Technical Painting a fiberglass car?

I'm about to start working on a '63 Studebaker Avanti- pretty much the only other HAMB-legit fibergl*** car besides the Corvette.

While I'm a reasonably competent mechanic, I'm very much not a paint-and-body guy, nor do I have the oodles of spare cash sitting around in easy-to-carry packages to just have the job off to a professional shop.

Like it or not, I'm gonna have to do it myself.

First, the car has 45 year old Imron. It's bubbling in a few spots, but only a few. Seems in good shape elsewhere. Should I go through the time and expense to have it stripped, or risk spraying over what's already there?

Second, if I do strip it, what are my options? Soda or dry-ice blasting? Mechanical means like grinding or s****ing? I'm given to understand that chemical strippers are right out.

Third, and there seems to be some debate about this: Bodywork then gelcoat, or gelcoat and bodywork over that? (There's also the question of bodywork over epoxy primer.)

And fourth, does anyone have a link to, like, a definitive fibergl*** car how-to? A lot of the stuff I'm finding is rather lacking in details- sand, prime, spray color, spray clear, hit the streets.

Thanks.
Doc.

 

First thing is fibergl*** cracks even small ones need to be be ground out as deep as the crack is, sometimes it’s all the way through the gl***. Covering it with filler, gelcoat or epoxy doesn’t work. Second there is no need for epoxy on a fibergl*** body that your working on at home.
The next thing is don’t use a chemical stripper on fibergl***. 40 years ago I worked at HoK in Minneapolis where we did a lot of Corvettes one was done before I started that had a problem with stripper coming out of the gl*** under the new paint. After several attempts at drying the gl*** and repainting the problem it was fixed. Since I left HoK I’ve only done mechanical strips on fibergl***, I use 120 or 80 grit on a large orbit palm sander, this is an acquired skill or so proceed with caution and don’t grind fibergl***. As good as that old paint job might be it doesn’t make sense to put all those expensive new materials over top of it and hope it will remain stable. Im not a fan of high build epoxy primer I still like Feather Fill polyester primer over fibergl*** especially for use at home
Good luck
From a retired painter/body man

 

IF , it is lmron , it should cut clean ( little gumming of the abrasive) 80 on a DA & DONT push hard , let the abrasive do its job ,fibergl*** seems to flex more than metal ( IMO) , its easy to make a wavy mess .

 

What d'ya think about getting it blasted, then? I'm trying to see if there's a soda or dry-ice blaster in the state. I wouldn't trust myself with a grinding disc...

So no epoxy, but I ***ume gelcoat is still a must?

Doc.

 

-That's my main concern. I am NOT a body guy, and I figure it'd be way too easy to do more damage than good.

But, that doesn't leave me many options...

Doc.

 

No gellcote is not required, the Polyester primer will cover that it’s actually a fibergl*** base primer. It smells like fibergl*** when you spray it, it uses regular fibergl*** Hardner.

 

Hope you get good answers. I've got a gl*** t body that'll need painted, so I'll keep watching to learn also

 

A couple ways. Feather edge the bad and make repairs.
Is sanding Imron as dangerous as spraying it?
That’s some very bad material.
Strip the car? sanding, chemical stripping, blasting.
If stripping, how much gel coat will be left?
A friend of mine restores vettes. He removes the gel coat, makes all repairs Then uses a polyester primer surfacer then gel coats
If having someone blast it, ask for references and pictures. Make sure they know how to blast gl***.
Whatever you do next is up to you.
The reason a friend of mine re-gel coats is that he feels this protects or seals the gl*** better increasing gloss and color hold out.

there are more than one correct answers to your question.

 

-This is one of my top options at the moment. Maybe not as good an overall result, but I'm in a tight budget and limited on space, equipment, and, to be honest, ability.

-It was my understanding (and corrections gladly welcomed) that Imron used an... isocyanate? Basically something like a cyanide compound, that one needed to use either supplied air, or a specific, special respirator filter for.

I do not know if that only applies to the material as it's being sprayed, or is still a factor in the cured material too.

But either way, any dust- even wood dust- should not be breathed, and any sanding, especially on an auto body, regardless of paint or coating, should be done with breathing protection.

-Good tip. There's a big difference between a rusty bulldozer and a fibergl*** car door.

-Oh sure, that's to be expected. I'm asking because I've never painted a car (well, properly ) and I want to do this right. I know just enough about some of this that I know there's a bit of "witchs' brew" to some of it, where this combo works for that guy, but didn't work for this guy, or vice versa.

On the pro side, the car, near as I can tell, needs very little bodywork- I'm sure more will appear once it's stripped, but it'll be things like pinholes. I'm hoping for not too many cracks like 440 mentioned, but if I find any, I'll fix those too.

