PAINT ON MY AIRPLANE?
By: Charles Threewit
Published: July, 2002 Custom Planes Magazine®
Today’s modern latex paints are miracles of chemistry.
Someone queried the members of the EAA on their web site about using latex paint on aircraft, and the responses were interesting. Some people had used it. One gentleman said he was 72 years old and had been in aviation for 55 years. He thought these facts gave the knowledge to predict dire results from its use.
His attitude, and that of the other nay Sayers, reminds me of when the Wright brothers’ father, a few days before their historic escapade at Kill Devil Hills, emphatically said to the press that “If God had wanted men to fly, he’d have given them feathers!” Or it’s similar to the sagacity of the long-departed IBM CEO, who said, in the late 1970s that “As near as I can calculate, there will be a worldwide market for a total of about five home computers.”
Actually, the following are several good reasons to give serious consideration to the use of latex paint on fabric-covered aircraft:
*A low cost of about $20 a gallon, compared to several hundred dollars per gallon for more exotic paints
*Ease of application and total lack of toxicity
*Its tenacious hold on fabric fibers
*Its resistance to UV damage
*An infinite variety of colors
*The dealer’s ability of computer-match paint samples
Years ago, model aircraft builders who had an aversion to the cost of automotive-type paints discovered the usefulness of latex paint on aircraft. And, in many cases, they didn’t have the equipment or the knowledge for proper application of these exotic materials. In addition, automotive paints require expensive breathing apparatuses; in curing they give off cyanide and they’re extremely unfriendly to the environment. Many award-winning giant-scale model aircraft are finished with latex paint today, and there are several web sites devoted to the subject.
Note: To be called “giant-scale,” a model has to be at least ¼ scale or have a wingspan of al least 80 inches for a single wing or 6o inches for a biplane.
One excellent article on painting and detailing giant-scale models can be found at http://www.modelairplanenews.com/how_to/latex.asp. The author, a nationally known, award-winning modeler, has used latex to finish his planes since 1983. He had been using expensive epoxy paint, but he couldn’t match the colors on a plane he had repaired after a crash. He went to the local Benjamin Moore dealer for help and learned they could match the colors exactly-for about 1/8 the cost–by using a computerized spectrometer. After refinishing the model with Benjamin Moore latex applied over conventional automotive primer, he was surprised to discover that the newly repaired plane was now 4.5 pounds lighter than the original had been-even with all the extra material used for the repairs.
It’s interesting that the SR-71 Blackbirds on display at the Blackbird Airpark in Palmdale, California, were painted with black latex to protect them from the vicious UV content of the high-desert sun. During flight, the plane’s skin temperature approached 575 degrees F, so latex obviously wouldn’t be suitable for flight. But, it works great to protect the grounded birds from the ravages of the desert sun.
picture (above) shows all the equipment required for a basic paint job
using latex paint. In the center is the paint; I used a can of bright
red I had sitting on my shelf. To the right of the paint are a foam
roller, a couple of foam brushes and a good-quality bristle brush. To
the left of the paint is a product called Floetrol. It lowers the
viscosity and surface tension of the paint and helps it to spread more
easily, making for thinner coats and easier application.
folks who use latex on full-scale planes use a base coat of black
paint for ultraviolet protection. However, if the bare fabric is going
to be visible in the finished plane, the black color isn’t too
desirable. An interesting Web site (http://www.larryvile.com/dcd/tandem/latex1.htm)
describes the painting of a Ragwing Ultra-Piet (a ¾-scale Pietenpol
Aircamper). The author didn’t use an undercoat of black on his
Ragwing because he didn’t want the black to show in the cockpit.
Also, he says he was concerned about the weight-saving possibilities.
He said, “If I was still flying the airplane in 10 years, it would
probably be ready for new fabric anyway, I figured, UV degradation or
Paint For Your Homebuilt
This describes a painting
method, which is highly experimental in nature, and if you choose to use this
please be advised you do so at your own risk. The ONLY way to paint and finish
any airplane is with certified and proven methods.
