X-Beam and the Giant

Discussion in 'Multihulls' started by brian eiland, Nov 12, 2006.

  1. brian eiland
    Joined: Jun 2002
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    brian eiland Senior Member

    Box Beams not Tubular Beams

    I'm not talking 'tubes'. I'm talking 'boxed' cross-section beams or modified boxed beams with aerodynamic shaped front ends....might be referred to as "D' shaped cross-sections.

    And in the RACE version, I'm talking of voluminous beams at their X point to at least accomodate the berths for the racing crew....in leu of the a 'crew pod' as on the ill-fated TEAM PHILLIPS

    As I was looking for the name of that boat (my senior moment), I happened back to my own website and discovered the reason I originally began to think of this X beam subject:
    ** Note: 4/20/2001. As we now know "Club Med" and "Innovation Explorer" both experienced structural problems with their front crossbeams. Details are not fully known, but the majority of problems seemed to have occurred at the connection points between the crossbeams and the hulls, and there it appears to involve considerable delaminations between the hi-tech fiber skins and their sandwich cores.

    ** Note: 5/20/2001. A variety of damage reports continue to filter in, even though there has been a concerted effort to keep them undercover. It now appears as though the damage to Club Med is quiet serious, " Club Med was in a much worse state than many people realized when she made her triumphant arrival in Marseilles. Had this damage occurred earlier in the race, Danby is certain they would have been forced to make a stop over." There are numerous reports of shear failures between the skins and core at the crossbeam connections, on both sides of the boat, and collapses of the core materials of the hulls in the areas of the daggerboards forward of the front mainbeam. The waves had also destroyed the 'bomb bay doors' in the bottom of the mainbeam where one of the liferafts used to be stored. This naturally raises some concerns about her two sisterships built to the same specifications.

    My 'X' beam proposal for those large cats may have gained some measure of validity when you consider the recent comments by Team Adventure, "We will be looking into diagonal bracing of the hulls similar to that on Warta. This was accomplished with kevlar rigging, run from the corners of the beams in a big 'X' (fashion), and will cut down on the racking motion experienced in a seaway. From what I heard from crewman Paul Larsen, this lack of X-bracing - or slackness in Team Philips' 'structural' trampolines may have been a big cause of the Goss machine's demise."
     
  2. brian eiland
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    brian eiland Senior Member

    D-Shaped Beams

    Here is an example from a trimaran a friend is building
     

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  3. yipster
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    yipster designer

    phillips had a pod and i did not know racers sleep in beams, sorry
    that frend looks good tho
     
  4. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    Actually - they end up looking like the same thing - the bow of one ama moves up and the bow of the other moves down.

    It doesn't hold true for the vertical where the hull is pretty well coplanar (ie a plane perpendicular to the vertical axis) so the input forces to produce torsion are pretty well coplanar too.

    I have this feeling we are not talking about the same thing.

    So a diagram attached below.

    The X beam diagram is too simplified so I have taken the liberty of making the base of the intersection bigger than can be seen in the diagram.

    I am assuming the same loads on both.

    Anyway the loads from torsion at the centreline of the conventional crossbeam will be proportional (not equal to) something like L/R.

    With the X-beam it is proportional to L/r

    So if I imagine a real life scenario the loads from torsion on the X-beam at the centreline would be 3 or 5 times greater than the conventional setup.

    Or am i misunderstanding what you are talking about completely - it's possible - I've done it before.

    MIK
     

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  5. yipster
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    yipster designer

    and that goes for me too :p

    re-read the thread and i'm still mostly in the dark but in time some lightbulbs flashed on
    forexample like in a mast beams probably too have I-beams build in
    i started sweating how to calculate and wondering if much cheaper tubes be valid at all
    in the diagram i belive the X frame torque is equal but all the torque now be in the X crossing box
    and better i think than the tranverse beams that use all the area with more play
    asuming we are looking at torque only by individual ama pitching
    in bed last night in the dark again i moved my arm up and imagined beams between them
    there are dozens of positions to move i realised before i fell asleep, maybe i still am :idea:
     
  6. Vega
    Joined: Apr 2005
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    Vega Senior Member

    Perhaps some help can come from the explanations, on the Designer's site.

    They say:

    "So difficult to talk about the Gitana X story !

    On the one hand the determination of Baron Benjamin de Rothschild was clear : after the exciting welcome-in-the-class Gitana IX adventure, he expressed a frank no to the proposed copy-and-paste approaches, that is to compose with existing moulds for creating a new boat, and a resolute yes to create a fresh and virgin design team programmed to re-ask the basic questions and try to open innovative ways... !

    On the other hand, spending so much energy to re-invent the car-with-four-wheels, while your rivals spend that time and energy to optimize the details of a classical config, that was obviously not the right direction, except for one Very Important Point : men able to take and assume projects risks are so rare that they must be honoured just for that..!

    Then, to drive these audacity effectively is the difficult issue !

    Exactly what "our driver" completely missed !"


