CFS Fibreglass Guide

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Fibreglass Guide CFS FIBREGLASS

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Transcript of CFS Fibreglass Guide

Page 1: CFS Fibreglass Guide

Fibreglass Guide

CFSF I B R E G L A S S

Page 2: CFS Fibreglass Guide

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CONTENTS

Working out quantities 3

Working with Fibreglass 4

Catalyst Mixing Ratios 5

Conversion Chart 5

Polyurethane Liquid Foam 6

Topcoating 8

Pattern & Mouldmaking hints 9

Pond Lining 10

Roofing 14

Repairs to boats 18

Casting 22

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WORKING OUT QUANTITIES

RESIN TO FIBFEGLASS RATIOSFor an effective laminate, it is essential that the fibreglass material is thoroughly 'wetted-out' with Lay-up Resin(Resin A). The amount of resin needed to do this varies from one fibreglass material to another. The followingtable shows the amount of Resin A needed per square meter of material.

MATERIAL SPREAD RATES(Note: CSM = Chopped Strand Mat)

RESIN Priming PlywoodLaminating, for each layer 300g CSM Resin = 650g per m2.Laminating, for each layer 450g CSM Resin = 1.1 kg per m2.Laminating, for each layer 600g CSM Resin = 1.5kg per m2.For multiple layers of CSMLaminating with FabricsCasting, unfilled. For each litre

Resin = 500g per m2.

Resin = 2.5 x CSM weight.Resin = 1 x Fabric weight.Resin = 1.16kg per litre

GELCOAT Gelcoating on mould surfaceTopcoating after laminating

PIGMENT PASTES

CATALYST

WAX SOLUTION

STYRENE

2 PART PU FOAM

PVA RELEASE AGENT

G4 SEALER

CARBORUNDUM GRIT

Add 10% by weight to Gelcoat

Add 2% by weight to Resin or Gelcoat.

Add 2% by weight to Gelcoat,to make "Topcoat"

Add 2% by weight for thinning resin.

Expands 25 times its original volume.

On non porous surface

Sealing porous surfaces

Spread onto wet gelcoat

550g per m2.650g per m2.

100g per kg

20g per kg

20g per kg

20g per kg resin.

1kg per cu ft.

200g per m2.

250g per m2.

1.6kg per m2.

Estimating quantities is very simple using this information and a few calculations.The important information you require is the surface area you wish to cover, expressed as "m2" and the totalweight of Chopped Strand Mat (CSM) used, expressed as "grams per m2".

CALCULATING QUANTITIESExample; Area to be covered is 1m2.Thickness of CSM required is 3 layers of 600gTherefore, the total weight of CSM = 1.8kg (3 x 600g).Resin required for this laminate would be 4.5kg (1.8kg CSM x 2.5)Please note that the information given is as a guide only. Allowances should be made for overlaps and errorsduring laminating.

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WORKING WITH FIBREGLASSWORKING AREAWhether laminating or casting you should work in anambient temperature around 20°C, as this ensuresthat the resin will cure correctly. Resin will not cureadequately below 15°C, and at temperatures above300 C, they will cure too quickly! You must not useoil heaters or electric fires (see below), so maintainthe temperature with convector heaters, 'Dimplex'radiators, or similar. You will need trestles to supportthe mould at a comfortable working height for smalljobs, of course, you can use a normal workbench ortrestle table. For protection cover with polythene,polyester film or brown wrapping paper.

PREPARING RESIN FOR CASTING ORLAMINATINGAll resins, whether for casting or laminating, requirethe addition of catalyst (hardener) to initiate thecuring process. Use a safety dispenser to add20ml of catalyst per kilo of resin. Stir thoroughly.The hardening process begins immediately, so onlycatalize a working quantity or your mixing containerswill soon be full of solidified resin.If pigments are being used these should be stirredinto the resin before adding the catalyst. Add up to10% of pigment, depending on the depth of colourrequired. To maintain consistent colour on a largeproject, it is often a good idea to pigment all theresin and then decant working quantities to becatalysed as required.Once catalized the resin gradually cures, takingon a jelly-like consistency in about 10-20 minutesbefore becoming hard in about 30-40 minutes atroom temperature (about 20°C). The curing processgenerates heat (known as 'exotherm') within theresin. Too much catalyst or large volumes of resinincrease this heat, so a thick laminate or a largecasting should preferably be built up in stages.

