Catamarans High Speed Blow Over - Causes & Solutions

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

  1. El_Guero

    El_Guero Previous Member

    I agree.

    But, why isn't it being used?

    Cost?

    Rules for the professionals? And that ends up driving the recreational market?

    A lot of the real question is where to place the stabilizing equipment (not using stabilizer, because that is a specific aeronautical term). Don't want to confuse too much.

    Under water? Above water? Or, both? I think some of both is really where you would want it. That coupled with gyros. If all above water, the airfoil would not give adequate control until you hit speed .... And as we are discussing this, because of the problems of all the control from water surfaces, you need at least 60% to 70% of the control from the air.
     
  2. daiquiri
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    daiquiri Engineering and Design

    If the intention is to race the boat, then it is obvious that rules have to be respected. Or otherwise you don't race.
    If the intention is to make a leisure boat, than a designer should do whatever necessary to make it a safe leisure activity. Imo, of course.

    Now, if a client wants to go 150 mph over the water surface, then there is a limit to what a designer can do. For example, he cannot control the waves in front of the boat, wind gusts, rooster tails from other boats or floating debris. In this case, I believe, the boat owners who want to go at 150+ mph should accept the fact that in those conditions they have a fair chance to encounter a random, non-predictable combination of events which might lead to a potentially catastrophic boat instability.

    If you want to go 150+ mph on the water, then you are seeking an extreme thrill. What bigger thrill than knowing that you might die anytime soon? You wanted that boat, so accept it with the spirit of the samurai and open up the throttle. :p
     
  3. El_Guero

    El_Guero Previous Member

    When faced with an engineering problem that is solvable, I prefer to solve rather than to punt.

    150+ at the water surface in most conditions is not difficult. Flying boats have done that for years.

    :p
     
  4. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    Flying boats are really not a good example because they have wings, horizontal and vertical stabilizers, elevator, ailerons and flaps. Fully equipped for going airborne. ;)
    Plus, they are not working in the full ground-effect mode, just exploit that tad of ground effect which allows them to take-off in less space.

    In effect, now that you mentioned flying boats, if one starts considering equipping his boat with all these aerodynamic devices - then yes, they would considerably improve the safety (they have their own problems, though). But then, buying a flying boat rather than a tunnel hull might be a better option right from the beginning? :p :p
     
  5. rxcomposite
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    rxcomposite Senior Member

    Some of us thinks the same way. I made the model last night but was able to take picture only today.

    I made a model out of heavy stock bond paper, glue, coin to balance, and spaghetti stick as a pin. I used a louvered fan to get an even airflow. The model was to closely imitate a typical tunnel hull, almost flat deck, slab sided, CG 30% aft, behavior once airborne.

    1. The first picture is a model with enclosed deck, balanced to trim up slightly.
    2, The second picture was with moderate airflow. The model wanted to flip over.
    3. The third picture has slats. With partially open slats, the model tends to nose down with moderate airflow due to negative lift of the slats/plate. With slight coaxing, the nose went up, stabilizing the model.
    4. The fourth picture has the slats fully opened. At high angle of attack, the model is hard to flip over. It did, so I added a tail extention. Apparently, the forward slats has too much drag and moment, it is overpowering the balance. With the the added tail, the model can reach almost 90 degree and remain stable. There are instances where it will still flip over due to the delicate balance and crudeness of the experiment but overall, it showed that;
    a. Spilling the air with slats will reduce the centroid of area (or AC including the tail) near the CG.
    b. Early deployment of slats will cause a negative lift or nose down attitude.

    In this case, active control that respond quickly can be used. The slats can be nested together so that the deck/airfoil profile can be preserved (similar to commercial jet airliner with leading edge extention and flap extention). Active controls have been used in the McLaren supercar.
     

    Attached Files:

  6. daiquiri
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    daiquiri Engineering and Design

    Rx composite, that's a very good try.
    Another favorable point of that configuration, from the aerodynamic point of view, is that it will shift the CoG forward. That's because of the added weight of the slats, their actuators, and reinforcing structure.
    The negative side, from the hydrodynamic point of view, is that it will shift the CoG forward. ;) That, plus the increased overall boat weight will result in a somewhat reduced top speed.
     
  7. powerabout
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    powerabout Senior Member

    the hulls could be a huge delta shape, thats what the Russians did to prevent their giant wig aircraft from blowover
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    So not tunnels any more ? Or fold out wings like carrier aircraft ? There's the answer, wings that fold down, placed well aft.
     
  9. rxcomposite
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    rxcomposite Senior Member

    Yes Daiquiri. Anything that will add weight and/or reduce the speed of the boat the designer/builder will balk. Even the discontinuty in the slats will add drag.

    So maybe one time use like explosives or compressed air. They may be out of the race but still alive. The decision lies on the regulating body.

    Remember the F1 Ayrton Senna accident you posted? Forensic study showed that when he hit a bump, the car went up, broke the vacuum underneath, lost control and he crashed. The rules was later changed to reduce the allowed downforce of the wing in the interest of safety. The cars went slower. (But only for a while. They were able to think of ways to go faster.)
     
  10. powerabout
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    powerabout Senior Member

    well we know tunnels are fundamentally unsafe at high speed
    thats what makes them good!!
     
  11. daiquiri
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    daiquiri Engineering and Design

    Sorry, didn't mean to downplay your efforts, which I indeed like very much. :)
    I don't think designers or builders would have nothing to say. They would feel more comfortable to have a design track-record which demonstrates safety of their designs. Their clients might have something to say, since they seem to be pursuing the ultimate speed ad power. but, we have few buyers of these boats, they might tell us what is the general feeling among their fellow pilots about trading-off between speed and safety. :)

    It was not Senna in the video. His death was due to a structural failure of the steering wheel axle, not because of the ground effect. For the rest, you're right. Rules are there to be circumvented. :)
     
  12. powerabout
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    powerabout Senior Member

    Hi Daiquiri
    Do you mean senna died from the upper control arm sticking in his head?
    I thought they proved the steering was working as he left the track?
    Cheers
     
  13. rxcomposite
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    rxcomposite Senior Member

    No not that. I realize that there will be penalties and weight. I was just playing around with the rules of aerodynamics.

    For Ayrton, maybe it was another video but their research showed the vacuum broke. It was a forensic study/docu. Maybe another version of the result of the accident.
     
  14. El_Guero

    El_Guero Previous Member

    That is thinking like an engineer .... active controls have advantages and disads... so do passive

    But, by using flight control to balance your vehicle, instead of water, you can fly instead of 'boat' along.

    I would guess, offhand, 300 kts should be doable with existing technology and experience. I might be a tad high. It would depend upon where the water turbulence becomes a problem forcing it through a screw drive ....

    But, you really want what the military uses for active controls, faster than most civilian systems currently used. faster = more responsive, necessary at an 8 foot altitude.

    :)
     

  15. El_Guero

    El_Guero Previous Member

    PS, I think the military already has determined the maximum speed of 'water-driven' craft ....

    :)

    Not that they wanted little ole me to work at skunk works ....
     
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