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From Fibreglass Material Services Pty. Ltd. (FMS)
188 Manns Rd. West Gosford NSW Ph 02-4324 7015
What is a Gelcoat ?
A gelcoat is a layer of special
thick coloured resin that protects the laminate and makes it look attractive.
It is usually about 1/2 mm (500 microns) thick and is applied to the mould
surface by spray or brush before the fibreglass laminate. It also has a fast
geltime - typically 10 minutes, that helps prevent "stick-ups".
Gelcoats always stay sticky on the surface. This helps the laminate to stick
and is the reason why gelcoats should never be used as a final coating. For
finish coats use a flowcoat.
What is a flowcoat ?
A flowcoat is similar to a gelcoat
except that it is used after the laminate has been made. Flowcoat has
a small quantity of wax added to enable the surface to dry "tack-free".
It is usually brushed but can also be sprayed. Flowcoats, like gelcoats
are available in a wide range of colours.
What is the difference between Q Cells and Microlight ?
Both materials are small hollow spheres
that are mixed with resin to make a lightweight bog or screeding material.
Q Cells can be used with both polyester and epoxy resins; Microlight should
only be used with epoxies.
Q Cells are white, Microlight is light brown.
Q Cells are the least expensive but are
a little harder to sand and the dust given off during mixing and sanding can
be an irritant. Microlight is very easy to sand, gives off no dust during
mixing and reduced dust during sanding operations.
What is the difference between polyester resin and epoxy resin?
Polyester resin is the most common,
the majority of boats and other fibreglass items are usually made from polyesters.
Polyesters are more economical, easier to use, more user friendly, more forgiving
and less of a health hazard than epoxies. Polyesters are compatible with the
vast majority of reinforcements used in the fibreglass industry including
chopped strand mat. Epoxies are generally stronger than polyesters, are much
better adhesives, have a low tolerance for mixing errors and can cause allergic
reactions, dermatitis, etc. They perform better than polyesters in "sticking"
situations such as boat sheathing. All epoxies yellow when exposed to sunlight.
Epoxies are not readily compatible with chopped strand mat.
Epoxies will generally stick to polyesters
but polyesters do not usually stick very well to epoxies without a special
primer coat.
What is the difference between Carbon Fibre and Kevlar?
Carbon (or graphite) fibres are the stiffest
fibres currently commercially available (and the most expensive). They are
used extensively in the aviation, aerospace and sporting goods industries
to reduce weight. Carbon suffers from poor impact strength (much worse than
standard fibreglass).
Kevlar is also very stiff and has good impact strength, but poor compressive
strength (much worse than standard fibreglass).
Both carbon fibre and Kevlar will generally give better results when used
with epoxy.
Should I use woven cloth or chopped strand mat?
With epoxy, use woven cloth or tape.
With polyesters use chopped strand mat for most applications, especially compound
curves and building up thickness quickly. Use woven cloth for sheathing and
or when thinner high strength laminates are required.
How much polyester resin should be used ?
225 gsm chopped
strand mat 500ml
450 gsm chopped
strand mat 1
litre
600 gsm chopped strand
mat 1.5
litres
4oz woven
cloth 500ml
*
6oz woven
cloth 500ml *
10oz woven cloth 500ml
* There
will be a small amount left over
From Fibreglass Material Services Pty. Ltd. (FMS)
188 Manns Rd. West Gosford NSW Ph 02-4324 7015
2. Measure out sufficient resin
3. Add 1.5% of hardener to the resin and mix thoroughly all the way to the edges of the container.
Use the mix within 20 minutes - less in hot weather.
NOTE - In cold weather use 2% of hardener. In hot weather use 1% hardener
4. Brush some resin/hardener mix onto the surface, place fibreglass mat in position and work more resin mix into the mat until all the air bubbles have been removed. Add more layers as needed. Proper wet out of the fibreglass with resin is most important to the success of the job. Air bubbles can be worked out with a stippling (tapping) motion of the brush, or better still with a metal consolidating roller
From Fibreglass Material Services Pty. Ltd. (FMS)
188 Manns Rd. West Gosford NSW Ph 02-4324 7015
2. Wax the mould according to the instructions on the can of wax. Allow to dry for al least 30 minutes after the last coat.
3. Apply the PVA release agent either by wiping it on with a small piece of Wettex or by spraying. Be careful not to leave runs as they will take a long time to dry and will come out in the finished product. Do not apply by brush as it will leave "train lines" in the release coating which will also come out in the finished product. Allow to dry. On a hot day it will take about 10 minutes and on a cold wet day it could take 2 hours or more.
4. Calculate the amount of gelcoat required at the rate of 400 mls (ccs) per square metre.
5. Calculate the amount of catalyst required using 1.5% on a hot day and 2% on a cold day. Use a small measure for amounts over 2mls and for lesser amounts count drops where 35 drops gives 1ml. NB. Catalyst is a dangerous liquid and must be handled with care. Read all the safety instructions on the container before use.
