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Advanced Concepts

Science-Kite Series

These kites & gear are research tools into reliable kite operations & micrometeorology.

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3D Anemometry

Real wind is helical & a two axis wind vane reveals this 3D structure. Below- a string tripod holds KiteLab's 3D windvane stable. The tailed delta holds up the "solid" tripod, but freely adapts to conditions by wandering. The fins on the vane can be seen flexing to filter out small turbulence while tracking kite-scale shifts. A halyard hauls up the wind vane & the faint ground-line keeps its from swinging. The picture was taken from the front lawn of the World Kite Museum. Sonic anemometers are likely to be the way to do airborne anemometry going forward.

1st Mass Lifting excercise- red ballast sack remained aloft for hours under a stable apex (< 5 cm. motion) of string tripod lifted by X-5 concept delta, which danced in turbulence.

Gram scale monitors line tension- this session with the X-5 concept delta showed ~800 gr. avg., with variation between ~0 to 1500 gr., in the lee of dunes. Terrain Interference (shed vortices) causes high variation in pull that a rachet/spring device could capture for driving a generator.

Landing Legs

Lifter Module with Landing Legs. Ballast/payload sack was trimmed for light conditions. The lander made numerous stable landings & relanches in variable breeze. A habitation module is a fond goal.

Particle image velocimetry (PIV) During '07 in Portland there was a summer blizzard of some sort of thistledown revealing extreme variations in trajectory of similar particles in the same wind field. Vortical filiments would capture gently drifting particles & really take them for a ride.

 

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10-08 The Grenada Island Moon Kite , a variant of West Indies Kites found from Bermuda to Surinam is an ultra high wind kite. I've long posed the question to kite experts as to what is the best high wind kite & been told the Tailed-Delta (particularly the Delta-Coyne) & Tailed-Sled are the best in a gale, but even these kites struggle in force7 or more. When i found George Peters flying at the One Sky fest (with Kay, Director of World Kite Museum) & posed the high wind question about his Grenadan kites, he laughed hugely & said "bring on the wind, this kite loves high wind, the more the better" Its roaring hummer can be heard from afar & may be a secret- a vibrating airframe that energizes its boundary layer to prevent violent vortex-shedding instabilities.

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Kite Deicing

Dec.15/08 Ilwaco, WA- Icing & blizzard conditions trial, toy plastc kite, aeroelastic flutter effectively prevented accumulation, kites generally self de-ice in high-wind or gustyness..

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Toward a New Lifter Kite: Pictured below is a completely compostable sled that flies well tailless, excellsin light wind & furls in a gale. It showed strange behaviors, flying inverted, folded sideways, & flapping like a bird; transitioning in changing conditions from one mode to another while maintaining flight.

Concept Deltas: The ancient delta kite continues to evolve. Its swept wing works over a wide range of conditions. Airplanes & birds get away with longer straighter wings by superb airfoils, complex control, &/or powering fast in their own air rather than dancing in a natural helical wind-field. As the swept delta is kicked around the leading wing drags more, correcting yaw like a primitive brain. The real genius of the kite is the frame. The wing tips pull up on high wing loading providing progressive (pitch) trim. The kite shifts its CG aft as its wings furl by curling.

The classic Delta Conyne was the basic reference for stability & performance, as it was most often mentioned when i asked master kiters to suggest the best all-time flyers. Gradually the new deltas supassed the Conyne- two sticks less, much lighter, & with the full stability package, more stable, able to operate in even higher winds.

It is hard to improve on, but fun to try, so i started chopping & augmenting toy deltas & later stock hobby kites, for use as "science kites" for my windfield studies. Eventually a dozen-plus modifications proved themselves, & taken together, really do make a better kite, more versatile, with a wider wind range.

enhanced stability package, amphibous capability, visibility package, useability features

Bridle

Variable Bridal AoA trim, five or more positions to tune to

Elastic Trailing Split Bridle

Multi-line/Single-line convertable

Single-line Tackable

Full Depower- Kite Killer, a sliding bridle-point like fish divers have

Power Trim, varies high AoA sail that functions like airplane landing flaps

 

Tail

Integrated Ram-air Tube Tail as air-beam empennage, venturi intake

Variable Ballast Clips

Tail as Kite bag

Sand Drain (water drain for water relaunch), a minimal reduction of airbeam pressure

 

Wings

Gurdy Wheel Tip Stabilizers, flasher action, spin set counter to wingtip vortices

Tapered Sleeve Set Frame, less weight, better stress distribution

Eddy Flapp TE, adds area & stability

TE Fringe, Eddy Flap effect on finer scale, eases TE flapping wear

Turbulators, dog-tooth & slot/hole

Cross-spar Lanyard

Variable (increased) Porosity/Elasticity (toward TE)

Misc. Upgrades

Water Relaunch Float

Skyhook, Improved design

Adding Sail- single-spar skyhook flying under delta pilot-kite effectively boosts overall pull, useful in light conditions.

