Hot Rods Fiberglass repair advice needed

I am needing some advice on fiberglass repair for my ’32 Ford coupe. One fender has a foot long tear in it. I would like to get it back together without destroying what’s left of the yellow paint. The car has plenty of “survivor” chips, scratches, and flaking paint so this scar will fit right in. If I ever repainted the car I would replace the fender altogether.

I am estimating the fender was made in the late 60’s-early 70’s time frame. My plan would be to use an epoxy of some sort to bond the tear back together. Then grind some of the underside away and lay some mat over the seam. Does this seem reasonable? What type/brand of epoxy should I use? I have done very little glass repair before, and don’t really plan on doing much ongoing so I don’t want to invest in an epoxy gun. What recommendations do you have? Thanks for all help.

 

All the two part adhesives need a gun but you might be able to use fiberglass filler as an adhesive. Prep the part's with a grinder or 80 grit paper until it's dull. Use mixed filler as the adhesive not mixing it to hot then clamp it together with vice grips allowing the excess to come out. Build up the back side with cloth and resin.

 

I'd pull it together from the top side as good as possible. tape it up. First a layer of masking type tape for ease of removal, then some duct tape for strength.
Scuff the bottom side with 80 or so. then brush on resin, add a layer of glass mat (chopped would blend best) followed by 1 or 2 more layers. Then call it good.

Any glass resin and hardener will be fine for what youre doing. A quart kit will be more than a plenty. itll take maybe 8 ounces

 

Evercoat does a whole range of 2 part adhesives that work in a caulking gun.
http://www.evercoat.com/adhesives/us/
The rest of your plans sounds like it would work fine. You can use reinforced tape (like drywall mesh tape) with the epoxy adhesive to repair the back side rather than mat.

 

Your plan is basically doable. The way it's torn gives you a natural overlap. Bridging it with a wide strip of mat on the backside is another step in the right direction.
But I don't hold much hope of eliminating any paint issues. At the very least the epoxy will ooze out and even if you squeegee the excess off, it's going to appear like glue on paint and draw the eye just as much as the crack, if not more. I don't see how you can avoid filling, lots of sanding, and primer...... and possibly color matching as an additional final step.
Doing something is a good plan, though. You don't want it to snag or lose chunks in the wind.

 

I am not a pro at all, but I mess with fiberglass on an off-road truck. I have done repairs to the back side only and then used some kitty hair or bondo on the front. It worked... For a little while, but the crack came back. Since this is a street vehicle and not off-roading I would expect it to last longer then mine (less bumps, jumps and hitting things). In the end I say do it. If it fails it is just glass and you can fix it the right way then. For now getting it to line up and glassing the back is better then what you currently have right? Glass is cheap and easy. If you mess up grind it out and do it again.

 

I would set up some clamping fixtures first. Have them ready to clamp it. Masking tape to protect the paint, mask just about the whole fender. Have the back side ground or sanded ready to apply matting. Mix up some fiberglass resin, get it in the crack however you desire. Clamp it and let it harden. If you can, apply some resin and mat to the back side before you take off clamps. After that gets hard, take off the clamps and apply more matting to the back. If all went well you can take of the tape from the fender and clean up the resin a bit with some careful grinding. There should be just a line where the crack was.

 

He's just looking for a handy bonding adhesive to attach the two sides of the crack back together, something that won't make too much of a mess and ooze all over the remaining paint. Then he can flip the fender over and do the resin and matt on the backside for additional strength. He isn't looking for a show car fix as he doesn't want to do any repaint on this fender. The scrape will match other "as found" scratches on the car.

 

Use UPOL SMC for filler. Normal body filler will crack on fibreglass.

Sent from my SM-A105G using Tapatalk

 

This is kinda what I was thinking to use to glue it back together. It says it is for fiberglass. Then grind some of the underside down and apply mat and resin. Think it will work ok?

 

I would line up the pieces and use painters tape on the paint to "seal up" the crack then use an epoxy like that from the back. THEN do the backside reinforcement with mat and resin. Probably just leave a small line on the front

 

Gorilla Glue

 

West System epoxy

 

What ever you do, You need a bonding strip at least 2" wide the length of the crack, gives an inch each side, doesn't have to be more than 1/8 thick, I have used broke CJ hard top's, you name it in my shop....

 

Unless you are looking to do a "farmer repair" you are going to end up damaging the paint around the crack, so you might as well do it right.

Establish the shape of the fender back where it belongs using 2" x 3" pieces of formed sheet metal to support the fender together and in the correct shape. These are attached to the backside of the fender using self-tappers going in from the top side. Use mold release on these metal strips so you can get 'em off later.

