Will fiberglass ever stop "wiggling"?

[Rick Parker]

I have an NAF that was created in about '85. It's hand laid and is relatively thick. The only area that I have experienced any of the described irregularities is on the tops of the front fenders near the foot boxes. This is directly over the exhaust headers as they snake off of the heads. I attribute the irregularities to the additional heat. I used a heat barrier material but it didn't eliminate the described issues. I might add that it becomes less noticable once its cooled down after driving.

[sea2jet]

I owned CSX4236 and I started to get the same print through and washboard effect on the tops of the fenders. I've owned 3 ERA's, a 1991 Cobra ERA297, an ERA GT40 made in 2002 and another Cobra, ERA708 manufactured in 2005 None of these have that issue. Has it gotten worse? I thought my Shelby was an exception until I ran across this post.

[Maricopa]

After 20+years & 8,000+ vintage race & street miles

8K in 20 years? No wonder it looks good, it never sees the outdoors!

Mine had 8K on it it's first year and regularly sits in the AZ sun. After 8 years it's still pretty smooth but a few problem areas can be noticed, mostly in the POS Tristates hood.

[strictlypersonl]

There's a reason that ERAs usually hold up better than most. Instead of standard resin, we use tooling resin for the main body. It's designed to hold up during many heat cycles, and it has less volatile styrene in the mix. Much more expensive, and harder to lay up, but that's the way we do things.

[Bernica]

I watched a friend of mine in the high-end auto painting business paint an old Corvette. He primed it with something he said was new. A carbon fiber based primer of some sort. He said that once that primer was on, nothing was going to come through, check or crack. I will ask him what it was.

[RedEye]

Mine looks great in the hot sun... noticeable waves on a cold day.

[Tim7139]

Well I must say, I looked a a few SPF examples, mostly older, mostly darker, before I plunked down any cash and I saw nothing in that regard with those cars.
The body and paint prep work, I was very impressed with.
Mine was made seven years ago, and while, light colored, I've seen nothing but straight panels and paint that looks pros teen. I did a light polish recently with pretty close examination.

[Kobura]

This is an interesting thread. My Backdraft is Indigo Blue and after a while I noticed that there is a lot of "Wavy Navy" in the doors and side panels. I didn't notice the waves until a few months after getting the car, so I assume they weren't there at the factory, but I am not sure. I have decided to live with them as I don't see the point of making a fake Cobra into a show car. Actually, the way it is lets me enjoy driving the car without worrying about getting the paint chipped up. Life is good!

[cycleguy55]

Think of it this way - the waves are like dimples on a golf ball, they reduce wind resistance.

[DanEC]

Originally Posted by Bernica

I watched a friend of mine in the high-end auto painting business paint an old Corvette. He primed it with something he said was new. A carbon fiber based primer of some sort. He said that once that primer was on, nothing was going to come through, check or crack. I will ask him what it was.

I would be curious to hear what it is also. It's been a regular practice for decades to spray gelcoat early Corvettes stripped to bare fiberglass (they received no gelcoat by GM) during re-paints. I sprayed my own and it's some tough stuff and a mess to work with - but as long as put on to a specified thickness, it will seal down fiberglass and repairs like almost nothing else. Some painters have converted to epoxy primer on bare fiberglass but on a rough body I think many of the pros still like glecoat. I haven't read about anything like a carbor fiber based primer over on the Corvette Forum yet.

[Bernica]

I know he said it was a ground up carbon mix with either epoxy or gelcoat. I know he said it cost $$$ and he was all excited about it, but said it was a b_tch to put on and he only got one shot. He is a typical crazy painter and loves new stuff. I will find out this weekend.

[mikeinatlanta]

This thread if full of misinformation.

1. Whether the body is hand laid glass cloth, matt, or chop gun has zero to do with this issue. Kevlar or carbon in the laminate is also irrelevant.

2. The idea that any primer has sufficient rigidity to be structurally significant in a composite laminate is ridiculous. If the composite wants to move, the primer is either moving with it or coming off. EDIT: Print through is not the same as post cure creep.

3. This issue is directly related to the quality of the resin, and the quality control in mixing the resin. If your body isn't stable after a year, you can pretty much bet on it never being stable. Without knowing the specific resin they used, there is no way to determine if your issue is a material defect, or just cheap materials that shouldn't have been used in the first place.

4. Generally speaking (very general) the resin food chain (bottom to top) is cheap polyester @ $25 per gal, better polyester @ $30 per gal, good polyester (like tooling resin) @ $39 per gal, cheap epoxies @ $75 per gal, vinylester (can you say factory five?) @ $45 per gal, quality epoxies @ $100-$800 per gal. The problem with cheap epoxies is excessive flex and post cure creep.

[DanEC]

Originally Posted by mikeinatlanta

This thread if full of misinformation.

