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Cyclic Trim Drag

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  • dave santos
    Trim Drag is the performance penalty exacted any time an aircraft acts to change attitude or maintain stability. Its drag both in the traditional aerodynamic
    Message 1 of 4 , Feb 3, 2011
      Trim Drag is the performance penalty exacted any time an aircraft acts to change attitude or maintain stability. Its drag both in the traditional aerodynamic sense & also the energetic cost of actuation. High performance aircraft maneuvering aggressively are most prone to excessive trim drag. A major aerodynamic trade-off to all our looping kiteplanes & autogyros is Cyclic Trim Drag. The ideal condition is for correct cyclic trim to be passively sustained by an ideal resonance of the aerostructure. This is very hard still for most human designers, but common in biological systems.

      Add Cyclic Trim Drag to the set of drag effects to be accounted for in AWECS analysis.

    • Doug
      It s excruciating to watch the newbies drag themselves through 2000 years of wind turbine design, still stuck around 2000 years ago, trying to re-discover the
      Message 2 of 4 , Feb 4, 2011
        It's excruciating to watch the newbies drag themselves through 2000 years of wind turbine design, still stuck around 2000 years ago, trying to re-discover the basics...

        History of Wind Energy:
        1) I guess trim drag would be the drag of a kite having to steer itself in circles, when it COULD have just been attached at a central point (called a hub). Now you're up to 2000 years ago in the Greek Islands, where they had a ring of triangular kites or sails attached by sticks to a central hub.

        2) Then apply more kites to the struts til they are solid kite to the center, add airfoil profiles, and you have low aspect ratio (long) kites, and you're up to 1000 years ago in Europe.

        3) Lower the pitch and Harden them for long term, high-speed use and you're now at 100 years ago in Denmark and America, when we first started spinning generators.

        History of AWE:
        1) Imagine sails pulling upward, and you're up to where I was in the mid-late 1970s, until I read my first book on wind energy.

        2)Transition to cross-axis spinning rotors took place in the late 1970's as I began to comprehend the realities of wind energy. I quickly saw that a stack of spinning rotors would make more power while helping to lift itself, also providing steady-state rotation for spinning reserves, while remaining simple (1 moving part).

        3) Early 2000 decade: Patents filed

        4) Mid-2000 decade: Prototypes built and flown for Popular Science (PopSci Invention of the Year 2008), Discovery Channel, first AWE Conference...
      • dave santos
        Doug, Cyclic Trim Drag applies particularly to rotating/oscillating systems that must truly fly, especially highspeed kite designs like Kitelab Group,
        Message 3 of 4 , Feb 4, 2011
          Doug,

          Cyclic Trim Drag applies particularly to rotating/oscillating systems that must truly fly, especially highspeed kite designs like Kitelab Group, Ampyx, Joby Energy, & Makani Power. If the backyard turbine world you ably represent has explored this flight issue, thats cool.

          The Super Turbine (R) hides its inherent "worst-case" out-of-trim condition (no blade hinges like a SkyMill autogyro) in its unimpressive stream-tube efficiency. There is also the unique Trim Drag of the thick  "rotating tower" angled down to windward, which requires extra lift to overcome (nevermind the excessive weight of flying a tower).

          Do not despair over your "newbie" status in Aerospace (& Aviation generally); its only "excruciating" if you fail to master the basics. Start with key parameters like Power-to-Weight & work your way up to narrower issues like Cyclic Trim Drag. Dave Lang recently took the trouble to pose to you some nice simple beginner questions that will help you progress, if you answer them carefully,

          daveS


           

        • Doug
          Dave S. My designs and patents DO include tilting hubs. I guess to know that you d have to be up to speed on them. OK what questions by Dave Lang are you
          Message 4 of 4 , Feb 6, 2011
            Dave S.
            My designs and patents DO include tilting hubs. I guess to know that you'd have to be up to speed on them.
            OK what questions by Dave Lang are you talking about? Can you re-post these questions please?

            My main point is this: after 10 years of fielding virtually identical posts on the "real" wind energy lists, for virtually identical machines, using identical "theories of operation" as those posted here, I recognize the ones that work as opposed to the complete nonsense ones.

            The stuff you talk about is as far into the complete nonsense as anything I've ever seen. The problem is this: As long as it is a battle of mere words, your words are equal to anyone's and there's no good way (for the average reader) to determine if your words represent the next breakthrough, a superior solution, or complete nonsense.

            It really IS just like when the religious nuts show up at your door: they will ALWAYS be "100% right" in EVERYTHING they say. if you disagree, you are "bad". And at some point you realize they can never, and will never, make any sense, they don't in fact WANT to make any sense, making sense is not what they are about, and you must find a way to politely (or not) say buh-bye and get on with reality.

            In wind energy, the crackpot-ism starts with lift-based vertical-axis machines like the Darrieus, proven to make less power using more materials less reliably, and goes down from there, to the drag-based vertical-axis machines, and finally to shrouded, drag-based vertical-axis machines.

            By that point you are usually listening to claims about 100 times the reality, say a 4-foot machine on your roof eliminating your electric bill.

            These roof-mounted 100% solidity machines are usually promoted for about 2 years before they finally go through the bothersome and irrelevant (to them) step of attaching a generator, whereupon they go through a few generators, cursing the fact that their machine cannot even turn one, blaming each generator manufacturer in turn until they finally give up or are driven bankrupt and taken to court by investors and state attorneys general.

            Down on the totem-pole even from there are the people promoting oscillating cycles, ribbon working surfaces, spiral working surfaces, etc. These are the ones perpetually stuck in the land of meaningless words with an occasional "breakthrough" press release. These are the ones with actually nothing to offer - not even a good hoax or ripoff, since they cannot even come up with a fake version that could convince anyone, let alone a working model.

            The bottom line in wind energy: There's ONE main determinant of whether any theory has legs, and it is called an electric meter. What does your electric meter tell us about your theories?
            Doug S.
            http://www.USWindlab.com/
            a wind-powered facility
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