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9-16-1968
Cantilevered Chairs
William Alvut
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Recommended Citation
CANTI
LEVERED
CHAIRS
by
Wi 1 1
iam
Al
vutCand idate
For
the
Master
ofF
ine
Arts
In
the
College
ofFine Arts
of
the
Rochester
Institute
ofTechnology
September
16,
1 968
TABLE
OF
CONTENTS
Page
Introduction
1
Experimentation
&
Research
2
Design
Interpretation
5
Seating
Solution
7
Conclusions
13
Future
Development
15
Bibl
iography
16
Illustrative
Material
Oak
Chair
-In
Development
Oak
Chair
-Side
View
Oak
Chair
-Front
View
Oak
Cha
i
r -Back
V iew
Oak
Cha
i
r -Deta i
1
sMetal
Chair
-Front
View
Metal
Chair
-Back View
Metal
Chai
r -Detai
Is
A
Comparison
SI
ide
I 1 1
ustrations
INTRODUCTION
The
practice oflaminating
wood,
whichhas
been
known
sincethe
15th
century
B.C.,
is
currently
animportant
processin
modernindus
try
.By
laminating,
an assembled piece of wood canbe
puttogether
which
has
strength and shape characteristicsthat
the
originalmaterial
did
nothave.
A
typical
example ofthis
processis
a roofthat
is
supportedby
laminated
archesbonded
together
with waterres
i
stant
glue.My
interest
in
this
industrial
processled
meto
my
thesis
"Laminated
Cantilevered
Chairs".
The
choice,
incorporating
a cantileveridea,
is
not a newidea.
Man
has,
through
the
centuries,
observed and used cantileveredobjects.
In
certainfortunate
areas,
primitive man made use of aso called
"natural
stonebridge".
Arch
-like
in
form,
but
actually
cantilever
in
stress,
these
magnificant
structureshave
been
thousands
of yearsin
formation.
The
technique
has
been
usedto
accent architecture such as
Frank
Lloyd
Wright's
work andthe
Barcellona
cantilever chair.The
election of cantilever as a specificdesign
problem waschosen
to
force
myselfto
approach atopic
which couldbe
andhas
Exper imentat ion
andResearch
The
subject oflaminated
woodlends
itself
to
the
use ofcurved structures which allows
flexible design.
I
decided
to
useblack
iron
pipeto
build
delineators
because
the
seating
arange-ment can
be
tested
andthe
possiblelaminated
shape canbe
represented
full
scale.I
decided
to
work with ahammock
orsling
type
ofseating
arrangement
first,
to
seeif
any
development
wouldbe
practical.A
test
structure wasbuilt
of 1"black
iron
pipe,
whichI
felt
would allow some
degree
offlexible
adjustments.I
t
looks
1
i ke
th
is
.A
sliding
adjustment onthe
upper pipe wasbuilt,
working
on
the
principle ofthe
sliding
part of a pipe clamp.PIPE
3/8"
STEEL
PLATE
HINGE
SLING
SUPPORT
The
two
front
points ofthis
seat were placedapproximately
2k"
apart and a 16"
height
from
the
floor.
The
suspension pointswere
held
by
1/8"steel cable.
First
I
tried
a sewnhem
in
some canvas.
It
held
the
sling,
however
the
cablehad
acutting
effect on
the
back
ofthe
legs.
1/8"
CABLE
I
found
I
could avoid alot
ofthis
cutting
feeling by lapping
the
hem
severaltimes
as shown andusing
grommets onthe
corners.Through
the
grommetsI
still usedthe
1/8" cables.Using
pipeI
devised
this
successful method of suspensionPIPE
8LEEVE
BOLT
Once
I
solvedthe
suspension and was ableto
adjustthese
points,
I
found
areasonably
comfortable seat.I
did
find
that
the
first
test
chair was nottoo
stable,
from
the
standpoint oflateral
movement,
andthat
it
didn't
have
the
rear point
far
enoughback
ofthe
center ofgravity
whilesitting
i
nthe
chai
r .I
kept
in
mindthe
lateral
instability
andknew
that
the
rearwould
have
to
be
wider orheavier.
