The idea is simple, and it's not new:
6sqm Stackable Pilot In Train.
Instead of carrying different sizes of pilot kites to events, why not take four or five of just one size (I'm betting on 6sq.m, but slightly smaller might cut with less waste), and stack them when the wind is light or more pull is required.
The advantages are many:
To festivals, I usually now carry 2/8sq.m, a 12sq.m and a 22sqm- to cover the wind range and for some redundancy . Total weight 9kg. If instead, I take five stack-able 6sq.m's, then I'll save 4kg, gain versatility (like being able to get 30sq.m lift onto one line when necessary), and have superior redundancy.
Also, light (or heavy) wind flying won't be restricted by losing or damaging any single pilot.
And there are fly-ability gains; Because fabric stiffness doesn't scale with kite size, larger soft kites tend to collapse more often and don't recover as reliably as smaller sizes. And, another scaling effect, large parafoils have the very devil of a problem with slow response- because the mass of air they hold that has to be swung around increases with the cube of dimension, while their lift increases with the square (they become more ponderous the larger they are).
And, ahem, there's another significant advantage of stacking that I shouldn't perhaps mention too loudly;
All pilots are equal, but some are more equal than others.
Whether they are big or small, skinny or fat, beautiful or ugly, stable or unstable, and no matter what their colour, all kites have the unalienable right to equal treatment of course. But, distressing as this is to acknowledge, lesser abled kites do tend to spend more time in the bag and less in the sky and in any train of kites, there is a tendency for the most competent kite to find its way to the top position.
Airbanners at Dameisha.
And though maybe it's insensitive to mention this, the differences in performance between seemingly identical kites can be considerable. High pressure situations (strong gusty offshore winds for example) expose differences in performance that may not be apparent in normal conditions- to the extent that one kite can stay up all day while other apparently identical kites may require re-launching every few minutes. Of course I utterly repudiate the view that green and red kites are fundamentally inferior to blue ones- this is just sheer prejudice. And I put on record right here and now my support for an affirmative program to rotate 'kites of colour' into top positions- but only when the wind is moderate and steady of course.
And there should be cost savings if there were more, but smaller pilots. A reduced range of designs and sizes and commensurate increase in the numbers made would improve manufacturing efficiency (the general rule is that for every doubling of numbers made, costs reduce 25%). I expect that if a fairly standardised design of 6sq.m stack-able pilot evolved the per-unit price, (with direct purchase via the internet), might, with competition, drive down to around $50 (judging by the prices of broadly similar but higher volume products like tents) . There would of course be winners and losers in this, but kite flying over-all should generally be advantaged- so even manufacturers, distributors and retailers who currently depend on sales of lifter kites at higher prices for some of their sustenance will ultimately win.
The difficulty is that making a reliable stack-able pilot is quite difficult to do.
Big Fleas Have Little Fleas.
I made a pretty serious attempt three years ago with a rather anatomically explicit slot at the centre leading edge of the standard 8sq.m/8 bridle PLK Pilot. The idea behind this was that by feeding the main line through this slot, each kite in a train would be able to find it's best angle from moment to moment- rather than it's being set by the angle of the train as a whole.
This idea has failed because lower kites would sometimes unrecoverably deflate and wrap themselves around the line; dragging everything down. This rarely ever happens in steady winds - but it's performance in the extremes that matters. Very few days are spent flying in perfect conditions, and festivals seem, increasingly, to be taking delight in challenging our skills with more and more difficult places and winds - Andalo, Taiwan and Shenzhen for just 3 examples..
I did try rigging restraint lines to prevent slotted pilots from sliding down the main line- the main reason they became line laundry. This reduced the problem a lot, but didn't eliminate it completely.
My next attempt at stack-ability was a bi-product of last year's 4 bridle pilot development. The centre front bridle on this design is fixed at the kite's upper leading edge- to improve launching and re-inflation. Serendipitously, this bridle position provided a place to train from- and is now routinely used for this, especially to get enough pilot area for lifting heavy banners and launching mega kites. It's not an ideal attachment point though- being too far forward for all the lower kites. Except for the larger size (22sq.m), 4bridle pilots trained this way become unstable in stronger winds , hunting from side to side and eventually looping as the wind strengthens. But with this rigging system, lower kites almost never wrap, and even when they do, almost always eventually recover.
I expect that the reason the 22sq.m pilots remain stable with this training while smaller sizes don't, is because of their slower response time- as explained in the second paragraph above.
A solution was always obvious; I'm just not sure why it took me so long to see:
There is a position on the centre line of the top skin of pilots, back somewhere between 5% and 10% from the leading edge, at which a top kite can be attached so that the lower kite(s) never becomes unstable. Because each kite rigged this way is held tight in the main line, it may swing around as much as it likes, but it doesn't seem to wrap irrecoverably- and even if it deflates, will always (so far anyway), re-inflate within a few seconds. We've been rigging various maxi kites this way for years, with complete success- so why did I think that for some reason, the same system wouldn't work with pilot kites?
The purple pilot in the accompanying photos is a new 6sq.m/8bridle developed to use this approach. For this design, the main goal is reliability; with less emphasis on flying angle, pull-for-size or de-power.
6sqm Stackable Pilot.
I will try adapting the simpler 4bridle flare system to it, but at this stage, having more bridles has made development quicker. Two of these bridles go to the upper leading edge- a feature adapted from the 4bridle designs that improves launching and re-inflation. It also uses the 4bridle's cross venting system- which causes the canopy to bend downwards at the trailing edge in light winds for better lift. The lower aspect ratio (compared to the 4bridle series and the 12sq.m 8bridle designs) is for the quicker recovery from partial collapse that this enables.
As a stand-alone kite it seems excellent so far- handling the gusty off-shore winds here at Shenzhen better than any other pilot flying there- with not a single collapse in two days. And this was a hard test, most fliers having given up even trying to keep anything in the sky by the middle of day two.
Rigged under a top kite, it also behaved perfectly - sometimes deflating and wrapping in the extreme turbulence, but always recovering- except when a passing fighter kite cut 5 of its bridles- and even then it still made valiant efforts to contribute at least something to the team effort.
It's next date is with the Mid-Canterbury norwester- a real chicken plucking wind that one. I'm hopeful that the upper end can be pushed to 70km/hr (above which it becomes difficult to stand, let alone fly), but will it remain wrap- free when trained in extreme conditions? This, and train performance in very light winds, will be the crucial tests.
Peter Lynn, Dameisha Beach, Shenzhen, October 31 '11
PS But I'm going to rather miss not having a 22sq.m/4bridle to fly. As for traction kites, there always seems to be one size in a range that is somehow better than the others- and for the 4bridle series, the 22sqm is it, I really like these kites, especially blue ones.