| GLASSING AN AIRPLANE
FOR STRENGTH AND
LIGHTNESS by George Lumpkins Most of an airplane's strength comes from the structure of the aircraft, for example, the ribs, main spars, formers, and sheeting on the wings and fuselage. However, what if this is not enough for your application? When adding more structure to the inside will not solve your problems, maybe you should consider glassing the outside of your airplane. Glassing should be done to surfaces, not to bridge gaps like between ribs on a wing. Glassing consists of epoxy lathered onto fiberglass cloth. The glassing I am referring to in this article is fiberglass cloth of any lightweight density and finishing epoxy of any make. Do not use regular epoxy as it is impossible to sand without balling or gumming up the sandpaper. Epoxy glassing is a great way to add strength to all of the areas it is applied to. First you should place the glassing cloth over the area you intend to glass and cut it to shape with one to two inches to spare at all comers. This is just in case you don't place the cloth exactly the way you want it. Next, mix up the epoxy resins for glassing. I mixed one-third hardener with one-third resin, and the last third with 91% pure rubbing alcohol. Pour some of the mixed resin onto to the area intended for glassing, and use a rubber squeegee to move it evenly around the whole surface. The wood will appear as if it is wet, but there should not be standing pools of epoxy. Next place the fiberglass cloth onto the area where the resin is. Pour the remaining resin on until all of the white areas of the cloth have taken on a wet appearance. Allow this to dry for 10 hours or so before sanding or painting. For anyone who has attempted to glass an airplane, you will quickly discover that you will get wrinkles or bubbles. If you try to push them out, the fabric tends to stretch and just makes matters worse. When I glass anything, I use the flexible rubber squeegees. These work wonders for gently sliding the wrinkles to the sides. Another suggestion, one that I use, is to take a Windex bottle (after using its contents and cleaning it) and fill it with rubbing alcohol. This will allow you to spray the alcohol onto your work evenly and it will delay the epoxy from curing immediately and thin it out a little. After you're finished, you can use lightweight spackling putty to keep the weight down and fill in the small indentations left in the weaves of the cloth. This is my two cents from my experiences from glassing on kits for strength. I personally have used all the techniques mentioned in this article. from NOTAM Bayou City Flyers, 21215 Park Bluff Dr., Katy TX 77450 TRY THIS OUT by Joe Podraza If you're a scratch-builder and have never tried to iron on balsa, you should. I don't remember the article, or in what magazine it was in, but I did try it out on a small model with tight curves in the fuselage and it worked well. No clamps or pins or holding the balsa down while the glue dries. I now use it to plank the leading and trailing edges of my foam wings as well as the cap strips. So far, I haven't had any of the planking let go. Using contact cement is okay, but once the planking is set in place, there is no moving it. With this method, you can take your time to line it up and hold it down while you iron it on. I remember the article said it was an old-time cabinetmaker's way of laminating the top ply on. All that's needed is Elmer's glue or any glue that says it's aliphatic resin, a way to squeegee it on really thin on both sides that are to be joined, and an old iron that you can pick up at any thrift store. Allow time for the glue to dry, then line up the planking and iron away. On the really sharp bends, I wet the outside of the balsa and the steam lets it bend without cracking. If you don't believe the holding bond, just iron on a sheet of 1/16-inch balsa onto a piece of foam and try to rip it off. When it comes off, the foam will come with it. Once it's on, more heat will not loosen it. Just remember to put the glue on really thin. I use a rubber squeegee, and be sure to let it dry before you iron it on. from Flypaper, Lake County Illinois Radio Control Club, Joe Podrapa.. Editor |