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  The following is from edited articles of mine which appeared in the April '82 and September'84 RCM and is brought up-to-date as new information becomes available.

  In the twenty years of selling my -.6 ounce glass cloth to modelers all over the US and the world, and during frequent trips to fly in scale contests and fly-ins, I have received many questions on the covering techniques using this ultra-light weight glass cloth. My technique works well for me and I'm sure will work very satisfactorily for most modelers. All the feedback I have received from customers over these many years indicates a very high level of satisfaction.

• First, I want to discuss the advantages of covering a model with our 0.6 ounce, ultra light-weight glass cloth and resin. The number one advantage is the speed, ease and lack of anxietttttty with which a model can be covered, especially where compound curves are involved. Number two is that all overlap joints disappear never to be seen again. Other important advantages are: little or no shrinking and no loosening of the covering over the life of the model; production of extremely durable, fuel proof, sealed surfaces and no "bridging across" or unwanted filletttttting as often occurs when using iron-on's or fabric and dope. (i.e. at the interface bettttttween the fuselage and the vertical stabilizer). And, this stable, sealed smooth surface is ideal for accepting any kind of paint you may wish to use.
  
  Contrary to a general feeling of many modelers who have never glassed their planes, ultra-lightweight glass cloth and resin covering is not heavy. My experience plus reports from many of our customers show that, relative to other covering metttttthods, it is as light or lighter than any metttttthod with the probable exception of the plastic iron-ons. For example, my 80 inch span de Havilland Hornetttttt twin, with 1080 square inches, a long fuselage, two large nacelles and large tail surfaces, picked up only eleven ounces from the 0.6 ounce glass cloth and two coats of thinned epoxy. Because our field elevation here in Albuquerque is 5300 feetttttt, I have always been very weight conscious. By the way, my Hornetttttt just passed 16 years of great flying and is still going strong with the original 0.6 oz. Cloth covering looking good. I want to point out that glass cloth can be used only over solid or sheetttttted surfaces, not over open structure. This is because the glass cloth cannot be shrunk tight after strettttttching over an open structure.

• There are several binders that are used to lay the glass cloth to the model's surface. The two most generally used are: epoxy resin and polyester resin. I prefer epoxy resin over polyester resin for several reasons. Epoxy shrinks much less than polyester during the cure. It is more flexible. It will cure when applied over most adhesives used in building (polyester has problems here). It does not attack the polystyrene foams, and it has little or no odor (wives will particularly appreciate this feature). Some modelers worry about the sandability of epoxy relative to polyester. My experience has been that, properly mixed and cured, epoxy sands just as well or bettttttter than polyester. See page 4 on where to easily obtain good epoxy in large quantities.
  
  Now, into my techniques for covering a model with the ultra lightweight glass cloth and epoxy resin. Of course I am using the 0.6 ounce per square yard glass cloth which I sell in 15 foot lengths. See my ad listed every month in RCM under DAN PARSONS PRODUCTS.  All surfaces of the model that are to be covered should be sanded reasonably smooth, with all dents and nicks filled and sanded.

• But before I describe the actual covering technique, I want to discuss the measuring, mixing, handling and curing of the epoxy. First, be careful to obtain an accurate mix ratio of the resin and hardener (some epoxies are quite sensitive to their proper mix formula - won't cure otherwise). In quantities of one fluid ounce or more, the volume metttttthod of measuring is OK, especially if the mix ratio is one part resin to one part hardener. In quantities smaller than one ounce, the weight metttttthod of measuring your resin and hardener is easier and more accurate. A sensitive balance scale is required. The Ohaus triple beam balance scale weighs directly from 0.1 gram up to 2610 grams (92 ounces). This is a fine instrument that I have found to be very useful in my shop for many weighing tasks.
  For the one-to-one volume mix ratio epoxy I use, the weight ratio is 85 parts of hardener to 100 parts of resin (because hardener is lighter than the resin). Thus, the hardener used equals 85% by weight, of the resin used.

  Here's the procedure I follow. First, weight the empty mixing cup then pour in the amount of resin you want. Weight the cup and the resin and then subtract the weight of the cup which gives you the weight of the resin. Then calculate the weight of the hardener to use by multiplying the weight of the resin by 0.85. Now add the weight of hardener to be used onto the Ohaus beam scale and then add the hardener to the resin in the mixing cup until the scale comes back into balance-simple, quick and accurate. Then I thoroughly mix the resin and the hardener.

