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Rochester Institute of Technology

RIT Scholar Works

Theses

Thesis/Dissertation Collections

9-16-1968

Cantilevered Chairs

William Alvut

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Recommended Citation

(2)

CANTI

LEVERED

CHAIRS

by

Wi 1 1

iam

Al

vut

Cand idate

For

the

Master

of

F

ine

Arts

In

the

College

of

Fine Arts

of

the

Rochester

Institute

of

Technology

September

16,

1 968

(3)

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

s

Metal

Chair

-

Front

View

Metal

Chair

-

Back View

Metal

Chai

r -

Detai

Is

A

Comparison

SI

ide

I 1 1

ustrat

ions

(4)

INTRODUCTION

The

practice of

laminating

wood,

which

has

been

known

since

the

15th

century

B.C.,

is

currently

an

important

process

in

modern

indus

try

.

By

laminating,

an assembled piece of wood can

be

put

together

which

has

strength and shape characteristics

that

the

original

material

did

not

have.

A

typical

example of

this

process

is

a roof

that

is

supported

by

laminated

arches

bonded

together

with water

res

i

s

tant

glue.

My

interest

in

this

industrial

process

led

me

to

my

thesis

"Laminated

Cantilevered

Chairs".

The

choice,

incorporating

a cantilever

idea,

is

not a new

idea.

Man

has,

through

the

centuries,

observed and used cantilevered

objects.

In

certain

fortunate

areas,

primitive man made use of a

so called

"natural

stone

bridge".

Arch

-

like

in

form,

but

actually

cantilever

in

stress,

these

magnif

icant

structures

have

been

thousands

of years

in

formation.

The

technique

has

been

used

to

accent architecture such as

Frank

Lloyd

Wright's

work and

the

Barcellona

cantilever chair.

The

election of cantilever as a specific

design

problem was

chosen

to

force

myself

to

approach a

topic

which could

be

and

has

(5)

Exper imentat ion

and

Research

The

subject of

laminated

wood

lends

itself

to

the

use of

curved structures which allows

flexible design.

I

decided

to

use

black

iron

pipe

to

build

delineators

because

the

seating

ar

ange-ment can

be

tested

and

the

possible

laminated

shape can

be

represented

full

scale.

I

decided

to

work with a

hammock

or

sling

type

of

seating

arrangement

first,

to

see

if

any

development

would

be

practical.

A

test

structure was

built

of 1"

black

iron

pipe,

which

I

felt

would allow some

degree

of

flexible

adjustments.

I

t

looks

1

i ke

th

is

.

A

sliding

adjustment on

the

upper pipe was

built,

working

on

the

principle of

the

sliding

part of a pipe clamp.

PIPE

3/8"

STEEL

PLATE

HINGE

SLING

SUPPORT

(6)

The

two

front

points of

this

seat were placed

approximately

2k"

apart and a 16"

height

from

the

floor.

The

suspension points

were

held

by

1/8"

steel cable.

First

I

tried

a sewn

hem

in

some canvas.

It

held

the

sling,

however

the

cable

had

a

cutting

effect on

the

back

of

the

legs.

1/8"

CABLE

I

found

I

could avoid a

lot

of

this

cutting

feeling by lapping

the

hem

several

times

as shown and

using

grommets on

the

corners.

Through

the

grommets

I

still used

the

1/8" cables.
(7)

Using

pipe

I

devised

this

successful method of suspension

PIPE

8LEEVE

BOLT

Once

I

solved

the

suspension and was able

to

adjust

these

points,

I

found

a

reasonably

comfortable seat.

I

did

find

that

the

first

test

chair was not

too

stable,

from

the

standpoint of

lateral

movement,

and

that

it

didn't

have

the

rear point

far

enough

back

of

the

center of

gravity

while

sitting

i

n

the

cha

i

r .

I

kept

in

mind

the

lateral

instability

and

knew

that

the

rear

would

have

to

be

wider or

heavier.

The

re-designing

led

to

the

result of

building

another

black

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 use

two

pipes on

the

back

curve

to

increase

the

strength.

The

pipe was

bent

cold

using

a system of

two

pins

in

a

bench

top.

PINS

BENCH

(TOP

VIEW)

(8)

The

3

A" pipe worked a

lot

easier

than

the

1" pipe.

