Single skin AWE

The single-skin lower mass favors a lower cut-in wind speed. So a significant advantage of a SS kite is a drastic decreasing of required takeoff and landing operations.

Lower Cut-in means less frequent landing and recovery operations
But the recent article
Vertical Takeoff and Landing of Flexible Wing Kite Power Systems
suggests lowering the cut-in of LEI, ram air and other kites.

Whilst also highlighting the complexity of handling this drone assist method requires.

Iā€™ve done very rudimentary drone assist experimentation. Makes total sense. Iā€™m all for the idea!

But an increased time in the air hastens UV-damage of kite and line without generating significant power during that time. To make a decision on whether the advantage outweighs the disadvantage you would have to look at windspeed data I would think.

What is the lifetime of uv-stabilized kite fabric out in the sun? Itā€™s measured in the low digit thousands? Youā€™d be lucky to get half a year of continuous flying out of that.

Iā€™d be happy to be proven wrong.

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Sailboat sails seem to last 2.5 years. Iā€™d think most of the low hangig fruit has been picked here, and that a kite could not easily last longer.

If we have an automated deployment machinery for the kite(s) we might also assume that only half the time is windy enough for production, furter extending that. In northern and southern parts of the world, the windiest periods coincide with less amount of sunlight (winter), another factor to extend lifetime in practice.

For me it seems simpler to keep it flying year round than implementing such deployment machinery. Both are very hard though.

https://www.cruisingworld.com/how-long-do-sails-last

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Cut-in wind speed concern should be considered for the whole flight, not only during takeoff (not landing I put by mistake) and landing operations.
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Indeed the lifetime of a flexible kite is low as AWE operation is most of the time. Appropriate and probably thicker fabrics with a better UV resistance should be studied. Rigid wings have a huge advantage in regard to the lifetime, excepted in case of crash.

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Some posts about single skin kites:

OZONE KITES EXPLORE V2 Teaser / Jks-kitesurf

At 0:36 from the beginning, the structure of the wing is shown, with its ā€œram air wingtipsā€ which I think improves profile and performance with little extra fabric just for the leading edge and the cords, most of the wing remaining single skin.

A similar structure is presented on:

La comparaison by Flysurfer: Peak 5 VS Peak 4 | Flysurf.com

These single skin kites seem interesting for AWE use because the profile remains efficient while the wing keeps its lightness.

Specifications

Size

4m

6m

8m

10m

12m

Weight

.65

.81

.91

1.06

1.21

Bar Size(cm)

45

45

50

50

55

Line Length (m)

20

20

22

25

25

Number of Cells

25

25

25

25

25

Projected Area (mĀ²)

2.89

4.36

5.86

7.30

8.76

Flat Area (mĀ²)

4.00

6.00

8.02

10.00

12.00

Projected Aspect Ratio

2.68

2.83

2.96

2.96

2.96

Flat Aspect Ratio

4.21

4.44

4.64

4.64

4.64

Root Chord (mm)

1180

1408

1593

1779

1948

Flat Span (mm)

4146

5210

6157

6875

7530

1.21 kg and 12 mĀ² of flat area for the 12 m. The aspect ratio is rather high. I would like to know the lift to drag ratio. What not using giant wings like this for AWES?

See also single skin paragliders like

SPECIFICATIONS

SIZES 16 18
Number of panels 39 39
Projected area (mĀ²) 13.9 15.6
Flat Area (mĀ²) 16 18
Projected Span (m) 8.0 8.5
Flat Span (m) 9.5 10.1
Projected Aspect Ratio 4.6 4.6
Flat Aspect Ratio 5.6 5.6
Root Chord (m) 2.0 2.1
Glider Weight* (kg) 1.3 1.4
In-flight Weight Range (kg) 55-90 67-105

The aspect and area/mass ratios are still higher. Perhaps these would make excellent scalable high lift to drag ratio AWES, with reinforced fabric?

See also

An excerpt:

7. How does a mono surface work? A little flight mechanicsā€¦

A wing is made up of an intrados (the ā€œundersideā€) and an extrados (the ā€œtopā€).

Vue du profil d'un parapente classique avec un intrados et un extrados

On single-skin wings the upper surface stops just after the leading edge.

Parapente mono surface schƩma explicatif vue de profil

In terms of flight mechanics: the air flow linked to the movement of the wing generates lift: by depression on the upper surface (approximately 70% of the lift) and by overpressure on the lower surface (approximately 30% of the lift). So even without a lower surface most of the lift is generated: it flies!

The behaviour of this type of wing is a little different from a classic paraglider. This means that learning to fly with it has it specificities. This is an excellent first step into the world of free flight with paragliders, they are easier to inflate and take-off than standard wings thanks to their very light wing weight, between 1kg to 2kg (a ā€œclassicā€ mountain wing would weigh between 2kg to 4kg).

Can we deduce that the lift is reduced for a single skin paraglider?

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