 Kite made from foam carry-out lid.

1) Bird Alerters, reelable tufts or ribbons every few meters, 2) Eye-spots on kites (avoid nesting stress), 3) Bird right-of-way

Notes

A good tailed delta flys stably backwards in lulls & gains lots of altitude when pumped slowly, thus flyable in near zero conditions, pumping up into useable wind.

A fishing reel is superior for kite use, esp. boat reels rigged with dacron or spectra line.

Tacking (leaning) destabilizes the kite some, observe wind-helicity handedness, which favors one tack & endangers the other.

Appendix

Delta Science Kite Series

Small PVC X-Kite Delta first proved integrated airbeam tail, carried a two-channel data-logger

Docking/Hotswapping

PVC Chinese Butterfly Delta with a docking hook on its nose, proved docking to be practical, close-hauled like a jib under a lifter-kite.

<= Butterfly shown successfully nose docked to "party-line" & pulled close-hauled by its bridle. Captain Clark assisting.

Docking Hook, add or remove kite from train

Gayla PVC Delta with a rigid keel added

X-Kites Nylon Delta w/ Koinobori integrated as tail

Gomberg Spotlight Delta with all the favored ideas integrated

See also the soft delta helium-kite

 

Sticky kites prone to nose dive as ballast CG balances vertically & keelstabilty builds with speed

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Tazed by the Sky: X-5 ScienceKite Encounters Electric Hail

12-26, '07.

The Columbia-Pacific seashore is a dark world, but once eyes adjust, its a gleaming silver gloom, how pearly fishy it shines. This winter day was splashed with sun, rainbows, & milky opalessent hail-showers over avalanching snow-glare surf. I lounged in the lee of a giant driftwood stump, in a pup-tent scaled snowboarding shell, never more at home. The X-5 ScienceKite flew smartly* in a near NW gale on about fifty feet of 80 lb. test dacron braid kiteline. More line was too much power higher & toilsome to retrieve.

Odd, it seemed a bug bit my thumb; funny tricks mind plays, now bit harder, how very strange. A sizzling sound erupted over the pelting hail. Weird crackling rose to an alarming roar from all directions. My kiteline & reel-rod shimmered. I grabbed the reel & got a smart electrical zap, plus adrenalin. I was being tazed by the sky , current gushed from the bristling reel. Now what? Perhaps a death bolt any second. A cowboy is taught to cast off metal in this situation & i began to toss the reel, but froze; for a cowboy is also frugal, & a hundred dolllars of kite gear would bound away downwind faster than any chase. Some anxious seconds later the reel lodged in the tree roots & i ran off. The hail soon passed & i got the kite back. In momentary survivor's elation, kite still flying, i saw a bald eagle pluck a large fish from the surging foam, all magic.

That afternoon i made a crude electroscope from aluminum foil & a plastic jar, to connect to the kiteline. It alerts well before things get too charged but seems to inhibit eagles. Next i'll rig an FET electroscope with tone/light alarm, voltage calibrated, to interface with an opto-isolated data-logger. A power strip varistor will protect electronics, & a "lightening arrestor", a bypass conductor to ground.

Notes- the kiteline was wet from drizzle & salty from months of ocean vapor. The hail & supercooled air were charged & transmitted this to the dilectric kite (new, not salinated). There was probably little risk of a deadly bolt under these particulars. Franklin's experiment is credible, kite electricity is not hard to observe across fairly typical electrostatic fields. This encounter happened by accident, on a short kiteline. The "insect bites" were small shocks as my thumb brushed metal parts of the reel. The crackling roar was discharge along semiconducting boundaries of wet & dry all about my kite gear & person, if it had been dark a sputtering blue fire playing about would likely be seen. This kite electricity event was somewhat different tahn Franklin's, there was no thunder (but thundering surf) & it seems like St. Elmo's Fire. That shimmering was faint plasma tendrils, on about a cm. scale, refracting dimly in daylight. Some shimmer may have been eyelash discharge, as i my face tingled & my beard crawled. Microelectronics is at-risk in such voltage fields. Lucky the the wireless usb webcam & data-logger were not onboard; they were due to fly next. The base-station computer would also have been at risk.

* thanks to its "stabilizer package"

March 25 (?), '08., experienced electric hail a second time, same beach, same rig, same zapped hand, again the hasty ditching of the sizzling reel in a driftwood snag, & apparently the dacron line melted/burnt thru & the kite flew free. Haven't found much online documentation of electric hail phenom. Altitude was low both times, so it seems the hail is transfering charge to the kite skin rather than more altitude dependent "Franklin charge" transfer to a long kite line. Tried to use electroscope with mere umbrella in hail, but the wind kicked the umbrella rigged instrument around & the hail was wet, not freeze-dried, shorting buildup, no clear charge, so i need to clamp off umbrella & await conditions.

