 'fast boat' side too often gets personal, as with the remark that mono sailors are snobs when they want to normally just race monos.

    Are we windsurfers snobs when we have their own World Cup and don't allow kites, cats and Beneteaus in?
    Are my friends in kitesailing snobs when they don't hold competitions that are open to Lasers and old gaffers?
    Is the tri owner I'm going to race with a snob because he organises multihull-only races that ban canting keelers and Farr 40s?
    Are the Euro cat sailors (like a friend of mine) snobs for not letting kites, windsurfers and monos into Texel?

    Strangely, you never address the question of why mono sailors are criticised for doing what kite, board and multi sailors do - that is, normally preferring to race like against like because it creates better racing. Anyway, I'll comment no more, because when you started accused others of personal defects like snobbery and paranoia, reasoned discussion exited stage left.
     
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  12. powerabout
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    powerabout Senior Member

    it was me

    Re the OZ defended, actually Bond knew he couldnt match Conners spend so he opened up the defender to a sail off and lost (ha ha) to a guy who was hated by everyone and we all knew would lose and he did

    My quote re the nascar v F1 was in reponse to the spectacle of yacht racing.
    What I tried to convey was that when it super high tech it has a bigger draw then when its technical and held in class rules.
    Just look at the international appeal of Nascar..close to nothing and F1 huge.
    I know many people who watch F1 but are not interested in any other motorsport. I 'm sure the cup is the same.
    Its the same in OZ we have our V8 supercars and many locals relate to that as its our local cars... BUT i'll bet the F1 TV viewing is far greater and we have no OZ team since the 60's so what are the people relating to that makes them interested?
     
  13. powerabout
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    powerabout Senior Member

    Well said
    Several nice points made there

    (PS personally I hang with the keel boaters as they have the biggest eskys)
     
  14. Willallison
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    Willallison Senior Member

    Sorry powerabout - not quite sure what you mean still - maybe it's me that's the dill!!:D

    F1 is, without doubt, the pinacle of motorsport. But it is still heavily regulated. Not in the same way as Nascar, perhaps - there is still an ecouragement to further technical advancement. Our V8's are much like Nascar - an entertainment spectacle as much as a motor race. None the worse for it either, I think. But I would reckon that most who actually follow F1, myself included (as opposed to just watch the occaisional race, or go to one when it's in their own backyard) are enticed by the technical aspect of it as much as anything else.
    It is the most watched tv there is - so old Bernie must be doing something right....
     

  15. powerabout
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    powerabout Senior Member

    No prob i'm not disagreeing

    I was making the comparison that the AC is watched by more people than any other yacht racing because its like F1 compared to the rest.
    Mega bucks spent and cutting edge technology used and invented but still to a set of rules so there is a competition spectacle.
    Therefore non sailing types get interested just like in f1 re non motorsport fans.

    It was mentioned that the use of production boats in the AC would get more people intersted and with that I would disagree.
    It might make some enthusiasts more interested but thats all
    Going fast re cat v mono is relative...Nascar at 150 or 200mph same race.
    "We can put as good a show on at 150 why do 200"
    quote Richard Petty

    The risk is the faster you go the bigger the difference in max speed of the compeditors so the race gets boring which is probably what we are about to witness?
     
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