'72: Fiberglass Type Identification

[Patricia Brown]

Hi,

From what I gather, a '72 model may have FRP or SMC or the in-between "genite" for its panels. Is there a panel on the car that is FOR SURE a particular type, so I could use it as a reference? For instance, would the rear top panel be genite for sure? All the 'glass on this car matches and is a light grey color, except for the firewall which is black and you can see (and feel!) the individual 'glass hairs, and the tail light panel which was very different, and I suspect, SMC. It was very slippery and felt thinner, more dense, and felt rather like plastic and had a grey marble effect. I do not know if that panel was a later replacement, which I suspect as it had really strange glue holding it on (not very well). So, does that sound like SMC? Does the rest of the car, light grey in color and quite different from that slick, plastic-like tail light panel, sound like FRP or perhaps the genite stuff? Regardless, WILL STANDARD FACTORY-STYLE POLYESTER ADHESIVE WORK ON GENITE or whatever the panels are, so long as they are not SMC?

Thank you!
Patricia

[Wayne W.]

Re: '72: Fiberglass Type Identification

By late 72 many panels were SMC. The rear panel that you describe sounds like a later SMC replacement. The black panel that you describe is polyester based which is the earlier style like the 68-69 cars. As genite or SMC became available it was worked into production. The term FRP is Fiberglass Reinforced Plastic. All panels are FRP.

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Thanks Wayne.

So the firewall is black fiberglass, the tail light panel likely SMC. So is the light grey color everywhere else genite? If it is, would standard fiberglass repair materials (polyester-based) work on it?

Patricia

[Chuck S.]

Re: '72: Fiberglass Type Identification

For SMC panel replacement, you'll have to use modern adhesives like Lord Fusor 127EZ or 128EZ. If you have cracks to repair, you can use 100EZ or 101EZ. They also have a reinforcing mesh to use with the adhesive, and the adhesive can be finished like body filler. The Lord site also has some download tutorials for using their products.

I'm not certain about Gennite...Wayne should correct me if I'm wrong, but I BELIEVE the polyester adhesive will work with Gennite panels. If you want to be certain, use modern adhesives for all your repair work; the new adhesives will work for everything, but polyester based only works on the old stuff.




Lord Fusor

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Thanks, Chuck.

I actually have some 127EZ and have used it, but I would prefer to use the old polyester stuff, if I can but verify what sort of 'glass I'm working with. I'm pretty sure it's note likely SMC, and it is light grey, so I'm thinking perhaps genite. Now I just need to find out if gennite can be adhered with polyester factory-style glue.

I was hoping there is a panel on a '72 that is FOR SURE gennite so I could have a reference.

Patricia

[Chuck S.]

Re: '72: Fiberglass Type Identification

My 70 has gennite panels on the doors and the T-tops; it's a light gray with occasional traces of black marbling through the material. As Wayne said they worked Gennite into the cars as production of the different panels switched to the new material.

Without standing there looking at the car, it's impossible to say FOR SURE that the panels are Gennite, but SMC was not used for production until much later. The tail light panel is probably a later replacement used in a repair. Check the bonding strips and spoiler/fender/tail light panel joint area for tell-tale collateral damage.

You probably know what polyester adhesive looks like...it's a black, heavy, paste-like material; any excess rolled out of the joint when the panels were assembled making rounded scallops in places along the joint. If a lot squeezed out, it might slump and/or fall off, but it didn't "run".

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Chuck,

Yeah, the whole rear end was messed up, including the quarter panel-to rear deck bonding strips ripped off. So I agree likely the tail light panel was SMC and was a later replacement. It was definitely marbled, thinner, very smooth, and felt kind of plastic-like.

On my '72 all original panels have a pink glue gushing out the seams and lovely "glue icicles" hanging beneath the car at the seams. Would this pink glue give any clue to the composition of the 'glass? I see no black glue.

I once took a '75 front clip off a '75, and to be honest, the grey fiberglass looks very similar to my '72's grey fiberglass. I'm assuming it can be counted on that the '75's nose was SMC (correct?), so if mine looks like that, perhaps it's SMC, too?

Wish I could just post a picture here.

