I found a lost production model telescopic hang glider called the Delta Wing Phoenix VI B Jr. designed by Bill Bennett
https://airandspace.si.edu/collection-m ... 715000cp02https://www.delta-club-82.com/bible/man ... _id238.pdfCore Dimensions & Layout (Standard 18ft Rogallo)
A typical 1970s "Standard" Rogallo used a 90-degree nose angle and three primary tubes:
Smithsonian Institution
Smithsonian Institution
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Keel Tube: 18' long, typically 1.75" x .058" 6061-T6.
Leading Edges (x2): 18' long, often using a 2" x .049" outer tube with a 1.75" x .049" telescopic inner section.
Crossbar: 18' long, typically 1.75" x .049" reinforced with an internal sleeve (e.g., 1.625" x .035") to prevent buckling at the center hinge.
Telescopic Sleeving Blueprint (Phoenix VI Style)
The Phoenix VI, a high-performance 1974 design, utilized a specific telescopic sleeving method for the leading edges:
National Air and Space Museum
National Air and Space Museum
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Inner Section: A 1.5" x .049" (6063 T832) tube runs from the nose plate to approximately 18" past the crossbar junction.
Outer Sleeve: A 1.625" x .058" tube slides over the inner section, creating a reinforced double-wall "sleeve" at the highest stress point (the crossbar junction).
Positive Lock: These were secured with 1/4" aircraft-grade bolts and stainless steel tangs rather than simple friction locks.
DELTA CLUB 82
DELTA CLUB 82
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While a single animated illustration of the Phoenix VI telescoping mechanism is difficult to find in a single image, the assembly is defined by a specific "sleeve-over-sleeve" design centered around the crossbar junction.
Phoenix VI-B Leading Edge "Telescoping" Blueprint
The Phoenix VI (specifically the VI-B) achieved its strength and portability through a multi-diameter nesting system. Instead of a simple "radio antenna" slide, it used two primary structural sections that met and overlapped at the highest stress point.
DELTA CLUB 82
DELTA CLUB 82
The Inboard Section (Nose to Crossbar):
Material: 1-1/2" x .049" 6063-T832 aluminum.
Length: Extends from the nose plate to exactly 17-3/4" past the crossbar.
The Outboard Section (Crossbar to Tip):
Material: 1-5/8" x .058" 6063-T832 aluminum.
Action: This larger tube slides over the 1-1/2" inboard tube.
The Sleeve: It slides toward the nose, ending 12-1/4" past the crossbar (toward the nose).
The Structural Overlap:
This creates a 30-inch double-walled "super-sleeve" centered right where the crossbar attaches. This is critical because the crossbar junction is where the wing experiences the most bending force.
Internal Reinforcement: Inside this junction, there is an additional "internal sleeve combination" that nests inside the 1-1/2" tube for even more rigidity.
DELTA CLUB 82
DELTA CLUB 82
Visualizing the Telescoping Action
To Extend (Fly): You slide the 1-5/8" (outer) tube away from the nose until it hits a "stop" or aligns with a bolt hole.
To Retract (Pack): You remove the safety bolt at the tip or junction and slide the 1-5/8" tube back toward the nose, effectively "swallowing" the thinner inboard tube to shorten the overall length for transport.
Locking: Unlike modern "twist-locks," the Phoenix used positive-lock aircraft bolts through the overlapped sections to ensure the tubes could not slide during flight.
Why You See "Deflexor Cables"
In most photos of the Phoenix VI, you will see thin wires running along the leading edges. These deflexor cables are there because even with aircraft-grade aluminum, an 18-foot tube is prone to bowing. These cables act like a "bowstring" to keep the telescoping tubes straight and provide the specific wing curve (washout) needed for stability.
National Air and Space Museum
National Air and Space Museum
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Me: it may be fixed and it doesn't telesope, im still not sure it telescopes
The Phoenix VI-B leading edges do indeed telescope, but they are not "one-touch" telescopic like a camera tripod. They use a manual sleeve-and-lock system designed for structural safety during flight.
How the Telescoping Works
The leading edge is split into two distinct sections of 6063 T832 aluminum tubing that slide together to create a reinforced joint:
The Inboard Tube (Nose Section): This is a 1.5" x .049" tube that stays attached to the nose plate.
The Outboard Tube (Tip Section): This is a larger 1.58" x .058" tube. It slides over the inboard tube, acting as an external sleeve.
The "Telescope" Action: To break the glider down for transport (reducing the 18.5-foot length to approximately 9–10 feet), you remove a positive-lock aircraft bolt at the junction and slide the outboard tube inward toward the nose.
Why It Doesn't "Look" Telescopic
If you are looking at a fully assembled Phoenix VI, it appears "fixed" because:
Safety Bolts: Once extended, the tubes are held by 1/4" aircraft bolts. Unlike a friction-lock pole, it cannot move while these are in place.
The Sail Tension: The Dacron sail is under high tension and held by end-caps, which physically prevents the tubes from sliding inward even if the bolts were missing.
Deflexor Cables: The deflexor wires you see in photos provide external bracing to keep these multi-part tubes from bowing under the hundreds of pounds of lift generated during flight.
Historical Context
In the 1970s, this was referred to as a "breakdown leading edge." Bill Bennett’s Delta Wing Kites designed them this way specifically so pilots could transport an 18-foot wing on a standard car roof rack
by JoeF » Thu Mar 19, 2026 1:16 pm 
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