The
re-designing
led
to
the
result of
building
anotherblack
iron
pipe chair.I
developed
another model and
began
to
build
the
next prototype.I
felt
I
could use smaller pipe since
this
design
would usetwo
pipes onthe
back
curveto
increase
the
strength.The
pipe wasbent
coldusing
a system oftwo
pinsin
abench
top.
PINS
BENCH
(TOP
VIEW)
The
3
A" pipe worked alot
easierthan
the
1" pipe.I
wasable
to
bend
it
myself,
whilethe
1" pipe requiredtwo
people.This
design
is
cantileverto
adegree.
To
develop
a purerdesign,
using
the
cantileverdesign,
I
bent
and welded another possibledesign.
This
design
placed much stress onthe
lower
parts ofthis
cantileverdesign.
Pes
ign
I
nterpretation
The
cantileverdesign
relies
on alaw
of physicsusing
afulcrum
and
lever
arrangement.Typically
a cantileveris
constructedto
provide an unsupported overhang.
To
supportthis
overhang
an equalanchoring
force
is
neededto
controlthe
weight.AN
EQUAL
FORCE
CANTILEVER
FORCE
^Cr
FULCRUM
The
design
canbe
expressed asT
4'
CANTILEVER
FORCE
FULCRUM
6
._
AN
EQUAL
FORCE
I
figured
the
maximum weight of a male atapproximately
250
lbs
plus
50
lbs.
for
the
initial
drop
stressequaling
atotal
of300
lbs
I
checkedthe
text
Practical
Carpentry
(P.
65),
andfound
alive
load
of360
lbs.
couldbe
handled
by
a 2" x k" cross sectionfor
the
5
foot
length
ofthe
cantileverlaminate.
This
was adetermin
ing
factor
in
relationto
the
cross-section ofthe
upper cantileverbends.
This
allows strengthfor
a300
lb.
manto
sit withlittle
def 1
ection
.Figuring
the
leverage
atthe
stress point#B
at about3iA
feet
to
1
foot
an approximate900
lbs.
to
1000
lbs.
wouldbe
applied.
The
lower
supporting
bend,
whichhas
to
handle
the
stress,
worked outto
the
equivalent of a cross-section of a2"
x 6"
to
handle
1000-1200
lbs.
ofleverage.
1
selected oak asthe
woodbecause
ofits
strength andits
elastic characteristic of
being
ableto
allow adegree
oftwisting
and
bending
before
the
grainfractures.
A
cantileverdesign,
suchas
the
oneI
finally
selected,
needs a certain amount offlexibil
i
ty
to
withstand notonly
the
sitting
of aperson,
but
the
initial
drop
weight.
The
thickness,
orcross-section,
can notbe
committedto
aesthetic
needs,
but
mustbe
emphasized enoughto
meetthe
material requirements.
Another
experiment wasto
test
the
3A" pipe prototypeto
seeif
the
design
was practicalfrom
the
standpoint oftipping
overbackwards.
I
jigged
up
the
prototype and stoodin
the
seat.
Lean
roll.
It
does
rollback,
but
it
wouldtake
a greatdeal
of effortto
tip
i
t
over.FORCE
FULCRUM
With
these
factors
in
mind,
I
proceededto
develop
the
full
elevations.
I
knew
the
probable cross sectionsneeded,
andduring
the
drawing
realizedthe
distribution
ofthe
weight.This
brought
about
the
functional
need of a solidbase
curvefrom
sideto
side.FULCRUM
-(centerof
gravity)
Seat
inq
Sol
ution
The
structure ofthe
chair was now solvent andthe
final
earlier
prototype,
I
felt
that
a purehammock
type
ofsling,
whilevery
comfortable,
in
my
opinionleft
something
to
be
desired.
The
reason
is
that
when youfirst
sitin
the
chair and when you get out ofthe
chair,
the
center ofgravity
ofthe
body,
forces
the
sling
to
make you sitin
a pocket.This
lower
seating
areatends
to
tilt
down
and makeit
difficult
to
get out ofthe
sling.AREA
The
concept of cantilever andsling
seat provided a problem ofhow
to
design
the
cantilever concept andthe
sling
conceptinto
oneworking
design.
