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Repairing/ painting fibreglass poptops.

Discussion in ''How To' & 'Handy Hints'' started by cbus, Jan 14, 2018.

  1. cbus

    cbus Well-Known Member

    sunshine coast
    A lot of poptops could do with some degree of repair or refurbishment.
    Hopefully the following may help.
    Its not hard if a bit if care is taken . results are directly proportional to care at each stage.

    This is assuming a full refurbishment. Minor repairs can be done in situ.

    Remove poptop.
    Create suitable stands so you can work at a comfortable height and poptop is supported "square".

    Separate the sections and remove all trim and sealants.
    Degrease and scrub ,rinse well.

    Most likely any chipboard stiffeners will be deteriorating. Regardless, take photos to guide reassembly and remove chipboard.
    Use these to cut new ones from a solid timber that will provide better strength for attachments.

    The dust is a strong irritant.
    You will itch for days if exposed and its bad for the lungs and eyes.
    Wear a full disposable paper overall set and wear mask and goggles.
    Silicone rubber masks are better than paper dust masks.
    Ski type goggles are better for vision and comfort
    You are going to need all of this for the spraying anyway so invest.
    Cotton hoods are also good and comfortable.

    If you do get itchy ,shower in cold water . prevents pores opening.

    Dry sand inner with a random orbital sander using an interface pad and 120-180 grit sandpaper. 6" palm sander is good if you have a compressor that delivers closer to 300l/min.
    Grey or beige aluminium oxide papers are pretty useless. blue or green ones are different and they last much longer and cut better. Especially when dealing with epoxy resins.

    The aim underneath is to key the surface for a coat of epoxy and cloth. Doesn't need to be smooth but needs to be clean and hopefully around 80% or more scratched up.

    For top / gelcoat. Same deal except you want it smooth and all sanded. Don't bother with sanding finer than 180dry.
    You may be able to sand this without the overalls if there is no exposed fibre. Use mask tho.

    Wipe down with a damp rag to remove dust and fibre.
    Dispose rags by wrapping in old plastic bags.
    Hose down work area.

    Ensure all moisture is dried out of any exposed fibre or cracks.
    Rinsing with acetone will absorb water. Blow out with compressed air.
    Dry in the sun for a week if unsure.


    For fine cracks a quality superglue is easy. You will be also sandwiching both surfaces and this gives added strength.

    Cracks all way thru .
    You can saturate with the broken edges with mixed resin and clamp or use superglue.
    Ensure top is sitting square and everything lines up
    To beef up the join, scarf out about 25% thickness both sides and build up with layers of resin and cloth to original level.
    Usualy scarfing would be a 7:1 ratio. In this case I would go a minimum of 25mm each side of crack on each face.

    Most poptops are flimsy and irregular.
    You will need to decide what finish you want.
    Personally I would repair any damage and cracks then apply a minimum 100gsm ( could go heavier if desired. Up to maybe 190gsm. ) layer of woven cloth using epoxy resins.
    This will help stiffen the top as well as sandwich any cracks.
    New stiffeners can be glued in place with a firm paste made of epoxy resin filled with glue powder.
    Details of use later
    Alternately a good bond with sika will do.
    Epoxy glue will prob be cheaper.
    Glass the timbers in with a layer or two of 190gsm cloth.
    190gsm woven cloth does not go around tight internal curves easily.
    Usual method is radius all sharp edges to about same as 5 or 10 cent piece.
    Fillet ( fill) inside corners with a glue powder mix.
    Work in with brush.

    Saturate the exposed edges of top to seal fibres.

    Large crushed areas are treated same as cracks except done as a whole surface.
    In this case grind off one surface so that you can saturate the core with an epoxy mix.
    It may help to add up to 15% acetone to reduce viscosity and help saturation.
    Once the resin has firmed but still tacky, apply another coat of resin ( it will be a fresh lot as working time is temp dependent but usualy less than 8 minutes.)
    Immediately work in successive layers of cloth to about level to finished surface or a bit under.
    Repeat other side.

    You need to distinguish between fractures and stress cracks in the gelcoat that are caused by rough handling and hammering during removal from mold.
    Such stress cracks are not structural. They often resemble spider webs with s point of impact being obvious.
    The only issue with these is they can delelop thru a new cost of paint.
    For this reason I would suggest a good physical key and at least a layer of 80gsm with resin before priming.

    Finish the underneath as you wish but it is usualy a rough finish of chopped matt.

