Clearcoat "ribbles"


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Whitesol
Whitesol
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I usually allow at least a 24 hr curing time before sanding and a 48hr or longer gap between the last wetsand and the applying of the clearcoat, to prevent the risk of any moisture still being present.
I've re-cleared these specific parts  and they've been out in the sun  for a full day  allready with no sign of deforming again, so the problem does seem solved :-)

Warren (Staff)
Warren (Staff)
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If it was not properly cured before sanding, you would find the sanding much harder and the resin would clump the paper and almost take chunks out of the surface.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
Lester Populaire
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Whitesol - 9/2/2019 11:05:26 AM
Lester Populaire - 9/1/2019 4:21:00 PM
Whitesol - 9/1/2019 7:55:17 AM
Hi,

I've recently come on to a problem  of which I'd like to know the exact cause, so what better place to ask than here..

I've skinned a few  plastic parts in CF  using the black basecoat & EL epoxy (fast hardener) and everything went as usual .. perfect

I applied an automotive UV resistant clearcoat (by spraygun) and the parts all looked stunning.

Now after a couple of days on the car, we're starting to see and feel  "ribbels" form  that run along exactly with the carbon fibre weave.
I've spoken to a few other people here that are into skinning and all have had the same problem with some parts but cannot explain the cause. They all say  that sanding & re-clearing the part solves the problem, but I'd like to know what causes it.

Some parts were installed on cars that were in the sun, others were  in a garage and have seen no sun .. yet both suffer the same issue

Probably just an issue with shrinking of the resin during polymerization. Make sure it is properly post cured so the glass transition temperature of the resin is higher than what the part will see during use. For automotive parts this can be really rather high...
Consult the technical data sheet of the resin to find curing cycles and the corresponding Tg.


Thanks for your reply, but the part was not exposed to any heat during installation. It was installed on the doors of a garaged car, with the outside temp at max 25 degrees and no sunlight

Can still be that it wasn't properly polymerized before sanding.

Warren (Staff)
Warren (Staff)
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Epoxy resins, although hard to touch after the initial cure, tend to have a slow tail end to the cure which could explain this.

Even on only a moderately warm day, a garage could easily get quite warm into the 30s or higher which may be enough for it to begin to slightly soften in relatively fresh parts.  A post cure will stabilise the material and resin up to the materials HDT which certainly helps with this.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
Whitesol
Whitesol
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Lester Populaire - 9/1/2019 4:21:00 PM
Whitesol - 9/1/2019 7:55:17 AM
Hi,

I've recently come on to a problem  of which I'd like to know the exact cause, so what better place to ask than here..

I've skinned a few  plastic parts in CF  using the black basecoat & EL epoxy (fast hardener) and everything went as usual .. perfect

I applied an automotive UV resistant clearcoat (by spraygun) and the parts all looked stunning.

Now after a couple of days on the car, we're starting to see and feel  "ribbels" form  that run along exactly with the carbon fibre weave.
I've spoken to a few other people here that are into skinning and all have had the same problem with some parts but cannot explain the cause. They all say  that sanding & re-clearing the part solves the problem, but I'd like to know what causes it.

Some parts were installed on cars that were in the sun, others were  in a garage and have seen no sun .. yet both suffer the same issue

Probably just an issue with shrinking of the resin during polymerization. Make sure it is properly post cured so the glass transition temperature of the resin is higher than what the part will see during use. For automotive parts this can be really rather high...
Consult the technical data sheet of the resin to find curing cycles and the corresponding Tg.


Thanks for your reply, but the part was not exposed to any heat during installation. It was installed on the doors of a garaged car, with the outside temp at max 25 degrees and no sunlight

Lester Populaire
L
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Whitesol - 9/1/2019 7:55:17 AM
Hi,

I've recently come on to a problem  of which I'd like to know the exact cause, so what better place to ask than here..

I've skinned a few  plastic parts in CF  using the black basecoat & EL epoxy (fast hardener) and everything went as usual .. perfect

I applied an automotive UV resistant clearcoat (by spraygun) and the parts all looked stunning.

Now after a couple of days on the car, we're starting to see and feel  "ribbels" form  that run along exactly with the carbon fibre weave.
I've spoken to a few other people here that are into skinning and all have had the same problem with some parts but cannot explain the cause. They all say  that sanding & re-clearing the part solves the problem, but I'd like to know what causes it.

Some parts were installed on cars that were in the sun, others were  in a garage and have seen no sun .. yet both suffer the same issue

Probably just an issue with shrinking of the resin during polymerization. Make sure it is properly post cured so the glass transition temperature of the resin is higher than what the part will see during use. For automotive parts this can be really rather high...
Consult the technical data sheet of the resin to find curing cycles and the corresponding Tg.

Whitesol
Whitesol
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Posts: 7, Visits: 15
Hi,

I've recently come on to a problem  of which I'd like to know the exact cause, so what better place to ask than here..

I've skinned a few  plastic parts in CF  using the black basecoat & EL epoxy (fast hardener) and everything went as usual .. perfect

I applied an automotive UV resistant clearcoat (by spraygun) and the parts all looked stunning.

Now after a couple of days on the car, we're starting to see and feel  "ribbels" form  that run along exactly with the carbon fibre weave.
I've spoken to a few other people here that are into skinning and all have had the same problem with some parts but cannot explain the cause. They all say  that sanding & re-clearing the part solves the problem, but I'd like to know what causes it.

Some parts were installed on cars that were in the sun, others were  in a garage and have seen no sun .. yet both suffer the same issue

GO

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