rexresearch.com



Roy Mueller, et al.

Rotary Arch Kite [ Skybow ]







An extreme sport application of the Magnus Effect -- with apparent potential for power-generation --


 

Videos -

http://www.youtube.com/watch?v=4ZIW-Ypkymk

200 foot Blue and Pink Skybows wereTested in Winds ~10-12 MPH. Rotation speed is at ~5000 RPM's

http://www.youtube.com/watch?v=oYN4zV4_B_c

Skybow Rotary Arch Kite spins @ 5000 RPM's

Two Turbo-Jet Skybow Airfoil Ribbons Flying in the Sky Together in light winds 10-12 MPH. Arch is ~35 feet high.
http://www.youtube.com/watch?v=PbwseVyXkts

A Pair of New Rotary Skybow Electro-Pro Kites

The New Skybow-PRO Electro Kite 75M/250'. By WindMueller Aerology Lab. Boca Raton Florida.

http://www.youtube.com/watch?v=-CfV77GWmfM

Skybow Kite... Digital scale test with winds ~ 10 mph

(200 foot / 60 meter) Skybow tested Dec. 2009 with Digital Scale in 10-12 MPH Winds showed pulling up to 17.68 Lbs. on one end ...


Jim's Skybow FAQ

What's a skybow?

It's a new kind of kite that acts sort of like an anti-gravity rope---when you and a friend at the other end hold it across the wind it pulls upward making a huge arch in the sky.

Who is flying skybows?

Kite enthusiasts worldwide are experimenting with skybows, improving flying techniques, design and materials.

How does it work?

It's not really a rope at all. It's a rapidly spinning ribbon. Have you ever noticed that a dropped card or ticket stub can start spinning and glide away from you as it falls? A skybow's ribbon is attached to swivels that allow it to spin the same way.

So why does spinning make it go up?

That's a subtle question, but it's basically the same reason a spinning ping-pong ball takes a curved flight. It's called the Magnus-Robins effect.

Okay, so why up instead of down?

With flat-ribbon skybows the fliers may have to help the ribbon start spinning in the correct direction---the top of the ribbon should spin downwind. Other skybows have creased edges and always spin the same direction, these skybows must be set up properly in relation to the direction of the wind. If started spinning in the wrong direction a skybow is just as happy to spin the otherway and fly into the ground!

Why does it make that eerie sound?

The aerodynamic forces always act nearly at right angles to the ribbon face, but the ribbon is constantly turning. This produces a rapidly varying reaction against the air ---sound is the natural result. Since the ribbon has two faces, the frequency of the sound is twice the spin rate.

A skybow flying well makes a howling sound reminiscent of the sound of high wind in a pine woods, a skybow that is not entirely steady sounds like a motorcyle race, with repeated accelerations and sudden downshifts of pitch.

Loudness increases drastically with wind speed. At 20 mph (32 km/hr) the curious have been drawn from a quarter-mile (400m) away. The sound is very directional, with a quiet spot near the fliers and directly behind them.

Why are there sometimes swivels in the middle of the arch, not just at the ends?

A skybow needs to spin faster where the wind is faster in order to fly high. Multiple sections that spin idependently can accomodate differences in windspeed along the skybow. Usually the fastest winds hit the high center of the arch. Sometimes a single-section skybow is tapered --- it's made wider in the center than at the ends so that the high windspeeds at the center can be accomodated when the whole ribbon is spinning at the same rpm.

How long can a skybow be?

The record so far, 1000 ft (303 m) long is held by, Mr. Big, a six section skybow 5/8" wide (1.6 cm). Tony Frame and Jim Mallos flew Mr. Big over the Washington Monument Grounds, Washington, DC on November 10, 1997.

The maximum length of a skybow is proportional to the strength-to-weight ratio of the ribbon material. There are fibers made with ten times the strength-to-weight ratio of Mr. Big's ribbon, so skybows two miles long (3 km) may be possible.

How wide can a skybow be?

Tony Frame and I have flown skybows in widths ranging from 10mm to 25mm. (Tell me about your experiments.)

How do you launch them?

Skybows are launched by pulling them taut across the wind. They can be launched all at once, or in stages letting one section go up at a time.

Skybow Builder's Notes

Construction Materials

Mr. Big was made from a sandwich of two outer layers of premium-grade box sealing tape (3M #3750), with a narrow middle layer of heavy-duty surveyor's flagging tape from blackburnflag.com . This design was prone to snap where the edges were damaged.

Construction of Mr. Big's 5/8" wide ribbon:

Polypropylene gift-wrapping ribbon is very strong and colorful, but it is difficult to attach centerweighting in a really permanent way.

The best design so far is an unsymmetrical sandwich of 3M's #863 tape (a transparent monofilament-reinforced polypropylene strapping tape), which is very strong for its weight and lets the color of the bottom layer show through, with a narrow middle layer of polyethylene adhesive tape as the centerweighting, and a bottom layer of 50-micron (2-mil) thick colored polyethylene bag plastic from bearclaw.net.