MIXING CATALYSTThorough mixing of catalyst into resins and gelcoatis very important. Also the correct additions shouldbe observed to maintain good results. Dispensersare advised for accuracy. The table below givesthe correct ratios of catalyst to resin and gelcoat byweight. 1% is considered a slow mix, 2% is ideal,3% is a fast mix. Additions outside these bands innot advisable for proper curing, in fact adding morethan 4% may result in a failure to cure. The pot life

of these mixes is also determined by temperature.The higher the temperature the faster the cure. Asa general guide 2% addition at 20°C gives 15-20mins pot life. The resin will always cure quicker if leftin a mass such as the mixing bucket or in castings.

APPLYING THE LAMINATEUntil you have experience do not mix up too muchresin at a time certainly no more than 2kgs, enoughfor between 1 and 1.5 m2 of fibreglass.For large flat areas it is quicker and easier to applythe resin using a medium pile roller. Roll on a coatof catalized resin to the surface and then lay onthe first section of fibreglass, apply more resin to"wet out" (saturate) the fibreglass. As the binderholding the fibreglass dissolves it will becometranslucent. Then apply the next layer which shouldbe cut slightly smaller to create a built in staggeredoverlap and again apply more resin. Once thefibreglass has been 'wetted out' it is necessary toconsolidate the two layers of fibreglass and this isdone using a metal roller. The roller can either beof the aluminium ridged variety, "paddle roller" or ametal "washer roller" but used vigorously it not onlyforces the two layers of fibreglass together but itremoves any trapped air, this appears in a laminateas a white blister, and care must be taken to ensurethat this is done.Having completed this section move on to the nextand with the overlap built in full widths.Unless the corners are radiused do not attemptto take the fibreglass around the corner since itis difficult to "persuade" fibreglass to lay into rightangled bends, start again with a built in overlap.Since there will be a butt joint at the corner it isthen recommended that a strip of fibreglass some200mm is cut with the edges frayed out and thenapplied as a tape would into the corner. You will findthat this is easier since the fibreglass can be bentinto shape. Once the fibreglass has been "wettedout" it is easier to work into corners and aroundmore complicated and compound shapes.For this purpose a brush is used with a stipplingaction and if required the fibreglass can be pre-wetted out on a flat board before being stippled intoposition.

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CATALYST MIXING RATIOPages

1 cc = 1 mg = 1 cc

RESIN WEIGHT

Addition of Catalyst (ml)

1%

2%

3%

50g

0.5

1

2

100g1

2

3

250g

2.5

5

7.5

500g

5

10

15

1kg10

20

20

5kg

50

100

150

CONVERSIONS

Length

Weight

Volume

Area

Millimetre (mm)Centimetre (1cm = 10mm)

Metre (1M = 100cm)Kilometre (1 Km = 100M)

Gram (g)Kilogram (1 Kg = 1000g)Tonne (1T= 1000kg)

Cubic centimetre (crrr)

Millilitre1(ml = 1 cm3)Litre (1L= 1000ml)

Square Foot (sq.ft)Square Metre (M2)

Metric Units

1in = 25.4mm1in = 2.54cm1 ft = 30.48cmyd = 0.9144m1 mile = 1 609 km

1oz = 28.35g1 Ib = 0.4536kg1 ton = 1.0 16 tonne

1 cu.in = 16.387 cm31 fl.oz= 28.41ml1 pint = 568ml

1 sq.yd = 0.929m2

Imperial Units

1mm = 0.0394 in.1cm = 0.3937 in

1m = 1.0936yds1km = 0.6214 mile

1g = 0.0353oz1 kg = 2.2046 Ibs1 Tonne = 0.984 ton

1cm3 =0.061 cu.in1ml = 0.0352 fl.oz1L= 1.76pints

1M2 =1.1960sq.yds

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POLYURETHANE LIQUID FOAMA two-part liquid yielding a high strength, rigid,closed-cell foam for cavity filling and buoyancyapplications. The foam may be used to fill cavitiesfrom 50mm to 300mm wide.

The liquid is extremely simple to use. Immediatelyafter mixing, it is poured into the cavity to be filled,then left to foam and cure. Deep cavities should befilled with layers of foam about 25mm deep, as theexotherm (internal heat) generated during the curingprocess increases with greater volumes.

The foam imparts considerable stiffness with onlya minimal increase in weight and is very usefulfor filling masts and booms for extra rigidity.Polyurethane foam is extremely buoyant - onekilo of mix will produce enough foam to supportabout 27 kg in water. To produce enough buoyancychambers on most small craft, the foam mix ispoured into previously prepared box sections - i.e.,under the seats.On canoes, the mix is simply poured into the bowand stern sections, then covered with "bulkheads"of fibreglass.

