360 Repairing crack in undertray

Picked up a used front undertray to replace the one missing from my car.
It has a crack on the leading edge. I don't think it'll be a problem once I put everything together, but I wanted to at least make an attempt to fix before installing.
It seems to be a fiberglass type material.
Has anyone made an attempt to repair these? Surely I'm not the first lol

Secondly, I can't seem to find a clear indication of the hardware needed to attach this thing to the car.
The diagrams look clear enough but the recommended count of each screw doesn't seem to match up.
Does anyone happen to have information on what all I will need?

Thanks, and advance!

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You can use JB Weld, dries much stronger than the undertray material. Use Gorilla "permanent" tape, not regular gorilla tape. It doesn't stick to jb weld, so you can fill the crack, lay down the tape to smooth it, then peel the tape off when dry. Totally solid repair

I did something more extensive here:

https://www.ferrarichat.com/forum/posts/147957964/

 

That all sounds easy enough. Thank you!

 

On a related note, had my undertray off yesterday and the JBWeld is still as solid as the day I did the repair a couple years ago

I think you'll be pleasantly surprised with the result.

You have to pull give the permanent gorilla tape a good pull, but it will come off, pull laterally, not vertically

I also used it to repair my front tray and front bumper tabs

 

Any reason you didn't sand, fill, and smooth it then refinish it? The permanent gorilla tape idea is great for creating a "form" for the epoxy.

 

Initial sanding, certainly a good suggestion, the JB Weld took to it fine to the bumper, I did sand the smooth plastic surfaces.

Finishing it off with some smoothing and paint - I intend to go back in and improve the presentation. Honestly I wanted to see how well it would hold first, I wanted to get the car re-assembled, and it was too cold out to spray paint.

I was gonna post about it after I did the cleanup in the Spring, but this post came up, so wanted to help out a fellow FCHATer

The Permanent gorilla tape was a happy accident, I was using it to hold a couple things together and when it peeled clean, got the idea to use it to form. Creates a lot of possibilities for nice looking plastic repair.

I also used it to repair the unbelievably flimsy fender liner holes which basically just deteriorate, now the liners are very solid at the attach points.

Not sure why the lower liners are so well constructed, but the larger component is a thin shell.

 

Can you post a link for the “permanent Gorilla Tape” please. Also, are you using it to make the missing tabs or just to repair holes?


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The Gorilla Tape idea is a good one. I had a hard time making the repair look reasonable from the top (engine) side when I used fiberglass on a large area. I would not use fiberglass again as it was way messy, took a long time to dry and difficult to sand. The JB and Gorilla is a better solution.

I used JB on the smaller cracks in mine and it was a solid choice. I also used it to fill some deepish scratches in my under tray then sanded smooth. The sanding of course lightened to color of the material (some sort of plastic, not fiberglass) and I made the decision to coat the entire piece.

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Though it may not last (!), I stripped and prepped the piece with lacquer thinner and alcohol and sprayed SEM Trim Paint (actually far more like a dye than paint) and it blended ridiculously well.
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Which JB Weld are you guys using? The black plastic bonder one?

 

Sure thing. I got it at Home Depot, I think this is it. Looks like it's all weather tape. I just saw the word permanent and that stuck in my mind.

https://www.gorillatough.com/product/gorilla-weather-tape/

Regular gorilla tape has a heavy fibrous base, the permanent version does not have the fibrous base, its like an all plastic tape. Regular may also work, I didn't try it. The permanent version worked so well, I just used that.

I used this JB Weld @GogglesPisano

Pictured left to right, reg gorilla tape (which I have not tried), permanent gorilla tape, JB Weld

 

**edit: Never mind. I just saw the post above?. I can't find Gorilla Tape called "permanent". Do you happen to have a label avail?

Not that I mind the tape being stuck to the inside, if it had to. I assume I can do all the work on the inside of the part, yes?

 

Not sure I'm following what you mean

 

Little bit more on the bumper tabs, once they were filled and solidified (they felt quite solid) I drilled holes, inserted threaded rivets, and now, the entire bumper assembly feels fantastically solid, before it was held on with one solid tab, the rest cracked or deteriorating at the ends.

I even added a couple layers to my armor scrape guard which was wearing thin. Those wings are like $250 a piece.

I was also able to create threaded inserts for my splitter which got replaced with regular rivets at some point. CF splitter due soon from Poland which I'll be able to easily install from underneath now.
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And in case I wasn't totally explicit, wait until the JBWeld is completely solid before pulling the tape, think I gave it 12 hours

 

I can JB Weld the crack from the inside, place the tape, etc without having to do any on the outside of the undertray. Or, do I need to do it on both sides? Not that anyone will ever see it either way. Just wondering how much reinforcement it needs.

 

I think you do exactly as you describe, yes.

Without seeing the crack, I think you can do this, yes, just make sure you work it into the gaps. I'd put a piece of tape on the outside so if there is any opening, it'll keep it from oozing onto the outside surface.

Worse case, if it isn't completely solid, you can just mix up some more and make another pass, this stuff is very easy to work with and gives you a lot of room to get it just the way you want. If you go multiple passes, def sand between for best adhesion