What can I do to bond fiberglass to metal, and keep it from

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PostPosted: Tue Jul 17, 2012 4:27 pm
cracking down the road?

I have already used the appropriate bonding agent {its been years, and now I'm getting the car back, and I can't remember what bonding agent was used}.

I also put stainless steel self tapping screws into the flange. The body filler to smooth it out.

But now I was thinking about going back and putting a few layers of fiberglass matte on it just to make sure.

Here is the car in question, and its the rear fenders, and door panels that worry me the most.

http://huntsville.ebayclassifieds.com/c ... d=18438034



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PostPosted: Tue Jul 17, 2012 5:23 pm
What I did was use Fusor cross bonding agent, and then polyflex to smooth the edge (wasn't a very big lip from the fiberglass scoop to the metal hood.. 1/16 maybe?), then my regular 2K on top. Hope it holds!

ALthough I do notice now that I (only I.. Others can't see it for some reason) can see a line running around the hood. I can't for the life of me figure out what it would be. Definitely couldn't see it through the 2K, and definitely couldn't feel it.



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PostPosted: Tue Jul 17, 2012 5:39 pm
Metal and Fiberglass expand and contract at different rates. There will always be a line.



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PostPosted: Tue Jul 17, 2012 6:48 pm
If there is always going to be a line, it looks like I could run a thin pin stripe where the crack is {there is already a hairline crack}, and just paint the pinstripe when I paint the car.

Might not be as noticeable as a crack.



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PostPosted: Wed Jul 18, 2012 8:29 am
It's not that simple. Filler and metal contract and expand at different rates. Lead and sheet metal expand and contract at different rates. Either way, if it doesn't crack, I'm happy!

M-train, yours already cracked?? That's rough. (Watch me go home this weekend and see mine has too. hah)



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PostPosted: Wed Jul 18, 2012 2:31 pm
JohnnyK wrote:It's not that simple. Filler and metal contract and expand at different rates. Lead and sheet metal expand and contract at different rates. Either way, if it doesn't crack, I'm happy!

M-train, yours already cracked?? That's rough. (Watch me go home this weekend and see mine has too. hah)


Yep, already, not even driven yet........lol.

I was thinking, what about laying some carbon fiber matte over the seam. Would that be strong enough?

Anther thing I can think of is to brace the under side of the panel as well as a roll cage to stiffen the body, as hatchbacks are notorious for being very flexible.



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PostPosted: Wed Jul 18, 2012 2:48 pm
You're asking the wrong guy. All I know is I used fusor cross bonding (meant for metal to fiberglass), and then a flexible filler.. Now, I didn't add any flex agent to the paint, so who knows!

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PostPosted: Wed Jul 18, 2012 6:57 pm
Our resident fiberglass guru is DarrellK. He has built a few fiberglass kit cars and bonded 'glass to metal many times. I do a lot of fiberglass work on Baja bugs and the like. Usually pop rivets, sheet metal screws or other physical anchors work well in addition to the normal procedures.

I have always used regular polyester based resin, but would imagine an epoxy based resin would work better for bonding to metal. You can get epoxy based resins at boating supply houses such as West Marine.

One thing to keep in mind; the metal needs to be pretty rough or coarsely ground to make enough "key" or surface area for the fiberglass resin to bond to. If you try to apply it over regular 80 grit scratches, chances are it will pop right back off within a few months. I use a 36-60 grit scratch or heavier when bonding glass to metal or wood. :)



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PostPosted: Thu Jul 19, 2012 2:09 am
Try the 3m structural adhesives, alot of them set hard the fusor does not seem to cure out well, and they recommend bare metal prep, I dunno I would be tempted to try using and epoxy primer with zinc chromate base before any fiberglass work on top of it, then scratch it up and go with fiberglass and not use any rivets or sheet metal screws,they will show through, fiberglass needs a good transition from metal to glass and be supportted, you cannot expect to have an abrupt cutoff and not expect to see the line, because it is showing the fibreglass is unsupported, weak and has air trapped.

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