I have experimented for 10
years using different painting methods to finish fabric on light experimentals.
The alternate finishing methods can and will hold up well given proper
application and protection from the elements. My first attempt at painting was
using Mike Fisher's latex method. It was my conclusion that this would not
provide the level of finish that I wanted to see on my airplane. In 1994 I
built and finished a Nieuport 11, (Graham Lee Design) and covered it in 1.6oz
Stitts. I used a combination of black latex primer to fill the weave of the
fabric and industrial polyurethane oil base paint for the finish. This
experience started my search for a better method. My goal was a serviceable
finish that would look good and avoid the need to spend the large amount of
money for the certified stuff!
Here is what I have come up
with and I might say it works well, looks good with a nice gloss and is very
easy on the pocket book. This finish goes on easy, and the need for elaborate
spray painting facilities is eliminated.
Seal aircraft with wood sealer if it is a wooden airplane. There is no need to finish an aluminum tube structure if it is not flown near salt water. For the RagWing Special I am building I am using 2 brush coats of MINWAX OUTDOOR CLEAR SHIELD POLYURETHANE WOOD SEALER. This material is applied unthinned but brushed on in thin coats. I use satin finish so that I may see better where I have brushed.
If you are using the STITS FABRIC (1.7oz) you can brush a thinned coat of POLY-TAC cement over the fabric gluing points. Use your Stits manual for further information on this. The cement can be thinned with MEK SOLVENT and I used about 50/50 cement/thinner. Let this dry and then the fabric can be applied and the cement under neath the fabric can be re activated by brushing 50/50 cement through the fabric at these areas. After the fabric has been applied and shrunk then the tapes that you're using for reinforcement and or rib stitching/attachment can be applied using this same glue combination. A little iron run along the rough spots will smooth them and make sure that they are attached well. I use a Modelers Heat Shrink Cover Iron for this process.
Clean the fabric with a clean cotton cloth and solution of MEK. Just dampen the cloth and wipe the fabric with it. Remember that this stuff is a strong solvent and is capable of melting the glue joints and dissolving your Polyurethane wood sealer. If you just dampen the cleaning cloth and wipe the surface of your covering job this will remove the sizing and other contaminants on the fabric. If you do not do this the paint will not adhere very well.
Using a Good Quality Tac Cloth wipe down the area to be painted BEFORE EVERY STEP!
Using EMPIRE POLYURETHANE LATEX PRIMER thinned with 30% FLOETROL LATEX PAINT CONDITIONER and a 3" FOAM PAINT BRUSH, brush the primer into the fabric using span wise strokes. This is the first coat so do not try to fill the weave completely with this first coat. If you do you will have runs inside the fabric and just in general make a big mess. Repeat this process using cross coats until the fabric weave is filled. This will take 3 to 4 coats. Be sure to let the paint dry well before each application. If you use nice even brush strokes there will be no need to sand before final paint application. The FLOETROL will help the paint flow out into the fabric and be self-leveling. It also adds flexibility to the paint. Minor brush stokes are acceptable to me but you make you own decision about sanding. Preparation is the key to a great final finish. No short cuts here.
Using ENTERPRISE GLOSS POLYURETHANE OIL BASE ENAMEL and a 4" WIDE 1" DIAMETER WHITE FOAM PAINT ROLLER roll the first coat of finish color onto the fabric. The finish will be much smoother if you put the paint on a smooth surface to apply it to the roller. I used wax paper taped to a smooth surface. Remember that you are not trying to apply the complete finish coat in one step. Roll the paint out to a nice even coat and when the paint begins to tack stop rolling. The urethane paint will self level as it begins to cure. All you are doing here is to apply the paint evenly and get most of the air bubbles out of the finish color. Time between coats will be about 24 hours depending on humidity. The finish color will take 2 to 3 coats depending upon the color you choose. You should have a very glossy finish.
