A guide to bodywork

So you've got a mini and itís due for some repairs.  Maybe you bought a project or perhaps you've owned it for a number of years and itís finally showing its age.  You're contemplating doing the work yourself but you're afraid you'll do a bad job.  I'm here to tell you that you can do a good job with a little guidance.  My first project years ago I jumped into blindly, and frankly I did a bad job.  If you've taken the time to do your research and are reading this page, you're already one step ahead.  I have no formal training, its all been research or trial and error to perfect my skills.  Almost not a job goes by that I don't run into a new obstacle or learn something new, but that's half the fun of this hobby.  There are several ways to go about autobody.  Many opinions, methods, materials, and styles.  Here are some pointers that I will share that will help you get started in the right direction to do a good job the first time. 

Let's talk about rust repair

If you're painting you're mini there is most certainly rust involved.  Walk around the car and really eye ball it, take it all in.  Strip the interior and check out those floors.  Poke around with a screw driver at those bubbled up spots of paint.  There's rust and the more you tear into your project the more you're likely to find.  Don't be intimidated by what you find! 

There are many levels of projects from the basic respray to the complete bare shell top to bottom restoration.  You need to determine what level your car falls under.  How far do you want to take this project?  Do you have floors that look like swiss cheese?  Do you have bubbles and rust around the headlights?  Apanels?   How does the first 5 inches of the car look?  The first 5 being from the floors up the side of the car about 5 inches.  After you work up higher than this, you may find there is absolutely nothing rusted.  So, do you want to strip the entire car or just that first 5?
Rust repair itself can be tackled any number of ways once you've determined which areas need replacing.  Look at the panel and decide:  do I need to replace the entire panel, make a fabricated patch, or replace only a section of the panel from part of a new panel.  Use common sense.  If you stripped the wings and front end and the only rust was a dime size hole your flares covered, patch it and move on.  If its rotten along all the seams and bent up, just replace the panels.  For the most part though the more of the original panels you leave in tact the better.  Maybe your front floor pans are rotten in the corners.  Well, no reason to replace the entire pan, creating a lot more work for yourself and taking away from the factory craftsmanship in the process.  Just use a new pan and cut the section you need to fix your rotten area.  This method of thinking can be applied across the entire body as you find rust.  You don't have to replace the entire windshield scuttle, you can just replace the areas that are rusted beyond repair.  You don't have to reskin the whole door, you can buy just that bottom section that loves to rust.  If your floors look like swiss cheese, by all means buy a whole new floor or floor halfs, leaving in that factory tunnel that's still in good shape.  You don't want 100 patches on the floor, you want a factory look.  Clean. 

You may find yourself repairing detailed areas that involve both fabricated patches and sections of replacement panels.  To me this is the most fun.  Itís a puzzle basically, and you get to make the pieces that make the puzzle fit together.  Again just sit and absorb the area that needs fixed.  Decide what you need to do to make it look factory again.  Take your time and put your tools to work making the pieces come together.  If you mess up a fabricated piece, no big deal, try again.  You'll get it and you may even surprise yourself how well it turned out!

An angle grinder, air chisel, drill, lots of vice grips, clamps, a small metal break, and mig welder will go a long way.  If you have a big shop full of nice fancy tools more power to you.  Spot welders or those 220 mig welders that use gas are certainly desired tools, but not necessary.  Metal on a mini is thin and the welder you use does not need to deliver big power.  Flux core will do the trick and either way you'll more than likely depending on the area be grinding down the welds with an angle grinder regardless.  So nice welds aren't a requirement.  If you've never welded, mig is easy.  I started with one of those cheapo harbor freight flux core welders.  It had a low and a high setting.  The low setting with a wire feed speed set in the middle was all I needed.  These days I have a slightly better lincoln that has 4 power settings that is still flux.  Practice on metal ahead of time and perfect your welding skills.  The beauty of welding a mini is it doesn't have to be pretty.  You'll grind it down and reweld till you get it right, then you'll run a little body filler over it and sand that down till its perfect and ready for primer.  Slow burst when welding thin metal is how I approach it.  Itís easy to burn through thin sheet metal so take your time and be easy on the trigger.  Again, practice a little and you'll figure out what works for you.  Spot welds are preferable done with a spot welder.  In the case you are stuck with your mig, drill out where you want your spot welds, and then weld it in.  I finally have gotten to a point where I can take my 4 power setting flux core lincoln and hit the holes just right on the high setting I can get 9 out of 10 spot welds in one shot with no grinding down later.  But hey, even if you find yourself grinding down some lumpy spot welds, you're only out a half hour on a pair of cills. 

