I need advice on how to fix this crack. My plan is to drill a small hole at the end of top of the crack, then screw a metal bar to hold it in place using the existing holes. Then patch the backside with fibergl*** matting, then when that is cured grind a small vee in the crack and patch the front side.
I've done cracks like that on my Corvette and no METAL is needed, just use the cloth and epoxy on both sides. Pat
I suggest making a wide(!) vee on one side, a bit deeper than half thickness and with a slope 12x the depth, i.e, for every 1mm depth you go 12mm out in every direction, making a 24mm wide ditch. The large surface area of the repair gives you a repair that sticks well, a narrow ditch makes a weak repair that can pop loose easily. You need a lot of area for the new material to adhere to the old - the strength is in the gl*** fibers, you have none going between the old and new, so it's basically a patch glued into place. Lots of area spreads load well. Fill in the ditch with fibergl*** and a suitable matrix (woven cloth plus epoxy resin will be strongest). If you need something to keep both edges of the crack level, apply it to the back. Doesn't matter what you use as long as it does the job, your metal plan would work but screwing may make holes you want to avoid as you'd have to fix them later. Once that side has cured, repeat the process on the other side. Ditch depth = as deep as you need to go to remove all the damaged material. /Ex fibergl*** boat builder.
I am currently building a gl*** bodied T Roadster and read quite a bit on fibergl*** "tricks". @G-son described the repair perfectly if you want the repair to last.
You don't need to make a hole at the end of the crack, as all the damaged material is removed before the repair is completed. Also, the fiber structure with fibers going in all directions is far less prone to letting cracks run than cracks in metal for example. If you want to make a hole anyway, or get gaps/holes for other reasons, you use the same 12:1 bevel around the hole.
I agree with not worrying about any hole or metal to hold it in place. I always try to do the majority of the repair on the backside where you can add some thickness and it not be seen. If you need to hold something together, I typically just use c-clamps and a piece of wood or something wrapped in wax paper so it will release from the resin when it sets up. Once you get it stabilized, you can cut the v in the outside tapering it back as much as you can as G-son mentions to have a good strong repair. I also agree with what G-son mentions about cloth versus mat since it is better for strength across the crack. Also need to v the backside to get a good repair across the crack as has been mentioned. Here is some information I put together a while back for tech week on putting a fibergl*** front end back together that was in several pieces. https://www.jalopyjournal.com/forum...w-to-put-humpty-dumpty-back-together.1228998/
I remember that thread when you wrote it, I think I have bookmarked it knowing I would need it later. Thanks
Its been a while since I posted this. Let’s just say life got in the way. Here is what I did to repair the fender. First I saw that the bonding strip had been broken off at the forward edge of the crack. I made a mold an made a new strip, then ground off the old one so the new one would cross the crack. I used a long strand fibergl*** to glue it in place and clamped till dry. Then I ground a V in the crack. The I cut several increasing larger strips of fibergl*** mat to fill the crack. Then a lot of sanding to finish I think it turned out well
Hello, The fibergl*** cloth when mixed together and laid out flat creates a good strong layer. But, your fender crack looks to be larger than most cracks and possibly needing more support. Your finish looks smooth on the outside. In our surfboard resin/fibergl*** cloth/mat cloth repairs, we noticed that if one layer was necessary to repair a large crack or indention from another fin cut, we needed to add two layers. But, if it was on the edge of the rails, sometimes it needed definite two layers to protect the large fin cut. In your Corvette fender, there is constant flex during all sorts of driving. So, one layer on top may be able to be finished smoothly for a good undercoat and final color spray. But, since the fibergl*** fender flexes, you might want to support the large crack underneath with a fibergl*** matting beyond the original crack and roll it under the fender opening edge. (Surfboard rails are the easiest to ding. So, when laying on the different fibergl*** coats, the rail is covered when the top layer goes on and later on, flipped over, the bottom layer overwraps the top rail coverage. Thus creating the strongest protection on the rail... as much as fibergl***/resin combo can give.) Jnaki When we were in a 60 Corvette with dual quads and 283 motor, it was pure sports car acceleration with some scary moments. First, the noise was tremendous and sitting in the low seats one could feel the car flexing as we took off down the avenue. Underneath the fenders were what I would call, “rough, but finished” surfaces. Without smoothing it down, one could feel the fibergl*** strands. But, it felt thick. A large crack like yours needs extra layers of support underneath for the full length of the crack and a curled lip of the fender opening. If that was your idea anyway, good on you. Cloth plus mat is desirable over just mat and resin for strength. YRMV
You also need to check and correct the body shimming to the frame if this crack was not from a accident. I had to do similar repairs on a 56 when they did not properly shim it putting it back on the frame.
The last picture showed the area where there was a gap repaired but the crack that ran across the entire fender is still visible in the the sanded upper fender. Corvettes are known to transmit the shock of a hit to multiple ares and cracks appear almost anywhere. The crack appears to be present since before the repair and even though it may not be detectable by touch on the surface, the visual indication of the crack is pretty clear. The process described for crack repair was spot on. For missing material you need mat and cloth to bond it properly. You need to dress the rest of the crack the way described across the entire fender top and bottom.
The area above the crack I fixed is an old repair and is holding up well, also the entire area under the fender is heavily reinforced with woven and mat. I have a lot of other small areas that need repair before primer. This ain't gonna be a show car I am eager to drive it again. Thanks to all that gave advice.
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