Blue Spot 1 - Flight Reports

The initial flight test of the blue spot was fairly convincing - despite the usual crappy bridling (first bridling attempts are usually based on hanging the kite from the ceiling and adjusting line lengths 'by hand') and the fact that the AoA was way too low, it produced a fair amount of power. However, a number of problems were immediately obvious: Initial inflation was poor - once inflated it was OK, and seemed to hold air pretty well, but getting it to inflate in the first place was tough.

The bridling was very wrong. Not only was the AoA way too low, resulting in almost instant overfly and luff, but the primary bridling points were in the wrong place. Initially I'd bridled at 9%, 33% and 66%, and the kite was 'kinking' between the A and B lines. Poop. In other news, however, there is absolutely no banana evident, which may or may not be due to the balance tube, and the tips stay inflated no matter what. Yay valves!

After some secondary bridle modifications, adding another primary line between the first two, and adjusting the AoA so that the towpoint was at around 21%, another test was attempted.

Ignoring the fact that the brake bridle was now way off, performance was now loads better. It still luffed fairly readily, but that was solvable with more towpoint adjustment. The canopy shape was better, and more power was liberated through that. Steering (with little or no brake control) was iffy, but manageable with some fairly major two-line technique.

With the towpoint moved back a smidge, and the brake bridle redone, it was off to Berrow, where it was pronounced 'good' by a couple of buggy pilots. It was pronounced 'scary' by me as I trundled off in 4mph winds only to have a brown-trousering incident as the wind lifted suddenly. Power was better than the (admittedly somewhat tired) 4m sands we flew it against, and it had hugely better edge performance - it pulls hard up to about 2 degrees before it prepares to luff. It is stable, accelerates pretty fast, and you can now steer it with 4 lines. Inflation is still crap, but once up and 'pumped' it holds shape pretty well. If you induce a luff, it falls back fully inflated until it suddenly powers up in the centre of the window and catapults you out of the buggy (guess who got hit with that one?).

However, Berrow also taught me a valuable lesson. Never, ever, build a kite with ripstop nylon (carrington seconds in this case). Always use icarex, or, at a push, chikara. Nylon absorbs water from a distance of a mile or so, and a couple of dumps on a wet beach is enough to turn that high-performance foil into a nasty shed.

Since Berrow I have replaced the front flap valves with 'tube' type valves, which has improved the inflation and pressure retention. The wing tips have had their AoA pushed up a little higher, which means unexpected luffs are pretty much a thing of the past.

So, a success as a buggy engine, but still not perfect. The additional bridle line doesn't have any reinforcement on the rib, so under full power the canopy still kinks a little. The crap fabric limits usability, and it could really use some Dribs. And the AR is still too low for me. I want the magic 10.

Stop Press!

Roger Parry has taken the original plans and blown them up to 8.2m^2. I think he's mad, frankly, but the result is almost finished. He's gone for tube valves from the off, and I keenly await more test results, a play with the thing, and maybe some photos. On the first flight it apparently tore the brake bridle off, so power would appear to be there....