With the proper professional tools and modern quality paints, anyone can complete a professional paint job even if you have no experience. Painting equipment and modern paints used today make it much easier for any individual to paint their own aircraft. Waterbase paints are becoming widely available. For aircraft builders, you have spent years building your masterpeice so why hire out the finishing touches. Aircraft builders have the added advantage of a desire for perfection and perserverence. Even if you have never picked up a spray gun you can do the job.
Professional painters for hire are often motivated by profit. Many want to paint your plane as fast as possible an move on to their next pay check. Many are auto painters, and are not used to the paints used in the aviation industry. An example is fabric covered top coats like dope. A professional paint job can easily range in the $3000 to $4000 area.
You can paint a plane assembled or unassembled. A first time painter will be better served to paint the airplane prior to assembly. It is much simpler to paint the individual parts of an airplane rather than to paint the entire airplane at one time. However, a smaller plane is not as difficult as painting a large assembled aircraft. Some builders will want to wait until they have test flown the airplane prior to painting. That enables them to correct problems and make necessary changes resulting from the test flying period. Some of these changes could affect the finish of the aircraft so they will wait until this time for final painting. Again, if you possibly can, paint the airplane prior to assembly.
You will gain experience quickly. Before you begin applying the finishing topcoats you will have acquired much experience spraying primers. The primer coat does not show so if spraying mistakes are made they can be easily corrected. You can also practice spraying techniques on large pieces of cardboard, scraps, etc. , old doors, masonite, stove pipe, etc.. If you are painting a fabric covered airplane you will have literally hours of practice spraying the more viscous coats of chemicals used on fabric. Then when you are ready to spray the final color coats you can do so with confidence. The bottom line is this painting an airplane is usually approached with much more fear than is necessary.
Whether or not you elect to paint your entire airplane you certainly will end up painting a number of small parts anyway so consider investing in good lifelong equipment and paint the airplane yourself. You will then also be able to maintain your plane and touch up with your gun.
You will want a large well lit area to paint your plane. If you are painting by piece you can use your garage. Some builders are fortunate enough to locate a hangar or other such facility for their painting. Bear in mind that some airports will no longer allow painting unless the shop is designed and built to comply with local restrictions. Certain locations require the user of solvent based paints to filter overspray and have a method of collecting waste. Consider using todays modern waterbased paints and you will not have this problem.
A garage or workshop is adequate. After you have found a suitable location you can easily build a poor man's paint booth. This can be done very easily by using a wooden frame or PVC pipe and plastic sheets. Build a square frame out of wood or PVC pipe large enough to cover your airplane or the largest surface you will be spraying. You should allow enough space to be able to walk around the surface. You can hang the frame from your ceiling. If you have a car port you may be in luck. You can even use an outside tree. Cover the roof and sides with plastic sheeting stapled or taped to the frame. Tape the sheets together using duct tape. At one end of the booth place a furnace filter and at the other end we also recommend you placing a furnace filter and seal it off. You can place the fan "outside" of the spray area to draw the air our. An explosion proof exhaust fan with an enclosed motor is the correct way to do this. If you are unsure about the fan, leave it out and quit spraying when the booth becomes full of overspray. The overspray will settle in minutes and then you can go back to work.You can also ask your dealer about non flamable waterbased paints.
Lighting is of utmost importance best at 45 degrees to the surface being painted. When you are painting you cannot have too much light.
You will also want to hang small pieces of your airplane for spraying. You can use PVC pipe or a welding rod. The length of pipe or wood can be suspended from the top of the spray booth.
Certain health hazards do exist with spray painting. If worried go with modern waterbased paint. Hazards depend entirely upon the chemical that is being sprayed. The most significant health hazard occurs when atomized chemical particles are inhaled. You must protect yourself with an adequate respirator. A charcoal filtered respirator, such as the one pictured, is sufficient for most primers, dopes, and paints. However, if you are using any type of polyurethane paint you should have a forced air breathing system. Polyurethane paints emit polyisocyanides that can be extremely hazardous to certain individuals. Some people have severe reactions to polyurethane so don't take a chance. A good investment to protect your health.
