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Re: Mothra Stack Dynamics and Operations ///Re: [AWES] mothra kite bunch

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  • dave santos
    The good news is that a vast wiggling stack of Mothras can have each kixel sweeping in its own well-scaled figure-of-eight pattern. So overall, the vast flying
    Message 1 of 16 , Nov 13, 2012
      The good news is that a vast wiggling stack of Mothras can have each kixel sweeping in its own well-scaled figure-of-eight pattern. So overall, the vast flying structure may look like its not sweeping much, but it is, at kixel scale. The line-velocity tapped at the bottom is close to the sweep-velocity of the kixels.

      There is confusion over the short-stroke/long-stroke issue, which was mostly a dimensional reeling question, where short-stroke race-car engines where a distant similarity-case. It has long been known to us that a short recovery phase is natural at the tops of power loops and eights, using just a bit of elastic-return force. This can be classed as a dimensionless "short"-stroke mode, without reels required.

      ----------------------------------

      Note that for Mothras, FAA Orange wing-tips with White center-wing aeria is looking like a better color scheme than alternating colors up and down the stack.

    • Pierre BENHAIEM
      In my sense realistic animation does not concern your work,Roddy,but the possibility to make a realistic animation with the scheme described by DaveS,which
      Message 2 of 16 , Nov 13, 2012


        In my sense "realistic animation" does not concern your work,Roddy,but the possibility to make a "realistic animation" with the scheme described by DaveS,which seems to be a little like Windbelt - Wikipedia, the free encyclopedia,but not quite since this scheme seems contain both torsion and short-stroke (note that torsion pushing farer becomes rotation).

         

        DaveS:if elasticity is an important parameter,should not be a membrane-shape more adapted to keep kinetic energy and high speed if it is possible?I dont see kites short-strokes in an other way than effective and recovery strokes where the average speed is low,the kite having not enough distance to accelerate,and where drag during recovery stroke stays (I dont see how it is possible to make energy);but if kites vibrations are really at high velocity,the ram air-mass you mention as advantageous can be a problem by preventing alternating motion.

         

        PierreB   

         

         


        > Message du 13/11/12 15:02
        > De : "Rod Read"
        > A : AirborneWindEnergy@yahoogroups.com
        > Copie à :
        > Objet : Re: Mothra Stack Dynamics and Operations ///Re: [AWES] mothra kite bunch
        >
        >  

        > Thanks for the argument points Pierre,
        >
        > Lack of area swept is definitely the problem with a wide arch tugging mechanism. This can probably be improved with narrower kite arches toward higher levels. They would sweep more for their area and be held more stable by the wide arch below. Also less likely to bowtie.
        >
        > If a large sinusoidal tugging force is used to overcome a recovery spring, The excess pull can extend the spring and generate whilst the recovery itself can also generate. I'm not yet sure how viable a hysteresis loop that is. You maybe have figures.
        >
        > As for a realistic animation, I'd have to buy more software in order to create kixel component roll relative to the loadpath. However if anyone has the relevant software and wants to use my 3d files, they will be online at kitepowercoop.org
        >
        >


        Rod Read
        >
        > 15a Aiginis
        > Isle of Lewis
        > HS2 0PB
        >
        > 07899057227
        > 01851 870878

        >
         

        >
        >
        >
        On 13 November 2012 00:12, Pierre BENHAIEM <pierre.benhaiem@...> wrote:
        >
         

        >

        >
        > Correction:"swept area roughly 15 km/1 km of kites (2 or 3 km/1 km)" instead "swept area of 6 or 7 Gm² (6000 km/1 km) of kites (1000 km/1 km)" too roughly. 

        >  

        > PierreB 
        >
        >
        >
        >

        > Message du 13/11/12 00:58
        > > De : "Pierre Benhaiem"
        > > A : AirborneWindEnergy@yahoogroups.com
        > > Copie à :
        > > Objet : Mothra Stack Dynamics and Operations  ///Re: [AWES] mothra kite bunch
        > >
        > >  

        > >

        > > DaveS,

        > > Some questions:are short-strokes involve effective and recovery strokes?If yes recovery short strokes should imply losses like long strokes.Are metachronic waves divided into antiplectic and symplectic waves?If yes how is it possible to control them?Can you provide calculations?(note:I know nothing about metachronic waves but it is not the only thing I dont know) Can you indicate how the generators work?Can Roddy provide a realistic animation of the set?

        > > In a recent post you indicate hundreds 50 m² kites.Nor "neutral-buoyant mass by carrying along internal air" is something like 10 m3; 200 (50m² kites) will be roughly 2500 kg for air,the same for materials.For MW-scale,it is neglectible.With 500 m² kites x 1000 (expected 1 GW for crosswind parafoils) air mass is roughly 100 tons,yet too low to take it into account. Morever mass is not energy,but in this case can be a small storage.But perhaps this mass helps for the complex motion you suggest.How does air-materials work? 

        > > Kites with L/D ratio is 1 like you indicate could provide something like 15% (in absolute or on Betz limit,I dont remenber) by going downwind.This small efficiency is probably at least lost during recovery stroke.If case of no loss,to obtain 1 GW you must have a swept area of 6 or 7 Gm² (6000 km/1 km) of kites (1000 km/1 km) with 15% solidity for example,very very roughly,and being very very optimist.Reel-out/in DougS critics (being right or wrong) looks very efficient beside.

        > > It looks like a non reasonable way for AWE (if AWE is a reasonable way for wind energy) unless important discoveries are made,implying Nobel prizes.

        > > PierreB 

        > >
        > >  
        > >

        > > --- In AirborneWindEnergy@yahoogroups.com, dave santos wrote:
        > > >
        > > >
        > > >
        > > > Exciting "Findings" about Rod's Stack of parafoil kixel Mothras-
        > > >
        > > > This sort of mega-stack could naturally oscillate in a twisting back-and-forth dance, aka "Dutch Roll". Its like a vast torsion-spring/mass* excited by the wind. An animation will be way-cool.
        > > > >
        > > > >
        > > > >Each parafoil kixel would dance its own little figure eight in local phase with the whole. Each kixel could be gangline controlled (trimmed or furled) by drawlines in the loadpath mesh, but the basic motion is passive. Each kixel could be constrained in three dimensions with the load[paths to resist fouling and recover from disturbance.
        > > > >
        > > > >
        > > > >The power signal is an opposed-phase sine-wave at each anchor-side sort of like a cardiac "lub-dub".
        > > > >
        > > > >
        > > > >Power would sum more-or-less linearly with kixel count, to fully load loadpaths. Gigawatt-scale is quite feasible.
        > > > >
        > > > >
        > > > >Launching would be a cascade in stages from top-to-bottom. Even if the stack lays off the wind axis, it will launch and self orient.
        > > > >
        > > > >
        > > > >Kill lines and furling would douse the stack. In a peak loadcase, one anchor-side can part passively, to autokill without runaway.
        > > > >
        > > > >
        > > > >Mothra's in the mega-stack should alternate FAA Orange and White, for maximum aviation conspicuity.
        > > > >
        > > > >
        > > > >A whipple-tree tackle can spread the massive static load along the circular track or cableway. The dynamic load can pass via corner-blocks to a phased crank shaft. Modeling these details is a good next step.
        > > >
        > > > * Large parafoils have considerable neutral-buoyant mass by carrying along internal air.
        > > > ------------------------------------------
        > > >
        > > > roddy wrote-
        > > >
        > > > 5 times more scary ...
        > > > like this
        > > > http://youtu.be/ql6l3-GWO7I 
        > > >
        > >

        >

         

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