jr73

I bought my 73 with most of the paint stripped. The owner said he used a stripper designed for fiberglass but Im wondering if he went too far. Most of the car feels fuzzy and being a Corvette virgin im not sure how far is too far. A Vette guy I talked to said the guy may have taken off the Gel coat and to re-apply that will be a nightmare. Am I in trouble?

jr73

About half the car looks like this, not as raw.

DUB

First off the car was never gel coated from the factory. And secondly...yes...you have issues that need to be addressed so NO contaminants get into the exposed fibers that you have showing right now.

I would begin by covering the fiberglass exposed panels with plastic..AS LONG AS IT IS INSIDE & UNDER CONTROLLED CONDITIONS!!! Do not let it get wet...if at all possible. A chemical wash can be given to it...I prefer using acetone...but only when you are ready to start doing any bodywork on this/these exposed panels.

Next...I would do all of my body work and re-work the bonding seams ( unless you want them to show up later). Then I would gelcoat all press-molded fiberglass panels and then go from there.

I know that others may "chime-in" with their thoughts and views....And I am not saying that what I wrote is the ONLY way of doing it. But seeing how I do this for a living and have to warranty my work...that is what I would do.

And applying gelcoat is no more of a "nightmare" than anything else. It is a product that requires attention the same as primer. Yes it is harder...but it is not concrete...so do not let that intimidate you from getting your car the way you want it. Many people have views and opinions on what "they" think about this or that....and what "they" think sometimes is controlled by what "they" are capable of doing correctly. So if it out of their comfort range..."they" often times will try to not talk about it due to it being harder or requiring a more precise effort on their part...where "they" often times either do not want o do it..or are incapable of doing it CORRECTLY.

For what it is worth...I have run into this issue numerous times...and it is NOT the end of the world...unless you go and spill a gallon of used oil and spray WD-40 all on it.

DUB

porchdog

agree with dub. fiberglass has to be squeaky clean and dry . we only have different top coats , dub uses gelcoat i use epoxy . either is acceptable but sealing with a urethane primer is not nor do i use a polyester. you have to create a barrier . " new glass " basically .

jr73

Thanks DUB,
for my information what did they use if not gel coat?
(remember Im a Vette virgin)

crazywelder

An original '73 body should be all SMC, not fiberglass. So make sure you topcoat it with a SMC compatible product. Epoxy is my preference.

DUB

Nothing. The panel was made in a way that the resin used was (as I have been told) applied to the inside of the mold and then the part made. So this top thin layer of the outer panel was basically the resin that allowed the panel to be prepped for priming and paint. So having a layer of gelcoat..like on a handlaid part of today..it does not have that.

Also GM...back then...did not have concerns on how well the body and paint held up. Due to owner input and technology...improvements have been made that make it so current body materials and paint can last for a long time...because GM knows that people keep Corvettes and want them to last as long as possible...but they still have issues...because GM wants you to buy a NEW Corvette every so often. That's their business...selling cars.

It is like the new SMC panels are manufactured with a very thin layer on the outside of it that allows for adhesion of the new types of adhesives used for bonding...which is why it is important on a new SMC panel NOT to grind it...but it is better to hand scuff it and not destroy this layer. It all deals with chemical adhesion and not so much a physical adhesion. And if you doubt me...separate factory bonded panels and you will RARELY see a grind mark.



Incorrect. 1973's still used press-molded fiberglass panels...because the rear section of the car was still of the era of chrome bumpers. This I know for a fact because I have dealt with numerous 73's. AND...YES...I have seen some cars with the taillight panel being that of the "early" SMC style panel. Also..if some of the other panels are "SMC" so-to speak. This early formulation of new type of body material is different than that of what is known today...and with that being said...this early type of new body material can be treated differently than what is being produced today. It all is dealing with the chemical formula of the resin used in the molding/manufacturing process for these "early" panels versus that of today's SMC panels. Similar to how the 1973-1974 urethane bumper material is completely different than that of today's urethane bumper material.

As for coating a SMC type panel with epoxy...I do AGREE that it is quite acceptable and often times provides a desired end result.

DUB

crazywelder

I have a '73 in the shop for the past year that is 100% early smc, there is no press mold glass in this body. I bought a used hood and it's smc as well. Look at jr73's pics, the large chunks of strand are indicative of the early smc. Any smc requires a release agent and that is where the compatibility problem lies.

Back in the day we were GM trained to use only epoxy adhesives but regular top coating materials (lacquer/enamel) were all that existed. Quality and longevity had different definitions back then.

Still, I would not recommend gelcoat on any form of smc and risk failure. Epoxy would be the safe way to go.

markids77

JR73 posted a few different photos in the General section... those appear to show panels which have been sanded very aggressively and are now quite thin... one shot shows a hole in the top surround. Perhaps he will post those here as well so he gets good input about doing a satisfactory repair.

crazywelder

I just looked at them. Sanded too far.

DUB

Not doubting that your car is all early SMC. But I have had 73's in my shop that were definitely press molded...mainly the rear clip panels including lower exhaust filler panel

YEP...I agree that things have changed a lot. Kinda like how using "red cap spot putty" was the only thing available until they came out with catalyzed spot putty. Boy-oh-boy...I do remember the old lacquer -acrylic enamel days.

I also agree that using epoxy on SMC is an acceptable standard and practice. But even then the epoxy can fail to adhere for an extended period of time...much like what can occur on a 1984-1985 body. But often times that can be attributed to moisture contamination due to being in a high humid region of the country....or the car being covered with a car cover outside in the elements and allowed to sit and be neglected. Nothing will stick to a surface that has a contaminant in it...or on it.

DUB

jr73

Is this the pic you speak of? Im not sure where the hole came from but there is a lot of damage on this car and Im assuming this is part of it.

porchdog

when chemstrip is used it weakens the surface which in turn makes removing the top layer of resin easy. but not a disaster . i would finish removing the paint then build a new surface with epoxy primer.

markids77

That's the one. I believe that panel is so thin you would have to laminate the hole from the underside first to have enough thickness to build from. If the entire panel; or a large section of that surround is thin you need to address that somehow before paint because simply leaning on it to tune the engine might crack it.

jr73

Is there a required thickness to these panels? As a machinist I have the tools to measure it if I know what dimension to look for.

markids77

Probably the easiest area to reach with a caliper is under the gas filler door. Remove the lid and measure the lip it screws to. All panels should be close in thickness.

DUB

jr73,
I would not get so concerned about the panel thickness being consistent. Because they are not consistent. Some areas will be thicker and some areas thinner. And as you being a machinist...with the two molds/dies used for making the part. If they are set off a little bit...due to shape of the part being made...you can have some edges be thick and some be thin.

DUB

markids77

True enough, but I would hope for a thickness greater than 1/16 or so? It appears to me that the ragged edge of the hole in JRs last photo is vanishingly thin; certainly thin enough to put an elbow through if one were to lean on the surround right there. Or perhaps the resolution in my 14 year old CRT monitor is leading me astray here?

jr73

I'll try to get a better pic of that area

jr73

I measured the area with the hole in the surround and it came out to a thickness of .111