Then "V" the top of the crack with a grinder going as deep as you can without going completely through. You can mask off the area around the crack so as not to get your filler material any more on the fender than you have to during the course of doing the repair.

Then use fiberglass resin and matting on the topside of the fender, filling the "V" with resin/matting as required with as much overlap onto the surrounding area as you can. This will get sanded smooth later.

When the resin/matting on the topside has cured, flip the fender over and remove the self-tappers and the metal strips from the bottom. Using a fiberglass "bonding strip" on the bottom side is a good idea, but you can just use a thick layer of resin/matting on the bottom side of the crack - after V-ing it out like you did on the top - to accomplish the same thing.

If you put masking tape over the self-tapper holes on the top side you can fill them with resin/matting from the bottom side - or you can use DuraGlass - and they will be good to go when you refinish the fender later on.

This is essentially how damaged Corvettes are repaired and customized. The metal strips are necessary to hold all the pieces together and in proper alignment. You can't do this with tape and you'll save yourself a lot of time and aggravation later on if you get the pieces in perfect alignment the first time.

Hope this helps. Good luck!

 

If he's going to "do it right", he'll replace the fiberglass fender with a steel one and repaint the whole thing to match. As stated or implied, the goal is to structurally repair the fender so that it can be used on a driven car without the crack propagating further without having to work the external surface. Having perfect paint around the crack isn't the goal, so long as it isn't covered in extruded adhesive goo. Heck, the crack can remain visible from the top side.

 

This. I mean, why wouldn't you use fiberglass resin to glue fiberglass back together?

 

I have built complete fiberglass parts by piecing multiple pieces together not terribly different than what you are talking about and have never had something come back apart or even crack. I would use something like what you mention here and clamp the crack together while it sets up trying to control how much oozes out on the top side so it isn't any more evident than it has to be. Then, I would grind the back side with something like 80 grit, put resin on it, lay about 10 layers of cloth around 3" wide over the crack while using resin on every layer and call it good for a LONG time. I also wouldn't be afraid to grind some on the top side later and just lay a few layers of glass over it too for the final fix once you decide you don't mind repainting the fender.

 

The right repair is to replace the fender.

 

Replacing a fender is not repairing a fender. Replacing a fender is repairing a car. Both are acceptable. I'm for fixing it as the op asked about. If he decides to replace the fender now or in the future is a choice, his choice.
I have done and helped others do this type of thing many times. We have found that if you screw a mending plate to the top side, do the glass work on the bottom and then remove the plate and finish the part that shows to whatever degree the owner desires is perfectly permissable.

 

This will read more labor intense than it really is but stay with me here...

1st, and anyone who says different can feel free to shit on me about it, but epoxy based gigs don't play well with polyesters. The older the 'glass is the more likely it'll be to fuck up. I'm not gonna play mad scientist here so take it or leave it, it'll fail either structurally or cosmetically, usually both.

Ok that's gone. You need some Duraglass (or the equivalent), some regular quality mud/bondo/polyester filler, polyester 'glass resin and mat. Mat is easier to blend in. Grind it out clean 1st top and bottom and get it pulled back where you need it. Mix up some Duraglass and "thin it out" a bit with some resin. You don't need liquid hardener for it just because you added resin. Play with it until works smooth, add your hardener, fill the top lightly as you can but still maintain enough strength to hold it together. Clean out the ooze from the back so it's as out of your way as possible, but again, strength. Let it cure, will be about 10-15 min but overnight will make it harder than the hinges of hell. Rough up the back and 'glass it. I'd recommend about 3 layers minimum and if you can keep it clean enough just let it cure and call it whipped. On top, take down the Duraglass just below your finish level and 'glass a few layers over that too, just enough to execute some decent finishing but still "below grade" so to speak. The textbook move after finishing would be gel coat but we're repairing here, not building. For your 1st build to the finish surface mix a 50/50 blend of regular mud and Duraglass. Again play with it to make it easy to apply and manage for simple finshing. Take it down, a final nice wipe of straight mud, finish, prime and paint. I need to add here, every process will require sanding and grinding after cure for a good mechanical bond throughout.

There's a theme here, everything is polyester based. It's also going over a polyester substrate so all the components will play nice together for years to come. Again anyone that feels like flickin my nut sack over the avoiding epoxy thing go ahead, but it will fail. If these were SMC you might get away with it but they're not. Good luck, and maybe show us how it comes out.

 

Wow, there are a bunch of different opinions on how to do this. I guess I should have expected that! I will have to digest them all and formulate a plan.

