Benelli lift theory under question

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

  1. daiquiri
    Joined: May 2004
    Posts: 5,373
    Likes: 255, Points: 93, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Helicopters or discussions like this one? :p
     
  2. Frosty

    Frosty Previous Member

    A fair assessment ---you think/

    Do you really think that I have to sit back and not make a reply to his 4th posts of insults. If PAR does not like this thread and or my level of intelligence why is he here. PAR is till seathing with anger because he did not know how to fit a marine fuel pump and the bafoon did.


    You may consider your welcome in a similar manner.

    Number 4 I am a very unintelligent person apparently so il'le not reply to your post of helicopter blades reaching the speed of sound. As a baffoon I have no credibility so ille leave it to someone else to correct you
     
  3. El_Guero

    El_Guero Previous Member

  4. El_Guero

    El_Guero Previous Member

    From: www.grc.nasa.gov/WWW/k-12/airplane/wrong1.html

    Next, he will convince himself he can fly a helicopter upside down, just because he saw an airplane fly upside down.
     
  5. Number4

    Number4 Previous Member

    Hi Frosty,
    It is not usual, I did say MAY. But a big rig like a Chinook flying in very cold air and it's blade tips will be just supersonic.
    Don't forget, wings and props are accelerating air. The blade does not actualy have to be going faster than sound to make some of the air around it flow supersonicaly.
    The link and cutting I have posted below, I am not entirely sure it is correct. I was told the same thing, and believed it until today. I think the blades are at 0.9 Mach or below, and as a huey makes an incredible racket all the time, it may be something else. Thanks to this thread I have learned something new!
    Best Wishes,
    Adam


    http://www.century-of-flight.net/Aviation history/helicopter history/Bell UH-1 Huey.htm
    "Bell UH-1 "Huey"

    The most famous helicopter in the world is the Bell UH-1 Iroquois, most commonly referred to as the "Huey." The Huey, which first flew in 1956, serves in front-line service in the U.S. military and the militaries of many nations and will continue to do so for many years to come. It earned its fame during the Vietnam War and has been featured in many war movies, including Apocalypse Now and Platoon, as well as in numerous action adventure films.

    The Huey has several distinctive characteristics, including its rounded nose, its twin-bladed rotor, and the loud "whomp whomp" sound it makes in flight. It is a particularly noisy helicopter because, when in forward flight, the tip of the advancing rotor blade breaks the speed of sound, creating a small sonic boom."
     
  6. Number4

    Number4 Previous Member

    Hi El_Guero,
    If you could reverse the pitch of the main rotors then there is no reason why a modified helicopter could not fly upside down.
     
  7. Frosty

    Frosty Previous Member

    QUOTE=Number4;

    The Huey has several distinctive characteristics, including its rounded nose, its twin-bladed rotor, and the loud "whomp whomp" sound it makes in flight. It is a particularly noisy helicopter because, when in forward flight, the tip of the advancing rotor blade breaks the speed of sound, creating a small sonic boom." /QUOTE



    Rubbish. But what do I know.
     
  8. Number4

    Number4 Previous Member

    Hi Frosty old chap,
    Huey Rotor Diameter 14.63metres
    Rotor RPM = 300
    Rotating Tip speed (relative to airframe)= 230 m/s
    Top Speed (Airframe) = 70 m/s
    Total tip speed ( rotor 90' to airframe, forward cycle)= 300 m/s
    Speed of sound at -50,C = 300m/s
    Tip speed = Mach 1

    Supersonic flow may begin, for an unswept wing, at Mach 0.7

    The entire wing is not supersonic, but a shock wave will begin to form over the thickest point of the aerofoil.

    So on a normal warm day, at sea level, a Huey will begin to create supersonic flow at 0 mph and 300rpm.

    Amongst other things, you are listening to two shock waves increasing and decreasing in amplitude as they circle the hub.

    Best Wishes,
    Adam

    P.S. WHOMP WHOMP WHOMP WHOMP WHOMP
    P.P.S. I think I will watch Apocalypse Now now.
    P.P.P.S. I did!
     
  9. El_Guero

    El_Guero Previous Member

    Frosty,

    You chose to publish a statement in a field you knew little about.

    Go out and google. There are some GREAT kit builders and designers who have a lot of data on their websites about airfoils and lift.

    http://www.vansaircraft.com/pdf/hp_limts.pdf This is a great read. Might be a little steep for you, but keep reading. You will get it over time.

    Regards,

    Wayne
     
  10. El_Guero

    El_Guero Previous Member

    Adam,

    Supersonic flow is not supersonic.

    Regards,

    Wayne
     
  11. El_Guero

    El_Guero Previous Member

    You guys?

    I got a -5 reputation point hit .... I ticked someone off and they went around and made a positive like me negative ....

    Oh well.

    Let's see if I can score a negative 273 a second time in life.

    :cool:
     
  12. Number4

    Number4 Previous Member

    Please elaborate El Guero,
    To me, what you have written is
    "Black Paint is not black."
    Please tell me how something can be supersonic, and not, at the same time?
     
  13. murdomack
    Joined: Jun 2007
    Posts: 309
    Likes: 23, Points: 18, Legacy Rep: 282
    Location: Glasgow

    murdomack New Member

  14. Frosty

    Frosty Previous Member

    Yes thats correct and thats when massive drag occurrs and the wing becomes unstable .. Helicoptor rotors can not exceed the speed of sound..

    Your source of knowledge is interesting. Flying in a choppper does not necessarily make you a chopper engineer or watching war movies.

    Where else is your knowldege derived,--Mary Poppins?

    EL-- From where is you information that this is not my feild--was that on google too? El---I should at this point welcome you to the forum but after just 2 weeks we see a character never seen before.

    One day you will wander into my field and maybe we might see yours but this is obviously not it.
     

  15. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    What's your rate Frosty? I'm just an single engine IFR guy, but hey, you might be experienced, though judging by your assertions, which are typical throughout this thread, you're talking out your butt again. Yes, chopper rotors do exceed the sound barrier, but without the very things I've suggested you don't have, also throughout this thread, you couldn't possably know this. In fact, I question if you even realize we're in the 21st century now, as your posts/experience levels indicate you're firmly and begrudgingly planted in the 70's. Still got your tight curl perm do you?
     
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