Peter Lynn Himself
March  2019
ONWARDS AND UPWARDS- PROBABLY

The topography of kite development (as for most new things) is a scattering of peaks of unknown form, number, and height, rising out of a mist enshrouded swamp.

Blundering around in this swamp, when a patch of dry and rising ground is encountered, the highest point of that particular hill can be reached- provided impenetrable bush and precipitous sections can be worked around.

What can't be known without going back down into the swamp, is whether there's a higher peak out there somewhere.


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1 skin 6sq.m showing leading edge buckling
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37 bridle keel less SS Pilot at Kuwait 2019
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Bridle supported leading edge SS Pilot kite in Kuwait 2019
 

From about a year ago, the 1Skin design (a single line single skin pilot kite) had run out of hill- having come up against leading-edge collapse, skin compression and excess lateral (keel) area (necessary to support bridles) all of which make these kites unreliable above about 40km/hr. Which was obvious at the '19 Nelson Kite Festival, when no single skin kites would stay up in the strong gusty winds. After this debacle ("A LOST CAUSE?"- last month's Newsletter) I pulled out some archived single skin pilot kite prototypes and flew them against more recent examples to confirm what I strongly suspected; that there has been little if any gain in strong wind reliability since 2015, notwithstanding all my clever dick 'improvements'. So, I've been back down stumbling around in the swamp for nearly a year now looking for another hill to climb. About the only compensation is that during this phase of development, prototypes don't have to be pulled down for changes to be made - just wait a few seconds for them to crash- if they get up at all. But sooner than expected, I've emerged onto dry land and am climbing strongly again. Occasionally the mist even clears a bit and there are glimpses of beckoning heights- or maybe I'm hallucinating- but whichever, I'm having a lot more fun than when I was slogging around in the bog. The breakthrough- if it really is- has come from using bridles rather than flares (keels) to support the leading edge and skin. The downside is more bridles; 1Skins have 20, the latest designs currently have 58, though a version that's flying OK has just 37. The upside is that they don't buckle in strong winds though they zoom around a lot- which can be damped by adding tails and may yield to shoulder shaping and careful disposition of lateral area. The lead-in was a 2/3rds size Serpent head made to test various shapes, sizes and attachment of tails, which surprised me a lot by flying without any tail at all. Actually, it was more stable in this form than some earlier Serpents were with tails. I also found that with rear outer flares (see photo), it was subject to terminal 'diving over', and wouldn't fly at all, which has led to an understanding of a lot of kite misbehaviour that's puzzled me since forever. It's a really simple cause and effect when you see what's happening, but not easy to explain in words or diagrams, so will have to wait until I get suitable graphics organised.

And adding to this, the Octopus/Serpent series of single skin show kites has also taken a step forward, with a 60m Serpent now rock solid from 12km/hr to more than 40km/hr on just one bridle setting. It still has the signature Serpent tendency of hanging a bit left or right in very light conditions- and traverses fully to one side when it stalls- but if better angle of attack control can be devised (see below) these remaining annoyances will be cured. When I tested this 60m Serpent in strong winds at a local industrial park, (after Nelson and before Kuwait), I had a bit of a whoopsie: It has a take-down line by which a light pull collapses the head no matter the wind strength, and after I'd finished testing I used this to drop the kite for packing away. As I detached this line, the wind came up even more and the kite self-launched, dragging the back of my 1.5tonne anchor vehicle sideways a bit. The kite then looped a few times before settling down at a decent angle weaving from side to side rather ominously. Being by myself, I then faced having to wait for the wind to become strong enough to break the line or crash the kite- or drop enough for me to pull it down. Instead I drove, with some loss of traction, to the upwind end of the field (aren't 4wd's wonderful), turned towards the kite and drove downwind at 60km/hr + until I ran out of field (about 500m). At which point the kite was (just) on the ground. I then leapt out and ran to the head, getting there just as it re-launched. Eventually some passers-by called in help and the husband of one of our Ashburton staff arrived with his 4wd. We then pulled it down with a caribiner. At the Kuwait Kite Festival (just finished) this kite was almost civilised enough to pass the good neighbour test - a huge gain from the indulgences single skin kites have required to date, and a definite sign that they are finally growing up.

 
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60 m Serpent and 4 sq.m keel less SS Pilot at Kuwait 2019
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60 m Serpent and other SS's at Kuwait 2019
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Pearl Mega Ray at Kuwait 2019

By the way, Kuwait '19, ranks amongst the very best kite events I have ever attended: 5 days of consistent winds ranging from light-useable through to upper mid-range, impeccable hospitality, excellent organisation, and an almost big enough kite field with plentiful anchors. The world's 3 largest kites flew at various times (all together on the 3rd day) and at one point there were 89 maxi kites in the air- not bad for just over 30 invited fliers.

If I get to Berck this year (probable) I'll retrofit the 60m Serpent's bridling to a 30m version, and possibly to an Octopus, to check whether the 60m's improvements are scalable (I think they are).
And I'll prepare bridle supported leading edge single skin pilot kites of various styles so as to have plenty of testing to do there (like Kuwait, Berck is an excellent place for kite development, especially when there's access to sewing machines).

But if single skin single line kites are ever to be more than just curiosities and an intriguing technical challenge, their leading edges need to extend further below the main surface when the kite is flying at a low line angle, but shorten up when flying high. Deeper leading edges make launching easier and enable light wind flying, but get pushed in, causing leading edge collapse, in stronger winds and when the kite climbs to a high flying line angle. Finding ways to have the leading edge depth change automatically with line angle and wind strength is therefore the key to single skin kite success.
Currently I have 2 ways to do this (see last month's newsletter):
One is aeolian bridles that pull the kite's trailing edge down at high flying line angles- which pushes more pressure forward to support the leading edge as well as applying drag to limit the maximum flying line angle.
The other is a pulley and bungy system that changes the leading edge depth in response to line pull.
Neither of these is ideal, and aeolian bridling is really only useable for kites with significant tails (like Serpents) because it pulls the kite's centre of pressure rearward, which upsets the stability relationship for tailless kites.
I have a few other ideas that are worth trying; none of which look to be easy however.

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Rearward lateral area causes diving over.

Climbing this hill is going to be formidably difficult therefore, but hopefully worth the effort if successful.
And there's nothing else I'd rather be doing.

 
Peter Lynn, Ashburton, 1 March 2019