boxer1 Posted March 8, 2014 Share Posted March 8, 2014 I own an Auto Trail Cheyenne 1998. I have found a pimple effect on the fibre glass front and rear panel, it covers an area of approx. 2" wide by 20" high. I have done nothing different to the van other than polishing it with marine polish last year. What would cause this Can it be repaired If left would it get worse and start to let water in Boxer1 Link to comment Share on other sites More sharing options...
Basil Posted March 8, 2014 Share Posted March 8, 2014 Only time I've seen this happen is when either GRP or the other plastics that various automotive parts are made from have been repaired and resprayed whilst there was either water or thinners or other liquid still in the part being sprayed or the weather was damp when the spraying occurred. That phenomena is known as microblistering and is described in the following article (though the picture is far worse than I have personally seen) see http://www.hmgpaint.com/knowledge-base/blistering-the-causes-and-prevention If you Google 'microblistering in automotive paint finishes' there are numerous articles on the subject. I had my worst encounter with this on a GRP hardtop made by Truckman, the top was replaced four times by them but still the last one went the same way and I have it to this day. Bas Link to comment Share on other sites More sharing options...
globebuster Posted March 8, 2014 Share Posted March 8, 2014 If the GRP has never been painted and the original gelcoat, then the chances are you probably have a mild case of osmosis. Or as Basil has explained, if painted, you may have microblistering or possible solvent entrapment. A few questions - Can you press the pimple, does any fluid come out? Is the van covered during storage? Is it parked adjacent to any moisture retaining substrate - Ie a wall, with poor air circulation? What kind of polish did you use? The chances of suffering any ingress is pretty limited I would imagine. Difficult to make an accurate appraisal without viewing. Link to comment Share on other sites More sharing options...
Guest peter Posted March 8, 2014 Share Posted March 8, 2014 I will reply when more info' is available. As requested above. Link to comment Share on other sites More sharing options...
boxer1 Posted March 9, 2014 Author Share Posted March 9, 2014 The vehicle has not been sprayed or repaired from I purchased it 2005.Bas looked at your web page the spots on my vehicle would be smaller approx. 1-2mm diameter and no liquid comes from them when squeezed in fact they are solid. The vehicle is in a purpose built carport. It is sheeted on the west side and rear which does not cover all the way to the ground, the east side and front are open which lets plenty of air around the vehicle. The damage on the vehicle is only on the east side as she sits and this side would not get any sun, not sure if this would matter. In the summer I polished the vehicle with 3M marine cleaner & wax which was a great job.Previously the GRP had a dull yellow finish and no matter what other polishes I used they didn't do as good a job as 3M. My own suspicions was either the polish or damp on the inside. I have checked the vehicle and can find no damp and the polish if it is used on boats all the time then why would it cause this damage to my vehicle. It would be a great help if I could attach a photo but not very good at the computing, just know how to switch on. Boxer1 Link to comment Share on other sites More sharing options...
Basil Posted March 9, 2014 Share Posted March 9, 2014 Sounds like the ones on my hardtop, I said the picture on that site was much more severe! The ones on my top have no liquid in when burst either so I am not sure that is necessarily an indication. As you have had no spraying or repairs carried out then that seems to rule that out so the only other thing that I have seen on GRP boats is called Osmosis as someone I believe suggested earlier see http://www.yachtsnet.co.uk/osmosis.htm hope you get to the bottom of it. Bas Link to comment Share on other sites More sharing options...
boxer1 Posted March 9, 2014 Author Share Posted March 9, 2014 Thanks Bas for your help. It would appear that my van has "OSMOSIS" your web page is all about boats that are in the water for long periods of time which can cause the problem. Slightly confused as my van is not in the water maybe it happened last year when I was in France in May and it rained everyday for 4 weeks. The good side to it all is that the GRP will still keep the water out and it is only water getting below the gel coat and no further. I am still confused as to why it has occurred to my van as it is under cover and not wet all the time. With the east side of the carport open there does not be a lot of weather getting at the van and it is open which should dry any water off. It is suspicious that it has only occurred now after using the 3M polish. Have I weakened the gel coat letting in water. The web page does say that it can clear in hot weather but come back again if wet. Better not go to France in May this year need to go to the south its warmer. Thanks again for your help. Boxer1 Link to comment Share on other sites More sharing options...
Retread24800 Posted March 10, 2014 Share Posted March 10, 2014 Lots on Osmosis here PBO Search . Looking forward to a chance of rain on the 18th here in the middle of France B-) Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 11, 2014 Share Posted March 11, 2014 This Caravan Club forum thread discusses a similar problem http://www.caravanclub.co.uk/community/discussions/technical-and-advice/caravans/grp-front-panel-goose-pimpling/rt/210500/ Link to comment Share on other sites More sharing options...
boxer1 Posted March 12, 2014 Author Share Posted March 12, 2014 Thank you all for your advice and help I don't know what one would do without the site. My main concern was would it let in water. From reading all the different information, that's not going to be a problem. My van is 14yrs old so things like this are expected. Its great that the weather is good in France, From talking to the locals, last year was different from the norm. Thanks again for the advice. Boxer1 Link to comment Share on other sites More sharing options...
hallii Posted March 12, 2014 Share Posted March 12, 2014 Just a thought, whatever the cause, a good paint sprayer could rub it down and give a couple of coats of two pack paint, on top of an isolating filler primer. That should last the lifetime of the van. It shouldn't cost a fortune either. H Link to comment Share on other sites More sharing options...
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