After the paint has cured for at least a week, clean the painted surface and wipe on a coat of SON OF A GUN PROTECTANT or similar to protect the paint and give the surface some UV protection. I clean my paint job often and keep a coat of this protectant on at all times.
The paint samples that I have
done over the years have spent their entire time out door in all kinds of
weather in the state of Indiana. This system seems to hold up well and still
look good after all of this abuse. Please do your own samples and satisfy your
self as to your technique and results. Best of luck and happy aviating.
For further information
contact Jerry Bunner
CLEAR SHIELD POLYURETHANE WOOD SEALER
BRAND LATEX PRIMER IN WHITE
BRAND LATEX PAINT CONDITIONER
BRAND POLYURETHANE OIL BASED ENAMEL
WHITE FOAM PAINT ROLLERS
Ultraviolet Absorption of Latex Paints by Kirk Huizenga
THE FLYER FAMILY FLIER
Using Residential Latex Paint for Aircraft Finishing
by Sid Hausding March 2001
Let me start by saying that although this procedure may resemble others that have been out for some time, this method is mine alone. I am responsible for the products chosen and the various methods Inside this issue: and applications described. I understand Fisher may be using all latex, and the Brunner method finishes with an epoxy paint over the latex primer. Many will not agree with my trial and error attempts and many Using Latex Paint may wish to provide better and more experienced philosophy and input. Everything can be improved. I am only describing my covering technique and painting methods as applied to one, privately owned and built aircraft…...mine! I have had my finished project application investigated and looked at by several homebuilders with experience, and by licensed A&P mechanics with lots of repair work behind them. Evaluations were good and the job judged to be just fine. Remember, this is low and slow here, certainly not rocket science with its requirements.
I started searching for a more economical painting application soon after investigating and settling on one design of a kit airplane to buy, build, and eventually fly. All covering techniques and painting methods as applied to the airplane industry were carefully researched and the prices used for the base material and square footage requirements for the size aircraft to be covered were analyzed and found to be out of reach......they all were way too excessive in price for my experiences in painting and weatherproofing projects, and I couldn't understand why the color red was more expensive than others! Except red might be popular, too popular.
I am a carpenter and home remodeling laborer with some combined 30 years bending nails and finishing out residential and commercial buildings. The advent of water based latex paint was a godsend for speed, ease of application and clean-up, not to mention the great price. I have enough experience with this paint to believe in it and to have seen the good results brought forth with the correct preparation, application, and understanding of its limitations. It is not bullet proof, and just like everything else you need to understand how to apply, care for, and what it can do and can't do. I do not consider myself an expert in the latex paint mixtures and techniques of its application, just experienced!
My plane project is a rag and tube, high wing, side by side, with some bare aluminum, and some fiberglass surfaces. This article is on covering the cloth only, but the paint and applications will readily apply to both the other surfaces also, with slightly different base (primer) coatings.
I used a spare 4130 tube, door frame at first, to play with, and to check the various latex primers I had on the shop shelf left over from several carpentry jobs this year. By shrinking some ceconite over the frame I had a surface just like the rest of the plane.
I wound up using Wal-Mart's $10.47 per gallon, Color Place primer (8095 white). Only because is was the right price per gallon, and I intended to add Flotrol to thin and induce a better saturation of the cloth and weave. The mixing directions were adhered to as followed off the container, and I only needed one gallon of the paint. I didn't think I needed any high priced value here, because primer to me is pretty much primer, and this is their 'best' anyway! It certainly seemed to work great. It satisfied my tests on the cloth covered door frame.
I generously applied two coats with the Flotrol mixture using a four inch (4") foam roller and some brushes where the roller wouldn't fit onto the surface(s) due to size, or space of the surface(s) being painted -lifting handles, tight curves, gear mounting, small round tubes, etc.. There was a difference in the texture when dried. The roller left a 'fairly' smooth and consistent skin like surface, and the brush usually left brush stroke ridges evident to my eye, even with the Flotrol. This stuff (latex paints) dries pretty quickly with warm, dry air in the shop, so the coatings were applied back to back on two separate days. No problems were encountered, but be sure you thoroughly mix the Flotrol initially and continue to mix and stir the supply as you go. I saw some 'sweating', or moisture bubbles on the surface now and then, but they evaporated, melted in, and disappeared. When done with each coating, I merely wrapped the foam roller with a sandwich bag and placed it in the refrigerator for convenience and to eliminate the tedious and unnecessary cleaning of the roller.
