Fiberglass repair

Wingboy

Wingboy

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Never done fiberglass repair before.But i'm going to get lots of practice now.The bodywork is Sharkskinz which is a good thing.I have a bunch of cracks and splits to repair.Do i need to grind out the stuff in the split to allow the peices to get back to their normal shape before laying in the patch itself?And what works best for grinding it?I know the paint has to removed inside and out.
Here's a pic of the bellypan from the inside,and then from the outside.
picture100zl.jpg

picture101f.jpg
 
It's nice to get the piece back as close as possible to the original shape. If you can get everything to line up you may not need to grind out the crack. Clean out all the broken and loose bits.
I use a large (ish) stone on a hobby grinder (dremmel)
You could repair from the back side only. Both sides will make for a stronger repair. Start on the backside. Tape the front side with duct tape (or whatever it takes) to give you the right shape.
Clean up (grind) a generous area around the crack. Wet it down with resin. Work the resin into the crack. Layer on a couple of layers of fibreglass cloth (I like to use high density). Work resin into the cloth, one layer at a time. It may seem backward, but use only as much resin as you need to wet the cloth. (adding resin doesn't do a lot to increase strength, it's all in the 'glass)
Once the backside has hardened take the tape off and see if the front side needs repair as well.
In your case you might need to do some work to rebuild that mount hole. Clean up (grind) any loose fibres.
You're done. (No need to paint it; "chicks dig scars.")
 
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VFR.CBR said:
It's nice to get the piece back as close as possible to the original shape. If you can get everything to line up you may not need to grind out the crack. Clean out all the broken and loose bits.
I use a large (ish) stone on a hobby grinder (dremmel)
You could repair from the back side only. Both sides will make for a stronger repair. Start on the backside. Tape the front side with duct tape (or whatever it takes) to give you the right shape.
Clean up (grind) a generous area around the crack. Wet it down with resin. Work the resin into the crack. Layer on a couple of layers of fibreglass cloth (I like to use high density). Work resin into the cloth, one layer at a time. It may seem backward, but use only as much resin as you need to wet the cloth. (adding resin doesn't do a lot to increase strength, it's all in the 'glass)
Once the backside has hardened take the tape off and see if the front side needs repair as well.
In your case you might need to do some work to rebuild that mount hole. Clean up (grind) any loose fibres.
You're done. (No need to paint it; "chicks dig scars.")
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Hey, I know this is an old thread, but thanks for this posting. I've never done anything with resin and fibreglass before, so reading other guides almost made me send off my bodywork for repair. Your short write up is so clear and I'm happy I saw it. I don't care about looks, just picked up some bondo stuff from Canadian tire (repair kit, also the fiberglass reinforced filler), and will attempt to do this myself. Helps it's just a track day body. Scars are OK :)
 
kneedragger88 said:
In ended up fixing and painting that one.
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Aah, this looks awesome, Ken!

I'll be initiating the repair later today, but have a couple of quesitons if somebody knows. See pic below: since it all lines up fine, I was thinking to hold it with duct tape, then grind it from the back side and lay two pieces of fiberglass. Should I also grind from the front and do the same there? Or just grind from the front and put just filler? ...OR, cut it all out, connect with fiberglass from the back, the front, then filler?

1-2013-08-08144102_zpse10dd108.jpg
 
Corsara said:
Aah, this looks awesome, Ken!

I'll be initiating the repair later today, but have a couple of quesitons if somebody knows. See pic below: since it all lines up fine, I was thinking to hold it with duct tape, then grind it from the back side and lay two pieces of fiberglass. Should I also grind from the front and do the same there? Or just grind from the front and put just filler? ...OR, cut it all out, connect with fiberglass from the back, the front, then filler?

1-2013-08-08144102_zpse10dd108.jpg
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Do all the heavy repairs from the back side. It doesn't look like you'll need to cut out anything, just grind it down on the back side. Tape the front side to hold the shape. It looks like you might have a bit of trouble holding the shape while the back side repair cures. In this situation I've shaped a piece of wood to match the contour and hold everything with a couple (or more) spring clamps while the repair cures. If you're using "waxed" resin and need to add layers after the initial repair has cured, remember to remove the wax film, a light grinding will usually suffice.
If all goes well on the back side there won't be much to do on the front side, clean it up with a light grinding and apply a thin layer of filler. If it needs any more than a thin skim of filler, then do a fibre glass repair to bring it up to level, then filler. Generally you want to avoid having to do a fibre glass repair on the front as it takes more work to hide the texture.
 
