KAP in Bft 5

Big wind One look at the forecast today was enough…Gale force is not KAP force at all! Opinion on the Trooper confirms it needs a tail when flown in turbulent (squirelly) flow, and is tricky to handle on a short line. The ease of handling in the main flow is a strong advantage for it over the PFK which, although easier to launch and recover, has vicious pull and violent cross wind movement in Bft5. They are designed for different purposes and have advantages in different ways. Faced with the prospect of ‘iron bar’ flying the Trooper is a welcome tool, once it’s in clean air a light auto rig can get to work to make the best of the opportunity, it’s not a powerful kite and it operates almost continuously on a slack line so a heavy rig ends up a long way down wind before gaining any useful height. It’s something of a surprise to find high speed kite design hits compromises like this, I would expect stronger flow to get me more lift but the reverse is true owing to the turbulent nature of the stronger flows and the reduced sail size to avoid overpowering. Of the 3 kites I have that will go in Bft 5 I can report how they behave, the Didak Explorer bows out 1st but is a great platform in a clear flow, it heels over and flies on its ear when overblown, a clear warning of a rising wind. The 2 deltas are much more lively than the flowform with a ‘hunting’ movement  as they follow the wind.

      • Dan Leigh uses a subtle low AoA, feathering of the wind to achieve lift without undue stress on the line. It is a difficult kite to handle at launch and recovery, if flown tail-less.
      • Paul Barnes uses a heavy duty approach with an over sized hardwood dowel spreader spar and heavy duty ripstop. It is a really strong wing which uses mass and flaps for stability but pulls like a horse and, although easy to let fly it pulls like a runaway train on recovery.

The table below is very loose in terms of the wind speeds and the pull values, I’m usually far too busy in these kinds of winds to keep accurate records but experience tells me these are pretty close ‘real world’ values. I usually commit to memory the max values from the wind record after I have everything back on the ground, bagged and back at base. I’m still learning the Trooper’s flight characteristics so the max value is from David Mitchell’s report from 2008. Apologies for mixed units, despite being metric since 1971 I still think of speed in mph (because all the road signs round here are still in mph).

Beaufort 5 kites for KAP
‘Nighthawk’ ‘Trooper’ ‘Explorer’ 1.6
Paul’s Fishing Kites Dan Leigh/ITW Ivo van Olmen/Didak
Type: Heavy Duty Delta High Aspect Delta Flowform
Flying angle: Steep Slack line/steep Low
Advertised wind speed: 10-46 mph 6-24 mph 6-24*mph
Achieved KAP speed: 15-28mph 8-25mph 10- 20mph
Line pull at Bft5: 5-10kg 2-5kg 5-10kg
Approx Lift capacity: 1.kg 0.5kg 1.3kg
Launch characteristic: Down wind release. Risk of ground looping if tail-less. Easy in clean flow. Difficult in wind shadow.
Recovery characteristic: Tight line: walk down. Slack line: hand haul. Risk of ground looping if tail-less. Tight line: walk/ winch down.
Tail: Not required. Recommended in blustery conditions. Drogue on a ‘Y’ line stabilises yaw.
*assumed from stated ‘Bft5’

A third approach to the high speed delta problem is the dynamic spar idea. Mike LeDuc has perfected this for the 9′ Levitation. My attempts to replicate his success with a crude copy have been ‘mixed’, the effect is noticeable but the reaction speed was never enough to avoid the kite becoming unstable in repeated gust cycles.

Bft 5 pushes kites as a photographic platform to the limit. The forces involved can be sudden and violent as the chaotic nature of local vortices in the 60m AGL zone increase with wind speed. If I had to advise a beginner on a Bft 5 kite (although the best advice would be to find something else to do until the wind drops) I would have to recommend the PFK Nighthawk,  not because it’s easy to fly (it is) but simply because of its stability at launch and recovery. Flying in wind-speeds around the 20mph mark is not for the fainthearted no matter what is put before the wind. Bft5 needs to be treated with respect as it is a harsh place for a kite to live in and care is needed to plan safe recovery- gloves are definitely required!

B

About billboyheritagesurvey

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4 Responses to KAP in Bft 5

  1. When flying the Nighthawk in strong winds, do you attach the line through the top of the three eyelets on the keel?

  2. I’m using the Super Kite which is a little smaller than the Nighthawk. I almost always use the top hole (nearest the nose) for KAP and often feel it could do with another hole slightly higher. Some time in the past a couple of KAPers have said they have only ever used the bottom hole which was something I couldn’t quite get my head around as surely the PFK’s are strong wind kites for kap and the hole nearest the nose is the recommended on to use for stronger winds.

    It would be interesting to see a comparison someday between the Nighthawk and the Superkite tested in the same conditions.

  3. How do you find the PFK Superkite?
    The smaller size should be an advantage over the Nighthawk in Bft 5. I have kept the Nighthawk for the worst of the wind at it has begun to fray badly on the trailing edges, I got to the point with it where I felt I didn’t want the physical workout getting it back, never mind the crazy motion it can have in a dirty flow- it seems to be able to cope with a big wind but at the cost of stretched line and frayed fabric.

    I’m becoming a fan of Mike LeDuc’s DS on the Levitation, it’s early days (I have only had it a week) but it lets the 9′ delta take bigger winds without the risk of fabric stretch which is the fate of the ‘over sparred’ Levi if its left out in a fresh breeze for too long..

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