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Discussion Starter #1 (Edited)
Has anyone ever fixed fiberglass?
I have no experience. I have a few cracks in my tub due to previous owner putting the winshild frame on wrong. Drivers side is not cracked through. Where the top of tub meets the hood/vent it is barely cracked under the paint. On passenger side it is cracked all the way through just where the dash meets the door opening and is not sturdy at all. Previous owner attached the windshield frame by using 3 bolts going into the bottom of the windshild on both sides. The winshield is very springy. See pics....does this look fixable. What would be a good plane to follow.
 

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Recovering XJ owner
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It's fixable, but probably won't last. The stress cracks in fiberglass are very hard to repair and will almost always come back if not fixed correctly.

The repair: you basically need to grind from the backside until you get near the surface, but do not grind through. Lay a couple layers of glass, taking note on how thick it is so you don't run into any interference problems remounting the parts being repaired.

Once the backside is done, grind the front side down to the new glass and put down a layer or two, but not going beyond the finish surface. Once it's close let it cure, then putty/bondo in your surface, sand, primer and paint.

Do not lay glass past the surface ... it will not sand down very well. You'll have little hairs sticking out everywhere.

You can get duraglass (basically bondo w/ glass strands in it) from a autoparts store, but for structure you are definitely going to need to add a few layers of glass down as well.
 

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you can also put masking tape on the surface, grind down close to it, laminate it, let it cure, remove the tape and then refinish the surface with a glaze coat.

This would be the easiest way.

I'm sure there's a million ways to get the same results.


edit: I don't know what I was thinking, I wouldn't lay any glass on the surface side in this case, the parts are probably too thin to begin with anyways.

FYI, I did a lot of prototype work at Roush and worked with glass everyday ... it really itches too.
 

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Here is a link to help you.
http://www.boatus.com/boattech/casey/17.htm
I'm sure there is more there.
I know that west marine has some poly fill that can be used on the top for finish of the repaired area that works great. After the subsurfaces are done use poly fill and resin to top coat and sand smooth it is hard to see after painting.

oh fiberglass is firberglass either on a boat or car.
 

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in place of 'grind' would be one of those abrasive roloc wheel things, less 'grinder' more sandpaper type
 

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Only reason I recommended gringing is less dust. Ever use roloc or try and sand fiberglass? not fun. If you mean like 2" roloc that's ~80 or 36 grit mkay, I'll buy it.
 

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Discussion Starter #11
Thanks everybody....very helpful.

I will see if I can get the supplies I need this weekend and start the project. What brand/tools/supplies will I need for this whole project. Also to strengthen the section that has cracked all the way through could I use like 1/4 inch plywood and glass over it.
 

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Thanks everybody....very helpful.

I will see if I can get the supplies I need this weekend and start the project. What brand/tools/supplies will I need for this whole project. Also to strengthen the section that has cracked all the way through could I use like 1/4 inch plywood and glass over it.
At least a 90* grinder w/ an attachment for 2" roloc pads, glass, bondo, sand paper, etc... there's a ton of different brands of this stuff. What ever shop you pick it up from should be able to lead you in the right direction.

If you can glass over 1/4 without interferring with how everything mounts, I'd probably go ahead and use a 1/4" steel plate. Or when I was stiffening structure on different models 1/4 foam board worked too, because the resin from the glass will harden it up.
 

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You might consider West Systems Epoxy for that repair rather than a polyester. They also have fillers to make it thicker and easier to use on verticle surfaces. Using a reinforcement on the back side (if room permits) will give it much more strength but you should sandwich it between 2 wet layers for proper adhesion. Whatever you use (we use 2024 T3 or 7075 aluminum) make sure you heavily etch it with a sand disc and clean real well. When you get your supplies, see if they have small quantities of peel ply. It can make it much easier and prettier.
 

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B.K.O.R.C. - Director
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Rolled my Jeep at jeep fest and broke the fiberglass top

I roll my cj7 on its side at jeep fest in Copemish and cracked the fiberglass top



The passenger side was slid out and inch or so and I was able pull it back in flush with the side.

this leaves my with two question
1) the windsheld was pushed over about and inch





should I unbolt the windshield from the top before repairing the top?
I am replacing the windshield and frame.

and

2) there is two cracks in the top



should I deal with them as one repair or two?
I was concidering grinding it out and doing it as one
but not sure how much to grind out ?
How much of a bevel do I need?
 

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Yes ... unbolt the windshield from the top. It could be holding it "out of shape"

You can treat them as one repair. Grind the inside, add glass, structure, cure, "bevel" the outside, fill, sand and finish. (In so many words)
 

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Discussion Starter #16
Thanks for all the input. I will get the supplies this week or next. I may have some more questions once I actually start.
 
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