Once the sketch tool is active we need to create a projection. Using the sketch tool create a sketch on the interior surface of the spar. Orbit around so that the interior of the forward spar is visible. If you have any doubts as to the rigidity and strength of your spars adding spar caps is strongly recommended. Carbon fiber spars for instance are far more rigid and strong than Balsa spars. It's important to note that material choice also has a large bearing on the spar design. In this demonstration we will be adding a single spar cap on the interior of the forward bar. For smaller airplane spar caps might not be necessary as you can use a thick enough web and be fine but for the model that's being demonstrated extra reinforcement is needed. Spark caps, for RC airplanes, can come in many different varieties. This means 1 cubic centimeter of volume doubled is 2 cubic centimeters but will have 8 times the volume.ĭue to these multiplying forces, we need to reinforce the web with spar caps. That web alone cannot resist those forces especially as the scale of your model airplane grows.įor example, a RC plane that has a wingspan of 100cm will encounter, by many magnitudes, far less arrow dynamic forces than a model airplane that has a 300cm wingspan. In our current design, we have a single flat surface also known as a web. The spar must also be rigid enough to restrict torsion induced by aileron and flap deflection.ĭue to all these types of forces, a spar must be strong enough to absorb and transfer these loads. The forces spars must resist include the bending, which is composed of tensile, compressive, and shear forces. Depending on your design, the loads are transferred directly into the airframe, or into the wing box to which the body is attached. Spar caps provide the spar web(s) lateral reinforcement and rigidity much the way an I-Beam does in building construction. In aircraft, spars transfer the many forces encountered by the wings throughout the airframe.
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