Build Log: April 8, 2013

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Well, for the last couple of months, things have been pretty slow regarding the build. All of a sudden, though, things are moving fast. I have some time off from work, the weather is suddenly spring-like, and I am on a mission to get paint on the car. So, the first thing I did was to finish the underside of the hood. It got coated with Duplicolor bedliner material. This will help to protect the underside as well as the finished side from spider cracks from errant stones and such. It also helps to mask the rough fiberglass finish of the underside.

While I had the hood sitting upside down in my table saw, I noticed how wavy the chin of the car was. I had never noticed this while doing the body work, since it is hard to see when the hood is upright. It is probably something that nobody would ever notice, but now that I know itís there, I needed to do something about it. So, more body work. Fortunately, this was just a quick touch-up:

Now it was time to get ready for paint. I needed to start with the body buck. In its current configuration, it holds the front and rear sections nicely together. But when I paint them, I need them to be apart. Additionally, I have a relatively small (30 gallon) compressor, and if the body sections can be painted separately, that will give the compressor time to catch up. So, I needed another body buck. I cannibalized the chassis dolly and repurposed it:

It holds the front section nicely.

The rear section almost looks lonely...

Next, it was time to start building the paint booth. Hereís the kit:

OK, itís not actually a kit. Itís just a bunch of pipe and fittings I got from Home Depot. But it will become a paint booth shortly.

 

First, the booth is framed. I used special paint booth tape as bracing. I hear itís good for ducts too.

Next, I needed to provide for some ventilation. I really wrung my hands over this. I definitely want the best ventilation I can manage, but at the same time, I didnít want to spring for a very expensive explosion-proof fan. I know several guys who swear that all I need is a couple of box fans pulling the fumes and overspray out, but those fumes and overspray are flammable. I havenít actually done the math, but I feel sure that the fans would be pulling a flammable mixture over the motors. So, I decided to use a fan in ďpusherĒ mode. In other words, the fan blows into the booth, rather than sucking air out. This way, only clean, non-flammable air is being pulled over the fan motor. The fan will be mounted at the near end of the booth near the top, and I will open the garage door at the other end to let the air out. A friend of mine lent me a 1500 CFM ventilation fan that will work nicely. I built a simple frame to hold it:

Since it is a little top-heavy, it gets clamped in place to the table saw:

I calculate the my simple booth is about 900 cubic feet. The fan moves a nominal 1500 CFM, so that gives me a little over 1-1/2 air changes per minute in the booth. Thatís not great, but it will do. A furnace filter gets taped to the outlet of the fan to keep the incoming air clean.

I found these nifty self-adhesive zippers at Home Depot. They will make moving things in and out of the booth much easier:

It will be tight, but workable:

I can paint the trunk deck and scoop horizontally on a rack, but the doors should be painted while upright. While I suppose it is more important to paint the panels in their final orientation with metallic paint, but I donít want to take any chances. So I made a simple rack for the doors:

OK. It looks like Iím ready to start. The paint regiment will be this:

1) 2 to 3 coats of Evercoat Slick Sand high-build primer

2) Block sanding

3) 1 -2 coats of PPG DP Epoxy primer/sealer

4) 2 - 3 coats of PPG Concept color

5) 3 - 4 coats of PPG Concept clear

6) Cut and buff

The Slick sand comes first. This is basically sprayable filler. It goes on thick and sands easily. It is intended to be the coat that is block sanded for the final straightening. I struggled a bit with getting it to spray properly. This stuff is thick. The tech sheet says to use a 2.0 to 2.2mm fluid tip. My good DeVilbiss gun only goes up to 1.8, and everything I have read indicates thatís not big enough. I have an old HVLP gun I got from, you guessed it, Home Depot years ago, and I wondered if I could modify it to work. I took it apart and concluded that I could probably bore the tip out to 2.0mm and it would still work - maybe. The gun was only $60 new several years ago, so I figured I had nothing to lose. I have a small drill bit set in increments of 0.1mm, and I slowly stepped the bore up to 2.0mm.  So far, so good. I put a bit if mineral spirits in the gun and did a test spray. It worked.

Next, I needed to get the primer ready to spray. Thatís easier said than done. This stuff settles out with a deep layer of thick goo at the bottom of the can. I had a paint stirrer that attaches to a drill and worked at it for a good 30 minutes to get the primer mixed up again. The tech sheet said to optionally thin with urethane reducer by 10% to improve flowout. I figured I needed all the help I could get, considering the crappy gun I was using. So, I prepared a small batch, thinned 10% and with the catalyst added in accordance with the instructions. I mounted a large piece of masking paper inside the booth to spray test patterns and set to getting the gun set up to spray properly. It took some time to get the gun dialed in, and I needed to add about 2 psi more than the gunís maximum rating to get proper atomization. I started by shooting the backs of the doors, and the underside of the trunk and scoop. I figured that if I got the gun set up wrong, or had technique problems, it would be best to find out on the least visible surfaces. They went fine, so I moved on the front section:

Then the rear section:

I shot a total of 3 coats on everything. The instructions require 10 - 15 minutes of flash time between coats, and a maximum pot life of 30 minutes, so you need to work quickly to get 2 coats per pot. Even with all the work getting the gun set up, I was still getting a fair amount of orange peel, so I started by blocking everything off with 180 grit. Once I had everything reasonably straight, I sprayed a guide coat:

If you donít know, a guide coat is a very light coat of a contrasting paint. I used a paint specifically designed as a guide coat so it will sand easily. The idea is to block sand the guide coat, and any paint that remains will indicate low spots. It works well. So after applying the guide coat to the front section, I started block sanding with 400-grit. Normally, I would not skip grits, but the Slick Sand sands so nicely, that I believed that the 400 would fairly easily take out the 180-grit scratches. Either way, the guide coat will tell me if I leave scratches.

 

More sanding...

The 400-grit did a fine job of wiping out the scratches from the 180-grit.

When block sanding, it is important to use the longest blocks you can. The longer the blocks that you use, the less likely the block is to follow flaws, and the straighter the car will be. They also tell you never to sand by hand. Well, on these cars, that just plain impossible. If you do find yourself needing to sand by hand, fold up the sandpaper several times to make it stiff and apply as little pressure as you can so as not to leave grooves from the pressure of your fingers.

Anyway, here you can see how the guide coat works. This is clearly a low spot that will need filling:

Iíll use glaze to fill the low spots. You may have noticed that I sanded clean through the Slick Sand in some places. Thatís OK. I wonít need to put on another coat of Slick Sand since I will be applying a coat of sealer. Stay tuned...

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