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  • #91
    Originally posted by C. Beaty View Post
    And Vance, I’ll bet you mistakenly believed that the high rearward stick force required by your Sportcopter rotrblades was the result of low drag rather than a negative ptching moment.
    I have learned a lot from you Chuck and appreciate your efforts to educate the less educated.

    In this case you are wrong Chuck; I just believed the Sport Rotors needed more trim spring than the RAF blades that The Predator came with.

    The why of it was not very important to me because I felt at the time Sport Rotors or RAF blades were my two choices for a 1,400 pound machine.

    My RAF blades had cracks in the trailing edge and I did not care for the hub bar.

    The goal became make the Sport Rotors work as nicely as practical.

    I continue to be pleased with my Sport Rotors.

    The why of things is interesting to me and that is part of why I am so attentive to your posts. I have also listened to my friend Jonnie Ham many times at great length about how a gyroplane rotor works.

    Johnnie Ham was born in Lancaster, California, and attended the United States Military Academy at West Point. After completing initial tours of duty in Army Aviation in Command and Staff roles, he then attended Georgia Tech, where he received a Master of Science in AeroSpace Engineering and then attended the United States Naval Test Pilot School at Patuxent River, Maryland. He was assigned as an Experimental Test Pilot at Edwards AFB serving on the RAH66 Comanche Flight Test Team, and as Director of Operations.

    I also spent a lot of hours learning from Martin Hollmann before his passing. I know you knew Martin.

    I feel fortunate to know you.

    I don't have the knowledge base or education to discuss gyroplanes on your level.

    I do have a sense of what works and what doesn’t.
    Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

    Comment


    • #92
      Originally posted by Vance View Post
      I also spent a lot of hours learning from Martin Hollmann before his passing. I know you knew Martin.
      I knew Martin Hollmann very well; he actually had a degree in aeronautical engineering and worked for Martin Aircraft in Orlando.

      Whenever he was in Tampa, he’d stop by my office and argue about rotors, unable to grasp the fact that rotors don’t actually flap, simply rotating about a different axis from the rotorhead axis and producing the illusion of flapping.

      When I first showed up at a flyin with a hingeless, floating hub 3-blade rotor and had fired up for the initial flight; Martin gathered up an audience and was explaining to them how it was going to fling itself asunder from lack of drag hinges just as I went motoring sedately past. That was related to me by someone who was present in Martin’s audience.

      Martin’s problem was that he was living in the shadow of his father’s fame, a famous physicist before WWII who had developed an early multi-cavity magnetron and was a radar pioneer in Germany: Hans Hollmann.


      Comment


      • #93
        Originally posted by C. Beaty View Post
        No one has criticized Averso rotor blades, Vance. The intent was to correct the misconception about the effects of rotor blade inertia.

        Professionally designed rotor blades have zero pitching moment coefficients with chordwise CG located on the aerodynamic centers whether gyroplane or helicopter, beginning with Juan de la Cierva. If high inertia is required, and it generally is for helicopters, it is always by the use of tip weights because of the weight saving as opposed to uniformly heavy rotor blades.

        But even Cierva goofed; early C-30s used rotor blades with a negative pitching moment that resulted in at least one fatality.
        I for sure thought and nothing seemed to suggest otherwise that you were absolutely cutting Averso Stella rotors to size and equating their behavior with Skywheels and having been in the gyroplane with both of them side by side on the same day, I couldn't have disagreed more. So far my and Greg's feeling is that overall Averso Stella are the best rotors that work with AR-1 and despite our efforts we have not been able to find a better choice. The proof of the pudding is in the eating, all theories aside. We are working with some rotor manufacturer to offer the choice of composite rotors to our customers who want composite rotors but they have to match or better Averso Stella overall for us to put a stamp of approval on them and it is not easy or simple.

        Comment


        • #94
          As i’ve said repeatedly, owners of light weight gyros raved about the ‘hang’ time of Skywheels rotors, mistakenly believing it was the result of high ‘inertia’.

          I also recently posted comments about how Skywheels would suddenly and unpredictably do a violent midair flare on a Dreadhaught class gyro, referring to my encounter with CFI Steve McGowan’s Mazda rotary powered Parson’s Trainer some ~20 years ago.

          And of course the angle of attack instability of tail heavy Skywheels shows up on light weight gyros, causing noseup pitching during upward gusts but owners passed that off as “high lift”.


          Last edited by C. Beaty; 03-10-2018, 05:43 PM.

