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|
|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!