20378-product design an activity based case study of sleeping bags

8/12/2019 20378-Product Design an Activity Based Case Study of Sleeping Bags

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Acknowledgments

The editors gratefully acknowledge information supplied by Polywarm Products Ltd and the

considerable assistance and advice offered by David Houston of Daimor Sleeping Bags.

Cover picture courtesy of Daimor Sleeping Bags.

I l f i l l R l l U



Alan Stancliffe was sponsored by the British Plastics Federation The Institute of Materials

British Plastics Training Association and the Polymer and Rubber Association.

The material was produced as part of the polymer industry education project at the

Chemical Industry Education Centre

Department of Chemistry

University of York

Heslington

YorkY015DD

Telephone (01904) 432523

ditors

Judy Jones

Alan Stan cliffe

With contributions from Gill Thomas - CIEC information officer

© Held by the University of York

Published 1995

ISBN: 1853427055

The copyright holders waive the copyright on the material which follows to the extent that

teachers may reproduce this material for use with their pupils in the establishment for which

the material was purchased, but for all other purposes permission to reproduce any of this

material in any form must be obtained from the University of York. The material may not be

duplicated for lending, hire or sale.

ii



ONT NTS

Foreword

Resources

Product design and development

Activities 1, 2 and 3

Analysis of general functional requirements for sleeping bags

Materials selection in product design

Development of a new product

Development of a new sleeping bag design

Factors influencing the development of a new product

Materials used in sleeping bags

Environmental extension activity

The manufacture of sleeping bags

Student sheets for activities 1-3

Information sheet for activity 1

Information sheets (a) to (g) for activity 3

OHP1 a) Factors influencing the development of a new product

b) New product path

a) The construction of sleeping bags

b) Stitch constructions used with synthetic fillings

0HP2

iii

Page

V

V

12

2

3

3

4

4

5

5

AI-A3.2



oreword

This package has been produced as a result of requests from design and

technology teachers. They asked for case study resources which demonstrate

the processes involved in industrial product design and selection of materials

for manufacture. It consists of a teachers' booklet and separate student work

sheets.

The package is intended to provide background information for use by

teachers and 14-16 year old students involved with design and technology

courses which contain elements of product design. It could also be made

suitable for younger students and post sixteen (A-level, GNVQ students by

modifying the level of expected outcomes in the suggested activities.

Students carry out a critical investigation of the design and manufacture of

sleeping bags as a product analysis exercise. This will help students to

develop technological and scientific skills and understanding by exploring the

properties of fillings, cover materials and processes used in the design andmanufacture of sleeping bags.

The teaching notes deal with the different stages of market research and

product design in the sleeping bag industry, and with the selection of

appropriate materials and manufacturing processes. They also offer further

guidance on classroom management of the student activities and

investigations.

Separate student copy master sheets (AI-A3.2) are provided which contain

background information and suggestions for analysis and problem solving

activities. Additional information for activities 1 and 3 (yellow sheets) is also

appropriate for product analysis exercises which can be devised by the teacherto suit particular circumstances.

A second unit is available in the Making Use of Science and Technology

series, also published by the Chemical Industry Education Centre,which

contains scientific investigations based on the construction and properties of

materials of sleeping bags.

iv



Resources

Samples of materials for testing can be obtained from

Tor Outdoor Pursuits

42 Widnes Road

Widnes

WA86AL

Tel:01514242225

This company will sell small quantities of fabrics and fillings.

At the time of printing typical prices were:

Fillings

Hollofil insulation (DacronFF2H) width 150cm

170g £3~~0per metre

240g £4.5b per metre.

Quilted insulation width 150cm

80g £3.80 per metre

150g £4.40 per metre

Duck down £9.50 per 100g pack

Outer cover fabrics

Nevetex 110 polycotton

Width 150cm

£4.20 per metre

200 Nylon plain fabric

Width 150cm

£3.20 per metre

Pertex 4 woven microfibre fabricWidth 163cm

£4.50 per metre

Tor Outdoor Pursuits are happy to receive enquiries about their products, but ask that

a stamped addressed envelope be included for replies.

v



Teaching Notes

Activity 1

This is a group discussion exercise using the information on student sheet A 1o

consider the factors which might influence the sleeping bag manufacturer'schoice of material. An additional information sheet for activity gives the relative

costs of common materials.

