Glass fibre preparation
Discussion
Hi all
Im looking for a bit of advice from people that paint fibreglass.
I have done some mods to the rear end of my glass fibre car (noble) and i'm really looking to get some realistic advice about how best to prep the panel before it goes for pro painting.
Im thinking it needs to go through a few serious heat cycles before its primered and then painted.... should I be asking for the guy to stick it in the corner of his oven for a few weeks before I fill and primer it?
The reason Im worried is I have a friend who had his fibreglass car painted after he did mods on it and it ended up with lines and ripples all over the place and I definatelly dont want this on my car.
Many Thanks
Im looking for a bit of advice from people that paint fibreglass.
I have done some mods to the rear end of my glass fibre car (noble) and i'm really looking to get some realistic advice about how best to prep the panel before it goes for pro painting.
Im thinking it needs to go through a few serious heat cycles before its primered and then painted.... should I be asking for the guy to stick it in the corner of his oven for a few weeks before I fill and primer it?
The reason Im worried is I have a friend who had his fibreglass car painted after he did mods on it and it ended up with lines and ripples all over the place and I definatelly dont want this on my car.
Many Thanks
Whenever we had a fibreglass car or component we wouldn't let it anywhere near the bake cycle on the oven after primer or basecoat.
Fibreglass is porous and will contains some moisture, when you bake you can't guarantee which side the water is going to try and escape from. The bubbles as it tried to escape through your fresh basecoat was never nice to see
We never pre-dryed the panels, because you still couldn't guarantee that all the moisture was gone, therefore you wouldn't bake it anyway, so there was no net benefit.
Fibreglass is porous and will contains some moisture, when you bake you can't guarantee which side the water is going to try and escape from. The bubbles as it tried to escape through your fresh basecoat was never nice to see
We never pre-dryed the panels, because you still couldn't guarantee that all the moisture was gone, therefore you wouldn't bake it anyway, so there was no net benefit.
apguy said:
Whenever we had a fibreglass car or component we wouldn't let it anywhere near the bake cycle on the oven after primer or basecoat.
Fibreglass is porous and will contains some moisture, when you bake you can't guarantee which side the water is going to try and escape from. The bubbles as it tried to escape through your fresh basecoat was never nice to see
We never pre-dryed the panels, because you still couldn't guarantee that all the moisture was gone, therefore you wouldn't bake it anyway, so there was no net benefit.
You're wrong mate,fibreglass isn't porous.....unless you are talking about boat hulls submerged in water for a long time where moisture can get into it (it's called osmosis)Fibreglass is porous and will contains some moisture, when you bake you can't guarantee which side the water is going to try and escape from. The bubbles as it tried to escape through your fresh basecoat was never nice to see
We never pre-dryed the panels, because you still couldn't guarantee that all the moisture was gone, therefore you wouldn't bake it anyway, so there was no net benefit.
What you get is pockets of air trapped during the laying up process which if exposed to high temperatures.....a hot sunny day can cause this...can find their way out thru the paint,which is why it's recommended that newly laid up grp bodies are left outside for a few months to acclimatise and therefore minimize any risks once the paint has been applied.
As I said before baking isn't recommended
Absolutely DON'T allow a full bake cycle on any GRP.
If you are concerned that there is moisture in the GRP, then the best solution is simply to allow the stripped panel/panels to dry out in a warmed garage/area.
The reason your friend ended with ripples/lines all over his car could be for any number of reasons - not least that the car was fully baked! But also that any filler/repair work wasn't allowed to settle over time before priming; primer wasn't allowed to settle over time etc, etc. I would place money on the car having been done by an 'accident repair' type company who can't afford/aren't geared up to allow this type of work to be done.
As an example I always cite the famous Ferrari CS stripe issue - it is a vinyl stripe, fitted to an aluminium panel & painted over with a 2k HS clear. All of these materials have a differing heat absorbtion rate & this causes cracking & deformation in the top clearcoat over many heat cycles - whether they be oven induced or 'life' induced.
PATIENCE IN WORKING PRACTICE & PROCESS IS ALL.
Hope this helps, Al.
If you are concerned that there is moisture in the GRP, then the best solution is simply to allow the stripped panel/panels to dry out in a warmed garage/area.
The reason your friend ended with ripples/lines all over his car could be for any number of reasons - not least that the car was fully baked! But also that any filler/repair work wasn't allowed to settle over time before priming; primer wasn't allowed to settle over time etc, etc. I would place money on the car having been done by an 'accident repair' type company who can't afford/aren't geared up to allow this type of work to be done.