2. The idea that any primer has sufficient rigidity to be structurally significant in a composite laminate is ridiculous. .

I don't believe anyone actually made this leap of faith - although the thread subject did get slightly hi-jacked by an extraneous comment about a supposedly new primer material. Having made major repairs, gelcoated and painted a 66 Corvette I couldn't help but follow up on it.

[Bernica]

My apologies for any "hijacking". Not my intent.

[Tim7139]

This issue is directly related to the quality of the resin, and the quality control in mixing the resin. If your body isn't stable after a year, you can pretty much bet on it never being stable. Without knowing the specific resin they used, there is no way to determine if your issue is a material defect, or just cheap materials that shouldn't have been used in the first place.


Is the inverse also true? If you have no issues over that year, are you likely to not develop any subject to proper finish and regular care?

[mikeinatlanta]

Originally Posted by Tim7139

This issue is directly related to the quality of the resin, and the quality control in mixing the resin. If your body isn't stable after a year, you can pretty much bet on it never being stable. Without knowing the specific resin they used, there is no way to determine if your issue is a material defect, or just cheap materials that shouldn't have been used in the first place.


Is the inverse also true? If you have no issues over that year, are you likely to not develop any subject to proper finish and regular care?

That is a tough one to answer other than "it depends". For example, I work with and epoxy resin Hysol EA9390 ($375 per quart). Its tg is 350 Fahrenheit and requires a 200 degree cook to properly cure, however, it will harden at lower temperatures to include room temperature. The thing is, the only area where is will have problems if cured cool is that it can't take high temps. If cured at room temp it can sit for two years and as soon as you put it in the hot sun it goes back liquid.

Basic story is that as long as your body isn't exposed to temperature extremes beyond what it has already seen, you should be ok, but when it sees a higher temp than before, that's when you may have an issue. The best thing you can do with a fiberglass body is to take it to someone with a big oven like a powder coater and have the body cooked at 150 for a good four hours. EDIT: That would be BEFORE paint, not after.

All of this assumes that the body is made of a sufficient quality material to begin with. If it's made of a low quality resin that can't take normal underhood temps you are screwed no matter what you do. It doesn't require the best resin, just not the cheap junk resin.

[krausewich]

Obsessive... Another cause of the wavy navy, can be the result of brush applied gelcoat. I don't know that this is your case on a 4000 body, but too often lazy laminators will brush apply the gelcoat prior to the reinforcement layers. This will result in starts n stops, streaks, thick an thin spots. If you hold the part up to the light you will see what I mean. I've attached a photo I just took of a hood scoop I have here that came from a reputable accessories supplier several years back. You will also notice a few bright speckles from air bubbles. Compound this with the glass reinforcement not able to lay flush with the surface causing a 'wavy' layup and resin pockets... long story short, resin shrinks as the styrene evacuates; thicker unsupported resin will move more than the thinner and squibbly spooge you will have! Brush application.. tolerable for small interior stuff like foot boxes, air scoops trunk trays, etc... but on quality finish surfaces, spray application is the only way to go. Not a solution to your current issue, but I do hope it helps with the understanding for future investments.

Bernica, may I hijack the lovely lady in your avatar?? I promise to have her home by 10

https://www.dropbox.com/s/nkxq67k5b6..._5103.JPG?dl=0

Mike.

[Obsessive]

Originally Posted by cycleguy55

Think of it this way - the waves are like dimples on a golf ball, they reduce wind resistance.

I always thought the golf ball dimples were there to help you focus on a single point to keep your eyes glued to the ball during your swing. The trouble is, the waves in my terribly expensive cobra have the same effect!

It's been a while since I posted/reviewed this thread and I appreciate all the feedback. The wiggles have not gotten any worse and I've made the conscious decision to just enjoy the car the way it is. After all, it sounds like the general consensus is that I am stuck with it. The body was constructed of hand laid fiberglass but I have no idea what the Las Vegas prisoners (many on this forum may remember the Shelby American history with this) were using for resin.

[mikeinatlanta]

Originally Posted by Obsessive

I always thought the golf ball dimples were there to help you focus on a single point to keep your eyes glued to the ball during your swing. The trouble is, the waves in my terribly expensive cobra have the same effect!

It's been a while since I posted/reviewed this thread and I appreciate all the feedback. The wiggles have not gotten any worse and I've made the conscious decision to just enjoy the car the way it is. After all, it sounds like the general consensus is that I am stuck with it. The body was constructed of hand laid fiberglass but I have no idea what the Las Vegas prisoners (many on this forum may remember the Shelby American history with this) were using for resin.

Go look at an unrestored Ferrari F40. It may make you feel better about your paint.

[DanEC]

Originally Posted by Bernica

My apologies for any "hijacking". Not my intent.

It's a 2-1/2 year old thread - what's not to hijack. I would be interested in what your painter tells you about that primer.