There are apparently no retail sources for the 3M #863 tape---you have to order a carton of 36 from a tape wholesaler.

Centerweighting

To fly, a skybow needs a strip of stretchy material (centerweighting) running along the center of the ribbon. The centerweighting, needs to be stretchier than the rest of the ribbon so that it shares little of the ribbon's tension. Inelastic materials will not have a stabilizing effect.

Roughly speaking, the centerweighting should increase the weight of the ribbon by 50% and be narrower than 75% the ribbon width.

An adhesive vinyl tape, such as electrician's tape, can be simply stuck on one or both sides of a ribbon, or a non-adhesive vinyl tape, such as surveyor's flagging tape, can be used in a sandwich construction. Polyethylene adhesive tape, such as "Frost King Weatherseal Tape," which is used to install plastic-film storm windows, is better than vinyl because it is less prone to delaminate.

Other stabilization methods

It seems that the function of the centerweighting is to make tranverse waves move along the skybow more slowly than the torsional (twist) waves. There two other ways to accomplish this same end:

1) carry all the tension at the very edges of the ribbon by placing low-stretch fibers there, or

2) give the a ribbon a tube-like cross section so it can act a like a flexible shaft.

These should be fruitful areas for research.

Weight

Skybows rely on damping from aerodynamic forces to spin smoothly, so the skybow must be rather light. A rule of thumb is that the skybow should not weigh more than 15 times the weight of the air in the cylinder that circumscribes it. For example a 17mm wide skybow can spin smoothly if its weight is 4 g/m---and even lighter is better.

Stiffness

A skybow does need a certain stiffness across its width so that when twisted under tension it will not buckle and twist up like twine.

Swivels

The ends of a skybow segment must be held by very low friction swivels. Only high quality (e.g. SAMPO) ball-bearing fishing swivels will work. Use the largest size you can find, as the small ones will wear out in a few minutes even though the tension is moderate. For some reason the black swivels last longer than the nickel plated ones. Lubricate each swivel with a drop of sewing machine oil. Do everything you can to keep the swivels out of the dirt.

For long-life swivels you have to take the trouble to make your own, using quality ball bearings with rubber seals. I am using MR115-2RS bearings from bocabearings.com.

Length

A skybow needs to be long enough to power the spinning of its bearings. This minimum length depends on the width of the ribbon. We've had success with 30m lengths at 19mm width, and 50m lengths at 15mm width. When multiple segments are used in a bow (as in Mr. Big), the segments can be shorter since in general one segment only needs to power one swivel instead of two. Most recently I have been making 17mm-wide skybows with multiple segments just 24m long. In the eastern U.S. the flying fields are never big enough, so short segments are more convenient.

The longest single section we've flown was about 114m, but really long single sections are in danger of twisting up like twine if the windspeed varies greatly along the length of the bow



http://stores.ebay.com/The-Skybow-Store

Skybow Information

Finally!!  After 16 Years of Research, 7 Miles of Ribbon, 100's of Variations of Materials and Swivel Systems, we have sorted out All The Best... To bring to you the Ultimate in Skybow Design and Performance.  

Introducing The Original WindMueller Turbo-Jet Skybow!!!

 The complete system was developed and is manufactured at the WindMueller Aerology Laboratory (Based in Boca Raton Florida since 1991).  The NEW Basic Skybow Unit is NOW comprised of 1 Continuous 200' Section of Rip-Stop Airfoil Ribbon, which translates into a Top Arch Height of ~24Meters/77 Feet.  Available soon from our site, we will have add-on, connectable sections that come in 30M/100' & 60M/200' lengths, to build an arch as high as you want to go.  There is no known limit.  The longest we have gone is 1000', creating an arch approximately 350-400 feet high in the center.  An Incredible 33 Pounds of Pull on each end of the 1000' Skybow was recorded.  The Turbo-Jet Skybow now also comes with our Latest High Performance MEGA-Velocity Ground Swivel's, rated at 85 Pounds/85,000 RPM's.  In a Light Wind, the Skybow Ribbon can spin at an incredible 4000 rpm's.  With Higher Dead-Smooth Winds (16-22 MPH), 7000-10,000 rpm's are now possible...  A hum will begin to sound once the Skybow Pops Up Into the Air, which is the loudest from beneath the Center of the arch.  Like the sweeping motion of a (Rotary Wing Aircraft) Helicopter Blade, the Skybow Airfoil Ribbon has a Sweeping Lateral Rotation.  This creates an Incredible Low Pressure towards the direction of the oncoming wind, which magically lifts the Skybow high into the air, based on the Magnus Effect Principle. (Named after the German Physicist and Chemist Heinrich Gustav Magnus (Photo below)).  Although Heinrich Magnus Published his papers of this Discovered Effect in the Mid 1800's, there has never been an apparatus to Demonstrate this Effect and Principle until Now.