The Flotrol seemed to thin out the paint too much for my filler coats so I stopped using it after the primer applications. Next I purchased two gallons of Thompson's House and Trim paint ($15.94 per gallon) from Wal-Mart. The one coat 100% acrylic latex satin, high hiding white (T31005). I chose this because it says in the directions on the can cover it has UV protection included in the formula. Name brands were not a consideration here, just price and product labeling.
I used this full strength, after mixing well. I merely poured it into the roller pan, and using the same 4" inch rollers, applied the paint to all surfaces with different directional rolling as I went (helter-skelter). I know some techniques say to do each coat in different directions, well I did mine in all different directions as I went each time. I applied two and three coats until I was satisfied I had hidden some of the features and mistakes of my covering and gluing. Make no mistake here. The paint WONT cover and hide much, and not any major mistakes will be hidden or covered if they are there in the gluing and Dacron covering process. I lightly sanded all the joints, seams, and edges of the tapes with #150 grit, and tested for smoothness. I would wipe my hands over and discover a roughness, some raised threads or curled edges, or dust and lint that had settled into the paint surface. If you sand before the coat really dries out well, you can speed the sanding quite quickly because it will rub up and roll into little pills and elongated 'boogers' with only a little dust. It does goo up the paper, the black oxides (wet or dry types) work best, but I just threw away the used and kept using little four inch squares because it fit my hands well. I think I only cut up and used three or four sheets at $0.85 cents apiece. Where I found any holes, or indentions and imperfections that didn't leave a flat surface that the paint would cover and leave a smooth coating, I squirted a little water soluble, paintable latex caulk. Usually a wet finger tip and smoothing was all that was necessary to blend in the patch and with some paint, presto, instant smooth surface (non-structural). This was for little areas and spots only, of course.
I tried hanging up the flat control surfaces and spraying the paint, but the thickness of the paint was too hard to control and sagging resulted with a most humbling effect on my ego. I was startled to see my perfect spray job sagging into a wet, sticky mess on the bottom edges as well as big runs along any area I had really 'stuck it to' an hour earlier. I used dampened cloths to actually wipe (some rubbing required depending on how quickly I discovered the sags/runs) out the sags and paint, down to the primer, and in some cases back to the cloth. It worked quite well and even allowed me to 'feather' the edges of the messed up areas for later sanding and blending of the repair painting. This set me back several days while this all dried and I carefully built up coats of the primer and satin coatings to try to match the good areas.....lesson learned here was to lay everything as flat as possible and roll or spray.
Now I realize I have suddenly mentioned spraying too. Well, along about the second or third coat of satin 'filler' I realized the finish wasn't getting as smooth (glassy) as I had thought I would like, so I decided to haul out my $100.00 Wagner airless, large project home sprayer. At this point I moved everything back against the walls and taped and stapled painter's plastic (a thin, filmy plastic -drop cloth and over-spray protection) over the work benches and storage shelves around the garage I am using for my hangar. Its a large single area, so I could spread my working surfaces out and had lots of room to paint several pieces at one time.
I have not mentioned any overall project sanding because I didn't do any. Yes, you certainly could sand everything down in between coatings and really bust your butt. I chose to leave it as it built up knowing the latex doesn't need scuffing or have any adhesion problems to itself. I did, as mentioned, look for high spots, specks, or tape edges that raised up or curled - and sanded them quite liberally. I even broke through and cut into the cloth at a few points over hard surfaces or corners, but with some judicial touch up with the paint, and more lighter sanding here, was able to smooth over and blend in any mistakes or problem areas with this easy to use and fairly thick coat material (the latex paint).
