The Body Experience
FFR2572
Tom Murphy

I am no expert on body work. I had never done a fiberglass vehicle. My paint and body experience goes way back to my first car. I slapped bondo on it, sanded and painted it with lacquer. This took an entire summer and turned out OK, but far from perfect. From there I painted several other vehicles with one part enamel. Now here it is 18 years after painting my first car and at least 15 years since picking up a spray gun. So does that experience count as experience? Well, maybe. I do remember that learning that I did not want to do it for a living, that it took much more time than expected, lacquer took way too much rubbing, and a run in enamel could not be fixed easily. I first thought that I would get someone to do the body and paint on my FFR, but lack of money and no FFR experienced body man nearby led me to do the research. Also there was this feeling inside of me that kept telling me to do it myself. It would be much more stressful for me to have to deal with someone working on my car than to just do it myself. After much research on the Forum, members web pages, and paint product manufacturers web pages, I decided it was a go. There are many products to use and many ways to do this project. My way worked for me, but I cannot guarantee your success.

The Start:

With the body mounted on the completed chassis, I checked fit of the doors, hood, trunk, and all trim pieces. Some grinding was needed for the lights, roll bar holes, windscreen holes, etc. I found that I needed extra clearance for the side pipes in the body opening. I marked all of these areas for grinding after removing the body. I did all of my body work with the body on the body buck outside. I did not want to fill my garage or shop with dust, also heat and cooling cycles are good for the body and fillers to get it all settled so to speak before final painting. I removed the body and began by cleaning the entire body 2 times with a wax and mold release remover from West Marine. Then I began grinding on the marked areas using a Dremmel tool with a sanding drum. I used the Dremmel also to put a radius on the edges (inside and outside) of all the cutouts. I used a cheap 4" angle grinder with a rubber sanding pad attached using 80 grit discs to clean up the hood and trunk openings, louver openings (removing the lip and rounding the edges), wheel well openings, cockpit edges, lower body edges, and other areas. I then used the Dremmel to do the final shaping to my liking. Be sure to wear long sleeves, goggles, and a dust mask when grinding. Then take a cool shower when finished. 

Seam Grinding:

I used the 4" grinder with the rubber pad and 80 grit discs to do most of the seam grinding. I used the wheel at a slight angle to get down in the seam and open up any voids that exist. Some areas were ground maybe 2" wide at the most and 1/8" deep at the most. All the bodies are different and may require more or less grinding. Some areas did not require much at all. Some people have said to remove all of the line of gelcoat down inside the center of the seam. I did not remove all of it because I did not read this tip until my primer was finished. I hope this does not cause any settling later. I also used the Dremmel to grind areas like where the seams go into the door and trunk openings. There is no way to do those areas with a 4" grinder. After grinding the seams, blow all the ground areas with air to remove dust from the pits in the glass. Then clean everything again with the wax and mold release remover.

Seam Filling:
Fill #1
I used West Systems epoxy (http://www.westsystem.com) to fill the seams. I used 105 resin and 205 hardener. The pumps work great, do not mess with trying to mix by hand. I used small disposable plastic drinking cups for mixing the epoxy and Popsicle sticks for mixing. The first application is done with the 105 and 205 mixture without filler. Use a foam paint brush to paint the epoxy on and rub it well into the seams. This is to seal the fibers that were opened up during the grinding operation. Keep the application thin, do not try to fill the seam now. I also used the epoxy without filler to seal up other areas where grinding was done like the cutouts and body edges. Let this dry overnight.

It is not necessary to sand the entire body before the next application of epoxy, but the areas near the seams (say 6" depending on the amount of filler needed) need to be sanded. I used 80 grit paper on a 17" long board wherever possible and smaller boards and pads for smaller areas. I had some panels that were not aligned very good, so I sanded down the high panel some and filled in steps to create a wide fill zone at that area. I sanded the areas around the seams and then started filling and alternated while the filler was drying. 

Fill #2
The next step is to lightly sand the epoxy in the seams after it is dry. Sanding here is needed to open the epoxy so the next layer will bond correctly with the first. Use sandpaper or a scotchbrite pad and make sure the gloss is removed from the epoxy. Put tape along the seams just outside of the ground area. This will prevent epoxy from getting on the body where you do not want it. Mix up some 105 and 205 and this time add some fairing filler. I used the 410 filler. Put enough filler to thicken the mixture considerably to keep it from running a lot. For this step, I mixed to a molasses consistency. Apply the mixture to the seams with some type of plastic squeegee. Keep it fairly thin and do not try to fill the entire area. It will take some practice to get good at smoothing it. 

