Design & Prototype an Ultra-Portable Hang Glider Dissertation.pdf · 2019. 5. 20. · Design & Prototype an Ultra-Portable Hang Glider Final Report p3/50 Jeremy Soper ’18/05/19

Design & Prototype an Ultra-Portable Hang Glider Final Report

p1/50 Jeremy Soper ’18/05/19

Design & Prototype an Ultra-Portable Hang Glider

fc286b Final Report

JEREMY SOPER ~ js2114 ~ Jesus College

This project is dedicated to my late grandfather, who would have liked to see it take flight.

Contents

1. Nomenclature 2

2. Introduction 3

2.1. Motivation 3

2.2. Specification 4

2.3. Plan of attack 4

3. Analytical flight model 6

3.1. Glide polar 6

3.2. Measurement 10

3.3. Flowfield 10

4. Design 12

4.1. Key features 13

4.2. Material selection 19

4.3. Physical modelling 20

4.4. Structure 21

4.5. Aerodynamics 22

5. Build 23

5.1. Funding 23

5.2. Procurement 24

5.3. Progress 25

6. Testing 30

7. Conclusions 33

7.1. Outstanding work 34

7.2. Changes for Mk. 3 35

7.3. Applications 36

7.4. Future prospects 37

8. Acknowledgments 37

9. Appendices 38

9.1. Numerical values 38

9.2. Structural sanity check 39

9.3. Aerodynamic influence of sail double surface proportion 42

9.4. Bill of materials 43

9.5. Snout fabrication drawing 46

9.6. Sail modification drawing 47

9.7. Retrospective safety assessment 48

9.8. Martian flight 49



1. Nomenclature

Table 1: Abbreviations

Abbreviation Definition

BB basebar

BHPA British Hang Gliding and Paragliding Association

CUE{D\S} Cambridge University Engineering Department\Society

DS double surface

GP glide polar

GR glide ratio

HF hands-free equilibrium (𝐶𝑀 = 0)

HG hang glider

HP hang point

KP kingpost

LE leading edge

LLT lifting line theory

MG maximum glide (ratio)

MS minimum sink (rate)

PG paraglider

QR quick release

TE trailing edge

TO takeoff

UR upright

US (Wills Wing) Ultrasport

VG variable geometry

XT crosstube

Fig. 1: Aeros Target 16, typical single surface hang glider

LE

KP

Lufflines

Top side wires

BB

UR

HP

Keel

XT

Battens

Washout

rod

Nose cone Top front wire

Top aft wire

Bottom aft wires

Bottom

front

wires

Bottom side wires

Keel pocket

Stinger



2. Introduction

Hang gliding is the closest man can get to flying like a bird. Lying prone and steering by weightshift,

soaring high above the landscape or skimming low over dunes and beachfront hotels, hang glider

pilots are afforded a truly bird’s eye view of the world. In the air, the 10 m span wing feels like a

natural extension of your body; so intuitive is the handling. On the ground, however, its ungainly

bulk makes for difficult transportation and storage.

Fig. 2: Glider carrying payload Fig. 3: Payload carrying glider

2.1. Motivation

Since the advent of hang gliding in the 1960s, wing design has been almost exclusively performance-

driven, seeing an improvement in maximum glide ratio (MG) from 2 to 20. World distance and

speed records are broken annually, and pilot life expectancy continues to rise. Despite this, the

sport’s popularity is waning; the principal reasons including the cultural lethargy of my computer-

bound generation (a rant for another day), and the rise of the paraglider (PG).

When asked in a confidential setting, most paraglider pilots admit that their seedlike

bobbing on the air currents cannot match the birdlike sensation of flying a hang glider (HG), but

the prospect of lugging 35 kg of 5 m long aluminium tubes up a mountain to takeoff (TO), compared

to 15 kg of plastic bag, is critically offputting. Chasing lower drag coefficients has made HG wings

stiffer and more aerodynamically efficient but heavier and fiddlier to rig. Having had an absolute

ball flying a less than high-performance training wing (Fig. 1, MG = 6), staying aloft for up to

5.5 hours over 80 km on nothing but rising air, I believe there is a market for a convenience-driven

wing, which, for a small sacrifice in performance, is light and compact enough to carry to launch

and fit inside a regular car. This would enable: access to more TO sites, self-retrieve after a cross-

country flight, and even “hike & fly”, which is immensely popular with PGs.

Thermalling wingtip to wingtip with griffon vultures above snow-capped peaks and azure

lakes has imbued me with a reverence for the natural world and the conviction to preserve it.

10 m

5 m



Aviation has changed my life for the better, and I hope that by making the equipment less

cumbersome, it could reach out to even more people. This project therefore seeks to design an

“ultra-portable” HG fulfilling the following specification, then build it to test the viability of the

design.

2.2. Specification

Design and build a hang glider:

1. weighing < 30 kg,

2. which when derigged occupies an envelope not exceeding 2 x 0.5 x 0.5 m – light and small

enough that it can feasibly be carried 5 km by the pilot alone and fit inside a Toyota Yaris.

3. Minimum sink rate (MS) < 1.5 m.s-1 and

4. MG > 7, the two of which together constitute what is henceforth referred to as “performance”.

5. Handling should be sufficiently benign that an average (mass, height, skill) HG pilot such as

myself can control it without undue physical or mental effort. Ideally, it would comply with

the British Hang gliding and Paragliding Association’s (BHPA) stipulations on positive pitch

and neutral spiral stabilities. Hands-free equilibrium (HF) should coincide with MS, so that

pushing the basebar (BB) out (and risking stall) is not required in wings level flight.

6. The glider must be able to withstand “[−2, 4]𝑔 loading”, i.e. up to 400% equilibrium flight

loading in upthrust and 200% in downthrust, without irreversible deformation and [−3, 6]𝑔

without catastrophic failure.

7. De\rigging should take < 20 minutes for one person.

Primary considerations are therefore compactness, mass, handling, safety, ease and speed of

de\rigging, performance, as well as ease, cost and speed of manufacture.

2.3. Plan of attack

1. Identify product niche.

2. Fix specification.

3. Create an analytical flight model for a HG, incorporating all the relevant geometric,

aerodynamic and material variables.

4. Collect flight data on my own glider, a Wills Wing Ultrasport 147, with which to calibrate the

model by adjusting the unconstrained parameters until it best fits the data.

5. Trial and compare candidate designs for the “Sopalite” using the model.

6. Flesh out and advance the most promising design with structural and aerodynamic analyses.

7. Build prototype.

8. Test (incomplete, see Fig. 4).



Fig. 4: Project progress as of ’18/05/26

2.4. Prior art

Fig. 5: Equipment mass vs. MG1,2

{H\L}P = high\low performance

Fig. 5 shows that in relation to other modes of free flight, the “Sopalite” aims to nestle between

PGs and HGs in terms of mass, and around intermediate HG performance. There is a distinct

positive correlation between equipment mass and MG. Only foot-launched sailplanes buck this

trend significantly, offering MG = 27 for as little as 48 kg (Aériane Swift Light2), though they still

require a trailer to transport due to the sizeable fairing.

Short-packing HGs do exist, for instance the Finsterwalders3 and Aeros Target4 can be

broken down to 2 m, although this fiddly process is far from convenient on a cold, windy hillside.

The author attests to many hours spent crawling under and reaching into his Target sail to undo

split rings, depress spring buttons whilst simultaneously twisting and feeding slippery aluminium

tube through two layers of slippery Dacron sailcloth, and retrieve dropped split rings. Once

separated, the vast collection of components is easily muddled or misplaced. Cables are prone to

incorrect rerouting when rigging, and pins are inexorably attracted to long grass. Scope for pilot

error increases with the complexity of the rigging process, both during setup and also once the pilot

is (eventually) ready for TO. Having spent a considerable length of time assembling an aircraft

from its constituent parts, they are more likely to attempt a flight even if meteorological conditions

are marginal. Hence a quicker rigging glider (specification point 7) discourages rash decision-making

and promotes safer flying.

Analyse Model Build Test Design



3. Analytical flight model

I opted to use Jupyter Notebooks as a form of computable document in which to construct the top

level flight model. The intention was for it to perform the necessary calculations and be readable

in a way that a Matlab script would not. It proved versatile yet frustrating. The embedded

visualisations are effective as hoped but the notebook regularly freezes and crashes, and slows as it

grows.

3.1. Glide polar

Table 2: Main parameters of the top level flight model

Symbol Definition US value Unit

𝛿 deviation from elliptical lift distribution 0.55 A

R aspect ratio 7.16

𝐶𝐷𝑝 parasitic drag coefficient 0.0461

𝑆 wing planform area 13.84 m2 W

L wing loading 77.97 Pa

Five main parameters were identified (see Table 2), and the variation in glide polar (GP) with each

was plotted, in order to gain an appreciation of performance sensitivity to different factors. At this

stage, 𝛿 was assumed constant for simplicity, the value set by the flight data (see §3.2) collected

on the Ultrasport (US). WL is constant because the GPs are for equilibrium flight. Drag is composed

of parasitic and induced contributions; the latter can be expressed in terms of the lift coefficient

𝐶𝐿, along with AR and 𝛿, both dependent on wing geometry. Parasitic drag is further split into form

(pressure) and skin friction components, the former a function of geometry and the latter with a

speed dependence though approximated as a constant 0.009 . This is justifiable because 𝐶𝐷𝑠

typically comprises only ~18% of 𝐶𝐷𝑝, so complexity is reduced considerably for a minimal loss of

accuracy (a recurring theme).

Lift 𝐿, drag 𝐷 and weight 𝑊 balance in steady glide at glide angle 𝛾 and airspeed 𝑣:

The above presents two distinct relationships between 𝐶𝐿 and 𝐶𝐷, which are solved as simultaneous

equations to give an implicitly defined GP curve:



where �̇� and �̇� are horizontal and vertical velocities relative to the air (+ve forwards and upwards)

and 𝜌 is air density.

Fig. 6a displays the full locus of theoretical vertical and horizontal velocity combinations

at which the forces are balanced. Angle of incidence 𝛼 increases in the anticlockwise direction. In

reality, stall onset (s) occurs just beyond MS (local maximum), as shown in close-up Fig. 6b, and

the lower half of the GP is not usually frequented. The same horizontal velocity can be achieved

at a smaller sink rate on the upper half, which is preferable unless diving to avoid a hazard. A

steep dive results in a strong restorative pitching moment, strenuous to maintain, while at the LHS

of the lower half, the pilot subtends a very acute angle to the keel, rendering the glider

uncontrollable (tuck). Therefore, a tight spiral is favoured for reaching the ground quickly. MG is

found graphically as the non-zero point whose tangent passes through the origin. �̇�𝑀𝐺 > �̇�𝑀𝑆 ≥ �̇�𝑠 .

Fig. 6a: GP, full range Fig. 6b: GP, usual flight envelope

Performance is sensitive to the parasitic drag coefficient (Fig. 7). Reducing 𝐶𝐷𝑝 from

0.046 to 0.03 improves MG from 8.87 to 11.00 and increases �̇� at which it occurs from 12.88 to

14.38 m.s-1, though derating MS slightly from -1.27 to -1.29 m.s-1. Sources of form drag are detailed

in Table 5. Besides the leading edges (LE), the largest contributor is the payload, highlighting the

importance of a streamlined harness and helmet and tidy flying technique i.e. flow-aligned posture.

