Body work on fiberglass parts

Though I don't like "Bondo" brand products these days, they do still make one I do like, fiberglass "gel". Instead of the old runny maple syrup fiberglass, this stuff looks and acts more like body filler. Thus you can easily lay it on to fill like you want. A tad bit of fiber might be good to add, but if it's only 1/4" I think you'll be fine without it and added fiber wil tend to complicate achieving a smooth finish later. Your main concern is that your filler bonds adequately to the part. To make sure you'll want to scratch the bejeezus out of it with around 80 grit sandpaper. Just the area you are working on, feathering towards the edges so you don't have a lot of scratches to fill later.
Spread this stuff on like body filler and let it set. Work it down. Repeat as necessary until you're satisfied. Don't even try to get a really smooth finish, it won't happen. Use a body filler "skim coat". Evercoat makes a fine one. I can't remember the exact name but it comes in a plastic squeeze dispenser. Mixes like bondo but is the consistency of hand lotion almost. Perfect for smoothing out fiberglass.
Evercoat more than likely makes a similar product to Bondo's "gel" but I haven't personally tried it. I'm no bodyman but the Evercoat stuff really impresses me compared to the old Bondo crap I've been using for years. What I've laid out above is how I "molded in" my CS side scoops. Dunno where I bought them now, but they fit absolutely horribly. Fitting them up top and front(more or less) left a gap at the bottom that I could slide all four fingers into. Filling and molding with fiberglass gel (and some mat) made them look sharp for the last three years. I know that 'glassing to metal (not what you are doing) ends up cracking sooner or later. When that happens I expect I'll grind them all off and try buying some that fit better. The best solution would have been to build up the scoops' deficiencies the way you are going to and kept them as "bolt ons". Then no cracking. Many people have done this very successfully. Due to bad fit, most have had no choice.

I am looking at a can of Bondo-Glass- short strand fiberglass filler sitting on my kitchen table as we speak. AKA kitty hair. It works great; just make sure you grate it down prior to hardening (mils above the final finish point) It dries hard as hell and takes a bit of elbow grease to sand it down after it dries. You can pick it up at Wal-Mart or Pep-Boys.

I have not done any of my fiberglass work yet, but when I talked to the guy who has done some of my major body repairs, the way he explained it to me was...
Bondo is 1960s technology, it has not changed since. Evercoat is 21st century technology, easier to mix, easier to spread, easier to sand.
I know I am going with Evercoat. The body putties that I have used convinced me.

Bondo glass is a "new" product. The Evercoat products are great though. My dad uses it for small repairs to his boat. I talked to a guy at a local Plastics/Fiberglass company and he told me that Bondo and Evercoat products are garbage. Opinions, opinions... I suppose that I should by his $70 a gallon resin. I use the Evercoat resin for my fiberglass layup and the Bondo to fill lows and to shape areas. My dad has done the same for quite a while and I have never seen any patch or panel come apart on his boat; and it is exposed to the elements 365 days a year.

I'm no chemist, so I'll leave the Bondo discussion alone, but you're right, you don't want to use filler to cover a 1/4" gap. My Shelby endcaps didn't fit, either but here's my fix. On the edges, I cut several 3/8" wide strips of 'glass mat and 'glassed them to the edges with resin. I found it best to work slowly, doing no moe than three layers at a time, then sanding them smooth and checking the fit to the body. After I got the fit right, I added a couple layers inside the cap to tie all the thin layers together. On the larger flat sides, I used more mat and resin to build up the contour to get them close to the quarter panel shape, then used a thin (less than 1/16") layer of filler, then epoxy primer. Make sure you scuff the gelcoat with 80 grit before adding any 'glass to existing parts and you'l be fine. Fiberglass is very forgiving and very easy to work with, just work slowly and measure your resin and catalyst carefully as per the intructions and you'll be an expert in no time.

Something else I found that helped with the endcap fitment...use a drill to widen the three mounting holes by about a 1/16th inch, that will give you a little more adjustment. I did that and was able to move most of the imperfections down inside the bumper area so that the bumper covers it.

67GTA-FB429 said:

Something else I found that helped with the endcap fitment...use a drill to widen the three mounting holes by about a 1/16th inch, that will give you a little more adjustment. I did that and was able to move most of the imperfections down inside the bumper area so that the bumper covers it.

Click to expand...

Thats what I had to do and I had to trim the endcaps a wee bit...and TONS of sanding.

To the original poster...I am having a hard time picturing where your gap is...could you post a pic? Where did you get your trunklid from?

Keep in mind we're talking about fiberglass here. You can fill as big a gap as you like. Or build an entire Corvette fender. Or in fact an entire speedboat out of it. It's important to differentiate it from polyester "fillers" whose sole purpose is to make a surface smoother and more attractive. You couldn't build a fender out of body filler. Then of course there are "crossover" products which claim to be the some of both, just to confuse things. Sigh.
The exact fiberglass gel I've personally had good luck with, and have no doubt I could construct things with, happens to be a "Bondo" brand. The body fillers I've been using lately happen to be "Evercoat" brands. Specifically Evercoat "metal 2 metal" and the final finish stuff called "glaze coat". Evercoat was recommended to me by no less than 3 pro body men. They seem to favor the Evercoat fillers "rage" and "gold". I've yet to try them as I haven't been doing body work lately. The last time I bought a can of old school Bondo body filler it was the consistency of cookie dough and pretty much useless.
Evercoat has a big product line, including the "fiberglass resin jelly" I like so much. Lookhttp://www.evercoat.com/productSection.aspx . the jelly stuff is under "resins and accessories".
I've tried kitty-hair type stuff. Sure it's strong, but how ADDITIONALLY strong do you need an end cap to be? And it's hell to sand to anything like a smooth finish, the stupid "hairs" keep sticking out. I found it to be much more useful in reinforcing the backside of something where finish doesn't matter.

do you have pics of this yet I am very interested on how it came out... thanks

Would like to see the finished product too...also would be cool to see the "before" pics, if you have them.

thx