I

was

able

to

bend

it

myself,

while

the

1" pipe required

two

people.

This

design

is

cantilever

to

a

degree.

To

develop

a purer

design,

using

the

cantilever

design,

I

bent

and welded another possible

design.

This

design

placed much stress on

the

lower

parts of

this

cantilever

design.

Pes

ign

I

nterpretat

ion

The

cantilever

design

rel

ies

on a

law

of physics

using

a

fulcrum

and

lever

arrangement.

Typically

a cantilever

is

constructed

to

pro

vide an unsupported overhang.

To

support

this

overhang

an equal

anchoring

force

is

needed

to

control

the

weight.

AN

EQUAL

FORCE

CANTILEVER

FORCE

^Cr

FULCRUM

The

design

can

be

expressed as

T

4'

CANTILEVER

FORCE

FULCRUM

6

._

AN

EQUAL

FORCE

(9)

I

figured

the

maximum weight of a male at

approximately

250

lbs

plus

50

lbs.

for

the

initial

drop

stress

equaling

a

total

of

300

lbs

I

checked

the

text

Practical

Carpentry

(P.

65),

and

found

a

live

load

of

360

lbs.

could

be

handled

by

a 2" x k" cross section

for

the

5

foot

length

of

the

cantilever

laminate.

This

was a

determin

ing

factor

in

relation

to

the

cross-section of

the

upper cantilever

bends.

This

allows strength

for

a

300

lb.

man

to

sit with

little

def 1

ect

ion

.

Figuring

the

leverage

at

the

stress point

#B

at about

3iA

feet

to

1

foot

an approximate

900

lbs.

to

1000

lbs.

would

be

applied.

The

lower

supporting

bend,

which

has

to

handle

the

stress,

worked out

to

the

equivalent of a cross-section of a

2"

x 6"

to

handle

1000-1200

lbs.

of

leverage.

1

selected oak as

the

wood

because

of

its

strength and

its

elastic characteristic of

being

able

to

allow a

degree

of

twisting

and

bending

before

the

grain

fractures.

A

cantilever

design,

such

as

the

one

I

finally

selected,

needs a certain amount of

flexibil

i

ty

to

withstand not

only

the

sitting

of a

person,

but

the

initial

drop

weight.

The

thickness,

or

cross-section,

can not

be

committed

to

aesthetic

needs,

but

must

be

emphasized enough

to

meet

the

material requirements.

Another

experiment was

to

test

the

3A" pipe prototype

to

see

if

the

design

was practical

from

the

standpoint of

tipping

over

backwards.

I

jigged

up

the

prototype and stood

in

the

seat.

Lean

(10)

roll.

It

does

roll

back,

but

it

would

take

a great

deal

of effort

to

tip

i

t

over.

FORCE

FULCRUM

With

these

factors

in

mind,

I

proceeded

to

develop

the

full

elevations.

I

knew

the

probable cross sections

needed,

and

during

the

drawing

realized

the

distribution

of

the

weight.

This

brought

about

the

functional

need of a solid

base

curve

from

side

to

side.

FULCRUM

-(center

of

gravity)

Seat

inq

Sol

ut

ion

The

structure of

the

chair was now solvent and

the

final

(11)

earlier

prototype,

I

felt

that

a pure

hammock

type

of

sling,

while

very

comfortable,

in

my

opinion

left

something

to

be

desired.

The

reason

is

that

when you

first

sit

in

the

chair and when you get out of

the

chair,

the

center of

gravity

of

the

body,

forces

the

sling

to

make you sit

in

a pocket.

This

lower

seating

area

tends

to

tilt

down

and make

it

difficult

to

get out of

the

sling.

POCKET

AREA

The

concept of cantilever and

sling

seat provided a problem of

how

to

design

the

cantilever concept and

the

sling

concept

into

one

working

design.

The

sling

seat

demanded

specific needs:

Lateral

strength

to

pull

the

two

front

suspension points

apart,

a

third

suspension point

high

enough

to

make

the

body

and

head

comfortable and

the

relative position of

these

three

points

to

the

floor

and

human

body

.

I

then

considered a

two

piece sling.

The

lower

seat

to

be

attached

from

side

to

side.

This

proved

to

be

a practical

approach,

since

it

does

away

with

the

pocket effect.