    If just doing a repair underneath and not a full layer of woven cloth then chopped strand will better match existing surface.
    Tear the edge to blend rather than cut with scissors.

    I would also consider a full layer of woven on top surface. Probably 100gsm.

    Epoxy laminating resin is a 2 part product.
    Resin and hardener.
    Use mixing cups to measure.
    Different resins have different ratios so familiarise fully with the product chosen.
    ALLWAYS download a TDS on any product.
    It gives usefull info.

    Typically can be from 1-1 to 4-1.
    Closer ratios usualy superior but not critical for our use.
    For this purpose same for brands.

    Reaction is quite temp dependent.
    Keep contents cool as practical.
    A litre and 500ml mixing cup are a good start. Start with small mixes as you only have 5-8 minutes at about 25C.
    Don't continue to use once it starts to thicken or gell.

    Be accurate in measuring.

    Once mixed put in a shallow container such as 4litre ice cream container. The reaction is exothermic. Shallow container allows dissipation of heat. If heat builds then working time is considerably reduced.
    It can also get hot enough to cause ignition.
    DO NOT dump in waste bin or allow rags soaked in mix to sit in a pile. Can cause fire.
    Safe once reaction completed and cooled.

    Pays to wear disposable gloves. Some people sensitive to resins.
    If on skin don't wash off with acetone or thinners. These enter bloodstream quite effectively via skin.
    Wash with vinegar then rinse with water.
    The vinegar breaks down the resin very effectively.

    Use in a ventilated area.
    Concentrated vapour can kill.

    If necessary ,thinning is between 5-15%.
    Washing tools is with acetone.
    Allow to harden in plastic containers and it can be pulled out.

    Work in limited areas till familiar with use.
    Cut cloth to size before mixing resin.
    I usualy apply a thin surface of resin and bed the cloth into it . Applying more resin as needed to ensure cloth is saturated.
    When saturated it will be clear. No signs of white fibres.
    Use squeegee to remove as much resin as practical.
    The less resin to cloth ratio the stronger the job.

    If difficult to fit or work into corners you can allow the first coat of resin to tack of and it will hold the cloth in place. Allow another 1/4 hour then saturate with next coat and squeegee excess.

    If building layers stick to 2 at a time.
    To many in one hit gets difficult to squeegee out plus builds too much heat.
    Wait until firm but still tacky and apply more.

    If it has hardened overnight it will usualy have an amine blush.
    This feels slimy to the touch.
    Wipe with acetone then lightly sand prior to following coats.

    It must be cleaned and sanded before filling or painting.

    One exception is by spreading a light skim of mixed epoxy resin and Q cells or microlight over a cured but still tacky resin. Usualy a hour or few hours after resin applied.
    This gives an easily sanded surface ready for painting.
    Additional filler can go straight over if needed.

    Q cells and microlight are filler powders that are added to micedvresin to form a filler like bog.
    The more powder in the mix the easier it is to sand.
    Straight epoxy is very hard to sand.
    Another method of easy prep for next process is using peel ply.
    This is like fine curtain mesh that is squeegeed into last cost of resin.
    Next day it is peeled off and removes extra resin along with amine plus leaves a rough finish ready for next process .

    If sanding thru epoxy exposes cloth fibres they should be encapsulated with some fresh resin before proceeding.

    Epoxy resin is completely waterproof. Sanded filler should have a coat of resin applied and if desired squegeed off to leave a seal.

    Same applies to the top if you choose not to apply a layer of cloth.
    A layer of resin that is then squeegeed off and allowed to go till still retaining a dry tac is good for next coat of epoxy primer.
    Not essential tho.
    Epoxy primer can go straight over the sanded surface.

    Will post this before I loose it.
    Will continue plus add links to productd
    Jethro, Tangles, David H and 2 others like this.
  2. nils

    nils Well-Known Member

    I have to refurb my top this year (along with a very long list of other things) Though there are no cracks and breaks there are alot of places that need attention.
    I'll be using flow coat for the final finish as it has better resistance to the weather than gelcoat. I also need to cut the hole back in for the skylight as its been glassed over.

    What do you know about flocking something? The T3 roof internally is flocked and the years have not been good to ito_O
  3. Grantus

    Grantus Well-Known Member

    Southern ACT
    Assuming you are referring to the 80’s method of flocking, like insides of cutlery drawers, jewellery drawers etc..(usually green, but most colours were available to fire through a big nozzle spray gun).