6. Mix the catalyst thoroughly with the gelcoat, using a flat stirring stick
7. Brush or spray the gelcoat onto the mould using light, even strokes, preferably going in the same direction. Do not push hard on the brush. Let it "float" over the surface of the mould, leaving behind a thick coating - about 0.5mm will be OK. Go over thin spots and smooth out thick areas until satisfied. Work quickly as the gelcoat will start to set in about 10 minutes. Wash the brush out straight away with acetone. Allow the gelcoat to gel and cure until it is almost touch dry - about 2 hours on a hot day and up to 6 hours on a cold day.
8. Cut or tear the chopped strand mat to fit the mould, allowing an extra centimetre around the edge. On tight curves tear the mat to fit, adding extra pieces if needed. Put the mat onto a clean surface until ready for use - such as newspaper.
9. Calculate the amount of resin needed - but mix no more than can be used in 30 minutes.
500mls for every square metre of 225gm chopped strand mat.
650 mls for every square metre of 300 gm chopped strand mat.
1 litre for every square metre of 450 gm chopped strand mat.
1.3 litres for every square metre of 600 gm chopped strand mat.
10. Calculate the amount of catalyst needed - 1% on a hot day and up to 2% on a cold day.
11. Mix the catalyst thoroughly into the resin.
12. Brush a thick coat of resin onto the gelcoat in the mould.
13. Position the glass in the mould on top of the wet resin and then add another coat of resin, taking care not to displace the fibres. It may be necessary to "dab" the brush against the glass fibres rather than brushing to avoid moving them. Make sure that every part of the glass is "wet out" thoroughly and that there are no white (dry) spots. Wait for 2 minutes to allow the fibres to fully saturate.
14. Consolidate the laminate, by using a grooved metal roller over all the wetted area. This removes air bubbles and gives a good quality laminate free of voids. Don't push the roller too hard as it will clump the glass. If the roller pick up the glass rinse in acetone and start again. Allow the job to cure for 1-2 hours.
15. Clean the brush and roller is acetone.
16. Add additional layers of glass and resin as needed, noting that 2nd and subsequent layers cam be laminated at the same time as long as each one is rolled properly. Allow the job to cure - preferably overnight.
17. Remove "nibs" from the laminate with a sharp knife or abrasive paper (80 grit). If the laminate has been left for 24 hours or more it should be sanded all over before flowcoating.
18. Calculate the amount of flowcoat needed based on 200 mls per square metre of mould surface.
19. Calculate the amount of catalyst needed - 1.5% for a hot day and 2% on a cold day
20. Mix the catalyst thoroughly into the flowcoat and brush or spray onto the job in long even strokes- keeping to one direction if possible. Work quickly as the flow goat will gel in about 10 - 15 minutes depending on temperature. Clean the brush in acetone
In laying up fibreglass boats often small pockets of uncured resin get trapped in the laminations. This draws in moisture from the outside or the bilge and as a result more resin is dissolved and so the process goes on. A build up of pressure can cause further delamination to the extent that a structural weakness may develop. The familiar blister on the outside of the hull is a sure sign, but the only real test is to locate the presence of moisture in the laminations. Fortunately there are now instruments that can detect moisture in the laminations that is not noticeable from inside or outside the hull. When slipping your boat a quick run over with a moisture meter will detect trouble spots.
This will also identify those many small blisters caused by trapped air and whilst not osmosis, they will eventually cause trouble. A true osmosis blister, when pierced ejects a pungent acidic liquid, under pressure - so do so only with appropriate eye protection.
Osmosis is curable. If small and isolated spots are found, it is not expensive. However, if moisture is found in many places even though it may have not developed the familiar blisters, early treatment will be less costly in the long run. Even if a hull has no evidence of osmosis, a full treatment with a barrier coat can be good insurance.
A leading UK authority on osmosis (Tony Stanton-Bevan) has found that 70% of the thousands of vessels he has surveyed had developed osmosis. And that is in Britain. It occurs at a higher rate in warmer climates.
Polyurethane coatings improve colour retention and
gloss finish of fibreglass laminates, and are used frequently for repair and
re spray of FRP laminates. There is a wide range of colours available and with
some simple precautions application is easy.
Surface Preparation -Recently Moulded Items
1. Solvent
wash using clean rags and thinners 60-0003.
2. Wet
sand using 280 - 300grit paper.
3. Wash
with fresh water and allow to dry.
4. Repeat
step 1 prior to coating.
Surface Preparation - Aged Surfaces
1. Wet
sand with 280 - 300 grit paper
2. Repair
gelcoat cracks and damage.
3. Spot
sand repaired areas, initially with 120 grit paper & finishing with 300
grit paper.
4. Fresh
water wash and allow to dry.
5. Inspect
for blemishes.
6. Solvent
wash using clean rags and thinners 60-0003 prior to coating.