The Turbo-Jet Skybow is the perfect tool for High School and College Mathematic & Science Projects. You can now move a Class of Students Momentarily Outdoors to an open area and demonstrate in real time, the Mathematical and Scientific Concepts of Angular Momentum, Angular Velocity and Witness first hand, just how powerful The Aerodynamic Principle of the Magnus Effect is.  The Basic Skybow Unit Now includes...  A Pair MEGA-Velocity Ground Swivel's, A 60M/200' Skybow Airfoil Ribbon, and A 10" Yo-Yo Winder... which all fit into 2 special drawstring pouches to keep everything together in, with the instructions.   It is possible to obtain an arch past 90 degrees perpendicular tilted into the direction of the wind Using Micro Aerial Swivels.  With longer bows, a horseshoe type arch, shaped like the St. Louis Arch in Missouri is possible.  Find a friend or two, to help you hold the ends so you can hear the noise it makes from underneath the center. With a good wind it can sound like A Thundering Waterfall or an Oscillating Turbo-Jet Engine

Chart Based on using 85,000 rpm rated swivels with a 17 mm/200' Rip-Stop Skybow Airfoil Ribbon.

The Highest Velocity ever Recorded was 10,625 rpm's, July of 2009.

Wind Speed -- ~ RPM Range : SkyBow Results

8 MPH --3000 : Parallel to Ground
10 MPH -- 4000 : Low Wavy Arch
12 MPH/10 Knots -- 5000 : Minimal Arch
14 MPH -- 6000 : Good Arch
16 MPH -- 7000 : Great Arch
18 MPH -- 8000 : Strong Arch
20 MPH -- 9000 : Very Strong Arch
22 Mph -- 10,000 : Super Strong Arch
24 MPH/20 Knots -- 11,000 : Maximum Lifting Arch
26 MPH & Above -- Above 12,000 : Instability Range



USPA 2010270432    
ROTARY ARCH KITE AND SWIVEL SYSTEM

Inventor:  MUELLER ROY
IPC:   B64C31/06; F16B7/00

Abstract -- A rotary arch kite kit may include a rotary arch kite and a system for connecting various segments of the kite. The connecting system may include ground swivels, aerial swivel connectors and static connectors. The ground swivels may be single independent swivels for attaching a handle to the rotary arch kite. The aerial swivel connectors may be double independent swivels for, for example, attaching two lengths of rotary arch kite together. The static connectors may also be used for joining two lengths of rotary arch kite together. The rotary arch kite of the present may include a unique folding and stitching design to permit enhanced rotation and lift.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to kites and, more particularly, to a rotary arch kite and swivel systems for operating rotary arch kites.

[0003] Rotary arch kites may produce a pulling force in excess of 50-60 pounds. These kites may also rotate at high velocities, often upwards of 20,000 revolutions per minute (rpm) or greater. Current swivel systems may not be able to work with these pulling forces and rotational velocities.

[0004] As can be seen, there is a need for a rotary arch kite and swivel system that may allow operation of the rotary arch kite at typical pulling forces and high rotational velocities.

SUMMARY OF THE INVENTION

[0005] In one aspect of the present invention, a rotary arch kite kit comprises a rotary arch kite; a ground swivel adapted to provide a handle for the kite; and an aerial swivel connector optionally connecting the rotary arch kite to a second rotary arch kite.

[0006] In another aspect of the present invention, a ground swivel comprises a strap having a tube rotationally attached to the strap; a monofilament extending from a body of the ground swivel, the tube attaching to one end of the monofilament; an end casing permitting another end of the monofilament to pass through into the body of the ground swivel a spacer ring within the end casing, the monofilament passing through the spacer ring; and a bearing, wherein the monofilament fits into an inner bore hole of the bearing.

[0007] In a further aspect of the present invention, a rotary arch kite comprises a strip of material, wherein the strip of material is from 1 to 4 inches wide and from 100 to 300 feet long, wherein the kite is formed by folding the strip of material in thirds and stitching the folded material along its length at one side of the strip; and an end of the folded material being folded and stitched to itself to form a loop in one end of the kite; and a slit cut in the end of the kite.

[0008] These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an aerial swivel connector according to an embodiment of the present invention;


FIG. 2 is a side view of the aerial swivel connector of FIG. 1;

FIG. 3 is a top view of the aerial swivel connector of FIG. 1;

FIG. 4 is an exploded perspective view of the aerial swivel connector of FIG. 1;


FIG. 5 is a perspective view of a ground swivel according to an embodiment of the present invention;


FIG. 6 is an exploded perspective view of the ground swivel of FIG. 5;

FIG. 7 is a perspective view of a handle being inserted into the ground swivel of FIG. 5;


FIG. 8 is a perspective view of a static connector according to an embodiment of the present invention;

FIG. 9 is a perspective partially taken-apart view of a rotary arch kite according to an embodiment of the present invention;

FIG. 10 is a perspective view of an end of the kite of FIG. 9; and

FIG. 11 is a top view of an end seam of the kite of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

[0021] Various inventive features are described below that can each be used independently of one another or in combination with other features.