I mentioned an air chisel.  In the event you are finding yourself removing panels and having to break factory spot welds, the air chisel is a must.  The beauty is itís cheap and uses little air.  You can also do a lot of damage so take your time!

Should you buy knockoff panels or factory?  When in doubt I would say go with factory.  Thats not to say I don't buy a tremendous amount of knockoff panels though.  Most knockoffs work fairly well, others your metal working skills need to be good to get a good fit.  Look at your budget and decide wether or not you feel confident you can overcome obstacles that are associated with knockoff panels, or if you want to spend extra on factory quality panels.     

Paint stripping

If you chose to strip the entire car there are a variety of methods.  Send the car off to be media blasted or DIY.  I use a basic sand blaster that works wonders on small areas or the occasional floor bottom or engine bay, but isn't ideal for a whole car.  Not efficiently anyways and itís highly messy.  Do it outside or in a contained area wearing a respirator and lots of face protection.  Sanding disc on an air sander work, as does sanding disc on my variable speed buffer.  Air sanders take a lot of cfm and your compressor may not keep up, but an electric variable speed buffer with sanding disc fitted may be a better choice.  Some areas may need a wire wheel on a drill, while other areas may be easier with a basic sand blaster.  Do you need to use 35 grit to cut through the 2 inches of bondo the guy before slapped on the side of the car, or is 180-220 grit enough to slice through to bare metal quickly.  You certainly don't want to be gouging away at the metal with low grit paper or an angle grinder creating not only more work later in the body prep phases, but also wearing the body down for the restore in its next life.  Chemical strippers work, but I find them to be messy and even more time consuming.  There are many methods to the madness when it comes to stripping paint from the body.  You'll have to decide which method works for you.

Materials explained

Etching primer, sealer primer, urethane, epoxy, filler primer.  Itís all very new and confusing to you, so let's break it down.  You need primer to both protect the body from the elements while you prep for paint, but really itís what the paint sticks to.  So don't over think it.  With that said there are many ways to approach which kind of primer you want to use.  Etching primer as the name implies self etches bare metal creating a strong bond.  Sealer primer seals, simple as that.  It prevents moisture from penetrating through the primer to the metal, in turn creating the rust you spent all that time removing.  You will find two different kinds of sealer primer, epoxy and urethane.  Epoxy is meant for bare metal while urethane typically is not.  Since I skip etching primer these days due to the fact my bare metal is sanded up from removing paint I go straight to epoxy sealer on bare metal.  However let's say you spray etching primer on bare metal, you could spray urethane primer on top of the etching primer.  You can spray urethane over existing primer, paint, or clear for that matter.  You can of course spray epoxy over the same surfaces.  I find the brand of epoxy I spray is a little thinner than the same brand in urethane.  I tend to use both epoxy on bare metal, then switch to urethane.  The choice is yours though.  Filler primer as the name implies fills.  Also sometimes referred to as buff primer or high build primer.  It sprays thicker with the intention of sanding down.   

The term basecoat is in reference to paint.  Whichever brand of paint you go with, I suggest going with one of the higher end lines they offer.  Suppliers will have a low end line, sometimes paint in the middle, then high end paint.  You don't have to drop 500 bucks a quart, but if you find yourself paying 50 bucks a quart you're probably not paying enough.  Personally I like dupont, but have used ppg, sherwin williams, matrix system as I recall, and a number of others.  As its been said before, paint is paint.  Just try to stay clear of the low end cheap stuff.  Dupont has a nason line that's not their top end paint, but is pretty good if you're on a tight budget. 

Read your cans.  When you buy primer, paint, or clearcoat, the cans tell you what you can and can't do.  It tells you the ratios to mix the activators and reducers.  Follow them to a T.  It will mention flash times.  Flash time is the time between coats.  If it says 30 minute flash time between applications, 1 hour flash for wet sanding, 2 hours dry sanding, it means just that.  Always think adhesion.  If you wait too long outside the flash period to make your next application you will want to scuff with scotchbrite or sand the surface before making another application. 

Speaking of paint, how about quantities required.  If I'm doing an exterior respray 1 quart is all I need.  This of course is reduced 1:1 so I end up with a half gallon sprayable.  A pint to do a roof and stripes.  Or two to three quarts for a full top to bottom job.  Primer for an exterior job might take two quarts with maybe a quart of filler primer.  A bare shell restore a gallon of primer usually does it and depending perhaps two quarts of filler primer. Clear coat two quarts will do an exterior job, but a full shell I will use a gallon.  Two to three coats on the clearcoat.  These figures can vary but a rough estimate to help the first timer. 