You also need to protect your skin with gloves and a cheap paint suit available where you purchase your paint. Follow the manufacturers safety requirements and if flamable do not use power tools while you paint.
TYPES OF PLANE SURFACES
Aluminum surfaces are treated differently depending upon whether the metal is new or used. Paint must be able to "grip" or adhere to the surface onto which it is applied. Most aluminum surfaces have a layer of pure aluminum on the surface called alclad that protects the metal from corrosion. It is very smooth and not favorable to paint adhesion. Therefore the surface must be adequately prepared by cleaning and slightly roughening to guarantee primer adhesion. This is accomplished by using a conversion coating such as alodine. This chemical process creates a ceramic layer over the aluminum that coats the surface and provides tooth adhesion. Used aluminum must have any primers, paints, or corrosion removed. Paint strippers are used to remove old paint. After stripping old paint the corrosion should be completely eliminated. Use fine sandpaper, Scotch Brite pads, or aluminum wool. Never use steel wool or a steel brush. After the corrosion is removed the old aluminum should be acid etched. This is simply a process of washing the aluminum with a product such as Poly Fiber's E-2310 Acid Etch diluted with water. An acid etch removes oil and light corrosion while etching or roughening the surface to provide a firm primer bond. The part is then thoroughly rinsed. Next wash the surface with E-2300 Conversion Coating that inhibits corrosion and further enhances primer adhesion. After this step the part is rinsed and allowed to completely dry. Once again, new aluminum surfaces need only be treated with a conversion coating.
After the aluminum (new or old) has been properly cleaned and treated, it is then primed.You can use a two-part epoxy primer. An epoxy primer will insure corrosion protection and also provide a bonding surface for most topcoat paints. Very often, polyurethane topcoats will lift or wrinkle primers other than epoxies much as a paint stripper would do. A primer is necessary to provide a bond between the metal and the final topcoat paint. The primer coat should be applied according to the manufacturers directions. Usually, two light coats will be applied. Heavy coats should be avoided.
Steel surfaces are much more susceptible to corrosion problems in the form of rust. This rust must be completely removed prior to priming the part. Of course, any old paints or primers will usually be stripped. Certainly, if you are going to paint over the existing topcoat you must still deal with any rust that might be present. Removal of old paints can be accomplished with a bead blaster or sand blaster found for as little as $40.00. However, this must be done without pitting or damaging the metal. Using the proper amount of pressure in blasting is essential. Once the structure has been stripped and the rust eliminated, the metal must be protected within 1-2 hours. Be sure to have the primer and spray equipment ready before you begin blasting or cleaning. Rust will begin to form on a bare steel surface within a very short period of time. Just as with aluminum, after cleaning the structure prime it using an epoxy primer. Be sure to clean the surface with a surface cleaner just prior to priming.
Wooden surfaces are usually covered with fabric. They still must be properly prepared to prevent rotting problems from moisture. Usually the part will be dry sanded and then varnished using a two-part epoxy varnish. Solvents used in fabric covering systems will "lift" most varnishes other than epoxies. If you plan to paint directly over the wood itself, an epoxy varnish must be used.
Fiberglass parts should be sanded smooth and primed using an epoxy primer. Of course, if you are building a composite airplane the surfaces must be filled and primed.
As a general review, all surfaces must be cleaned, any corrosion removed, and then primed prior to painting. Epoxy primers come in a variety of colors. The most popular colors are green, yellow, and white. White colors are much easier to cover with final topcoats. It is your choice. Zinc chromate has been used for years as a primer. However, its popularity is decreasing with the advent of epoxies. Zinc chromate should not be used if you plan to apply polyurethane paint.
The elapsed time between priming and applying the topcoat will vary depending upon the brand of paint used. Different manufacturers use varying times. Usually, an epoxy primer should completely cure and harden prior to applying the topcoat. That process takes several days depending upon the temperature and humidity. Often, a full week is needed. The primer then needs to be scuff sanded to obtain the needed adhesion for the topcoat.