On the con side, I've never mixed automotive paint, never used a proper spray gun, don't have a booth, and for that matter, I can't really do extensive sanding in the shop, as it's full of machine tools. (Bondo dust and fibergl*** gunk is not something you want swirling around in your $20K CNC turning center. )

Doc.

 

-Oh, good idea. Hadn't thought of that, but duh, makes perfect sense. I also have a stack of various Corvette magazines around here somewhere, I should go back through those for body-repair articles, too.

Doc.

 

I hate fibergl***, it's almost like a living breathing material. One thing I learned about old fibergl*** is that yeah, it doesn't rust, but you can bet your *** that it rots. Not where you are looking at it, but from the other side. Confirm that your bubbles are the paint releasing, and not the gel coat releasing from rotted fibergl***.

 

Another source, if you haven't tried, is StudebakerDriversClub.com & RacingStudebakers.com. There are a few guys who may have a clue. Also the Avanti club. There used to be 2, but since I have no interest in owning an Avanti - I like them n all, but don't want to own one - I can't tell you what the names of the clubs are. SDC site guys should know.
Glad to see you bringing it back to life. ! . Still Stude-engined? Resto or mod? Hey, I'm happy either way.
Marcus...

 

I have been doing bodywork all my life. I have done corvettes, steel cars just about everything you can imagine. Painted with lacquer, imron, synthetic enamel, acrylic enamel, I think I have seen it all. Just like a lot of guys here have. All I can do is word my opinion in a different way. When you say you have never done any bodywork or painted a car before, it really throws up a lot of red flags. Stripping the surface correctly can save you a lot of work down the road. I understand you don't want to spend a ton to get it done professionaly, But stripping a gl*** car with a sander is way different than stripping a steel car. Depending on the finish. In other words the type of paint. If it has been painted before, how many times? I mean how many types of paint and how many coats? You say Imron, but what is under it? It takes a feel for how much you are sanding off, in other words,stay in one spot too long ect... your into the gel-coat. If you can be-friend a bodyman you can be miles ahead by having someone to help you along. I'm not saying you cannot do this, because you can, but it's not a process we can explain on a message board. JMO. Lippy

 

I think this is the best advice given so far. Realistic and straightforward.

 

-Good point, and yeah, I'm well aware that fibergl*** can decay and delaminate.

All I can do is hope that's not the case here- the car's been under one for or another of cover (as in, a building, not just a tarp) for forty years, out of any direct sunlight, etc.

-Yep, already posted over there, too. I'm a reasonably competent mechanic, but I know I'm going to need some help with some of the oddball Studebaker minutiae. Haven't tried the racers, might check that one out too.

-Keeping the Studebaker R2 supercharged 289, which at this point is about 80% rebuilt. But no, it's not a restoration- it was my dad's car, and he wanted a good, safe, reliable driver, not a Concours-accurate restoration. We've already put in an aftermarket front suspension kit, that uses real, live spindles with ball joints instead of the kingpins, big ventilated LTD rotors instead of those skinny Bendix things, and a rack-and-pinion instead of the Rube Goldberg bellcrank monstrosity the car shipped with.

It's a HAMB-legit car, if you gents want, I can start putting the build-thread pics over here, too.

-Really, I absolutely do not want to strip it with a sander or grinder. I'll paint over what's there before I do that. Basically, the two options I'm keeping on the list is either professional media blasting (if there's even anyone in Alaska who can do it, and not treat it like a rusty bulldozer frame or something) or laboriously s****ing it with a razor blade. (Or rather, 25,000 razor blades. )

-I'm given to understand that the car was originally gold, from the factory. When my dad bought it, it was at that point painted brown, and done very badly. He had the shop he bought it from repaint it in metallic green Imron, and it seemed to be a pretty decent job. Was the brown all stripped off first? I'd ***ume so, given the description of how bad it was. Maybe they just sanded it down. I don't know. What type of paint was the brown? Don't know that either.

I can say whoever did the Imron job did it reasonably well, as it's only lightly bubbling in a very few places, after literally forty-five years.

-We have a bodyman in the family. I've already been waiting over two years for him to come over and help with it, and my neighbor has been waiting three years for him to just do a little rust repair and a few parking lot dings on a truck.

I can probably get advice, maybe even some materials, but actual, physical help? Not happening. If I don't do this myself, it's simply not going to get done.

-Of course. This is less a case of 'teach me how to do this" and more "point me in the right direction". This isn't my forté, so I want to arrange my waterfowl into colinearity before I start.

I was already pretty sure I didn't want to DA all the paint off, and that's pretty much confirmed. Interesting to hear gelcoat isn't needed- I guess I was under the impression that was pretty much always used with fibergl***. Ditto the epoxy primer.

Doc.