The

back

rest

sling,

when set

up

within conventional

dimensions,

did

not seem

to

work out well.

I

cut a slot

through

the

stretcher and ran

the

back

rest

from

this

point

to

the

top

of

the

barrel

staved

section.

This

arrange
(12)

the

head,

from

the

neck

up,

into

a

down

and

forward

unnatural position

A

one piece

sling

could eliminate

this

feeling,

but

provided a

pocket effect

in

the

lower

seat.

I

decided

to

take

the

best

of each

and

incorporate

the

ideas.

I

used 22" cotton

duck

canvas as a

foundation

and sewed

two

pieces

together

to

incorporate

the

two

sling

technique.

The

pattern was as

follows.

At

point

A

on

the

drawing

the

backrest

material was

brought

under

the

cross si

ing

piece.

The

front

edge was

hemmed

over and

the

backrest

piece sewed

in

between.

CROSS

SLING

2

(13)

This

canvas

foundation

was

tried

on

the

chair and

this

dove

tailing

of

the

two

slinging

methods proved

to

be

a successful seat.

The

sling

was removed

to

be

covered with

black

vinyl, j"

foam

rubber was

bonded

to

the

canvas with contact cement.

It

was noticed

that

the

brushing

of

the

cement on

the

foam

tended

to

stretch

it.

I

taped

the

sewn

hems

with a 2" mastic

tape

to

smooth over

the

sewn

area

SEWN

MASTIC

TAPE

The

foam

was cut

zj"

smaller

to

allow a margin and

the

foam

and

canvas were

bonded

together.

1/2"

FOAM

AREA

B

HEM

MASTIC

TAPE

After

the

foam

and canvas were

bonded

together

Area

B

was
(14)

11

were pinched

together.

This

made a slight curvature on

the

edge as

shown

below.

-nGLUED

AREA

B

X

_

1/2"

FOAM

HEM

MASTIC

TAPE

The

covering

was

traced,

cut about 1/8" small and sewn pillow

case style

(inside

out).

r

SEWN

The

flap

was

then

folded

and

taped

with

the

2" mastic

tape

to

the

eventual

back

of

the

backrest

sling

cover.

T

SEWN

MASTIC TAPE

The

use of

the

mastic

tape

guaranteed

that

the

inside

flap

would

stay

on

the

back

of

the

edge when

the

cover was slipped over

the

foam

(15)

The

lower

seat was

fastened

to

the

chair as shown

below:

3/8"

X

3/8"

CLEAT

CANTILEVER

LAMINATES

Before

the

sling

fastening

cleats were

placed,

the

two

cantilevered

laminates

were compressed

towards

each

other,

so

that

they

would

naturally

expand and pull

the

sling

side

to

side when no one was

s

i

tt

ing

in

the

cha

i

r .

The

backrest

part of

the

sling

was secured

by

first

cutting

the

top

of

the

chair

to

be

in

sympathy

with

the

angle of

the

backrest.

A

cleat was made

for

the

barrel

staved section and rabbets cut

into

the

side

laminated

areas.

Cleats

were also

fitted

into

these

rabbeted
(16)

13

CONCLUSIONS

Aesthetic

standards

vary

from

person

to

person.

However,

the

quality

of appearance

is

of vital concern and cannot

be

overlooked.

To

have

a cantilever chair

that

is

functional

is

fine,

but

if

it

is

to

be

of value

the

appearance must

blend

together.

The

Oak

Cant

i 1

ever

Cha i

r

The

oak version

has

blending

of

1

ines.

The

main and

barrel

staved

laminates

follow

a curved plane with

the

cantilever

laminate.

The

two

curves are

tied

together

visually

by

the

curving

and

meeting

at

the

top,

which establishes unity.

At

the

top

the

sling

head

rest also

ties

in

at

that

point and

curves

slightly

to

the

seat.

Looking

at

the

front

or rear of

the

chair

the

profile

is

tapered

to

the

top.

This

tapering

visually

makes

the

base

appear

to

be

stable and

the

curving

plane gives a

certain amount of grace.

Two

points of

the

design

cause some questions

to

some and

accep

tance

to

others.

The

first

is

the

curving

of

the

back,

which gives

the

impression

to

many

that

the

chair might roll

backwards.

It

will,

with a

little

effort while not

seated,

but

will not

tip

when seated.

