Sanding "Old Spot"

[Sandra H.]

Need some opinions.....am I on the right track here?
I've decided to go ahead with the stuff that doesn't involve a lot of cash outlay.....and cause it's killing me to not be doing anything with this car.

My Corvette has been sanded partially, but I'm assuming before I can repair the cracked fender and spray a gel coat that I should sand off the 'spots' down to bare fiberglass all around. It was originally Fawn Silver..no paint remaining, just undercoats.
Hand sand or machine sand?

All advice would be welcomed.....
Sandy

Corvette parts 004 copy.jpg

[Paul S.]

Re: Sanding "Old Spot"

Hand Sand With A Sanding Block, Or Air Sand With An Air File .do Not Use A Da Sander( This Will Create Dips And Ripples ). It Would Be Safer If You Just Hand Sand With A Sanding Block.

[Mike E.]

Re: Sanding "Old Spot"

Fawn beige or silver? There was no fawn silver in 61 or 62.

[Sandra H.]

Re: Sanding "Old Spot"

Mmmm....I knew that Mike, just had a brain fade for a moment.
Fawn Beige is my favorite color for a '62, but mine was silver.
Thanks for getting me back on the track.
Sandy

[Jim T.]

Re: Sanding "Old Spot"

I have only done my 68 and 70. After stripping the paint which only primer was left, I wet sanded the primer to obtain bare fiberglass.
Never used any power tools, just a sanding block.
If I used power tools I would of damaged the fiberglass for sure.
Are you going to repair the cracked fender? If there was a Corvette club in the area they could have a meeting and use your car as member hands on demostation and show other members on how to correctly repair a cracked fender?

[Sandra H.]

Re: Sanding "Old Spot"

Jim.....hand sanding sounds like the way to go. Why wet? Just regular sandpaper, but wetted down?

I'm concerned that it looks like late husband removed the paint and most of the primer coats (down to glass) with an electric sander. He was good with cars....guess I'll find out how good. Don't know if there are ripples or not....all edges seem to be intact and not rounded off.

I plan on doing the fender myself (and any other body work).....would be fine with sharing that experience with a club. However, nearest club that I know of is 200+ miles away.

The book that was kindly sent to me about fiberglass repair does have some info about sanding and filling in low spots.....doesn't look to be hard at all. (Unless ignorance truly is bliss.) What could possibly go wrong?

Sandy

[Bruce B.]

Re: Sanding "Old Spot"

I have stripped a 54, a 57 and 2 62 Corvettes and used a air powered orbital sander (DA) with 80 grit paper.
Just keep it moving and you will not damage the fiberglass in my opinion.
Then spray on a good heavy coat or multiple coats of high build primer then block sand wet with 200 or 320. Look for high and low spots and prime again and block sand until flat. The final block sanding should be done with 320 paper. After the final block sanding seal and paint.
I like the polyester high build primers since they are similar to the polyester resin used in the fiberglass body.
I have never used a gel coat and don't feel it is necessary on a cured out 40+ year old body.

[Bruce B.]

Re: Sanding "Old Spot"

Sandra;
If you want to get an idea of how flat the body panels are try the following. Get a can of black quick dry spray paint and dust a light coat of paint on an area. Then dry try block sanding the area wet with 320 paper. I like to block sand using a wooden paint stick wrapped with 1/2 sheet of 320 wet paper. Use a sponge and keep the area being sanded wet. After sanding look for high spots(areas where the black spray paint is sanded off) and low spots(where you see remaining black paint).
After the sanding if you dry with a rubber sqegee (spelling?) you can see the highs and lows easier.
After you finish block sanding the car a few times you won't have fingerprints for a few days.
Good Luck.

[Sandra H.]

Re: Sanding "Old Spot"

Bruce,
I had not heard of polyester resin before.....will this make "hairy" fiberglass lay back down?

Don't know yet if there is an orbital sander amongst the car stuff, but boxes of sanding disks would lead me to believe that I own one somewhere. (Chaos rules here.) If there's one here I'm betting it is electric.

As I plan on sanding down my old truck for painting too, maybe an air sander would be a good purchase since I have a big honkin air compressor.

(Fingerprints are overrated anyway.)

Sandy

[Paul J.]

Re: Sanding "Old Spot"

Sandy, Sandy, Sandy...polyester resin is what holds the glass fibers together. If your panels are getting "hairy", you've gone through the gel coat and into the panel and may need to apply resin or filler to true it up. The high build primer may be sufficient to do this, and I don't rely on it for large dips, but I'm no expert.

Regardless of how you strip it, you will still need to block it by hand. Think about the time and effort that you're putting into repainting it, as well as the cost. You want a good result. More aggressive stripping methods make more work for you when you block it, although experienced body men and painters can minimize any damage. Bruce has given you a tried and true method for blocking a body and checking it with a guide coat. Most body people follow this with some variations.

It's a big project, I admire you for tackling it.

Paul

[Steven B.]

Re: Sanding "Old Spot"

Jim.....hand sanding sounds like the way to go. Why wet? Just regular sandpaper, but wetted down?

Sandy, wet sanding does a few things, makes the paper last longer and provides a lubricated, smoother, more even finish compared to dry sanding. Keep the paper & surface of the body wet with a slowly running hose or continually dipping paper bucket of water. It is easier to control the outcome with wet sanding, in my opinion.

Good Luck and Have Fun!

Steve

[Paul J.]

Re: Sanding "Old Spot"

Steve's right. Plenty of water. It keeps the small particles from plugging the fine sandpaper grains and provides good lubrication.

[Sandra H.]

Re: Sanding "Old Spot"

OK, well, you're getting some idea of what I don't know about fiberglass....if polyester resin as in high build primer is what holds the fiberglass together, then what is gel? Is it also polyester resin? What's the difference between the two?

Sandy

[Peter J.]

Re: Sanding "Old Spot"

Sandy, I'm with Steven And Jim. Push her outside and wet sand. Really smooth and clean results.

[Bruce B.]

Re: Sanding "Old Spot"

Sandra,
Here is some basic info on gel coat;
A gelcoat is a material used to provide a high quality finish on the visible surface of a fibre-reinforced composite material. The most common gelcoats are based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to moulds in the liquid state. They are cured to form crosslinked polymers and are subsequently backed up with composite polymer matrices, often mixtures of polyester resin and fiberglass or epoxy resin with glass, kevlar and/or carbon fibres.

In addition gel coats can be sprayed or brushed on items such as a fiberglass Corvette body.

I believe Corvette switched to another type of body material chemistry at some time after 1967.

One more tip, you must use wet-dry paper when you wet sand. Otherwise you end up with 2 items, those being soggy paper and loose abrasive particles. Normally the adhesive used in standard dry sandpaper is water soluable.
Keep us informed of you new adventure.
And believe me, you will throughly appreciate the paint job if you do the prep work.