  Since the epoxy will be brushed on over the cloth, the epoxy must be thinned. The thinner I use is denatured etttttthyl alcohol. Metttttthyl alcohol (metttttthanol) or denatured metttttthyl alcohol work equally well. They can be bought in paint and hardware stores where they are sold for thinning shellac or for burning in alcohol stoves. As always, observe the precautions on the container.

  I thin the epoxy with an equal volume of alcohol (1 part resin, 1 part hardener, 2 parts alcohol). This ratio is not critical and does not affect the cure, so just getttttt it approximate. Thin enough to brush down through the cloth easily without pulling the cloth. I use brushes from 1" to 3" wide, depending on the size of the surface. Ordinary paint brushes work fine, the softer the bettttttter. After use, thoroughly clean the brushes in alcohol.

  With alcohol-thinned Enviro Tex (the epoxy I use), pot time on quantities up to at least two ounces is easily two hours. So, no need to be in a big hurry. NOTE: If, during brushing the epoxy onto the cloth, you getttttt a patch where the epoxy is two thick and doesn't brush out easily, just dip your brush into a separate cup of alcohol and brush into the thickened epoxy. This will immediately "re-thin" the epoxy so it again brushes easily.
  I have had a few worried modelers call to tell me that their epoxy did not cure properly in the pot. And it is true, all the epoxies I've tried, when thinned with alcohol or acettttttone, will not cure to the proper hardness "in the pot." They remain rubbery indefinitely.
  But, when you brush the alcohol-thinned epoxy over the cloth it cures normally. The alcohol quickly evaporates and the epoxy goes right ahead and does its thing perfectly. I have tried simultaneous tests with both un-thinned and thinned epoxy spread or brushed over glass cloth, then allowed to cure at room temperature and can dettttttect no difference in cure time or sandability.

  It is good to remember that at normal room temperature (around 72 degrees F) some epoxies remain tacky for as long as 12 hours. This is particularly true of Enviro-Tex. However, don't worry, at the end of 24 hours you will be in good shape

  I recommend that you not attempt curing below 60 degrees F. This would normally be a problem only during the winter months. I have had a few customers call to ask me why their epoxy was still tacky after several days. In every case it was during the winter and their shop temperature was well below 60 degrees F.

• I'll start with the bottom surface of the wing. Cut a piece of glass cloth long enough to go from the tip of the wing to at least 8 to 12 inches past the center of the wing and wide enough to provide a 1" to 2" overlap of the leading and trailing edges and tip. Lay the cloth over the dry wing surface and pull gently to remove any large and obvious wrinkles-this is not critical. Do not
   smooth the cloth with the palm of your hand as this will snag and distort the cloth.
   

  First, brush the thinned epoxy over the end of the glass cloth at the wing center section (this will "tie" it down" then just start brushing the thinned epoxy over the cloth in a span-wise direction toward the tip. Just as fast as you can brush, you will be laying the cloth down smoothly to the wing surface. (And, any small wrinkles ahead of your brush will magically disappear as the brush reaches them). After you have reached the tip (in just two or three minutes) trim the overlapping cloth along the leading edge and around the tip leaving enough to wrap around the leading edge and the tip. Our cloth will "paint" right around the leading edge and tip with no problem. I like for the cloth to go underneath and back about 1" from the leading edge and tip.

  If your trailing edges are slightly rounded, our cloth will again "paint" right around them and toughen them up considerably.

  After the epoxy has lost its tackiness (10 to 12 hours), the other half of the bottom surface of the wing is ready for covering. The center section overlap edge of the cloth should be smoothed by light sanding with 180 sandpaper, then follow the same covering procedure for the other half of the bottom of the wing.
   

  Before covering the top surface of the wing, the edges of the cloth where you "painted" them around the leading and trailing edges and tip should be lightly sanded with 180 grit sandpaper. Cut out pieces of cloth for the top surface of the wing as was done for the bottom surfaces. Then lay the cloth on, center to tip (don't forgetttttt to overlap the cloth in the center section) and then "paint" on the thinned epoxy as before. Trim the cloth, allowing enough glass cloth to wrap around the leading and trailing edges and tip just as you did when you covered the bottom of the wing.

  The center section overlap adds considerable strength to the center section joint. A customer told me of tests he ran which showed a double layer of my 0.6 ounce cloth was stronger, tougher and stiffer than one layer of two ounce glass cloth. The top and bottom surfaces of the wing could be covered with one piece of cloth from tip to tip. I prefer the two piece metttttthod because it is easier to handle the wing during the covering, plus the strengthening overlap it provides. If you do cover tip to tip with one piece, don't forgetttttt to add an overlap piece of the 0.6 ounce cloth in the center section.