 

Pretty sure some here are trying to make this harder than it is and it seems you are looking for a temporary fix anyway. Your original idea will hold together just fine as long as you actually glass in the backside with a few layers until you decide to do something else. The worst that can happen is that you decide to replace it later anyway like you mentioned.

Glass fenders aren't that expensive so spending too much time and effort on this is probably not what you are looking for. I'm sure you will get it worked out just fine and be happy with it for a long time. If you weren't so far away, I would offer to just fix it for you in an hour of two's worth of work.

 

I hope everyone read the part about epoxy and polyester resins by the Highlander. When you make a mold for a polyester based part you use epoxy resin so they won't bind together. So, how would you expect it to stay together when repairing a fender?

 

Reading through your thread, looking to see if anybody mentioned epoxy versus polyester.

Finally, someone mentioned... West Systems epoxy.
Then it was said that epoxy resin won't stick well to the polyester based fender. And that was reinforced with the statement that polyester based fiberglass parts are laid up in an epoxy based mold... so that the part won't stick to the mold.

West Systems is just one of many good companies who carry fiberglass materials.

No matter what a mold is made from, a release agent is always used so that the laid up part will release from the mold.

Polyester based fiberglass resin is usually used for laminating... laying up fiberglass parts such as your fender.
Epoxy based fiberglass resin is considered a bonding type resin. Used epoxy resin has about four times the holding strength of polyester and is often used where excellent structural integrity is necessary. 500 pounds per square inch for polyester vs 2000 pounds per square inch for epoxy.

This is the thing
Polyester based fiberglass resin does not stick well to epoxy based fiberglass.
But epoxy based fiberglass will stick to almost anything... including cured polyester fiberglass parts... your fender.
When a boat built with polyester fiberglass needs part of its inner structure replaced, they cut out the rotted portion and build and bond the replacement to the polyester based portion with epoxy based fiberglass.

Of course, anytime you are trying to glue something to something else, it's good and sometimes absolutely necessary to really rough up the area to get some tooth for the new stuff to grab onto.

And as with most other things, do you your research, follow directions, and a test application will always teach us something... before we dive in head first.

The polyester will work.
The epoxy will work better.
Epoxy is more expensive.
Epoxy resin will not work with some woven fiberglass cloths.
Works fine with chopped strand.

That's all I can think of right now.
Good luck.

 

@theHIGHLANDER...
Might disagree...
but never shitting on you.

 

Rickybop,
Thanx for the clarification. I have to admit that my fiberglass experience is getting pretty old, around 1978. The technology of the day was to use epoxy resin for molds and polyester for parts. Release agent was always used too.
I was trying to simplify, and between that and old guy thinking, I was making some poor generalizations.
I'd still fix the OP's fender as I described

 

Epoxy based products aren't meant to "soak in" like old school polyesters do. When you grind out old stuff like vintage boats and fenders, old 'vettes, etc, those surfaces are pourous enough to suck in the liquid resin and create a nearly chemical bond as well as a stronger mechanical one from grinding. The newer stuff like panel bond won't play either. They grip but they also suck up solvents and then shrink later compromising the mechanical bond. As mentioned above it's a simple gig, a few hrs and some itch, done. Long sleeves and fan behind you goes a long way to managing the misery.

Modern epoxy formulations have their places and do last longer, have superior strength when applied as engineered. From experience I've never had an epoxy-ish product last on an old 'glass part repair. There's only 1 thing worse than doing 'glass work, and that's doing it twice. The obvious question; if the old polyester parts and repairs are inferior then why is the shit still around? We're here discussing a fender built 50 or 60 years ago. Fuckin junk...

quick edit: Just took another look at the damage. Once roughed up top and bottom you can mix up the Duraglass as recommended, thinned with resin, use THAT vs epoxy, tape it together for position and let it cure about an hour. Still take down excess ooze. It'll stick sooner but leave it until it's back to room temp (gets hot when it hardens). Flip it, grind the stuff that came through and glass the backside, maybe 4-5 layers but keep it at least looking like rest of that rough ass surface. Let it cure, rattle can some black, bottom done. Finish the top with Duraglass and bondo. No need for glass work on top. Resin is cheap, a qt of Duraglass is cheap, bondo is cheap. I'm out, but I'd still like to see how ya did.

 

Most responders to this thread aren't listening to the original post. He doesn't want to do ANY body or restoration work to the topside. Just glue the crack back together, maybe strengthen on the UNDER side, and leave the scar on the top. ZERO paint or finishing on top, and hopefully not a lot of goo oozes through the crack.