TYPES OF FINISHES
The interior structure of a welded tubular airframe should be painted with an anti-corrosion primer called zinc chromate. There are some other epoxy based primers that can be used but zinc chromate (while not an epoxy) is the most common treatment. Zinc chromate comes in yellow or green color. If you have ever seen the inside of an aircraft structure, like a P-51 with the panels off, those green parts are painted with zinc chromate primer. Obviously this primer needs to be applied before any covering is installed.
Fiberglass or composite parts suffer from ultra-violet breakdown if not properly protected - special primers with U.V. blockers is available for these parts.
In aircraft there really is only two choices of types of paint to use. Either enamel or epoxy. Lacquer just does not seem to handle the chemicals and fades too quickly.
Enamel is much cheaper and less hazardous than epoxy (polyurethane) paints. Problems with enamels are: Enamel is fairly brittle and does not flex much. This can cause paint to chip or crack even when plasticizers are added to make the paint more flexible. Enamels fade and oxidizes after some time even when stored indoors. Enamels will also breakdown when in contact with certain chemicals.
Polyurethane paints are flexible, strong and resistant to almost all chemicals and have a nice shiny look A clear coat is not needed but can add a greater degree of depth to the paint and added protection but is not required to get the paint to shine. It is also expensive and more hazardous to work with than enamel.
It is possible to use an enamel under and then put put on a coat of polyurethane clear coat for added protection and that super shine. Test if you use different paint manufacturers for compatability. When a paint brand is decided on stay with that specific manufacturers brands of primers, reducers, and so on. Paint is very much a chemical action and the paint companies spend a lot on research and development.
Flexible structures such as composite or fabric covered aircraft can also benefit from the flexibility of polyurethane. If adequately taken care of these paints can last through your lifetime.
Acrylic Lacquer not recommended
This paint has a low solid content that makes it more difficult to apply. Acrylic lacquer should be thinned using the proper thinner and then a very light tack coat applied. An additional 4-5 cross coats of paint will then have to be applied allowing about 30 minutes drying time between coats. (By the way, a cross-coat is defined as moving the spray gun north and south followed by east and west: one cross coat).
Lacquer is somewhat like dope in that it dries fast. So fast, in fact, that the bugs in the area have to be on standby alert in order to zoom in quickly if they hope to land on a wet surface. This makes it a good choice for those painting outdoors.
Unlike dope, lacquer becomes very hard and brittle when completely cured and will crack and chip, particularly on sharp edges and corners. You should not use this paint on flexible or fabric surfaces.
On the other hand, lacquer is more versatile than dope and it can be used on most any type of solid surface (aluminum, steel, wood, composite, etc.). It is a very economical type of finish and is easy to apply. Like dope, you can touch it up and spot areas without repainting the whole component.
Lacquer's quick-dry characteristic can turn into a disadvantage if you aren't careful when spraying. Your paint application must go on wet or it won't adhere very well and the resulting surface will feel rough and fuzzy under your hand. If this happens, sand off the roughness and try again.
Acrylic lacquers have low solids content and they cover rather poorly. Five or six coats of lacquer must be applied. Fortunately, all of these can be applied in a single spraying session if you allow about 5 minutes between coats to permit the paint to "flash oft". There is virtually no wait between coats for larger components because it will take you that long to spray from one end to the other.
There is one more thing you should know about lacquer. A lacquer finish has to be compounded, or rubbed, to improve its gloss. This, however, should be delayed until the next day after an overnight dry.
As a rule, you should never attempt to paint over an enamel finish with lacquer unless you first apply the appropriate sealant recommended for the brand of paint in question. A fresh coat of lacquer will generally cause an underlying enamel surface to curdle and pucker. Ordinarily, there is never any difficulty in applying an enamel topcoat over a lacquered surface..
