AN ABSOLUTELY INCREDIBLY, STUPENDOUSLY, FANTASTICALLY GOOD IDEA, I THINK.
It's not mine either, just in case you're wondering after this somewhat positive endorsement.
But first, a reprise of where things are at on the single line single skin (SSSL) front:
It's sort of depressing actually; when a goal is achieved there is a brief period of euphoria, then boredom and 'what do I do now?' sets in.
But fortunately, like when climbing hills, each ridge reached usually reveals another higher one, and in this case I can already see one in the distance which I would rather like to get to.
My initial goal, when I started exploring SSSLs a little more than 4 years ago, was to see if such kites could be developed to a level where they would be useful.
I already knew that such kites are possible because a parachute with a person hanging below it can be tow-launched as a kite. But in this case, the person, without whom the ensemble isn't single-line stable, weighs perhaps 15 times as much as the canopy, so is not a practicable single line kite.
And in 2012 at Dieppe, Robert van Weers had a shaped piece of fabric with 3 or 4 bridle points which would fly single line- though I never saw it flying, so can't attest to its angle, stability or wind range.
By mid 2014 I had 12 bridle single skin pilot style kites flying in a modest wind range (15 to 30km/hr) and now have 20 bridle 1Skins and 16 Bridle Singers that cover the range from maybe 8km/hr to more than 100. By early 2016 the single skin 20m Octopus could handle almost the same range (with 3 different bridle settings) and, finally, last week, after an immense struggle, a 35m Serpent achieved the same range but without the tentacle ties that make the Octopus style so difficult to manage. The 26 bridle Boomers, which were licensed off to John and Irene Tan in Singapore quite early in the program, are also fully operational SSSL pilot kites, especially in mid- range winds.
The inherent tendency of SSSL pilots to superstability (slowly but inexorable diving off to one or the other side in stronger winds), which the first 3 years of this development was plagued with, eventually yielded to very careful leading edge and skin shaping, though this solution did cost some light end performance. Tailed SSSLs, like the Octopus and Serpent do not suffer from superstability, though do show something similar when flown in light winds with their leading edge bridles on strong wind settings.
But after the Pasir Gudang and Satun events (at which I used only single skin pilots) it's clear that having the wind range covered is not by itself enough to make single skin kites practicable for fliers who are not as fanatical as I am. To be truly useful at events like these, where the wind routinely varies from not enough to too much quite a few times every hour, pilot kites need to have one setting that covers the entire range- like the 11sq.m Airbanners ram air pilot which is currently the gold standard. This is NOT going to easy to accomplish for SSSL pilots, but at least I know what I'm going to be doing for the next few years and won't be getting bored.
For the SSSL pilots:
Lever bridles and pulley bridles, both of which lengthen the front bridles and shorten the rear ones in response to the kite's centre of pressure moving forward as line angle increases.
And, for the 6 sq.m 1Skin, re-rigging the centre front bridles shorter and the shoulders longer to cause preferential but non-destructive drag inducing centre collapse in stronger winds.
For the tailed SSSLs:
What I call 'blink' stability to broaden their range on each bridle setting. By this, the shoulder bridles are shortened until they collapse at lower wind speed than the centre, which causes drag that prevents the kite overflying, but recoverably (having the centre collapse is not). Though this sounds crude, it is effective; reducing the number of settings for the entire range down to just 3.
But for events like Pasir Gudang and Satun, none of this is enough. Even when using 3 pilots with overlapping ranges: 7 to 20 (6sq.m 1Skin on forward setting), 10 to 60 (Lever bridle 3sq.m 1Skin) and 15 to 100 (2.5sq.m Singer with tail), I had to change kites repeatedly as the wind strayed outside any range selected. Even for someone as obsessional as me, this was just about too much trouble.
Fliers want a pilot kite they can pull out of the bag, throw up into the sky and forget until they have to pull down and pack- and most don't have the skills to tune bridles anyway, even if they have the willingness.
This is a level of flyability that I would dearly like to be able to supply: An SSSL Pilot with the same wind range as, say, an 11sq.m Airbanners ram air pilot, but flying at a higher angle (increasingly demanded now as show kites fly higher too) and for a third the cost and a quarter the weight.
The essential function of wind range extenders for SSSL Pilots is to have something that is angle of attack or line angle sensitive that will pull the trailing edge bridles in and/or let the leading edge bridles out as the kite's angle of attack decreases at higher line angles. Lever and pulley bridles both do this, and, in their most developed form so far, probably halve the number of wind settings required.
Volker's idea is to use high-drag rear bridles so that as wind speed and flying angle increases they pull in on the rear of the kite, automatically changing the kite's angle to suit different winds. The genius bit of his idea is that such bridles are sensitive to flying angle as well as to wind speed because it is only at higher flying angles (lower kite angle of attack) that the wind flows across them- at lower flying angles they're more in line with wind flow direction. I use light weight braid rather than heavy cord for these bridles, because in the wind range of interest, braid develops aeolian vibrations which cause drag to increase at a rate far exceeding the square of the wind speed. Perhaps this bit is my contribution.
I've tested the idea on a 3sq.m 1Skin by changing the rear 6 bridles to 8mm wide braid. On a light wind setting such that, with original bridling, the kite's leading edge just collapsed at apex, with the braid bridles, no leading edge collapse was ever visible. This was a sequential test rather than side by side, so the satisfactory result could have been because the wind was different, but I don't think it was, because maximum line tension didn't change noticeably. As a bonus (or otherwise, if noisy kites annoy you) it also sounded rather like a Dieu Sao (Vietnamese flute kite) in gusts and climbs- a loud middle C buzz.
I did also try braid rear bridles on a 35m Serpent, but by then the wind had dropped too much for noticeable effect.
Too soon to be sure, but VERY promising! Surely with this, porous skin sections, lever/pulley bridling and Simon Freidin's secret squirrel stuff going on over there in Melbourne, there are now sufficient tools to make an all winds SSSL pilot possible. Thank you once again Volker (he also solved the Serpent problem for me by suggesting a few modest tail slits).
Oh well, plenty of thinking time!
PETER LYNN, ASHBURTON, NEW ZEALAND, 1 APRIL 2017