32 replies to this topic

[slindborg]

Having read up a little on GRP blistering and osmosis over the apst few weeks I've come to the conclusion that 90% of vx clam blistering isnt actually down to the GRP going funny. http://www.yachtsnet.co.uk/osmosis.htm I know my doors have got proper GRP based blistering as the fibres are "on show" from where the scabs were removed. But upon inspecting regular paint bubbles on the clams it just looks like its the paint thats gone and not the clam. This implies its just a repaint job and not a reclam job. Aside from the small chance of getting water into the GRP with emulsion bound glass when the cheese eating surrender monkeys made the clams, there is no real way water can get into the GRP to then require what you lot claim as "drying out" (I know that link says water can get into the GRP once made but thats different). Given the thickness of the VX clams its unlikely that the tiddly bubbles we see are really GRP damage. So seemingly the fix for blistering if its actually got fibres on show is to steam clean the wound and fill with resin/glass paste (not car body filler), and if its just plain ole bubbles with no GRP damage then its most likely to just need repainting. discuss

[p4cks]

I concur.

[Zoobeef]

I just know its damn ugly If it is just the paint why does it do it?

[Mr Tidy]

My old man's been a yacht repairer for 36 years. After discovering a couple of bubbles and areas where paint was starting to lift on my recently purchased VX I suggested to him it might be osmosis – he couldn't stop crying with laughter for five whole minutes. I thought I'd killed the b*stard!! From this reaction I concluded that it may not be osmosis after all...

[slindborg]

it sort of is and isnt from what I can work out. It mostly sounds like sh** paint prep causing areas of poor bond to let water sit and do its thang without going into the grp.

[turbobob]

Fibreglass is a porous material, and can therefore absorb moisture. When fibreglass is exposed to heat (e.g. direct sunshine) and there is moisture in the fibreglass, the moisture evaporates which results in blistering. Additionally, if there is moisture in the fibreglass, and it freezes, the moisture freezes and expands also resulting in blistering. This would suggest the clams weren't stored very well before painting and / or the gel coat (the layer to protect from moisture absorbtion) is crap. I think the use of the phrase 'osmosis' isn't correct in this context.

[Mr Tidy]

it sort of is and isnt from what I can work out. It mostly sounds like sh** paint prep causing areas of poor bond to let water sit and do its thang without going into the grp.

I'm no expert but that sounds about right to me. A couple of my bubbles have broken and flaked off and it's left a deep hole in the gel coat – but cant see any of the glass. Like you said, I'm just gonna top it up with resin, then possibly try and blend it in with touchup paint and the Langka touchup solution. When this looks a pile of sh** I'll stop being so tight and pay a professional to do it!!

[redvts]

I have a bit on my rear clam, it's directly on top of where the seam is underneath (around the boot hatch) the bubbles follow the seam in straight lines, the boot hatch must be bonded to the clam as the hatches r different on the na and the turbo this allows one shape clam to be made for both models, anyway it looks like moisture has got into this seam and caused the bubbles I must admit I don't know much about this and could be wrong

[turbobob]

it sort of is and isnt from what I can work out. It mostly sounds like sh** paint prep causing areas of poor bond to let water sit and do its thang without going into the grp.

I'm no expert but that sounds about right to me. A couple of my bubbles have broken and flaked off and it's left a deep hole in the gel coat – but cant see any of the glass. Like you said, I'm just gonna top it up with resin, then possibly try and blend it in with touchup paint and the Langka touchup solution. When this looks a pile of sh** I'll stop being so tight and pay a professional to do it!!

Gel coats are a thin a thin layer, so I doubt its left a deep hole in just the gel coat.

However. Whilst the use of resin as a protective layer to prevent absorbtion of water is good, unless you treat the area before hand, there is a chance it will come back. Basically the area needs stripping back, then baking to evaporate any remaining moisture, then re-fibreglassing (if necessary), then applying the gel coat / resin before prepping for paint.

Edited by turbobob, 23 March 2010 - 05:09 PM.

[Mr Tidy]

it sort of is and isnt from what I can work out. It mostly sounds like sh** paint prep causing areas of poor bond to let water sit and do its thang without going into the grp.

I'm no expert but that sounds about right to me. A couple of my bubbles have broken and flaked off and it's left a deep hole in the gel coat – but cant see any of the glass. Like you said, I'm just gonna top it up with resin, then possibly try and blend it in with touchup paint and the Langka touchup solution. When this looks a pile of sh** I'll stop being so tight and pay a professional to do it!!

Gel coats are a thin a thin layer, so I doubt its left a deep hole in just the gel coat.

However. Whilst the use of resin as a protective layer to prevent absorbtion of water is good, unless you treat the area before hand, there is a chance it will come back. Basically the area needs stripping back, then baking to evaporate any remaining moisture, then re-fibreglassing (if necessary), then applying the gel coat / resin before prepping for paint.

I know the guys on here sing the praises of people like Chipsaway but have they got the knowledge to sort areas like this out?? I've no doubt they understand paint but it's whether they understand fibreglass too. Has anyone had these problem areas fixed by people like Chipsaway before and had any problems with the result??

[techieboy]

I know the guys on here sing the praises of people like Chipsaway but have they got the knowledge to sort areas like this out??

Never seen anyone here sing the praises for Chipsaway.

Personally, I wouldn't go anywhere near them or their ilk unless I was sure they knew what they were doing. Anything they do is just a temprary fix anyway, IME.

