Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass?

[Ian G.]

I'm getting ready to start repairing the fiberglass on my 1959. I've bought all the materials and now wondering if I should fix some of the smaller surface cracks at edges and corners. I don't think these cracks go all the way through, but I worry they may cause separation in the paint eventually. See below. if you think they should be fixed, what's the best technique? Just sand down one layer of fiberglass and then apply a mat layer on top basically, then sand etc? See below.

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This one below where the chunk is missing from the fender is a problem, and I'm not sure how to progress. I've been trying to hunt down a fiberglass fragment to replace it with. if anyone has a fragment, or lead on a fragment I'd be very appreciative. I tried Joe Marquez but no luck. Otherwise, I guess I'll refill it with bondo, sand, take a mold of that, and then relay fiberglass after cutting it out.

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Thanks!

[Mark S.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

For what it is worth, I Veed out the small cracks; and filled with the correct fiberglass mat and resin. I put some wax paper over the area and then applied pressure over the filled area with a small roller to get the air bubbles out. You can then put some tape over the wax paper to hold it in place. There are several people that are more experienced than me; however, once you gain some confidence, you will feel more comfortable working on the larger damaged areas. I believe that taking care of those small cracks will give you peace of mind in the long run. Good luck; and you might enjoy this more and more.

[Rod K.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Definitely repair any cracks or de-laminations. For those cracks in your photos, the single line cracks be repaired using Evercoat 870 Vette Panel Adhesive as a filler (not regular body filler), also use it for minor spider web stress cracks. Vee out the cracks until the cracked 'glass is completely removed (usually 1/16-1/8 deep) then fill with the Panel Adh and sand flush. For more serious repairs such as areas where the surface is crunched the above advice about fiberglass and resin is good. Your damaged fender should be repairable by grinding out the damaged material and building it back up with 'glass and resin. If you break through, just back up the area from the inside with a piece of cardboard (not corrugated) with waxed paper against the original panel and build up the outside as needed. Always use fiberglass mat, not cloth, as the cloth weave will show thru the finished repair, even after paint, etc. If the backside is rough after you've finished the outside, just build up a "finish" inside layer and sand it accordingly. If you have any cracks or tears that go all the way thru, grind front and back to a shallow Vee on both sides of the crack and build up with increasingly wide strips of mat/resin. After a couple of successful repairs, you'll be looking for more places to fix. Good luck and enjoy.

[Ian G.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Thank you both for the advice. Rod, that fender chunk is actually an odd piece of fiberglass panel stuck in there and had bondo filled over it. It isn't actually the original piece "smashed in" sadly. I guess I can just repair as you suggest and just "V" out around the edges and lay fiberglass and build up to the original curve. On the back the same and try to get it close to the original curvature. I'm just a bit worried I'll have trouble getting it right...

[George C.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Ian,
All of the advice you have received is right on track, I have used these methods successfully. The only thing I do differently is use plastic sheeting instead of wax paper, as I had wax paper effecting one resin I used years ago.

I have the 63 Corvette Shop manual and it has a great section on fiberglass repair, good stuff for us beginners. Maybe the C1 manual has a similar section.
Enjoy your repairs,
George

[Ian G.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Would you guys fix these cracks on the rear underside seat nutplate mounting area? It won't get painted obviously, and the cracks don't seem to go all the way through to the other side of the floorboards. They just worry me a bit, given this is the rear mounting of the seat.

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[Richard M.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Ian, See this thread for some photos of repairs I made on a '59, particularly the left rear fender. Also a few below. Cleaned the fender backside, then laid in mat/resin to restore strength and form. Then made paper templates for filler mat on outside. It was much work but I was very pleased with results.

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For the rear flanges for the bumper brackets, as others mentioned, I used the "vee" out method and chopped mat and mat strips for the cracks and rebuild of the flanges, then VPA for strength and light filler to get proper final finish before surfacing primer. Also cracks near the hood gutter areas. Some pics of that in this thread and below... Rich

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[Ian G.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Master work Rich.