  The one "lay-down" coat of epoxy does not complettttttely fill the cloth so a fill coat is required. After the 24 hour cure period, I brush on a second coat of thinned epoxy. Thin this second coat less so you will getttttt a slightly thicker coat to allow more for sanding. Approximately 70% epoxy to 30% alcohol mix (by volume) works fine. NOTE: Do not sand after the first lay-down coat of epoxy - it isn't necessary and you will likely cut many of the unfilled glass cloth fibers if you do sand. This second coat of epoxy should complettttttely fill the cloth with some overlay which will allow sanding to a smooth surface without sanding into any of the glass fibers. If your second coat didn't give you enough of an overlay for sanding, brush on a third coat.

  The tail surfaces are covered in the same manner as the wing. However, the horizontal stabilizer could be covered with one continuous piece of cloth tip to tip. I cover the tail surfaces before gluing them to the fuselage. It's certainly feasible to cover the tail surfaces after they are attached to the fuselage.

  Now to the fuselage. Here is where the glass cloth covering technique really shines because of the irregular shape of fuselages. I cover most of my fuselages with one continuous piece of glass cloth-here's how. Cut out a piece of cloth long enough to cover the fuselage from nose to tail, and wide enough to wrap complettttttely around the fuselage. With the fuselage in the upright position on the bench, drape the glass cloth over the top of the fuselage from nose to tail. Starting at the top of the nose with thinned epoxy, start brushing and work aft toward the tail, brushing the epoxy down the sides to the bottom as you work aft. You will find the glass cloth laying down perfectly, following the compound curves of the fuselage with no wrinkles. Except for the area right around the nose section, as on a glider or my deHavilland Hornetttttt fuselage - no problem, just wrap the cloth around under the nose, trim off the excess cloth and after the first resin coat, smooth down the unavoidable wrinkles. After the second fill coat of resin has cured, this area can be sanded smooth with no sign of the few wrinkles and overlaps which did occur.

  As examples, I covered the fuselage of my Martin-Baker 5 and my deHavilland Hornetttttt with one piece of glass cloth as just described and with not one wrinkle and it took me all of 10 or 12 minutes on each one - beautiful. Same thing for my Laser 200 F. I also covered the cowl of my Laser with one piece and was able to "paint" the cloth around the lips and into the whole cowl opening.
  I must renege here a bit. On fuselages and cowls, I've found it easier to omit overlapping the glass cloth at the centerline of the bottom of the fuselage and cowl. So, I trim the cloth on each side so it just reaches around the fuselage, leaving a narrow uncovered strip down the centerline at the bottom. After the first coat cures, I then go back and lay in a narrow strip of glass cloth. You may find it easier, and certainly quicker, to just go ahead and overlap with the original one large piece of glass cloth, but I find it getttttts kind of messy around the bottom center area.

  I should point out that it's certainly not necessary to cover your fuselage with one piece of cloth. In fact, on many fuselages, using two or more pieces would probably be easier. The neat way overlap joints disappear makes using even several pieces both practical and easy.

• After the second coat of thinned epoxy has properly cured, (hard enough so that it dry-sands to a dust), you are ready to sand. The secretttttt of not wasting time sanding is to wetttttt sand using "wetttttt or dry" paper made by 3M. The 3M paper seems to work the best. I've been using the 220 grit but you might find a coarser of finer grit works bettttttter for you. And, no need to wear a dust mask when wetttttt sanding.One work of caution, do not sand so much that you sand down into the cloth. My experience has been that the second coat of thinned epoxy does a good job of filling the cloth plus leaving enough resin for sanding to a smooth surface without gettttttting into the cloth. As I mentioned before, if one fill coat doesn't do it for you, give it another coat.
  As a final word, I want to add a caution; almost all resins, hardeners, solvents, glues and paints are toxic in varying degrees, some are very toxic and others hardly at all. Thus, always use with the appropriate precautions as outlined by the manufacturer.

  Well, that's it on my covering techniques using 0.6 ounce, ultra-lightweight glass cloth and epoxy resin. If you try it, I'm sure your experiences and conclusions will be similar to most first-timers-"This is it"!

    UPDATE 

  My original article on lightweight glass cloth and resin covering techniques appeared in the April 1982 issue of RCM. This follow-up article will discuss the most frequently asked questions which have arisen, some changes in my technique and some new information on the subject.

