This article was originally published in Fly RC’s May 2016 issue.
By Gary A. Ritchie
For decades experienced RC model air-plane builders, especially scale builders, have relied on fiberglass as a tough, easy-to-apply balsa covering material that resists dings and scratches and will accept most paints. Fiberglass cloth for model airplanes comes in many weights from a half ounce to three or more ounces per square yard. Typical application involves laying the cloth on a prepared wood surface, then painting it on with an epoxy resin. The resin soaks through the cloth, binding it tightly to the wood. Another coat of resin and more sanding then yields a hard surface that can be painted to simulate full scale aircraft surfaces.
Up until very recently, fiberglass cloth was covered and sealed using a two-part epoxy/hardener mix that required careful measurement and mixing, many hours to dry and organic solvents for clean-up. Those days are over. Now this job can be done much more rapidly using a water based, one part resin that dries in less than an hour. The product is called Eze-Kote, is manufactured by Deluxe Materials in the U.K. and is marketed here in the United States by Horizon Hobby. It is actually a finishing resin, not for laminating in the way you might use epoxy.
I recently obtained a sample of this material along with some Deluxe Materials fiberglass cloth, marketed as “Super Lightweight Glassfibre Laminating Fabric”, and decided to try it out on a set of balsa floats that I recently built. If you saw my article on floats, which appeared in the June 2015 FlyRC magazine, you may have noticed the floats that I installed on my Tiger Kitten model (page 50). I had initially covered these floats with Solartex fabric, which was strong and light and gave me good service for two flying seasons. During the second season, though, I noticed that they were beginning to leak around the seams, so I decided to strip the fabric of and sheet the floats with 1/16” balsa, then cover them with fiberglass cloth. This offered me an opportunity to try Eze- Kote for the first time (Figure 1).
Here’s how I did it. With the floats sheeted and sanded, first with 120 grit then 320 grit sandpaper, I cleaned them with a tack cloth to remove all traces of balsa dust. Then I painted each float with one layer of Eze- Kote – right out of the bottle, no mixing, no weighing. Eze-Kote has the consistency of thinned latex paint and goes on smoothly and easily with a small paint brush (Figure 2).
After the Eze-Kote had dried (about one hour) I sanded each float lightly with 400 grit sandpaper in preparation for glassing. This yielded a hard, smooth finish.
I began by covering the float bottoms with 1.5 oz. cloth (Figure 3). I used this heavier weight cloth on the bottoms because they often take a bit of punishment – both from smacking into floating objects in the water, and also when the plane is being run up onto the beach after landing. This was done by brushing the Eze-Kote on top of and through the fabric, soaking the fabric and sealing it to the balsa. Before sett ing the pieces aside, I examined them carefully for any bubbles and squeezed them out using the brush or a credit card squeegee.
After about two hours of drying time I sanded along the edges of the bottom with a 320 grit sanding bar to remove the extra material (Figure 4). This technique results in a very neat, smooth edge.
After the bottoms were finished, I cut some 0.6 oz. cloth (Figure 5) to cover the sides and tops of the floats using the same technique described above (Figure 6). I allowed these to dry overnight. Finally, I applied another coat of Eze-Kote to both floats and after a thorough drying they were wet sanded with 320 grit paper and were ready for priming (Figure 8).
After I was finished glassing I rinsed my brush out with water, and poured the remaining Eze-Kote back into the bottle. I should also point out that Eze-Kote is almost odorless and washes of your hands with soap and water. The final step in covering my floats was to prime and paint them. I applied one coat of Rust-oleum 2X Flat White Primer (any good primer will work) let it dry (Figure 8) then carefully wet sanded it with 320 grit paper (Figure 9). I then applied two coats of flat black spray paint. Finally, I applied some trim strips cut from stick-back trim and applied them using the “Windex Method” (Figure 11, 12).
The advantages of Eze-Kote over epoxy/hardener are many. For starters, it is nontoxic, nearly odorless, requires no measuring or mixing, can be cleaned up with water, and will accept virtually any kind of paint from fuel-proof dope to water based paints. Curing, which is enhanced by light, continues for several days, improving the final properties. It is light, tough, strong, can be easily sanded and is now readily available in the U.S. through Horizon Hobby.
Another feature I like is that when you are done putt ing your fiberglass cloth on you can pour the unused Eze-Kote back into the bottle. This lets you do several small jobs without having to mix epoxy and hardener every time then throw away the epoxy that is left over. In the case of my floats, I covered only one or two surfaces at a time and let them dry before covering another surface. Although I used fiberglass cloth specifically supplied by Deluxe Materials, Eze-Kote can be used on virtually any type or brand of commercial fiberglass cloth.
My experience with these fiberglass-covered floats so far has been ? rst-rate. They are tough, strong, light and beautiful – just as if they had been ? ber-glassed in the traditional way. My days of fiber glassing with epoxy resin and hardener are over!