Preparing an aircraft to be painted is a lengthy job consuming a lot of time sanding and filling all those imperfections if you built yourself a composite aircraft. Aluminum has some advantages but needs to be cleaned properly before any paint will stick. Composites can be made to look perfect where aluminum does not quite look so superb.
Also, you also need to make a decision if you spray paint the aircraft yourself or have an experienced aircraft spray painter do that job for you. It depends on how much paint background/ experience you have and the amount of money you are willing to spent on that part of the aircraft.
Either way, you can do a lot beforehand so that the cost of the paint job is not too excessive and you still end up with a perfect paintjob on your dream machine.
Prepare for some sanding, cleaning, sanding and more cleaning....you get the idea.
This part of the job will take the bulk of the time needed to get the paint on the aircraft. At times it will seem that there is no end, discovering more and more unfinished and imperfect areas as you go along.
Sometimes overlooked but providing all the necessary tools, masking paper and tape and other equipment needed to protect parts that not need to be painted will take a lot of time too. Not all of us have a paint booth available nearby so you need to build one yourself with good ventilation, heating and lights. Good respirators will also be on your list of protection equipment.
Get yourself a reliable compressor with a large tank, 50 liters or more. A good spray gun, several, and paper towels and tack rags will be needed. Of course, lots of sand paper of good quality (3M) in different grit numbers from 60/80 up to 1000 and sometimes higher will be on your shopping list.
To remove air from the booth you will need one or two large floor fans. Safety dictates that a fire extinguisher is required and a no smoking policy must be enforced due to the flammable thinners and solvents you are going to work with in a small confined area.
You are bound to spill paint somewhere so old clothes and shoes might come in handy too.
Before starting off you must inspect the item to be prepared. Use a portable fluorescent light so you can hold it close to the surface to see any shadows made by shallow imperfections. This way they are very easy to see and marked for sanding and filling.
Use micro-balloons and epoxy to create a filler. This is very lightweight, easy to sand and it is not so heavy as normal Bondo, and you will probably need lots of it to create the perfect finish without adding all that weight.
During construction, several parts might have picked up oil, grease from your hands, glue, silicone and what not. You will need to remove these impurities as paint will not stick on this. You might want to use MEK, Acetone or other removers to get rid of the waxy film that has formed by touching parts with your bare hands.
The same must be said for pencil and other markings needed for construction, sometimes they will bleed through the paint.
Clean all parts with compressed air and a vacuum cleaner, make sure that you get into every corner of the fuselage, use brushes if needed. You might pickup some spare parts or other items you lost/misplaced during construction too!
Sharp edges do not hold paint all that good, it will chip and crack off very easily. Make sure that every aluminum part with a sharp edge is filed round and smooth. The more area the paint has a grip on, the better it will stick and it will last that much longer.
This cleans up the surface and roughens it up so that the paint can adhere. Large areas can be done with special tools, but make sure not to sand into the structure. Use flat sanding block of different sizes and use straight strokes in stead of circular movements.
After sanding clean up all dust with some good tack rags, vacuum cleaner and the use of compressed air. Use gloves so that any oily film from your hands does not get onto the parts again.