Activity 2

This is an exercise based on the market research stage of the design and

development cycle and is supported by student sheets A 2.1 and A 2.2. OHPI can

be used in a class discussion to help students formulate a structure for their

investigations. This activity could be carried out with students working in small

groups and might include the following:

• a survey of existing stock kept by local retail outlets to determinecurrent popular conditions of use, fashion and colour trends

• a survey to compare current costs to the customer

• a survey of use and preferences within the school population

• development of a marketing strategy from the information obtained

Activity

A teacher-led class discussion based on information on information sheets (a) to

(g) for activity 3, and OHP2 forms an introduction to this activity. It is an analysis

and investigative exercise designed to illustrate the considerations which are

involved with materials selection. Ideally it should be done with students

working in small mixed ability groups. This creates opportunities for students to

support each other in an exercise that is quite complex.

Using the information provided in information sheets (a) to (g), students are

required to list the functional requirements which apply to sleeping bags. They

must compare these requirements with the general properties and

characteristics of cover and filling materials, and fabrication construction

techniques. Samples of different cover, lining and filling materials can be

examined under a microscope (8x and 20x magnification) to observe the

characteristics described in the text of the student sheet. Groups can then be

assigned one of the following working conditions and asked to produce a short

report on the suitability of combinations of materials and fabrication structures

for use in the design and manufacture of appropriate sleeping bags.

i) summer low level camping in the UK

ii) a Himalayan trekking expedition

iii) a polar expedition

Reports can be produced in a written format, poster illustrations, verbal and/or

video presentations, to cater for a range of ability levels. There is no definitive

answer and a variety of acceptable solutions may be produced by the students. As

a concluding exercise, each group can present its final report to the whole class,

and compare and evaluate the different solutions offered.

The following sections demonstrate how the activities relate to the real world of

design.

1



Background information

Analysis of general functional requirements for sleeping bags

Whilst many sleeping bags can be considered multi-functional, they are

generally designed for specific outdoor conditions such as winter camping,

mountaineering, summer walking expeditions or general travel. Therefore thefirst questions relating to functional requirements would normally be:

What is the primary use for the sleeping bag?

In which temperature range will the bag regularly be used?

In which other conditions will the bag commonly be used?

After considering these questions carefully a designer is in a position to look at

cover fabrics and filling materials for a particular sleeping bag. As with most

insulation, sleeping bags work by trapping and holding air as still as possible.

They use the body's heat to warm this air. The efficiency of a sleeping bag relates

to the amount of air it can trap; this is affected by the combination of filling

material, and the design and construction of the bag.


When designers are considering which materials to select for a particular

product they normally liaise with a materials expert who advises on the

development process. There are two fundamental concepts which are considered

in the selection of materials. These are:

• materials must have properties which allow the designer

to produce a required effect

• the choice of material will influence the manufacturing

methods and vice-versa

Designers are not normally experts in, but are familiar with, materials and

manufacturing processes. Most designers build up a number of personal

contacts with specialists in materials science, manufacturers of processing

equipment and mould makers, and draw on their experience while seeking

solutions to problems.

There have been considerable developments in new materials over the past few

years and these have found applications in almost every field of design and

manufacture. This has made the process of material selection more complex for

designers. When selecting materials for specific products the designer must

consider which ones offer the best balance of properties. It is unlikely that any

material will meet the specifications perfectly and the usual compromises are

between desired performance and cost. Some of the main factors to be taken into

account are listed in student sheet Al, and a class discussion on materials

selection can be centred around this.

2




Analytical studies of industrial management and business performance

structures have identified three kinds of cycle times. These are time-to-market

(i.e. design and development), production time, and delivery time (order

processing). The first stage is the design 'and development cycle (or lead time).

In the sleeping bag industry this usually takes from 1 to 3 months. A diagram(New Product Path) is given in student sheet A 2.1 which illustrates the various

stages in this process. Student sheets A 2.1 and A 2.2 and the following notes can

be used together to form the basis of a class discussion of the design cycle involved

in the development of a new sleeping bag product.