Thanks,
Patricia

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Oh, I should add that I have the Fusor 127EZ and was planning to just use it to cover my bases and not have to worry about what kind of 'glass I have, but what has me wishing to avoid it is its product info sheet states to avoid placing polyester-based filler over the glue or it will blister. While I don't plan to smear body filler or whatever directly over mass glue, I would imagine when I glue a new quarter panel on the car and lay in the mat and resin over the bond, that the polyester materials may touch a bit of glue, and I dread to think of it blistering. Also, I will need to gel coat over my repairs, and gel only sticks to 'glass or polyester materials, not this glue. So I'm kind of backed into a corner on this epoxy. I'd sure like to stick with original-style polyester glue, but I wish I could know exactly what sort of panels I'm working with.

Here's a practical question: What if I have SMC panels but incorrectly think they're standard 'glass and then use polyester adhesive. Will it be obvious it's not sticking? Would there be a way I could tell, or will it not cause problems until later?

Thanks for the help,
Patricia

[Chuck S.]

Re: '72: Fiberglass Type Identification

In my opinion, the pink adhesive is a different material than the old polyester adhesive.

To be safe, I would use the Fusor. I'll do a little more research on the Fusor for you; once the panel is bonded on, you may be able to handle the seam as a "repair" using the 101EZ and reinforcing mesh to "glass" the seam. The 101EZ can then be finished like body filler, or you can use body filler over the Fusor without problem. Body filler, or glassing the seam may not be necessary.

In spite of all the discussion about gelcoating, I believe I would forego gelcoat over Fusor because it's a different animal than the old polyester (good news, bad news?). If you order any repro panels, that's a different matter because you WILL get the old polyester fiberglass for a 72, and in the case of some vendors, you had BETTER gelcoat...repro panels will resurrect your problem all over again.

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Chuck,

I've got Sermersheim quarter panels, tail light and exhaust panels all on order. They are, of course, the old-style polyester fiberglass and gel coated both sides. So, if my rear top panel is really SMC and I am attaching polyester quarters, would polyester glue work?

Patricia

[Chuck S.]

Re: '72: Fiberglass Type Identification

I would NOT use polyester adhesive on an SMC panel. Your thread has prompted me to rethink using polyester adhesive on one of my doorskins that needs rebonding in one area.

To answer your earlier question, if polyester adhesive is used to bond an SMC panel, you may not see a problem immediately, but I believe the bond will not have full strength and will fail prematurely after some passage of time. From your description of the bonding adhesive used on your panels, it doesn't sound like polyester based adhesive was ever original to your car. I had never heard of a factory pink adhesive; maybe the color tint was intended SPECIFICALLY to alert shops making future repairs to the adhesive change. Your car must be a late 72.

As far as I know, Sermersheim panels aren't the ones that really must have the gelcoat. If Sermersheim isn't strongly recommending gelcoat for the repair, my advice would be to use the Fusor products as described above and skip the gelcoat. I really don't see where you have much choice if you can not apply polyester products over Fusor materials.

After the repairs are made, I would prep the repro panels for primer just like the rest the car. Gelcoat was not used when the cars were painted at the factory, but its use became commonplace to deal with oil/grease contamination, and lately, to counteract problems with some repro panels. If you have contamination you want to deal with, maybe you can apply the gelcoat selectively by panel stopping at a body gap or a sharp edge like the fender peak, or feathering the gelcoat on a contour where its harder to see the transition. Be advised; I'm just brainstorming here...I haven't used the stuff and don't know what's feasible.

Maybe others with actual experience using Sermersheim's panels can offer advice.

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Chuck,

Thanks for the advice. It's intereting about the pink glue not being the usual polyester adhesive color. I have a '75 parts car that I looked at, and it has the pinkish glue, too. So did a '76 I worked with. If I understand correctly, by '75 and '76 the cars were all SMC, so that is probably a hint mine is, too. The glass looks very similar to my glass-light grey.

The Sermersheim panels come already gel-coated on both sides.

So I can attach the new panels to the old SMC panels using the Fusor 127 product. Along the bonding seam where the new quarter (polyster 'glass) joins the SMC (I assume) top panel, I am still not quite sure how to handle the epoxy glue which will inevitably be present and which will blister any polyester material on top. I thought it best to lay in mat and resin, but the Fusor won't like any resin I use, and it seems a cheesy repair to just fill with more Fusor glue. Hmmmm.