[0022] Broadly, an embodiment of the present invention provides a rotary arch kite and system for connecting various segments of the kite. The connecting system may include ground swivels, aerial swivel connectors and static connectors. The ground swivels may be single independent swivels (that is, a first end may rotate relative to a fixed second end) for attaching a handle to the rotary arch kite. The aerial swivel connectors may be double independent swivels (that is, each end may independently rotate) for, for example, attaching multiple lengths of rotary arch kite together. The static connectors may also be used for joining two lengths of rotary arch kite together. The rotary arch kite of the present may include a unique folding and stitching design to permit enhanced rotation and lift.

[0023] Referring to FIGS. 1 through 4, an aerial swivel connector 10 may include tube casing 12 having end casings 28 attached to each end thereof. A monofilament 20 may extend from each end casing 28. The extending end of the monofilament 20 may attach to a tube 22. The tube 22 may attach a first rotary arch kite 24 with a second rotary arch kite 26. Typically, two aerial swivel connectors 10 may attach to each end of a central rotary arch kite, with two additional rotary arch kites attached to each of these aerial swivel connectors 10. In an alternate embodiment, the tube from one end casing 28 may attach to a strap handle and the tube from the other end casing 28 may attach to the rotary arch kite. Within the tube casing 12, each monofilament 20 may pass through a bushing 14 and fit into an inner bore hole of a bearing 16. Each monofilament 20 may have different diameters, as shown in FIG. 4. Alternatively, each monofilament 20 may have the same diameter. A bushing 18 may fit between adjacent bearings 16. The tube casing 12, end casings 28, and bushings 14, 18 may be made of any suitable material, such as PVC, CPVC, ABS, carbon composite, metal, and the like. The bearing 16 may be a high RPM rated bearing, such as a bearing rated at 10,000-500,000 RPMs.

[0024] Referring now to FIGS. 5 through 7, a ground swivel 30 may include a strap 32 having a tube 34 rotationally attached to the strap 32 to allow the tube 34 to spin freely at high velocities. A monofilament 36 may extend from a body 38 of the ground swivel 30. The tube 34 may attach to one end of the monofilament 36. The other end of the monofilament 36 may pass through an end casing 40, a spacer ring 42 and fit into an inner bore hole of a bearing 44. A first spacer 46 may attach to the end casing 40. A tube 48 may fit over and attach to the first spacer 46. A second spacer 50 may fit into and attach to the tube 48. As discussed below, the strap 32 may attach within the second spacer 50. A heat shrink tubing 52 may be used to cover and protect the components of the body 38 of the ground swivel 30. The end casing 40, tube 48, and spacers 46, 50 may be made of any suitable material, such as PVC, CPVC, ABS, carbon composite, metal, and the like. The bearing 44 may be a shielded high RPM rated bearing, such as a bearing rated for at least about 85,000 RPMs, however other bearing ratings may be used.

[0025] According to one embodiment of the present invention, the strap 32 may be folded in as shown in FIG. 7. The resulting four layers of strap 32 may be inserted into the second spacer 50. A hole (not shown) may be drilled in either the second spacer 50 and/or the tube 48. The hole may also pass through the four layers of strap 32. A pin (not shown) may be inserted into the hole to hold the strap 32. Optionally, a monofilament may be inserted through the pin to reinforce the strap 32 onto the body 38 of the ground swivel 30. Other means, as may be known in the art, for connecting the strap 32 to the body 38 of the ground swivel 30 may be used.

[0026] The tube 34 of the ground swivel 30 may attach to one end of a rotary arch kite. The ground swivel 30 of the present invention may allow the rotary arch kite to rotate at high velocities, even while a pulling force is applied from the ground swivel 30. The spacers 46, 50 may be, for example [1/2] inch pipe and the tube 48 may be a [1/2] inch coupling and the end casing 40 may be a [1/2] inch cap.

[0027] The ground swivel 30 may have other uses where a swivel handle may be desirable. For example, the ground swivel 30 may be used to connect a dog collar to a leash, thereby preventing twisting of the leash.

[0028] Referring to FIG. 8, a static connector 80 may be used join ends of a rotary arch kite. The static connector 80 may be used, for example, in place of the aerial swivel connector 10, described above. The static connector 80 may have first and second tubes 82 attached by a monofilament 84. In one embodiment, three rotary arch kites may be part of a kite package, wherein the ends of the middle rotary arch kite connect with the other two rotary arch kites with two aerial swivel connectors. In another embodiment, a first and a second rotary arch kite may be joined with the static connector 80. A fourth and fifth rotary arch kite may also be joined with the static connector 80. A third rotary arch kite may have the aerial swivel connector at each end to connect to the first/second rotary arch kites at one end, and to the fourth/fifth rotary arch kites at the other end. The ground swivel 30 may be used as a handle for the first rotary arch kite. Such a package may incorporate several features of the present invention into a single rotary arch kite package or kit.