 

If you can't get answers that work here, try the Avanti Owners ***ociation, Intl. I think they have a website and forum.

 

No production body panel on a Corvette or an Avanti ever had gelcoat from the factory. All Vette panels, from the get go of production to the present, and all Avanti panels for the entire production run, were made by the same company. The company is Molded Fiber Gl*** Company (MFG) in Ohio. The panels are press molded and have no need for gelcoat.

Gelcoat is used on hand laid and chopper gun parts as the first coating sprayed into the mold to produce a smooth surface finish as the part is built from the outside in. Think boats, f/g hot rod bodies, etc. MFG press molded their parts from fibergl*** reinforced plastic sheet material, so it isn't necessary to use gelcoat to produce a smooth surface.

Polyester primer, aka Feather Fill, is sprayable Bondo. It was the hot tip for a high build primer back in the 80's, mainly because it was the only high build product available and suitable for block sanding, but that's not the case today. High solids sandable epoxy is the best product to use on Vette or Avanti bodies today. Sandable being the key word, as some epoxies are rock hard and not suitable for blocking. Southern Polyurethanes (SPI) makes a great epoxy product for filling and blocking on these bodies. The primary advantages to epoxy are twofold. Once cured, it is impervious to the solvents used in subsequent products. And over time it remains flexible which helps in preventing any variations in the underlying surface from telegraphing thru to the finished surface over time. Epoxy does not contain isocyanates, so a standard respirator

There is no danger of isocyanates remaining in cured urethane paints. ISO's are used as a part of the chemical setting reaction of urethane paints and primers, but they do not remain as a reactive product after curing. As mentioned, dust masks are good to use when sanding any material

It's my understanding that Imron used a particularly wicked blend of ISO's which led to it falling out of favor as more modern and less dangerous catalyzed auto paints were developed. That said, it also presents no elevated danger in sanding because it is essentially just another plastic surface once cured.

Soda blasting is a bad idea on steel bodies and an even worse idea on fibergl***. Even on steel, which is a non porous surface, there are so many problems related to fully neutralizing the residue that the major paint manufacturers refuse to warrant their products if used on a soda blasted surface. Not hard to imagine how much more problematic that becomes on a fibergl*** surface which is always somewhat porous in it's bare form. The owner of SPI puts it bluntly. He says if you use soda, please buy someone else's primers and paints so you won't be blaming me when the job fails.

Dry ice blasting is primarily a cleaning process. The CO2 freezes soft products like sealers, caulks, etc and blows them off the surface. The CO2 is non abrasive, so it's unlikely it would even touch an Imron coated surface. Besides that, the cost is prohibitive for use on a large object like a car body even if it would work to remove paint.

Running 80 grit on a palm type DA sander isn't nearly as aggressive as it might sound. Obviously, you don't want to bear down on body edges or similar features, but overall it is very easy to control the stripping process. I'd say the biggest problem to a newbie removing paint with a DA is the tendency to sand with the edge of the disc rather than keeping the pad flat on the surface. Just takes some concentration at first to avoid that mistake, and keeping it flat on the surface becomes second nature. All said, it is the safest way to strip paint from a steel or fibergl*** body.

Palm DA Sanders are available with a vacuum connection for dust extraction to address the problem of dust flying around your machine shop. By the same token, if you're doing any machining that puts mist in the air, I'd be concerned with that mist contaminating the surface of the body. I'd definitely keep the car covered with poly whenever doing any machining involving coolant

 

Good info! That's the kind of thing I came here hoping for.

-I had no idea. I'd have thought that baking soda would wash off easily with plain water.

-I was given to understand that, in a case like this, the rapid sublimation of the CO2 flake helped "pop" the paint off. But of course that's just from one article I read a while back..

-Still not thrilled with that idea. I know how I use flap discs and the like. I an see easily doing more damage than good- and as above, in that case, I'd be better off spraying over the old paint. The overall job might not last as long, but it stands a much higher chance of looking better.

-Entirely true, and I've been thinking about that. I have no other place for either the car or the machines, so I suppose the best I can do is use a cover and a lot of degreaser.

Doc.

 

I have built 2 fibergl*** bodied cars in the last 50 years. The first was a Speedway bodied 32 roadster which we did in my one stall garage and painted with some form of enamel in the early 70's. I did the prep work just like any body, painted it and over the years it has held up well, but it's been living in CA. The second was a Gibbon bodied 34 roadster which was professionally painted with Acrylic enamel in the early 90's and I see it almost every year at the LARS and it also looks good. I'm not a painter but as with any paint the key is lots of prep work/

 

Yep. I’m misspoke. Vettes we’re built in dies. Had like an extra thicker resin outer layer.
The gel coat vs polyester vs epoxy vs urethane will probably continue.
The reasoning for using gel coat is it’s hardness and sealing capabilities.
the down side is you need a gun that can shoot it.
Poly works great but still needs a gun that can handle that as well.
Some guys use epoxy but will require more coats.
I’m not the biggest fan of urethane because it’s prone to shrinkage more vs the others mentioned.