Rigging wires form a substantial fraction due to their length, suggesting that plastic coating should

only be considered if committed to the longevity of the wires, particularly for frequenters of coastal

sites where saltwater hastens the corrosion. Aerofoil section as opposed to cylindrical uprights (UR)

are worthwhile due to the 90% reduction in 2D drag coefficient 𝑐𝑑; less so for the shorter BB. The

obsession amongst pilots with removing wheels is unfounded – a pair of 6” pneumatic wheels only

add around 3% form drag but can easily save the pilot’s life and their glider in the event of a crash

landing and drastically reduce the frequency with which the control frame must be repaired due to

heavy landings.

�̇� / m.s-1

𝑦 /

m.s

-1

s stall

MS MG

𝑦 /

m.s

-1

�̇� / m.s-1

𝛼



Fig. 7: GP vs. 𝐶𝐷𝑝

Counterintuitively, MG is constant w.r.t. WL =

𝑊

𝑆, though MS worsens and occurs at a

higher speed for higher WL i.e. the GP simply scales linearly, maintaining its proportionality

(Fig. 8). This means that a heavier but no more voluminous pilot can glide the same distance as a

lighter pilot on the same wing, and would do so faster (until the greater loading flexes the compliant

wing into a less efficient shape). Hence competition pilots often carry lead weights as ballast to

increase their speed at MG. Although a lighter pilot with better MS could outclimb them in the

same thermal, the heavier pilot can potentially reach it sooner to gain the racing advantage.

Fig. 8: GP vs. WL

𝛿 decreases with 𝛼 i.e. increases in the clockwise direction around the GP because at lower

angles of incidence (corresponding to higher speeds), spanwise lift diverges further from an elliptical

distribution as the washed out wingtips become unloaded and eventually negatively loaded. This

is confirmed by Fig. 9, showing 𝛿𝑀𝑆 = 0.4 and 𝛿𝑀𝐺 = 0.59. Approximating constant 𝛿 = 0.55

throughout the usual flight envelope centres the 2 data points for MS and MG in Fig. 10 on

AR = 7.16 with acceptably little deviation.

𝐶𝐷𝑝

�̇� / m.s-1

�̇� / m.s-1

�̇� / m.s-1

𝑦 /

m.s

-1 W

L / N.m

-2



Fig. 9: GP vs. 𝛿

Increasing AR with constant 𝑆 increases the wingspan, distancing the tip vortices from the

wing root thus reducing downwash on the main lift-producing areas, decreasing induced drag and

improving performance (until the increased form drag due to the greater wingspan begins to

dominate). The main compromise is stiffer handling, since there is more wing further from the root,

increasing the moments of inertia about the roll and yaw axes, requiring more input to initiate and

halt a turn. Structural considerations also limit the feasible AR; the bending moments at the root

increasing with AR for the same WL. In terms of a HG, this increases the loads in the side wires and

makes a LE tube of the same diameter more slender so more prone to buckling. Greater forces

necessitate a stronger structure, which incurs a greater mass penalty. Increasing AR from 4 to 8:

improves MS from -1.36 to -1.27 m.s-1,

decreases �̇�𝑀𝑆 from 11.86 to 9.27 m.s-1, correspondingly lowering the stall speed thus improving

TO and landing characteristics,

improves MG from 7.38 to 9.15,

decreases �̇�𝑀𝐺 from 15.66 to 12.38 m.s-1.

Fig. 10: GP vs. AR

�̇� / m.s-1

𝑦 /

m.s

-1

𝑦 /

m.s

-1

�̇� / m.s-1

𝛿

AR



3.2. Measurement

Collecting data on the fly is tricky. Even with an anemometer (which I do not have), �̇� and �̇�

cannot be extracted from 𝑣. In order to estimate MS and MG, I performed 13 straight line, wings

level flights between points of known horizontal and vertical separation in stable (non-thermic)

evening conditions, subtracting the forecast wind velocity from my mean ground tracking velocity.

Maintaining MS is awkward due to its proximity to stall rendering steering inputs less effective,

whilst attaining MG without a flight computer loaded with the GP relies on pilot judgment.

A further test of the flight model was to generate a 2D flowfield around a simplified hill

shape in which to “place” the parameterised glider, comparing its trajectories and equilibrium

positions to those experienced whilst ridge soaring and measured with an altimeter. The Long

Mynd, Shropshire, was chosen as the test ridge due to its especially uniform profile and prismatic

shape, which combined with the unimpeded plain upwind gives a consistent laminar flow.

3.3. Flowfield

Windspeed gradient near the ground varies with the meteorological conditions and surface texture.

Unless scratching low on a light wind day or deliberately ground skimming, however, HGs usually

ridge soar clear of the boundary layer, so the flow may be considered inviscid.

Potential flow around a cylinder is given by a doublet imposed on a uniform flow (Fig. 11).

This was conformally mapped onto a Joukowski aerofoil reflected left to right (Fig. 12), the upper

half upstream part of which approximates the profile of the soarable slope of the Long Mynd. The

result is the flow velocity field of Fig. 13. Flying at MS in a 14 mph breeze, the US is found to

equilibrate (purple triangle) 46 m above and 72 m in front of the apex of the hill, corroborated to

within 11% by the onboard altimeter. Fellow pilot Keith, flying an Airborne Fun 190 with 30%

lower wing loading, was notably (smugly) hovering around 50 m above and slightly in front of me

on the US, despite his estimated 25% higher drag. This too is upheld by the model (cyan triangle).

Fig. 11: Flow velocity field around 2D cylinder Fig. 12: Joukowski R-L aerofoil as 2D hill

𝑥 / m

𝑥 / m

𝑦 /

m

𝑦 /

m



Fig. 13: Flow velocity field over 2D smooth ridge, 14 mph wind

Summing the flow velocity field and the glider’s velocity vector leads to the trajectory fields

of Fig. 14, mapping the flight paths available if a constant pitch is maintained with wings level.

Later the same day, the windspeed increased to 20 mph and Keith found himself pinned back in

the enlarged region of no return, characterised by the arrows terminating on the hill, with the result

that he top landed just downwind of the hill apex as predicted (much to his chagrin).

Fig. 14: Trajectory fields over 2D smooth ridge for US in 14 mph wind

∝

∝

𝑥 / m

𝑦 /

m

𝑥,𝑦

/ m.s

-1

𝑥 / m



4. Design

Starting from the base design of the US, each component was interrogated according to the

following philosophy: remove if superfluous. If essential, could its mass or volume be reduced?

What effect does that have on the other components?

Given that my particular 2001 US was originally made for the then women’s world

champion, for whom performance was of paramount importance, its design represents the pinnacle

of evolution in HG design at the start of the millennium. Far from a radical new prototype, it is

the mature product of 4 decades’ incremental development by one of the largest and oldest

manufacturers in the world.5 Every component has therefore already been substantially optimised

for performance, and changing anything even slightly inevitably leads to losses, as well as a

cascading knock-on effect throughout the entire design due to its interlinked nature.

On the other hand, an upshot of basing the Sopalite on the US is that a certain level of

performance is assured, as long as the detrimental consequences of alterations can be mitigated.

Another is that in the event of supply chain failure, some components may be scavenged from the

US. Incidentally, this saved the project (see §5.2).

Each macroscopic design action was accompanied by the double feedback loop illustrated

in Fig. 15. The aims dictate the necessary features, arrangement and subsequently external loading,

which produces a pressure distribution over the wing via the aerodynamic analysis of XFLR5. This

is fed into Abaqus to compute the internal structural forces, whose associated stresses may exceed

the material capability, calling for either a different arrangement or strengthening, which usually

entails more mass. Concurrently, the internal stresses produce strains, leading to significant

deflections in the highly compliant wing due to its slender tubing and flexible sail, thus modifying

the flowfield. A coupled flow structure interaction (FSI) study may be possible exclusively within

Abaqus, but reconnaissance in that direction suggested it would have taken too long for this project.

Fortunately, the iterative combination of Abaqus and XFLR5 was found to converge to a steady

wing shape for a given loading satisfactorily quickly.

Fig. 15: Computation flow

p pressure

distribution

W loading

σ structural

stresses

δ deflections

Features F structural

forces

Aim

s

Abaq

us

XFLR

5



4.1. Key features

Prose cannot capture the web of reasoning that justifies every aspect of the design, so only the

main features are described here.

Bowsprit: the most immediately striking part, for those who are at least vaguely familiar

with modern hang gliders, is the 1 m long extension of the keel ahead of the wing. Restraining the

LEs with tensioning cables running to the bowsprit facilitates the elimination of the crosstubes

(XT), the principal compression members and one of the heaviest components. Typically around

3.5 m in length each, XTs also pose an obstacle to short-packing, especially when hidden inside the

wing thus awkward to disconnect, as on a double surface (DS) glider. Dispensing with them was

therefore a top priority, the compromise being higher compression in the LEs.

Fig. 16: RH frame and rigging in flight

Further benefits include twofold enhanced crash protection. Firstly, when nosing in, the

angle subtended to the ground by the keel is reduced by the bowsprit, decreasing the likelihood of

the pilot impacting their head on the keel when their momentum swings them through the control

frame. Resulting spinal injury is the main cause of incapacitation amongst HG pilots. Secondly, in

the event of a tree landing, more cables abound to snag on branches, preventing the glider from

plummeting to the ground to the detriment of the pilot.

Sail tension is initially applied by pulling back (to open out) the LEs in lieu of the XTs,

which usually perform this function. The LE junction (“snout”, Fig. 17) is free to slide longitudinally

but constrained in roll by electing a square section keel. Additional tension may be tailored in flight

by means of a “variable geometry” (VG) 8:1 pulley system, as per most modern intermediate and

high performance gliders. Higher tension flattens the washout, improving wing efficiency hence GR

but increasing roll stiffness, making it harder to turn. Webbing is used to hold tension as opposed

Nose wire (WN) 1

WN3

WN2

“Ablative heat

shield” at nose

Snout

LE3

LE2

LE1

Bowsprit

Keel

midsection

Stinger

Tension

𝑇𝑊𝑇



to cables because it is flexible enough to loop back (through 2 bow shackles as pulleys), providing

2:1 mechanical advantage. Its greater elasticity also makes it less susceptible to shock loading

damage caused by the VG cord being released in an uncontrolled fashion, as can sometimes happen

on landing approach when the pilot is struggling to multitask.

Fig. 17: Snout in flight

Bowsprit HGs have been marketed previously, notably the Batuek Astir6 and Wasp

Gryhpon7, however their short-packing speeds are still unacceptably slow due to the need to remove

the LEs and battens from the sail to roll the sail up, which is why the Sopalite implements…

Telescopic LEs: quite an obvious feature considering the 5 m long encumbrance of

conventional LEs forces many HG pilots to drive around with an illegal vehicular overhang.

Unsurprisingly (otherwise they would be commonplace), their implementation was tricky. Most

so-called telescopic models only partially enclose the LEs, meaning each tube must be extracted

separately for stowing, occupying just as much volume if not length as a standard model. Full

length telescoping precludes the use of bolts in holding the LE together, since their necessary

removal\insertion during de\rigging would be too time-consuming, so an alternative means of

connection had to be devised, in such a way as to transmit substantial compression and bending

moments.

