Multi-Link Tethers and Sleeved Multi-Lines
Common kite tethers are single lengths of one line well suited to the
loads a single kite puts on a tether. The slightly greater tension at the
kite (that DaveL found in his simulations) favors the line parting at the
kite in the event of break-away, so that the kite will not drag along XC
indefinitely, but glides down. Eddy/Patton trains include tri-swivels
inserted along a main tether, so that kites can branch off and not develop
line twist as they loop. Trains and stacks develop far greater tension at
the surface; the sum of all the kites pulling together, therefore an
optimal tether is graduated in stages, much like a multi-stage rocket
tapers toward the top. The end result is similar; a capacity to fly higher
than any single-stage. Stages can also be assembled and disassembled on
the fly from separate winders, adapting to changing wind, and damaged
Lets call such composite tethers "Multi-Link". The simplest and kitiest
method to connect links is with a larkshead loop and stopper knot, which
everyone should know how to make. For a graduated line, a thinner link
should larkshead onto a thicker line stopper knot. Properly done larkshead
knots are secure, especially under load, and easy to connect and
disconnect. With very fine line, a tail is sometimes added on the knot
loop, to grab if needed for easier disconnect.
Hardware is often introduced between links, like the tri-swivel noted
above, but a common instance is a shackle of some sort. Rigging, sailing,
fishing, and climbing all have great versions of shackles to use or learn
from. In the case of kites a good shackle is light, generally aluminum in
any size larger than sport fishing shackles. Snap shackles are handy, but
beware the potential of such shackles to snap onto a line unintended, with
potentially disastrous results. Where a risk of such fouling exists,
choose a locking shackle. Always select the "perfect" shackle from the
endless selection of products.
Pulleys are a common rigging component with many variations. Special
pulleys are designed to allow knots and low profile shackles to pass.
Graduated rings and stopper balls allow multi-link tethers to display
programmed dynamics as multi-tethers (original Cody War Kite staged-launch
method). Varied components, like NAV markers, can be linked in between
line sections. The possibilities are infinite, and extend into 3-D
lattices for mega-scale latticework.
Pocock highly optimized almost all the features of his Charvolant kite
buggy system. One of his proudest innovations was to put all three of the
traction-kite lines in a silk sleeve, thereby preventing most snagging,
sawing, and looping twists. Protected so, the lines could be specified
thinner, offsetting sleeve weight. Its possible that the neatness of
sleeved lines even reduced aerodrag, further offsetting any extra weight.
Pocock did not report that the bit of extra actuation friction was a
problem. especially compared to the robustness of being able to yank
sleeved lines out of trees, as happened on occasion.
Sleeved Muli-Lines seem to have been overlooked by modern kite riggers,
but like all else Pocock discovered, are due for a comeback. A natural
trick is to use modern braid-over-core, or hollow-braid with custom core
added, as a multi-line by pulling on the core differentially from the
outer braid. Many basic control functions could be so enabled, like
steering or kite-killing.
~Dave Santos 21Nov2011
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