[Shiny]

I need to repair a structural crack in the nose (sorry if it's called something else) of my 70 LeMans.

Is glass/polyester the right material or is there a better system WRT bonding with the original part? .... epoxy resin for example.

How did Pontiac make this part and what materials were used?

Tnx,

Mike

[Shiny]

Anyone have experience repairing the fiberglass nose/header on a 70 Tempest/LeMans?

[1965gp]

I’m not a body man but I would think you could use regular resin and fiberglass cloth from behind to strengthen it. I’ve done that on shaker hood scoops with pretty good success in the past.

[4dblnkldude]

My buddy Mark just did this on his 70 LeMans and he used 3M SMC 8274 panel bond adhesive. You can't even tell there was damage now.

[HoovDaddy]

That part is made of SMC, not fiberglass. The repair procedure is the same, the chemicals are not. Standard polyester resin won’t adhere, you must use resin that is compatible with SMC. The label will state that. The primer you use must also be compatible with SMC, so check the tech sheet of your favorite primer beforehand.

[Shiny]

Originally Posted by 4dblnkldude

My buddy Mark just did this on his 70 LeMans and he used 3M SMC 8274 panel bond adhesive. You can't even tell there was damage now.

Thank you! I will hunt this down.

Originally Posted by HoovDaddy

That part is made of SMC, not fiberglass. The repair procedure is the same, the chemicals are not. Standard polyester resin won’t adhere, you must use resin that is compatible with SMC. The label will state that. The primer you use must also be compatible with SMC, so check the tech sheet of your favorite primer beforehand.

Thank you too! I'm glad I asked and appreciate everyone sharing their experience. I'm just curious if you know what type of resin was used?

It's obvious the part has a lot of long glass fibers and now that you educated me on the SMC process, it makes sense. Hopefully the 3M material or similar resin and woven glass cloth will get it done.

Mike

[HoovDaddy]

Post a pic of the damage, and I can elaborate on the repair.

[Shiny]

Here's the fracture. Fortunately, it's still held together enough to make alignment easier.

I thought I could fixture it, sand to expose material on both front and rear, then bond glass cloth over the break- heavy on the back, thinner on the front. There is enough "geometry" involved to make me think a glass cloth and resin would work better than solid strips but I'm speculating.

The 3M 8274 is very expensive ($110 !!) and needs a special gun to push both components through the mixer. Not very DIY friendly IMO... probably excellent material, though. Seems it is an adhesive for bonding panels and not a resin like I was thinking..

3M 8274 appears to be an epoxy but they also sell polyurethane-based SMC adhesives. The data sheet says a primer is not required.

It looks like Evercoat markets some SMC repair products. One of them, SMC Fiberglass Resin, is made to work with cloth and claims better adhesion to SMC than "typical" polyester resins. There may be similar epoxy resins if the Evercoat resin won't adhere, but why would I doubt them?

3M also warns against using common fillers: "DO NOT use a two part polyester body filler or putty over PN 08270. Bubbling
may result."

Evercoat says their fillers are OK, which is another "friendly" answer for me.

Mike

[4dblnkldude]

My friend did body work for 17 years, hes very patient and the damage was close to the same. He's got a spare nose I think.

[400 4spd.]

Do not use “woven cloth” (boat repair) mat for your repair. Use a random strand material, the type that you can shred with your hands, not cut with scissors.
Most polyester resins are SMC compatible, but confirm before buying.

[turbo69bird]

Idk the part you’re taking about specifically or it’s material. But many times I can repair items that are flexible with marine 4200 which has some flex . Harder pieces can be effectively willed with marine 5200 which hardens like a rock
Take a
Look at those tow products see you you think it will work .

For actual Fiverglass repair there are products like kitty hair which is a fiberglass filler in the consistency of bindo (except it’s water proof) with strands in it larger strands are called tiger hair. These work well, I’ve repaired boat jetski hulls with this product rather than standard cloth and resin.

[Shiny]

Originally Posted by 4dblnkldude

My friend did body work for 17 years, hes very patient and the damage was close to the same. He's got a spare nose I think.

I have no doubt the 3M adhesive would adhere, I just don't want to spend $200 for a one-time fix if I can avoid it. Do you know how he did this repair? Did he bond a thin solid sheet or did he use glass fiber or cloth?

Originally Posted by 400 4spd.

Do not use “woven cloth” (boat repair) mat for your repair. Use a random strand material, the type that you can shred with your hands, not cut with scissors.
Most polyester resins are SMC compatible, but confirm before buying.

Thank you. Please explain the tradeoffs. I can see random fiber matt or rovings matching the original material and making it easier to finish the visible front. But a woven cloth would be easier to get uniform thickness and I expect would be stronger, especially on the back side. Maybe cloth on the back and random on the visible face?

