T-Craft

Discussion in 'Boat Design' started by kach22i, Apr 16, 2007.

  1. BMcF
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    BMcF Senior Member

    [​IMG]

    OK..I got it now. those were a key part of the propulsion concept that would ahve never worked. And imagine the noise!..as bad as LCAC but with passengers??

    Thankfully..some projects die when they need to. I've worked a few that did..and some that didn't die soon enough.
     
  2. kach22i
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    kach22i Architect

    I have a "wait and see" attitude about the thrust concept and most sound travel paths hate right angle changes.

    If you can keep the weight down, you can lift or float just about anything.

    I found out the hard way when I left the cover off my hovercraft one winter, until I remove the waterlogged foam it will never have a chance of flying right.

    Weight is the enemy, but that is another topic for another day.
     
  3. BMcF
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    BMcF Senior Member

    A junior aerodynamics engineer can prove that the thrust efficiency of that mess pales in comparison to the the already rather poor efficiency of the best ducted propellor designs out there.

    And no George..when you are talking about the sound power spectrum involved in making those thrusters blow..you might be astonished how much of it will travel in any/every direction it cares to..virtually un-attenuated. And that is something I have far to much teeth-gnashing experience with, having helped design and actually build test so many SES and ACV.
     
  4. kach22i
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    kach22i Architect

    I trust your experience and word on the matter.

    It is more an matter of efficiency (or lack of) than sound as you have clarified. My background is with buildings, and yes those 90 degree elbows can be attenuated (baffles/insulation) and do work.

    http://www.michiganair.com/newsletters/2007-2/section3.htm
    [​IMG]
    Elbow Sound Traps with circular connections

    I cannot say if those roof mounted vector things had provisions for sound attenuation, my guess is not and that you are correct. However I still would like to see (hear it) for myself and not rely on theory or the experience of others. I'm a hands-on type of guy and have found errors and omissions in text books which are misleading.

    Maybe active sound attenuation would help (speakers in the path), but this would not do anything for the thrust efficiency.
     
  5. BMcF
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    BMcF Senior Member

    You are talking about noise transmission along/within duct boundaries. I'm talking about the open-air radiated noise field at the exit an d 'breakout' noise everywhere through the ducting. Active noise attenutation requires long section of duct..not there. And ..ahem..how many HP of air are you moving down an HVAC duct the size of one of those thruster ducts?..and how many HP of air is expected to move through the thruster ducts? Rather huge difference, yes?

    George..I'm ONLY talking about reams of my own direct hands-on experience with all of the above. I'm sure you would not find it surprising that the vexxing problems of noise in sir-supported vessels have always be a huge concern to the passenger ferry operators..and even more so to the military folks who want their ride to be at least long-term crew friendly if not also extremely sneaky....;)
     
  6. BMcF
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    BMcF Senior Member

    An interesting approach. I've learned from failures, yes. We all have. But I do not ever consider failure to be the goal of anything I'm attempting to achieve and much prefer avoiding it as best possible through a rigorous design process...

    Surely you do not take that approach with the design of large HVAC systems...
     
  7. kach22i
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    kach22i Architect

    Thank you for putting the problem in context, I understand it better now.

    You otta open your own school or something.:D
     
  8. BMcF
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    BMcF Senior Member

    LOL..the class would have three pupils and you would probably be one of them. Methinks that imparting my extensive range of ACV/SES knowledge and experience might be worth..a free cup of coffee? :D The value of all that experience is heavily attentuated by the total dearth of any projects that might make use of it.:rolleyes:
     
  9. kach22i
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    kach22i Architect

    1. In business/architecture it is always best (most profitable) to take the shortest path, and I hire an engineer to design my HVAC systems.

    2. In hobby land (hovercraft for me), I take the scenic path to learn as much as possible and failure is nothing to be feared, although as you pointed out - failure is not a goal.

    3. One day I would like to take a longer path on my architecture ventures and a shorter path on my hovercraft engineering/design adventures.
     
  10. BMcF
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    BMcF Senior Member

    I can relate..and recently turned my 13-yo son loose to build a 'reverse three wheeler' that he saw on Junkyard Wars. He'll learn a lot.
     
  11. nikezz
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    nikezz Junior Member

    Really stopped?

    I'm sorry to ask this, but if the T-craft project been cancelled, may I know the reasons behind it? Were they technical? Or was it just a funding cut?
     
  12. BMcF
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    BMcF Senior Member

    The 'official line' was that it was a lack of funding or funding cut. The unofficial line .....Chief of ONR didn't like it and decided that it was not going to be built on his watch and had decided that long before the second phase design efforts were completed and proposals submitted for construction.

    To be fair, the concept had a lot of skeptics and detractors..and some of those skeptics included yours truly in the beginning. By the end, however, there were truly viable designs produced by at least two of the three teams.

    With amphibious warfare concepts and doctrine in a total state of flux right now..its certainly within the realm of possibility that the requirement from something likc T-craft could emerge.
     
  13. nikezz
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    nikezz Junior Member

    I have seen some interesting things from Google and I was pondering a few questions. They are not linked but were questions that I thought of as I read through the thread.

    1) May I know what the detractors were saying about the T-Craft?

    2) Am I right to say that the designs and prototypes are no longer required by the US ONR?

    3) There is a Russian hovercraft called the Zubr that was bought by China at 80 million each. How would you compare that to the T-craft?
     
  14. BMcF
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    BMcF Senior Member

    The answers to your questions are, in fact, intuitive and easily gleaned from the internet if you know anything about LOTS and amphib ops. That said:

    1. The detractors and skeptics had a range of criticisms, many quite valid. They ranged from 'too expensive to affford enough of them' to being picky about potential CONOPS ("250 nm OTH ops?..are they crazy?") to being very legitimately concerned about the reliability and maintainability of such a complex machine, etc etc. You can even step it up a level and find strategists that question the future need for amphibious lift at all..

    2. No, you are not correct in saying that at all..but you are forgiven because you probably do no understand ONR's core mission.;) ONR is tasked with doing things, often very technically risky things, in the Science and Technology realm that regular Navy and its contractors dare not touch. T-craft may still 'transition' from the ONR world to the real world and it is even more likely that technologies developed over the course of the T-craft program will transition. And that right there is exactly what ONR is all about.

    3. Quite familiar with the Zubr's..have been for many years. The T-craft is not one..not even close. The T-craft is a long range self-deployable surface-effect-ship (SES) medium-capacity lighter that can, if needed, become a fully amphibious ACV for low-speed near-shore amphibious operations. Zubr is a conventional hovercraft.
     

  15. kach22i
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    kach22i Architect

    Back to Atlas just for a second.

    John Carter's photos:
    http://www.hoverclubofamerica.org/forum/index.php?showtopic=2063&st=15
    [/QUOTE]

    Back to T-Craft:

    A large SES mothership (Harrier's and helio's on roof) with six or so LCAC sized hovercraft below might be a nice alternate.
     
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