Fig. 18: LE coupler concept Fig. 19: LE cable lug concept



Fig. 20: LE2-3 junction, showing QR pin passing through tang, sleeve, LE2, LE3 and bung

Numerous couplers that twist to un\lock in non-round section tube were proposed

(e.g. Fig. 18) then dismissed, as were their accompanying lugs welded to the outside as cable

attachments (Fig. 19). Eventually, chunky 10 mm diameter quick release (QR) ball lock pins were

settled on with more generally available round section tube, passing through welded outer sleeves

and inner bungs to increase contact area and dissipate stress concentration, with custom tangs for

the cables (Fig. 20). A snug fit and 90 mm overlap helps to address the bending. Three LE sections

were needed to bring the stowed length down to 2 m. More sections suffer over-compliancy and

unavailability of snug consecutive telescopic tube sizes (see §5.2). Hole positions were contrived to

align in both de\rigged configurations where possible so that the QR pins may be used to secure

the tubes in both states with minimal loss of strength. The ability to stow the LEs within the sail

opens up the option for a…

Concertina sail: rather than rolling, which necessitates the tedious removal of 26/28 battens,

folding the sail alternately up and down as it slides along the LE like a curtain rail permits the

battens to stay in place, provided they are positioned along the folds. This results in battens

perpendicular to the LEs, instead of the usual chordwise arrangement (parallel to keel). To my

knowledge, battens spanning radially from the nose have been tried before, but never anything akin

to the Sopalite. Far from presenting an impediment to the flow, this arrangement is actually better

aligned in certain conditions when the spanwise component becomes significant e.g. slow flight near

MS. HGs (with an aspect ratio of around 6) are very much in the domain of finite span wings,

where the low pressure on the top surface sucks air around the wingtip from the bottom, drifting

towards the root as it progresses along the chord. This crossflow is augmented by the severe twist

distribution, which imposes a spanwise pressure gradient from tip (high) to root (low).

Confirming my suspicions, Apco Aviation have since unveiled a new paraglider featuring

flow aligned ribs, clearly the first of its kind as they are awaiting a patent.8 The overall effect on



the Sopalite is realistically minimal if the sail is tight because the battens protrude mainly inside

the aerofoil, which is probably why HGs have stuck to convention in this department.

Fig. 21: Plan view of RH sail in flight Fig. 22: Isometric view of RH sail stowed

The curved LE shape and DS are not conducive to neat, repeatable folding, so the bottom

surface was made semi-detachable by a zip running the full semi-span. When stowing, it is unfurled

up around and placed on top of and in plane with the top surface, folding about the max. camber

line (aft of which the unloaded sail is essentially planar). The curved sections of the battens are

secured to the LE in flight by Velcro strips. Repeated folding will likely crease the sail, but these

creases will be largely unproblematically flowwise. The Mylar LE inserts will suffer slightly, but

removing\inserting them each flight would be too much hassle, and flowwise creases will not

prevent them from performing its role of holding curvature about an orthogonal axis.

Once the sail is compressed, the front ends of the battens gather along the elongated snout

plate, 490 mm wide as compared to the usual 150 mm.

Telescopic keel: the addition of the bowsprit requires the keel to be broken down into 3

sections to fit in the 2 m envelope. For the same reason of convenience as the LEs, telescoping is

preferable to hinging or separation. Shortening the keel by truncating the stinger (aftmost section)

near the trailing edge (TE) was considered but dismissed because the glider would then have to be

rigged either flat – prone to damaging or dirtying the sail; or nose down – treacherous in wind as

the sweepback places a lot of surface high off the ground, inviting ground-looping.

Fig. 23: Stowed frame



As for the LEs, no bolts can be used except at the extremities, invoking more QR pins.

The kingpost (KP) and URs, not coinciding with the end of a section, were mounted on a slider so

that they can be retracted for stowing, both hinging forwards onto the keel (URs usually hinge

aftwards). Not welding the KP and URs onto the keel allows them to be adjusted if necessary.

Noticeable in profile is the unorthodox aft rake of the KP, principally to bring the luffline

hook closer to the ground when sat on the stinger (resolving a common problem for vertically-

challenged pilots), with the added benefits of lifting the TE more vertically (neater reflex) and

presenting less frontal KP area (reduced parasitic drag) without weakening the top rigging. The

last clause is conditional on positioning the KP base in line with the connections of the top side

wires to the LEs, ensuring the net force line remains within the KP. To achieve this, the KP was

moved aft 150 mm, requiring a separate component to provide a hang point (HP) sufficiently far

ahead of the top of the URs to avoid chafing the hang strap. A hang channel offering 9 positions

over a 99 mm range gives ample options for trimming pitch (see §4.5).

Fig. 24: KP, UR, HP keel slider in flight

Control frame: (triangle comprising the URs and BB), one of the only elements to escape

substantial modification. Its dimensions are intrinsic to the intuitively benign handling of modern

gliders. Shortening the URs would diminish roll authority, demanding more effort to attain the

same roll rate (since a shorter pendulum has a higher ratio of vertical/horizontal displacement). It

would also prohibit the glider from being able to rest on the ground once the pilot is clipped in

when preparing to TO and after landing, burdening the pilot with the weight and downthrust.

Parasitic drag reduction is minimal, even if the URs could be removed entirely:

𝐷𝑝 ≈ 𝐷𝑓 =1

2𝜌𝑣2𝐴𝐶𝐷𝑓

=1

21.2 (50

1609

3600)

2(2 ∗ 1.7 ∗ 0.025)0.12 = 3.06 N for standard aerofoil

section URs on 50 mph glide, corresponding to

ℎ =𝐸𝑝𝑔

𝑚𝑔≡

𝐷𝑓𝑥

𝑚𝑔=

3.06∗1k

111∗9.81= 2.81 m equivalent altitude loss per km, which is hardly a competition-

winning margin.

Placing the pilot right up against the wing would see an additional parasitic drag reduction

by shrinking the pilot’s wake and wetted area, but this benefit is negated by the loss of visibility

(unless the sail can be made fully transparent) and the need for manually-operated controls in the



absence of a pendular pilot. Weightshift control is something that HG pilots, the most puritanical

of aviators, are unwilling to relinquish.

Longer URs oblige the pilot to raise the glider above their shoulders to lift the BB off the

ground for TO, forfeiting valuable pitch authority. As for the KP, the top of the URs was positioned

to align with the connections of the bottom side wires to the LEs. This puts a slight couple (𝑊ΔURHP𝑥)

in the keel tube during positive loading but nothing untenable. I elected to rake the URs forward

3° as compared to 10° on the US, sending the BB 260 mm aft as a matter of preference (it was

previously unnervingly close to my face at HF).

Rigging: 53 m of galvanised steel cable (vs. 38 m on the US). The extra length is mainly

due to the nose wires, directly upstream of the LE so incurring minimal drag penalty. The two

potential connection points for the side wires are at 1/3 and 2/3 span, via custom tangs secured by

the QR pins. Aligning the top side wires with the KP is only feasible at 2/3, likewise for keeping

the bottom side wires perpendicular to the URs to avoid unduly compressing them, otherwise the

slightest normal load can prompt buckling. Although the URs are intended to be sacrificial to an

extent, breaking in preference to the pilot’s arms in the event of a heavy landing, it is not convenient

to have to replace them too frequently.

Fig. 25: Frame, partial rigging and sail LHS in flight mode

Given that the snout slides, the front wires bolt to the “ablative heat shield” at the nose.

As per usual, the bottom front wires can be released quickly for flat de\rigging in strong winds,

though accessing the spanwise zip is trickier in this configuration. The aft wires are bolted as far

aft as possible to facilitate keel telescoping without snagging in grass. Front and aft wires primarily

transmit pitch inputs and as such are vital but not heavily loaded, so standard duty (SD) 2.5 mm

7 x 7 strand wire is sufficient, with PVC coating to protect against weathering. The nose and

bottom side wires, on the other hand, are almost constantly strained, calling for heavy duty (HD)

3.2 mm 7 x 19 strand wire. These are uncoated to enable daily inspection and because they should

be replaced biennially anyway.

The lufflines support the TE, adding reflex when diving to augment positive pitch stability.

Their 1.5 mm diameter reflects their lower loading.



4.2. Material selection

Deflection of the 5 m long LEs on the US is 80 mm at midspan when the sail is tensioned but

unloaded. This forwards bowing biases the buckling mode of the slender column, which the sail

acts to restrain. The main priority for the LEs is then to achieve sufficient bending strength whilst

minimising mass, examined in the following analysis.

Axial stress condition: 𝜎 =𝑀𝑦

𝐼≤

𝑀𝑅𝜋

4(𝑅4−𝑟4)

≃𝑀𝑅

𝜋

44𝑅3𝑡

=𝑀

𝜋𝑅2𝑡< 𝜎𝑦 ,

where thickness 𝑡 ≪ 𝑅 outer radius for thin-walled tube.

Mass per unit length to be minimised: 𝑚 = 𝜌𝜋(𝑅2 − 𝑟2) ≃ 𝜌𝜋2𝑅𝑡 ∝ 𝜌𝑅𝑡 ,

therefore minimise objection function 𝑓 = 𝜌𝑅𝑡, subject to 𝑅2𝑡 >𝑀

𝜋𝜎𝑦 .

Assume similar extrusion processes i.e. 𝑅

𝑡= 𝜏 ∀ materials,

then 𝑓 =𝜌𝑅2

𝜏 , 𝑅3 >

𝑀𝜏

𝜋𝜎𝑦= 𝑅∗3 , where 2𝑅∗ = minimum OD.

𝑓∗ =𝜌𝑅∗2

𝜏=

𝜌

𝜏(

𝑀𝜏

𝜋𝜎𝑦)

2

3 ∝

𝜌

𝜎𝑦

23

= 𝐵 = material “bending index” to be minimised.

Table 3: Material bending index9

Chromoly steel, though commonly used to make bicycle frames, is not as well suited to enduring

bending as aluminium 6082T6. Titanium would be superior, but is beyond budget. Even bamboo

is better, and naturally occurring at the right diameter, but not particularly weldable. Carbon fibre

is the clear winner, and is gradually replacing aluminium in the industry at the high performance

end. However, its expense is prohibitive for the Sopalite, and difficulty in detecting structural

damage, which can be internal without displaying on the surface, is not ideal when testing a

prototype. Alloy 6082 aluminium was chosen over the slightly stronger 7075 (the current industry

favourite) for its greater weldability. All attendant plates, sleeves and bungs are likewise 6082 for

compatibility.

The sailcloth is Dacron PET with a Mylar boPET LE panel; strong, lightweight and

durable. Contemporary high performance gliders are exclusively Mylar for higher stiffness, but this

would be an inappropriate choice for the Sopalite because it would add mass and not concertina

as readily. Lighter colours are more UV stable i.e. shrink less in the sun, but show dirt more easily.

