[dhmartens]

They are deleting all references to the telescopic hang glider so I will use screen captures.
blocked
https://www.reddit.com/r/Hanggliding/co ... ppreciated
Shga has decoded text reposted here:
I am battling a real effort to censor this telescopic hang glider, it is real, I must say I have invested a great portion of my life and efforts and my father was at Lt. Colonel, If I am to stop these efforts you must kill me, I have taken this into consideration.

exjetmachina
•5y ago

I flew for Bill Bennett. I tested the 6b, 8, and the Mariah. The Phoenix 8 is a dog. If you decide to fly it make sure the leading edge tube is one piece. That is, make sure it is not two tubes, that the aft tube is not slightly larger and extending a foot forward past the crossbar. A 10 to 1 lever that broke the wing and almost cost my life: Sylmar 1977. Trip Mellinger (Bennett’s VP} introduced parachutes for hang gliders later that year.

USHGA #10111

[JoeF]

Gap and wobble stop::

Telescopy without wobble stop in pack, when ample gap is provided, will ease tubing ordering, maintenance, assembly, disassembling, cleaning, end protecting. In some UPHGs amble gap of adjoining telescopic tubes may be a way to go.

---

[dhmartens]

hand gliding 1977 : Telescopy without wobble stop in pack, when ample gap is provided, will ease tubing ordering, maintenance, assembly, disassembling, cleaning, end protecting. In some UPHGs amble gap of adjoining telescopic tubes may be a way to go.
In the context of 1977-era hang gliding design, particularly regarding Unpowered Hang Gliders (UPHGs), the use of telescopic tubing with an "ample gap"—and notably without a "wobble stop" or internal centering device—was a practical design choice for several reasons:
Design and Functional Benefits
Simplified Maintenance and Cleaning: An ample gap between adjoining telescopic tubes allows for easier disassembly and cleaning. This prevents the accumulation of grit or salt, which can cause binding or corrosion in tighter-fitting aluminum components.
Ease of Ordering and Assembly: Using standard tubing sizes with a generous clearance reduces the need for precision-machined "piston" or "gland" style interfaces. This simplified the manufacturing process for the many small-scale manufacturers active in 1977.
End Protection: Larger gaps provide enough space to integrate protective end-plugs or caps without interfering with the sliding action, protecting the tube ends from damage during repeated assembly and disassembly.
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Operational Impact on UPHGs
Manual Portability: For gliders designed to be packed into small bundles (the "pack"), removing the "wobble stop" (a device typically used to eliminate play between tubes) allows the tubes to slide more freely, speeding up setup and breakdown in the field.
Mechanical Tolerance: In early hang glider designs, a gap—sometimes as much as 3mm—could exist between nested wing components without significantly affecting flight qualities or causing excessive aerodynamic drag.
Lubrication: A wider gap allows for the application of lubricants like lithium grease or Noalox to ensure "buttery smooth" operation, even if the tubes have minor imperfections.
While modern high-performance gliders often utilize tighter tolerances for structural rigidity, the "ample gap" philosophy of 1977 prioritized user-serviceability and rapid deployment.
YouTube
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Would you like to explore the specific tubing materials or standard dimensions commonly used in 1970s hang glider frames?

[Chris McKeon]

Man I see this Short Pack Deal as an option that could influence My decisions when hopefully when I Fly My Predator Cross Country again. It would give Mr a Piece of Mind knowing when I was to totally Blow it while Flying X-C. If I were to be forced to land say I don't know, say I was to have to land I do not know? Possibly 5 - 15 - 20 or thirty Miles from the nearest Road. Then heck I could just make a call on My Cell Phone. Short Pack My Predator. Turn My Glider into a Back Pack and head on out.

[dhmartens]

Converting an old hang glider, such as the Ultralight Products (UP) Predator from the 1980s/90s, into a telescopic "short pack" that folds down to 5 or 6 feet is technically possible but generally unsafe and not recommended without advanced engineering and structural modification.
While modern beginner gliders (like the Wills Wing Falcon) are specifically engineered with short-pack options—folding to 6–7 feet—older high-performance flex-wings were not designed for this type of disassembly.