[0029] Referring now to FIGS. 9 through 11, a rotary arch kite 90 may be an airfoil ribbon formed from, for example, ripstop nylon that is folded in thirds, as shown in FIG. 9. An exterior third 92 may be attached with stitching 100 for the length of the kite 90. The length of the kite 90 may be from about 100 to about 300 feet, typically about 200 feet. The unfolded kite 90 may have a width from about 1 to about 4 inches, typically about 2 inches. Each kite end 94 may have a slit 96 cut therein. The slit 96 may be use to retain a tube of, for example, the ground swivel 30, the aerial swivel connector 10 or the static connector 80. The kite end 94 of the kite may be formed by folding about 6 inches of a material end 98 of the kite onto itself. This material end 98 is then folded under itself (back toward the kite end 94) for about two inches to create a fold 106, resulting in a three-layer thickness 102. This three layer thickness may be joined with stitching 104 as an interior, elongated X, as shown in FIG. 11. The stitching 104 may not extend across the width of the kite 90, as such stitching may provide a perforation in the kite capable of tearing. The stitching 104 may extend beyond the fold 106, as shown in FIG. 11.


Addendae ( 4-2018 )

http://weaveanything.blogspot.com/2012/03/skybow-thoughts.html
Weave Anything -=- Weaving baskets by computer

Reminiscences on skybows

In the late 90's, Tony Frame and I developed a rotating ribbon arch kite that we called a skybow. I provided most of the engineering ideas, but none of it would have happened without Tony's driving encouragement and his part in the flight testing and design iterations. I wrote at the time that flying a skybow was like playing with "an anti-gravity rope" because, held across the wind between two fliers, a spinning skybow "sags" up the way an ordinary rope sags down. In favorable winds, a skybow can form a tall, leaning, horseshoe-shaped arch, typically many tens of meters in length. A skybow is a soft kite in the sense that there are no struts, and it coils up compactly after flying. The controversy over whether a skybow really is a kite at all is probably ongoing, the arguments being summarized early on in an article on skybows by Steve McKerrow and Valerie Govig in the Winter 1997-8 issue of Kite Lines magazine.

The outstanding characteristic of a skybow is its rather absurd length-to-width ratio. Mr. Big, with a 16mm chord (flown on the Washington Monument grounds in the fall of 1997) was 300m long (as measured lying on the ground)—in that dimension it was probably one of the largest kites ever flown—at the same time, in the chord dimension, it was probably one of the smallest kites ever flown. We later flew a 17mm-chord skybow that was just over 400m long (one quarter of a mile) on the Washington Monument grounds during the 2002 Smithsonian Kite Festival. My petite girlfriend (now my wife) started shrieking so much at seeming to be pulled straight up into the air (though I doubt the tension was really much more than 30 pounds) that Tony, ever discrete, took himself to another part of the field. A skybow does not really have all that high a lift-over-drag ratio—magnus-effect airfoils are not very good at L/D in any case, and the effective aspect-ratio is reduced by the twisting of the ribbon—but when a skybow is misaligned to the wind, the downwind side of the arch can seem very steep. Hence the skybow flyers' rule: "up moves up, down moves down." (For example, if your side of the arch seems to be lying down, you need to move downwind.)...

During the same late-nineties era, Roy Mueller of Wind Mueller Aerology Lab in Boca Raton, Florida, independently developed a rotating arch kite that is stabilized by a different principle. We were corresponding and sharing samples at the time. It is fair to say that Tony and I were jealous of the Mueller design's ability to form tall arches with short lengths, and Roy may have envied our design's performance in high winds. Roy's design, which had a cross-section that popped into classic airfoil shape when uncoiled, seemed more affected by aerodynamic pressure (or centrifugal force) in high winds. But that was years ago. I see that the Wind Mueller Lab is still coming out with new commercial skybow designs, ones that I am not familiar with.

In contrast, our skybow design was a dynamically stabilized flat ribbon. It did not seem to care how fast the wind was blowing, or how fast it was spinning, as long as the arch was shortened enough to keep the tension in the ribbon in a safe range. I had the pleasure and excitement of flying a 80m-long skybow in sustained 50 mph winds at Jockey Ridge State Park in Nag's Head, North Carolina. The noise was incredibly loud—like a Harrier jet landing on your head—and that was in a situation where the wind itself was so loud you needed to yell to be heard 20m...

A taut ribbon will not spin stably by itself. That's a fact that will be overly obvious to trained engineers—I say overly, because a skybow proves that under the right conditions a taut, lightweight, unsupported ribbon can spin so smoothly it seems like a laser beam. As a trained engineer, the effectiveness of aerodynamic damping was something I needed to be confronted with in person.