Material ρ / kg.m-3 σ y / MPa B 2R* / mm

Al 6082T6 2710 250 68 57

Bamboo 700 40 60 105

Carbon fibre 1600 600 22 43

St 4142 "chromoly" 7850 550 117 44

Titanium 4600 750 56 40



4.3. Physical modelling

There is little merit in making a scaled down model of a HG. In order to fit in the Markham wind

tunnel, the 10 m wingspan would have to be reduced to 1 m. Such a model would not be valid for

demonstrating the structural integrity of the manufacturing techniques, such as TIG welding and

cable crimping, since weld beads and ferrules are not available at 10th scale (0.5 mm diameter), nor

is substantially thinner sailcloth. Full scale test pieces are more appropriate (see §5.3).

The barrier to using a model for aerodynamic investigations is the scaling of the flowfield,

exacerbated by the effect of FSI. The same sailcloth on the model would be relatively thicker and

disproportionately heavy thus deflect less, creating an unrealistic flow. Consider the independent

variables that enter into the calculation of the structural stresses 𝜎:

flow properties – speed 𝑣, medium viscosity 𝜇, medium density 𝜌,

wing geometry – composed of angles 𝛽 and lengths 𝑙, modified by deflections 𝛿,

material properties – Young’s modulus 𝐸.

It is clear that the independent dimensionless groups include Reynolds number 𝑅𝑒 =𝜌𝑣𝑙

𝜇 and some

ratio of lengths i.e. strain e.g. 𝛿

𝑙 . Dynamic similarity requires both of these to be the same for the

model as in reality. Geometric similarity is also a necessary condition, though is not possible on a

scaled down model using the same materials as explained above. Using different materials, for

instance clingfilm, can establish geometric similarity but the different material properties impact

on the flow speed if strain is to be maintained. Even if a full set of miniaturised components could

be sourced, however, restoring 𝑅𝑒 still requires a change of medium i.e. altering the composition of

the gas in the wind tunnel, which is beyond the scope of this project. This reasoning is presented

more mathematically as follows:

Strain 𝛿

𝑙≡ 휀 =

𝜎

𝐸=

𝐹

𝐴𝐸=

𝐹[𝑝𝑙2,𝛽]

𝐴[𝑙2]𝐸[material]

Pressure 𝑝 = 𝑝[�̅�, 𝛽]

Wing loading = average pressure �̅� =1

2𝜌𝑣2𝐶𝐿[𝛼, 𝛽]

Dynamic similarity ⇒ geometric similarity ⇒ {𝛽, 𝛼}m(odel) = {𝛽, 𝛼}r(eal) same shapes scaled,

�̅� = �̅�[𝜌𝑣2], 𝑝 = 𝑝[�̅�], 𝐹 = 𝐹[𝑝𝑙2] = 𝐹[𝜌𝑣2𝑙2], 휀 =𝐹[𝜌𝑣2𝑙2]

𝑙2𝐸

Same strains 휀m = 휀r ⇒𝐹[𝜌𝑣2𝑙2]

m

𝐹[𝜌𝑣2𝑙2]r=

(𝑙2𝐸)m

(𝑙2𝐸)r=

(𝜌𝑣2𝑙2)m

(𝜌𝑣2𝑙2)r⇒

(𝜌𝑣2)m

(𝜌𝑣2)r=

𝐸m

𝐸r

Same flow regime 𝑅𝑒m = 𝑅𝑒r ⇒(𝜌𝑣𝑙)m

(𝜌𝑣𝑙)r=

𝜇m

𝜇r=

(𝑙𝐸)m

(𝑙𝐸)r

𝑣r

𝑣m⇒

𝑣m

𝑣r=

(𝑙𝐸)m

(𝑙𝐸)r

𝜇r

𝜇m

⇒(𝜌𝑙2𝐸)

m

(𝜌𝑙2𝐸)r

𝜇r

𝜇m=

𝜇m

𝜇r⇒ (

𝜇m

𝜇r)

2 𝜌r

𝜌m=

(𝑙2𝐸)m

(𝑙2𝐸)r



Fit in Markham wind tunnel ⇒𝑙m

𝑙r≤

1

10

𝐸clingfilm

𝐸Dacron=

𝐸PVC

𝐸PET=

2G

3G=

2

3⇒ (

𝜇m

𝜇r)

2 𝜌r

𝜌m= (

1

10)

2 2

3=

1

150⇒

𝜇m2

𝜌m=

1

150

(1.8∗10−5)2

1.2= 1.8 pN

If the medium to be used in the wind tunnel is air at atmospheric pressure, it would have to be

cooled to −235°C to achieve these properties according to the extrapolation of Fig. 26, but this is

below its freezing point (−215°C). Hydrogen and carbon dioxide face the same issue. Depressurising

the wind tunnel would have little effect on viscosity until near vacuum pressures, at which point

there is not so much a continuous flow over the wing as discrete molecular collisions, yielding a

highly unsteady “pressure” distribution.

Fig. 26: Temperature vs. 𝜇2/𝜌 for different gases10

The only conceivable use of a model, then, is to gain building experience, but given that I

made frames for 4 full-size BHPA standard gliders, cables for 6 and assembled 2 when working at

Avian Hang Gliders Ltd. last summer, this was deemed an unnecessary drain on limited time.

4.4. Structure

Abaqus was used to perform a finite element analysis on a simplified model of the structure. Its

input is the pressure distribution over the sail given by XFLR5, and it outputs the internal forces

within the frame and the deflections. The snout was represented by an ‘I’ beam, and fasteners were

neglected. After much difficulty with membrane parameters and shell constraints, it eventually

revealed:

Sail strain (Fig. 27) is maximum at the keel pocket, as evidenced by the presence of triple

reinforcing there on the US.

Jeremy

Rectangle



Fig. 27: Sail strain, +1g loading

The QR pin through the LE1-2 junction should be inclined at 45° pitch up relative to the z,x

plane to align with the neutral bending axis for minimum stress. For the same reason, the

LE2-3 pin would ideally be vertical, but that would prevent its connecting wires from passing

through the sail neatly.

The computed forces informed the selection of tubing and wire sizes necessary for a balanced design

i.e. where all load bearing components fail together, though naturally material availability has the

final say. §9.2 details a biconal sail method for verifying the results of the FEA.

4.5. Aerodynamics

XFLR5 is a 3D implementation of XFoil which offers 4 methods for 3D wings: lifting line theory

(LLT), horseshoe vortex lattice, ring vortex lattice and 3D panels. LLT is generally the most

accurate, especially at high 𝛼, but the vortex lattices are better for low aspect ratio or highly swept

wings. 3D panel is the only one which provides the chordwise pressure distribution. Whilst they all

agree on 𝛼 vs. �̇� and the value of 𝛼𝑀𝐺, LLT is substantially more pessimistic about performance,

and they all diverge significantly on 𝛼𝐻𝐹 i.e. 𝛼[𝐶𝑀 = 0].

Besides selecting the optimal aerofoil section, one aim of the aerodynamic design is to

position the combined centre of mass of the glider and pilot 𝑥𝐺 such that 𝛼𝐻𝐹 = 𝛼𝑀𝑆, erring on the

side of 𝛼𝐻𝐹 < 𝛼𝑀𝑆 to avoid stall. XFLR5’s values of 𝛼𝑀𝑆 are questionably high, ~40°, whereas in

reality stall occurs beyond ~27°. I therefore approximated 𝛼𝑀𝑆 ≈ 𝛼𝑀𝐺 + 2°, corresponding to

pulling the BB in 6 cm from MS to MG. The subsequent discrepancy in 𝑥𝐺[𝛼𝐻𝐹 = 𝛼𝑀𝑆] between

LLT and horseshoe vortex lattice was a worryingly large proportion of the static margin. Not

knowing which method to believe, it was necessary to incorporate the option for 𝑥𝐺 adjustment

into the design.

Resilience to pitch perturbation requires that the pilot’s centre of mass coincides with that

of the glider, otherwise when the pilot momentarily become weightless in turbulent air, the glider



pitches up\down or in extreme cases, stalls\tucks. 𝑥𝐺 adjustment consequently requires both hang

point and glider mass distribution adjustment. The former is provided by a multi-holed channel

from which to suspend the hang strap, while the latter is achieved by sliding counterweights up or

down the stinger. Once trimmed correctly, a counterweight of equivalent mass can be secured on

the inside of the stinger so that it does not impede telescoping. Welding an aluminium ring through

a hole is the most obvious method.

Studies of performance vs. DS proportion (§9.3) and washout were conducted, concluding:

A single surface (SS) sail is markedly disadvantaged at MG, though the benefits of higher %DS

diminish beyond 25%.

MG is very sensitive to washout, hence the value of VG despite its additional complexity.

5. Build

The summary of the Sopalite’s technical milestone report concluded with the line, “Unless there is

a major mishap in the supply chain, there is no reason that the build should not finish in time to

carry out a test for the final report.” In describing the subsequent progress, “major mishap” is an

understatement.

5.1. Funding

The primary stumbling block was funding. For the department that boasts the father of the jet

engine amongst its rich aviation history, it’s a shame no provision could be made by CUED to

support the Sopalite financially. Despite the obvious outreach potential of a garishly coloured

10 m wingspan student-built aircraft, complete with said student in sheepskin hat and aviator

goggles, it was not deemed worthy of a Dyson bursary or CUES grant. Nor would my college dip

into its vast reserves. It even blocked my attempt to contact alumnus, aerospace magnate and

generous donor Sir Marshall, on the selfish grounds that he should not “be troubled by a further

request on top of all they already do for us”.

Undeterred, I went on a site visit to Marshall ADG, where I distributed my written

sponsorship plea. I offered to sell up to 32 m2 advertising space on the sail, with potential exposure

at inter\national competitions and regular airings above the British countryside, typically on fair

weather days when the public is out in force. As per 8/12 such company-targeted requests, it was

ignored (the other 4 were rejected). Perhaps indicative of the declining fortunes of British industry

or British HG, 30 years ago it was commonplace for league pilots to have their sails emblazoned

with company logos – not so any more. Still hopeful, I translated the letter into Mandarin and

disseminated it in China via my cousin, to no avail.



Production sails cost around £200 for laser cutting the panels and £1,000 sewing them

together. The HG sailmaking industry is not large scale enough to warrant automation, relying on

the manual efforts of a small group of skilled craftsmen. Materials for the frame and rigging are

comparatively cheap, totalling under £500. An efficient, well-equipped production line with batch

purchased stock can therefore expect to turn out 1 aluminium and Dacron glider for approximately

£2,800 in 2 weeks, including labour for 2 people. Selling new for £3,675 gives a profit of £875 (24%),

not accounting for test flying or premises overheads.11

I am neither well-equipped, well-stocked, nor turning over the quantities required to pursue

efficiency. A prototype could easily take twice as long to sew, costing upwards of £2,000 for the

sail alone, plus £500 for the frame, hence the need for capital backing. After several members of

the HG community advised me that they would donate if a crowdfunding platform was set up, I

agreed to accept donations (reluctantly, as I would prefer to provide something in return).

Characteristically, this move was largely unsuccessful, garnering only two monetary contributions.

5.2. Procurement

Having resigned myself to taking out a loan to fund the Sopalite, sourcing the materials soon

emerged as an equally formidable problem. As of January, there were only 2 HG sailmakers in the

UK. Boat sailmakers, though more than capable, refuse to entertain aerospace applications. Despite

having personally enlisted his services previously without a hitch, one of the HG sailmakers declined

to attempt my prototype. The other announced that he would be migrating to Poland in March,

and was busy until then, so would be unable to help unless I was willing to visit him once he had

set up a sail workshop there. Fitting a bespoke sail to a new frame is not something that can be

performed remotely, and my loan would not stretch to shipping my frame to Poland and back, so

a new sail was clearly out of the question.