I have used this small hand held gun and my commercial duty airless very successfully before and thought, what the hell! I now made sure my wings, tail surfaces, and the side of the fuselage I would be painting was level and used the Wagner sprayer with great success. It did have a propensity to drip after spraying continuously for several minutes, but I carried a damp cloth at all times to wipe the nozzle and tip areas. For the drips that did make it onto my work surfaces a quick swipe with a small brush, kept handy for just this occasion or for little areas, usually allowed the touched up spot to blend in and disappear. The ease with which the latex cleans up after you are done is amazing if you can compare to enamel, or worse, epoxy paints. And its not really toxic, unless you really close off the area you are painting in and shoot a lot of over-spray. I would use a cheap face mask, or as I do, a bandana over the nose and tied behind the neck, ala the masked avenger! Shoot what you need, and exit the area for an hour to let everything settle and keep the dust down while the surface sets up. Good time to take everything into the kitchen and clean the equipment in the sink! Warm, dry, clean, and near the refrigerator!
I purchased two (2) gallons of Ace interior/exterior Royal Hi Gloss Latex Enamel (102A100 high-hiding white [Ace 16664]), on sale, for about $18.00 dollars apiece. My local Ace outlet has a very good looking and friendly paint lady, Denise, and I wanted to impress her with my high finances. This is "washable and durable, acrylic latex, mildew resistant". All the things you would want for your homebuilt project! :-)
Okay, here I went with the sprayer recommendations about flow ability and spraying of thicker solutions. Although the sprayer is supposed to handle the thicker coatings, I added some water (just tap), and mixed very well before proceeding (probably a one to ten ratio, or less) to assist the suction of the little handheld gun from the attached, quart sized, paint container. It worked just fine.
Now, here is where you must practice and learn as you go. The spraying can be quite heavy now, with two or three slow passes over the same area being covered, because your surfaces are level and you want to fill in and hide some of the flaws. Be careful shooting near or on the edges because these areas could run or sag. Most everything is going to be flipped over, so I rightly figured the edges and ends would be getting lots of paint eventually. And they did. By making it heavy now you will achieve the smooth and glassy look that the higher priced painting jobs attain. It can be done. And if one coat isn't to your liking, just let it dry and give it another. My rule of thumb was shoot early in the morning, and then maybe after dinner (eight to ten hours later) so it could dry overnight. Some times it was once per day, and if it rained, I would wait longer for the humidity to return to normal. I do have electric heat available in the hangar (her garage), and used it several times to speed the drying process. The build up of layers and weight really wasn't a consideration here. I only had two thinned primer coats, three filler coatings, and now two or three finish sprayed on coats to achieve a fairly nice finish. How much can a gallon of paint weigh after the liquid medium evaporates? I don't know, but it can't be too bad.
If you will wait for several days at room temperature, the final finish will harden enough to touch and work with so you can assemble the parts without finger prints and smudges in the paint. The added bonus is that you can touch up any mistakes, or boo boos from the assembly process, with a little brush and some full strength latex paint later. I inadvertently dropped one wing tip (see "ground loop in my garage", Avid forum) and was pleasantly surprised to find during the repairs on the tip, the painted surfaces glued up and mated with my Superflite Superbond (it contains acetone) just as good as new. Shrunk down, coated, primed, and painted, it blended in just fine for me. A better finish will be sanded out and painted over to match as closely as possible later.
As you may have noticed I used all white here. No particular reason, except my wing upper surfaces are also the wing tank surfaces too. Meaning if I painted them in a darker color I felt they may draw too much thermal energy from the direct sunlight and cause the fuel to expand in excess. Then leaking, spilling, and evaporation and condensation within the tank itself may be a problem. I realize this article may raise more questions that it answers, but right now the finish is looking good, and a lot of money was saved and labor reduced. My plane has folding wings, a trailer, and several garages and hangars to put it in on a regular basis. I do believe this finish will last a long time.
