US Hawks Hang Gliding Association

Having fed key notes to an AI assistant and added some after its response ChatGPT wrote:Captive-Ellipse Hang Gliders

This topic thread explores a unique design approach to hang gliders, centered on the innovative use of a tensegrity-based structure instead of a traditional keel beam. The following concepts define this special focus:

• No Central Keel Beam: Unlike conventional designs, the stability and structure of these hang gliders are derived entirely from the interplay of tension and compression between the elliptical frame, the taut sail, and the central posting system.
• No bowsprit.
• No conventional crossbar or spreader.
• Tensegrity System as the Core: The kingpost and queenposts act as a floating beam system, stabilized by stay lines radiating to key planetary points on the rigid elliptical frame. This arrangement supports the pilot and provides structural integrity without a solid keel.
• We may explore a simple framed TCF (triangle control frame) that acts as a tensegrity beam and function as a floating upper and lower posting system, so one does not see a conventional king posting.
• Pilot Integration: The pilot hangs directly from this dynamic tensegrity system, experiencing the balance of forces created by the interplay of sail tension and frame rigidity.
• Ribs, baton, stuffers, airfoil curving? A world of exploration may be available here.
• Single sail or double sail Explore both.
• Elliptical Innovation: The fully enclosed elliptical shape—featuring both leading and trailing edges—ensures aerodynamic efficiency. The narrow wing tips define the elongated ellipse and help distribute loads evenly across the sail and frame.

This thread invites creative exploration of circle-ellipse and non-circle-ellipse framed gliders under this concept. TPHG (Tiny Packed Hang Gliders) studies are especially welcome, alongside non-TPHG designs. Enthusiasts, experimenters, and designers are encouraged to share insights, questions, and progress as we collectively unfold the potential of these revolutionary structures.

• Elliptical Frame: Depicted as a rigid outer loop.
• Sail Fabric: Highlighted as the taut, load-distributing element that connects to the frame.
• Kingpost and Queenposts: Displayed as three vertical members (one central, two flanking) forming a load-sharing system.
• Stay Lines: Shown as radiating thin lines from the kingpost and queenposts to specific points on the elliptical frame.
• Pilot: Positioned in the center, hanging from the tensegrity system.

• The ellipse is a bold, continuous loop.
• The kingpost and queenposts are drawn as slender lines within the ellipse, slightly inclined for visual balance.
• Stay lines are drawn as thin, angled rays connecting the posts to the ellipse.
• The pilot is represented by a small, simple figure hanging from the midpoint of the kingpost.

• The elliptical wing is tilted at a slight angle to convey forward motion.
• The sail is taut, and the stay lines are visibly tensioned.
• The pilot hangs suspended beneath, with wind currents implied by light lines or gradients flowing around the structure.

Here’s a creative draft for a caption to enhance engagement and understanding:

TCF as tensile-float beam in CEHG.

TCFasFloatBeam001.jpg (20.75 KiB) Viewed 302 times

The Floating Beam of the CEHG Universe
Behold the Tall Central Framework (TCF, triangle control frame), tensionally suspended in perfect balance! Acting as both the kingpost and queenposts, this innovative structure is anchored to the elliptical frame through a web of taut stay lines. This tensegrity masterpiece forms the heart of the Captive-Ellipse Hang Glider, supporting the pilot in an elegant dance of forces.

Explore, innovate, and share your ideas for this bold reimagination of flight!

User Prompt wrote:Two slightly overlapping circular or elliptical rings for a glider begin to show the development of a keel in the glider. Otto Lilienthal approximates such geometry in his Normalsegelapparat; but he did not use the captive arc or captive circle principle; he used radiating ribs to tauten the sail fabric. Discuss all this.

Response wrote:The idea of slightly overlapping circular or elliptical rings as a structural element in a glider design provides a fascinating avenue to explore aerodynamic and mechanical principles. Here's an in-depth discussion of this concept in the context of hang glider development and comparisons with Otto Lilienthal's pioneering designs, specifically his Normalsegelapparat:

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Concept of Overlapping Rings in Glider Design
1. Overlapping Rings as a Keel Development:
- The slight overlap of two circular or elliptical rings creates a structure with potential to serve as a keel-like element.
- This configuration could distribute loads symmetrically and provide inherent structural stability without the need for a central, linear beam (as is common in conventional designs).
- The overlapping geometry also has the potential to create zones of tautness where fabric sails can be tensioned effectively. These tensioned regions, formed between the arcs of the rings, would create aerodynamic lift surfaces.

2. Captive Arc or Circle Principle:
- The "captive" principle involves using a hard frame (elliptical or circular) that is kept in shape by stay lines and the tension in the sail.
- This eliminates the need for internal ribs or beams radiating outward, reducing structural weight while maintaining aerodynamic efficiency.
- The overlapping rings could provide unique zones where such captive structures could "lock" into a desired shape and provide multiple attachment points for rigging, further enhancing the flexibility of the glider's design.

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Comparison with Otto Lilienthal's Normalsegelapparat
1. Normalsegelapparat's Radiating Ribs:
- Otto Lilienthal's Normalsegelapparat used a central keel beam and ribs radiating outward to support a fabric sail. These ribs were crucial in shaping the airfoil and providing structural integrity.
- Lilienthal's approach relied heavily on the uniformity of rib spacing to ensure consistent tension in the sail fabric, which directly influenced the aerodynamic performance of his gliders.
- This method was effective but added weight and complexity to the design.

2. How Captive Arc Differs:
- Unlike Lilienthal's radiating ribs, the overlapping rings and captive arc principle focus on tension and compression relationships within the frame and rigging system. This allows the structure to "float" in a tensegrity-like balance without the need for rigid internal ribbing.
- The sail fabric in a captive arc design becomes integral to the structural system, held taut by stay lines connected to key points along the overlapping rings.

3. Aerodynamic Evolution:
- Lilienthal's designs represent an early understanding of aerodynamics and structural integrity, but they were constrained by the materials and engineering knowledge of his time.
- The overlapping rings approach could advance these concepts by enabling lighter, more flexible designs with the potential for modularity and portability (such as in modern TPHG systems).
- The elliptical or circular arcs allow for a more organic integration of aerodynamic principles, potentially creating smoother airflow over the surface and reducing drag compared to ribbed structures.

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Potential Applications and Challenges
1. Applications:
- Such a design could be used for ultralight gliders, parachutes, or even micro-aerial vehicles where weight and simplicity are critical.
- The dual-ring system might also allow for innovative control systems, where shifting the tension in specific stay lines could alter the wing shape dynamically, providing new methods of flight control.

2. Challenges:
- Achieving the right balance of tension and compression within the rings and stay lines could be complex. Excess tension could deform the rings, while insufficient tension might lead to a collapse of the sail.
- Material selection is crucial—both for the rings (to ensure lightweight rigidity) and the stay lines (to handle the dynamic loads without stretching excessively).

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Conclusion:
The overlapping ring concept and the captive arc principle offer a modern reinterpretation of Otto Lilienthal’s structural ideas. By reducing reliance on radiating ribs and using stay lines for structural integrity, the design could pave the way for lighter, more efficient gliders. Lilienthal’s pioneering work, particularly with his Normalsegelapparat, remains a cornerstone, but these innovations represent how advancements in materials and design philosophies can transform his foundational ideas into futuristic applications.