I therefore redimensioned the frame to fit in the US sail with a few alterations, which I was

possibly prepared to undertake on my domestic sewing machine. To compensate for the reduction

in wingspan, area and subsequent increase in min. sink rate, the TE was extended by a single

surface panel, limited by the desire to maintain a reasonably high aspect ratio. “Sopalite”

subsequently refers to this Mk. 2 version (SL2), and the original design is henceforth Mk. 1 (SL1).

Snugly telescoping aluminium tubing is surprisingly rare, even though it would be expedient

to make all tubing telescopic to save storage and transportation space. Millimetre steps in OD are

not compatible with integer millimetre wall thickness; 1/8” steps do not match 1/4” thickness, nor

the most readily available SWG thicknesses. The only workable combination, short of an expensive

custom extrusion, is the elusive 17 SWG in 1/8” steps. Before proceeding with the telescopic LE



design, I scoured the internet for a source, eventually tracking down one supplier. Satisfied of its

existence, 17 SWG tubing became a keystone of the Sopalite.

It was only months later when I contacted the supplier for a quote, that they confessed the

website was misleading, having not stocked it for several years. Naturally, this information could

not be extracted in a straightforward manner, being gleaned by contacting each one of their 11

distribution centres separately. Fortunately, after presenting my project to the Royal Aeronautical

Society (“An ultra-portable hang glider for the age of convenience”), I was introduced to microlight

manufacturer P&M Aviation, who not only possess a supply of said tubing but also offered me

their assistance free of charge.

5.3. Progress

The trials did not end there, however. By the time P&M came aboard (’18/03/22), I had almost

already given up on the prospect of building the Sopalite this year, so no other materials had been

ordered. A frenzy of purchasing ensued. The laser cut aluminium arrived late, delaying the welding

by 3 weeks. The wrong size stinger tubing was sent, its supplier refused to communicate let alone

resend, and no like square telescopic tubing could be found, prompting a redesign of the keel and

delaying the machining by 3 weeks.

The bench mountable cable swager arrived with ill-fitting jaws, requiring modification. In

order to check its integrity and test cable strength, an hydraulic ram was set up with a pressure

gauge to measure the breaking strength of short samples. A very shoddy swage (that would not be

accepted) on SD wire pulled through the ferrule at 4,908 N. A contest between an acceptable

in-house swage vs. a crimp made at Avian Ltd. (entire ferrule squeezed in a single pass) on SD wire

proved triumphant for the swage, breaking the wire at 6,537 N at the crimp end where the cross-

sectional area necks down slightly. A third test pitted a swaged 2.5 mm ferrule against a 3 mm on

HD wire. Both outlived the wire, which broke at 10,936 N at the 3 mm ferrule end (Fig. 28).

Fig. 28: Cable test rig



The ill-fated TIG welding took 5 weeks to schedule, then was hampered at the final hurdle

(after sanding off the oxide) by a faulty rig. In the meantime, the LE sleeves and bungs and keel

bungs had been glued in position to advance the drilling. The polyurethane bond is rated to

3,300 psi = 22.75 MPa, 37 times stronger than necessary for +6𝑔 even if all the LE compression is

transmitted through the LE2-3 bung, assuming the entire 35 mm long contact patch is fully adhered.

Equivalently, only 2.7% of the patch needs to adhere successfully. The versatility of gluing should

have been acknowledged earlier during the design. Unlike TIG welding, it does not require

specialised equipment and does not reduce the aluminium locally to its T0 annealed strength.

The snout assembly ultimately welded together neatly (fabrication drawing §9.5,

photograph Fig. 29), though some edges were a little awkward to access. The keel slider (Fig. 30)

could have been clamped more sturdily i.e. with distance pieces separating plates liable to pull in

during cooling.

Fig. 29: Welded snout assembly

Fig. 30: Welded keel slider

The LH LE2 tube was found to be misshapen, jamming inside LE1 and unable to house

LE3. Assembly of the frame in flight mode was able to continue whilst awaiting a replacement.

Consequently, drilling of the frame holes in stowed mode for the RH LE was carried out more

tentatively than planned – fastidiously deburring internally and marking the inner tube through

the outer hole rather than drilling through to avoid trapping swarf in the fine gap. Accumulation

of dirt with repeated use could lead to similar problems. A larger gap along the bulk of the tube

and a shim out to the current diameter at the junction would offer a more tolerant fit, though no

such combinations of tube sizes are available.



Fig. 31: RH LE stowed

Parts produced without a hitch include the battens and heat shield (Fig. 32). Battens 3-9

were restrained at the TE in the usual fashion with bungee cords through pairs of eyelets (Fig. 33).

B2 is able to share the OEM tie holding B1 (Fig. 34).

Fig. 32: Heat shield in position with WN1

Fig. 33: Batten restraint at TE Fig. 34: B1&2 sharing a batten tie

The sail modification was tricky to mark up single-handedly on a squash court floor,

suitably flat and expansive but not permitting the sail to be pinned taut. See §9.6 for the drawing.



Once transferred to a sail table at P&M (Fig. 36), attaching the TE strips, batten pockets and

spanwise zips took two full days. Semicircular reinforcement patches were sandwiched between the

two panels of the TE strip at the TE end of the batten pockets to accommodate the eyelets (stitch

just visible in Fig. 33). Concave curving of the TE between battens prevents flutter at high speeds,

and the lip is folded under itself twice for stiffness, making the TE 5 layers deep at the battens.

The spanwise zip is a chunky size 10 for robustness, terminated by an insertion pin and socket at

the tip for total separation when stowed.

Following P&M’s suggestion, the curved portions of the batten pockets are fastened to the

sail by hook and loop, rather than the webbing loops originally planned. This is easier to

manufacture, though more laborious to de\rig, and the hooks are prone to picking up detritus when

flat rigging. It also fully separates the sail from the LE tubing when derigging, opening up the

possibility of rolling rather than concertinaing the sail (see §7.2).

Fig. 35: Sail RHS separated from LE; bottom surface folded up around onto top surface,

exposing curved portions of battens

Another deviation from the design is due to the standard width of sailcloth roll. Rather

than double the complexity, labour time and opportunity for imperfection by forming the TE strip

from two panels in the chordwise direction, a slight reduction in chord length enabled it to be cut

out of one. Seguing the strip into the original TE at the root takes advantage of the existing

reinforcement at the keel pocket. It is both critical for steering the glider, dragging the keel around

with the sail during a turn, and the most highly stressed part of the sail (see Fig. 27), so the fewer

stitch holes puncturing this region the better.



Fig. 36: Sail LHS ready to receive eyelets

Even though many materials and services were gratefully received free of charge, £890.80

has already been spent on the build, detailed in §9.4. This rises to £1,260.43 if accounting for travel

costs associated with travelling between Cambridge, Taunton, Marlborough, Bristol, Sheffield,

Shepton Mallet and Tiverton for various resources.

Fig. 37: Compressed concertina sail

Fig. 38: De\rigging on the URs, advisable on rough terrain

490 mm



6. Testing

Certifying a HG requires a land based structural and aerodynamic test to prove its structural

integrity and positive pitch stability. This involves securing it above a specially adapted car at

specified angles of attack 𝜃 and driving along a runway. Simulating ±𝑛𝑔 loading for a flight speed

𝑣 and angle of incidence 𝛼 entails driving at ±𝑣√𝑛 (airspeed) with 𝜃 = 𝛼. A force meter resisting

pitching motion measures the pitching moment to gauge static longitudinal stability, which should

be positive ∀ |𝛼| < 90°.

Insufficient time was available to complete the remaining work outlined in §7.1. In

particular, several iterations may be required to tighten the sail uniformly. Hiring the BHPA rig

(the only one in the UK) incurs a not insubstantial expense, so it is prudent to submit only a

complete build in order to extract cost-effective, worthwhile results. The Sopalite was therefore

given a preliminary +4𝑔 static load test to assess the structure independently of the aerodynamics.

Typically, sandbags are placed on the upturned sail to impose the relevant distributed

flight loading.12 In this case, roof tiles were found to be a superior (and more abundant) option.

Their uniform mass permitted a fine and regular load increment of 4.25 kg, whilst their tessellating

shape and rough surface allowed them to be positioned methodically without slipping off. Sandbags

have a tendency to slide as the sail twists, requiring that the TE be held up artificially.

A Megarailer roadrail excavator was mobilised as a crane, courtesy of Rexquote Ltd., from

which the Sopalite was suspended upsidedown via the hang strap. Builders’ bags and rubber floor

mats protected the sailcloth from the coarse tiles (Fig. 41). A bracing strap across the control frame

via the suspension secured the glider in pitch without affecting the loading (Fig. 43).

340 kgf = 3,335 N was added symmetrically, which combined with the glider’s self-weight simulates

+4𝑔 for a pilot of mass 63.25 kg.

Fig. 39: Builders’ bags secured to nose wires and keel



Fig. 40: Inverting the Sopalite

Note that the aftmost part of the TE is just clear of the ground, avoiding batten bending

during an aggressive landing flare. The Citroën sponsorship deal brokered by the US’s original

owner is sadly no longer active.

Fig. 41: Non-slip roof tile\rubber mat interface at +2g

Fig. 42: Substantial sail billow at +4g



Fig. 43: Suspension chain and bracing strap, +4g

Fig. 44: +4g



As per the specification, the cables, LEs, keel, sail, KP and control frame all survived

without irreversible deformation, confirmed for the tubing by its enduring ability to telescope snugly.

The only component to stray from the elastic regime was the upper snout plate, bent by the

bowsprit but not catastrophically (Fig. 45). This is the preferred failure mode, as it would have

little effect on handling characteristics if inflicted during flight, yet would certainly be noticed

during derigging. The structural analysis of §4.4 did not detect this weakness because the annealing

effect of the welding could not be predicted accurately.

Fig. 45: Plastically deformed upper snout plate

7. Conclusions

The technical side of the project was largely successful as far as can be concluded from the static

load test. Specification points 1, 2 and part of 6 were achieved. An ultra-portable flexwing hang

glider was designed and a prototype built, which weighs 29 kg and stows compactly enough to fit

inside a Toyota Yaris. De\rigging is closer to the 40 minute mark than 20, but this is expected to

drop as the process is streamlined through familiarity. The structure passed a +4𝑔 static load test,

except for some minor plastic deformation on the snout.

Despite getting organised early, starting the design in earnest 4 months before the beginning

of this academic year, logistics prevented the project from completing the plan set out in the

technical milestone report. The innate audacity of the project is not exclusively responsible for this

failure – hang gliders have been successfully designed, built and flown for final year projects.12 It

seems that reliability is currently a rare commodity in the British supply chain. Had even half the

suppliers delivered correctly and punctually, the build might have been finished in time to perform

flight tests. There is only so much slack that can be incorporated within an 8 month timeframe.

This was largely used up fruitlessly seeking funding, when perhaps the backup plan of adapting the

Ultrasport should have been activated sooner.