A taut ribbon will not spin stably by itself—it will typically either turn wide-side to the wind, and not spin at all, or go through wild oscillations of spin and translation. But if twisted up enough, it will indeed spin stably. A demonstrator of this is what Tony and I called a wind-womp. Terminate both ends of a 24 yard section of 3/8" corrugated plastic ribbon with 4 feet of light kite string. Hold the resulting assembly across the wind while twisting up the string at one end with a cordless drill (no swivels being used at either end.) As the increasing twist is shared with the ribbon, you will see its behavior in the wind gradually improve. Ultimately, with a lot of twist in the ribbon, it reaches a point where it spins smoothly, and then reverses, alternately flying up and then down, and making a "whomp" sound each time it changes direction.

That is fun, but unfortunately this kind of twist stabilization cannot be maintained when swivels are added to each end to allow a continuous rotation in the "up" direction. We first tried a practical approximation to twist stabilization. Our first skybow was 2" wide, made out of "poly" packing tape. It had built-in discrete twists of 90° about every 10 chord-lengths (as I recall). Each 90° twist was accomplished by fabricating a hollow, elongated tetrahedron out of the same tape. (You could also think of the tetrahedra as universal joints rather than 90° twists, I am not sure which idea was foremost in my mind.) The results flying a 50m length of this sort of skybow on the Washington Monument grounds and the beach at Mason's Neck State Park in Virginia where encouraging, but it was a lot of work to make kites this way...

I don't remember how I came to the idea that we could stabilize the ribbon dynamically by "mistuning" the twist-wave and translation-wave velocities. The key proved to be adding slack material (deadweight) near the center of the chord. The addition of this mid-chord inertia lowers the translation-wave velocity, but has little effect on the twist-wave because mass added at the mid-chord does not increase the airfoil's moment of inertia. (It is important that the added weight not carry tension, or the weighting effect will be partially or even completely cancelled.)...

Our most successful skybows were razor-trimmed assemblies of commercial tapes. We added stabilizing weight to our skybows by including a stretchy, thick, narrow tape at the center. Trying to build a symmetrical sandwich of commercial tapes proved problematical as there was always enough stress at the center to cause unsightly local delaminations. Instead, we settled on an unsymmetrical three-layer design, strong on one side, weak on the other—the stress on the adhesive bond being limited by the weaker layer. The main mechanical strength came from a layer of high performance, clear, polypropylene strapping tape from 3M (#863 tape trimmed in the last assembly step to 17mm chord-width), the weighting came from a thick, stretchy, clear polyethylene weathersealing tape (Frost King Weatherseal Tape, trimmed before assembly to 10mm width), and the color came from a thin layer of colored polyethylene film (2-mil Bear Claw bags from Bland Co., trimmed in the same final cut with the polypropylene strapping tape.) The stretchy weighting tape was assembled with its unsticky side against the sticky side of the polypropylene strapping tape. That allowed the thin colored polyethylene film to be in contact with pressure-sensitive adhesive over its full width. The stretchy tape came off the roll with so much tension that a motorized capstan was needed to lower the pre-stress before assembly. Making skybows quickly becomes a matter of making tape-converting machines that make skybows. My homebrew tape-converters never worked very reliably, or without fussing over every few meters, and making unnecessary splices. That, and the cost of converting materials that were themselves at retail prices, was our big problem in trying to go into commercial production. That and the fact no customer anywhere had flown anything like it. A well-tested skybow went to persons who said they were going to fly it at Burning Man. It came back covered with beautiful pink playa dust and complaints that it had not flown.

The center-weighting tape in a skybow is not entirely un-structural. When a taut ribbon is twisted, compression stress builds up across the width. The thickness of the weighting tape in the middle part of the chord helps reinforce the ribbon against buckling in compression.

A skybow can work with swivels just at the two ends. We called this a single-section skybow. We flew single-section skybows that were as long as 114 meters with some success. There is a launching problem with a single-section skybow since the entire length must be supported off the ground to start the ribbon spinning—ultimately, there is a length where this is no longer possible. There is also a performance problem with a single-section skybow since the middle of the arch sees better wind, and lies at a better angle to it, so it wants to spin faster than the two ends. This problem can be avoided by tapering a single-section skybow to a narrower chord near each end—but that only makes the next problem worse. A long, single-section skybow can carry a lot of torque towards one end, where, if anything stops the ribbon from spinning, it will cause a buckling failure of the tape that basically turns the ribbon into twine—for good. For these reasons, as well as the ability to reef in the length of the skybow to suit the wind speed, we settled on making independently-swiveled sections of 20 to 24 meters in length. These could be easily launched or reefed, one section a time, and were nearly immune to the twist-up buckling failure. Swiveled sections of moderate length are also easier to handle on the ground.

