fiberglass on back of MC8

rcbeam · June 03, 2011, 05:20:33 PM

I bought a heat gun, heated and scraped all the lettering off of the rear "window" fiberglass panel of my MC8. The heat gun/scraper also removed some pieces of what seems to be several layers of paint and I think I gouged it in a few places too. My questions are:

1. What can I fill in the gouges with and smooth out places where different paint layers were removed?

2. What do I clean the whole area with and also remove residual adhesive from the lettering?

3. After I repair the fiberglass what do I paint with temporarily until I have the whole coach painted?

Anybody else gone through this process?

Thanks for you guys help.

robertglines1 · June 03, 2011, 05:26:53 PM

cheap lac thinner is what I used. takes glue off. then treat like any other surface just fill with spot filler sand and prime and await painting.

rcbeam · June 04, 2011, 07:03:55 AM

That sounds fairly simple... I've never worked with fiberglass before. For some reason I think it's my nature to make things more complicated than they are. Thx for the info.

We've finally had a week without rain... another sunny dry week in the forecast for next week.

Call me, "dryin out in KY".

luvrbus · June 04, 2011, 07:11:54 AM

If you sand or have gouges past the gel coat that needs to repaired if not when you paint most of the time it will have tiny bubbles in the paint at least that the problem I have with fiberglass

good luck

rcbeam · June 04, 2011, 09:20:01 AM

Thx Luvrbus. I think one or two gouges may be past the paint. So can I fill these with bondo?

Jeremy · June 04, 2011, 10:51:52 AM

Quote from: rcbeam on June 04, 2011, 09:20:01 AM
Thx Luvrbus. I think one or two gouges may be past the paint. So can I fill these with bondo?

As luvrbus says, it's not going through the paint that matters, it's going through the gelcoat. The gelcoat is the outer layer of the fibreglass, and consists of a layer of fibreglass resin (only) that sits on top of the resin/glass layers underneath. There's no problem at all in simply filling some small gouges in the gelcoat with filler before painting everything as normal.

If a larger area of gelcoat is removed (eg by sanding) it can be advisable to seal the surface with a new coat of resin (sometimes called a flow coat) before proceeding. Although regular high-build primer ('primer filler' or 'spray putty') will often suffice to fill the pinprick holes which often exist in the resin/glass layers.

Incidentally (and a small bug-bear of mine) - some people refer to flow-coating as re-gelcoating. This is technically wrong as flowcoating is done with regular resin, not gelcoat resin, which can only be used in moulds (gelcoat resin has wax added so that it 'gels' but never fully cures in the open air. This makes it bond to the next layer of resin in the mould, but means it cannot be used for any other purpose).

Jeremy

chev49 · June 04, 2011, 10:55:47 AM

i would not fill them with bondo...do what the others suggest abt the gelcoat
However, in some corvettes i have bought at the auction for resale, i have seen lots of bondo when repairing the body problems...

Jeremy · June 04, 2011, 11:50:56 AM

'Bondo' is often seen as being an cheap / inferior / amateur product, and in some respects it is. It's worth pointing out though that (correctly used) Bondo is entirely suitable for use on fibreglass mouldings, because Bondo is itself fibreglass.

There are all sorts of powders available to mix with fibreglass resin to create materials with different properties - for instance, you can mix carborundum grit with fibreglass resin to create a very tough, hardwearing material. Or you can use different powers to create either non-slip or 'very slippy' surfaces. Or mix in real metal powers to cast 'bronze' sculptures and the like

And of course there are many types of powders for the purposes of bonding and filling. One of the easiest-to-use fillers is created by mixing in magnesium silicate, which is more commonly known as talcum powder. You can buy magnesium silicate in bulk to create your own filler, or you can buy Bondo, which is exactly the same stuff - fibreglass resin mixed with talcum powder.

Jeremy

gus · June 04, 2011, 02:10:21 PM

Get a small can of resin at WM in the auto body repair section, mix it in small quantities and apply sparingly with a small brush. You may have to buy a small repair kit but it is still the cheapest way to go. This will seal the gouged fiberglas.

Then spray it with epoxy appliance enamel (if your bus is white). I don't think it comes in any color except black and white, not even sure about black. I put this stuff on the nose of an airplane and it never flinched in the five years I owned it.

rcbeam · June 04, 2011, 05:54:37 PM

Jeremy, you seem to know your stuff about fiberglass. Gus, I never thought about WM having fiberglass repair kits, but that may just be all I need to fix a couple of places. Gus, you also brought up a good point that I haven't covered yet and that is repainting... it is currently black. I'll not be in a position to paint my bus for a while yet as I have too much other stuff that will have to come first, but in the mean time, I would like to do something to spruce up this back end.

My first thought was just go back with flat black like it is, but that could make the bedroom or back cabinets if I have them hotter in the summer so white would be better.

What color do the rest of you guys paint your back fiberglass area?

Thx so much guys,

bevans6 · June 05, 2011, 04:42:36 AM

Some of the best and most respected Porsche restorers, and a lot of early competition Porsches were all fiberglass bodied, use a high quality bondo for the top finish. You can create your own gel coat, it's not just resin but has a specific filler added to it, and brush it on. If there are cracks in the gelcoat you have to remove it, grind or sand it off until you reach the substrate of glass, then start building it up again. If you leave the original gel coat on, it will simply crack again. There are other fillers that you can add to resin, I use ones from West systems. http://www.westsystem.com/ss/410-microlight/ is a very low density filler that is very easy to work and designed to fair over large areas like the rear cap of a bus. http://www.westsystem.com/ss/406-colloidal-silica/ is neat stuff, it leaves a surface that is a lot harder, and harder to sand out, but it has the neat ability to not run off vertical surfaces. You can add it to the 410 and get something in the middle. I use this with the West system epoxy more often than not, it leaves a very strong finish and bonds well mechanically to the original fiberglass, but i also use them with normal resin when I don't need strength, just a workable finish. In all cases, you want the layer to be as thin as possible - there is no strength in the resin or the finish layer so if it's thick, it cracks very easily.

If I was going to repair what you have, I would sand with 80 grit paper to fair out the gouges, fill with bondo and sand out normally, and have a sign company put a wrap on it. Like wall paper over old plaster, the wrap plastic covers any cracks really quite well.

Brian

gus · June 05, 2011, 01:01:44 PM

Both my fiberglass caps are solid white, the only color that makes sense if you spend any time in the hot sunny climes.

Flat black is probably the worst possible color from the heating aspect, it really sucks up the heat. The best test is to lay your hand on a horizontal white surface on a bright sunny day and then lay it on a black or very dark surface. Do the dark part carefully though!!

If you decide to use the white epoxy appliance white be sure the flat black is well sanded and clean, it really oxidizes badly and the white won't stick if it isn't really clean. My airplane nose was black before I painted it white and even the gloss black paint was in bad shape.