          Comment


          • #95
            Originally posted by C. Beaty View Post
            As i’ve said repeatedly, owners of light weight gyros raved about the ‘hang’ time of Skywheels rotors, mistakenly believing it was the result of high ‘inertia’.

            I also recently posted comments about how Skywheels would suddenly and unpredictably do a violent midair flare on a Dreadhaught class gyro, referring to my encounter with CFI Steve McGowan’s Mazda rotary powered Parson’s Trainer some ~20 years ago.

            And of course the angle of attack instability of tail heavy Skywheels shows up on light weight gyros, causing noseup pitching during upward gusts but owners passed that off as “high lift”.

            I got that and I told you its because they are made like a flex noodles not maintaining any shape in chord twist or span wise. Even Dragon wings the way they are constructed if taken to 8.5 chord will do weird stuff because their rigidity would be too compromised to maintain stable airfoil and stable angle of attack. Try it even with Dragon Wing airfoil and construction method and tell me what you find. This is no different than what we find in airplane wings not structurally engineered properly and that do not pass the load tests for torsional rigidity. In flight tests they are divergent as one goes faster and faster.
            Has there ever been a light Dragon wing blades for 8 inch plus chord? Does anyone have any experience with any of them. I heard they were tried once some years back and put the fear of God in the customer. I would bet they were divergent as well. Can't make them without torsional rigidity and control to keep the right shape while flying..
            I will try and verify your theory of this "collective pitch effect" on landing with direct measurement of G and rotor RPM and let you know how much is really that giving us the hang time and how much is "NOT" that or is inertia of high inertia rotors.
            You have given me no sound explanation of why Magni which you say is nose heavy rotor also has significant hang time compared to low inertia Dragon wings, both I have first hand flight experience in as well as in Averso of course. Things have to add up correctly if your theory is to hold.
            You say high inertia rotors on flare will fall through because they will not increase RRPM. Well they don't on Magni. You say Averso Stella don't increase RRPM but don't fall through because of this "collective pitch effect" because they are tail heavy. Ok will see for sure. Your theory basically says Dragon wings should have hang time because they increase RRPM because they are low inertia and not fall through. Well Dragon wings with light inertia don't hold a candle in the respect of hang time to Averso Stella or Magni rotors. Your theory and statements are not adding up in real life to me. I am sorry. Something is very much missing.
            Last edited by fara; 03-10-2018, 07:35 PM.

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            • #96
              The basic problem with Skywheels was the result of tail heaviness; torsionally stiffening them via a honeycomb core would delay the onset of divergence but would not eliminate it.

              What is so strange about correct chordwise CG location?

              Flexibility in a flapwise direction is necessary for durability.

              Comment


              • #97
                Hobbycopters have always been an undertaking largely the domain of by guess and by gosh designers and make believe engineers.

                The currently popular Eurotub style was originated by Vittorio Magni, a helicopter mechanic who learned how to design gyros from having built a Bensen. Magni purchased a license for the blades and rotorhead of his gyro from Jukka Tervanaki, a real engineer who had interned at Bensen.

                Magni’s low slung Italian sports car styling converted a flying lawn chair into something that many people found attractive.

                The Spanish firm ELA produced a copy of a Magni and raised the seating position in an effort to decrease the CG/thrustline offset.

                The German firm AutoGyro built ELAs under license for several years until going off on their own.

                There have been a number of copies of AutoGyro designs but they’re all about the same.

                The lesson is that when copying someone else’s design, copy something that is already commercially successful.

                It is all the fault of Igor Bensen, an engineer at GE who started it all, playing with a British Rotachute.

                Comment


                • #98
                  Originally posted by fara View Post
                  Any thoughts about why Magni rotors that are nose heavy have way better hang time than say something like Dragon wings? That is the other puzzle that can't explained with this theory.
                  I have no idea, Abid. I have no quantified data of the feel of landing ease of one rotor over another. In my humble opinion, three things work here:
                  - rotary inertia
                  - collective pitch effect by heavy tail
                  - low pitch setting for keep rotative energy more longtime

                  Comment


                  • #99
                    Actually Jukka designed, the MT-7 for magni in the mid 80'S,he also was the one that tried to sell the fact that the lack of a tail section was the instability problem not

                    the high thrust line,of course here in this country nobody listened, Magni did and the rest or Europe also did,so all of the really good gyros were

                    made in Europe until the AR line of gyros came into being here in this country. It appears that Abid has payed attention and has produced a line of Gyros that

                    have raised the standard in quality,flight performance and handling. I personally will never have the money for one of his machines but that wont keep me from

                    admiring them.
                    Best Regards,
                    Eddie Sigman,Polvadera,nm
                    (575) 835-4921

                    Comment


                    • Originally posted by C. Beaty View Post
                      The basic problem with Skywheels was the result of tail heaviness; torsionally stiffening them via a honeycomb core would delay the onset of divergence but would not eliminate it.