 

I just painted my Vette, third time in 40 years, and have vowed to quit wrecking it. All the cracks and mods I've done over the years are just polyester resin, sanded, skim coated with filler, prime and paint. First time was lacquer, second two polyurethane primer and top coat, no different than metal. Works for me.

 

Imron is going to be a ***** to remove with blasting, paint striper, flapper wheels. I would repair the flaws, scuff and shoot. It could become a beginner's nightmare otherwise.

 

When you say " bodywork" , I'll ***ume your using a filler material . Then your advocating gel-coating over the filler ?

 

Yep , Imron is HARD , the risk of taking off too much of whatever is under the Imron when sanding will be difficult .

 

Hey, Doc;
I'm no bodyman/etc, but on the DA; have you used one? Reason I ask, from memory of using mine decades ago, & knowing I'll have to get reacquainted w/it in the near future, is that it is *nowhere* near a body grinder(4", 4.5", 8"/9" type), palm sander, straight-line sander, or angle grinder, even when it's set on just rotary. The dual-action creates a very "soft" sanding event, & before I used it the 1st time, I just had to see how aggressive it was, so I held the disc in a gloved hand & tried to get the DA disc to spin - it didn't, just vibrated, I also stopped the disc from spinning by putting too much pressure on the DA(got impatient w/the cutting action time). IDK, maybe the air pressure was too low(small Sears 5hp, 20 gal, 220v air comp), but I was kinda pleasantly surprised to find that it was difficult to cut grooves/arcs, even in bondo. Waves may be another story, but if you're careful, a little long board time will help there later. IIRC, 'gl*** bodies were never straight when new. Or at least didn't stay that way long. ??? Don't worry, you'll still need to hand sand areas of the body. Someone can give you an idea of grit-equivalent on the hand sanding(esp using blocks of different shapes - don't use just the fingers) vs DA. Idk, but would appreciate that.
DA's seem to be fairly cheap now at HF, although I bought new mine new ~45yrs ago(& wasn't cheap), new might be as good or better than mine is/was. I was cautioned by a 3M rep to only use a very minimum amount of oil in the DA(like ~ 1 drop/day. I ***ume that requires a very dry air supply. Mine wasn't). That did cause me a little extra work later in pre-cleaning. I'm *really* liking the idea of a vac attachment for the DA. Also helps solve a problem or two. If my DA is corroded inside after decades of non-use, that's the route I'm going.
As for the dust n mist in the shop, since there is room now for things, how about making a small temp plastic "garage" w/filters for air in n out? There is a good thread on that. Solves at least 2 problems at once. & is cheap.

Metlmuncher - thanks for the info. Helpful.

Corrections welcome.

PS; Good on the Avanti mods. Improving is better.
Marcus...

 

one word of advice, if anyone starts their thing with “im no body man but..” or words to that effect, dont listen to them

 

You dont need epoxy primer on fibregl*** as it wont corrode.
Figure out if the bubbles are in the paint or gelcoat. If theyre in the paint, mechanically sand it all off, youll likely have to spend that time sanding it AFTER spending money having it stripped anyway..
If the gelcoat is bubbled, use your 36 grit disc on a grinder to dig out the bubbs.. depending on how deep you do this-
If youve dug past the gelcoat to the fibres, re gelcoat that little spot. You can either put a spot of fibregl*** back in depending on how deep (judgement call) or just some gell coat. keep it local to within the area you ground. If the bubbs arent deep to the fibregl*** you can fill the spot back in with a long strand fibre filler.
Then bodywork with your favourite filler, prime and continue the paint process as normal.
If its cracked through, yes youll haveto grind it down and re fibre it, 3 layers of fibregl***, then a coat or 2 of gelcoat, key, bodyfill, primer and paint as usual.

your also get useable advice on fibregl***ing from boat guys, boat builders or boat forums. Again, ignore anyone that tries making up there being a difference in conditions boats vs cars see therefore tecniques differ etc.

i dont know why youd put gelcoat over filler

i didnt read the whole thread, so youve likely already had this stuff mentioned.

 

weird. So will not gelcoating over the filler and stepping down to finer grades of paper then waiting the right amount of time for primer to dry.

bodyfill, use that 3m black powder to guidecoat your sand scratches, block them out, do it again (from 80 grit to 120 down to 180), prime, then sand your primer with 240, guide coat again, sand with 400 dry or 600 wet, then paint. Theres no scratches then to sink back.
fyi, polyester fillers dont shrink either, not waiting till your thumb wont dig into primer before sanding it does