Refinishing old fiberglass hard top

Anything goes in the world of fiberglass and plastic



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PostPosted: Mon May 08, 2017 12:52 pm
Hi -

I'm new here & while I've done plenty of welding & fabrication on cars, I'm pretty new to auto body work. Other than some small repairs, I've not done much before.

I have a little British MGB (that I put a Ford 302 into) & recently got an old (circa 1970's) fiberglass hard top for it. Plan is to paint it gloss black (which I know means prep needs to be best it can be).

The top had a thick gel-coat that simulated vinyl texture which I sanded off. That left thousands of little air bubbles/pin holes. On the recommendation of a friend, I put down a coat of polyester primer to make the holes easier to see & then filled them with polyester finishing putty (FINISH PRO, AL-GLAZE PRO GLAZING PUTTY, Part # FPR-216).

There were also a few places where I had to fix the top with fiberglass & a thin layer (<3/16") of polyester filler.

I've since sanded the top smooth so there's a patchwork of bare fiberglass, glazing putty, and filler.

I'm now ready to start block sanding, but do I need to use a sealer before I start spraying high build primer? If so, what's recommended? And/or what other recommendations do you have so I don't waste time/energy/$$?

I work slow, but will try to use this tread as a progress page & I'm sure I'll have more questions as I progress through this process. I appreciate your help along the way!

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PostPosted: Mon May 08, 2017 6:08 pm
With all that going on I'd seal it all down with full strength epoxy primer. If you've got a local jobber see if they've got maybe some closeout quarts in colored epoxy primer. I mean, you're going black so it's going to cover.... If buying on the net look at the storefront here for Tamco. You could also consider maybe **********.
302 in an mgb huh, love engine conversions in a small car. Harks back to the days of Sunbeam Tigers, original 289 Cobra, etc. I run about a 320 hp supercharged rotary in my 1800 pound kit car. Just cannot get that smile off your face...... :lol:
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PostPosted: Mon May 08, 2017 7:08 pm
Wow, thanks for the quick reply Darrel!

And thanks for your comment on my car; you can see more of what I did here... http://www.britishv8.org/MG/RobFicalora.htm. What's your kit based on? Sort of looks like a Fiberfab. I don't know much about them but a regular on one of the British conversion sites built - or I should say, rebuilt one. Looked like a great project & makes for a fun car.

So, epoxy primer. Will check the local jobber tomorrow to see what they have. Is there a window of time after the e-primer before starting high build - or does it depend on the brand of e-primer?

Thanks agian for the quick info!
Last edited by 302MGB on Wed May 10, 2017 2:23 pm, edited 1 time in total.

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PostPosted: Mon May 08, 2017 9:45 pm
Yeah, mine is a Bremen manufactured Sebring II model. Rear engine configuration going to a pretty much modified to the max VW transaxle. In fact I've got it over on ebay at the moment.... http://www.ebay.com/itm/1983-Replica-Ki ... t4&vxp=mtr
Epoxy primers do vary somewhat with time windows, and yes, the product sheet for whatever you choose will get into the specifics.
Wow, just looked at your car....I now feel like a slacker. Nicccceee job.... especially like the tasteful chin spoiler. What a bunch of work and a very tidy install. You'll like having a removable hardtop. My wife has a 2004 Ford Thunderbird Pacific Coast Roadster that has a removable top as well. It's handy for winter and long trips for us.
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PostPosted: Wed May 10, 2017 12:40 pm
Very cool car Darrel! I remembrer drooling over those in magazines growing up. I was actually researching to find a kit car I could build when I ran across BritishV8.org and decided to go that route.

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PostPosted: Wed May 10, 2017 3:59 pm
i would feather fill with a 2.5

sand with 150 and fix what needs fixed then high build primer.. not epoxy
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PostPosted: Wed May 10, 2017 4:45 pm
Hey, Dave, just curious, I've been locking down fiberglass now for 27 years with epoxy and haven't had a problem with it, so why no epoxy? I've seen crap bleed right up through Slick Sand and Featherfill on old fiberglass work and yes, it was still staining up through a 2k build primer. I mean, I guess I could see it on very new "virgin" parts but that's not what we are dealing with most of the time.....
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PostPosted: Thu May 11, 2017 8:38 am
hey darrel, im just not a fan of sanding epoxy. just my opinion. theres more than one way to skin a cat. what is bleeding through ? i dont work on kit cars or old stuff at all so im sure you run into more problems than myself. what bleeds through 2K that dont bleed through epoxy ?
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PostPosted: Thu May 11, 2017 2:52 pm
Yeah, okay I get it with the sanding epoxy thing. And yes, almost everything I work with is somewhat "seasoned" fiberglass. The problem with not using epoxy is that gel coats wear down with age (worse if it is a sandable gel coat that never got finished), stuff ( and this list includes but obviously isn't limited to....) like cat urine, pigeon poop, soluble gypsum dust from a leaking drywall ceiling, and on and on.... get stuck in the gel coat or worse just under the gel coat and magically release when you start working the surface. I've always found that PPG DPLF epoxy can stop any of that from coming up but high build poly surfacers and polyurethane 2k couldn't stop that crap from leaving a contaminated surface with problems. One time when I skipped sealing with epoxy (trying to meet a car show deadline) my Slick Sand "bloomed" kind of yellow and wouldn't even harden up (assumed that something was neutralizing the hardener) in a horizontal surface. I should have known, the guy told me the roof of the car was exposed to everything in his old barn. It was still soft after 3 days and you could just scrape it off like soft mud.....
So, yep, if you are working newer fiberglass I could see getting away without using it.
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PostPosted: Thu May 11, 2017 6:38 pm
Ok - so sounds like for my application with the various products that have been used already, a seal coat of epoxy makes sense. I was assuming that is intended to be a seal coat that's not sanded back. Instead, poly high build goes over it directly & it's the high build that gets blocked. Did I get that right?
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