[Rod K.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Yes, I would repair those "minor" cracks as they are structural to some extent. If left alone they'll probably start to chip out eventually. Just grind out the cracks or whole areas and fill with Panel Adh (small cracks) or glass/resin (larger areas) as discussed above. Definitely repair any cracks that are in the outer face of the body as they'll show thru any other "fix" you try.

[Ian G.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Rich, How would you recommend I go about fixing this shattered cove? I've partially removed the old repair. It still has a big matt and resin behind all over holding it in place. I was thinking once I remove the jigsaw of pieces I would screw some thin boards to each of the outside and then repair. the inside of panels first. Seems thats the best bet to get the right contour. Is there a good alternative to drilling holes to limit the amount of finishing work? some kind of glue that is easy to separate afterwards?

The old repair was covered in gummy matting and bondo. See below:
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Over the fender, it's been cut out and filled with an original piece from another car, but not quite the right position/shape for where it should be based on measurements of the other fender. It should be over a few inches. I was thinking to recut it and then fill in on either side with backing paper as you showed. these are the worst spots on the car. Everything else is cracks, gouges or small pieces missing, so I count myself lucky.
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[Richard M.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Ian, This is what I would do...

Remove 100% of the old repair, including the old mat and material on both the backside and outside. You want to get to original clean fiberglass everywhere. Scuff a few inches around the entire opening on the backside to get a clean resin bond area for mat overlap.

For the contour in the cove, rather than using wood, maybe some sheet aluminum curved to shape and some long clamps or braces to hold it in place. Use a mold release wax agent or several layers of wax paper on the sheet so the resin won't adhere.

On the backside, place mat and resin and extend the mat beyond the opening into the clean areas surrounding the opening. A few layers should suffice. After it's cured and you remove the contour sheet, this will define the front area depth you need to build up. Create a template of the fill area and cut the mat to fit in the area to build up. Lay in the properly sized mat cut from the template to build up the outside area. You may need several layers there. Once you have good buildup you can then shape with a longboard sander. If you have to use some screws on some areas you can fill with some finely chopped mat/resin. This will reduced shrinkage.

I'd also suggest Vette Panel Adhesive for initial finish layering over the repaired mat/resin areas. In my photos it's the dark gray areas. Then a lighter product for the final finishing. VPA doesn't shrink and sands like cured resin. If you haven't used it before keep in mind it kicks off pretty quick so experiment with small portions at first. It's pricey, but the best product for these types of repairs in my experiences.

Remember to clean/sand any cured areas that were exposed to release agent or wax paper so the new layers of material adhere properly. For best practice it's a good idea to sand any cured areas before applying anything new over it as well.

Rich

[Rod K.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Just an additional thought as an alternate to the sheet aluminum Rich suggested. Haven't tried this but how about hardware cloth (I think it's called, heavy screen wire) to form the backup form for any large areas you need to rebuild. I think it would form more easily than sheet aluminum for areas where you have compound curves.

[Ian G.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

I do like the idea of the heavy screen vs the aluminum Rod. Sounds easier to get the shape. What thickness aluminum would I look for Rich, if I go that route? And it sounds like you are saying I should toss the "jigsaw" pieces and just fill in with all new fiberglass vs relay them as they were, grind down and fix the individual cracks both sides correct?

[Richard M.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

Yes Rod's idea using screen is a good method also. You could then use thin cardboard coated with wax paper over the screen when forming the curve and before setting in place.

The aluminum sheet I suggested would need to be pretty thin, just so you could bend to shape by hand.

Yes, remove all of the old jigsaw pieces and use new material for the repairs.

Rich

[Daniel S.]

Re: Is it recommended to fix smaller non-penetrating surface cracks in the fiberglass

HI Ian,

I am doing some research on body repair so I am going to attempt it myself probably when it gets cooler here in Northeast. I was wondering how you made out? Is this the first time you have attempted fiberglass repair?

Thanks

Dan