7.1. Outstanding work

Owing to the late build start and myriad mishaps, there is much still to be done before aerodynamic

testing can be undertaken.

Widen the keel pocket, which currently prohibits the full range of bowsprit telescopic motion,

to accommodate the stowed keel slider.

Tighten the sail at the LE in the chordwise direction by removing material from the bottom

surface, bringing the spanwise zip forwards 30 mm.

Tighten the sail along the LE in the spanwise direction by gathering material at the root with

laces through eyelets straddling the keel battens (to achieve the effect shown in Fig. 46). This

region is covered by the snout cone so scrunching the underlying fabric will not affect the

airflow.

Fig. 46: Spanwise tensioning demonstration

Tighten the sail’s bottom surface in the spanwise direction by removing 40 mm of material

alongside the keel zip.

Machine off bung LE1-2 and sleeve LE2-3 from the misshapen LH LE2, checking how much

adhesive area was achieved. Glue onto the replacement then drill the holes.

Reshape the flatter battens with a rounder profile at the LE to transfer the sail more smoothly

onto the LE.

Unstitch the curved section of the innermost battens B1, replacing with hook and loop fastener

as per B2-9. This was not performed earlier as it was not certain that B1 would be necessary.

Source correct length bolts. Excessively long ones have sufficed for the preliminary assembly.

Burn off excess to terminate the batten TE bungees.

Replace the damaged snout plate and reinforce, or redesign as per §7.2.

No doubt more challenges will present themselves as the above points are addressed, but that is to

be expected for a prototype.



7.2. Changes for Mk. 3

If the Sopalite Mk. 2 impresses sponsors enough to finance a sequel, a few potential alterations are

already apparent, and more would likely emerge during aerodynamic testing.

Investigate the feasibility of bamboo for the LEs, offering reductions in mass and carbon

footprint. Seeing as weldability is no longer a concern, it only remains to check its water

resistance, fatigue properties and machinability.

Source thinner walled square section for the stinger.

Restrict the angular motion about the 𝑥-wise pivot through each UR top fitting. Moderate

rotation allows the wing to roll relative to the control frame so that the LE tip touches the

ground, alleviating stress imparted to the snout by the LEs when de\rigging on the control

frame on uneven ground. Too much rotation, however, inconveniences the latter\earlier stages

of de\rigging, threatening to tip the top-heavy bundle.

Coat the keel in PTFE film as a slippery shim, simultaneously taking up the slack between the

tubes and easing the telescoping, which is especially difficult when loads are applied.

Widen the snout keel aperture and use needle rollers to facilitate more effortless tensioning.

Consider redesigning the snout assembly for gluing rather than TIG welding.

Folding the sail neatly is time-consuming. Either: run a drawstring from the sail tip through

regular loops to the sail root, then through the LE tube from the root to the tip, facilitating

quicker concertinaing. Or: respace the batten pockets such that the battens collect at the same

position on the circumference when the sail is rolled up from the tip to the root. Rolling is

faster than folding and avoids creasing but this would entail larger gaps between battens at the

root, risking bagginess.

Explore the use of PE fibre as a lighter substitute for steel cable. These are commonplace on

PGs and kitesurf wings but not HGs, possibly due to the latency in altering consumer

perceptions.

Fig. 47: Spectra PE kitesurf line, the future of HG rigging?

Revert to the original plan of a bespoke sail to avoid fitting problems.



7.3. Applications

Applications for an ultra-portable hang glider are not just confined to the leisure industry.

Exploration of other planets could benefit from a lightweight craft that occupies minimal volume

in the interplanetary spacecraft, yet when unfurled at the destination is capable of carrying a useful

payload over a significant range. An orbiting probe can only scan the surface in limited detail,

whilst terrestrial vehicles face mobility issues. On Mars, for example, canyons are sites of interest

in the search for water and minerals, but their complex terrain is problematic for the passage of

rovers. A “Sopamars” flexwing microlight, powered by solar panels or a nuclear reactor, could skim

over the surface at any desired height within the atmosphere, capturing high definition imagery or

ferrying equipment and personnel.

As well as being more portable than a rigid wing craft, the Sopamars would boast a slower

flight speed, permitting greater scanning detail, shorter takeoff and landing and smaller turning

circles. Though not quite as portable, it is fundamentally more efficient than a paraglider, which

relies on ram drag to inflate its cells. Just as aeroplanes have a greater range than helicopters, the

Sopamars could travel further than a rotary drone, and its sail planform is more conducive to

affixing solar panels. Furthermore, the absence of moving parts renders the weightshift flexwing

the simplest craft to maintain and repair, essential for space missions where resources are inherently

scarce.

Due to the rarefied atmosphere, flight speed on Mars is higher than on Earth. Martian

gravitational acceleration 𝑔𝑀 = 3.71 m. s−2 at the surface, meaning that the Sopamars would not

need to be as sturdy as the Sopalite to withstand [−3,6]𝑔𝑀 loading. Assuming the same planform,

aerofoil section and materials, the analysis of §9.8 demonstrates that Sopamars flight speed

𝑣𝑀 = 82 mph with the same sail area 𝑆 = 15 m2 , dropping to a minimum 𝑣𝑀 = 50 mph at

𝑆𝑀 = 100 m2.

Back on Earth, a microlight trike coupled to a Sopalite wing could offer a transport solution

that is more compact to park than existing flexwing microlights, with far greater range than rotary

drone taxis and fuel consumption comparable to a car.13 Consider my journey between my

Somerset home and Jesus College, Cambridge. In my 2001 Toyota Yaris, the 235 miles via the M4

and M11 take between 4 and 6 hours, depending on traffic, and consume around 33 litres of

unleaded petrol. Alternatively, with the Sopalite stowed overhead and the propeller enclosed in a

safety cage, I could taxi the “Sopatrike” 150 m to the closest field suitable for TO. Unfolding the

wing, then flying the 161.5 miles in a straight line to Jesus Green at a cruising speed of 75 mph

would take less than 2.5 hours, consuming around 28 litres of unleaded petrol, (ignoring landing

restrictions in public spaces, and assuming similar wing efficiency to the Quik GT450).14 The

required parking space is even less than the Yaris.



7.4. Future prospects

Ironically, the high quality of workmanship required to pass gliders through certification ensures

that they are robust enough to last several decades with minimal degradation, swamping the

secondhand market with serviceable specimens that heavily undercut manufacturers. Combined

with the dwindling number of HG pilots, this has driven many factories out of business, so that

there is only one left in the UK, a few in mainland Europe and a handful in the USA and Australia.

On the other hand, the Chinese market is ripe for exploitation, with its vast array of

mountains and burgeoning nouveau riche seeking outdoor thrills. Where stringent (and enforced)

transport regulations regarding vehicle overhang prohibit the use of standard HGs, the Sopalite

could excel, provided the design is protected by an airtight patent and actively defended by an

energetic legal team. Entrenched in the quagmire of oriental bureaucracy is not a status I wish to

pursue in the next few years, however, so plans to monetise the Sopalite are on the backburner for

now.

In the immediate future, I intend to complete the build and alterations and test the Sopalite

aerodynamically on the BHPA rig. If it passes, I will test fly the Sopalite, initially on small dunes,

progressing to bigger hills and eventually fulfilling its potential by taking it up ski lifts to launches

never before accessed by HGs, where only eagles dare.

8. Acknowledgments

Avian Ltd. – for the URs, KP, battens, fittings, work experience, hoodie and expertise.

Dr Fehmi Cirak – for believing in my project.

James Porter – for assistance with sail markup.

John Soper – for the machining and trailer.

Jonathan Howes – for providing a Weissinger method implementation with which to critique

XFLR5, and donating to my crowdfunding campaign.

P&M Aviation – for the LEs, sail modification, consulting and enthusiastic factory tour.

Rexquote Ltd. – for use of a MegarailerTM roadrail excavator.

Roger Soper – for everything.

Simon Murphy – for lending me a glider to use now that my US is dismantled, and donating

to my crowdfunding campaign.

Steven Blackler – for filming my RAeS presentation and providing regular encouragement.



9. Appendices

9.1. Numerical values

Table 4: Ultrasport vs. Sopalite – geometric comparison

Table 5: Sources of form drag

US SL1 SL2

Sail plan area / m2 S 13.84 16.00 14.97

Wingspan / m 2s 9.957 10.035 9.957

Mean chord / m c 1.390 1.594 1.503

Aspect ratioA

R 7.16 6.29 6.62

Mass / kg m 28 26 29

Wing loading / Pa WL 78.0 66.2 72.7

Attribute

Diameter Length Qty. Shape Frontal area 2D drag coefficient Contribution

Ultrasport US d / m l / m q A f / m2 c d q.c d .A f/S %

basebar BB 0.025 1.360 1 cylinder 0.034 1.2 0.00295 7.9

kingpost KP 0.025 1.255 1 aerofoil 0.031 0.12 0.00027 0.7

leading edge LE 0.14 4.978 2 aerofoil 0.697 0.12 0.01208 32.6

lufflines 0.0015 15.710 1 cylinder 0.024 1.2 0.00204 5.5

payload 0.3 0.600 1 prone human 0.180 0.89 0.01156 31.2

rigging wires 0.0032 22.042 1 cylinder 0.071 1.2 0.00611 16.5

upright UR 0.0262 1.720 2 aerofoil 0.045 0.12 0.00078 2.1

wheel 0.15 0.050 2 cylinder 0.008 1.2 0.00130 3.5

Sum Σ 0.0371

Σ(q.c d .A f ) 0.514

Sopalite SL1

basebar BB 0.025 1.254 1 cylinder 0.031 1.2 0.00235 6.6

kingpost KP 0.025 1.182 1 aerofoil 0.030 0.12 0.00022 0.6

leading edge LE 0.14 5.018 2 aerofoil 0.702 0.12 0.01054 29.4

lufflines 0.0015 14.126 1 cylinder 0.021 1.2 0.00159 4.4

payload 0.3 0.600 1 prone human 0.180 0.89 0.01000 27.9

rigging wires 0.0032 38.763 1 cylinder 0.124 1.2 0.00930 26.0

upright UR 0.0262 1.717 2 aerofoil 0.045 0.12 0.00067 1.9

wheel 0.15 0.050 2 cylinder 0.008 1.2 0.00113 3.1

Sum Σ 0.0358

Σ(q.c d .A f ) 0.573



9.2. Structural sanity check

Taking moments about the keel in front view (Fig. 48), 𝑀(𝐾)𝑥 = 0:

Tension[basebar] 𝑇𝐵𝐵 =𝑧𝐿

𝑦𝐵𝐵

𝐿

2

Tension[bottom side wire] 𝑇𝑊𝐵𝑆 =𝑧𝐿

𝑧𝑊𝐵𝑆

𝑙𝑊𝐵𝑆

𝑦𝐵𝐵

𝐿

2

Fig. 48: Front (-z,y) view of frame RHS, cut through BB

Summing the forces in y, Σ𝐹𝑦 ↑ = 0:

Compression[upright] 𝐶𝑈𝑅 =𝑙𝑈𝑅

𝑙𝑊𝐵𝑆𝑇𝑊𝐵𝑆 =

1

𝑧𝑊𝐵𝑆 cos 𝜙𝑈𝑅

𝑧𝐿𝐿

2

→ to avoid UR buckling, connect WBS outboard, narrow AF.

