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new guy with some performance questions

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  • artic_knight31337
    ok for a lack of better knowledge im going to use analogies from a airplane in motion as the air strikes from head on. ok im looking at the props and mostly im
    Message 1 of 9 , Dec 5, 2006
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      ok for a lack of better knowledge im going to use analogies from a
      airplane in motion as the air strikes from head on.

      ok im looking at the props and mostly im noticing props like on the
      front of a plane, where the airfoil is on the front im guessing
      however doesnt the raised edge or airfoil generate the lift? shouldnt
      it take a more lift giving position like the wings of an airplane?

      im no rocket scientist obviously since im on this list but it just
      seemed like common sense...

      anywho i also wanted to question the rotor you have pictured on the
      front of this group vs a more traditional magnet inside a ring of
      coils, or electric motor version. which would me more effecient? and
      is there really any difference in how you work the magnets and coils?
      perhaps have 3 coils in the center with a ring of magnets or just do
      it the way pictured,..

      sorry if this is slightly annoying, i just figure anything worth
      making is worth making well. and if this is off topic i'll stop :)
    • Steve Spence
      http://www.nrel.gov/learning/re_wind.html A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side
      Message 2 of 9 , Dec 6, 2006
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        A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
         
        Blade design calculator
         

        Steve Spence
        Director, Green-Trust
        http://www.green-trust.org

         


        From: axialflux@yahoogroups.com [mailto:axialflux@yahoogroups.com] On Behalf Of artic_knight31337
        Sent: Wednesday, December 06, 2006 1:37 AM
        To: axialflux@yahoogroups.com
        Subject: [axialflux] new guy with some performance questions

        ok for a lack of better knowledge im going to use analogies from a
        airplane in motion as the air strikes from head on.

        ok im looking at the props and mostly im noticing props like on the
        front of a plane, where the airfoil is on the front im guessing
        however doesnt the raised edge or airfoil generate the lift? shouldnt
        it take a more lift giving position like the wings of an airplane?

        im no rocket scientist obviously since im on this list but it just
        seemed like common sense...

        anywho i also wanted to question the rotor you have pictured on the
        front of this group vs a more traditional magnet inside a ring of
        coils, or electric motor version. which would me more effecient? and
        is there really any difference in how you work the magnets and coils?
        perhaps have 3 coils in the center with a ring of magnets or just do
        it the way pictured,..

        sorry if this is slightly annoying, i just figure anything worth
        making is worth making well. and if this is off topic i'll stop :)



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        This message was checked by NOD32 antivirus system.
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      • artic_knight31337
        -snip- ... pocket of ... low-pressure ... turn. This ... ok lets assume this D is a wing, and that curve side (even tho the curve isnt right) is the lift side,
        Message 3 of 9 , Dec 6, 2006
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          -snip-
          > A blade acts much like an airplane wing. When the wind blows, a
          pocket of
          > low-pressure air forms on the downwind side of the blade. The
          low-pressure
          > air pocket then pulls the blade toward it, causing the rotor to
          turn. This
          > is called lift.

          ok lets assume this D is a wing, and that curve side (even tho the
          curve isnt right) is the lift side, now of the wing is facing wind
          like this
          D <-wind- then its not gonna make much lift is it? but most of the
          designs i see is almost like that, they twist the wing a bit, why not
          make the wing so the curve faces up and down? so it maximizes the
          winds force? like this ^ <-wind-

          i dont know a whole lot of fluid dynamics but just what ive seen its
          kinda..... funny for these props to be as they are.
        • Michael Vanecek
          Don t forget that this wing is traveling and the angle of attack takes this into account. It s not just wind flat onto the wing, but wind forming lift on a
          Message 4 of 9 , Dec 6, 2006
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            Don't forget that this wing is traveling and the angle of attack takes
            this into account. It's not just wind flat onto the wing, but wind
            forming lift on a moving object, much like a sail. As it gets to speed,
            the current configuration is pretty much optimal for the ideal angle of
            attack.

            Be well,
            Mike
            --
            Zone 8, Texas
            http://www.taroandti.com/ Exotic Plants and More...
            http://www.mjv.com/ Home...


            artic_knight31337 wrote:

            > ok lets assume this D is a wing, and that curve side (even tho the
            > curve isnt right) is the lift side, now of the wing is facing wind
            > like this
            > D <-wind- then its not gonna make much lift is it? but most of the
            > designs i see is almost like that, they twist the wing a bit, why not
            > make the wing so the curve faces up and down? so it maximizes the
            > winds force? like this ^ <-wind-
            >
            > i dont know a whole lot of fluid dynamics but just what ive seen its
            > kinda..... funny for these props to be as they are.
            >
            >
          • Kirk McLoren
            Because it has been proven it is the deflection that drives it not Bernoulli forces. Hasnt changed the textbooks tho. I have a model I am building of a drag
            Message 5 of 9 , Dec 6, 2006
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              Because it has been proven it is the deflection that drives it not Bernoulli forces. Hasnt changed the textbooks tho.
              I have a model I am building of a drag windmill. Will get it online in the newyear. Self furling and probably the cheapest possible design horsepower per $.
              That is the bottom line most of the time.
               
