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Painting Your Homebuilt Part 1
Lessons Learned and Relearned
By Tony Bingelis (originally published in Sportplane Builder, December 1994)
If I had to paint a homebuilt before I could get to build it, I probably would never start on the project in the first place . . . figure that one out, amigo!
To me, painting an airplane is on a par with building cowlings and doing other fiberglass work . . . both efforts are messy and both stink. I would rather whittle wood and drive rivets. However, painting comes with the sport so I try to do the best I can for every project I undertake. S re, I could have somebody else paint my aircraft - and I would if I could, but I can think of several thousand reason for doing it myself (read that as "dollars").
Anyhow, it is not that I can't do a pretty good job of painting. I can, but since I don't use my spray gun for two or three years at a time, I have much to relearn. Consequently, my results, at least initially, are not always predictable and consistent. As a confidence booster, I try to convince myself that there is no such thing as a perfect paint job . . . it helps.
I realize that anyone who is picky enough can always find something to criticize in the finest paint job: a masking flaw, a small run in some corner, a pin hole or two in fiberglass parts, a slight "orange peel" appearance where least expected, or maybe a paint starved edge. Anyhow, my latest project, a little single seat RV-3, has finally been painted, and with fairly good results, I might add. This time I took plenty of time to mull over the problems I experienced during previous painting efforts.
For example, I well remember how I had to cope with the problems of spraying the airplane in the driveway, the messiness of it all, the bugs and the tiny dust particles, the masking mistakes, the consequences of over-spray, paint runs (always where they showed the most), and, yes, even
the mild elation I experienced when I managed to turn out a few perfectly sprayed components and parts.
If you intend to paint your own airplane and have never had the occasion to spray paint an airplane, a car, a boat or an automobile at some time in your life, why not go for it? Not only will you save money, you gain a real-life experience in the process. I'm sure you realize there is much more to painting an aircraft than simply selecting the paint, spray gun, reducers, masking tape and a place to perform the ritual.
You're right. There is quite a bit in the way of painting preparations and techniques the average builder never hears about. Maybe the paint manufacturers take it for granted that only professional painters paint airplanes and they already know the tricks of the trade. Unfortunately, that is not usually the case as there are many of us who restore autos, or build airplanes and boats, and determinedly elect to paint our own creations. Nevertheless, although we are amateurs many of
us are turning out some beautiful work.
So, regardless of how little you think you know about spray painting and pre-painting preparations, why not go for it? This article is based on what I have learned and what I have had to cope with every time I started to paint a newly completed airplane. It may give you a better grasp of what to expect when you plan your own painting extravaganza. After all, it is much easier to avoid most painting pit
falls when you know where and why they develop. NOTE: I generally use DuPont's Centari Acrylic Enamel on my homebuilts because it is less expensive and its fumes are less toxic than those emitted by the exotic Polyurethane "wet look" finishes. My comments are, therefore, specifically oriented to the use of acrylic enamels. Nevertheless, most of the precautions and preparations described are, I am sure, equally valid for most any kind of painting project you choose to undertake.
Let's face it. Painting an airplane at home is as bad for the environment as it is for your lungs! The culprits, of course, are the paint fumes and the overspray spewed out by the spray gun. To reduce the amount of excess paint spray that does not land directly onto the component you are painting, consider using one of those remarkable high volume low pressure (HVLP) spray units. These turbine units produce, at a very low pressure, a very high volume of heated air that operates the spray gun. This heated air coupled with the gun emits a cone-shaped spray pattern that reduces the relative humidity in the surrounding air, and the overspray as well . . . provided the wind is not blowing.
Almost a third less paint will be needed because of the greatly reduced amount of overspray. The environment, naturally, will benefit from the use of such a paint spray system as much as you will.
Even so, your assault on the environment and on your lungs is not over because after you finish using the spray gun, any kind of spray gun, you must clean it. Of course, you never set the gun aside and let paint harden in it. If you do, you'll regret it the next time you have to use that gun.
Now . . . how do you clean a spray gun? That's right . . . with copious amounts of lacquer thinner, or some other highly volatile solvent. Meanwhile, as you brush and/or spray the fluids through the gun, plenty of fumes are being turned loose in the air around you. These are the same volatile solvents you will use to clean up whatever paint spilled mess you make. Actually, you will have used several gallons of solvents by the time you complete painting the airplane. All of the leftover paints and dirty solvents remaining in the gun, and in various coffee cans on the bench, have to be disposed of. So, what do you do with all that stuff? Pour it down the drain? On the ground? If you do, that paint residue and dirty fluids will discolor and contaminate the soil where it is dumped.
A more sensible solution would be to conscientiously collect all of the waste paint and solvents in a large container - and keep it tightly capped. Then, after you have completed your painting project, haul it away to an approved disposal site . . . it is the right thing to do. If you live "out in the country," resist the temptation to pour out the leftover paint and solvents on the ground in some private dump site. Think twice - that stuff will permeate the soil and may even get into the underground water supply.
Think About Your Hands
I say again, painting is a messy operation. No matter how careful you think you will be, that hard-to-remove paint will get on your hands and under your fingernails. That's bad enough but the solvents will also penetrate and dry out your skin. Without any protection, your hands quickly become so paint stained that no amount of scrubbing will get the paint off for several days . . . a social disgrace, indeed.