Development of a new sleeping bag design

Typical working stages in the development of a new sleeping bag design are:

a) A marketing strategy is developed by:

• identifying the customers who will buy the sleeping bag;

• identifying the type of image the product range will project.

b) The designer is briefed and produces several concept proposals for

consideration by the project managers.

c) The designer develops the proposals approved by the project managers.

d) The designer produces bag shape outlines and pictures of the product in

three dimensional coloured images, possibly using Computer Aided

Design (CAD).

e) A prototype bag is commissioned, and further development considered.

f) Prototypes are tested for performance and quality and assessed forconsumer acceptability. Any necessary modifications are then made.

g) Designs are produced for a range of sizes, shapes (rectangular/tapered

mummy), fittings and colours as required by the marketing brief.

h) Tooling is organised in preparation for final production.

The aspects which influence a new sleeping bag design can also be grouped into

factors leading to production and factors controlling production. A diagram

(Factors related to production) is given in student sheet A 2.2 to show this.

According to commercial research, production time is the key to profitability.

The research has shown that companies who have managed to reduce production

cycle time by 50 have improved their return on investment by about 10 .



nvironmental extension a£tivity

Synthetic fibres are now being produced from recycled materials. As an average

estimate, 35 recycled 2 litre PET (polyethylene terephthalate) bottles can provide

enough polyester fibre filling for 1 sleeping bag. An extension to a£tivity could

be to engage the students in a survey of existing sleeping bag products to

determine which ones use recycled materials and to suggest possible ways of

recycling old sleeping bags which have come to the end of their working life.

he manufacture of sleeping bags

Information sheets f and (g) outline the main stages of manufacturing a

sleeping bag and can be used as the basis of a class discussion. Note the labour

intensive nature of the processes involved.

5



tivity


Working in groups:

1. Discuss how the factors outlined below might influence a

manufacturer's choice of material for a sleeping bag.

2. Prepare a report of the major outcomes of your discussion to

present to the whole class.

When selecting materials for specific products the designer must consider

which one offers the best balance of properties. Some of the main factors to be

taken into account are:

• appropriateness for the manufacturing process and quantity

production (machining, moulding, extrusion, etc.)

• physical properties of the material (strength, hardness,

chemical resistance, etc.)

• material form (sheet, rod, strip, liquid, fibre, etc.)

• aesthetic considerations such as colour, texture, pattern

and shape

• environmental considerations such as weather resistance and

ease of recycling

• safety such as flammability and toxicity

• cost (there is an information sheet to help you) and availability

Note

When designers are considering which materials to select for a particularproduct they normally consult experts in materials whose advice will

influence the development process. Two of the main considerations are:

• The materials must have properties which allow the designer to

produce the required effect.

• The choice of material will influence the manufacturing

methods and vice-versa.

Student sheet Al



Information sheet for activity 1

Properties and costs of some commonly used sleeping bag materials

Cover fabrics

Material Properties mass Costperm2

(g/m2)

Performance Proof lightweight, waterproof, tear 00 £2.70

resistant

Matrix breathable, durable, waterproof 150 £8.50

Taslan similar to matrix but heavier duty 170 £8.00

and more robust

Tactel Milair lightweight, breathable, waterproof 125 £9.00

Ski-tex breathable, shower proof 130 £4.00

Pertex ultralight, draws away body 54 £2.80

moisture

Ripstop fabric soft, light, shower proof, can retain 68 £2.00

down

Polycotton breathable, windproof and shower 120 £1.80

proof

Nevetex 110 strong, windproof and shower proof 110 £2.80

200 Nylon plain I strong, tear resistant, not proofed 200 £2.00fabric

1 . . _

Filling materials

Material Properties mass Costperm2

(g/m2)

K2 Fleece fabric wind proof, low water absorbency, 250 £7.80

dries easily, easy to sew

Polar fabric soft, good insulator, easy to sew, 400 £3.80

machine washable

Thinsulate good insulator 100 £3.50

Hollofil soft, compressible, low water 170 £2.50

retention, very good insulator- • -.

Duck down £64 for800gxcellent insulator, compressible. 800g

needed

fora 4

seasonsleeping

bag



Activity 2


The development of a new sleeping bag design will be influenced by the

following factors:

• consumer requirements

• fashion and colour trends• demands of retailers and distributors

• society and environmental pressures

• properties of materials• technical aspects of manufacturing processes

Carry out a survey of existing sleeping bags in order to develop a marketing

strategy for a new product line. Your market research should investigate the

following:

• consumer attitudes and preferences

• an examination of existing cover styles, constructions

and fillings

• current costs to the consumer

Sleeping bag design involves the following two aspects:

• designs for the fabrication structure of the cover• selection of the most appropriate material for the filling

The design and development cycle (or lead time) for a new product in the

sleeping bag industry usually takes from 1 to 3 months. The diagram below

illustrates the various stages of this process.

