Catamarans High Speed Blow Over - Causes & Solutions

Discussion in 'Hydrodynamics and Aerodynamics' started by kidturbo, Sep 11, 2013.

  1. daiquiri
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    daiquiri Engineering and Design

    I remember (though it was so many years ago) that it was found back then that steering wheel axle broke right when he tried to turn it to engage a left curve, leaving him with no control of the car. So the car went straight into the tyre wall barrier, which he impacted first with the forward right tyre. At the impact, the upper suspension arm snapped and one part of it hit Senna's helmet, perforated it and caused a fatal head injury. Now, perhaps something else has popped out from the investigations in the meanwhile, in which case my info is outdated.

    By the way, can't help noting how I remember these things of 19 yrs ago as though they happened yesterday, but if you ask me what did I eat 7 days ago, I won't be able to tell you. It is really incredible how selective human memory can be. :)
     
  2. rxcomposite
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    rxcomposite Senior Member

    That happens to me too. Some memories playback like a video. And in color too. Sometimes it evokes emotion, but most of the time, none at all. What was that we were talking about? Hahaha.

    For the military hardware, I am no longer in the aerospace industry. Used to collect lots of magazines keeping up with the latest info. Now I have only the 10 year old Jane's manual, and a broken RC helicopter.:D
     
  3. daiquiri
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    daiquiri Engineering and Design

    Getting back to the technical side, does someone here have a data about mass moment of inertia (or radius of gyration) of a 15 meters (50 ft) racing cat?
    I would like to perform few calcs about response time of various solutions.
     
  4. El_Guero

    El_Guero Previous Member

    Janes ....
     
  5. daiquiri
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    daiquiri Engineering and Design

    Jane's...

    :p
     
  6. rxcomposite
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    rxcomposite Senior Member

    Yup. It's JANE'S. I have the 27th edition of High Speed Marine Craft.
     
  7. El_Guero

    El_Guero Previous Member

    What was that? $350?

    Class or Unclass?

    :)
     
  8. kidturbo
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    kidturbo Junior Member

    Nice slatted deck concept RX. That was actually my first concept [in thought] also. Dump that lifting air and they can't fly.. Flush hull panels that open up could easily be incorporated into a new design. Not much weight would be added, just hinges, release pins, plus a little glass work.

    Then I think retro-fitting, basically cause one of these early 90's style big cats is parked in my yard :D The wife will likely get pissy if I blow her cuddy cabin apart to prove a theory... Easier to just deal with a blow over situation. lol

    What I'd really like to see is an illustration using a single slat deployed from the bow and those impacts on lift. As listed above, this could be actuated quickly with air or electrical rams. If quick enough reaction, one might halt the departure before angle of attack goes critical. Even a second active spoiler on the rear could be added to increase effect.

    The best part about this discussion, the scale models are more popular than the real thing. So testing working concepts is gonna be easy, just bust out a good helli gyro, fit the idea to a couple of these RC versions, and then whip up some waves with a jet ski. :cool:



    Here is our test pilots.

     
  9. BMcF
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    BMcF Senior Member

    You just touched on a fundamental piece of the puzzle when it comes to computer stabilizing essentially unstable, or marginally stable, vehicles, whether marine or aircraft.

    Modern flight control systems (whether flying an F-117 or a high-speed hydrofoil) achieve and maintain stable flight by reacting primarily to angular rates-of-change (and even the second derivative..angular accelerations) of flying attitude. A typical high-performance flight control system measures and responds with countering foil (flap, tab, etc) action to very small angular rates and angular accelerations that are divergent or deviating from the desired or commanded flight attitude. The foil responses are extremely fast (within milliseconds) and occur long before a human operator would sense and respond the changing flight attitude.
     
  10. daiquiri
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    daiquiri Engineering and Design

    That video gives a hint about what happens and what to do, in order to diminish the risk. Note the the boat capsized two times while encountering it's own waves. The only time it didn't capsize was when it slowed down just before hitting the waves (at 1:43).

    Morale of the story: preventing the illness is better than curing it. Sometimes it is wiser to slow down a bit at the right moment - costs less than installing a fully-automated flight control system. ;)

    But I imagine you probably already know that... :)
     
  11. daiquiri
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    daiquiri Engineering and Design

    Precisely so. And what they actually do is to maintain the aircraft inside the flight envelope where these control surfaces are effective. That's why I said that I don't think it would be very effective for restoring the boat once the blow-over has gone beyond a critical point. But they would be useful, if working together with pilots sound judgement and testosterone control, for maintaining the vessel inside the safe zone.
     
  12. Petros
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    Petros Senior Member


    something like a slat might work, you need to suddenly kill the lift in the front, and increase lift in the back, in a balanced way so it does not continue to pitch upward, but maintain a relatively level flight attitude.

    There is some aerodynamic hysteresis, that is it will take a moment of time to alter the airflow and to generate the correcting forces. These aerodynamic forces have to slow and over come the inertia forces of the rotating mass of the boat, slow it and than bring it back under control. if the correcting aerodynamic forces from a deployed surface such as slat or fin are to work, they have to be larger than the inertial forces acting on a fast moving hull. And certainly you do not want to over compensate either, or the front of the boat will slam back into the water. So analysis will by necessity be complex since there is a critical time element in the problem.

    This is a complex problem, and will require quite a lot of the correct resources to first model it, and than test it in stages. After a rigorous computer analysis, than scaled models, and than eventually a full sized powered hull. So, who wants to be the first one to volunteer their expensive boat to test it out? who wants to be the first one to ride it out and tell everyone what it was like?

    this kind of thing is way outside my area of expertise.
     
  13. kidturbo
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    kidturbo Junior Member

    BMcF; Computer aided flight controls have proven very useful in fighter jets and feel they would be reasonable additions here too. Majority of the "supercars" use them in some aspect as well.

    daiquiri; Like jets, these boats could also benefit from ejection seats. Computer controlled ones, so if it senses a big testosterone surge, it boots "you" out and continues flying "safely" along it's course. ;)

    Petros; Any ideas where we can find an aeronautics student that would simulate this theory with some good software? Can visualize it, but prefer to have a computer explain it to me. As for the expensive boat volunteers, that's another subject. But I agree plenty of testing time on scale models would be required to get crisp correct control inputs..
     
  14. powerabout
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    powerabout Senior Member

    dont forget the tunnel boat can roll over then fly upside down and then blowover
     

  15. Petros
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    Petros Senior Member

    yes, roll stability while airborne would have to be part of the solution, and yaw stability as well. it would not do any good to keep the boat level and have it flat spin and hit the water backwards.
     
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