Fig. 49: Front (-z,y) view of frame RHS, cut through bottom side wire and UR

Beam section stress 𝜎 =

𝑀𝑥𝑦

𝐼+

𝑀𝑦𝑥

𝐼+

𝑇

𝐴

= 𝜎𝐵 + 𝜎𝑇

Stress due to bending 𝜎𝐵 = (𝑀𝑥 sin 𝜃𝑡 + 𝑀𝑦 cos 𝜃𝑡)𝑟

𝐼

𝑑𝜎𝐵

𝑑𝜃= 0 @ 𝜃𝑡 = tan−1

𝑀𝑥

𝑀𝑦

max𝜃𝑡

𝜎𝐵 = √𝑀𝑥2 + 𝑀𝑦

2 𝑟

𝐼

Maximum magnitude maxm𝜃𝑡

𝜎 = −√𝑀𝑥2 + 𝑀𝑦

2 𝑟

𝐼+

𝐶

𝐴 (compression)

where 𝐴 = 𝜋(𝑟2 − (𝑟 − 𝑡)2), 𝐼 =𝜋

4(𝑟4 − (𝑟 − 𝑡)4) for circular tube.

Fig. 50: LE section

L/2

W/2

TBB

zL

yBB

K

lWBS

lUR

L/2

W/2

TWBS CUR

zWBS

r

t

x'

y

𝜃𝑡



Tension applied to sail by frame 𝑇𝑆[𝑥] = �̅�𝑆[𝑥]2𝑟𝑆[𝑥]

Sail modelled as a pair of cones, s.t. z,y sections can be approximated as segments of

a virtual cylindrical pressure vessel with uniform spanwise pressure.

Fig. 51: Aft (z,y) view of RHS as pressure vessel

Moments about snout (Sn)–LE pin 𝑀(pin)𝑦 = 0 = 𝑥𝑁𝑇𝑊𝑁1 sin 𝜓𝑊𝑁1 − ∫ −𝑥𝑇𝑠 cos 𝜙𝑆0

𝑥𝐾𝑑𝑥

𝑀(pin)𝑥′ = 𝑧′𝑊𝐵𝑆𝑇𝑊𝐵𝑆

𝑦𝐵𝐵

𝑙𝑊𝐵𝑆− csc 𝛬 ∫ −𝑥𝑇𝑠 sin 𝜙𝑆

0

𝑥𝐾𝑑𝑥

Fig. 52: Plan (z,x) view of frame RHS w.r.t. 𝑀(𝑝𝑖𝑛)𝑦

Fig. 53: Aft (z,y) view of RH LE

𝜓𝑊𝑁1

𝑇𝑆 cos 𝜙𝑆

z

𝛬

z'

x'

x

z'

TWBS

y 𝑇𝑆 sin 𝜙𝑆

z'WBS

𝑀(pin)𝑥′

TS TS

TS

TS

�̅�𝑆

rS 𝜙𝑆

z

TS 𝜙𝑆

TS �̅�𝑆

zLE

𝑦𝑆

y



Compression[LE @ Sn] 𝐶𝐿𝐸𝑆𝑛= 𝑇𝑊𝑁1 sin(𝜓𝑊𝑁1 + 𝛬) + cos 𝛬 ∫ 𝑇𝑠 cos 𝜙𝑆

0

𝑥𝐾𝑑𝑥

Fig. 54: Plan (z,x) view of RH LE

Tension[tensioning wire] 𝑇𝑊𝑇 = 𝑇𝑊𝑁1 cos 𝜓𝑊𝑁1 = 𝐶𝐾 compression[keel]

Fig. 55: Plan (z,x) view of frame RHS w.r.t. keel compression

Stresses at contact areas with pin thru LE @ Sn 𝜎𝐿𝐸𝑆𝑛=

1

2𝑟pin𝑡(∓

𝑀(pin)𝑥′

2𝑟𝐿𝐸1−

𝐶𝐿𝐸𝑆𝑛

2)

Survival criterion for bung\Sn: |𝜎𝐿𝐸𝑆𝑛| ≤ 𝜎𝑦 → 2𝑟pin𝑡 ≥

1

2𝜎𝑦(

𝑀(pin)𝑥′

𝑟𝐿𝐸1+ 𝐶𝐿𝐸𝑆𝑛

),

where 𝑡 = thickness of bung wall\Sn plate.

𝑇𝑊𝑁1

𝑇𝑆 cos 𝜙𝑆

pin

Sn-LE

𝐶𝐿𝐸𝑆𝑛

𝑇𝑊𝑇

𝑇𝑊𝑇 𝐶𝐾

𝐶𝐾



9.3. Aerodynamic influence of sail double surface proportion

�̇� / m.s-1

−𝑦 /

m.s

-1

𝛼°

�̇� / m.s-1

𝛼°

𝐶𝑀

GR G

R

�̇� / m.s-1

𝛼°



9.4. Bill of materials

Abbreviation Description Dimensions Material Detail Supplier Comment

1 2 Glider Extra Total mm Unit Total 1260.43

Category B 4 plate Sn Sn 2 2 4 9.64 19.28 Al 6082 ideally Al 6061 Luffman late

attached assy. A B 5.1 bung LE01 LE1 N 2 2 2.99 5.99 Al 6082 lathe+saw MCIH

frame block B B 5.2 bung LE12 LE2 F 2 2 3.75 7.51 Al 6082 turn+bore+saw MCIH

consumable C B 5.3 bung LE23 LE3 F 2 2 2.94 5.88 Al 6082 lathe+saw MCIH

fitting bespoke D B 5.4 sleeve LE12 LE1 A 2 2 3.60 7.20 Al 6082 saw Forward Metals

equipment E B 5.5 sleeve LE23 LE2 A 2 2 3.09 6.18 Al 6082 saw Forward Metals

frame tube F B 7.2 saddle KP mount KP 2 2 6 5.38 10.76 Al 6082 Luffman

joined assy. J B 8 heat shield K N 1 1 8.18 8.18 Al 6082 lathe+saw+mill MCIH

sail S B 9 guide K Sn 2 2 4 2.34 4.68 Al 6082 Luffman

travel T B 10 brace Sn lat Sn 2 2 4 5.86 11.72 Al 6082 Luffman

wire W B 11 brace Sn long Sn 2 2 4 2.20 4.40 Al 6082 Luffman

accessory Z B 12 bung sail retainer LE3 sail tip 2 2 0.00 plastic US

B 14 plate slider T slider KPUR 1 1 4 6.16 6.16 Al 6082 Luffman

Item B 15.1 plate slider SA slider KPUR 2 2 4 2.60 5.20 Al 6082 Luffman

A frame AF B 16 plate slider B slider KPUR 1 1 4 2.32 2.32 Al 6082 Luffman

aluminium Al B 17 swivel UR T UR T 2 2 0.00 US

keel K B 18 connector UR UR 4 4 0.00 US

kingpost KP B 19 connector BB BB 2 2 0.00 US

leading edge LE B 20 bung stinger stinger A 1 1 0.00 plastic ukplasticparts eBay

nose N B 21 spacer slider snout 1 1 10 13.54 13.54 Al 6082 Luffman

snout Sn B 22.1 bung KMB K MF 1 1 3.74 3.74 Al 6082 saw+mill Forward Metals

stainless steel SS B 22.2 bung KSM stinger F 1 1 3.74 3.74 Al 6082 saw+mill MCIH

steel St B 23 hang channel slider KPUR 2 2 4 3.58 7.16 Al 6082 Luffman

upright UR C 1 ferrule 2.5 wires 30 10 40 0.00 0.00 St Avian

Ultrasport US C 2 eyelet St P&M

C 3 washer LE Sn LE 4 4 40x12.5x1.5 nylon/PE OD x ID x t

Locale C 4 bolt hex M12x90

fore/aft F/A C 5 washer plain M12 bolt LE Sn 2 2

right/left R/L C 6 nut nyloc M12

top/bottom T/B C 7 bolt hex M6x60

mid M C 8 nut nyloc M6

side S C 9 washer plain M6

Item ID Location Quantity Price



C 10 bolt skt M6x60

Process C 11 bolt skt M6x70

assemble in houseAIH C 12 wire rope 3.5

machine in houseMCIH C 13 thimble wire rope 3.5wire rope

hole to hole (for wire making)h2h C 14 shackle bow snout tensioning strop2 2 M8x6.35 6.18 12.36 St RS124-4812 0.5 t +nut+split pinRS

C 15 bolt hex M8x120 Sn shackle bow 2 2 M8x112

C 16 nut nyloc M8 Sn shackle bow 2 2

C 17 washer plain M8 Sn shackle bow 2 2

C 18 bolt skt M8x12 Sn batten K 1 1

C 19 bolt csk M6x50

C 20 pin ball lock 10x80 LE 4 4 dxl shank 23.90 95.59 SS WDS 955-10080 WDS

C 21 bolt skt M6x20

C 22 bolt skt M6x90

C 23 bolt skt M6x55

C 24 bolt hex M12x110

C 25 wire rope 3 HD 7x19 St 10936 N break Avian

C 26 wire rope 2.5 SD 7x7 St 6537 N break Avian

C 27 pin ball lock 10x60 K 3 3 20.66 61.98 SS WDS 955-10060 WDS

C 28 lanyard w/ tab 10x6"pin ball lock 10 7 7 3.54 24.77 SS WDS 250-890056V

C 29 tensioning strop TE snout 1 1 1" x 4111 0.00 webbing P&M

C 30 zipper insertion pinzip spanwise 2 2 size 10 7.10 ganc_uk eBay

C 31 zip spanwise undersurface join 2 2 10c x 5 m 0.00 P&M

D 1 tang flat AF wire S AF 2 2 SS 316 US/Avian

D 1.2 tang bent LE wires N LE 2 2 30 deg, h2h 30 SS 316 laser & bend

D 2 tang bent K wires T K T 2 2 SS 316 Avian

D 3 tang double bent wire B K B 2 2 SS 316 Avian

D 5 tang triple bent LE23 WS, WN1 2 2 h2h 31 34.56 SS 316 laser & bend

D 6 tang tensioning stroptensioning stropstinger S 2 2 SS 316 smooth laser

E 1 swager 1 1 78.37 bench mounted GSProducts

E 2 welding rod TIG 5356 1 1 20.23 1 kg R-Tech

E 3 stitch unpicker 1 1 1.90 seam ripper Sew Creative

E 4 glue Gorilla LE sleeves and bungs and keel bungs1 1 5.60 Homebase

Abbreviation Description Dimensions Material Detail Supplier Comment

1 2 GliderExtra Total mm Unit Total 1260.43




Description Dimensions Material Detail Supplier Comment

1 2 GliderExtra Total mm Unit Total 1260.43


F 1.1 LE1 Sn LE2 2 2 2.1/4"x17 SWGx2k 0.00 Al 6082 OD x t x l P&M

F 1.2 LE2 LE1 LE3 2 2 2.1/8"x17 SWGx2k 22.16 Al 6082 0.5 clearance each side P&M LH misshapen