After this dries maybe an hour or so, pull the tape off. Do not wait until it cures completely, the tape will be difficult to remove. Let dry overnight and do some more body sanding if you get bored. 

The next day start sanding the filler on the seams with 80 grit paper on the long board. Work the board at 45 deg angle to the seam in both orientations (90 deg to each sanding direction). In some places like the rear fenders, I found that a cheap, plastic sanding board worked better to retain the radius on top of the fender. The rigid board was flat topping my fenders. Sand just enough to blend the filler with the body and remove the high spots in the filler. Some areas may be getting close to done, but other areas will still have large low spots. Try not to sand the gelcoat too much because it will open up millions of pinholes. Again here this step will take some practice.

Fill #3 and Beyond....
Always remember after sanding to blow all the dust out of the pores before filling again. Tape the perimeter of the seams again like the last step, but a little wider this time. Mix the epoxy as in the last step, but add a little more 410 filler to make it thicker than last time. Spread as in the last step and pull the tape before the filler dries. By this time you should have the body completely sanded and if you are really into it, the hood, trunk and doors could be underway also. I did these as a side attraction in the garage late at night when it was too dark and cold to be outside.

After filling the third time and sanding as before, the seams should look pretty good in most places. There will be some low places in the filler and any panel misalignment areas will need to be filled and widened more. Just keep filling and sanding until the seams are completely filled and there are no low spots. It would be great if you could not feel anything by hand on the seams at this point, but if you use a filler primer later, you can get rid of small imperfections with the primer. Try to avoid over sanding on the gelcoat. Sanding through the gelcoat opens up pinholes, but if you must then do not worry about it. We will deal with them later. 

Pinholes and other Troubles:

After all the seam sanding, you will have opened up some pinholes in the gelcoat and there are more that you cannot see. I had some voids in and under the gelcoat on my hood and trunk. There were a couple areas on the body, but not many. You need to find all of these areas or you will end up with a sunken area after painting and curing more. The sun curing the body will cause some of the spots to become visible by now and some will be invisible still. Use a wire brush and beat on the body. Yes, beat on it like you are trying to stick the small wires on the brush into tiny pinholes on the body. This will bust open the gelcoat over these voids and make them visible. Also when you see an area use an awl to dig around and expose all of the void. Another trick is to use a bright trouble light and go over the body looking for areas the light will shine through the body. I filled larger voids with West, but in the later stages on the trunk I used 3M Premium Marine Filler. It dries in like 5 minutes, so progress is not halted waiting on the West stuff to dry. Do not mix products on an area. I kept the 3M well away from the West. Whatever you use make sure you press it hard into the hole and get any trapped air out. You want to completely fill the hole with filler and not leave any air pocket underneath. For small pinholes I used Smooth Prime by Poly Fiber from Aircraft Spruce. This is a water base, high solids primer for composites. It mixes with a catalyst. For large areas I rolled it on with a foam roller. When rolling it on, I mixed a little water with it to thin it slightly. I rolled it on all the seam areas to fill small pinholes in the West and where I sanded through the gelcoat beside the seams. And also to give me somewhat of a guide coat over the seams to see where I had low places. I also used a squeegee to apply it in certain areas. Do not worry too much about filling all of the pinholes in this stage before primer, just make sure to find all of the voids and air pockets. The Smooth Prime dries fast and is fairly hard, but easy to sand. Sand it dry with 120 grit.

Sealer:

Before spraying any sealer, I let the body cure in the sun several days and then went over the whole thing again with 120 very lightly, blow with compressed air, washed the body with soap and water and then cleaned it with DX330 cleaner by PPG. Now that the seams are filled, voids filled, pinholes are mostly filled, and entire body is sanded, we need to seal the fiberglass and all of the fillers so they will not react unfavorably with the topcoats. I used DPLF by PPG. This is a 2 part epoxy primer / sealer that dries very hard and is impossible to sand dry because it clogs the paper. It is not necessary to sand this sealer, but if you get orange peel or a run, sand it wet with 120 or 150. It must be top coated with primer within 7 days. If you wait more than 7 days, you must sand the entire surface to open up the pores in the sealer. I let it cure in the sun for 3 days and then wet sanded the entire body with 150. I did not really need to sand because it was pretty smooth, but I felt better doing a little sanding to get out any high spots. Do not sand through the sealer! If you do, just touch it up. The DPLF comes in several colors. I chose blue just because I could. I applied 2 wet coats. The only pause between coats was to fill the gun. Sure did look good to see the smooth body finally one color!