The foam can also be used (with a suitable releaseagent) to produce lightweight moulded items. Wood,fibreglass or metal moulds can be used and areproduced in the same way as those for fibreglasslaminating. However, due to the pressure generatedby the foam, the mould needs to be considerablystronger than is normally the case, and with a splitmould, the separate parts must be securely boltedtogether. A typical use for this technique is in theconstruction of sailboard hulls although it shouldonly be employed in conjunction with a suitablelaminated shell designed to provide the necessarystrength.

The foam mix, being designed to produce maximumbuoyancy, is of comparatively low density and lacksany great inherent strength.

Apart from the permanent buoyancy the foamprovides it also has good thermal insulationproperties as well as reducing noise levels.

Polyurethane foams are resistant to benzine, dieseloils, acids and alkalis in normal concentrations.

PRODUCING THE FOAMUse two plastic cups to measure out an equalvolume of each part, then pour both componentsinto a mixing container. Stir thoroughly but quickly-the mixture will begin to thicken in 25-35 seconds,and must be poured into the cavity to be filled up toapproximately 25 times its original volume, reachingits maximum rise in about 150 seconds. It should beleft to set. It will reach a sticky condition in about 4minutes and will be completely cured in about halfan hour.

The uncured mix is highly adhesive and should bondto most materials. Whilst the mixture is foaming takecare not to inhale the fumes.

Insufficient foam may be generated due to incorrectproportions of components, inadequate mixing,too low working temperature (optimum workingtemperatures is 20°C) do not use below 10°C orusing a restricted mould.

Polyurethane foam can be used for structuralstiffening in masts and booms- with minimalincrease in weight; accoustic and thermal insulation,rapid prototype shapes in fibreglass and lightweightfoamed shapes produced in wood, fibreglass ormetal moulds.

Each liquid kilo of polyurethane yields approximately0.08m2 (1 cu.ft.) of rigid foam and will support 27 kgin water.

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STORAGE AND HANDLINGThe two components will remain stable for atleast six months, if stored in sealed cans in dryconditions. Storage temperatures should not exceed20°C.Contamination of the materials by moisture must beavoided. The part 2 compound is an isocyanate -care must be taken to avoid contact with the skin oreyes. You should also avoid breathing the fumes.Always work in a well ventilated room or in the openair.If the foam mix is in contact with the skin or eyes,flush IMMEDIATELY, with copious amount of water.If irritations persists, consult a doctor. Medical aidshould also be obtained if excessive inhalationoccurs or if any material is swallowed.Always exercise care when opening cans, aspressure can build up in the container.

SPILLAGE AND DISPOSALSpillage should be soaked up in rags or cottonwaste, and the area sprinkled with sand or sawdust.This should be left for at least ten minutes, thenswept up and the area washed.The waste should be soaked in water beforedisposal. When dealing with large spillage,protective clothing and respirators should be wornbecause of the danger of fumes.

FIREAlways use dry powder extinguishers.

FOAM BLANKSPolyurethane foam blanks are available ready-formed for use as surfboards or sailboard hulls. Theblanks are shaped to individual requirements by theuser, sanded down and sheathed in a fibreglassskin. They are constructed from white foam which,whilst retaining a reasonable degree of buoyancy,gives greater strength and rigidity.

CALCULATIONSPU foam is supplied in several pack sizes andit is necessary to calculate the volume of thefoam required so as the correct pack size can beselected. This can be done by multiplying length bywidth by height in metres and dividing by .0283. Thisgives the total amount of foam required in kg.Example:A bouyancy tank measuring, length 0.5m x width0.5m x height 0.5m = 0.13m3.Divide this figure by .0283 = 4.59Total liquid foam required is 4.59kg (1 x 5kg pack).0283m3 (1 cu.ft) of hollow buoyancy tank provides28kg of positive buoyancy in fresh water and about30kg in sea water.Polyurethane foam gives about 27kg per m3 ofbuoyancy.The calculations on buoyancy are complex sincemany materials have a buoyancy factor that has tobe deducted from the total theoretical requirement.As a very rough guide including crew, motor andequipment the following can be used:-2.4m' dinghy requires 70kg approx. 0.08m33.6m runabout requires 198kg approx. 0.23m34.2m sailing dinghy requires 88kg approx. 0.1 Om36m sailing cruiser requires 830kg approx. 0.93m3

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