72 NOS fiberglass IDhelp

[Bernard S.]

I am planning to buy some NOS rear panels for my 72 coupe. I have located some sources, but am not sure the panels are correct. ( black vs sheet molding compound, Rockwell vs Owens Corning, etc.) Any help with identifing true 72 NOS is appreicated

Thanks

[Wayne W.]

Re: 72 NOS fiberglass IDhelp

For 72 that could be interesting since some panels are the early SMC type or Genite made by General Tire. Other panels are the former FRP panels used in earlier production. You should be able to tell the difference by looking closely at the original panels. I think that by 72 most rear panels would have been the newer materials. The SMC or Genite panels are light gray, tend to be a little thicker and have a smoother apperance. On the underside you will see little or no fiberglass strands on the panel surface. The old FRP will be darker, nearly black and have visable fiber strands.

[Norris W.]

Re: 72 NOS fiberglass IDhelp

I've always been of the impression that SMC parts didn't commonly hit production until 73. I've only owned 1, which a subsequent owner got rear ended in and I'm certain it was PM glass all the way. Incidentally, I've never seen the term FRP used before. Does this mean "fiberglass reinforced polyester" in the older PM glass, and is it a common description?

[Wayne W.]

Re: 72 NOS fiberglass IDhelp

SMC like panels started filtering into the mix as early as 70. Actually it is difficult to distinguish between the so called Genite and SMC in the early cars. The first panel to be introduced was 69 doors. FRP just stands for Fiberglass reinforced plastic which is technically true for SMC also. Maybe I should have used the term polyester.

[Norris W.]

Re: 72 NOS fiberglass IDhelp

Hmmmmm, well maybe I'll learn something here. Are you saying that all 69 doors use a different glass than the PM on the rest of the car? I have 5 69 cars, (actually 6 if you count a totalled parts car) and a 70 and a 71. I've never noticed any difference in any of the glass on any of these. 2 of the 69's are still as naked as they've been for years, so they'll be easy to look closely at today.

Since we're talkin' glass here anyway, one thing that I've always wondered about is the reason inconsistencies in glass color of the midyear glass, especially in the earlier cars. One of my 63's is white, another all grey, and I keep hearing about cars being mixed. I'm also aware of some post 63 cars that were back to all white, although I've never seen one. Was the difference in color just a result of inconsistent materials supply or intentional for some reason?

[Wayne W.]

Re: 72 NOS fiberglass IDhelp

The change to the new material started in 69. In general the early ones have old style polyster fiberglass. Sometime in the year they started installing the newer type. I have seen a couple that had one of each. As for the color of 63-67 glass, there seems to have been a conscious effort to darken the color to near black at least after 65. This I think was an effort to reduce the blackout problems. Certainly they did this on some parts throughout the mid-year production. For example spare tire carriers and fan shrouds were dark even on the white glass cars of 63-65. But there also was obviously a lack of concern on the part of the manufacturers as the colors varied greatly. So it appears that at least early in the mid-year production it was just a lack quality control or a lack of a specification. But later on, most were dark even though there were different shades of dark.

[Norris W.]

Re: 72 NOS fiberglass IDhelp

Wayne, I gotta tell ya', I don't think there was ever an SMC panel put on a Corvette by GM before 1972, and I've never seen a pre 73 with SMC myself. As far as 69's I've got 5 coupes of my own and a 6th junker as a parts car. I've also got a 70 roadster and a 71 coupe I've seen 4 of the 69 cars totally naked and all 4 fenders on a 5th are naked as well as the parts car being busted up pretty well, showing slivers of glass at all positions. I've also stripped the 70 and the 71 and there was no SMC anywhere. Just to get a second opinion, I called a local guy who set up the Bloomington workshops until several years back and actually taught the fiberglass workshop himself for several years. He's had a full service Corvette collision/parts/restoration shop since the 60's and he says no SMC before 72 with a few rear taillight and valance panels on very late cars, which is about what I thought with the exception of the late 72 stuff. So for what little it's worth, that's my opinion.

[Wayne W.]

Re: 72 NOS fiberglass IDhelp

You have yours and I have mine, you know the joke every body`s got one.

You will notice that I did not distinguish between SMC and Genite. The reason is that it is difficult to distinguish between them. Genite is most likely the material that is actually used on the 69-71 cars. Believe me some 69 cars, at least late ones, had the new doors. On the 70-72 more of the panels were substituted as they became available. Now all of this is from years of experience working on these cars. But if you need more proof, I quote from the book Building A Legend, by Peter J. Licastro. " In 1968 the Chemical / Plastics Division of the General Tire and Rubber Company introduced a low shrink wet resin system , known as Genite"..... General Tire became a major suplier of Corvette body components to the St. Louis assembly plant." " During 1970, another improvement in fiberglass technology, called low-shrink Sheet Moulded Compound (SMC), was introduced ..... The rear quarter panels on the 1971 Corvette were the first parts manufactured using this system."

[Bernard S.]

Re: 72 NOS fiberglass IDhelp

I have been following the respones between you and Norris with interest. The reason for my initial post was because I have a 72 BowTie car which recieved some damage to the rear. I have been searching for some NOS panels to repair the damage and I have received the same questions about the type of glass from various vendors. The vendors also are split as to when the type of glass was changed. I have a 71 and another 72, and there is clearly a different type of glass in the rear on those two cars. But the 72 might have been repair at some time in its life. Too bad these old vettes can't talk - what stories they could spin. The BowTie car is at a vendors shop and I can't remeber what the glass looks like, but I probably would not have noticed the difference anyway.
I would like to continue to research this subject and any help would be appreciated.
Thanks

[Wayne W.]

Re: 72 NOS fiberglass IDhelp

You should be able to tell what was there by looking at the old panels. It is almost certain that most of the panels on the rear of the 72 would be of the genite or SMC construction. The genite panel is light gray and has fibers , but less on the surface than the polyester type. SMC panels tend to have larger coarse fibers and they are located exclusively in the inner sandwich. Now because undamaged panels are basically the same color and are sand blasted on the under side it becomes harder to tell, but you should see some fiber on the Genite panel. On the 71 you could find either the polyester or the Genite. The color is obvious once you learn what to look for. On the 71 you will probably find a mixture and some parts may be the polyester. Some have Genite panels and polyester bonding strips. The polyester panels tend to be dark gray to Black.