Re: [AWES] Fractal Kixel "hairnet" lifter kite set
- That Reinhart Paelinck paper is an interesting find. I have been looking
for prior art on inflated annular wings. The basic inflated doughnut or
toroid can be very strong for its weight. The tyres used on nearly all
road-going vehicles are an example.
Some examples of morphing the basic toroid into an aerodynamic shape
include the disc shaped wing made by Lee Richards here;
The Aerodynes illustrated here are another example
Some model aircraft with annular wings. The ringflieger -
Cellular kites all use the basic principle of the strength of the
When Hargrave was developing his box kite he found that two boxes
separated from each other produced the most stable result. He also tried
annular designs but I suspect the materials he had available in 1893
contributed to him finding the box shape to be best.
The circoflex took another 100 years (exactly) to develop because the
single annulus requires a very complex tether arrangement to be stable.
I suspect Reinhart would have a more stable kite if he used two like
Something like a Cody could be made using 4 inflated annuli. If there
were central spars running down the centre of each pair of annuli and if
those spars protruded beyond the front of the front annuli then they
could act as tether secure points. I envisage a 3 tether system. One
tether goes to the bottom front edge of the right back annulus. The
second goes to the left back annulus. The third divides near the kite
and goes to the front of each central spar. The front tether can be used
to retract the kite at great speed. In the power phase all three tethers
are used to steer the kite and control its angle of attack.
I think Reinhart's proposal for inflating the structure is not optimal.
I think a series of pure toroidal shaped support rings would be best.
They would be spaced apart with inflated spars and then skin would be
stretched over this inflated skeleton. This way each toroidal bladder
could be inflated to a different optimum pressure.
I accept that Dave's proposal of using flat sheets would cost far less
initially. However, the inflated structure would have such superior
aerodynamics it is possible that the cost of energy would be lower once
a factory to mass produced an optimized design was established.
The superior aerodynamics also means that a dancing pair of these
inflated kites could tow ships in any direction and at speeds many times
that of the wind. They could also pull a Kitegen type carousel
throughout the full cycle - no clumsy scrabble to get the kites out of
the power window every cycle.
A pair of small propellers on the central spars would overcome the
launching and landing difficulties Reinhart mentions with his "balanced
kite" proposal. (What I have been calling dancing pairs.)
Another inspiration from his paper is including both the power and
retraction phases in each cycle of the kite looping through the sky. His
diagram shows the kite flying in a circle. However, that causes problems
with the tether tending to twist. A figure of 8 can still be done but
there would be 2 power/retract cycles per cycle of flight. Taking it to
its logical conclusion it is like turning the figure of 8 flight path
from the vertical plane and onto its side on the horizontal plane. So
the kite would sweep from one side of the power window to the other at
more or less a constant altitude. It would pull out the tether in this
phase. At the end of phase 1 it would turn towards the reel and be
retracted, but again at constant altitude. Phase 3 is another power
phase going back across the power window in the opposite direction.
By keeping the kite at the same altitude the whole time we avoid
problems with wind shear. We just choose an altitude where the wind
speed suits the kite. When a suitable height can no longer be found the
kite is changed.
The speed of the retraction phase is enhanced because we are taking
advantage of the momentum of the kite built up during the previous power
Another advantage of the short phase (or 4 phase) idea is reduced tether
wear. The reel is made sufficiently large so that during normal
operation the tether is in direct contact with the reel drum so that
there is no tether to tether contact. It should also be possible to keep
the tether tension roughly constant so that there is no slippage of the
tether on the drum because of stretching as the tension varies.
Hope you are all as excited by the potential as I am!
On Wed, 2012-05-16 at 13:48 +0000, roderickjosephread wrote:
> I envisage a kite like Reinhart Paelinck designed as a good lifter
> for tracking the wind, inherent stability and not getting tangled.
- Robert,To fully cover ring-wing designs, be sure to check out the Pop Can kite type. It does not have a bridle at all, and self relaunches really well. One can make a small autonomous AWES very easily with such a kite to initiate a launch cascade. I did not find a single definitive link for the Pop Can, just scattered content.The first link you shared was a real freak show of rare discs and rings. I would add a review of modern ring wing concepts from the likes of NASA and elite aeronautical engineers like Kroo. My own contribution to this concept space was the Flying Sphere, developed in the late eighties.daveS
- Robert, your description of active bladder spar control to manipulate dynamics is very interesting. Beyond that I struggle to imagine how the one architecture could be used to perform so many functions. As ever I am simple and need drawings to best understand the whole story.