Enamel is an older style of paint that was commonly used on aircraft surfaces. These paints are sprayed over epoxy primer after being thinned to proper consistency using enamel thinners. A light, mist coat is first sprayed on and allowed to dry for a few minutes until it is tacky to the touch. This is then followed by a full coat of enamel. One full coat may be sufficient or another may be sprayed if desired. The use of enamel has decrease over recent years.
Enamel is a paint with varnish in it. This explains the instant shine that is characteristic of an enameled surface. The paint dries fairly fast (dust free in 45 minutes, about half that time for acrylic enamels) but is slower drying than a lacquer or Butyrate dope coating and, consequently, there is more time for dust and bugs to take refuge in the tacky surface. Painting with enamel should, therefore, be done indoors, preferably in a paint booth. It is, nevertheless, a very good paint type for use over most any kind of hard surface. It is very durable and holds up well under most conditions.
The acrylic enamels (Ditzler's DELSTAR/DuPont's CENTARI) are very popular and economical to use.
Enamels are less brittle than lacquers. Nevertheless, they are not very well suited for fabric covered surfaces. One exception might be white DUPONT DULUX enamel, provided it is applied sparingly to the fabric surfaces. The dark colors tend to be more brittle than the whites.
One of the advantages of using acrylic enamel is that the entire airplane can be painted, including the metal parts, without a lot of extra masking preparation.
As a rule, you should never attempt to paint over an enamel finish with lacquer unless you first apply the appropriate sealant recommended for the brand of paint in question. A fresh coat of lacquer will generally cause an underlying enamel surface to curdle and pucker. Ordinarily, there is never any difficulty in applying an enamel topcoat over a lacquered surface.
Epoxy primers are great but the use of epoxy as a topcoat finish may not be quite as good. Epoxy does have superior adhesion qualities and is quite durable and long lasting. However, it does have the reputation of fairing poorly in the sun, and is prone to oxidizing . . . chalking.
Epoxy should not, ordinarily, be used over zinc chromate as there is sometimes an adhesion problem in doing so. Use an epoxy primer under epoxy topcoats.
Catalyzed epoxy is rather slow drying (2 to 6 hours) so you may wish to speed up the drying process. You can do this by mixing the epoxy with its catalyst and setting it aside for one-half of its pot life. Then stir it thoroughly and spray it on. The epoxy coating will then cure in half the usual time. This is still slow by dope, lacquer and acrylic enamel parameters.
Being a slow drying paint, it is very difficult to get a dust-free and bug-free finish unless you paint indoors in a well ventilated paint booth.
*Polyurethane Paint best
Polyurethane enemal (Imron, Durethane, Etc.)
That "wet look" so typical of polyurethane enamel finishes has really captured the fancy of the aviation community, amateur builders included.
And is therefore, probably the most popular choice for a topcoat today. It is very durable and provides a high gloss finish. It is also chemically resistant. These paints have a high solid content and they cure very slowly which means they continue to flow out for a long period of time. This flowing out or settling process forms a very flat surface that gives the surface a high gloss look. Polyurethane enamels are mixed with a catalyst prior to use. They are then reduced to proper viscosity for spraying. A very light tack coat is first applied followed by one or two full coats. One problem inherent in polyurethanes is the thickness of the film applied. If the paint is applied too thick it may tend to crack over a period of time.
Cracking is especially true when applied over fabric. The fabric on an airplane will flex and move during flight. This movement coupled with the thickness of polyurethane paint can present a problem. Polyurethane paints designed for fabric airplanes are manufactured and should be used when painting over polyester fabrics.
The one major problem encountered when using polyurethane paints is its toxicity. Breathing the spray mist from polyurethanes may cause severe sickness. With this in mind, you must use the correct safety equipment. You should also protect your skin and eyes.
These polyurethane paints adhere well to most surfaces. They provide a hard surface finish that is outstanding in gloss retention, resistance to chemicals, fuels and oils, and is flexible enough to exhibit superior chip resistance . . . and, oh yes, this super paint is expensive to use.
This type of paint requires the addition of an activator. Once mixed, however, application is as simple as spraying enamel or lacquer.
