Molding fiberglass spoiler to metal oem trunk

Anything goes in the world of fiberglass and plastic



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PostPosted: Fri Mar 28, 2014 6:26 am
Years ago, I bought a fiberglass ducktail spoiler. I sanded down the paint on the trunk, secured it down with very strong adhesive, and then used Bondo to try and smooth over the seam.

Like I said, that was years ago. I didn't know Bondo was so rigid and would crack. The job I did was very well executed; it's just that Bondo wasn't fit for the job and I have a crack where the Bondo meets the fiberglass. Otherwise you couldn't tell it was a two piece thing.

So, present day, I'm prepping the car for my first 'real' paint job (which I plan on doing myself). I would like to address this issue. I am at a loss for a plan of attack. What would you use? What method would you use to prevent flexing and most expansion? I want to stop all cracking altogether.


If there is no viable option, my back up plan is to just buy an appropriate section of 3M vinyl wrap which best matches the paint and just wrap the stupid trunk.

Oh, by the way, this is going on a Miata. For reference, here is the same exact spoiler. Ignore the rivets, this is not my picture.

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PostPosted: Fri Mar 28, 2014 8:39 am
First, welcome to the forum. Now for the bad news.... Ever wonder why you don't see factory plastics actually bonded to metal surfaces??? It doesn't work. You are fighting physical properties way beyond your control. The expansion rate difference between plastics and metal is just too great with temp.s swings from exposure.
Vynil wrap isn't a bad idea. You will still need to make a minor separation as it will pull itself apart as well over time (it's plastic too right?). I would put down the knifeless pull tape around the base of the spoiler, then wrap the whole thing tightly, then slowly pull my tape making a nice close (trust me, I've done this, you can barely see the seam) separation. You can also obviously pre wrap the spoiler separately and just bolt down to the trunk.
What looks best to me is to use something like a pre-colored plastic gasket/piping like they use on old VW fenders. I think that gives a more "factory" look to the whole thing.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Fri Mar 28, 2014 3:39 pm
As said, trying to mould them together as one isn't going to work.

If you really want the seamless look I guess you could temporarily smooth the area out as you did before, make a mould of the whole lid including the newly added spoiler, then use that mould to construct a new skin for the lid out of fibreglass which you could join to the old lid frame after cutting the metal skin off.

That's a whole lot of work though...



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PostPosted: Sun Mar 30, 2014 8:36 am
Thanks guys. I was pretty sure that this was going to be the result, but I wanted to check with the experts of course!

For reference, here's where that picture came off of. I'd wager that they never post results because they all cracked perhaps.
http://www.mx5nutz.com/forum/index.php?showtopic=138666

Looks like I'll be wrapping the vinyl.

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PostPosted: Sun Mar 30, 2014 9:14 am
Thanks for the link for that.... Yeah, riveting like that was a bad idea on something that gets slammed shut. He would have been better just doing a straight epoxy bond or using something like a Fusor bonding product. And, yes you never get to see long term pic.s of a lot of this stuff.

I think your wrap idea is a good one. I am slowly becoming a fan of wrapping for various problem areas on cars. I made a mini nose shield for my car since it sees fairly high cruising speeds during our summers here... bugs, bugs, bugs... I'd spend a 1/2 hour at car shows cleaning them off. Now just a quick spritz of spray detailer and they wipe right off the faux carbon fiber.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Sun Mar 30, 2014 12:50 pm
unclefather wrote:For reference, here's where that picture came off of. I'd wager that they never post results because they all cracked perhaps.
http://www.mx5nutz.com/forum/index.php?showtopic=138666


I wouldn't be happy with that job at all, but then it's not my car so if the owner is then fair enough :)

But it shows just how small this internet world of ours is. There's a guy posting on that thread (Painter Dave). He and I used to work together for a while. He left to set up his own place and is doing rather well, but I'm still stuck here! :lol:

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