I now have an all gloss white project ready to add graphics or color designs right over the final coating. Maybe I will do that soon, maybe not. But with the newer rubberized stick on numbers and graphics choices, it should be as easy as painting with………, latex...........!
It’s a Beauty! This picture doesn’t do Sid’s paint job justice! Sid lives in Michigan and he would be glad to share his experiences and comments with you. If you’d like to contact Sid just drop me a note by email or regular mail and I will send you his address. It’ll give him something to do besides shovel snow!
Painting aircraft with latex paint
Part 1: Latex UV resistance, pros & cons
In the spring of 1995 I completed this Ragwing Ultra-Piet (3/4 scale Pietenpol Aircamper) ultralight, using Sherwin-Williams Acrylic Latex over bare Stits Polyfiber fabric. I've received a lot of requests over the years for information on my experiences with the relatively new "latex process," so what follows is what I know from my experience painting and maintaining one airplane. I hope these pages are helpful to you.
Latex paint is very flexible, and therefore well suited for use on unsupported fabric surfaces that will inevitably see flexure in normal flight service. You can wad a piece of latex-painted fabric into a tight ball, and then lay it out flat without seeing any cracks in the paint (I've done it -- it's very convincing). Latex is also very user-friendly, locally available, and dirt cheap compared to "real aircraft paint" (should easily cost hundreds of dollars less to paint an entire airplane).
It is generally recommended to apply some sort of UV barrier below the color coats, and most builders that use latex seem to comply. The most common approach seems to be initial coats of flat black latex, thick enough so that direct light does not pass through it. Then the color coats are applied over the black. Makes the innards of the airplane kinda ugly, I hear. I opted to not add a UV barrier for two reasons. One, I could tell that my Ultra-Piet was already in danger of exceeding the Part 103 weight limit and I wanted to keep the paint job as light as possible (later found to be a very wise move). Two, I didn't feel that a UV barrier was really necessary. If I was still flying the airplane in 10 years, it would probably be ready for new fabric anyway, I figured, UV degradation or no.
To test my theory, I decided to subject a sample of latex-painted fabric to an accelerated aging test, something much harsher than it would see on a hangared (UV-sheltered, for the most part) airplane. So I made a simple wood frame, attached a scrap of the Stits fabric with Poly-Tac around the edges and heat-tautened it. I cut a patch with pinking shears, glued it to the fabric, and cut a square hole through both layers to represent actual patches in the Aircamper around the cables and struts that protrude through the fabric (leaving the fabric unsupported around the hole except for the patch).
Here's an "after" picture (sorry, I failed to take a "before" picture.) In the upper right corner you can see one brushed layer of red latex (wish I would have added a second coat of red). The balance of the sample was brushed with white latex -- one coat over the entire surface and a second coat in the lower left quadrant. (The stains at lower left demonstrate the effects of canine urine on latex paint -- I told you this was going to be a harsh test!)
This panel was leaned outdoors, against my shop, for the next 6 1/2 years, facing south in direct sunlight and directly exposed to the elements. I just brought it inside a couple of weeks ago as it is only now clearly non-airworthy. Every few months I would inspect the panel and try to poke a hole in it by digging in hard with a fingernail. Somewhere around the 6th year, I heard the fabric crinkling during the fingernail test*, although I was unable to repeat this later. Up to this point, I would have flown the material, but now I had to concede some doubt. (*I now think this was the paint cracking at the edge where the fabric was being stretched tight over a corner of the wood frame, and not the fabric itself tearing. I know how to duplicate this sound now, and it seems to be paint-related, not fabric-related.)