    They seem to put the blame on the "Driver" that didn't want to wait for the superior time needed to make competitive an all-new concept. It seems that the Guy wanted to win races:p

    http://www.sebschmidt.ch/portfolio/00169/
     
  7. yipster
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    yipster designer

  8. BOATMIK
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    BOATMIK Deeply flawed human being

    Howdy Brian,

    That wouldn't be my take at all looking at the damage

    [​IMG]

    Looks to me that they miscalculated the bending and/or shearing loads on the hulls.

    The crossbeam structure looks completely intact.

    From your report of the crew's comments it sounds like torsion of the crossbeams was a problem too.

    In which case it looks like the whole boat was built on a false set of assumptions about loads from the sea and the rig.

    If that was the case everything was too lightly built and not built big enough in dimension.

    So maybe nothing wrong with geometry of the cross beams - after all there have been many other big multis built with similar conventional crossbeam structures that don't have similar problems.

    So far you haven't (I don't think) explained why the X beam configuration would be better. Sure it would reduce some loads in some places but it is hugely vulnerable at the crossing of the X to torsional loads as I've explained above.

    And those are the wracking loads that the crew is already worried about (quite seperately from the hull failure)

    Maybe I continue to misunderstand something - so if you can explain how the torsional loads at this point are alleviated in your scheme then you might have something here.

    If you plan to build something along this scheme make sure you run a full set of calcs based on existing structures but I think the problem will be that the X beam setup will have to be so heavy to deal with the torsional loads that it will become too strong for the bending loads - so the structure will be overweight/inefficient..

    Or if a third beam conventional beam is added aft then the aft swept arms of the X will not be doing much relative to the other beams.

    With the wracking loads that the X is aligned to deal with - they can also be dealt with as mentioned above by running kevlar diagonally from the forebeam to the after beam - much, much lighter.

    The wracking loads in this plane are the lowest and easiest to deal with - with the fore and aft width of the crossbeams - it is the ones that require depth in the crossbeams that are the most punishing because everyone wants to keep the depth to a minimum for windage.

    So I still can't see the advantage of the X.

    Best wishes
    Michael
     
  9. brian eiland
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    brian eiland Senior Member

    Hi Michael,
    Regrettably I can't spend much time on this subject right at this moment as I am in a rush to finish up a new design idea and take off to Thailand on Mon.

    The damage you see in that photo was the first incident where they discovered the bow areas ahead of the front beams were improperly reinforced. if I remember right there was serious questions as to the proper bonding of a reinforcement rib on the inner sides of the hull skins.

    The second incident where she was feared to break up, and thus abandoned, I believe involved the flexing of the entire beam structure that promted those other comments.

    Sorry my memory is a little vague here, and I didn't have time to go back and research it properly.

    PS: I am going to surprise a lot of folks with the next design proposal I'm working on:idea:
     
  10. brian eiland
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    brian eiland Senior Member

    Team Phillips reference

    ....a recent posting from another forum

    The new Pete Goss website is worth a visit, even if only to see the beginnings of the storm that took Team Philips: http://www.petegoss.com/journey-to-date-team-philips.php

    32 knots under bare poles with 30 tons of drag in the water convinced me of the need for a telescoping mast. They would have better chances to save the boat if its masts could be "reefed" this way.
     
  11. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    X Beam purposes for Tri

    Hi everybody,

    Very intresting topics, on my side, just as an amateur, I try to find the good idea to achieve a slight X configuration and curved in order to gain clearance above the water, for a small cat.
    I asked ideas to a friend who has been maintenance engineer for 60 tri like Sodebo and also used to work on hydroptère for a few years.

    About the X beam for 60 tri, he explained me that it was intentionnally to allow the platform to twist because the 3 bows of the boat do not meet the wave at the same time according to the angle between waves & boat direction.

    Overall it is intended to minimize platform pitching and the rig does not seem to suffer from stays connections at the X tips.

    As I am not engineer, I am still looking for ideas to to something new for a A cat, including building process ideas. Compared to 60, a A Cat experience, would be probably cheaper!

    Good Wind everybody

    Erwan
     
  12. Pericles
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    Pericles Senior Member

    Brian,

    Both IDEC and Sodebo have their amas connected to the central hull with curved D shaped transverse beams that locate into the upper surface of the amas. This setup seems remarkably strong in resisting the twisting action you mention when only one ama is in the sea. Could this be down to the use of superior building materials, not available to earlier vessels?

    Regards,

    Perry
     
  13. Erwan
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    Erwan Senior Member

    Amas = lateral hulls ?
     
  14. yipster
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    yipster designer

    oui ami thats right

    Herreshoff, Antrim, Wharram and others tackled the problem, even deckhouses have torsion

    have to read Pete Goss book and hope he finds the time to write one on team Philips
     

  15. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    G'day,

    There are a bunch of ways to improve an A cat, but they are pretty extreme as the current boats are so advanced and the weight limit means there is no return from conventional improvements. If you are interested in doing something extreme, please let me know.

    Regards,

    Rob
     
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