The
sling
seatdemanded
specific needs:Lateral
strength
to
pullthe
two
front
suspension pointsapart,
athird
suspension point
high
enoughto
makethe
body
andhead
comfortable andthe
relative position ofthese
three
pointsto
the
floor
andhuman
body
.I
then
considered atwo
piece sling.The
lower
seatto
be
attachedfrom
sideto
side.This
provedto
be
a practicalapproach,
sinceit
does
away
withthe
pocket effect.The
back
restsling,
when setup
within conventionaldimensions,
did
not seemto
work out well.I
cut a slotthrough
the
stretcher and ranthe
back
restfrom
this
pointto
the
top
ofthe
barrel
stavedsection.
This
arrangethe
head,
from
the
neckup,
into
adown
andforward
unnatural positionA
one piecesling
could eliminatethis
feeling,
but
provided apocket effect
in
the
lower
seat.I
decided
to
take
the
best
of eachand
incorporate
the
ideas.
I
used 22" cottonduck
canvas as afoundation
and sewedtwo
pieces
together
to
incorporate
the
two
sling
technique.
The
pattern was as
follows.
At
pointA
onthe
drawing
the
backrest
material wasbrought
under
the
cross siing
piece.The
front
edge washemmed
over andthe
backrest
piece sewedin
between.
CROSS
SLING
2
This
canvasfoundation
wastried
onthe
chair andthis
dove
tailing
ofthe
two
slinging
methods provedto
be
a successful seat.The
sling
was removedto
be
covered withblack
vinyl, j"foam
rubber was
bonded
to
the
canvas with contact cement.It
was noticedthat
the
brushing
ofthe
cement onthe
foam
tended
to
stretchit.
I
taped
the
sewnhems
with a 2" mastictape
to
smooth overthe
sewnarea
SEWN
MASTIC
TAPE
The
foam
was cutzj"
smaller
to
allow a margin andthe
foam
andcanvas were
bonded
together.
1/2"
FOAM
AREA
B
HEM
MASTIC
TAPE
After
the
foam
and canvas werebonded
together
Area
B
was11
were pinched
together.
This
made a slight curvature onthe
edge asshown
below.
-nGLUED
AREA
B
X
_
1/2"
FOAM
HEM
MASTIC
TAPE
The
covering
wastraced,
cut about 1/8" small and sewn pillowcase style
(inside
out).r
SEWN
The
flap
wasthen
folded
andtaped
withthe
2" mastictape
to
the
eventualback
ofthe
backrest
sling
cover.T
SEWN
MASTIC TAPE
The
use ofthe
mastictape
guaranteedthat
the
inside
flap
wouldstay
onthe
back
ofthe
edge whenthe
cover was slipped overthe
foam
The
lower
seat wasfastened
to
the
chair as shownbelow:
3/8"
X
3/8"CLEAT
CANTILEVER
LAMINATES
Before
the
sling
fastening
cleats wereplaced,
the
two
cantilevered
laminates
were compressedtowards
eachother,
sothat
they
would
naturally
expand and pullthe
sling
sideto
side when no one wass
i
tt
ing
in
the
chai
r .The
backrest
part ofthe
sling
was securedby
first
cutting
the
top
ofthe
chairto
be
in
sympathy
withthe
angle ofthe
backrest.
A
cleat was madefor
the
barrel
staved section and rabbets cutinto
the
sidelaminated
areas.Cleats
were alsofitted
into
these
rabbeted13
CONCLUSIONS
Aesthetic
standardsvary
from
personto
person.However,
the
quality
of appearanceis
of vital concern and cannotbe
overlooked.To
have
a cantilever chairthat
is
functional
is
fine,
but
if
it
is
to
be
of valuethe
appearance mustblend
together.
The
Oak
Cant
i 1
everCha i
rThe
oak versionhas
blending
of1
ines.
