Thanks so much!

 

Priya who is going to paint the car and how much experience do they have. That will be a big point in choosing a color. I have been painting cars for a long time. I had a collision shop for some years. Now I paint my own cars in my garage. I stay away from fancy paints, I usually just do solid colors. Easy to repair if you burn thru sanding or buffing. And easier to do in a garage.

 

My husband has a friend who is a painter, I'm not sure how much experience he has but several years at least I believe given the age of my husband and his friends. He'll be doing it assuming he's still working as a painter when I get the car ready for paint. Other than that I contacted a local body shop that will paint it for an estimated $3500 paint included assuming I bring it to them in final primer and sanded to 320 grit.

 

just my opinion but , don't compromise on your color choice. if you want pink , paint it pink. you are building the car for you , not some unknown circumstance down the road. when it comes time to sell ( if ever ) people are going to nitpick everything anyway. when i built my 79 i made a compromise that i now deeply regret , so it will be sold as i get deeper in to its replacement. bottom line , build it like you want it and have no regrets in a few years...i speak from experience

 

Thanks dtamustang

 

After I joined the ACI 70-73 rear clip to the car I blended the join line on the upper deck and thought I was done:



I later ran my hands over the upper deck and it was apparent the upper deck on the ACI 70-73 rear clip rises up a bit from the low point of the ducktail at the tail light panel and I needed to shave it down all the way to that low point (blue line in picture). The red line is roughly where the 79 rear deck and the ACI 70-73 rear deck originally met when I joined the two together. The blue line is the lowest point on the ACI 70-73 rear clip's upper deck and the surface in front of the blue line originally rose up from there. I had to do a lot more shaving on the deck between the red line and blue line to get a smooth transition from the 79 rear deck to the duck tail on the ACI 70-73 rear clip. This is why I wanted the electronic thickness gauge to make sure this area isn't too thin after all the shaving down.





I put fiberglass wax and grease remover on the upper deck a number of times while I was sanding to make sure I had a nice shape (water didn't lay down flat enough to really show panel levels well) and I've got it where it needs to be now. I'm finally ready to use the electronic thickness gauge to make sure its neither too thin nor too thick where I joined the ACI rear clip to the car and reshaped the quarter panels. So, probably next week I'll be back underneath the car in the gas tank area doing the miserable work of thinning things out a bit again.

 

Why thin the underside? What harm can a few ounces or lbs of extra glass do? Or are you getting used to the feeling of glass fibers stuck in your face and miss it? I would think about maybe adding a layer or 2 where you are worried about thinness, but too thick?

 

Here's my thinking on that. As you drive the car you hit bumps and that creates a downward momentum on the body panels that causes a sort of impact on them. If you have extra thick parts of the panel with extra weight that creates a bigger impact and makes it more likely the panel will crack over time. Maybe as you say, its not enough to make a difference, but I prefer to keep the panel no thicker than necessary just to be on the safe side. Further, my husband tells me, and it sounds plausible to me, when you have a thick part of a panel next to a thin part the panels will flex with driving and that's where a crack is likely to occur because of the different amounts of flex between the thick and thin parts. So, for that reason as well, I want to keep all the panels close to the same amount of thickness.

 

I would be more concerned with what looks like fiberglass mat laid over that white gel coat or whatever it is and not bare fiberglass.

 

There is no fiberglass mat laid over the white gel coat.

 

why would you be concerned about mat laid over gel coat ?

 

Color: as a suggestion you can look at the Circus- Circus race boats - they were fuchsia in color - 7 different colors on the boat. Just one thought - if you go with a Metallic or candy - repairs and touch up are a real issue.

Gel coat is not structural. If just bonding over gel coat to build up - usually there is no issue as it can bond well. I would not bond to gel coat when there is a structural area as gel coat can shear / fracture. Most gel coats are just resin with a high concentration of color and fillers.

The project looks great and will look super in whatever color you choose..

 

I'll have a look.

Thanks!

 

Typical instructions for fiberglass surface preparation for repairs. I do follow these and have always had good adhesion.

SURFACE PREPARATION: Remove all paint, primer or gel coat by rough sanding (40-80 grit abrasive) down to the SMC or fiberglass. Sand past the damage, allowing a 2” margin around damaged area. Remove debris and clean surface with #1240 Wax, Grease & Silicone Remover.

http://uschem.com/products/docs/TDSU...ALL_RESIN1.pdf

 

So, I was keen to measure the thickness of my fiberglass joins with this ultrasonic thickness gauge:



To use the gauge it says to take a 1 inch thick example of the material you want to measure and use that to calibrate the gauge. I layered up a couple of thick pieces of fiberglass resin and mat and sanded them down to exactly one inch. I spent about 15-20 hours doing that and trying to get the thickness gauge to work. The instructions were written in China and some of them were confusing or incomplete so it was quite a chore to figure out how everything works. After trying all settings and combinations it measured my 1 inch thick fiberglass sample anywhere between .2 inches at times and .5 inches - it never gave a consistent measurement. I sanded my samples down to 1/4 inch and 1/2 inch thick to see if that would make a difference and still couldn't get a consistent reading.

I tried the gauge on the car and the readings varied a great deal on my laminations and on the hand laid fiberglass of the 70-73 ACI rear clip. On the SMC body panels it was reasonably consistent. For example out of perhaps 10 measurements in the same place on the SMC it would give around eight readings of .09 inches to .11 inches and one reading of .06 inches and one reading of .14 inches. So the Ultrasonic thickness gauge would be of some use on SMC body panels but is of no use on fiberglass. I think it probably wouldn't work on factory press molded fiberglass either.

I figure I put about $50 worth of material into my 1" fiberglass samples for calibrating the gauge and the gauge was around $200, so that's around $250 down the drain. I really wanted it to work but it just didn't no matter how hard I tried to make it.

So, I guess I'm done sanding the inside of the joints between the 79's body and the 70-73 ACI rear clip.

Next thing to do is to glue in the rear wheel well splash panels and this piece of the upper deck reinforcement I removed in the beginning. I'll have to laminate that back together as well once its glued into place and then its back on re-working the remainder of the bumper brackets to get them to fit.



The piece above joins to the 79's upper deck reinforcement in the picture below where the arrows are:

 

Not sure if this may help but I have watched guys do thickness testing on steel tank walls etc with small hand held units and they get a dob of grease and push the sender(transducer?) end into that .

I realise its the last thing you want to do on a glass panel

 

Priya,
For what it is worth. Your concerns on how thick or how much weight your panels have and your fear of cracking in the future can all be eliminated IF the rear body panel ( lower taillight panel area) is correctly bolted to the rear crossmember/impact bar via the bumper brackets you made that will make it so the bumpers are being supported and not just being bolted to fiberglas and hanging there. This is why I commented on that in the manner I did when you were at that point of your conversion . Simply bolting your bumpers to the fiberglass is one thing and may look good...but how GM did it..there is a reason for it as you are now seeing due to your concern.

With your clip in the rear being bolted to the rear crossmember like GM did...there is no way for it to be able to flex and due to the shape of the panel with the curves in it...that gives the panel a lot of strength...so...if the rear taillight area is able to be secured to the rear crossmemberb or rear impact bar....I would not think twice about it.

DUB

 

 

Yes, I will have all the factory chrome bumper bumper brackets bolted to the bumpers, the rear crossmember, and the rear frame rails as the factory did it. In addition I'll have the brackets that go from the quarter panel bumper bolts to the rear frame rails as was done on the '73.

 

Please stop worrying about too thick. With glass, whenever in doubt, add another layer.