    As we are starting 2018, I’d be de flocking, and looking at way more advanced methods of coating your roof.....;)
  4. cbus

    cbus Well-Known Member

    sunshine coast
    Sorry. Never flocked anything and not up on the process. Pigeon poop splatter closest :)
    Stone guard any use?
    Reread and figured you do mean the kombi roof and not under side of poptop.
    High temp contact glue and material or maybe the plastic sheeting that trimmers use for door cards and cover them before installing.?
    Is the normal velour type roof lining a close match?

    Re flow coating . once roof is back to sound material what are you thinking of using?
    You could bog and flatten quickly with random orbital if it needs the build. Fine bog ,have to check brand, about $60/4kg. Apply with steel trowel and screed with metre long wallpapering ruler ;)

    EDIT. Would be wary about large or thick applications of bog due to the flexibility of the thin build of poptops. Bog is likely to crack if flexed too much.
    Might need to stiffen first with stiffening panels of sandwiched foam or light wood. Being careful about added weight affecting spring operation.
    Stiffener sections would likely remove much of any sag in panels due to thin construction.

    Can use a self levelling finishing bog over that if desired but its expensive.
    High build epoxy is harder to sand than auto high builds but easily half the price. Just a maybe.
    Final primer can be heavy wet on wet.
    Poly U 400 is a common top coat for boats and busses etc. Better resistance to chalking than gelcoat.
    Or go up a notch and use something like Jotun Imperite.
    Hard as hell and still flexible.
    Beats anything automotive.
    Slow flash off as is necessary for doing boats ,trucks etc so good finish off the gun and no compounding.
    Epoxy primer about $100 / 4l.kit.
    Imperite. About $200-250 for 5l kit
    Dedicated reducer approx $60/4l.
    Just options.
    Last edited: Jan 16, 2018
  5. David H

    David H Well-Known Member

    Great thread & a sticky on day one.:D
    Thanks & congratulations;) .
  6. nils

    nils Well-Known Member

    No definitely talking about a pop top. The T3 westy roof is flocked on the inside of the poptop, apparently the texture helps with condensation? Stone guard is an interesting suggestion, will look into that.

    Thanks mate

    Haven't you heard Grant? Flock is making a comeback!
  7. oldman

    oldman Super Moderator Staff Member

    Avalon Beach NSW
    Nice one Col.
    This will help a lot of us with aging pop-tops ;)
  8. cbus

    cbus Well-Known Member

    sunshine coast
    Will continue with full details and painting but its something anyone with a bit of nouse can do.
    Hopefully less housepaint versions:eek:
    New ones are available at about 4k.
    They are much improved over originals and nice upgrade for a kombi.
    The bloke who does them used to restore tops but faced the usual issue of never really being happy due to faults in the original product so made his own plug and sorted any issues.
    In general most minor to average repair n paints by many usualy cost 2-2.5k. And not always a good job.
    Its difficult for a panel shop to choose where to draw the line on a non standard job like this.
    Some look at it as easy bucks and the results from poor prep show.
    Customers don't often understand how much work can be in improving existing defects.
    This way owners can put the effort in for a good finish or only have themselves ti blame if they rush it ;)
    David H likes this.
  9. peter915

    peter915 Active Member

    Sunshine coast
    Great write up Collin !:cool:
    Go to the front of the class!

    I was wondering- I am in the process as I write this of restoring a pop-top roof I brought last month for my T3.
    Should post a whole bunch of photos here or start another thread?
  10. cbus

    cbus Well-Known Member

    sunshine coast
    Photos always good Peter.
    As long as you do it correctly ;):D.
    Just kidding.
    Plenty of ways to approach it .
    I'll get on to the painting stage blurb soon.
    How's your project going?
  11. peter915

    peter915 Active Member

    Sunshine coast
    My Syncro Project is slowly coming along.
    The van is now complete with finished under-coat, blocked and ready.
    All seams are filled. With still a few to under-coat and rub back.

    I was literally going to spray the T3 roof with final top coat when I came across Alex's pop-top for sale via FB (T3 group)
    We brought the roof back from Byron Bay on top of the Caddy.

    The roof had come from a South African T3, so the roof could be SA or European origin ?
    I know the lifters are unlike pop-top lifters used here in Oz

    I'm basically stripping the PT right back to basics, including the lifters.

    Feel free Collin to use my photo's for your tutorial - I've got broad shoulders

    I've elected to go down the Automotive paint method.
    I went to Kustom Paints and spoke with Peter at length regards the process.
    And as I already have all the paints it seem a pretty simple process.