Additional Pin Hole Filling:

After spraying the sealer, you probably will see more pin holes appear. I used more of the Smooth Prime to fill these pinholes. I applied it with a squeegee so as not to have a lot to sand off. I sanded it lightly dry with 120. Some areas took 2 applications to completely fill the holes. The Smooth Prime seems to settle it's way deep into the holes which is a good thing. You do not want to leave air pockets.

Filler Primer:

I chose to use PPG K38 for a filler primer. It is a better, improved version of K36. The K38 is designed to be sprayed on and act as a thin layer of body filler. You can have it as thick as 1/8" so they say. My body was very strait by this time and I probably could have gotten away with a more standard primer. I think I worked the body more than I needed to before sealer. Next time I would spend less time sanding on the seam filler and gelcoat. This would result in fewer pinholes, but not a perfectly flat surface. But the K38 would be able to fill the low areas. 

I washed the body with soap and water, blew it with air, cleaned it with DX330, and went to work with the K38. It mixes 4 to 1 with the catalyst, so it is very thick. It went on smooth and easy with no runs. Like the sealer, I applied 2 wet coats. I had only one area on the body with a low spot. It was in front of the passenger door. It was maybe 1/32" low. So I just would shoot a little extra K38 in this area every time to build it up as I went. I let the K38 dry for a day and then sprayed a light mist of a black guide coat over the entire body. I purchased the PPG Guide Coat in a spray can. The guide coat lets you see low spots while sanding. Using 150 on your long block, lightly sand the surface. Like before, work the block in a diagonal motion, sliding it slightly sideways. Then reverse the action and cross-hatch back the other way. You can even work the board completely sideways first one way, then the other, until the guide coat is removed. Once you have sanded enough to remove all of the guide coat, you will have a perfectly smooth, uniform body panel with no ripples or defects. If you sand through the K38 in an area before all of the guide coat is removed in an adjacent area, you will know that is a low spot that will require more primer and work. Do not cheat by using the edge or end of the board to remove guide coat in a low area. Keep the board flat and the surface will come out perfect. 

Wash, blow, and clean with DX330 as before and then shoot another double coat of K38. Before the final sanding before paint, I let the body cure in the sun for about a week. Just to make sure that everything was settled and would not change later. During this time, I mounted the body to do a final check and check the door fit for a final time. Mist a guide coat over the entire surface. Use 220 on the long block and lightly go over the entire surface, looking for any defects and blocking down any significant high spots. Don't remove all of the guide coat at this stage. Remove just enough to make sure that there are no defects and that the panel is smooth and straight. Then give this surface a very light, fresh guide coat.

Now I start wet sanding with 600 grit. Use warm water with a little dish soap in it. The soap acts as a lubricant to keep the edge of the paper from sticking to the surface. Wrap the paper around a foam rubber sanding block and sand in a diagonal cross hatch motion as before. Keep sanding until all of the guide coat is completely gone. This will take several days. If you sand through the K38 any where, you will need to shoot more in that spot, guide coat it and work it flat. For small places I used my hobby air brush to touch up the primer. It was so much easier than using the big gun. Once this is finished and all of the guide coat is removed, the surface will be perfectly flat and have a little shine.

Basecoat:

Wash, blow, and clean with DX330 as before. I used PPG DBC basecoat. It mixes with DT Reducer. The basecoat applies at a lower air pressure than the primers. I applied 2 wet coats of the white down the center of the car where the stripes would be. No masking, just shoot it plenty wide for the stripes. I let this dry for an hour and then taped up the stripes. I used the blue 3M fine line tape. I made measurements when the body was on the frame for the final fitting, so I just went by my drawing and eye to mask off the stripes. I used paper and then tape over the paper to make sure that I had all the white stripe area sealed off. Then I shot the whole car with the blue basecoat. Again 2 wet coats. The basecoat dries quickly and is pretty dull, so do not worry about it. I waited about 30 minutes and then pulled the tape. I had one small spot where a little blue over spray snuck through the masking. My helper (Will) was worried that we had a major problem, but after thinking about it a minute, I used a pencil eraser and slowly sanded the blue dots off of the white. Now it looked perfect, except no shine!

Clear:

I used PPG DCU2010 clear. This mixes with the catalyst and DT reducer. The basecoat has to be clear coated within 24 hours or you have to sand and apply more base. The clear went on pretty well. I mixed exactly as the directions said and it was smooth. If you have an orange peel problem, add a little extra reducer, but beware of runs. I guess all the paint gods were with me because I did not have any compatibility or application problems. I applied 2 coats of clear. The clear is some sticky stuff and takes a while to dry. When I was finished I felt like a giant piece of fly paper. I was sticking to the floor because all my water had evaporated, sticking to the gun, and everything was sticky. I did not wear a paint suit because I was afraid of unfamiliar clothing and it falling into the paint. It took 2 weeks for the sticky stuff to wear out of my hair and off of my arms. 

