When did SMC start?
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
Likes: 0
From: Forty Fort PA
When did SMC start?
I thought that the factory started using SMC in 74 but I saw a post from Lars that talked about it starting in around 82.
Before I try to repair a crack in my 75, is it SMC or not?
Thanks
Before I try to repair a crack in my 75, is it SMC or not?
Thanks
Burning Brakes
Joined: Jun 2006
Posts: 1,249
Likes: 13
From: San Angelo TX
You will get lots of different opinions on this.
From everything I have read, I believe SMC started on some panels in 1972. Your 75 would have some panels in SMC also.
Smooth on the back, it's SMC. Rough on the back, it's not SMC.
Also, the 84 and up SMC panels are a newer generation of SMC and require the newer products such as Duramix for proper adhesion.
On your 75, use the Evercoat resin that says it works with both types and you will be fine. Use it with fiberglass matting not the cloth.
Roger
Racer
Joined: Nov 2006
Posts: 435
Likes: 7
From: Wake Forest NC
You will get lots of different opinions on this.
From everything I have read, I believe SMC started on some panels in 1972. Your 75 would have some panels in SMC also.
Smooth on the back, it's SMC. Rough on the back, it's not SMC.
Also, the 84 and up SMC panels are a newer generation of SMC and require the newer products such as Duramix for proper adhesion.
On your 75, use the Evercoat resin that says it works with both types and you will be fine. Use it with fiberglass matting not the cloth.
Roger
From everything I have read, I believe SMC started on some panels in 1972. Your 75 would have some panels in SMC also.
Smooth on the back, it's SMC. Rough on the back, it's not SMC.
Also, the 84 and up SMC panels are a newer generation of SMC and require the newer products such as Duramix for proper adhesion.
On your 75, use the Evercoat resin that says it works with both types and you will be fine. Use it with fiberglass matting not the cloth.
Roger
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
You will get lots of different opinions on this.
From everything I have read, I believe SMC started on some panels in 1972. Your 75 would have some panels in SMC also.
Smooth on the back, it's SMC. Rough on the back, it's not SMC.
Also, the 84 and up SMC panels are a newer generation of SMC and require the newer products such as Duramix for proper adhesion.
On your 75, use the Evercoat resin that says it works with both types and you will be fine. Use it with fiberglass matting not the cloth.
Roger
From everything I have read, I believe SMC started on some panels in 1972. Your 75 would have some panels in SMC also.
Smooth on the back, it's SMC. Rough on the back, it's not SMC.
Also, the 84 and up SMC panels are a newer generation of SMC and require the newer products such as Duramix for proper adhesion.
On your 75, use the Evercoat resin that says it works with both types and you will be fine. Use it with fiberglass matting not the cloth.
Roger
Burning Brakes
Joined: Jun 2006
Posts: 1,249
Likes: 13
From: San Angelo TX
I am not sure if there is really any reliable documentation that gives a definite answer but I have sure seen some printed information that has flat out been wrong.
Melting Slicks
Joined: Jul 2004
Posts: 2,577
Likes: 2
From: Long Island New York
My 1977 Chevrolet Service manual states on page 2D-25 under body repair s "The following gives information necessary for repair of collision damage on Corvette bodies. Included here is information dealing with availability of repair panels, general installation procedures for installing panels and repairing damage to the body. Repair of fiber glass reinforced plastic bodies can be a relatively easy matter if precautions are observed." This would lead me to believe that up until 1977 they were still using FRP panels. That is what my car is made out of and that is the materials and procedures I am using to do mine with. When I called Eckler's about this originally they told me that everything from 73 and up was SMC, however if you watch their Fiberglass Repair DVD Volume 2 that I bought from them, they are clearly doing a FRP fender repair on a 1977 Corvette.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
The first SMC panels were the rear quarter panels starting in `71. By 74 all external panels had been changed over to SMC. Now SMC itself has evolved and there are differences as the years have passed.
I quote from " Birthplace of Legends" by Peter Licastro "During 1970, another improvement in fiberglass technology, called low-shrink Sheet Molded Compound (SMC), was introduced at General Tire`s Marion facility. Parts made from low-Shrink SMC were almost as smooth as steel and pre-painting preparation at he Corvette plant involved only scuff sanding and solvent wipe. The rear quarters on the 1971 Corvette were the first parts manufactured using this system. All body components on the 1974 model were fabricated using the SMC process."
I quote from " Birthplace of Legends" by Peter Licastro "During 1970, another improvement in fiberglass technology, called low-shrink Sheet Molded Compound (SMC), was introduced at General Tire`s Marion facility. Parts made from low-Shrink SMC were almost as smooth as steel and pre-painting preparation at he Corvette plant involved only scuff sanding and solvent wipe. The rear quarters on the 1971 Corvette were the first parts manufactured using this system. All body components on the 1974 model were fabricated using the SMC process."