When flying a multi-section skybow, it is possible to end up with one section spinning in the wrong (downward) direction. Then there is nothing to be done short of bringing down the entire skybow to that section and relaunching it. To avoid this problem we would "train" the skybow sections to prefer spinning in a particular direction by strongly folding the outboard, unreinforced, portions of the chord in a Z-pattern. The polypropylene tape would almost completely "forget" this creasing, but remember it just enough to strongly prefer spinning in the trained direction. A trained skybow has, in effect, a left side and a right side (as seen looking downwind) that must be respected in setting the skybow up on the flying field.

Under high tension a skybow will sometimes snap. Surprisingly, it is not rare for a skybow to snap in two places at once—some sort of shockwave phenomenon I guess. If that happens, the broken middle portion of the skybow may drift a long ways downwind—something to consider when choosing a flying field.

If repairing (i.e., splicing) a skybow is necessary, anything you do with pressure-sensitive tape will prove temporary. We came up with an expedient we called squiggles. Two sections to be spliced are folded over double and overlapped. The squiggle, a zig-zag, bent piece of piano wire is woven over-and-under (the action is really more like wrapping) the doubled and overlapped ribbon to generate enough friction to hold the splice together permanently...

If you fly skybows you will soon learn this truth: twisted is tantamount to tangled. To handle a long length of ribbon without tangling, it must be kept untwisted. If a length of skybow on the ground is being twisted up by the wind, it must be allowed to align downwind, and fast.

Winding spools having cranks can store ribbon without twisting it, but they are dangerous. They can break your fingers with the crank, or friction-burn right through your clothing with the rim. Notice that the usual way of winding onto a crank-less spool puts twist in the unwound portion of the ribbon—which is only permissible if the twist is being freely released to an off-spool swivel.

If you buy cut ribbon in a fabric shop from an experienced clerk she will deftly wrap it (untwisted) in a figure eight on two fingers of one hand. The same approach works to wrap a 24m section of skybow on the forearm. Once slipped off the arm, the untwisted ribbon can easily pay out from the inside of the figure-eight. Cinching these figure-eight hanks with velcro cable ties (which can obligingly stick to one's socks when not in use) became my favorite way to deal with skybows on the ground.

Another way to handle long lengths of ribbon, useful at times, is to stuff the ribbon into a sack (or, indoors, into a pile on the floor) taking care to remove twist as it goes in. It may not seem likely that a chaotic pile of ribbon will remain untangled in a sack, but it will, if you remove all twist before it goes in, and never allow the tag end of the ribbon to enter the sack. This storage method is strictly last-in-first-out.

Five-hundred pound fish don't spin very fast. The relevance of that saying is this. It is easiest to start with homebrew skybows by exploiting ready-made fishing swivels from the tackle shops (only the highest-quality, e.g., SAMPO, ball-bearing swivels will work at all.) The ratings on these swivels are for breaking under tension, not spinning under tension. You need to choose a ball-bearing fishing swivel rated about twenty times the tension you expect in your skybow. Even then, if you keep the swivels out of the dirt, the life will only be a few outings.

Five-hundred pound fish don't spin very fast. The relevance of that saying is this. It is easiest to start with homebrew skybows by exploiting ready-made fishing swivels from the tackle shops (only the highest-quality, e.g., SAMPO, ball-bearing swivels will work at all.) The ratings on these swivels are for breaking under tension, not spinning under tension. You need to choose a ball-bearing fishing swivel rated about twenty times the tension you expect in your skybow. Even then, if you keep the swivels out of the dirt, the life will only be a few outings.


https://en.wikipedia.org/wiki/Kite_types

Arch kites -- a single kite with an arch form,[61][62][63][64] multiple arches,[65] or an arch top[66]
 
http://www.energykitesystems.net/Kites/RibbonBowArchRotators/index.html

Ribbon-arch-rotating kites and its cousins where "ribbon" is taken to extremes into snakes, Darrieus complexes, Selsam cylindricals, Faust-ribbed playsails, etc.  [Herein is mostly considered flip-winging with secondary overtures of Magnus-effect processes in  complexes with their attending low-end lift/drag challenges.]

http://web.archive.org/web/20030604035820/http://www.wizard.net/~jmallos/skybow/
http://www.wizard.net:80/~jmallos/skybow/builders.htm

Jim's Skybow FAQ // Skybow Builder's Notes

Construction Materials


Mr. Big was made from a sandwich of two outer layers of premium-grade box sealing tape (3M #3750), with a narrow middle layer of heavy-duty surveyor's flagging tape from blackburnflag.com . This design was prone to snap where the edges were damaged.

Construction of Mr. Big's 5/8" wide ribbon:

Polypropylene gift-wrapping ribbon is very strong and colorful, but it is difficult to attach centerweighting in a really permanent way.