Paint Guns

Paint guns.  Lots of choices from the cheap purple harbor freight gun to the guns that cost hundreds of dollars.  I use 3 different guns.  One is a bottom feed detail gun for hard to get to spots.  Holds 8oz, has a 1.5mm tip and while it only cost $20 from harbor freight, it does a surprisingly good job for the areas I use it on, such as underside of wings, inside the boot, and nooks and crannies that my top feed gun can't get to as easily.  I use a 2.0mm tip on a bottom feed gun I use for filler primer and a 1.3mm top feed gun on the main job for the finished product.  Tip sizes vary for the type of application.  For sealer primer, basecoat, and clear, a 1.3mm tip is pretty standard.  Sprays nicely and doesn't waste.  Filler primer is too thick to spray out of the 1.3mm tip, so the 2.0mm tip is what I use.  My 1.3mm top feed gun that I use on the "main job" is also the gun I spent the most money on.  $300 to be exact.  That's not to say you need to spend that to do a good job, but spend less on a filler gun and detail gun and more on your "main" gun.  Not that you need three paint guns, but it can make the job easier.  Another important note, clean your guns!  After every spray I put in a little acetone and shake it around, dump it out, add some more, shake, dump, add a bit more and spray it out cleaning the lines.  I do this till itís clean.  I even put a pinch of acetone in the gun and sit it back on the shelf for next time after I'm done cleaning just to be safe.  Ten minutes of cleaning the gun after you sprayed will save you an hour tearing the gun down unclogging dried paint later.

Now that you understand which materials to use and how to apply them, its time to put this knowledge to use.

Body Prep

You've found rust, stripped the body, and made your repairs, you're ready for all that glorious prep work for paint.  This is where you're paint job will shine.  The more elbow grease you put into your prep the better the paint job. 
You can do the worst job welding metal, body filling, and spraying primer, but you need to do a good job block sanding with the right grit sand paper.  The bigger the block the straighter the body will be.  Areas that have dents, dings, repaired sections with either heaps of body filler or filler primer you will want to use a big block with low grit paper.  1000 grit would take too long to sand through these repairs, but 80, 60, or even 35 grit will cut right through it.  Autobody shops sell these longer blocks you will want to use as well as the sandpaper that fits it.  Your sanding strokes should be done in such a manner you aren't sanding ruts or paths in the side of the car, but rather feathering it all together into a seamless flat surface.  If you find yourself sanding with your hands in hard to get to spots a block can't reach, use your palms and avoid using your finger tips as much as possible.  You'll cut lines into the body that will show at the final stage when you clearcoat.  Flush long strokes at opposing angles to create the perfect surface is what you want.  You will find that sometimes you will primer, sand, fill, sand, primer, fill, sand, primer, and sand.  Then maybe do that some more.  Initially you'll use the low grit on the long block to work out the body filler and filler primer on the bad areas and eventually work up to 320, 400, or 600 grit.  An example of what you can expect would go something like this:  You filler primered the rear quarter panel where you made some repairs, banged out a dent, and had skimmed some body filler over a section you welded in.  You then block sanded with a long block and 80 grit paper.  You proceeded to spray a couple coats of urethane primer and let sit for a couple hours before taking a smaller block and 320 wet sandpaper and sanded down till you hit a little body filler and filler primer.  You run your hand over the surface while itís wet and feel a couple remaining dents you can't visible see.  You contemplate spraying the two spots with more filler primer but decide to skim coat with body filler.  After the body filler hardens you use the smaller block and 80 grit and sand the body filler till flush.  You primer once again and resand with 320.  You find a couple pin holes where you applied body filler.  You take glazing putty and press it into the pin holes, let dry, sand, and reprimer.  Now that you feel comfortable this section is "perfect" you make a final sand with 400 or 600 grit for the basecoat to be applied to.  As you can see you may find yourself working an area for awhile.  Sometimes I'll mist a little paint over the primer before the final block sanding.  This allows me to see any low spots which are identified by the remaining paint that was misted on.  It is imperative that the final surface before applying basecoat is not only flat but that the surface is no more than 320 grit.  Anything lower will show sanding marks.  Which is why I recommend 400 or even 600 grit for the final sand.  It still allows a rough surface for good adhesion, but is smooth enough that your basecoat/clearcoat will have a canvas to lay down smoothly on.

Now that you've spent a week block sanding your body to perfection and have the perfect surface for paint you're ready to spray a show quality paint job.