Being a rather slow drying paint (about 45 minutes to a dust free cure and 4 to 6 hours for a tape free dry) it is best that your painting be done indoors in some sort of well ventilated booth or enclosure.
Polyurethane enamels are being used on just about every type of aircraft surface. As for fabric covered surfaces, although DuPont (maker of Imron) may not be ready to claim that Imron is suitable for use on fabric surfaces, that doesn't bother some homebuilders. Amateur builders are using Imron on fabric covered airplanes with eye-catching results. Only time will tell how well the finish holds up on those flexible surfaces. So far, the performance of the paint is outstanding. These are professional finishes and require proper protective gear.
Painting a fabric airplane, you can use a specially designed polyurethane topcoat, butyrate dope, or Poly-Tone. Butyrate dope and Poly-Fiber's Poly-Tone are both very easy to apply because they are more viscous. Therefore, they are less likely to run when applied.
AIR CRAFT DOPE
Today's high-tech wet-look paints just don't look right on classic airplanes. They are still using dope on fabric for real vintage plane restorations. Those grand old flying machines had satin-smooth finishes that looked deep without the candy coating look on it. The secret to those finishes was the cellulose dope. You can get dope, etc. from aircraft supply companies.
COOPER, DITZLER, DUPONT, RANDOLPH and STITS.
Classic Aero dopes are made right here in America by Poly-Fiber. Our only business is making outstanding aircraft coatings. Classic Aero is kind to the environment and has been exhaustively tested both on the ground and in the air. Aircraft dope is a plasticised lacquer that is applied to fabric-coated aircraft. It tautens and stiffens fabric stretched over airframes and adheres and protects fabric applied to other skin material.
Butyrate Dope Finishes
Everyone knows that dope is used for fabric surfaces. What everyone doesn't know, however, is that dope cannot be used over metal surfaces because it will surely peel off. It is not suited for use on slick composite surfaces for the same reason.
Since all fabric covered airplanes have quite a few metal parts and surfaces, in addition to their fabric covered components, you will have to switch to some other type of paint for the metal work. Color match and sheen is an artform and takes practice.
One nice thing about using dope is that it can be easily touched up, patched and blended without repainting the entire unit . . . something you can't do as successfully with enamel.
Because dope dries fast it can be sprayed out-of-doors without the benefit of a paint booth . . . provided a little extra care is exercised in selecting the best conditions for the paint job (early morning hours, no wind, low humidity and warm temperature). Dope is humidity-sensitive and you should not spray it when the humidity is over 65% (best temperatures are between 65 and 80 degrees F).
Dope doesn't cover as well as many other types of paint and, as a result, you have to be prepared to apply numerous coats of dope to equal the coverage obtained with only a couple of coats of, say, acrylic enamel on other types of surfaces.
In short, doped surfaces can be work intensive. They require, first of all, a brush coat of Nitrate dope followed by two or more coats of Butyrate dope, and then a couple more coats of pigmented aluminum dope. All this is followed by three or more color coats of Butyrate. Of course, a lot of different coats spells a lot of work, a lot of wet sanding in between and a lot of rubbing. This means spraying your dope will cup down on application time tremendously. The STITS process using Polybrush and Polyspray is somewhat different and a lot simpler to use. Nevertheless, either product is still the best paint type to use on fabric covered surfaces, be they grade A fabric, linen or one of the Polyfiber fabrics. The finish will remain quite flexible throughout the years of service and is less likely, by far, to crack from embrittlement than when finished with any other type of paint currently available.
The most important aspect of painting is Practice. Do not practice on your airplane. Get several pieces of cardboard or other scraps and learn how to properly set up the spray gun. Spray pieces of metal lying flat on a surface. Then spray the metal pieces hanging vertically. When you feel really confident, a test of your mastery is to paint something odd shaped. Buy a piece of stovepipe or a large diameter pvc pipe and paint it. Stand it vertically and paint the entire piece. When you can do this without major mistakes you are ready to begin on your airplane. If possible, always begin the painting process with a small control surface.