As an example I always cite the famous Ferrari CS stripe issue - it is a vinyl stripe, fitted to an aluminium panel & painted over with a 2k HS clear. All of these materials have a differing heat absorbtion rate & this causes cracking & deformation in the top clearcoat over many heat cycles - whether they be oven induced or 'life' induced.
PATIENCE IN WORKING PRACTICE & PROCESS IS ALL.
Hope this helps, Al.
Ok so no baking of the car
The person painting the car is a recomended local garage who specialise in restoring cars including a lot of old grp cars... he doesnt exactly rush his work and I dont think he does accident repairs.
The reason Im concerned is that I have modified the clam by cutting sections out and then making up new parts, this is a piece by piece process so its not a complete one piece section.
I am not overly worried about adding 2-3kgs over how light the panel could be, Im just worried about the end finish being right.
Basically the panels are entirely made from 450gr matt with resin, I have ground it down intergrated it into the existing body very throughly, I am going to now grind the top down and matt over the join on the top as well probably with tissue to try to avoid allowing air bubbles or cracks coming through.
Question is this going to be good enough and should I cover the panels with gel coat and sand it flat then have it finished in high build primer?
The person painting the car is a recomended local garage who specialise in restoring cars including a lot of old grp cars... he doesnt exactly rush his work and I dont think he does accident repairs.
The reason Im concerned is that I have modified the clam by cutting sections out and then making up new parts, this is a piece by piece process so its not a complete one piece section.
I am not overly worried about adding 2-3kgs over how light the panel could be, Im just worried about the end finish being right.
Basically the panels are entirely made from 450gr matt with resin, I have ground it down intergrated it into the existing body very throughly, I am going to now grind the top down and matt over the join on the top as well probably with tissue to try to avoid allowing air bubbles or cracks coming through.
Question is this going to be good enough and should I cover the panels with gel coat and sand it flat then have it finished in high build primer?
The usual process would be to use body filler to smooth out the join and then a good 2k primer.
How were you intending on applying the gel coat ? Gel coat usually goes on 1st,in the mould, before the laminating,what you are thinking of doing is the exact opposite.Gel coat isn't supposed to be applied open to the atmosphere
How were you intending on applying the gel coat ? Gel coat usually goes on 1st,in the mould, before the laminating,what you are thinking of doing is the exact opposite.Gel coat isn't supposed to be applied open to the atmosphere
I didnt have a mould.... Im not 100% certain but i dont think there is any issues with gel coat drying without being covered by resin and matt? I know gel coat finished cars (ie unpainted) can have repairs with just grinding down the surface or crack and then filling with new gel coat and then sanding down.
The only issue I am aware of is that gel coat is significantly harder than filler and thus takes a lot more work to sand and flat???
The only issue I am aware of is that gel coat is significantly harder than filler and thus takes a lot more work to sand and flat???
There's a big difference between filling in a crack with gelcoat and spraying a complete new coat on the top.
From the small amount of research I've done I'm led to believe it's not a wise move....I was thinking of doing a similar thing myself at one point,over an entire bodyshell.....it's not like spraying paint.
You are right about 1 thing,it will be hard to rub down !
From the small amount of research I've done I'm led to believe it's not a wise move....I was thinking of doing a similar thing myself at one point,over an entire bodyshell.....it's not like spraying paint.
You are right about 1 thing,it will be hard to rub down !
If you add in wax (or buy pre waxed gel coat) it is fine to apply on top... apparently some repairers actually prefer to use resin rather than filler to prevent long term shrinkage of filler.
It would be painted on and then sanded down, harder than filler for sure but if it ends up with a better result in the long term then im prepared to go this route.
Trouble is like you its all theory to me,hence i'm asking so many questions.
It would be painted on and then sanded down, harder than filler for sure but if it ends up with a better result in the long term then im prepared to go this route.
Trouble is like you its all theory to me,hence i'm asking so many questions.
tommobot said:
Bit of a bump....
Thinking of doing a similar thing with gelcoat / topcoat over a front \ rear clam that I have modified in parts..
Is it possible to spray on, or is it a hand paint job, will this still give a decent finish?
https://www.youtube.com/watch?v=1HaZEzEfmncThinking of doing a similar thing with gelcoat / topcoat over a front \ rear clam that I have modified in parts..
Is it possible to spray on, or is it a hand paint job, will this still give a decent finish?
Top result: Google.
You need a special gun and it splatters on in blobs.
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