Melting Slicks
Joined: Oct 2002
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From: I may be getting old but I refuse to grow up
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Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
My 1977 Chevrolet Service manual states on page 2D-25 under body repair s "The following gives information necessary for repair of collision damage on Corvette bodies. Included here is information dealing with availability of repair panels, general installation procedures for installing panels and repairing damage to the body. Repair of fiber glass reinforced plastic bodies can be a relatively easy matter if precautions are observed." This would lead me to believe that up until 1977 they were still using FRP panels. That is what my car is made out of and that is the materials and procedures I am using to do mine with. When I called Eckler's about this originally they told me that everything from 73 and up was SMC, however if you watch their Fiberglass Repair DVD Volume 2 that I bought from them, they are clearly doing a FRP fender repair on a 1977 Corvette.
Burning Brakes
Joined: Jun 2006
Posts: 1,249
Likes: 13
From: San Angelo TX
Race Director
Joined: Apr 2009
Posts: 19,294
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From: Charlotte NC
Instructor
Joined: Jun 2005
Posts: 221
Likes: 0
There was a stress crack in the left front fender right where it mated to the urethane bumper. I have ground the crack down and out but it is really to deep to just use filler. I need to build up some mat and resin then filler or adhesive. So what materials do I use, poly or SMC?
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
There was a stress crack in the left front fender right where it mated to the urethane bumper. I have ground the crack down and out but it is really to deep to just use filler. I need to build up some mat and resin then filler or adhesive. So what materials do I use, poly or SMC?
DUB
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
GREAT PHOTO....Thanks.
It is hard to say actually how deep you went.
How much did you grind off???
Are you sure that you got the crack out all the way????
Is the depth of the notch ground on the edge your major concern???
Also...where is your IMPACT BAR???? I should be able to see it and I am not. That metal retainer that is pop riveted to the flange of your fender gets secured to it via the large hole in this retainer. Without this retainer secured...any repair you do will fail in time.
PLEASE answer the questions to the best of your ability.
DUB
It is hard to say actually how deep you went.
How much did you grind off???
Are you sure that you got the crack out all the way????
Is the depth of the notch ground on the edge your major concern???
Also...where is your IMPACT BAR???? I should be able to see it and I am not. That metal retainer that is pop riveted to the flange of your fender gets secured to it via the large hole in this retainer. Without this retainer secured...any repair you do will fail in time.
PLEASE answer the questions to the best of your ability.
DUB
Instructor
Joined: Jun 2005
Posts: 221
Likes: 0
At the deepest I am down about .125
I am pretty sure that the crack is totally ground out but I can dye pen to make sure. Also have ultrasound available.
My major concern is what materials do I use for the repair. Stuff for SMC or stuff for the older fiberglass? Information seems contradictory in this area.
Second concern is how to build up material. I plan to layer mat, sand and fill.
If by impact bar you mean the steel U channel that is bolted to another steel U channel that is bolted to the frame, it is there, just the attaching bolt is removed.
Answered to the best of my ability.
I am pretty sure that the crack is totally ground out but I can dye pen to make sure. Also have ultrasound available.
My major concern is what materials do I use for the repair. Stuff for SMC or stuff for the older fiberglass? Information seems contradictory in this area.
Second concern is how to build up material. I plan to layer mat, sand and fill.
If by impact bar you mean the steel U channel that is bolted to another steel U channel that is bolted to the frame, it is there, just the attaching bolt is removed.
Answered to the best of my ability.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
Thanks for the reply.
Just make sure that the large bolt that goes through this steel retainer that is pop riveted to your fender is in place and secure.
IT IS IMPERATIVE that you know if the crack is no longer there or not.
If the crack only effected an upper portion of the adhesive...and when you ground it away it 'chunked ' away and stopped....AND you can not manually make the crack appear and be seen...or with your equipment verify that it is not there...then ....
Honestly...I would fill it in withe the Vette Panel Adhesive and move on. 1/8" is nothing...especially in the seam area, The effort and benefits of apply resin and fiberglass mat is kinda pointless. You are not adding enough to provide any major structural strength. It would add something...but if the crack is gone...I know I would not laminate it. And it does not appear that you ground away from the seam drastically.
Your photo did not look like you ground down that far. And I have ground down much more than what you have done...And used the VPA and NEVER had it come back and crack....BUT ...I also knew I was not covering over a crack.
BUT...if you want to apply mat and resin...I use the WEST SYSTEMS epoxy resin.
DUB
Just make sure that the large bolt that goes through this steel retainer that is pop riveted to your fender is in place and secure.
IT IS IMPERATIVE that you know if the crack is no longer there or not.
If the crack only effected an upper portion of the adhesive...and when you ground it away it 'chunked ' away and stopped....AND you can not manually make the crack appear and be seen...or with your equipment verify that it is not there...then ....
Honestly...I would fill it in withe the Vette Panel Adhesive and move on. 1/8" is nothing...especially in the seam area, The effort and benefits of apply resin and fiberglass mat is kinda pointless. You are not adding enough to provide any major structural strength. It would add something...but if the crack is gone...I know I would not laminate it. And it does not appear that you ground away from the seam drastically.
Your photo did not look like you ground down that far. And I have ground down much more than what you have done...And used the VPA and NEVER had it come back and crack....BUT ...I also knew I was not covering over a crack.
BUT...if you want to apply mat and resin...I use the WEST SYSTEMS epoxy resin.
DUB