CUSTOMER

MACH IN ISTS

PROTOTYPE

\MATER IALS

FABR ICAT ION

STRUCTURE

M AR KE T R ES EA RC H

\CONCEPT

DESIGN

/

New product path

Student sheet A 2.1



1

The aspects which influence a new sleeping bag design can

be grouped into factors leading to production and factors

controlling production. These are shown below.

Factors Related to Production

2

Student sheet A 2.2



Activity

Characteristics ofmateria1s used in sleeping bags

1. List the desired properties of materials used in the manufacture

of sleeping bags.

2. Examine the functional requirements for sleeping bags given on

student sheet A 3.2.

3. Compare these aspects with the general list of properties you have

identified. You could examine some of the available materialsunder a microscope using 8x and 20x magnification to help.

4. Use information sheets (a) - g to help you select appropriate

materials and construction techniques which will be suitable for

producing cost effective sleeping bags to be used under one of the

following conditions:

• summer low level camping in the UK

• a Himalayan trekking expedition

• a polar expedition

Note

Designers now use a range of natural and synthetic cover fabrics and filling

materials for sleeping bag design. Sleeping bags do not have to be thick to be

warm. It is the types of filling and stitching construction used in the cover

fabric which produce the required thermal insulation' properties. It is easy to

adjust the characteristics of sleeping bags to suit specific working conditions

using various permutations of cover fabric, filler material and stitching

construction.

Student sheet A 3.1



General functional requirements for sleeping bags

1.Weightand bulk:if sleeping bags are heavy or bulky, they

will be more difficult to carry, so a light weight material,

which retains its elasticity after compression, is an

advantage.

2. Toughness: sleeping bags should be capable of withstanding rough

treatment both in use and when folded for transit and storage (crush and

compression factors).

3. Comfort and shape: most sleeping bags are tapered, rectangular,

or mummy shaped. They should be flexible enough to fit the body form,

non-constrictive, and allow movement during sleep.

4. Insulation: sleeping bags should possess thermal insulationproperties which are related to the conditions of use. Most manufacturers

classify sleeping bags according to the minimum comfort temperature(MCT). Bags should be designed to keep the occupant comfortably warm,

when used at this temperature, provided they are in a tent and using a

quality sleeping mat. The MCT classifications of use are as follows:

Class MCT Conditions

ISummer low level camping in the UK. Travel to

warm/temperate climates.

3 season mountain camping in the UK. Travel to coolerclimates.

3 I o o e 4 season camping in the UK. Alpine walking. Himalayan

trekking.

4Winter mountain camping in the UK. Alpine

-20oe mountaineering. Ski touring. Expeditions to all but the

highest, coldest places. ~-30oe Expeditions to the highest, coldest places (e.g. polar).

5. Waterproofing: some protection against contact with wet ground is

a desirable, though not an essential feature of sleeping bags.6. Drying time: sleeping bags should be capable of drying quickly.

7. Tear resistance: good quality sleeping bags use ripstop materials

to improve resistance to accidental tearing during use.

8. Flame retardation: this is a desirable property of the materials

used to manufacture sleeping bags.

9. Breathability: the ability of the materials to transfer perspiration vapour

from the skin to the outside of the fabric.

10. Zip together: some sleeping bags are designed to zip together

with other bags. This requires right and left handed versions.

Student sheet A 3.2



Information sheet (a) for activity 3


Cover and lining fabrics'

Cover fabrics

Most sleeping bag manufacturers use a variety of polyester, cotton and nylon

fabrics for the cover material. This is because of the strength and lightweight

characteristics of these particular materials. The price and quality of a

sleeping bag depends on the quality of the materials used, as illustrated in the

following table.

Price range Material

Lower Polyester cotton quality nylon fabrics

Medium Ripstop quality nylon for added strength

Upper Pertex and ripstop quality Pertex

Pertex is a lightweight fabric made from tightly woven nylon microfibre

having almost 4000 filaments per square centimetre. It is water repellent,

windproof, breathable and dries very quickly when wet.

