Fibreglass Bumper Repair

[AE92-5ONIC]

I have read almost all the fibreglassing threads on this forum and videos on youtube but they havent really answered my question.

How do I repair a cracked bumper like this?



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Am I able to grind back a larger area of the surface then fibreglass over that surface using resin + fibreglass cloth and lay a rough gel coat over the top of that then sand back? Or is this the wrong way about dealing with this?

Cheers.

[soopachargen]

you shouldnt need to gel coat them, grind the face back a bit and glass it up and make sure you reinforce it from the back too

[AE92-5ONIC]

no gel coat? but I am repainting it?

[soopachargen]

gel coat just goes in molds, you can prime and paint fibreglass

[AE92-5ONIC]

OK, cheers, looks like I have a project for next weekend

[Stott69]

might want a skim coat of bog over top as I think fiberglass is pores

[AE92-5ONIC]

Yeah, was thinking that too.

[frost]

another trick a friend showed me was if you dont want to grind back some fibreglass, you can use a syringe to inject resin into the crack to bond them back together, just slightly pry the two parts apart and drench the crack with the syringe, then wipe off excess resin,
you can buy syringes from pharmacy for like $1.30 each,
this saves a lot of back fill work later. then just one layer of glass on the back for added support.

[Quint]

Use chop strand behind to give strength, clean up the front so the crack doesn't have loose paint and crap everywhere and just fill it with resin, let it dry and sand it back flush.

[Flannelman]

to repair it properly it takes time. This is how i would do it.

1. Cut out broken sections of fiberglass.
2. Sand inside of bumper so the repaired section has something to bite to.
3. Put tape over the holes on the painted side of the bumper. This will act as the mold. Try to shape as best as possible. The extra five to ten minutes to get this right will shave hours off trying to sand and fill
4. With the tape in place, position bumper somewhere it wont be disturbed for a day. You will be working on the inside so keep this in mind too.
5. Use gelcoat. Mix up a batch and spread over the tape and 100-150mm on to the existing fiberglass bumper. This will act as a bonding agent, stops cracking and gives the paint something to stick to. Make sure there is at least 4mm depth in coverage. Any less will result in tripe. (It will look like the inside of a sheep stomache) Due to the nature of the bumper, a styrene buildup will occur. This just means the cure time will be extended.
6. When gel coat has cured (it leaves a fingerprint in the surface) Its ready for the fiberglass. The strongest glassing is with the least amount of resin. Be sure to remove all air from under the matting. When finished dont touch for 24 hours
7. Next day peel off tape and begin shaping your repaired section.

[Truenotch]

I did a similar type of repair job on my bumper using fibreglass and bog - it worked well for barely any effort.

I had to chop this bulge out and redo the whole area.


- Started by cutting away the bulge and sanding the surface so it was rough to give the glass a chance to stick.
- Cleaned off all the dust from sanding
- Cut the cloth to suit.
- Glassed 4-5 layers into it for strength, with a good amount of overlap on the underside and generous amounts of resin.
- let it dry, gave it a light sand and used normal bog to finish it off.

Result:

[Jingle Balls]

did you let your dad drive it again?

[AE92-5ONIC]

did you let your dad drive it again?

Huh?