                      What is so strange about correct chordwise CG location?

                      Flexibility in a flapwise direction is necessary for durability.
                      Well yeah. Of course beyond a certain speed every airplane will also be divergent because many high performing fast airplanes have pretty good pitching moment on their wings and the tail is designed to balance that to a certain point. Design and construction always has a criteria and specs to stay within and beyond those, they can all behave erratically. Goes without saying.

                      Flexibility in span is ok but not like what Skywheels have. Have you ever put an assembled set of large Skywheels on saw horses and seen them droop. They are way beyond AutoGyro, Averso, Magni and many other rotors of similar span.

                      Comment


                      • Originally posted by Jean Claude View Post
                        I have no idea, Abid. I have no quantified data of the feel of landing ease of one rotor over another. In my humble opinion, three things work here:
                        - rotary inertia
                        - collective pitch effect by heavy tail
                        - low pitch setting for keep rotative energy more longtime
                        Hi JC:
                        I agree on your points. I believe its a combination of all three effects. I have asked Matt at MGL to design me a screen for iEFIS which just shows G and Rotor RPM. I will try and use that to see what I can find with Averso rotors. It would be very interesting for me to know.

                        Comment


                        • The late Ken Brock performed some tests for the Navy (Marines?) regarding gyro performance. Ken equipped his KB-2 with a recording G meter and did everything he could to try to achieve 2 Gs for them. Ken told me that it was impossible to pull 2 Gs with a gyro. One of the military's tests involved a CH53 Sea Stallion Sikorsky tailing Ken's gyro. On a command, Ken was to pull the stick back as hard as he dare. Ken said the Sikorsky's pilots were panic stricken as Ken disappeared from sight and feared his rapid climb would yield a more rapid descent into their massive rotors.
                          Tom Milton, PRA Director, Need a DAR, Seat tank, Prerotator, Rotor Brake, or Rotor Tach?
                          Have Airworthiness Certification questions?
                          gyroplanes@aol.com or
                          Visit www.calumetair.com

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                          • I heard the new about DWs. BUT!!!....

                            I'm selling my 23' Dragon Wing Rotors. New, in-crate...never been removed from the box. I am selling out my project for another project :)

                            Link below to other thread. Must go! At a nice price :)
                            I am selling my 23' Dragon Wing Rotors I bought several years ago from Rotor Flight Dynamics. New in-crate, never been used, never removed from crate. Mint
                            BW
                            PPL-ASEL; SP-Gyroplane
                            Pace, Florida

                            Maule MT7-235 (N235)
                            Got STOL?

                            RAF 2000 GTX SE FI (N429RK) Sold 2014
                            Stabilator/Stability Dust

                            Building the GENESIS G1sa - Aviomania

                            YouTube Videos

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                            • This and that:

                              Jim Vanek has, I believe, reported results from a recording G-meter of something near 4G's at the entry to a loop. This, if accurate, must represent a momentary figure; a jolt in lift brought about solely by the sudden increase in blade angle of attack that occurs with an increase in disk angle of attack. Once the rotor reacts by changing RPM, it's probably not possible for the rotor to continue making 3+G's in a steady state; tip speed just won't allow it.

                              McCutchens may be more flexible spanwise (i.e. droopy) than most metal blades, but they are concrete planks compared to the old Bensen wood blades. The woodies behaved as if made of rope. Their metal spars were merely 1/8" thick full-span straps of mild steel. Yet they flew quite nicely, were entirely stable and even made an entertaining screechy whistle as the air blew over the hollow nose weights. Wood and steel both have far better fatigue characteristics than aluminum.

                              Fiberglass is, in effect, synthetic wood -- both are composites consisting of a bundle of limber fibers held together with glue (in wood, the fibers are cellulose and the glue is lignin). Both materials are extremely limber, but relatively strong in tension, as a consequence of this basic make-up.

                              Like any wooden object, wood blades were sensitive to impacts and moisture.

                              Comment


                              • Mr.Riley, I have to say your insights and experience have always astounded me. I would like your take on the blades that Ken Wallis made and how they weather time. I'm sure you've made comment here in the past, but I'm nowhere up to speed on this new platform.
                                Jim Friend

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