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 11 1 1 11 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 . •

The material comes in three

qualities, specified by weight as

follows:

Pertex

Pertex 4 (54g/m2)

Pertex 5 (69g/m2)

Pertex 6 (80g/m2)

A dense weave of microfine filaments

giving optimun pore size

Pertex 4 is matt, silky and extremely comfortable, making it an ideal high

quality sleeping bag cover fabric. For even higher quality and strength, with

increased resistance to tearing, there are two 'ripstop' versions, Pertex RS4and Pertex RS5. These are superfine, soft, immensely strong and were

originally developed for use in parachutes.

A hydrophobic coating of polyurethane can be applied to Pertex RS5 to

produce a completely waterproof yet breathable fabric. This fabric is more

expensive and known as Pertex 1000.

Ijning fabrics

Lining fabrics should be comfortable, soft and pleasant to feel. Sleeping bags

in the lower price range tend to use a brushed cotton polyester cotton or

viscose nylon for inner liners, in combination with an outer cover of polyester

cotton or nylon fabric. Sleeping bags in the upper price range tend to use

Pertex materials throughout, in particular Pertex 4 for linings.



Information sheet (b)for activity 3


Filling materials- natural

Goose and duck down

Down is the lightest, warmest filling material available. However, it is

also the most expensive. Down should be used where lightweight, warmth

and lack of bulk are the priorities. The use of goose and duck down as a filling

material in sleeping bags is because of their durability, softness (cushioning

property), packability (resistance to compression damage) and loftcharacteristics. Down comes from the breast of the goose or duck and, in

contrast to the feathers from other areas, has no quill.

Loft is the ability of a filling material to maintain an even distribution when

enclosed by a cover fabric. Down is normally used with a small percentage offeather added which improves the loft quality and prevents the down from

clumping (gathering together in different areas of the sleeping bag).

Down filling is normally specified as the percentage of down followed by the

percentage of feather, e.g. 9 1 would represent 90 down with 10 of

feather. The best downs give a very high loft which in turn means more

warmth for less weight.

The insulating performance of a particular down is measured by its fill power.The fill power figure represents the volume (in cubic inches) occupied by 10z of

fully lofted down. Some examples of commonly used specifications are shown

below.

Fill type Fill power

85/15 DD 450

90/10 GD 550

90/10 DD 65 0

96/4 GD 70 0

DD duck down

GD goose down

Thermal insulation is then governed by a combination of the total mass and fillpower of any particular grade of down used in an individual sleeping bag.

e.g. A sleeping bag with a total mass of 1000g filled with 9 1 DD, will give a

higher thermal insulation than one with a total mass of 300g filled with

9 1 GD. This is because the first one has both greater mass and greater

fill power than the second.

A sleeping bag with 700g total weight of 96/4 GD will give a higher

thermal insulation than one with B O O g total weight of 9 1 GD. In thiscase, the first one is lighter, but has a fill power of 700, whereas the

second one, though slightly heavier, has a fill power of only 550.



Information sheet (c) for activity 3


Filling materials- synthetic

Polyester fibres

Some characteristics which account for the use of polyester fibres as

filling materials for sleeping bags are as follows:

• toughness with good compactability and recovery

• less expensive than down• combines lightness and comfort (but heavier than down)

• is a thermoplastic with a natural feel• good thermal insulation properties and 'mildew resistant'

• dries much quicker than down• machine washable (usually at 40°C)

Polyester fibres used in sleeping bags can be either solid or hollow. Although

the hollow fibres are more expensive they trap more easily the thermal

insulation properties, and are softer. Sometimes a combination of solid and

hollow fibres are used to combine a lower cost with increased thermal

insulation, softness and resilience.

DACRON QlJALLOFIL 4 and 7 are all year round suitable polyester fibres with

a unique construction which combines the qualities of down with the easier

care and quicker drying characteristics of synthetic fillings. Each tiny fibre

incorporates four or seven air channels which trap air and provide excellent

loft and resilience. They are lighter in weight than other polyester fibres, have

20 more thermal resistance, and are used with stitch constructions normallyassociated with down filling. Although more expensive than other polyester

fillings they are a cheaper alternative to down.

