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Advanced Tarpaulin Kites (Megascale
Rope-Loadpath Method)
Simple Tarp-Kites rigged as playsails, have
the greatest COTS power-to-cost performance; but also shortcomings, like
the crudeness of playsail wing geometry, and short service life of an
overworked tarpaulin. Better tarp soft-kite designs are a wonderful
breakthrough. Few AWES engineering challenges will be so rewarding as
perfecting these tarp-kite platforms. What is cooler than a cheap low-tech
mega-kite of decent geometry and robustness?
The New KiteLab megascale tarp-kite method is to first create a large
rope-loadpath structure in a desirable kite geometry (like KiteShip's OL),
and hank the many tarps into place between the loadpaths. This way each
tarp only experiences its local loading and the loadpaths carry the big
accumulated loads. A large powerful Kite-Arch can be made by running a row
of tarps along two or three ganglines, like a constrained laundry line
(ease the leech-line to tune for high lift). The really great thing about
the megascale loadpath method is that the essential "tailoring" of the
wing is merely in the length of the cords: A kit can thus consist of just
a box of tarps and a set of cords cut to the right dimensions.
CoolIP*
~Dave Santos 10Feb2012 AWES5603
Comment and development of this topic will be occurring here.
All, send notes, drawings, and photographs!
Terms and aspects:
Related links and concepts:
Commentary is welcome:
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Notes:
A key to to large tarp kites is to control luffing by any suitable
combination of the common methods.
KitLab's favorite stability method is to fly the kite "staked out" by an
anchor circle, and belay it around to match the prevailing wind.
Telone is Italian, and Manta, Spanish, for Tarpaulin (AWES news hint).
UV resistant tarps with cordage sewn in all around the edge are best.
Some high-duty tarps have a sewn-in diagonal belting (webbing), for
reinforcement. A similar advantage is by setting a rope X across the
tarp to windward, allowing the tarp to billow away from the rope.
Alternatively, one can let the sail rest against the rope X (belting
best), as long as the shape is acceptable and friction does not cause
premature wear. An ancient method is to back up a cheap tarp with a thin
plastic netting, as a sort of primitive rip-stop. In fact "stone-age"
Maylay style leaf kites use a handmade netting to backup a fragile
fabric of tiled leaves.
All sorts of tricks are useful. One can "tailor" a tarp with tucks and
gathers secured by skewers, tapes, and glues to avoid sewing. Tie-offs
can be made anywhere on the tarp with just string and small wood
"pebbles" tucked in the fabric. Grommets are cheap and easy to use. For
gust compliance, elastic lines can be set to the leech (trailing edge)
of a tarp, even just using smaller stretchy nylon cordage in conjunction
with low stretch polyester rope run to the luff (leading edge).
KiteLab has built and flown large scrap-kites (made from old tents) that
fly shoulder to shoulder with commercial wings. Every year, my old
friends (Ortiz/Renteria Kite Kartel) in Austin build a giant kite in
half a day from just bamboo and used construction plastic, to usually
win the "largest home-made kite" category at the local kite festival.
Bamboo kites >100sqm are part of active traditions, from India and Japan
to Guatemala. Traditional designs would fly just as well with tarp sails
as they do with paper and cloth.
The largest stock tarps run as large as 10,000sqft; thats far beyond
bamboo scaling. The only way to use such a tarp and expect it to last a
while is with a full loadpath netting behind it. The advantage of such a
monster tarp is in light winds, by its lower weight (by area) and
porosity compared to open tilings of smaller tarps (suited for higher
winds).
A flat floppy rectangle requires some cleverness to make into a great
wing. The playsail rig pulls hard, but flies with high drag at a low
angle and is prone to luff. A general notion is to modify the flatness
with a pleating that sets a good chord-wise curve while pressurizing the
billows.
There are endless other tarp variations to discover and test. The design
language should be elemental, or one might as well use raw fabric.
KiteShip's OL or NPW (NASA Power Wing) are good models for Tarp Kites:
If you can get tarps to fly comparably or better, that's awesome.
An basic design is a "staked out" rectangular tarp gathered along the
leading edge to shorten it, creating a delta plan-form with a suitable
chord-wise curvature. A powerful kite arch might consist primarily of
tarps rigged into a composite ribbon-arch, with the required longer
trailing-edge as a natural feature, and the tarps able to furl by
draw-lines, just like curtains draw open.
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The modern poly tarp is incredibly cheap, as little as a dime per square
foot for medium duty UV resistant versions with sewn rope borders and
grommets every two feet or so. Value-priced kites run ten times higher
by the square foot, mostly as a reflection of lower volume production by
higher skilled workers. Quality rigid wings run almost one thousand
times the cost of the common tarp, by area. This is why Dave Culp
pondered if there was not some way to use tarps for kite energy; the
"Village Blue Tarp" AWES concept.
Anyone who depends on tarps as canopies knows that the larger sizes are
more vulnerable to blow-out by the concentration of far higher forces.
Strangely, tarp prices seem flat across their size ranges, for a given
fabric weight, so one can buy a box of many smaller tarps at a
comparable price to one larger tarp. The small tarp formats that sell as
many as thirty to a box are very easy to individually manage and can be
aggregated by setting in a large rope load-path network, a minimal
surface with about 30% projected solidity. Furling of the networked
kites could be as simple as pulling lines on window blinds. Cheap tarps
do require early replacement, but the UV protection that allows a
five-year warranty life promises a year or two in AWES service.
The 1500ft or so of tarp to a 150 dollar box is enough lift in a medium
breeze to lift about five hundred pounds at low wing-loading. One could
lift an adapted 10-50kw HAWT and hundreds of feet of conductor with this
amount of wing. A "lift-ready" HAWT payload might look like an airboat
rotor on a sleigh-runner. Such a freaky turbine can win by reaching far
better wind than a HAWT tower can. One can also imagine lounging aloft
under a tarp array like royalty on-the-cheap, the lowest-cost human
aviation of all, persistent and renewable.
Cheap pioneering DIY sky-sailing methods are only workable by
considerable rigging and piloting skills; they are the opposite of
wishful AWES where one merely flips an On switch and walks away. Endless
novel experiments in rigging are possible, and the end result may be
highly refined purpose-built AWES wing arrays.
coolIP
An 1873 French magazine sketch depicts an unattributed South American
kite lifting design with three taglines managing a heavy load bag. The
kite itself is a large framed rectangle with elaborate eddy flap and
rear bridle pennants. Two side pullers hauled on the wing while a third
puller had a tag line to the load.
A. M. Clark in 1875 patented what is obviously a PlaySail, a simple
rectangular tarp with taglines spreading from it to four pullers, and a
payload suspended under the sail. Clive rashly opines that this is
"impracticable"; luckily no one told that to those Nebraska kids on
YTube ("The Furry [sic] of the Wind"), who totally rocked.
The classic tarp-flying video:
BIGGEST KITE IN THE WORLD - YouTube
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