The

second

is

the

impression

of

the

two

cantilever members

supporting

the

seat.

They

tend

to

make people ask

if

it

is

safe or

strong

enough

to

sit

in.

The

sling

and

the

stretcher

hidden

below

the seat are

deceiving.

The

seat

has

held

260

lbs.

and

I

feel

has

a
(17)

A

The

proportions of

the

chair were

demanded

in

part

by

the

needs

for

the

function

of

the

seat.

I

feel

that,

looking

at

the

front,

the

base

should

have

been

2"

or 3" wider.

The

greater width

is

needed

for

visual proportion

from

that

viewpoint.

The

Meta

1

Cant

i 1

ever

Cha i

r

This

version was re-designed after

it

had

fulfilled

its

role

-to

test

the

design

of

the

oak chair.

The

use of pipe allows more strength

in

relation

to

the

cross-section of

any

structural member.

This

apparent

lightness

of

the

cross-section gives a

piece,

and

in

particular

the

metal

version,

a

certain amount of grace.

This

accents

the

space

it

contains.

It

still performs as a chair

but

allows an open

light

appearance as

opposed

to

the

oak version.

One

point which seems

to

cause

interest

in

the

metal version

is

the

openness

between

the

seat and

back

seat.

Traditionally

these

are

usually

fastened

together.

This

feature

allows an elastic

torque

to

the

back

rest.

Another

point which

has

caused

the

same question

to

be

asked as

with

the

oak

version,

"Is

it

safe enough

to

sit in?"

The

lower

joint

that

holds

the

seat

is

a welded

joint.

The

electrode used

to

arc weld

the

miter was an

E

6013.

This

rod when used

in

a weld will stand

up

to

60,000

lbs.

of

tencil

strength per square

inch.

Each

joint

does

not
(18)

15

Futu

re

Development

Due

to

my

studies

I

plan

to

go

further

with

the

cantilever

chair.

I

have

several

designs

in

mind.

1.

A

wood version of one similar

to

the

metal

design.

2.

A

wood

rocking

version of one similar

to

the

metal

design.

3.

A

metal

rocking

chair similar

to

the

metal

design.

k.

A

wood version of

the

oak chair with arm rests.

My

evaluation of

my

work seems

in

order when

considering

the

future

.

I

reflect at

this

writing,

that

the

design,

I

seem

to

favor

as

better,

is

the

metal chair.

I

feel

this

is

true

because

it

was

the

fourth

cantilever

design

of

my

thesis.

I

used

the

pipe

for

the

second and

last

chair.

All

were related

in

design

-the

big

advantage

was

the

media.

Metal

can

be

bent,

changed and welded.

It

allows more

liberal

designs

to

be

created.

Metal

however

lacks

the

warmth and

beauty

of wood.

This

is

why

I

want

to

go

further

with

the

designs

I

(19)

B

i bl

iog

raphy

:

Boger,

Louise

Ade,

The

Comp

1

ete

Gu ide

to

Furn

i

ture

Sty

1

es.

New

York:

Charles

Scribner's

Sons,

1959

Christensen,

Erwin

0.,

The

Index

of

American

Design.

New

York:

The

Macmillan

Company,

1959

Earl,

Arthur

W.

,

Experiments

with

Materials

and

Products

of

I

ndus

t

ry

.

B

1

oom

i

ng

ton

,

Illinois:

McKnight

and

McKnight

Publishing

Company,

1 960

Kauf

mann,

Edgar,

Jr.,

What

is

Modern

Design?

New

York:

The

Museum

of

Modern

Art,

1950.

Knoblaugh,

Ralph

R.,

Modelmakinq

for

I

ndus

t

r

ia I

Pes

ion.

New

York:

McGraw-Hill

Book

Company,

Incorporated,

1958

Knoll

Index

of

Contemporary

Design.

New

York:

Knoll

Associates

I

ncorpora

ted

,

1

9^+3

Mix,

Floyd

M.,

Practical

Carpentry.

Homewood

,

111.:

The

Goodheart-Wi

1 1

cox

Co.,

Inc.,

1

963

Rottger,

Ernst,

Creative

Wood

Design.

New

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Reinhold

Publishing

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I96I

Shortley,

George

and

Williams,

Dudley,

Elements

of

Physics.

Theses Thesis/Dissertation Collections

References

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