Hollow fibres

QUALLOFILfibres

with 4 channel construction

QUALLOFILfibres

with 7 channel construction

Synthetic fillings are normally specified as the number of layers Batts of

filling followed by the mass in grams per square metre of each layer. Some

commonly used specifications for synthetic filling materials are:

1x 90 2x 125

Lx 180 2x 180

1x 270 2 x 270

170+ 1x 240

e.g. 1 x 90 means 1 filling layer Batt with a mass of 90g per square metre

and 2 x 125 means 2 filling layers Batts each with a mass of 125g per square

metre.



Information sheet d for activity 3

The construction of sleeping bags

General construction

Sleeping bags comprise an outer cover, a filling, and an inner lining.

Outer cover

Stitch constructions used with down filling

Cover fabrics for use with down fillings are stitched into channel

constructions to allow maximum loft. Each independent channel is known asa baffle. The different arrangements illustrated below are used to help create

an even loft and a minimum of cold spots.

Box Wall Double Offset Box Wall

Slant Box Wall

(enhances overall insulation) V Baffles

Double Box Wall

(2 layers - increased thermal insulation)

The vertical side walls of the baffles are usually made from a lightweight

knitted fabric material, different from the cover and lining. Elasticated thread

is often used on high quality sleeping bags to sew the baffles in place. This

allows the fabric more flexibility to gently contour around the body shape and

thus reduce heat loss.



Information sheet (e)for activity 3

Stitch constructions used with synthetic fjUing

Sewn Through constructions are used for the cover fabric with synthetic

fillings. Any line of through stitching creates cold spots which reduce the

insulation properties of the materials. To overcome this, Double Offset Layerconstructions can be used.

Sewn Through Double Offset Layers

Intermittent stitch patterns are other alternatives used to gain maximum loft

with minimum restriction. These consists of a series of short, alternate zigzaglines of stitching to hold the cover, filling and liner together and produce a

high efficiency of thermal insulation.

Intermittent Stitch

Construction

The combined materials are then overlock stitched around the edges, creating

a large internal air space.



Information sheet t for activity 3

General manufacturing process

Shape

The shape for a particular sleeping bag is marked out on the materials and cut

by hand, using template patterns in a similar manner to that used in the

clothing industry.

Down filled sleeping bags

Pertex material is normally used for down filled bags. Prior to sewing, the

Pertex is 'down proofed' by passing through a set of rollers, one of which is

slightly heated. During this process the surface fibres on the inner side of the

material are fused together, which prevents the down from infiltrating the

fabric. This produces a 'wet look' appearance on the inside whilst leaving theouter surface of the Pertex in its attractive natural matt state.

The box channel constructions are individually sewn. using heavy duty sewing

machines. The down is weighed out and placed into the box channels by handin a still air environment (otherwise the down disperses into the air).

Fibre filled sleeping bags

Fibre preparationSynthetic fibres (which look like cotton wool) usually arrive at the factory in

bales. Fibres of different types and densities are mixed together to createspecific percentage blends for particular jobs. The blend mix is then passed

through a carding machine (as in the wool industry) to produce flat layered

sheets of different layer thicknesses.

To keep the fibres in place the carded sheets are either sprayed with a quick-

dry resin to bond the fibres on the outer surfaces, or special hot melt fibres are

included at the blending stage which melt when the layered sheets are passed

through an oven, creating an integral bond with the other fibres.

Resin spray

Fibre layered

sheet



Information sheet g for activity 3

The outer cover material, fibre filling sheet and the lining material are

assembled together like a sandwich. The materials then pass through a

multi needle quilting machine which is set to stitch either straight lines or an

intermittent zigzag pattern.

Movement of needles for

intermittent stitch patterns

Sleeping bag

materials -~~ ~ Flatbed

To produce the intermittent stitch pattern, the needle heads descend and move

a fixed distance sideways in one direction, then lift and descend at anotherpoint before moving in the opposite direction to return to their original position,

as the materials pass through. This sequence repeats and the intermittentzigzag stitch pattern is built up. The process is computer controlled.

The materials are then manually overlock stitched around the edges using

heavy duty sewing machines.



The Construction of Sleeping Bags

Stitch constructions used with Down filling

Box Wall Slant Box Wall

(enhances overall insulation)

V Baffles

Double Box Wall

(2 layers - increased thermal insulation)

Stitch constructions used with synthetic filling

[] iOO~:[E

ewn Through Double Offset Layers

OHP 2

20378-product design an activity based case study of sleeping bags

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