PFK all the way?

Today I was out in a big wind!

So the big Atlantic weather is with us now and I have just retreated from a shoot of a windmill on a hill I have been after for months, the HQ2.0 fairly ripped the arms off me and, although I’d quickly realised I had too much kite before the wind, it was an epic struggle to get it back without snaring overhead wires (telephone, imagine the shame in trying to get British Telecom to co-operate in a kite or line recovery!),  swirling trees, lampposts, hedges and rooftops. It was a case of hold on until the gusts eased and then haul away whilst dancing with the kite to keep it in an uncluttered piece of sky! Back at base I ponder the kite I should have used: Paul’sFishing Kites (PFK) Nighthawk.

Although it’s a joy to fly I have never got on with it as a camera sky-hook because the wind-speeds it works in are characterised by sickening turbulence making photography almost impossible as the rig swings about like a floundering ship on a stormy sea.So it looks like Bft 6 is ‘too windy for KAP’.

On the packet it says the PFK Nighthawk will fly in up to 40knots, that’s the kind of weather I like to keep out of, if true this kite could push the KAP envelope into Bft7 or even 8!

Today I was out at between 10 and 11 so I was dealing with a rising wind of 25 mph gusting to 30. The violence of the gusts was such that the kite would heel over and then begin to spin forcing me to run down wind to prevent a powerdive into all manner of obstructions. It’s difficult to describe how stressful this situation can be. The pull on the line in these conditions is severe, tying the line off was not an option as the obvious anchor points I could see would place the madly veering  kite in the way of wires, the mill itself or houses whose roofs looked ever more fragile compared to the hammerforce of the diving kite!

The 2 flowforms I have match the chart for the parafoil 7.5 pretty closely although the HQ 2.0 at 26mph is really on its beam ends!

So my fellow KAPers advise this is the answer:

The tough little delta flies well in most brisk breezes but can’t lift a rig until it’s biting into something like Bft5 or better. It has 2 alarming chacteristics: one is the racket it makes and the other is its tendancy to overfly the flyer. The noise turns out to be a good indicator of its lifting capacity, if the noise stops so has the lift. The steep flying angle means it’s a kite that demands the attention of the flyer once the rig is committed to it’s care; it’s a very mobile kite which constantly reacts to changes in wind strength by tracking to left or right. The small surface area means that once the required lift is lost, even if only by a fraction, the rig drops really fast!

This is what I get when I fly my rig from the PFK:

My rig swings about madly as the line is jerked about by the kite! The hit rate for sharp images in these conditions is practically zero! I think it’s fair to say (certainly for these parts anyway) that the bigger the wind the bigger the variation in wind speed.

So what I’m after is a kite that is tough enough to take the battering of a big wind but also stable enough to bridge the lift gaps big winds tend to have. It’s certainly not simply a matter of a bigger kite as the multiplied forces would get painful pretty quickly. My thoughts on dealing with the big range of forces in acting on a single kite (trains of kites is another matter!) tend towards 5 ideas:

1. Elastic Bridle. The idea was desrcibed at KAPiNed10 by Bernard-Noël Chagny of an eleastic bridle to soften the effect of changes in wind pressure on a rokkaku sail to reduce the stress on the spars: the idea being I could fly a slightly bigger PFK and have the eleastic spare the extra stress on the kite and the increased sail area save the falling rig.

2. A ‘reefable’ kite. Sailors tell me reefing is the way to go. When faced with too much sail before the wind sailors’ reef’ in the sail area to reduce the risk of having the boat blow over. Many kites are adjustable but my favorite is the Brogden prize winner from 1908 for no other reason than I think it’s a very pretty kite in the sky. I have a half size one in aluminium and ripstop and it’s something of a performance to tune it to the wind and it has a nastly short line ground loop characteristic. The 5 sails mimic the sails of a square rigger ship, in theory I can vary the tension on each sail in much the same way as reefing. In practice this kite is a bit of a handful and can take an age to get dressed for the wind and even then its very easy to get it out of balance as it has so many adjustments!

In the picture is Charles Brogden with the nervous look typical of a kite flyer who is expected to ‘perform’ in public; only he knows the true extent of the risk in what he is about to do! This photo is so evocative of the ‘dawn of flight’ era, at the time kite builders and flyers above all others were making the dream of flight real, kite designs were leading edge technologies in a world still largely powered by steam and horse. Nothing would come close to this golden age of kiting until Dominina Jalbert created the parafoil and opened up a whole new world of wind powered sports on land and water 50 years later.