Although you may consider using vinyl or rubber gloves awkward and inconvenient, they will help keep your hands clean. Unfortunately, these protective gloves don't last very long when you handle paint reducers, lacquer thinners and similar volatile solvents because they quickly dissolve and eat away the glove finger tips.
One skin protective product I've used time and again to keep my hands clean is Invisible Gloves #1211, a water soluble hypoallergenic pomade. I rub it into my hands BEFORE I even think of touching a paint can. Since the pomade is water soluble, you must resist wiping a perspiring forehead with your hands or getting your hands wet, because the moisture will dissolve and ruin the protective coating.
Although MEK, zinc chromate, epoxy, and aviation gasoline won't penetrate the protective barrier on my hands, water will. I am always surprised how easily paint smeared hands cleanup with soap and water. Resist the temptation to clean your hands with lacquer thinner, or MEK, as they are harmful to your skin. The fumes aren't so good for you, either.
Workbench Surfaces Get Messy, Too
You have to mix the paint somewhere. The workbench is an obvious first choice. It is inevitable that you will spill paint trying to pour it from the paint can into your mixing pot. Then, after the paint is mixed you will spill even more trying to fill the spray gun through a paper cone paint filter. For that matter, you may overfill the spray gun because you can't see through the paper filter, and there it goes all over the bench.
What can you do to minimize spills? Not much. Just be as careful as you can. Keep a roll of paper towels handy and use them frequently to wipe up the spills as soon as they occur. This will do much to minimize the mess of cumulative paint spills. These acrylic enamels dry fast so you better wipe up spills as soon as you can.
Before starting any paint work it will be worthwhile to spread and staple a heavy plastic sheet over the work surface area where the paint mixing is to be done. Then, whatever spills do occur will not soak into the underlying wood surface and can be easily wiped away. By the way, how many painters have you seen wearing a respirator while they were mixing paint? Those fumes, you know, are no less toxic than the fumes given off while spraying.
You Are Going To Paint It . . . Where?
In the driveway most likely. However, you will learn quickly that you are taking a chance when you decide to paint your airplane in the driveway. Painting under trees is even chancier because you will have to cope with falling leaves and buds, bugs and strafing birds, as well as airborne dust particles. Such a decision means, at the very least, you will need to erect some kind of overhead cover . . . say, a temporary plastic roof spanning your work area. The plastic cover can be stapled to a simple wood frame or you might consider making the structure with PVC pipes, T-sections, elbows and flanges. In that case, the plastic would have to be taped to the pipe. Fortunately, both duct tape and masking tape stick tenaciously to the plastic sheet so don't worry about adding staples or other fasteners. Consider the effect these prospects could have on your work:
1. Should you have a day or two when it rains, that plastic roof will fill with water and may even collapse the light frame.
2. Strong winds might blow it away.
3. A plastic roof won't keep the dust away from whatever you are painting.
Oh, well, you can't paint when it is windy or raining, anyway. The ideal setup, of course, is a completely enclosed plastic shelter with filtered air inlets and effective suction fan outlets. Such a temporary enclosure could be set up inside the workshop (garage), or just outside the door in the driveway. It means extra work and expense but it might be worth it under some climatic conditions.
To thwart bugs and flying insects, plan to paint only during the early morning hours. There will be little or no wind (usually) and the humidity will be higher providing a potentially dust-free few hours. To this end, I usually turn on the lawn sprinkler system and, also, wet down the driveway.
A word of caution, however. If you are doping an airplane with a regular spray gun, realize that dope does not take kindly to a high humidity (65% or higher) and the doped surfaces could blush. A high humidity, on the other hand, is not a problem when using a HVLP gun as the turbine heats and dries the air passing through the spray gun. Incidentally, avoid spraying any component that is in the direct sunlight as its abnormally heated surfaces will affect the paint behavior and paint flow-out.
Overspray, a Serious Problem
Spraying your airplane under the plastic roof of that makeshift driveway shelter has other ramifications. The paint overspray will easily carry 50 feet or more. Any object within that distance will receive a barely visible mist coating from the airborne paint. This includes nearby autos, bicycles, boats and shrubbery, too.
Protect Everything You Don't Want Painted!
Protect the floor/driveway pavement beneath the components you will be painting. If you don't, the ground will gradually assume the same hue as your airplane. Plastic sheets spread over the ground (pavement or floor) where needed, although unsightly, are effective. Always keep in mind the awareness that while you are concentrating on the component being painted the overspray, in the air all around you, is settling on everything nearby.
Even more devastating, the components or parts you have already painted and put aside may now be gathering some of the overspray, too. Consider this as an important precaution. As soon as you have painted a part, remove it from the area if you intend to continue painting other parts. Anything nearby that you don't want coated with that almost invisible overspray must be draped with protective plastic sheets. But be absolutely sure the parts you cover with plastic sheets are completely dried or the plastic covering may stick to the finish.
Look At Your Shoes, Man!
You may not realize it but your shoes will also surely become victims to overspray from the repeated use of the spray gun. Select the worst pair of shoes you own and wear them every time you paint. By the time the airplane is completely painted, you won't feel so bad about getting rid of those comfortable old paint speckled beauties.