Cut and Polish:

I thought long and hard before taking sandpaper to the clear coat. But there were a few bugs in the clear that had to be flattened out. I started with 1500 grit wet paper wrapped around the foam rubber sanding block. I used a bucket of water with a shot of dish soap. Soak the paper in the water and start sanding. You can really see the imperfections in the clear when you sand a little and then dry the area. The clear is not completely flat even though it looked perfect. I tried this on my truck and found the same thing. Factory clear is not flat. It has a orange peel to it even though it looks good. Anyway, I kept sanding to remove most of the high spots with the 1500 and then switched to 2000 grit wet and sanded until the surface was completely flat and smooth. You cannot see your progress with it wet, so dry it off and check often. This took a couple days of going around the car to get it perfect.

Next step I used 3M Perfect-It 3 rubbing compound on a 3M white foam compounding pad attached to a DeWalt variable speed polisher set at 1400RPM. Start slow spreading the compound using medium pressure and as the compound dries, speed up to 1400RPM and reduce pressure to light. The wipe any remains off. I did this step 2 times on most of the body. This will bring out a good gloss, but will leave some swirl marks.

Next I used 3M Perfect-It 3 Machine Glaze on a 3M black foam polishing pad at 1400RPM. Like before use medium pressure and slower speed then as the glaze dries, speed up and reduce pressure. I did this step 2 times. This removes the swirl marks and brings on more gloss.

Last step I used 3M Perfect-It 3 Finishing Glaze on a 3M black foam polishing pad on my air DA sander. You can also apply this by hand if you like. Apply a thin coat and let it dry and haze over. Then wipe it off with a 3M yellow detailing cloth. This gives more gloss and a little protection until it is time to wax in 60 days.

In the end it was well worth the time and effort to do the cut and polish. The body is smooth as glass and a great gloss.

My Paint Booth:

I constructed a paint booth in my one car shop in the back yard. I stretched strings from one end to the other and draped plastic over them creating a tunnel for the car. I taped the plastic together and to the walls with duct tape. I hung the plastic below the level of the roll up door so I could open and close the door. I sealed off the door end with plastic sealed to the plastic walls and plastic ceiling. I cut a small flap out near the floor on the door end for fumes to exit. I taped a furnace filter to a box fan and put it in the window at the back end of the shop blowing in. I sealed the filter to the fan and the fan to the window with duct tape. The fan blowing in created positive pressure inside the booth so nothing could fly in except through the fan/filter. It also poofed out the plastic against the walls of the shop and made the booth effectively larger while the fan was running. Like blowing up a giant balloon. I scrubbed the floor, blew out the whole thing, vacuumed it, wheeled the body inside, wet down the floor and went to spraying. 

The first filter I used was the standard blue fiber furnace filter. I had this when I painted the body. I think the few tiny bugs I had get into my clear coat actually came through the filter. That is my theory anyway. I had no problems with this setup during the primer steps, but Murphy's law got me went I sprayed the clear. Between the primer and color I actually painted some furniture in the booth and just scrapped all the plastic and started fresh with new plastic when I started color. The standard filter gave me good airflow, well about as good as I could expect in such a rig. I painted the doors, hood and trunk a month or so after the body. For this I changed the filter to the pleated type furnace filter for finer filtration. I did not have a bug problem this time, but the airflow was greatly reduced. It was not a problem with small parts like the doors, hood, and trunk, but it would have not been enough airflow to keep good visibility to paint the entire body. 

For lighting, I had one 4 foot fluorescent fixture overhead and I robbed 2 more from my garage and put them horizontal on the walls near the floor on each side of the car. This worked OK, but I could have used more light at times when the fog became thick in the booth. I suppose a HVLP gun would have reduced the fog also, but oh well.

References:

http://www.northcobras.com/video.html  Body Video by Roger Stine
http://www.tricitypaint.com/docs.html  PPG data sheets
http://www.autobodysupply.net/ 
http://www.westmarine.com 
http://www.cobralads.com/butcher32.html  Andy Dunn "The Butcher"
http://www.quickkeys.com/Cobra/Default.htm  Wade C
http://www.hometown.aol.com/pepeborja/Cobra.html  Jose B
http://corporate.ppg.com/PPG/SBU/AutomotiveRefinish/Default.htm  PPG
http://www.3m.com/US/auto_marine_aero/aad/  3M

Go back to the FFR FAQ