              Kirk

              artic_knight31337 <artic_knight31337@...> wrote:
              -snip-
              > A blade acts much like an airplane wing. When the wind blows, a
              pocket of
              > low-pressure air forms on the downwind side of the blade. The
              low-pressure
              > air pocket then pulls the blade toward it, causing the rotor to
              turn. This
              > is called lift.

              ok lets assume this D is a wing, and that curve side (even tho the
              curve isnt right) is the lift side, now of the wing is facing wind
              like this
              D <-wind- then its not gonna make much lift is it? but most of the
              designs i see is almost like that, they twist the wing a bit, why not
              make the wing so the curve faces up and down? so it maximizes the
              winds force? like this ^ <-wind-

              i dont know a whole lot of fluid dynamics but just what ive seen its
              kinda..... funny for these props to be as they are.



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            • Kirk McLoren
              Steve do you have the calculator? If so what are the ballpark numbers for output for a swept area of 100 square feet in 30 mph wind? Kirk Steve Spence
              Message 6 of 9 , Dec 6, 2006
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                Steve do you have the calculator?
                 
                If so what are the ballpark numbers for output  for a swept area of 100 square feet in 30 mph wind?
                 
                Kirk

                Steve Spence <sspence@...> wrote:
                A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
                 
                Blade design calculator
                 
                Steve Spence
                Director, Green-Trust
                http://www.green-trust.org
                 


                From: axialflux@yahoogroups.com [mailto:axialflux@yahoogroups.com] On Behalf Of artic_knight31337
                Sent: Wednesday, December 06, 2006 1:37 AM
                To: axialflux@yahoogroups.com
                Subject: [axialflux] new guy with some performance questions

                ok for a lack of better knowledge im going to use analogies from a
                airplane in motion as the air strikes from head on.

                ok im looking at the props and mostly im noticing props like on the
                front of a plane, where the airfoil is on the front im guessing
                however doesnt the raised edge or airfoil generate the lift? shouldnt
                it take a more lift giving position like the wings of an airplane?

                im no rocket scientist obviously since im on this list but it just
                seemed like common sense...

                anywho i also wanted to question the rotor you have pictured on the
                front of this group vs a more traditional magnet inside a ring of
                coils, or electric motor version. which would me more effecient? and
                is there really any difference in how you work the magnets and coils?
                perhaps have 3 coils in the center with a ring of magnets or just do
                it the way pictured,..

                sorry if this is slightly annoying, i just figure anything worth
                making is worth making well. and if this is off topic i'll stop :)



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                This message was checked by NOD32 antivirus system.
                http://www.eset.com


                Need a quick answer? Get one in minutes from people who know. Ask your question on Yahoo! Answers.

              • Steve Spence
                http://www.otherpower.com/windbasics1.html Steve Spence Director, Green-Trust http://www.green-trust.org _____ From:
                Message 7 of 9 , Dec 6, 2006
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                  Steve Spence
                  Director, Green-Trust
                  http://www.green-trust.org

                   


                  From: axialflux@yahoogroups.com [mailto:axialflux@yahoogroups.com] On Behalf Of Kirk McLoren
                  Sent: Wednesday, December 06, 2006 3:11 PM
                  To: axialflux@yahoogroups.com
                  Subject: RE: [axialflux] new guy with some performance questions

                  Steve do you have the calculator?
                   
                  If so what are the ballpark numbers for output  for a swept area of 100 square feet in 30 mph wind?
                   
                  Kirk

                  Steve Spence <sspence@green- trust.org> wrote:
                  A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
                   
                  Blade design calculator
                   
                  Steve Spence
                  Director, Green-Trust
                  http://www.green- trust.org
                   


                  From: axialflux@yahoogrou ps.com [mailto:axialflux@ yahoogroups. com] On Behalf Of artic_knight31337
                  Sent: Wednesday, December 06, 2006 1:37 AM
                  To: axialflux@yahoogrou ps.com
                  Subject: [axialflux] new guy with some performance questions

                  ok for a lack of better knowledge im going to use analogies from a
                  airplane in motion as the air strikes from head on.

                  ok im looking at the props and mostly im noticing props like on the
                  front of a plane, where the airfoil is on the front im guessing
                  however doesnt the raised edge or airfoil generate the lift? shouldnt
                  it take a more lift giving position like the wings of an airplane?

                  im no rocket scientist obviously since im on this list but it just
                  seemed like common sense...

                  anywho i also wanted to question the rotor you have pictured on the
                  front of this group vs a more traditional magnet inside a ring of
                  coils, or electric motor version. which would me more effecient? and
                  is there really any difference in how you work the magnets and coils?
                  perhaps have 3 coils in the center with a ring of magnets or just do
                  it the way pictured,..

                  sorry if this is slightly annoying, i just figure anything worth
                  making is worth making well. and if this is off topic i'll stop :)



                  __________ NOD32 1904 (20061206) Information __________

                  This message was checked by NOD32 antivirus system.
                  http://www.eset. com


                  Need a quick answer? Get one in minutes from people who know. Ask your question on Yahoo! Answers.