Follow the Fundamentals. Paint needs to be properly mixed. Take it to the store and shake it within one week of application. After shaking the paint it should then be thoroughly stirred just prior to use. Secondly, the surfaces should be wiped down with a paint cleaning solvent using a clean rag. Then a tack rag is also sold at any store and should be used to remove any dust. Thirdly, the paint should be properly thinned by following the manufacturers directions. A viscosity cup can be used for the thinning procedure. Slight differences in color can often be found in different batches of paint. One solution is to open all of the cans of paint you will be using and mix them together in a large container. They can then be poured back into the original containers after being mixed.
Mixing the catalyst in polyurethane paints should be done in accordance with the directions from the manufacturer. Usually, you should let the catalyst react with the base paint for at least 20 minutes prior to spraying. Once you have mixed the paint you will have approximately 5 hours before the chemical crosslinking begins and the mixture begins to thicken. With that in mind, only mix the amount of paint you will need for the job. If you mixed too much paint you can place it in a freezer (never food) overnight, remove it and allow it to reach room temperature before spraying. The cold temperature delays curing processes.
The actual adjustment of a spray gun depends upon the equipment you are using. The manufacturer may provide you with a set of instructionsn or email us at firstname.lastname@example.org. You should use the type of spray gun nozzle recommended for the type of paint you will be spraying. There are general guidelines on our spray gun page that fit most applications. The gun should be properly adjusted each time you spray. A test pattern should always be sprayed on a piece of cardboard before beginning to paint. The normal pattern for a spray gun will be fan shaped. To begin the actual application procedure, hold the spray gun approximately 4-6 inches from the surface for HVLP, 6-8 for Reduced Pressure. The spray gun should be far enough away so the paint does not run or sag when applied and close enough to lay on a wet coat. To prevent the paint from being uneven, it is imperative that the gun be held exactly perpendicular to the surface in a side to side motion. If it is tilted the paint will be heavier on one side and lighter on the other. The spray gun should then be moved parallel to the surface only the distance you can comfortably move your entire arm while keeping the movement exactly parallel. If the gun is moved in an arc back and forth the material will be applied heavier in some places and lighter in others. You should squeeze the trigger of the gun just prior to beginning the paint stroke and release it just before it is completed. You then should move up or down approximately fan width and begin the next pass. You must overlap the passes to achieve an even build-up. Each pass of the gun will usually apply the paint more thick in the middle with a tapering off on each end. Remember our definition of a cross-coat, one pass north and south followed by a pass east and west. If at all possible, paint on a flat surface. Of course, that is not always feasible. Paint will sag or run much more easily on a vertical surface. Spraying in corners and around corners presents a problem. Practice in areas such as this to establish the proper technique. As a general rule, spray the corner first whether it is inside or outside then you can blend the paint in with subsequent strokes.
It is much easier to paint your airplane prior to assembling it. But many builders will assemble their airplane, test fly it, and then paint it. If you do paint your airplane assembled follow this pattern. First, you will want to paint ends and leading edges of surfaces. Paint the bottom of the airplane first by beginning at the tail. Spray from the tail control surfaces all the way up the fuselage to the engine then spray the underneath side of the wings. The trick of the entire process is to keep the surface wet all the time. It is much easier if you can persuade another painter to help you. That person can paint at the same time you are painting with one of you staying slightly ahead of the other keeping a wet edge.
After spraying the underneath side of the airplane you then should spray the vertical stabilizer, the top of the tail surfaces, the top of the fuselage, and then the top of the wings. It is more difficult to paint the airplane when it is assembled. Overspray is the problem. You must keep overspray off the surfaces you have finished. I would recommend visiting a local paint shop and watching their techniques. There are a number of ways to do this and each painter has a trick or technique. When you paint the airplane unassembled the problems are minimized.
As a rule of thumb, a white coat of paint should be applied prior to final colors. This will provide better coverage with less material and also bring out a more brilliant color in the final coats. White primer will serve this purpose. Do not try to cover red paint with a lighter color. Red should always be the last coat sprayed.