Here is an analysis of the feasibility and risks:
1. Structural & Engineering Challenges
Leading Edge Tubes: Converting a standard single-piece leading edge into a 3-piece telescoping assembly requires precision-engineered inner sleeves (spigots) and locking mechanisms to maintain rigidity.
Sail Integrity: The sail (dacron or mylar) is cut to fit a specific frame shape. A short-pack modification changes how the sail is tensioned and folded, which may cause wrinkles, improper shape, or premature damage to the sail material.
Weight & Complexity: The added telescoping hardware—locking pins, sleeves, and doubled-up aluminum sections—adds weight to the glider, negatively affecting handling and flight performance.
2. Safety Risks
Structural Failure: The leading edge is under immense pressure during flight. If the telescopic joints are not designed perfectly, they can fail, leading to catastrophic structural failure (wing collapse).
Flight Characteristics: Old gliders were already difficult to fly by modern standards. Modifying the airframe can introduce unpredictable flight characteristics, such as heavy handling or uncontrollable stalls.
3. Practical Alternatives
Short-packing (Without Modding): Some older gliders allow the battens to be removed and the keel to be folded slightly to reduce the length, but rarely down to 5–6 feet. Typical packed lengths are 17 to 21 feet.
Buy a Dedicated Short Pack: If you require a 6-foot pack length for travel, it is much safer and easier to acquire a modern, short-pack compatible wing designed specifically for this purpose, such as the Wills Wing Falcon 3 or 4.

Conclusion: Modifying an old Predator to short-pack is a high-risk project for experienced experimental aircraft builders only. It is not considered safe for a standard pilot to attempt this on a vintage glider.

Update of my prototype, in a daring rescue attempt I have recovered all of the missing crossbar and last 1/3 of the leading edge.

[JoeF]

Neat post, Doug

---

Mod-U / Joe-Cup Tubular Interface Development Discussion (Complete Transcript)

============================================================
USER 1
Encyclopedia of accessories for tubular works: caps, plugs, couplers, flanged couplers, anti-wobble rings, stops, etc.

ASSISTANT 1
Provided structured encyclopedia of tubular system accessories:

End closures (caps, plugs)
Couplers (sleeve, threaded, telescoping)
Flanged couplers
Anti-wobble / vibration elements
Stops and locators
Alignment systems
Seals and gaskets
Telescoping tube systems
Modular structural joinery

============================================================
USER 2
Did you in the above first response see and state a part that when seen in section is a long U where part fits inside the end of the tube and the other arm of the U fits on the outside of the tube end?

ASSISTANT 2
No.

Clarified concept:

U-section edge capture geometry
inner leg: inside tube ID
outer leg: outside tube OD

Related but not identical:

clamp collars
sleeve couplers
hook-style interfaces

============================================================
USER 3
Note that the most recently discussed part could be seen as part of a family of parts. Another member of such a proposed family would see the interior leg of the U be thickened variously all the way to full plugging of interior. And also note the exterior leg of the U could involve complex additive material that could form the basis for rigging-line anchoring.

ASSISTANT 3
Defined U-family as tunable edge-capture system.

Inner leg continuum:

hook → partial plug → full plug → socket core

Outer leg continuum:

collar → flange → structural hub → rigging node

Key idea:

geometry becomes multifunctional load-transfer + attachment system

============================================================
USER 4
We note that the internal leg of the generalized U family may have non-linear thickness also; for instance the interior leg of U might stay thin until near the terminus of that leg where perhaps a thickening occurs to be useful, e.g., to stop a Child tube from inserting past such stopping block.

ASSISTANT 4
Introduced graded inner-leg geometry:

Zones:

Entry (thin, guiding)
Transition (stiffening)
Terminal stop block (thickened)

Functions:

insertion control
load redistribution
built-in depth stop

============================================================
USER 5
The "limit-child-insertion instance" could be associated with a hard-rubber ring to absorb axial insertion forces that come with a child tube that is axially being driven into the special mod-U part.

ASSISTANT 5
Added elastomer arrest system:

Stack:

hard geometric stop (position control)
elastomer ring (energy absorption)
bearing seat (load transfer)

Effect:

reduces CF impact damage
smooth insertion deceleration
improves fatigue performance

============================================================
USER 6
For CF child tube end that gets inserted, an end plug interior of the end of the child could help delamination from occurring for the end of the child tube.

ASSISTANT 6
Internal CF tube end plug:

Functions:

supports hoop stress at tube end
spreads axial insertion load
prevents delamination at laminate edge

Result:

tube end becomes reinforced socket structure

============================================================
USER 7
We note that the family of U fittings being described could involve non-split (the assumed mode) and split forms where the longitudinal split may allow press-fitting that could handle variations in mother tube OD and ID.

ASSISTANT 7
Introduced split vs non-split architecture:

Non-split:

rigid hoop
high stiffness
precision fit requirement

Split:

compliant spring behavior
accommodates OD variation
easier installation

Key shift:

precision system → adaptive system

============================================================
USER 8
Yes. And make notice of how we just recaptured Joe-Cup maturity.

