August 2007

Newsletter, August '07

Too Slow. - and it's Thomas Jefferson's fault

Kite flying has been taken by a great schism- like Sunni/ Shiite, Catholic/Protestant.

In it's earliest form the split was single line/two line then four line sects came along and now there even five line believers.   

A useful label for all multi-line flying is 'controllable' by the view that the reason for having more than one line is so as to make kites steer-able.  .

Of course fighter kites may then be eligible for both groups, depending on the precise definition of 'controllable'- but I'm not going there today as this is an 'angels on the head of a pin' type digression.

Generally, controllable and single line kites attract different groups of people, and different clubs, publications, shops, manufacturers and events increasingly service these.  This is inevitable, no matter the attempts by various flier organizations (The AKA for example) to cater for both sides.  And it's sensible, mum and dad going to a local kite day with their pre-teen children do not have much in common with the kitesurfing scene or extreme buggying. 

Now I'm hoping there'll have to be a new definitions for the types of kite they each fly though because this definition- single line kite versus controllable kite- is under attack from both sides.

The Slarc as described in an earlier newsletter, is a high performance traction kite that is being developed to fly on a single line with radio control of pull and steering.  The goal is to make kites for all traction applications, but particularly to make large ones suitable for yachts.  Using a single line overcomes the inherent problem of multi-line winch systems - holding precise length registration between lines under different tension as they are let out and pulled in.- and it almost eliminates the main cause of the line snarls, a major safety concern.   This work is progressing slowly but well.  There seems to be only one main problem remaining- how to accomplish power control without excessive battery drain, - and there are promising leads to this. 

The Slarc is (or will be) a controllable power kite that has just a single line.

And now, as also touched on in an earlier newsletter, steer-able single line display kites are on the way.  The goal here is not full control in the sense that power kites require, but just the ability to reposition show kites without shifting their anchor points.   With this feature it will become possible to fly more and larger kites closer together at kite festivals with less hassles and greater safety. The first kites that this is to be applied to are pilots- shifting the pilot also shifts the kites below to a useful extent- but I'm now intending to take this further and actually steer the main kites as well.  The approach I'm following has come out of work on the Slarc steering system.  Also being ram air inflated soft kites, Slarc steering principles cross over to display kites.  Unfortunately the devil is indeed in the detail. The difficulty is in finding simple aerodynamic effects that achieve predictable and proportional steering across a wide speed and angle of attack range.   Apart from Lilienthal's pendulum steering (later used by Chanute and others), the pioneers of heavier than air flight never did find any such and eventually developed the complex pilot operated multi-axis system requiring ailerons, elevators and rudder that aeroplanes now use.  This level of complexity is not practical for pilot-less kites. Out of six different layouts tried so far, two work satisfactorily. I don't think I've yet found the best system.  We're doing this testing by my standing on the rear seat of the van with my head out through the sunroof holding things in the wind stream- "we" in this context because Elwyn does the driving- see photo. It's working well because there's no need to wait for wind (it's winter here so there isn't any) and it's far away from spies- err, except heavily disguised ones- see other photo.

But optimal or not, there should soon be single line show kites that are also controllable.

Too slow? - Yes I'm taking too long to get these things working- and yes, it's Thomas Jefferson's fault.  I try to live by his adage to the meaning that 'if you don't ever waste a minute you'll never be dissatisfied with what you accomplish.' Well Thomas, I am dissatisfied- but have I ever wasted a minute?  Hmm, how could a kite flier ever answer that one?

Sticking my neck out though, I expect to have steer-able pilot kites by the beginning of the next (northern) season.

Peter Lynn. Ashburton, New Zealand, August 1 '07

PS.  To those who have asked for plans for the stable single line non-steer-able version of the Slarc as promised in April:

When I started to get them into understandable form I realised how difficult it is to describe how they are made.  They are complex and made with techniques that not even experienced kite makers will know.  So, to add some simplicity I decided to change to span-wise panel construction.  Slarc 8 and before used chord-wise panels, requiring 43 different patterns for each kite. With span-wise panels there are only 10 total and the construction is much easier (cuts time down, for me, from four days/kite to two)- but the design is more difficult.   I have now made two span-wise panel prototypes- 9 and 10; they are flying, but won't fly with much less than 100% inflation.  I need to do at least one more prototype before inflicting this design on anyone. 
Watch this space!