The
main andbarrel
staved
laminates
follow
a curved plane withthe
cantileverlaminate.
The
two
curves aretied
together
visually
by
the
curving
andmeeting
at
the
top,
which establishes unity.At
the
top
the
sling
head
rest alsoties
in
atthat
point andcurves
slightly
to
the
seat.Looking
atthe
front
or rear ofthe
chair
the
profileis
tapered
to
the
top.
This
tapering
visually
makes
the
base
appearto
be
stable andthe
curving
plane gives acertain amount of grace.
Two
points ofthe
design
cause some questionsto
some andaccep
tance
to
others.The
first
is
the
curving
ofthe
back,
which givesthe
impression
to
many
that
the
chair might rollbackwards.
It
will,
with alittle
effort while not
seated,
but
will nottip
when seated.The
secondis
the
impression
ofthe
two
cantilever memberssupporting
the
seat.They
tend
to
make people askif
it
is
safe orstrong
enoughto
sitin.
The
sling
andthe
stretcherhidden
below
the seat are
deceiving.
The
seathas
held
260
lbs.
andI
feel
has
aA
The
proportions ofthe
chair weredemanded
in
partby
the
needsfor
the
function
ofthe
seat.I
feel
that,
looking
atthe
front,
the
base
shouldhave
been
2"or 3" wider.
The
greater widthis
neededfor
visual proportionfrom
that
viewpoint.The
Meta
1
Cant
i 1
everCha i
rThis
version was re-designed afterit
had
fulfilled
its
role-to
test
the
design
ofthe
oak chair.The
use of pipe allows more strengthin
relationto
the
cross-section of
any
structural member.This
apparentlightness
ofthe
cross-section gives a
piece,
andin
particularthe
metalversion,
acertain amount of grace.
This
accentsthe
spaceit
contains.It
still performs as a chair
but
allows an openlight
appearance asopposed
to
the
oak version.One
point which seemsto
causeinterest
in
the
metal versionis
the
opennessbetween
the
seat andback
seat.Traditionally
these
are
usually
fastened
together.
This
feature
allows an elastictorque
to
the
back
rest.Another
point whichhas
causedthe
same questionto
be
asked aswith
the
oakversion,
"Is
it
safe enoughto
sit in?"The
lower
joint
that
holds
the
seatis
a weldedjoint.
The
electrode usedto
arc weldthe
miter was anE
6013.
This
rod when usedin
a weld will standup
to
60,000
lbs.
oftencil
strength per squareinch.
Each
joint
does
not15
Futu
reDevelopment
Due
to
my
studiesI
planto
gofurther
withthe
cantileverchair.
I
have
severaldesigns
in
mind.1.
A
wood version of one similarto
the
metaldesign.
2.
A
woodrocking
version of one similarto
the
metaldesign.
3.
A
metalrocking
chair similarto
the
metaldesign.
k.
A
wood version ofthe
oak chair with arm rests.My
evaluation ofmy
work seemsin
order whenconsidering
the
future
.I
reflect atthis
writing,
that
the
design,
I
seemto
favor
asbetter,
is
the
metal chair.I
feel
this
is
true
because
it
wasthe
fourth
cantileverdesign
ofmy
thesis.
I
usedthe
pipefor
the
second and
last
chair.All
were relatedin
design
-the
big
advantagewas
the
media.Metal
canbe
bent,
changed and welded.It
allows moreliberal
designs
to
be
created.Metal
however
lacks
the
warmth andbeauty
of wood.This
is
why
I
wantto
gofurther
withthe
designs
I
B
i bl
iog
raphy
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Louise
Ade,
The
Comp
1
eteGu ide
to
Furn
i
ture
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1
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York:
Charles
Scribner's
Sons,
1959
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Erwin
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The
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New
York:
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Macmillan
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1959
Earl,
Arthur
W.
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ndust
ry
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1
oomi
ng
ton
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McKnight
andMcKnight
Publishing
Company,
1 960
Kauf
mann,Edgar,
Jr.,
What
is
Modern
Design?
New
York:
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Museum
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Art,
1950.
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Ralph
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ndust
ria I
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