And the Evercoat polyester is marketed for this type of repair so I expect it to adhere...but I also hear the warning from HoovDaddy and note the 3M adhesive is an epoxy.

Originally Posted by turbo69bird

Idk the part you’re taking about specifically or it’s material. But many times I can repair items that are flexible with marine 4200 which has some flex . Harder pieces can be effectively willed with marine 5200 which hardens like a rock
Take a
Look at those tow products see you you think it will work .

For actual Fiverglass repair there are products like kitty hair which is a fiberglass filler in the consistency of bindo (except it’s water proof) with strands in it larger strands are called tiger hair. These work well, I’ve repaired boat jetski hulls with this product rather than standard cloth and resin.

Thank you, I'll look up these materials. They will probably be useful as fillers.

This is an example image of the part I pulled off the web:




The rib (red arrow) seems like a barrier to using a solid sheet to reinforce. I think it would limit the overlap to the blue area. A woven cloth would conform and let me go over the rib as outlined in green. This is why I like the idea of a cloth and resin better than an adhesive to bond a solid sheet.



Mike

[HoovDaddy]

The repair is too large for epoxy alone, you'll need to use fiberglass cloth the same as any SMC bodied Corvette repair. Use Acetone to clean the front and backside of the repair areas before you start. V out the main crack from the outside. Use 80 grit to sand the outside and inside surfaces. All paint must be removed around the areas. Then clean again. Purchase chopped strand fiberglass cloth, lightweight, not too thick, do not use woven cloth. Woven cloth will leave a pattern in the paint and it doesn't conform as easy in tight corners. On the outside apply 2 layers, first layer larger than the second. Two layers on the inside as well. Use Evercoat Vette Fill for SMC as your filler instead of bondo.

[Shiny]

Originally Posted by HoovDaddy

The repair is too large for epoxy alone, you'll need to use fiberglass cloth the same as any SMC bodied Corvette repair. Use Acetone to clean the front and backside of the repair areas before you start. V out the main crack from the outside. Use 80 grit to sand the outside and inside surfaces. All paint must be removed around the areas. Then clean again. Purchase chopped strand fiberglass cloth, lightweight, not too thick, do not use woven cloth. Woven cloth will leave a pattern in the paint and it doesn't conform as easy in tight corners. On the outside apply 2 layers, first layer larger than the second. Two layers on the inside as well. Use Evercoat Vette Fill for SMC as your filler instead of bondo.

Thank you! This is consistent with data sheets online and it makes sense. I'll chase down the matted/felted cloth.

Do you think the Evercoat SMC resin is a good option or should I look for an epoxy resin? The Evercoat is a polyester but they seem to have a "system" that includes the filler you mentioned.

Mike

[4dblnkldude]

[QUOTE=Shiny;6425242]I have no doubt the 3M adhesive would adhere, I just don't want to spend $200 for a one-time fix if I can avoid it. Do you know how he did this repair? Did he bond a thin solid sheet or did he use glass fiber or cloth?

He probably "borrowed" the material. I will ask him.

[Shiny]

Here's an SEM video showing how to use their product for a rigid plastic repair. It mimics the advice you all have been giving.

I now see how the thicker adhesive makes more sense than a thinner resin.

Link to SEM Repair Video on YouTube

I'll check out the SEM material and compare with other options. It appears to be an epoxy-based system, similar to the 3M that was recommended.

Thanks all,

Mike

[Shiny]

Any way to avoid buying a dual-component applicator gun? There are some decent-looking options on Amazon for ~$50 but if somebody has a clever option I could avoid collecting another single-use tool... I guess I could check the local parts stores for a "loan-a-tool".

I decided to order the SEM 40887. It is a glass-filled epoxy, half the price of the 3M, and their support tech said adhesion would be good. He also said it sanded well, would work as a filler, and I could use polyester glaze over it if needed.

I also considered Transtar 1478 and Plio-Grip/Valvoline 8004. I've had good experience with SEM products so stuck with them. The local auto body supply store had NOTHING in stock for SMC repair.

Mike

[HoovDaddy]

It will crack unless you back it up with fiberglass cloth.

[Shiny]

Understood, thank you! I will use as much glass mat as I can wherever I use this stuff. I don't have too many dings, just the fracture..

[Shiny]

I found a couple more surprises... 2 holes through the beak someone had "repaired" by filling with bondo.

I ended up using the SEM Dual-Mix Rigid Plastic Repair Material and glass mat as recommended.

I followed the SEM video and used a "pyramid" of glass layers on both sides.

The SEM epoxy was easy to use, wet the glass, and seems to have adhered well.