F 1.3 LE3 LE2 2 2 2"x17 SWGx2k 0.00 Al 6082 sq P&M

F 4 tube K M K N K KP 1 1 45x2x1045 17.56 Al sq 2k Metalsshop

F 5 tube KP K M 1 1 0.00 Al aerofoil US/Avian

F 6 tube bowsprit K N 1 1 50x2x1480 16.20 Al sq 2k Metalsshop

F 8 BB AF 1 1 1360? 0.00 Al round Avian

F 9 tube UR 2 2 4 1560? 0.00 Al aerofoil US

F 10 tube stinger K A 1 1 40x2x1860 38.81 Al sq 2k Metalsshopsent wrong size

S 3 sail modification 1 1 0.00 P&M

T 1 train return Taunton Cambridge 3 3 59.40 178.20

T 2 car return Taunton Marlborough 1 1 40.30

T 3 car return Taunton Sheffield 1 1 75.51

T 4 car return Taunton Tiverton 1 1 33.22

T 6 car return Taunton Henbury, Torr Works1 1 42.40

W 1 wire BS AF LE 2 2 3 St HD 7x19, galv not SS AIH

W 2 wire BA AF stinger B 2 2 2.5 St SD 7x7 AIH

W 3 wire BF AF N B 2 2 2.5 St AIH

W 5 wire T lat LE-KP LE 1 1 2.5 St AIH

W 6 wire T long N-KP K TA 1 1 2.5 St AIH

W 7 wire N1 N split 2 2 4 St AIH

W 8 wire N2 split LE1/2 2 2 3 St AIH

W 9 wire N3 split LE2/3 2 2 3 St AIH

Z 1 sticker sail sail LH 1 1 1x1 m 0.00 Dacron adhesive cut+stick in-house

Z 2 bag 1 1 2.2x0.6x0.5 m 0.00 US

Z 3 US 1 1 300.00

A 0 GA 1 AIH

A 1 spine 1 AIH

A 2 arms 1 AIH

A 4 sail K LE3 tip 1

A 4.1 sail one side 2

A 5 LE snout 2 glue+drill in-house

A 6 KPUR K M 1 AIH

J 4 snout 1 1 10.00 10.00 Andy May

J 5 slider KPUR 1 1 10.00 10.00 Andy May



9.5. Snout fabrication drawing

6082



9.6. Sail modification drawing



9.7. Retrospective safety assessment

The project was accomplished safely thanks to the due diligence of everybody involved.

Hazard encountered Potential consequence Risk Mitigation techniques Comment

Computer use Eyesight damage HighMaximise natural ambient light,

perform regular eye exercises

Society in general is overly accepting of eyesight degradation and makes

little provision to prevent or retard it. CUED is no exception, with dimly

lit lecture theatres and the drive to go paperless forcing us to spend even

longer in front of computer screens.

Back pain High Use standing desk

After gaining the stamina to stand for long periods, the standing desk has

had a very positive impact on my health and efficiency. Highly

recommended.

Driving car Death/serious injury Moderate Rest when tired, travel at night when roads quieter

with trailer Note longer stopping distance, ensure tow hitch secure

Hang gliding Death/serious injury Moderate Assess conditions carefully, inspect equipment thoroughly before each flight, carry reserve parachute

Machining, welding Serious injury Moderate Stay vigilant, wear PPE, use appropriate guards

Using excavator as crane

in confined spaceSerious injury Low

Attach lifting equipment securely

with redundancy, assist operator

with another pair of eyes on the

ground when manoeuvring

Dynamic lifting equipment is much better suited to the task of raising a

fully-laden hang glider than attempting to hoist over a ceiling joist.

Would use again.

Working at height on

excavator and ladderSerious injury Low

Check shoelaces tied, hold ladder

firmly



9.8. Martian flight

Subscripts 𝐸 and 𝑀 denote Earth and Mars.

In level flight, lift balances weight: 𝐿 =1

2𝜌𝑣2𝑆𝐶𝐿 = 𝑊 = (𝑚𝑝 + 𝑚𝑔)𝑔,

where 𝑚𝑝 and 𝑚𝑔 are the masses of the payload and glider respectively.

Structural forces 𝐹 = 𝜎𝐴 ∝ 𝑊

Stressed area 𝐴 = 𝑡2, where 𝑡 = characteristic thickness

(intermediate variable so absolute value is arbitrary, chosen 𝑡𝐸 = 2 mm).

𝑚𝑔 = 𝜌𝑔𝑆𝑡, where 𝜌𝑔 = characteristic glider density =𝑚𝑔𝐸

𝑆𝐸𝑡𝐸=

29

15∗0.002= 967 kg. m−3 .

Keeping the stresses within the same limits: 𝜎𝑀

𝜎𝐸= 1 =

𝑊𝑀𝑡𝐸2

𝑊𝐸𝑡𝑀2 =

(𝑚𝑝+𝑚𝑔𝑀)𝑔𝑀𝑡𝐸

2

(𝑚𝑝+𝑚𝑔𝐸)𝑔𝐸𝑡𝑀

2 =(𝑚𝑝+𝜌𝑔𝑆𝑀𝑡𝑀)𝑔𝑀𝑡𝐸

2

(𝑚𝑝+𝑚𝑔𝐸)𝑔𝐸𝑡𝑀

2

→ quadratic in 𝑡𝑀 → 𝑡𝑀 =𝜌𝑔𝑆𝑀𝑔𝑀𝑡𝐸

2

2𝑊𝐸(1 + √1 +

4𝑊𝐸𝑚𝑝

(𝜌𝑔𝑆𝑀𝑡𝐸)2

𝑔𝑀

) .

Flight speed 𝑣𝑀 = √2𝑊𝑀

𝜌𝑀𝑆𝑀𝐶𝐿

𝑆𝑀 = 𝑆𝐸 ⇒ 𝑡𝑀 = 1.17 mm, 𝑚𝑔𝑀= 16.9 kg ⇒ 𝑣𝑀 = 36.7 m. s−1 ≡ 82.1 mph

𝑑𝑣𝑀

𝑑𝑆𝑀= 0 @ 𝑆𝑀 = 100.49 m2 ⇒ 𝑡𝑀 = 1.85 mm, 𝑚𝑔𝑀

= 180 kg ⇒ 𝑣𝑀 ≥ 22.5 m. s−1 ≡ 50.4 mph



Bibliography

I. Kroo, Aerodynamics, Aeroelasticity, and Stability of Hang Gliders – Experimental Results,

1981, NASA

R. Haberle et al., The Atmosphere and Climate of Mars, 2017, Cambridge Planetary Science

G. de Matteis, Dyanmics of Hang Gliders, 1991, AIAA

S. Hoerner, Fluid-Dynamic Drag, 1965, Hoerner

P. Dees, Hang Glider Design and Performance, 2010, AIAA

D. Boote & M. Caponetto, A numerical approach to the design of sailing yacht masts, 1991,

Tenth Chesapeake Sailing Yacht Symposium

D. Pagen, Performance Flying, 1993, Black Mountain Books

K. Nickel & M. Wohlfahrt, Tailless Aircraft in theory & practice, 1994, Butterworth-Heinemann

References

1 Graph compiled from data given by:

Flybubble, Paragliders: Weight Ranges, 2015, https://flybubble.com/blog/paragliders-weight-ranges

[’18/11/12],

Swing, Astral 7 – Glide ratio > 10 !!!, 2012, http://www.swing.de/article/items/astral-7-glide-ratio-

10.html [’18/11/12],

Moyes Delta Gliders, Litespeed RX – Specifications, https://www.moyes.com.au/products/hang-

gliders/litespeed-rx/specifications [’18/11/12],

USA Soaring Team, Sailplanes & Gliders, 2004,

http://www.ssa.org/files/member/BR%20Sailplanes%20V3%2004.pdf [’18/11/12] 2 Aériane S.A., Swift Light Technical Data,

http://www.aeriane.com/products/aircrafts/swift/swiftlight/ [’18/01/16] 3 Finsterwalder GmbH., The Features of the Fexes, https://finsterwalder-charly.de/en/hanggliders-a-

accessories/hangglider-features.html [’18/04/28] 4 Aeros Ltd., Target Manual, http://www.aeros.com.ua/manuals/Target_en.pdf [’18/04/28] 5 Wills Wing Inc., A Brief History of Hang Gliding, Paragliding and Wills Wing, 2012

https://www.willswing.com/a-brief-history-of-hang-gliding-paragliding-and-wills-wing/ [’18/02/05] 6 bautek GmbH., bautek Astir, http://www.bautek.com/index.php/astir-en.html [’18/05/04] 7 S. Murphy, Vintage Gliders, http://www.turfhouse.com/acatalog/Vintage_gliders.html [’18/05/04] 8 Apco Aviation Ltd., Thrust V,

http://www.apcoaviation.com/products.asp?section=paramotors&product=thrust%20V [’18/05/04] 9 Performance Composites Ltd., Mechanical Properties of Carbon Fibre Composite Materials, http://www.performance-composites.com/carbonfibre/mechanicalproperties_2.asp [’18/05/06] 10 Graph compiled from data given by CUED, Thermofluids Data Book, 2017 11 Avian Ltd., Fly 15, http://www.avianonline.co.uk/fly-15-p-1827.html [’18/05/06] 12 W. Brooks, Handley Page Named Lecture 2017, https://www.aerosociety.com/news/video-and-

audio-archive-handley-page-named-lecture-2017/ [’18/05/24] 13 N. Lavars, Autonomous Passenger Drone swoops onto the flying taxi scene, 2017,

https://newatlas.com/passenger-drone-flying-taxi/51539/ [’18/05/23] 14 P&M Aviation, Quik GT450 Performance Data, http://www.pmaviation.co.uk/gt450.html

[’18/05/23]

https://flybubble.com/blog/paragliders-weight-ranges

http://www.swing.de/article/items/astral-7-glide-ratio-10.html

http://www.swing.de/article/items/astral-7-glide-ratio-10.html

https://www.moyes.com.au/products/hang-gliders/litespeed-rx/specifications

https://www.moyes.com.au/products/hang-gliders/litespeed-rx/specifications

http://www.ssa.org/files/member/BR%20Sailplanes%20V3%2004.pdf

http://www.aeriane.com/products/aircrafts/swift/swiftlight/

https://finsterwalder-charly.de/en/hanggliders-a-accessories/hangglider-features.html

https://finsterwalder-charly.de/en/hanggliders-a-accessories/hangglider-features.html

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https://www.willswing.com/a-brief-history-of-hang-gliding-paragliding-and-wills-wing/

http://www.bautek.com/index.php/astir-en.html

http://www.turfhouse.com/acatalog/Vintage_gliders.html

http://www.apcoaviation.com/products.asp?section=paramotors&product=thrust%20V

http://www.performance-composites.com/carbonfibre/mechanicalproperties_2.asp

http://www.avianonline.co.uk/fly-15-p-1827.html

https://www.aerosociety.com/news/video-and-audio-archive-handley-page-named-lecture-2017/

https://www.aerosociety.com/news/video-and-audio-archive-handley-page-named-lecture-2017/

https://newatlas.com/passenger-drone-flying-taxi/51539/

http://www.pmaviation.co.uk/gt450.html

Documents

Design & Prototype an Ultra-Portable Hang Glider Dissertation.pdf · 2019. 5. 20. · Design & Prototype an Ultra-Portable Hang Glider Final Report p3/50 Jeremy Soper ’18/05/19