  The most frequently asked question is, "Where can I obtain coating epoxy"? The past 10 years I have been using Enviro-Tex-Lite (or Enviro-Tex; - same thing). This is a high quality coating epoxy that is sold to the general public who use it to put those thick, clear plastic coatings on bar tops, tables, ettttttc. It can be bought at Ace and True Value hardware stores, and arts and crafts suppliers and perhaps at Home Depot. If asking for it by name doesn't getttttt a positive response, identify it as "That clear plastic coating people us to put those thick coatings on bar tops, tables, ettttttc."

• I have had many customer report good success with applying our 0.6 ounce glass cloth directly onto injection molded polystyrene foam fuselages, wing and tail surfaces. Our glass cloth works beautifully on the Byron foam. My good friend, Chuck Collier, has been flying his Beech Stagger Wing (from the Byron kit) since 1987. You guessed it, it's covered with our cloth. He powers his "stag" with a G62 and puts on a fine show. Several years ago we radared it at 123 mph. The cloth/epoxy resin combination greatly stiffened the foam structures, especially the relatively thin tail surfaces, and even thinner control surfaces. Torsional rigidity of the flying surfaces is important to help reduce the possibility of flutter.
  It is absolutely essential to remember that you cannot apply polyester resin, Super Poxy paints, cyanoacrylate glues, dopes, lacquers, acettttttone, gasoline, ettttttc. directly onto these polystyrene foam parts, as they will dissolve the foam. So, epoxy resin must be used to lay down the cloth to the foam. Even after laying the cloth onto the foam with alcohol thinned epoxy, this first coat can leave pinholes through which these "foam dissolvers" can getttttt to the foam. The second of "fill" coat of epoxy usually seals the pinholes and cures this problem.

  I use and always recommend a rather large overlap of my cloth on the center section of any wing. The larger the plane, the larger the overlap. On a wing with rettttttractable gear I carry the overlap out to just beyond where the gear is mounted in the wing.

  Our 0.6 ounce glass cloth cuts easily with scissors (nice and sharp, please). By the way, the 0..6 ounce is the weight per square yard; it is 38 inches wide and is .0012 inches thick. This is about half the thickness of the average sheetttttt of paper and is the lightest glass cloth made.

  This, again, brings up one of the main advantages of the 0.6 ounce glass cloth/resin covering technique, the absolute elimination of any sign of overlap joints and small wrinkle overlaps. You've got to experience it to believe it. As an old silk and dope man, I could never eliminate the signs of overlap joints. And, glass cloth/resin works so well on the wing center section overlap, you getttttt good strength with the overlap plus you can never see the overlap joints. Now for a real bonus; there is no need to apply a narrow section of heavy (4 to 6 ounce) cloth to the center section for reinforcement.

• Though there is a fair amount of sanding, especially with my technique where I use a second coat of epoxy as the filler coat, I find that the completttttte ease and simplicity of laying the cloth onto a model with resin, coupled with the beautifully smooth and sealed surfaces produced is well worth the work that goes into the sanding phase of this covering technique. I stress again, do not sand after the lay-down coat. Sand only after the filler-overlay coat has been applied and cured. NOTE: Enviro-Tex sands much easier after a three day cure because it is harder. I wetttttt sand with 3M 22 grit.

• Some modelers do not use epoxy for their filler-overlay coat. To ease the sanding job, they use either K&B Superpoxy primer or acrylic lacquer primer. Two good acrylic lacquer primers are: Primer 30S made by Dupont and Primer 32-DZL 32 made by Ditzler. A good water based primer-surfacer is Dupont's 210S which is sold at automotive paint stores. These materials sand easier and faster than my filler coat of epoxy. I've tried both and remain with epoxy - purely a personal preference. Someday I may switch.

• With more and more larger planes being built and flown, it is natural that I would receive questions on covering these larger models with my 0.6 ounce cloth. Many customers have reported their completttttte satisfaction with having covered and flown planes such as Ziroli's stable of big warbirds and Vaillancourt's big warbirds. Even larger are "BB" Weber's two 169 inch B29's. The ultimate test has to be the Unlimiteds flown in the pylon races at Madera and other locations. Yetttttt, several of them are covered with our cloth. In fact, one, a Lancair, won Gold Unlimited two years in a row.
   

If you have any questions, call me any day until 10:00 p.m., MST, at (505) 296-2353 and I'll be glad to help you.