[smithers]

I have a bit on my rear clam, it's directly on top of where the seam is underneath (around the boot hatch) the bubbles follow the seam in straight lines, the boot hatch must be bonded to the clam as the hatches r different on the na and the turbo this allows one shape clam to be made for both models, anyway it looks like moisture has got into this seam and caused the bubbles

I must admit I don't know much about this and could be wrong

/devils advocate/ could it not be that the clam is just flexing along this crease, and that has caused the paint to bubble up under the flexing along this line?

My bodywork doesn't have any bubbling and as far as I know, it was left outside in London for the first 3 years of its life, then garaged by me for 4 years, albeit in a slightly damp garage... each approach has made bugger all difference to whether it has bubbled or not.

Poor prep sounds as reasonable an argument as any though

no help but there you go

[Mr Tidy]

I know the guys on here sing the praises of people like Chipsaway but have they got the knowledge to sort areas like this out??

Never seen anyone here sing the praises for Chipsaway.

Personally, I wouldn't go anywhere near them or their ilk unless I was sure they knew what they were doing. Anything they do is just a temprary fix anyway, IME.

I've stumbled across a couple of threads where they're mentioned – I've always been sceptical because they'll rarely come across GRP. Have you had problems with them then??

[southpaw]

Is it right to say that all bubble cases are when the car has been left outside, but not all cars left outside bubble - ie those that had proper paint prep done. ?

[Mr Tidy]

Is it right to say that all bubble cases are when the car has been left outside, but not all cars left outside bubble - ie those that had proper paint prep done.

?

Mine sits outside and the guy who had it before me kept it outside too. I think the winter from hell has taken its toll!! It's not horrendous and, getting back to the point of the thread, I don't think it's poorly laid glass, just crap paint...

[redvts]

I have a bit on my rear clam, it's directly on top of where the seam is underneath (around the boot hatch) the bubbles follow the seam in straight lines, the boot hatch must be bonded to the clam as the hatches r different on the na and the turbo this allows one shape clam to be made for both models, anyway it looks like moisture has got into this seam and caused the bubbles

I must admit I don't know much about this and could be wrong

/devils advocate/ could it not be that the clam is just flexing along this crease, and that has caused the paint to bubble up under the flexing along this line?

My bodywork doesn't have any bubbling and as far as I know, it was left outside in London for the first 3 years of its life, then garaged by me for 4 years, albeit in a slightly damp garage... each approach has made bugger all difference to whether it has bubbled or not.

Poor prep sounds as reasonable an argument as any though

no help but there you go

u could be right I have no Idea all I know is that it's got something to with the seam, well on mine anyway

[FLD]

Whats missing here is that its not 'proper' fibreglass. The clams are made in closed moulds with fibre inside and then plastic is injected in from one side only. (thanks renault!). This gives the appearance of regular fibreglass. The fibres dont properly wet out in these sorts of mouldings. The fibre is there to stop the brittle plastic busting apart. I'm not sure if the fibres that aren't wet out provide some sort of wick for moisture to lift the paint. I do know paint prep on this sort of finish is a ball ache. You need adhesion promotor and plasticiser to get it to stick properly which I believe is often missed. Could always bake it to dry it, then use an epoxy sealer followed by paint. I hate painting laminates.

[turbobob]

What I am saying (and I don't have all the facts, but I a making a suggestion based on the evidence to hand) is that when the cars / clams were manufactured, there must have been an opportunity for them to absorb moisture. This could be because they were stored outside or maybe a damp / humid warehouse etc. Then after painting, and over time and exposure to extreme cold / high temp, the previously absorbed moisture will expand / evaporate causing the blistering. To eliminate future blistering, the affected areas need the paint and gel coats stripping back and then baking to remove any further moisture in the fibreglass. Once baked the area then needs repairing (if needed) then the gel coat / resin applying again (the gel coat / resin is essentially the protective layer preventing moisture abosorbtion into the fibre glass) before paint. Any ChipsAway repair is as suggested only a temporary fix. The underlying cause, i.e the moisture in the fibreglass is still there (or at the very least still likely to be there). So again after exposure to cold / heat, it is highly probable the blistering will return.

Edited by turbobob, 23 March 2010 - 06:12 PM.

[Mr Tidy]

What I am saying (and I don't have all the facts, but I a making a suggestion based on the evidence to hand) is that when the cars / clams were manufactured, there must have been an opportunity for them to absorb moisture. This could be because they were stored outside or maybe a damp / humid warehouse etc. Then after painting, and over time and exposure to extreme cold / high temp, the previously absorbed moisture will expand / evaporate causing the blistering.

To eliminate future blistering, the affected areas need the paint and gel coats stripping back and then baking to remove any further moisture in the fibreglass. Once baked the area then needs repairing (if needed) then the gel coat / resin applying again (the gel coat / resin is essentially the protective layer preventing moisture abosorbtion into the fibre glass) before paint.

Any ChipsAway repair is as suggested only a temporary fix. The underlying cause, i.e the moisture in the fibreglass is still there (or at the very least still likely to be there). So again after exposure to cold / heat, it is highly probable the blistering will return.

Bad times...

[slindborg]

and simply getting a 'new' clam wont necessarily fix it either as they might have been stored poorly or with the non wetting out of the fibers let water wick through a treat. I'd imagine even ripping the gel coat off and drying wont fix it given then thickness of the grp. obv freezing will blow any water bubbles out, but it definitely appears warm weather is a bigger problem for causing the water to move around, so Summer is worse than Winter lmao. so no real solution other than to clean out round the bubble, steam it out and then dry, fill with an epoxy stopper/filler and refinish.