Benelli lift theory under question

Discussion in 'All Things Boats & Boating' started by Frosty, Dec 5, 2012.

  1. Frosty

    Frosty Previous Member

    Good morning Par thanks again for an informative post. Never any input or help just publish your irrational hatred for ----well everything.

    You can not insult me --I have no respect for your words.

    You know where my expertise lies. This I agree is not . Are you saying I can not post about it.

    Since when did single IFR teach helicopter rotor speeds.

    Google it ---its there.

    I hate going to google but here you are. http://www.helicoptersmagazine.com/content/view/1388/59/



    Rotor can exceed mach but they go to a lot of trouble to stop it. Hence we have pretty much reached max Chopper speeds and are now going twin rotors which is not really new.
     
  2. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Wanna talk about helicopters, speed and the direction rotorcraft industry has undertaken? Then check out these:
    http://www.flightglobal.com/news/articles/sikorsky-x2-breaks-helicopter-speed-barrier-342211/
    http://phys.org/news/2011-05-eurocopter-x3-world-fastest-copter.html :)

    This article adresses the problem of tip speed and how did the Eurocopter resolve it for it's speed-record X3 helicopter:
    http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_07_09_2012_p64-472797.xml&p=1

    Two different ways of breaking speed barriers. Sikorsky has opted for slightly supersonic tip speeds, while Eurocopter relies on wings to unload the rotor and hence reduce rpms and keep the tip speed in the subsonic zone.
     
  3. Frosty

    Frosty Previous Member

    Thats a Hybrid its a helicopter at slow speed (subsonic ) and a plane at high speed.
     
  4. swabbie

    swabbie Previous Member

     
  5. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Theres not a wing effect craft in the world designed to take off with zero incidence foils - from Cessnas to Jets to Helicoptors.

    Its like the previous posts have re-iterated, BOTH effects are required for efficient flight.

    Frostys 'friend' isnt totally off the mark - its just the belief that its all angle of attack that does the job.



    Stop complaining about the thread Number4 - these discussions dont have to be angst filled, some people just enjoy "clarifying other peoples limitations" :)

    I guess all the other posters must enjoy braving the wrath of frustrated 'educators'
     
  6. tom kane
    Joined: Nov 2003
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    tom kane Senior Member

    A helicopter rotor blade with flat top and bottom surfaces works just fine as also does a propeller with constant angle from tip to hub. My mates used to spend hours tweaking their props and wings and they performed no better than my easy made basic jobs.
     
  7. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Helicopters can fly upside down. ridgid rotor ones .Here in New Zealand we use them to trim hedges and scrub on the hillside.
     
  8. Frosty

    Frosty Previous Member

    You can get negative pitch , when they land on a moving vessel they will select negative to hold it down. It might fly upside down if the mast was long enough and the blades could not reach the fuselage or the tail rotor.

    Some models have been made to.
     
  9. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Military helicopters have been doing upside down for years, but only for short periods.

    http://engineering.mit.edu/live/news/418-can-helicopters-fly-upside-down

    " To enable a commercial helicopter to fly upside down, manufacturers would need to make its rotor blades more rigid so as not to flex too close to the main body of the helicopter (otherwise they could rip off their own fuselage or other critical components). They would also need to redesign the joint that connects the rotor blades with the rest of the vehicle so it could bear the load of an upturned helicopter. Finally, they would need to develop new controls to allow the rotor blades to tilt downwards and reconfigure the engine so that fuel and lubricants could be distributed properly while the helicopter was inverted.

    Even without these changes, many of today’s helicopters can fly upside down for seconds at a time, notes Frazzoli. “Military and acrobatic helicopter pilots often perform loops and barrel rolls in which their vehicle momentarily flies upside down,” he says. “During that time, the rotor still generates thrust toward the top of the helicopter, so the pilot must maintain sufficient momentum and altitude to remain airborne.” "
     

    Attached Files:


  10. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    You are talking models no doubt.

    Real helicopters need much more finessing to be economical and professionally controllable.
     
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