The best design so far is an unsymmetrical sandwich of 3M's #863 tape (a transparent monofilament-reinforced polypropylene strapping tape), which is very strong for its weight and lets the color of the bottom layer show through, with a narrow middle layer of polyethylene adhesive tape as the centerweighting, and a bottom layer of 50-micron (2-mil) thick colored polyethylene bag plastic from bearclaw.net.

There are apparently no retail sources for the 3M #863 tape---you have to order a carton of 36 from a tape wholesaler.

Centerweighting

To fly, a skybow needs a strip of stretchy material (centerweighting) running along the center of the ribbon. The centerweighting, needs to be stretchier than the rest of the ribbon so that it shares little of the ribbon's tension. Inelastic materials will not have a stabilizing effect.

Roughly speaking, the centerweighting should increase the weight of the ribbon by 50% and be narrower than 75% the ribbon width.

An adhesive vinyl tape, such as electrician's tape, can be simply stuck on one or both sides of a ribbon, or a non-adhesive vinyl tape, such as surveyor's flagging tape, can be used in a sandwich construction. Polyethylene adhesive tape, such as "Frost King Weatherseal Tape," which is used to install plastic-film storm windows, is better than vinyl because it is less prone to delaminate.

Other stabilization methods

It seems that the function of the centerweighting is to make tranverse waves move along the skybow more slowly than the torsional (twist) waves. There two other ways to accomplish this same end:

    1) carry all the tension at the very edges of the ribbon by placing low-stretch fibers there, or

    2) give the a ribbon a tube-like cross section so it can act a like a flexible shaft.

These should be fruitful areas for research.

Weight
Skybows rely on damping from aerodynamic forces to spin smoothly, so the skybow must be rather light. A rule of thumb is that the skybow should not weigh more than 15 times the weight of the air in the cylinder that circumscribes it. For example a 17mm wide skybow can spin smoothly if its weight is 4 g/m---and even lighter is better.

Stiffness
A skybow does need a certain stiffness across its width so that when twisted under tension it will not buckle and twist up like twine.

Swivels
The ends of a skybow segment must be held by very low friction swivels. Only high quality (e.g. SAMPO) ball-bearing fishing swivels will work. Use the largest size you can find, as the small ones will wear out in a few minutes even though the tension is moderate. For some reason the black swivels last longer than the nickel plated ones. Lubricate each swivel with a drop of sewing machine oil. Do everything you can to keep the swivels out of the dirt.

For long-life swivels you have to take the trouble to make your own, using quality ball bearings with rubber seals. I am using MR115-2RS bearings from bocabearings.com.

Length
A skybow needs to be long enough to power the spinning of its bearings. This minimum length depends on the width of the ribbon. We've had success with 30m lengths at 19mm width, and 50m lengths at 15mm width. When multiple segments are used in a bow (as in Mr. Big), the segments can be shorter since in general one segment only needs to power one swivel instead of two. Most recently I have been making 17mm-wide skybows with multiple segments just 24m long. In the eastern U.S. the flying fields are never big enough, so short segments are more convenient.

The longest single section we've flown was about 114m, but really long single sections are in danger of twisting up like twine if the windspeed varies greatly along the length of the bow.



https://tvclip.biz/video/PbwseVyXkts/pair-of-new-turbo-jet-skybow-pro-kites-75m250.html

The New Skybow-PRO Electro Kite 75M/250'. By WindMueller Aerology Lab. Boca Raton Florida. Capable of producing upwards of 20,000 RPM"s... Enough to power up to 4 outlets for charging a Laptop, a Cell-Phone, a String of LED's Lights and a Radio... simultaneously.



https://tvclip.biz/video/asEQ3qllnLs/amazing-kite-turbine-by-scottish-inventor-engineer-rod-read-kite-powerplant-system.html

Amazing Kite Turbine By Scottish Inventor Engineer Rod Read - Kite Powerplant System

...Airborne Wind Energy Systems (AWES) are not a new concept. However, many systems under development, such as Google’s Makani, tend to require complex computer controlled hardware to steer the flying turbines accurately, making them expensive and introducing operational risk.

Hebridean engineer, Rod Read, has developed a system using spinning kites tethered to a ground-based turbine. (think of the spinning red parafoils on the BBC ident) The turbine only uses kite parts without needing controls, making it lightweight and affordable. Working in an open source hardware environment, Rod has spent the last five years perfecting his design and his company is now selling these scalable kite power systems online. Further R&D on his system designs is being carried out in conjunction with the University of Strathclyde and TU Delft in the Netherlands.

Rod explains “Power to weight ratio is key to the efficiency of flying wind turbines. The advantage of using kites is their lightweight construction. My system ties the kites in a simple rigging arrangement which can be set up quickly and easily, even in terrain where you couldn’t transport a regular turbine. This first system is designed to be affordable for personal use, for example when camping, but the science which guided the design allows it to be scaled up to provide enough power for grid and utility uses.”...




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