Is it true that gel coat will not be compatible with SMC panels? I had myself convinced I wanted to gel all the original panels, but if they're SMC I'm not sure that's wise...

Thanks,
Patricia

[Chuck S.]

Re: '72: Fiberglass Type Identification

"I have a '75 parts car that I looked at, and it has the pinkish glue, too. So did a '76 I worked with. If I understand correctly, by '75 and '76 the cars were all SMC, so that is probably a hint mine is, too. The glass looks very similar to my glass-light grey."

Well, Gennite or SMC, they apparently used a different adhesive. Your thread has made me change my mind about using polyester adhesive on my doorskin.

"So I can attach the new panels to the old SMC panels using the Fusor 127 product. Along the bonding seam where the new quarter (polyster 'glass) joins the SMC (I assume) top panel, I am still not quite sure how to handle the epoxy glue which will inevitably be present and which will blister any polyester material on top."

DOHP, NOW I see what you're saying. If your panels are SMC, and I'm thinking there is a chance they could be, you WILL have to SKIP THE GELCOAT entirely. Eckler's product description is pretty clear...their polyester based gelcoat CAN NOT be used over SMC.

"I thought it best to lay in mat and resin, but the Fusor won't like any resin I use, and it seems a cheesy repair to just fill with more Fusor glue. Hmmmm.

Not exactly cheesy. I'm not sure anything has to be done for strength reasons, but V-grinding the seam at the butt joint and refilling with 100EZ will guarantee you a smooth joint surface. Originally the seams weren't "glassed"; the excess bonding adhesive that squeezed out of the joint was simply ground smooth, and any voids filled and smoothed. Glassing the seams has been done on repaints to fill "sunken" seams (glassing destroys the originality), and to restore strength to the joint without having to remove and rebond the panels.

The Fusor products I would use for the seam are different than the ones used for bonding the panels...100EZ is an adhesive used for repairing gouges (no mesh used) or cracks through (reinforcing mesh required). Check out the Fusor website and download the tutorial for 100EZ; it shows you how build up layers of alternating adhesive and mesh. If you V-grind the butt joint narrowly, say almost to the depth of the panel thickness and maybe 3/8" width to the side (total width 3/4"), you may be able to just skip the mesh, and finish the 100EZ to contour.

As with the gelcoat, I have not used the Fusor products before, but I do have a project planned using the 100EZ, and have spent time studying how to use it. The one caution in your case is that your working time with the Fusor materials is probably LESS than with conventional polyester products, and that rear fender seam is a LONG seam...I would probably not fool with the mesh; just V-grind the butt joint, fill with 100EZ, and finish to contour.

And, once more...SKIP THE GELCOAT. I don't know what paint system you're going to use, but I would prep sand the fiberglass body (including the gelcoated Sermershiem panels if used), and start with a good coat of high quality epoxy primer. After that, each restorer gets to choose their poison, but keep the paint manufacturer the same, and check the P-sheets to confirm the next planned coat is suitable as a top coat to the previous material.

[Wayne W.]

Re: '72: Fiberglass Type Identification

Funny thing is, the original bonding agent was polyester based as far as I can tell, and it was just marginal as a bonding agent. When a mid seventies car gets a hit in the front, the seams explode, and the body pops off of the cowl. Obviously the bond was not so great. You also see a lot of seam cracks and separations over time. And BTW it was pinkish in color on the mid seventies cars. There are some products, evercoat has one, that will do, but epoxies and urethanes are best for SMC. If you have a mix match of parts like you are going to have, you could use more than one product. You can bond the top panel to the bonding strips with epoxy, then hang the fenders. You can do that with either system. When finished, scrape or grind out the seam joints to remove the excess epoxy and fill the seam with a good quality polyester product. The polyester product, like evercoat sells, will be good enough for surface or non structural use.

[Patricia Brown]

Re: '72: Fiberglass Type Identification

Wayne,

Just to clarify, would the factory only use the pink-colored glue with SMC panels, or did they use pink with the standard 'glass, too? In other words, does the presence of pink glue necessarily indicate an SMC panel?

Would either of you guys mind if I snapped a picture of my fiberglass and email it to you and see if you can verify SMC or standard 'glass?

Patricia