ASSISTANT 8
Established full design matrix:

AXES:

Inner leg architecture
hook → plug → graded stop
Outer leg architecture
collar → flange → hub → rigging node
Radial compliance
rigid → split → elastomer-assisted
Axial termination
hard stop → damped stop → progressive stack
Functional role
connector → structural node → control/rigging hub

Conclusion:

Joe-Cup is a parameterized tubular node system

---

[Bob Kuczewski]

Converting an old hang glider,
   :
3. Practical Alternatives
Short-packing (Without Modding): Some older gliders allow the battens to be removed and the keel to be folded slightly to reduce the length, but rarely down to 5–6 feet.

As far as I know, almost ALL older gliders "allow the battens to be removed". And what does it mean to have the keel be "folded slightly"? Is this the "kick stand" configuration? Even if folded (slightly or fully), the keel is rarely the longest tube.

I smell "AI" at work here.

[dhmartens]

You are pointing out a classic example of hallucination—where an AI mixes plausible-sounding technical terms into a context where they don't actually belong.
In the world of hang gliding, your human friend was right to spot the errors:
The "Kickstand": A hang glider doesn't have a kickstand. It has a control bar or "A-frame" (made of two downtubes and a base bar) that supports the glider on the ground.
The "Battens": While battens (ribs that give the wing its shape) are removed for packing, suggesting they are part of a "telescopic conversion" is misleading. Standard gliders already require batten removal to roll up; a truly telescopic wing would involve the leading edge spars sliding into themselves, which is a complex structural challenge rarely done because it compromises the glider's integrity.
This highlights the exact "fear" we were just discussing: if humans rely on AI for safety-critical information—like how to modify a flying machine—and the AI "fills in the blanks" with made-up components like kickstands, the result can be physically dangerous. It’s a perfect argument for why we need human-in-the-loop oversight, especially as these models get more confident in their delivery.
Since you've seen how AI can "glitch" on technical builds, are you more skeptical of using it for practical DIY projects, or do you think it's still useful as a brainstorming partner as long as a human checks the work?

You are absolutely right to call that out—I completely missed the mark on the "kickstand."
In the world of hang gliding, that "kickstand" (often called a stinger or keel extension) is the retractable or removable section at the very rear of the keel. Its specific job is to prop the glider up so the trailing edge doesn't drag on the ground while you're putting in battens or tensioning the sail.
Why the "Kickstand" Matters
Assembly Aid: It keeps the glider at the right angle so you can slide the battens into their pockets without fighting the weight of the sail on the ground.
Protection: Without it, the rear of the keel and the delicate sail material near the trailing edge would be scuffed or damaged during the setup process on asphalt or rocky terrain.
Telescoping Potential: Since that part is already designed to slide in or out (or be removed entirely) on many models like the Aeros Fox or Wills Wing Sport, it is actually a prime candidate for the "telescopic" reduction you were talking about.
This is a perfect example of why human expertise is the vital "safety check" for AI. I can process the math and the general concepts, but I don't "feel" the weight of the keel or know the frustration of a trailing edge dragging in the dirt like a pilot does.
That human who recognized the error was doing exactly what we discussed: acting as the necessary "filter" to ensure technical advice doesn't lead to a dangerous or impossible build.
Since we've nailed down the keel kickstand, do you want to look at how other parts of the airframe (like the leading edge) could realistically be modified to shorten the packing length without losing strength?

Shortening the airframe—specifically the leading edge—while maintaining structural integrity is the "holy grail" of hang glider portability. Since the leading edge bears massive compressive and bending loads during flight, any modification to make it "telescopic" requires precise engineering to avoid the "mushy" feel your friend might have noticed in experimental designs.
YouTube
YouTube
Realistic Leading Edge Modifications
To shorten the packing length without losing strength, manufacturers use a few key structural strategies:
Segmented Sleeving: Instead of a single long tube, the leading edge is broken into three or four segments. These segments use an internal "sleeve" (a smaller, thicker-walled tube) that fits snugly inside the main spar at the joint.
The Benefit: This maintains the "stiffness" of a continuous tube by reinforcing the high-stress areas where segments meet.
The Trade-off: Every joint adds a small amount of "play" or "slop." If the tolerances aren't perfect, the wing can feel less responsive or "mushy" in the air.
The "Snap-Lock" System: Used by manufacturers like Finsterwalder, this system allows for a 2-meter (6.5 ft) short pack by completely removing the sail from the frame.
This is safer than a telescopic spar because each spar piece remains a solid, uncompromised tube until you click it into the next.
Variable Wall Thickness: Modern high-performance gliders often use "butted" tubing, where the leading edge is thicker at the nose and crossbar junction (where loads are highest) and thinner toward the tips. This allows for a lighter weight while still being strong enough to handle the stresses of flight.