3. A smaller ‘softer’ flowform. Reducing the area from 2m2 to something less with a bigger wind spill might work. Simply reducing the size alone would not be enough as these kites have a sort of ‘paper bag’ flight dynamic when they are overblown.

4. Drogue the life out of the kite. It’s possible the PFK can be damped to a degree by a carefully towed drogue. I have seen this work well on the flowform kites, my hope would be that the drogue slows down the tracking of the kite and thus reduce the movement of the line.

5. Gyro stabilisation of the rig in the roll and tilt axis. A ‘roll rig’  is very effective at cancelling rig movements in ‘reasonable’ winds at the cost of a slight increase in weight. Having seen some of the movements ( including 360s around the flying line!) I’m not sure a roll rig could keep up but its worth a try!

So with these ideas in mind I’ll probably start with the drogue, then borrow a roll rig and see what happens next time the wind gets fierce.

Now of course the wind has dropped to nothing and all thoughts of fighting with it are gone:

Out on the Eastern side of the fen todays Westerly, such as it was, gained full strength and the X1 was aloft again.

The full size shots are at:

http://www.flickr.com/photos/bblakecambridge/4974115057/

http://www.flickr.com/photos/bblakecambridge/4975026470/

About billboyheritagesurvey

Heritage worker
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7 Responses to PFK all the way?

  1. KAPshop says:

    Something else was “wrong” too: the direction of the wind, East. I still don’t understand why but I always have trouble when the wind is blowing from that part of the world. Try the PFK in a storm coming from the west.

  2. You may well be right but I have the same experience with Northerlies too! I’m certainly not giving up on PFK and Noel’s elastic briddle might make a big difference to it. I’m on the hunt for the right kind of elastic! My idea is to set up a loop of slack flying line with the bungee taking the strain so that the kite will be restrained if it reaches the elastic limimit. If nothing else it will smooth the line movements.

  3. Julie Edwards says:

    Interesting.. I’m not a KAP’r but down where I live there are a great many kite boarders who ‘fly’ in all sorts of winds.

    t’s quite clear whilst they are in the water the power is soaked up by the pulling but the bit i am interested here for you is that when they set up on land, their 4 line kites have additional lines to allow them to be de-powered. They seem to stand in the field is quite high winds with the kites set and fastened to their harnesses and seemly very stable in the sky.

    Now of course the kites are not as high in the sky as you want them but they do tend, when de-powered to fly at a high angle.

    Are there not some techniques you can apply here?

    • Very good point Julie! My goal here is a bit different to the 4line sport kiters: they feather off the trailing edge to the point where the kite is almost acting as a flag to park it. I can’t do this because I need lift! It is possible to ‘de-power’ to a degree with this kite as it has 3 tow point attachments which ‘blunt’ its angle of attack. The 4 point cross-bar control method is very effective and there is good video evidence of this but quite how I could get my rig held aloft I’m not sure.

  4. Ramon says:

    Hi Bill,

    Was just checking on video footage of the Brogden kite and one of the first hits was your blog. No video, but at least some info on the Brogden. Together with the Cody War Kite and some other designs this Brogden kite is a true classic. I only saw it once when airborne back in 2005. As mesmerizing as my own Cody Extended kite.

    I doubt if it will be a potential KAP kite due to the reasons given. But still, you can’t beat the looks.

    • Nice of you to comment Ramon. You did really well in the snow! Perhaps it’s time to build a ‘better Brogden’, I think it might be a case of working with the full size design and finding a way of getting a fixed fabric tension for simplicity when setting the sails. My idea for the half size one was that it would fold out from the centre spar like an umbrella but being so small some of the spar lengths were very short and ended up with more ‘jonit’ than spar. But maybe I should put the effort in to a 3/4 size version of one of Ralf’s lovely ‘Kapfoil’s though. .. a bit more useful!

  5. Ramon says:

    I am re-reading your blog, starting with this topic.

    As you may know I also have a PFK. Frankly I am quite happy with it. I don’t really care that much about the noise it generates – I consider it a part of the deal. I only fly it in winds from a good 5 Bft to a stiff but stable 6 Bft. I’ve also flown it in 7 Bft winds but my experience is that winds higher than 6 Bft are always dirty (no matter from what directions they blow) and not usable for KAP. A total waste of time.

    The first time I flew my PFK was in such a wind – 24 knots, probably higher. This is what it looked like:

    Kiwi Nighthawk testflight from Ramon Pallares on Vimeo.
    My guess is that other kites will show similar behaviour and taking measures that really work is far from easy.

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