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Sliced Wing Ribs


Try this technique to produce light, scale ribs with no more fuss than cutting them from balsa sheet.


By Scott Copeland


T 44


he first time I encountered the sliced-rib technique was on the pages of the March 1982 issue of FLYING MODELS magazine. In this


issue was an article about a Loening OL-9 amphibian designed by Fulton Hungerford for rubber power and I was immediately drawn to a photograph of the uncovered air- frame. This masterpiece sported built-up ribs and museum quality scale construction. As an aspiring builder of peanut scale models and want-to-be scratchbuilder, I could not fathom how anyone would spend so much time and effort building up ribs for a freeflight model which I knew from expe- rience would inevitably meet with grief! My


astonishment was compounded when the rib building technique was revealed and it was actually quite simple! I would find later that other designers


whose work I admired, most notably Mitch Poling, also favored this technique. In the early ’80s when electric powered R/C could best be described as rudimentary, Mr. Pol- ing was able to design aircraft, which flew extremely well despite the handicap of being powered by weak electric motors running on heavy Ni-Cd “bricks” (a far cry from the Li- Po batteries and brushless motors of today). One of his designs was a Sopwith Tabloid,


which he was able to fly indoors on an Astro .020 electric motor, a feat accomplished by


very few designers during this time period. In order to get reasonable flight character- istics, the airframe was designed to be strong and lightweight and as such, incor- porated sliced wing ribs. The basic principle of this design is build-


ing a sandwich shaped to the desired airfoil and then slicing individual ribs from this “slab” with a hobby saw. The result is a stack of strong, lightweight ribs, which have a built-up structure with far less effort than building each rib individually. One im- portant design feature is that all balsa pieces used to construct the sandwich must have grain that runs parallel to all of the other pieces, not only for ease of slicing, but


FEBRUARY 2012


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