Some things you just have to do right.

I've spent most of my posts explaining how to do things.  I'm going to take a minute now to explain a why.  Since I started fixing the Viper's body, one of the big things I've been harping on is the need to do things right to prevent future cracking.  I've also mentioned repeatedly how the previous "repairs" on the car weren't done properly.  You'll notice that I always put repairs in quotes.  With cracked fiberglass, you CAN'T just band-aid it, it must be done properly or it WILL crack again.  As with many other things on this project, the hood has again provided me a perfect example to demonstrate why.

 

Lets take a closer look at this crack here.  As I mentioned a few posts back, this crack appeared after the car had been "repaired."  That much is obvious because it's cracked through the primer that covers the "repair."  The question is why did this "repaired" crack come back?

Without the paint covering it up, the reason was very apparent on the bottom of the hood.  Here's where the crack is on the bottom side of the hood.  The white is the original panel.  All the 'glass on the bottom is stuff I added during my repairs(and before I repaired the front lip).  The stuff in the middle is just kitty hair(fiberglass reinforced filler) from the previous "repair."  You can see that not only is the crack still very much there, there are voids in the kitty hair and much of it isn't actually bonded to anything.  The crack is basically just bondo'd over.  While it might have looked smooth from the outside the structure is cracked and has no strength.

Grinding into the back side of the crack further shows how poorly this crack was "repaired."  Not only was the crack only glossed over on the top side, just below the surface on the back side there is no more filler.  There is just a large void under the crack.  So, we're left with a still cracked panel that has no reinforcement behind it. 

It's no wonder that this crack reappeared.  There's almost nothing holding the shattered fiberglass together.  The top side just has a skim coat of filler covering the crack.  The back side has a little filler just kind of holding the pieces together.  This, right here, is why so many repaired fiberglass panels crack again.  Covering up a crack doesn't address the problem, it just makes it look nice temporarily.  You can't actually repair a crack in fiberglass, you must completely remove the crack and replace it with new fiberglass.  If you just cover a crack with bondo or even a layer of fiberglass, it's not a matter of if the crack will reappear, but when.