I'm so glad I deal with a body shop that knows what they're doing... Did all my bodywork and paint on the CHEAP!

Before:

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After:

9511058928_30dc5f4a97_z.jpg


VFR.CBR's advice is pretty much spot on, although I didn't see the guy work on it from A-Z but I did stop in occasionally.
Masking tape on the outside and all the fibreglass and resin/hardener mix was from the inside. Filler, sand, etc.
 
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Are there any concerns with using polyester resins on epoxy body work or vice versa?
 
Don't know if my resin is wax-based, it doesn't say on the bottle. I just did a test-run on my lower body (crash made a 1"x1" hole, obviously not displayed in the pic I posted earlier). so we'll see how it works out. I just grind it from the inside, cleaned it up with acetol, then rasin solution => cloth => brush to make sure it's wet => another cloth => some more rasin. Looks good for now, will wait it out and see. In terms of how it looks (if I have to do it from the outside, I really don't care much, it's a track day bodywork, and by the looks of it it will see the ground more often than I wish by the end of the season and next, so I'm all good :) I'll post a couple of pics later, but I'm afraid it's not gonna be not even nearly as good as Mina's repair, which looks awesome by the way.
 
Don't sweat it, I have no skill what so ever, I just paid someone to do it. lol
 
As an FYI, easy way to know if your resin is waxed or not, touch it when it's cured. If it feels completely dry and smooth, it's waxed. If it has a small amount of tackiness feel to it, it's unwaxed. When I used to do fiberglass work, I used unwaxed to build up layers, as they will stick better to one another, followed by a waxed final layer to give a nice smooth finish. When you sand unwaxed, you'll see that the powder will 'stick' to the work, and will be hard to just wipe off. When you sand waxed resin, the powder will not stick to the work, and a simple blow gun will get rid of it.
 
I just remembered I never posted the other day about the fiberglass repairs I did.

Let's just say my goal was to make it strong, and I achieved it. As for pretty---I believe I could have made it much better if I used a regular filler on the outside. Instead I used Bondo Hair, which I found impossible to shape for my purposes, although with a couple of more layers and massive grinding that could have turned out well too. I used fiberglass cloth for the outside on the tail though, just to see if it will be better...

Anyway, I enjoyed the process, here are some pics:

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Your along the right path. I use duct tape all the time. Also another good trick is using empty beer cases (cans) the cardboard is just the right stiffness for forming complex shapes. I have used it to replace missing pieces generally you can overlay the other side to get the exact shape needed the reverse it for opposite side Duct tape it on and then lay in matting from other side. once cardboard comes off (most of it anyway) shape with random sander and 150-180 lay in a bit of bodyfill to clean it up . Take it down with 320-400 after rasp. Prime, prep with 400 then 800 and paint.
 
Mina said:
Don't sweat it, I have no skill what so ever, I just paid someone to do it. lol
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I have tiny hairline cracks in my front nose fairing. How much approximately would it be to stop crack and paint from your experience?
 
Mr.Azim said:
I've fixed worse damage with a fibreglass repair kit from crappy tire.

Or you can contact TJ @ Reflections Auto (carboncat on gtam) to get it fixed.
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I know TJ, the job he does is professional, the things I've seen him get done are in better than showroom condition after leaving his shop. In my case that would've been an overkill, I'm likely to crash again soon anyway.

kneedragger88 said:
Your along the right path. I use duct tape all the time. Also another good trick is using empty beer cases (cans) the cardboard is just the right stiffness for forming complex shapes. I have used it to replace missing pieces generally you can overlay the other side to get the exact shape needed the reverse it for opposite side Duct tape it on and then lay in matting from other side. once cardboard comes off (most of it anyway) shape with random sander and 150-180 lay in a bit of bodyfill to clean it up . Take it down with 320-400 after rasp. Prime, prep with 400 then 800 and paint.
Click to expand...

I really don't know why I used the detail sander and not the random orbital I have, would have turned out better. But yeah, good to know about using cardboard from beer cases, that could come handy in the future. So, it goes something like this: crash => drink a lot of beer while fixing :)
 
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