73 corvette panel joint

W

walkvet48

I am preparing my 73 corvette for paint and need an opinion on how to do the bond joints on the front fenders and rear quarter panels. The traditional method seems to be to grind a dish or bevel about 2" wide along the length of the joint and then fill with fiberglass mat and resin. I have heard of a second method that uses Evercoat Vette panel adhesive in place of the mat and resin.

Have any of you used the second method and if so what's you thoughts on this process?

Thanks

George Walker
 
3 in wide , feathered out , epoxy resin and mat , finish off with evercoat panel bond adhesive if needed. DO NOT use a soda can for making a grove !!!!!!!!!! any sharp line will ghost back on you .
 
shine, thanks for the info. Kind of figured that was gonna be the way to go. Been following your posts for some time now and will copy your system of epoxy primer and concept ss. Have not decided whether to use clear or not. Color is yellow (no metallic). Car will be flight judged so not really going for that deep deep look. Trying to make it look like lacquer.

Thanks again
 
Last edited:
I would think that it is actually OK to use a soda can (or like shape) to BEGIN the panel joint preparation process, if a person feels comfortable doing this.

But that would only be step one, step two would be to feather back the edges of the "U" shape created by the process with a sanding block or DA sander, until there is a nicely tapered edge, all done with grit 80 or coarser, our usual technique involves 40 grit at this stage.

The area of glass removal should be shaped to allow the repair material to taper off as smoothly as possible into the existing panel, this will help keep the edge of the repair from becoming visible after lots of hot/cold cycling.

Anyone who advocates leaving a sharp line in the repair of virtually any material repair requiring a seamless appearance probably has a poor understanding of the fact that expansion coefficients will vary between materials. Even if the exact same material as the base material could be utilized, the expansion coefficient would still be different because the car is old and the material is new.
 
Last edited by a moderator:
no telling who came up with it. no doubt they thought they reinvented the wheel but they knew nothing about glass work . it is the sharp line that caused the problem in the first place. a 3 in rolock on an angle grinder works best. but i have learned my lesson about giving info on vette sites.
 
Well, to throw my 2 cents in here, BE CAREFUL IF YOU USE EPOXY...here's the rule...epoxy sticks to polyester or smc, but polyester (bondo or most fillers) don't stick well to epoxy...I don't care how it's done. Also the epoxy expands and contracts at a different rate, and if not buried enough WILL GHOST...I assume the panel adhesive is used as a barrier coat between the two for adhesion...hmmm...epoxy, adhesive, filler ...3 different expanding matierials...another approach to consider is using vinylester resin instead of the epoxy (on pre smc) and get your first coat of filler on sanded resin within 24 hours for better adhesion...I like shine's approach for smc (just to clarify between old and newer style corvettes, however, on polyester bodies, it has never worked for long for us. We have also had trouble with exposed adhesive to primer areas looking different than filler areas MOST of the time. I believe alot of the ghosting you see on panel replaced areas is actually adhesive not covered by filler...Just some ideas to ponder from an old guy who should probably keep his mouth shut but sometimes can't.
 
When I have concerns about adhesion between two dissimilar materials, a double coat of epoxy primer seems to answer the question very nicely. There isn't much it won't adhere to, with the obvious exception of TPO and polypropylene.

I believe most repair procedures could not be hurt by applying epoxy primer between material stages, the only disadvantage being the extra time involved.
 
crashtech;2009 said:
When I have concerns about adhesion between two dissimilar materials, a double coat of epoxy primer seems to answer the question very nicely. There isn't much it won't adhere to, with the obvious exception of TPO and polypropylene.

I believe most repair procedures could not be hurt by applying epoxy primer between material stages, the only disadvantage being the extra time involved.

I absolutely agree and that's how we do it...excellent adhesion on both sides, and no build, so no possibility of dissimilar movement
 
walkvet48;1932 said:
shine, thanks for the info. Kind of figured that was gonna be the way to go. Been following your posts for some time now and will copy your system of epoxy primer and concept ss. Have not decided whether to use clear or not. Color is yellow (no metallic). Car will be flight judged so not really going for that deep deep look. Trying to make it look like lacquer.

Thanks again

We have had good results with using a top notch ss with 30% flatner in the final 3 coats, cut and buff as usual...judged on 2 cars and no deduct at all where you usually get at least 5 to 20 points deduct for a buffed ss urethane.
 
Fly, if you would ever care to detail the process of using flattener in your topcoat combined with polishing, I think it may well deserve its own thread!
 
I think there are are a lot of ways to do the seams but I think the bottom line to prevent a problem is make sure you an extreme Vgrove when you are done.

This vette and the last two I did all c-3's the V grove was about 2.5 to 3 inches wide and I always go as deep as I can, this one was a good inch deep and used a 24 grit 3" roloc grinder.
I then brushed three coats of epoxy over a full day and for the third time in a row used SMC filler adhesive. Sanded it and sprayed epoxy over and then 2K primer.
I learned the SMC filler deal from a vette shop in Ohio and it is a lot easier then, I had been doing.

Before I was using Duramix to fill the seam over the epoxy and then when done coating the epoxy., doing it that way since about 1986 when Duramix came out.

Before that I would use epoxy fiberglass resin with fibers added over a non epoxied joint and when done epoxy over the sanded glass and apply the filler.