Today, after 6 1/2 years, my thumb went through the material during the fingernail test (you can see the new hole in the upper right corner). It should be noted, however, that the material failed in an area that had only received one coat of paint. At this time I cannot get the material to fail in the area with two coats of white paint, even while forcing a thumbnail in with assistance from the other hand. This suggests to me** that it is possible for Stits-type fabric with two or more coats of latex paint (with no other UV barrier) to be left directly in the elements for six years and still be airworthy. (I plead ignorance of how an official fabric-testing instrument would compare to my fingernail test. I'd guess that a real fabric tester might be a bit too pessimistic for lightly-loaded ultralight use, though.) White paint is probably the worst case, too. The darker -- or more opaque --the paint is, the better a UV barrier it will be, and the longer the fabric should be protected from UV degradation. (**Paranoid note to litigious society: I am speaking only for myself, and do not recommend that anyone actually trust their life to fabric and/or paint under the conditions mentioned here!)
This is a close-up of some "ringworm" cracks in the paint. This only occured in the area with two coats, and I can't say exactly when it happened. I'd guess this appeared somewhere around 4-5 years after the test started. I'd also venture a guess that the panel was about -10°F at the time the cracks were formed, and perhaps it was struck by hail,an icycle, or a dog! Despite some cracking, the paint overall still has excellent purchase on the fabric and will not peel or flake off. When the paint is applied in a manner that allows it to soak into the fibers properly (see Part 2), this seems to produce an excellent and long-lasting mechanical bond.
Here is the patch and hole. The edge of the hole is still in excellent condition, but on the left side of the patch you can see the Poly-Tac bond between the fabric and the patch has failed from the outer edge to the hole. The bond is quite intact elsewhere, though, so perhaps my bond wasn't executed as evenly as it should have been.
One weakness of latex that I noticed is a slight sensitivity to gasoline. Spilled gasoline should be wiped off pronto, as it can soften and swell the paint slightly. This swelling seems to go away given time, but it can leave a slightly visible scar or discoloration.
I followed Roger Mann's advice (designer of the Ragwing Ultra-Piet) and applied Armor All to the paint once or twice a year. Roger says that Armor All contains a UV barrier, and it also restores a nice sheen to the paint. I did this 6-8 times to the Aircamper over the years, and the effects on the paint seemed to be nothing but positive.
Another weakness of latex paint seems to be in its resistance to bird droppings. I'm no chemist or biologist, but bird droppings seem to be quite acidic and they will etch their way partially into the paint. Sometimes they'll wash off and leave no trace, other times you'll end up with a lightly-etched reminder of a truly ugly wad of avian excrement that resembled blackberries and cream gone bad. Nasty stuff. But I think the worst scars the airplane incurred were from bird eggs tossed thoughtlessly out of a nest in the hangar's rafters. The goo that ran out of the shells got into the paint big-time and was very difficult to soften and remove.
I never had occasion to repair any latex-painted fabric, so I can't comment on that. But this is mentioned in "Maximum Paint Job, Minimum Cost," a 12/01 Kitplanes article by Kay Fellows about using latex paint on aircraft. Fellows writes, "If you get a hole in the fabric, simply cut a piece of cloth athletic tape with pinking shears. Fit it over the affected area, get out the trusty brush and house paint, and daub it over the tape. This process takes about 10 minutes and gives you more time to fly." I have to question this suggestion, though, as my experience with athletic tape is that it is low in tack. I'd be more interested to know the results of sanding the old paint around the hole and attaching a Polyfiber patch with Poly-Tac. If the Poly-Tac doesn't react negatively or bond poorly with the latex paint, that should create a much stronger patch.
Fellows seems to agree with me on fabric life in general: "As we all know, after 1000 hours or 10 years, you should recover your plane and give it a good once over. I would rather pull the fabric off my plane knowing it only cost $200 than if it cost $1000."
I've concluded that for a low-cost and low-hassle homebuilt airplane, latex paint is an excellent alternative to the high-dollar aircraft paint systems out there. It may not give you a grand champion award at Oshkosh, but properly applied it looks nice enough to satisfy even me. I further conclude that a UV barrier is not worth the cost, hassle, or weight on a hangared airplane (especially on an ultralight). My gut feeling is that a latex-painted airplane that spends most of its life shielded from direct UV rays (under a roof) will remain airworthy and attractive for at least 10 years, and for the money, that's good enough for me.
2, I'll describe how I actually applied the latex paint to the