The Dreaded Delta Dive

Well, it actually wasn’t a delta kite, and it didn’t really dive – but it definitely looked dreadful … 🙂 We were at Ljubljana Marshes landscape park again, targeting river Ižica and the putative Roman road just beyond it, but our main goal was to test a remodelled delta of a unique Dr.Agon kites design. Our old 333 cm Great White Delta was behaving funny for some time now, so the kite master decided to rip it apart and remake it into a sort of an unvented Conyne. The kite is 4 meters wide now and it lookes absolutely magnificent.

The triangular box that goes all the way along the spine unbroken – unlike a typical delta conyne that has the central third of it removed – is there for stability and extra lift in soft winds. This modification was to expand the wind range and to avoid the kite acting funny in wind gusts and especially when the wind changes its speed substantially while the kite is up.

The test started perfectly in a ~20 km/h breeze:

Liftoff complete

The wind started to pick up speed, but the new Great White Almost-Conyne Delta performed impeccably

100 meters AGL

It looked like this was going to be a fairly uneventful KAP session, when we noticed a couple of probems. As the Delta was widened the cross spar had to be longer, and for portability it was made of three segments – and because of that it was much more flexible than before. The Delta started to bend furiously in the ever stronger wind gusts (now approaching 40 km/h) and its wing profile got more and more distorted. The spars in the wings couldn’t cope with all the forces and suddenly the kite veered …

Pan pan pan … abrupt loss of lift on the right wing

Deltas are notorious for this behaviour, but it seemed the triangular conyne tunnel exacerbated the problem. By letting the line go the kite temporarily stabilised and rose again – only to veer again, this time making the first of what will be many loops.

Start of the second loop. Mayday mayday mayday.

Now the wind speed prevented the line to be fed efficiently and the kite started to gyrate in tighter and tighter loops closer and closer to the ground.

And then it crashed.

Accident site from this side of the river

The poor kite nosedived onto a meadow on the other side of the river, and the picavet and our better camera ended on a bush that softened the impact … We were extremely lucky as the kite missed two large and hungry kite eating trees by a couple of meters; the only real problem was the kite “landing” spot was across the river, and the nearest bridge was a couple of kilometers away.

Loop and crash sequence in 30 second intervals

During the frantic attempts to save the kite we let a lot of line out – 350 meters of it in total, as confirmed on a map (see how it missed the hungry kite eating trees!):

In the end, everything was OK. The camera was intact, the Delta was swiftly recovered and flown again – nothing broken or torn. The end of the kite line was wet, bit that was it.

Poor kite …

Funny – the precursor of this kite, the Great White Delta had survived one such crash; it was even more dramatic, landing on top of a huge pine tree … and two of our smaller deltas still adorn tall trees, one in Ljubljana and the other on Bloke plateau …

Dr.Agon kites chief designer and kite master has ideas about mitigating the problem of looping and crashing. So next time we will have better news – and better kite aerial photos! 🙂

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