Never have had a problem with seams and these are three extremely different ways and that leads me to believe, its all V-Groove.
 
flynams;2006 said:
Well, to throw my 2 cents in here, BE CAREFUL IF YOU USE EPOXY...here's the rule...epoxy sticks to polyester or smc, but polyester (bondo or most fillers) don't stick well to epoxy...I don't care how it's done. Also the epoxy expands and contracts at a different rate, and if not buried enough WILL GHOST...I assume the panel adhesive is used as a barrier coat between the two for adhesion...hmmm...epoxy, adhesive, filler ...3 different expanding matierials...another approach to consider is using vinylester resin instead of the epoxy (on pre smc) and get your first coat of filler on sanded resin within 24 hours for better adhesion...I like shine's approach for smc (just to clarify between old and newer style corvettes, however, on polyester bodies, it has never worked for long for us. We have also had trouble with exposed adhesive to primer areas looking different than filler areas MOST of the time. I believe alot of the ghosting you see on panel replaced areas is actually adhesive not covered by filler...Just some ideas to ponder from an old guy who should probably keep his mouth shut but sometimes can't.

I need to clarify the above...I meant epoxy RESIN, which we never use on vettes unless it's smc, and then we use smc specified resin (fortified epoxy)...fillers do not stick to epoxy resin...and as far as I'm concerned, not to any unscuffed epoxy primer either...the resin has different skinning properties than the primer and is incompatipable with fillers...
We are getting China whored epoxy at some places on the internet. now. and it is really crap...Buy American...course you should anyway hehehe
 
crashtech;2017 said:
Fly, if you would ever care to detail the process of using flattener in your topcoat combined with polishing, I think it may well deserve its own thread!

Doesn't need a thread...Rules are solid single stage mix in 30% flattener (we mix it for all 6 coats so there is consistancy) won't work for clear, so take my word and don't try it...be forwarned, it takes a real vette freak to appreciate this approach when all other cars are deeper...but if you want 1000 points, there is no other way...only other thing is to be sure to mix each gun refill before pouring...we also have skipped the final polish if the car is to be judged outside. Course all this is preparation for one judged show to filght the car. Take a car like that under the lights and it will look like crap...in fact you might think it looks like crap anyway, cuz factory paint was crap by today's standards
 
Barryk;2018 said:
I think there are are a lot of ways to do the seams but I think the bottom line to prevent a problem is make sure you an extreme Vgrove when you are done.

This vette and the last two I did all c-3's the V grove was about 2.5 to 3 inches wide and I always go as deep as I can, this one was a good inch deep and used a 24 grit 3" roloc grinder.
I then brushed three coats of epoxy over a full day and for the third time in a row used SMC filler adhesive. Sanded it and sprayed epoxy over and then 2K primer.
I learned the SMC filler deal from a vette shop in Ohio and it is a lot easier then, I had been doing.

Before I was using Duramix to fill the seam over the epoxy and then when done coating the epoxy., doing it that way since about 1986 when Duramix came out.

Before that I would use epoxy fiberglass resin with fibers added over a non epoxied joint and when done epoxy over the sanded glass and apply the filler.

Never have had a problem with seams and these are three extremely different ways and that leads me to believe, its all V-Groove.

You say 1 inch deep, where is the body this thick, or did I misunderstand ? (as usual,lol)
Brush 3 coats of epoxy, is that resin or paint ?
SMC filler adhesive, is that a specific brand or a generic term?

Thanks !
 
Perhaps bad choice of words, we are not grinding the body only the factory bonding seams, I never measured but would guess some spots will go an inch, some maybe only 1/2 inch and every where in between.
Point is you want them as deep as you can go for a long lasting repair.
Strength = no ghosting lines.

I brushed with epoxy paint and the SMC was Fiberglass/Evercoat, don't remember the number.
 
WOW, I would have never thought that the seams would be that thick! I just assumed they would be 3/8 inch or so.

So much to learn, so little time :(
 
i use west systems marine epoxy . it is about the best i have ever found. the reason i went to epoxy is the adhesion. i have seen many polyester resin repairs pop off. there is no chemical bond , just mechanical to the scratches. epoxy will adhere when all else fails. the vette bond adhesive (870)seems to work really well although i am leaning towards the quantum hybrid epoxy filler. have not tried it yet. i use spi epoxy for build just because i hate polyester and urethane primer. it has worked great for me and no shrinkage or swelling. the only thing that showed on the 57 was that dynatron polyester junk i used on minor stuff. never again . dynatron can kiss my grits . but like barry i think the #1 reason for ghosting is sharp lines. but you cant tell corvette guys this if they are into those vette sites heavy. they will coke can them and fill. then blame it on the painter . i will not touch a car that has the body work done. no matter the agreement you can bet when seen at a show the owner will whine how the painter screwed them. been there done that. but to each his own.
 
I've used the west and USC, use to make a epoxy resin but I think they stopped.
Trying to find an epoxy fiberglass resin seems to be like pulling teeth, jobbers won't stock it because to expensive, so you need to twist there arm to order from their warehouse and hope their warehouse has it in stock.
 
i order direct from west . i have also used taps warehouse resins but i think west is better. the west system 105 has a lot of different additives for making different fillers and such. they seem to put a lot of work into it over the past 5 years.
 
Back
Top