Spraying basecoat and clear

Basecoat solids are fairly straight forward and relatively easy to spray while metallic have some issues associated with them.  Again, read the cans to the paint and follow the directions.  Use a water separator on your compressor to keep moisture out.  Stir the paint well in the can before each use, use filters when putting the paint in the gun and spray using 40-60psi from the compressor.  You will want to dial in your gun to have a spray pattern that isn't too narrow or too wide.  A six inch path is a good starting point while spraying.  You will not want to hold the gun too close nor too far away.  Too close will cause runs and waste paint and too far away will also cause waste as well as orange peel while clear coating.  6-8 inches away from the body while spraying is a good reference point.  Two to three coats should give you full coverage.  If you're spraying metallics two to three coats will provide coverage, then mist coat over the body.  This is one time you'll want to hold the gun further away to allow the paint to fan out wider.  This mist coat will allow the metallic to lay evenly and prevent tiger stripes.  If you have tiger stripes they will be visible after the flash period by noticeable dark lines.  If at anytime you mess up the basecoat, itís still not that big of a deal.  You can sand out runs if needed, and all you need to do is respray the section you had to sand.  You are not however allowed to clearcoat over sanded basecoat.  The sand marks have a tendency to show under the clear, or have a discoloration.  Just make sure your basecoat is one solid color, free of debris, and has a fresh coat of paint layed down.  Again, if you had to give up on painting midway through and your flash periods expire by a significant amount of time, you will need to roughen the surface and respray.  Adhesion is important.   

I have been told you can clearcoat up to 24 hours after you sprayed your basecoat.  Quick tip, use a tack cloth to wipe down the basecoat to remove fine dust that may have settled on the car before you clear.  With that said, I try to clear over basecoat within an hour.  Some exceptions include when you're laying out stripes or say a checkered roof.  In my mind the sooner the better as the chemical bond is stronger for adhesion.  I have yet to have a job peel off.  The clearcoat in my mind is one of the hardest parts, least forgiving, and can make or break a good job.  It tends to run a little easier, and bad runs often times can't be fixed, unless you sand down and reclear.  Even then itís easy to sand into the basecoat, which requires to respray base in the spot you sanded through before reclearing.  You can get debris in the clear which can forever be imbedded into your job, or bad orange peel which can be a real bugger to color sand out.  Sometimes itís easier to just sand down with 320-600 grit and reclear if the orange peel is bad enough.  So if you do a bad job here, it can be fixed with more sanding and time.  The best clearcoat job is one that is on the verge of running.  The flatter it lays out which in turn requires the least amount of color sanding.  When I lay the first coat of clear I am careful not to spray it too thick, then depending on temperatures let it flash from 5 to 15 minutes.  The cooler the temps the longer I wait to spray the next coat, which is then a little thicker of a spray.  Flash times on the can will probably mention ten minutes, which is not uncommon.  When spraying the clear you want to keep the line your spraying overlapping the last line to keep a continuous "wet" look.  If you get a "dry" spot, its ok, you can color sand it out later.  The more continuous wet surface you have the better.  Hold the gun close enough the path isn't too wide, again 6 inches and not much more.  The further away you are, the more orange peel you will get.

Color Sanding and buffing

Color sanding is the final step before buffing.  This is where you'll take 1500 grit and 2000 grit wet sandpaper and sand out dust nubs and hopefully the minor amount of orange peel you have.  If itís bad you can start with 1000 or 1200 grit and work up to 2000 grit.  If itís minimal you can go straight to 2000 grit.  Avoid sanding edges, as itís easy to cut through the clear.  Use your hands to sand and be cautious of grit or debris under the sandpaper.  Use lots of water.  If you feel grit under the paper, stop immediately and clean it off.  You are most likely grinding a particle across the clear creating a scratch.  Dry with a cloth as you go to observe your work and eventually the surface will be completely dull in color, with no shiny spots.  If there are shiny dimples and specks, keep sanding, that's the orange peel.  Now that you're completely sick of sanding take out your variable speed buffer and a deep cut compound and buff the car.  Keep it wet and avoid too high of a speed to prevent burning the clear.  Careful on the edges as you will cut through them easier than you may think.  Another plug for harbor freight, but they sell a very affordable variable speed buffer with velcro pads that works wonders.  I'll use a deep cut compound and 3 or 4 others till I get down to glaze.  I use a separate pad for each one.  Keep on buffing and working your way down to glaze or swirl remover at the least till you have your show room finish.  The sooner you color sand and buff after clear coating the better.  The clear will not be fully hardened and easier to work with.  However wait 24 hours before you colorsand and buff!  It stays fairly tacky that first 24 hours and can easily be ruined.  You should wait two weeks before waxing the car, as itís still curing. 

Hopefully this information can be useful and help you along in your project.  As always post up your project, ask questions, and browse what others have done to help guide you along.  If you're still unsure in your ability to do your own work, there are some of us who are always willing to take on the next project for you!  Good luck and hope to see you around.