    After removing all hardware, fittings etc, I washed and blasted the main parts.
    The roof was in quite good condition so I sanded this back with an air driven orbital using 240 grit.
    Cleaned of the under-neath as well.
    Then applied a coat of Wattle etch primer both sides.
    Then about 3 coats Carmaster under-coat primer 2-pack.
    Sanded the top back lightly using 600 grit.
    Wiped all surfaces between coats with wax and grease remover.
    Then applied 3 coats Paraglaz Gloss colour 2-pack

    I still wan't to finish the roof underneath - I'm going to apply a coat of speckle paint here - grey background with about 3 colours speckle - applied around the visible edges - centre section had a roof hood liner - which was tired looking. I'll replace this with something.
    Right now, I am grinding back the base plate - the mould side - cleaning it of all dirt and back to clean fibreglass base.
    Once thats done I am applying a 100mm wide polyester tape around the inside perimeter. Doing this as previous installer had drilled and fixed pop-rivets every 100mm along both sides.
    Plus the front and back are weaken
    So I'm applying the tape completely around all 4x sides
    When thats done - I'll flip the base over, use bog to fill every hole, and finish sanding.
    I've already sanded most of the base top.
    Later this month I have a new canvas sleeve being made. In Blue.

    I'll let the photos tell the story.


    [​IMG] [​IMG] [​IMG]



    Roof - top side sanded - washed and still wet with water

    [​IMG] [​IMG]


    [​IMG] [​IMG]
    Roof - painted - I was pretty happy with the results - a couple of runs which I'll rub off. But happy with the result.
    Good practice Collin. !

    [​IMG] [​IMG]

    Roof Base washed and cleaned
    [​IMG] [​IMG]

    Damage to the base

    [​IMG] [​IMG]

    Base - damage

    [​IMG] [​IMG]

    [​IMG] [​IMG]

    Mould side - this I am currently stripping back some 150mm in from all edges.
    Using a 115mm angle grinder with flexible rubber backed discs 120 Grit.
    Wearing total coverage overalls, glasses, respirator, ear muffs. Plus

    Large 90cm workshop fan blowing over me while I work.
    Dirty work

    More photos to come
    grantw likes this.
  12. Luckyphil

    Luckyphil Well-Known Member

    When you get the canvas done suggest you have a zippered window put in so you can access the front roof load area from inside the van. Much easier than doing it outside.
  13. cbus

    cbus Well-Known Member

    sunshine coast
    Photos always good to encourage and give the visual aspect Peter.
    Looks good.
    The advantage of marine paint for me is purely economic plus I'm used to it.
    Advantage of auto paint is easier sanding of primers and quicker drying so less bugs and runs.

    I would choose epoxy over polyester for the repair but both will work.
    If space allowed, bedding in metal washers using glue powder or tape would prevent crush on the mount points rubber washers backed by metal and a crush tube may also help.

    I would add that for someone in the habit of going bush and driving under low hanging trees , the harder marine paints like croda or jotun Imperite give much better scratch resistance.
    An alternative for people getting annoyed with stone chips to front panels as well?
    Some can be tinted to a fair range of formulas or are compatible with existing tint systems.
    Last edited: Jan 16, 2018
  14. mackaymanx

    mackaymanx Active Member

    This is the one I'm hoping to salvage, looks to be the same as your's Peter. Will be following this closely.

  15. cbus

    cbus Well-Known Member

    sunshine coast
    Do these rooves come up very often?
    What sort of price range?
  16. mackaymanx

    mackaymanx Active Member

    Not often, you have to be in the right place at the right time. Bay windows tops come up all the time but not the T3s. Prices will vary.
  17. mackaymanx

    mackaymanx Active Member

  18. peter915

    peter915 Active Member

    Sunshine coast

    Brent - well bugger me !!!
    What are the chances of that - yes - I agree - its the same roof.
    How was your roof fasten down to the vehicle Brent?
  19. cbus

    cbus Well-Known Member

    sunshine coast
    Think I need to veer away from another kombi sitting in the yard ;)
    oldman likes this.
  20. mackaymanx

    mackaymanx Active Member

    About 20+ s/s screws around the perimeter of the hole in the roof. There is a roughly 40mm x 25mm piece of wood fiberglassed into the corresponding area in the poptop for them to screw into. They come up from underneath, they distort the metal of the roof slightly as they pull up. But you don't get to see that once finished.

    You can just see a hole in this photo from when I removed it.
    p.s. that is the van you have in the background.


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