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Fibreglass cracks....

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    Fibreglass cracks....

    I'd be grateful for any tips for surface cracks on the roof of my Microlite please, and a few places elsewhere ? I wondered if there was some kind of tube equivalent to fill the cracks - they look like simply the outer smooth surface is starred, and fairly thin. Haven't got up on a ladder for a close inspection yet, that's to come, but have a good view from the bedroom window .......

    They seem to be around where the bolts for the poptop grab handles come through, so could be from over-tightened bolts - I've got a new set of plastic domed covers and washers to fit, which are missing on the two concerned, so thought I could do something about the crackles, and replace the bolts while I'm at it.

    There's also a few places on the body could do with a bit of a tidy - some of the same surface cracks in a couple of small areas, and a few little scrapes and minor grooves that look like they came from roadside bush/branch encounters !
    But nothing looks too serious, the roof is the worst, but I think that's probably more cosmetic than structural, but would be a good preventative measure to prevent water etc... seeping in.
    Better to get it early - might even replace the poptop catches while I'm at it, they are bent about a bit, over 20 years of minor hamfistedness !

    [And the gas locker lid could do with a rub-down and respray/paint, come to think of it - cor, it's the old "once you start" lark again, innit ?]

    Fibreglass (glass reinforced plastic GRP) is created in a hollow mould by first brushing a good layer of relatively thick, high viscosity coloured plastic resin GEL COAT to the mould surface, this is allowed to go off. Next, glass cloth is laid into the mould on top of the Gel Coat and saturated with more of the same resin of a lower viscosity ... which bonds to the Gel Coat. Layers of glass cloth and resin are added until the desired thickness and strength is achieved.

    When the GRP moulding is removed from the mould the gel coat layer becomes the surface you can see and which in your case has cracked. The good news is that small cracks are not generally structurally significant but they can permit water ingress to the underlying structure, and are of course ugly.

    Many folk resolve their problem by having their GRP spray painted, but while specialist GRP repair is possible, it is not really a DIY task for the inexperienced. Suggest a visit to a boatyard to pick brains/ ask advice as a first step, and put 'DIY gel coat repair' into Google for a spot of reading.
    Last edited by mikeroch; 15-10-2014, 08:32. Reason: typo


      When I was messing about with boats I came across tubes of "Crack Repair" for GRP Gel Coat.
      I never tried it so I cannot comment on its value/success.
      However, my car in the picture above suffered damage in collision with a lady when she insisted she was blameless in crossing to my side of the road to pass a parked car because she was "coming through. My proximity going in the opposite direction seemed irrelevent! The insurers supported my account!
      However my GRP front wing seemingly only suffered faint cracks in the surface Gel-coat while the metal on her car was seriously deformed.
      My wing was rubbed down and re-painted to look as new. Unfortunately the "crazeing" soon reappeared through the paint. Successive attempts to paint over the problem has never really sorted it.
      I cannot really tell you how to deal with your problem, but I think it unwise to just try painting over the cracks/crazeing.
      Keeping people waiting is stealing a part of their lives.


        Stress cracks on fibreglass are a nuisance rather than a major problem but if the water can get in then the underlying area can become hygroscopic.

        The correct way to repair is to grind out the crack and fill with a gel coat filler with the right colour pigment in it. It is a real pain and most of us will not do that. Perhaps Captain Tolleys creeping crack sealer may stop water ingress. Whatever you use to repair will need to be flexible or the crack will return.

        Our Romahome was in an accident 6 years ago and we are just starting to see cracks where the repair was completed but the area does have ths strain of the lower rear door hinge.



          Had a chat with a crash repair shop guy - he said clean the cracks out as much as poss with non-wax cleaner, wash off well, dry.
          Then, if cracks are large enough, carefully " scour out" with fine sandpiper, not going too deep, just to clean and roughen slightly. Otherwise, try a needle or fine tip to just scarify a bit. ( If still too small ... forget it and just wax polish a lot, or even vaseline, and keep an eye on it ! )

          When/if cleaned out, use Plastic Padding Gelcoat Filler in layers, finely sanding down each until looks OK - then polish like mad and keep waxed regularly.

          He didn't think it was structural at all, but should be waterproofed, and as it's only a small area, and on the roof out of sight, colour matching isn't too critical, so "a careful amateur can get a reasonable result" - sounds a fair assessment of me, anyway.......... he did smile as he said it ! Also that it might need doing again, depending on the weather extremes it goes through.
          Also added that anything structural, or major cracks that go beyond the gel coating, are almost always the result of consistent stress, not a good idea, and should at least be checked professionally.

          So with mine, it seems a job that is a good idea to do, and within my scope.
          Obviously, sunny/dry weather or indoors a good idea - or buy that cover I've been putting off getting, and hibernate 'till Spring ....
          Last edited by rugmike; 15-10-2014, 11:08.


            I have used the gel coat filler, it comes as white and so is not immediately obvius. The trick is to jet the crack clean and dry. I used a dremel tool with a pointy end to open the crack into a V to put the filler in. The bodyshop guy is right, just keep polishing.

            Sit down when you order the tube of fjiller though.

            Good luck



              Originally posted by peterholden View Post
              I have used the gel coat filler, it comes as white and so is not immediately obvius. .................................................. .....Sit down when you order the tube of fjiller though.
              Good luck
              Yes, thanks Pete, for the confirmation re: that advice - and, yes, I've already done that sitting down exercise !!


                Sorry Mike, I couldn't resist the temptation!

                Originally posted by rugmike View Post
                carefully " scour out" with fine sandpiper, not going too deep
                One like this?


                As against ... for Jim's benefit ... one like this that has been drinking from the dregs of discarded beer cans, hanging out all night with some rough old birds and generally carrying on in a dissolute manner. It might seem like a good idea at the time but it catches up with you in the end.

                dead sandpiper.jpg
                Last edited by mikeroch; 16-10-2014, 08:55.


                  Originally posted by mikeroch View Post
                  One like this?

                  Well that one looks "fine" Mike! But what does a "coarse" one look like?
                  Keeping people waiting is stealing a part of their lives.


                    Carpe diem! :)


                      to all the above ................

                      This thread has what I believe could be termed "morphed" !!!!!

                      Excellent !

                      However, I am extremely interested in this "rough old bird" situation ....... ummm ........... these can be spotted where ?

                      And is nestling .... oops .... nesting involved ?

                      (And can they be found in more of a discarded wine bottle (claret preferably) location ?)

                      Ermm ..... Purely out of ornithological interest you understand .....


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