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Jan., '09

Wayne,

just to clarify my overall findings-

Your concept of tethered foils has been validated both by the soft-composite "hotwings" & the single-skin "flipper-wings", which far outperform ~comparable conventional kites in speed & power.

Counter-findings are that inflatable tech & avionic/actuation electromech are not essential, & you might mull over running with a bare-bones revolution v. heavier, more complex, & expensive features that add failure points. Of course time may make the full vision practical, but you don't have to wait.

dave

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hi Peter,
 
Have long enjoyed your newsletters. Re: Jan 09
 
additional single-line stability factors for your list, some are "major"-
 
lighter weight: for two kites of same design the lighter will be more stable due to less flywheel mass resisting or overshooting pendulum/snowplow*/reflex corrections (exception: if critical perturbation faster than natural pitch/roll/yaw freq. of lighter kite, but slower than heavier kite's periods) * "snowplow stability" after Holland
 
compliance: a kite like the modern delta or sled that flops loosely when hit by small perturbations is more stable (lower Q-factor of an oscillator less sensitive to resonant input from specific scaled turbulence)
 
aeroelastic entrainment: turbulation of flow around kite can usefully stabilize. Two broad categories; a) turbulators creating vortical filaments on upper surfaces keep flow attached, preventing stall & act almost like straps onto wind-flow, b) energizing boundary flow generally has stabilizing effects (entrained gyro mass)
 
aeroelastic dampening: airframe vibration acts as mass dampener (as well as conditioning boundary flow). West Indies Moon Kite is high wind champ & seems to rely on its essential hummer to do this, plus b) above)
 
swept surfaces: vortical shedding smoothed (lower Q-factor again)
 
Bridle drag: dampens reaction, esp. edo like multi bridles.
 
kite detuned to turbulence spectrum: natural wind-field turbulence has a lot of order within its chaos. Given practical partial turbulence characterization, kite scale, line length, etc. can be chosen to decouple kite from dominant turbulence harmonics. 

Yikes, better stop here, could go on & on about conquering turbulence. Solved auto-zenith mystery after we met; obscure wingtip twist mechanism cited helps, but its magical misdirection, the answer is on the ground where control-bar, level & squared to the wind acts as an artificial horizon for passive brakeline correction.

Best Regards

Dave Santos

KiteLab

Ilwaco, WA

Austin, TX

KiteSurfing MegaLoop Theory
-kite accelerates crosswind upwindow to one side while
-pilot accelerates across-to-upwind in the other direction while
-(in video) steep wave advancing upwind provides an advancing launch-ramp to revector horizontal acceleration upward
-in-flight, kite & pilot tend to fly as a paraglider, but,
-with a sufficiently fast rotatable traction kite, tossing in a kite loop is possible. Its more flash than oomph, look closely the pilot is barely jerked (in part by yanking-in control-bar).
-kite dives partly of its mass in 1G, &
-accelerates rotation going into a loop of tightened radius. Here is where its hard to tell how much kite "brakes" (flaps) are converting momentum into sending the kite downwind (which kite sees as pitch-up). Such motion has kite going downwind faster than wind, for a moment.
-snap at the loop bottom is interesting, the goal of the loop is not to make useless pull downwind, but to beat the accelerating freefall of the pilot & get wing back up to Paraglider mode for landing.
- mixed with pitch-up input is- a) leading wing-tip, lightly wingloaded at low AoA (therefore less D) whips around mainly by centrifugal force &
-b) high AoA retarded wingtip ("flap down") is higher wingloaded (therefore Lower L/D), CP may actually be toward retarded side & not contribute to turn,
-diving to loop bottom requires kite to outrun downwind its spherical coordinates with a little kick fully extended at the base of the kite power window.
-wind gradient in play, at bottom of loop weaker wind partly cancels better power zone.
-waggling kite adds sweep to soften landing as needed, pilot aligns for landing.
Its that easy ;^)
 
WARNING author learned to kite-jump from Utube & never yet looped in jump, no chest-armor or will, too old & chicken.
 
Note: Rotation cycle of a looping airborne-energy kite ("HotWings") differs considerably, mostly by its fixed anchor, much more kick downwindow, leaning-egg-shape loops, power pulse pesks past loop bottom (7-8 o'clock, pointy egg end), see vid clip off of-
 

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providing a baseline for comparison with small sleds, which scale up, while sticky kites, by scaling law, remain smaller.

===========key old links==============  

Best Kite Study (tied with Ito & Komura)   http://en.scientificcommons.org/8488723  

great ribbon-rotor paper   http://dspace.mit.edu/handle/1721.1/38720

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