Priming
Even though the use of recoatable polyurethanes
over sanded unprimed gelcoat can be successful, the use of a primer such as
Luxepoxy 4 white primer is recommended. This primer is inexpensive and easy
to apply - it cal be tinted to approximately the finished colour if required.
Application
In addition to specific instruction with the product
used the following hints should also be followed.
1. Avoid
application below 10 deg C, above 30 deg C and within 3 deg of the dew point.
Do not apply in
a dusty environment.
2. Ensure
that the correct thinners is on hand prior to commencement.
3. Mix
all components thoroughly with a broad flat clean stirrer - ensuring that
the mix rate is accurate.
4. Allow
the correct digestion period for the two pack products - usually in the order
of 10-30 minutes.
5. Apply
subsequent coats within the stated recoat interval - otherwise lightly sand
the surface.
6. Even
though a spray application will give a superior finish and a more consistent
colour development, brushing
may be necessary in some circumstances. A high quality brush and a unidirectional
"flow" technique
will give best results.
7. Do
not place coated surfaces into service immediately - allow at least 2 days
at or above 25 deg C before
compounding or buffing.
Brushing Technique
Load the brush and "flow" the polyurethane
on the surface allowing it to self level. Do not overwork with the brush and
do not brush wet areas previously painted. Use short unidirectional strokes
with a good quality brush.
Spray Technique
Equipment should be clean, free of contaminants,
dry and properly regulated. Instruction specifications should be precisely
followed. To avoid runs on vertical surfaces thin coats can be applies at
10 min intervals to build up the required thickness. Application of a second
full coat before the minimum recommended time is likely to cause crinkling
of the first coat.
Before using materials of any chemical nature the wise craftsman retains information about the care of handling the materials and the proper safety precautions. Resins, Catalysts, Solvents and Reinforcements all have Material Safety Data Sheets (MSDS) that are easily obtained.
Personal Protection
When undertaking any job it is important to consider exposure to both the user and others nearby. Items such as Protective Clothing, Breathing Equipment and Eye Protection will usually be required.
Working in Confined Spaces
When working on boats with fibreglass the job will often be in a confined and unventilated space in which case special precautions are needed. Resins, solvents and paints all give off fumes that are usually heavier than air. In a small confined space they can quickly build up and without warning incapacitate anyone without the proper breathing equipment. Furthermore most solvents and paints give off fumes that can become quite volatile- displacing air in small spaces. A stray spark would then be disastrous. Therefore proper forced ventilation as well as wearing breathing equipment is important for safety and survival.
Sunlight, Water and Salt combine
very well to degrade and oxidise external and internal gelcoated and clear
timber finishes. Over time there will be evidence of progressive oxidation,
chalking, staining and fading. Darker colours are at greater risk because
they generate and then are subjected to higher temperatures - which accelerates
the aging process.
Surfaces should be protected with Polymer
Glazes, Waxes and Polishes - especially those exposed to UV radiation. Choose
protective coatings and materials of high quality suitable for the surface
to be protected.
COMPOUNDS
Compounds are specifically formulated either as oil or water based pastes. Additional solvents are used with medium or coarse grade abrasives that are designed to remove severe surface imperfections such as coarse scratches, oxidation, stains and etching. Compounds can be applied by hand or machine. As a result very fine scratches and swirl marks can be left behind. These are removed with the correct polish.
POLISHES
Polishes are specifically formulated as either water bases liquids or pastes. They are designed to remove minor surface imperfections such as fine scratches, light oxidation, water spots and swirl marks left from previous treatments. They contain a mild abrasive and produce a high gloss finish.
CLEANER WAXES
Cleaner Waxes are a wax / polish combination containing a mild abrasive capable of removing light to medium oxidation and fine scratch marks while leaving a protective wax layer, with a durable high gloss finish.
WAXES
Waxes are formulated blends containing glossifiers and other ingredients that produce a durable high gloss finish. Some are polymer based while others use a blend of natural or synthetic waxes. The finish results in a gloss surface which helps protect the gelcoat or painted surface and making cleaning easier.
Safety First - Remove loose clothing. If working close to water, secure power lead.
Machine Tool - The recommended machine buffing speed is 1200-2500 rpm.
Select the Right Buff - A different buff is required for compounding & buffing.
Weather Conditions - Working in overcast conditions or in the shade is best as most compounds & polishes dry out
Surface - The surface should be clean & dry. When removing dust and dirt wipe and clean in only one direction.
Application - Apply a small amount of compound or polish to the surface and spread it out in a circular fashion using a cloth to get an even distribution. When using the machine use an overlapping left/right or up/down motion pattern - and NOT a circular one.
Spur the Buff - To keep the buff working efficiently spur the buff every 3-5 minutes. Allowing the compound or polish to build up on the buff slows the process and can damage the surface.
Work to a Pattern - When doing a big job work to a pattern without introducing random areas to treat.
Care of the Buff - When the machine is turned off always place it upside down in a clean place to avoid contaminating the buff.
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