                  __________ NOD32 1905 (20061206) Information __________

                  This message was checked by NOD32 antivirus system.
                  http://www.eset.com
                • Kirk McLoren
                  I was curious what % of Betz the program assumed for airfoil efficiency. A preliminary penciling from your url shows my drag windmill to be right up there. I
                  Message 8 of 9 , Dec 6, 2006
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                    I was curious what % of Betz the program assumed for airfoil efficiency.
                    A preliminary penciling from your url shows my drag windmill to be right up there. I always assumed airfoils were much better performers than drag. I guess not looking at your numbers.
                     
                    Kirk

                    Steve Spence <sspence@...> wrote:
                     
                    Steve Spence
                    Director, Green-Trust
                    http://www.green-trust.org
                     


                    From: axialflux@yahoogroups.com [mailto:axialflux@yahoogroups.com] On Behalf Of Kirk McLoren
                    Sent: Wednesday, December 06, 2006 3:11 PM
                    To: axialflux@yahoogroups.com
                    Subject: RE: [axialflux] new guy with some performance questions

                    Steve do you have the calculator?
                     
                    If so what are the ballpark numbers for output  for a swept area of 100 square feet in 30 mph wind?
                     
                    Kirk

                    Steve Spence <sspence@green- trust.org> wrote:
                    A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
                     
                    Blade design calculator
                     
                    Steve Spence
                    Director, Green-Trust
                    http://www.green- trust.org
                     


                    From: axialflux@yahoogrou ps.com [mailto:axialflux@ yahoogroups. com] On Behalf Of artic_knight31337
                    Sent: Wednesday, December 06, 2006 1:37 AM
                    To: axialflux@yahoogrou ps.com
                    Subject: [axialflux] new guy with some performance questions

                    ok for a lack of better knowledge im going to use analogies from a
                    airplane in motion as the air strikes from head on.

                    ok im looking at the props and mostly im noticing props like on the
                    front of a plane, where the airfoil is on the front im guessing
                    however doesnt the raised edge or airfoil generate the lift? shouldnt
                    it take a more lift giving position like the wings of an airplane?

                    im no rocket scientist obviously since im on this list but it just
                    seemed like common sense...

                    anywho i also wanted to question the rotor you have pictured on the
                    front of this group vs a more traditional magnet inside a ring of
                    coils, or electric motor version. which would me more effecient? and
                    is there really any difference in how you work the magnets and coils?
                    perhaps have 3 coils in the center with a ring of magnets or just do
                    it the way pictured,..

                    sorry if this is slightly annoying, i just figure anything worth
                    making is worth making well. and if this is off topic i'll stop :)



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                    This message was checked by NOD32 antivirus system.
                    http://www.eset. com


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                  • Tom Visel
                    The reason for the twist (on more optimized props) is due to relative velocity. For a given shaft speed, the root of the blade is traveling more slowly than
                    Message 9 of 9 , Dec 6, 2006
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                      The reason for the twist (on more optimized props) is due to relative velocity.  For a given shaft speed, the root of the blade is traveling more slowly than the tip.  Since the whole blade hits the same "chunk" of wind at the same time, this means that a blade with only one angle of attack will be less than ideal aerodynamically all down its length.  In addition the root also needs to flex less, and carry more torque than the tip.  With these three things (and many others) varying down the length of the blade, a smoothly changing cross section is appropriate to match the load and angle of incidence, as well as the structural properties of the prop material(s).

                      Or you could just not sweat it, settle for less-than-ideal efficiency and grab an off-the-shelf design.  Odds are something else will steal the 2% extra efficiency you might have found with a "perfect" prop anyway.

                      TomV

                      Michael Vanecek wrote:
                      Don't forget that this wing is traveling and the angle of attack takes 
                      this into account. It's not just wind flat onto the wing, but wind 
                      forming lift on a moving object, much like a sail. As it gets to speed, 
                      the current configuration is pretty much optimal for the ideal angle of 
                      attack.
                      
                      Be well,
                      Mike
                      --
                      Zone 8, Texas
                      http://www.taroandti.com/ Exotic Plants and More...
                      http://www.mjv.com/ Home...
                      
                      
                      artic_knight31337 wrote:
                      
                        
                      ok lets assume this D is a wing, and that curve side (even tho the
                      curve isnt right) is the lift side, now of the wing is facing wind
                      like this 
                       D <-wind-  then its not gonna make much lift is it? but most of the
                      designs i see is almost like that, they twist the wing a bit, why not
                      make the wing so the curve faces up and down? so it maximizes the
                      winds force? like this ^ <-wind-
                      
                      i dont know a whole lot of fluid dynamics but just what ive seen its
                      kinda..... funny for these props to be as they are.
                      
                      
                          
                      
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