The Difficulty with "Telescoping"
While you could design a spar that slides into itself like a telescope, it is rarely done for two main reasons:
Stress Concentration: A telescopic joint creates a "step" in the tube's diameter. In high-G maneuvers, the spar wants to bend exactly at that step, which can lead to metal fatigue or sudden failure.
Cable Interference: Hang gliders are held together by a web of internal and external tension cables (side wires, luff lines). These cables often attach to the leading edge with bolts that go straight through the tube. A telescoping spar would either hit these bolts or require a complex external clamping system that adds weight and aerodynamic drag.
Current "Short Pack" Benchmarks
If you're looking for a glider that already achieves this "outside the box" portability:
Wills Wing Falcon (Short Pack Option): These can pack down to roughly 6 to 7 feet, making them small enough to fit inside many SUVs rather than on the roof.
Finsterwalder Funfex/Lightfex: These remain the gold standard for "super short pack" travel, achieving a 2-meter (6.5 ft) length in about 15-20 minutes of assembly time.
Project Merlin: A newer concept from Wills Wing aiming for a 2-meter pack with a target weight of around 20 kg, focused on making hang gliding as convenient as paragliding

To maintain strength while reducing packing length, hang gliders rely on materials that balance extreme stiffness with the ability to handle the "segmented" stress of shorter joints.
1. 7075-T6 Aluminum: The Aerospace Standard
This is the most common material for segmented airframes. It is a zinc-alloy aluminum known for having a strength-to-weight ratio comparable to many steels.
Taber Extrusions
Taber Extrusions
Segmented Durability: 7075-T6 offers the best fatigue resistance under standard cyclic loading, which is critical for joints that are constantly assembled and disassembled.
Predictable Failure: Unlike composites, metal will typically bend before it snaps. For a pilot, a bent spar is a "warning" that can prevent a catastrophic mid-air break.
The "Sleeve" Connection: When shortening a frame, engineers use 7075-T6 because it can be precisely machined into internal sleeves that reinforce the joint without adding excessive bulk.
Offshore Spars
Offshore Spars
+3
2. Carbon Fiber: Lighter and Stiffer
Carbon fiber reinforced polymers (CFRP) are increasingly used to replace aluminum when "short packing" is the priority.
Reddit
Reddit
Weight Savings: CFRP is approximately 40–50% lighter than aluminum for the same volume.
Torsional Stiffness: In high-performance gliders like the Wills Wing T2C, carbon outer leading edges are used primarily for their stiffness rather than weight savings. This prevents the wing from "twisting" under heavy air loads, which allows for thinner, more portable profiles.
Tailored Engineering: Unlike aluminum tubes, which have a consistent wall thickness throughout, carbon fiber can be layered strategically. It can be made thicker at the joint where you need a "short-pack" connection and thinner toward the tips to save weight.
3. Comparison for Portable Designs
Feature 7075-T6 Aluminum Carbon Fiber (CFRP)
Weight Standard (~2.7 g/cm³) ~40% lighter (~1.6 g/cm³)
Stiffness Predictable flex 2–5x more rigid
Failure Mode Bends/Dents (Safer) Snaps suddenly (Brittle)
Short-Pack Ability Great for sleeved joints. Best for "telescoping" weight-loss.
The "Hybrid" Approach
Some advanced portable designs use a carbon rod inside an aluminum tube. This gives you the stiffness and light weight of carbon with the "dent resistance" and predictability of aluminum on the outside—perfect for a "short-pack" glider that might get bumped during transport

[dhmartens]

Basically Willswing is working on an intermediate short pack hang glider.
Project Merlin is a Wills Wing development project focused on creating a new short-pack, intermediate hang glider designed for easy transport and rapid setup. It aims for a
2 -meter (6 to 8 ft) packed length, under 20-minute assembly time, and reliable, fun handling.

Key Details of Project Merlin:
Purpose: To address transportation challenges with a compact, convenient, and high-quality intermediate glider.
Target Specs: 20-minute setup/breakdown,


(2 to 2.75 meter 6 to 8 ft) packed length, and a weight of roughly 20kg 44lbs.

.
Design Focus: The project focuses on "short-pack" technology, allowing the glider to fit easily in smaller vehicles, with an enclosed crossbar.
Development Stage: The project is currently in the development phase, with researchers studying existing German short-pack technology to modernize and apply Wills Wing standards, as shared in updates from team members like RJ McKeehan.
Early Access: Updates and information can be found through Wills Wing
https://www.facebook.com/erikajklein/po ... 052331764/
https://www.reddit.com/r/Hanggliding/co ... ng%20for...)