1969 underbody fiberglass repair

[Kevin S.]

Another NCRS restoration opportunity for me.

I have a few places where I would like to do some fiberglass repairs on the underside of my '69. I have attempted, without much success, to do fiberglass color matching using white, black, and brown gel coat tints along with wax and hardeners. My results are hit and miss, mostly miss and very inconsistent. I've looked at a few boat repair videos and they make it look easy. I am not getting the same results. The original (gray) fibergalss color is very hard to match exactly and the gel coat surfaces are tacky after 24-48 hours. Obviously, I am not doing something right.

I am wondering if someone has found a product (besides fiberglass gel coat tints) or a paint that is close to a perfect color and sheen match to the original fiberglass under the car? Thank you in advance for your ideas and suggestions.

Kevin

[Mark E.]

Re: 1969 underbody fiberglass repair

I experimented with several spray paints while repairing the tunnel, battery box and tire carrier on a 1970. I'm not home now but can check later what I used. Purchased at a big box store, it's an interesting antiquing spray paint that blends well with the original finish.

[Kevin S.]

Re: 1969 underbody fiberglass repair

Hi Mark,
I've checked out some of the other related threads, good information.

I also stopped at Bradley Auto Supply store here in my area and talked with the guys for awhile. One of the guys is going to bring his equipment out to my house to color match the gray fberglass. They are thinking a 1-stage enamel with no clear coat mixed in the paint to get the right sheen, which to my eyes is a semi-flat gloss. They can mix the paint into a rattle can for me to test the color match. I'm thinking that I can use the rattle can and some acetone on a rag to spray and then wipe and thin the areas to blend in the repaired areas with the surrounding OEM gray fiberglass.

Gel coat tinting is certainly not working out for me. Paint seems like my best option, especially if I can get it on really thin so I can still see the fiberglass strands underneath and the color and sheen match.

Kevin

[Mark E.]

Re: 1969 underbody fiberglass repair

Sounds like a good plan; keep us posted with progress.

If the area is repaired, you may want a more opaque finish to hide the irregularities in grain.

Also, after all is repaired and paint matched, I found that a light coat of matt clear across the entire surface evens out the overall finish and leaves a clean, original look. This also helps to seal and makes cleaning easier.

[Joseph W.]

Re: 1969 underbody fiberglass repair

Following this thread….
I have repair work in that same area but mines much worse.
IMG_3015.jpg

[Patrick H.]

Re: 1969 underbody fiberglass repair

If the material is tacky at 24-48 hours that suggests to me you're not adding enough hardener, or getting the balance incorrect. Alternately, old or outdated materials may also cause this.

I assume you also looked at articles or videos on how to tint resin color for fiberglass?
If you do know anyone who does fiberglass boat repair they can probably help you. I have friends who have done a lot of fiberglass work as well as patients who make and repair boats, so the resources do exist.

[Kevin S.]

Re: 1969 underbody fiberglass repair

Good Morning Joseph,
Glad your tagging along with my battery compartment repair. I'm happy to share anything that I learn along the process. Yesterday, I spent time with acetone and blue shop towels removing my last gel coat tint attempt from the bottom of the battery box and the jack storage box, which was still tacky after 4-days of sitting.

I'm pretty comfortable now doing the fiberglass repair work. My battery box looks good where the repairs were done.

I've added some in-process photos so you can see where I am at. I need to get the repaired fiberglass color better (closer to OEM) and then rivet in the front and rear battery reinforcements.

Kevin

[Kevin S.]

Re: 1969 underbody fiberglass repair

Hello Patrick,
It's all operator error I'm sure. Since I am a perfectionist, I tend to keep dabbling with the resin color to get it "exactly perfectly matched", which means that I am constantly adding another percent or two or five of black, then more brown, then white, then more black, etc. Bottom line, I believe you are spot on. The color correction process is throwing off the percent of wax and the percent of hardener I need for the final "finished mix".

Test #9 formula: which was a failure and was still tacky after 48-hours
0.600 oz. (37%) fiberglass resin
0.810 oz. (51%) black gel coat tint
0.190 oz. (12%) brown gel coat tint - I have also used white gel coat tint too at this step
check color match and make color adjustments.....and this is where I am going wrong. I'm adding colors without adding hardener
then add 0.240 oz. (15%) wax and stir 2 minutes
then add 0.90 oz. (5%) blue paste hardener and stir 2 minutes - I have also used liquid MEKP hardener in this step too

Note: I did a bench test using 1%, 5%, 10%, 15% hardeners, both blue paste hardener and liquid MEKP hardener. The blue paste hardener kicked harder quicker and I settled on 5% blue paste hardener which gave me about 15 minutes of working time before it was too hard to work with.


You are right. If I am adding correction colors, then I need to add more hardener to the final blend too.

[Joseph W.]

Re: 1969 underbody fiberglass repair

Looks great Kevin!

[Kevin S.]

Re: 1969 underbody fiberglass repair

Group update,

All done with the battery box restoration. Friend of mine helped me by holding my bucking bar so that I could go under the car and set the rivets for the front and back battery reinforcements. I did have to cut the length of the rivets down about 1/8" since they came too long from Corvette Central.

Only thing today left to do is a light coat of acrylic matt clear lacquer on the bottom side of the battery box and the jack storage box.

Thanks for everyone's help.

Kevin