May  2018
A BRIEF HISTORY OF RECENT LARGE KITES
Before Dominic Jalbert's 1950s development of 'soft' kites which use the stagnation pressure of airflow (Bernoulli's principle) as a structural element, large kites were size limited by frame strength. The largest Japanese Wan Wan's could be more than 20m diameter (315 sq.m.), but weighed an impractical 2 tonnes- or more. The Holland Kite Team, led by Gerard van der Loo, made the first successful very large soft kite, the CS550 (550 sq.m, <150kg), in 1982. Their guiding principle, which has been adopted for all the large kites that Peter Lynn Kites have made, is that they should have as little pull as possible.
In 1983, Edmonds Community College in Washington State, USA, made a more conventional parafoil style kite that was larger than the Dutch kite, but its launch director, Steve Edeiken, fell and died when he became entangled in the bridles while launching it. By the American Kitefliers Association's criteria at that time (flying at an altitude greater than the kite's width for more than 2minutes), this flight qualified for the record, but it was never recognised due, I expect, to the tragic consequences.
The Holland Kite Team flew their large kite for the final time at the 1995 Napier Kite Festival (New Zealand), preparing the way for the Megabite, Peter Lynn Kites' first very large kite, built that year. This flew at many events, and officially received the Guinness record during the Bristol International Kite Festival in 1997 by flying without any part touching the ground for more than 20 minutes.

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Megabite 635 sq.m
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Large Parafoil
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CS550 (The Blob)1982
The size of large kites cannot be simply defined, and the areas I quote are usually more conservative than what Guinness (and media) often claim. By our view, "qualifying area" is the projected area of the kite when inflated, not the stretched-out dimensions, and does not include tails and non-lifting appendages. Guinness declared the Megabite to be 933 sq.m, but by our criteria it's 635sq.m., as is the Mega Ray (built in 1997) which we made as near to the same area as possible so that both could be claimed by events as the "World's Largest Kite". The Megabite was subsequently purchased by Gerard van der Loo/Vlieger Op and has now passed to Dominique Scholtes, who occasionally flies it at events. The Mega Ray was also flown at many events by Peter Lynn Kites and then sold to Lutz Treczoks in Germany. Since Lutz's untimely death (not from a kite accident) the Mega Ray has been ably flown by Sebastian Ju and team, (also Germany). The Megabite and Mega Ray are made from zip together sections to enable travel by air as personal luggage. Zips work well enough but can fail when subjected to scraping as the kites launch and land. All our subsequent very large kites have been of one-piece construction and are freighted to events.

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Mega Ray 635 sq.m
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The Pearl 1250 sq.m
The first of which was a 950 sq.m (inflated) Kuwait flag kite for the Al Farsi kite team, recognised as the new world's largest kite by Guinness on 15th Feb 2005. Also in that year, flag kites of this size were made for Masaaki Modegi in Japan (the Mega Moon) and for David Gomberg in the USA (a US flag).

For emergency take-down, our very large kites use various systems. The Megabite and Mega Ray both have velcro-ed sections on their upper surfaces that can be ripped open to deflate the kite by pulling a cord paralleling the main line. Flag style kites use a different system; when the main line is released, a line attached to the kite's trailing edge causes the kite to turn over, deflate rapidly, and descend.

In 2011, Peter Lynn Kites made a 1250sq.m (inflated) kite for the Al Farsi's. It's a large Ray, called 'The Pearl'. As for the Mega Ray, a line attached to the nose is used to depower the kite and cause it to drift back to the ground (without deflating). But the Mega Ray also has a rip-panel. Because of Al Farsi nervousness about the nose line as the only take-down option, The Pearl has only ever been flown three times- and has just arrived back in NZ to have a rip-panel fitted (if biosecurity authorities ever release it!).

In 2018 a new 1250sq.m (inflated) flag style kite was built for the Al Farsis. Called 'The Hope', it's just had a second successful outing- at Berck-sur-Mer in France. It is the first very large single line soft kite that can fly without stabilising side lines (though the Mega Ray and The Pearl nearly can in light smooth winds).

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Kuwait Flag 2005 950 sq.m
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Mega Moon 2005 950 sq.m
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USA Flag 2005 950 sq.m
Critics have questioned whether very large kites are really "kites" at all, seeing as until now they have required active stabilising by teams of people on side lines. I tend to agree with this, while recognising that kite events are more interested in attracting media attention than in such nuances. Side lines enable very large kites to fly in a limited space and eliminate the requirement for self-stability, which has made making large kites much easier given that there is no theory of stability by which such kites can be designed. Nor is it possible to scale from smaller versions. This is because three factors effecting stability; aerodynamic forces, weight and mass, don't stay in proportion as size increases (weight and mass are not directly related for soft kites because the enclosed air has mass but no weight). Aerodynamic forces increase with the square of dimension, as weight nearly does in the size range of larger kites, but mass increases as the cube of dimension. This matters, because when a kite recovers from leaning over, the rate of recovery is slowed by the kite's mass- with an undeterminable effect on its stability. The Pearl is 6 times the span and length of a standard maxi ray, about 10 times as heavy, has 36 times the area, but encloses 216 times the air mass (9504kg versus 44kg). As for smaller kites therefore, the only available design process, except for informed guesses, is trial and error- which is impractical for kites that each take many months to construct, 20+ tonne anchors, a team of fliers, and substantial organisation for every flight.
To reduce the effect of enclosed mass on the stability of very large kites, we use the "super ripstop" construction system. Earlier large kites like the Dutch CS550 and the Edmonds College parafoil, connected their top and bottom skins with multiple ribs in conventional parafoil style type construction. In consequence, the air in each cell must move with the kite during any correction. With super ripstop construction, the top and bottom skins are connected by multiple cords, which allow the kite to rotate independently of the enclosed air. I doubt that very large soft kites can be single-line stable without this facility, though I'm unsure as to the size for any given style at which this mass effect becomes critical.

But from 20 years watching various large soft kites flying with side lines, there seemed every chance a very large flag style kite with a suitable tail could fly stably on a single line. And fortunately, I do now have a "theory of tails" which is verging on the quantitative. Not having any enclosed air mass, flat tails do scale predictably enough, so we were able to test variations on smaller flag kites before committing to a full-size version. And it worked!- a success that I'm pleased to claim a share of, even though it seemed too easy- a small offset for the huge string of kite failures that I can also lay claim to!

Wind was very light at Berck, so we don't yet know what The Hope's upper wind limit will be for single line flying, but expect it to be useful. It was unstable during its first flight there, climbing immediately to full height, only to dive back down, climb again and so on. For this we can blame Daniel Bernoulli (1700 - 1782, Swiss), whose equation describing fluid flow establishes that when velocity increases, pressure decreases. This is experienced as the bath plug pulling in when you try to hold it partly out. During The Hope's first flight at Berck, there was a significant wind gradient- almost no wind at ground level but 15km/hr or more at 100m up. When it reached maximum altitude, there was significantly more wind above the kite than under it. There was therefore a nett low-pressure area above the rear of the kite, which caused it to nose down and descend (called a luff). This was also the cause of the infamous restaurant trashing by the Mega Ray in Sardinia (2001?). Very large soft kites are susceptible to this because they are carefully tuned (by adjusting camber) for minimum pull- so fly on the verge of luffing, and because they are generally flown very close to the ground. When there is a significant wind gradient, they should therefore be flown higher or pilot kites should be used to hold the leading edge up.

PETER LYNN, ASHBURTON, MAY 1 '18

As some of this is from recollection, I'll be pleased to correct any errors that are bought to my attention.