The first thing to do when designing a wing is to look at the airfoil shape that the wing will take. The airfoil is a shape that has characteristics that create lift. When looking into the airfoil, like any portion of the plane, it is important to first do research into the subject and to look at what people have done before. This team looked into what airfoils previous teams at this school used, to see if they used similar airfoils and how well the airfoils preformed. The team then used an airfoil software, ModelFoil, and calculations to compare the characteristics of many airfoils. The airfoils included 2000's E 211, 2001 E423, 2002's OAF102, and from our own research the E214 and S1223. The program was able to generate many of the key numbers that are important to engineers in designing the wing, top among these is the coefficient of lift and drag at different angles of attack. The plane to be designed is a heavy lift cargo plane and there for must have a high coefficient of lift, even at low speeds, and has a low coefficient of drag. This maximizes the ability of a plane with a heavy load to take off within the given output of engine constraints. Comparing the data received from the software, and other calculations it is determined that the S1223 is the best airfoil with a high coefficient of lift and a small coefficient of drag. The graphs generated from the ModelFoil software can be found in appendix B-1 showing comparisons between CL vs. Angle of Attack of the various airfoils. This data can then be used in the various calculations in order to determine the characteristics of the plane see the calculations section for further details.
The airfoil is the most important part of the wing creating lift but there many decisions to be made before the wing design is done. The wing shape and the angle with which it makes parallel to the ground improve some of the characteristics of airfoil chosen. The wing shapes considered by the group were rectangular, tapered, elliptical, swept and elliptical each with there own positive and negatives see appendix G. The rectangular wing shape was chosen mainly for its easy of build, though its stall characteristics are worst then that of the elliptical. The wing angle gives many improving characteristics to the airfoil including stability and performance see appendix G. A dihedral angle is the common angle used on model aircraft and has been used many times in previous years. The dihedral angle improves stability in side to side motion as well as stability in turning.
Once all of the components of the wing are decided on, and the major calculations concerning the characteristics of the plane are completed, the design for the construction can begin. Design for construction takes into account the decisions made the materials to use and way in which parts can be fabricated. The wing makes up the largest area of the plane but is among the lightest. There are to main construction methods for building a model aircraft wing foam core and risers, each with there benefits and drawbacks. The foam core is and easy construction and has been used with varying degrees of success in the past. The foam core is just that lightweight foam that is shaped, with a hot wire, in to the airfoil design, and then covered with various materials to improve strength. One year the covering was Kevlar attached with an epoxy, the epoxy soaked in to the foam making the wing heavier then designed, the plane did not do well that year. Other years they have used foam core with a little better success but not much. This year the team has decided to use the rise constructions method which entails creating many thin airfoils, out of balsa wood, and spacing each along wooden spars through out the wing. The spacing was determined to be every 2 inches, this distance was determined from studying commercial available planes and a previous years plans for a riser wing. A front edge wooden dowel and two middle spares give the wing its strength; a tailing edge supports the flaps, gives the tailing edge airfoil shape and also lends strength to the wing. See appendix B-2 for the detailed design of the rib and appendix B-3 to see the final fabrication of the wing.
The wing a static analysis, in SolidWorks, was done on the wing to determine if it would crack under the lifting force. This was a simple beam analysis on half of the wing, it was determined that the lifting force was not sufficient to break the wing. This final analysis with the completed design of the wing can be found in appendix B-4.
Wing construction started early in the second semester with the construction of the selig 1223 rib airfoils. A full scale print out was made of the rib from the model constructed in SolidWorks which was used as the original template. The template was placed on a sheet of balsa wood and carefully cut out. That template was then taken to the machine shop where George hand cut two sheets of aluminum into the precise shape of our ribs, these metal cut outs were our primary templates. Once the aluminum templates were completed members of our group that were in charge of constructing the wing then carefully scribed over 70 ribs out of basal wood sheets. The next task for the team was to procure four 5 ft. 3/8 in sq. spars for the wing, 5 foot pine wood was purchased then cut to the appropriate dimensions on a band saw. The leading edge was fabricated by connecting two 2 and 1/2 foot, 3/8 in diameter, wooden dowels together using a tongue and groove technique. The trailing edge was constructed in the same manner using 3/8 sq. basal wood, then attaching a triangular trailing edge over 2 feet. The other three feet were left for the ailerons to be attached to later. The wing was constructed in two 5ft halves to be attached later. The ribs were placed at an interval of two inches as per the design along the bottom spar, the leading and trailing edge. The upper spar was the last piece to be added to the skeleton of the wing. The two halves were then joined in the middle with a 4 in sheeting of balsa wood covering and a wrapping of Kevlar tape for extra strength. The servos were then added at mid-point of each aileron; each was glued to the middle spars with the connecting rod to be added later. The wires to connect the servos to the radio receiver were run through each rib to the middle of the wing where they came out and are connected to a y-connection that is plugged into the receiver. This y-connection makes the servos move in conjunction for turning, when one aileron goes up the other will go down, unfortunately with this set up the ailerons cannot affect the angle of attack during take-off and landing. The wing now complete was to be covered with a plastic shrink wrap like material called monocote. The monocote is placed over the skeleton and heated till the glue on the bottom surface adheres to the ribs. The monocote provides the surface area for lift and with an expert hand can be put on with on very smoothly with no wrinkles that create drag. Once the monocote was added to the wing the ailerons were attached with small fabric hinges and the connecting rod was added to them to connect them to the servos. This is a complete history of how the team designed and fabricated the wing for the 2004 Stevens Heavy Lift Cargo Plane.
Based on the research the group had performed last semester, the use of NACA0012 airfoil for horizontal stabilizer will provide minimum drag and maximum stability since it has a symmetrical shape of top and bottom. Moreover, the use of a thin planar surface for the vertical tail will provide a minimum weight to the plane. The vertical tail will have a round shape in front and flap on the rear side.
Our group used risers that are made out of balsa wood connected with simple wooden beam for the construction of the horizontal tail. Using wood for tail assembly is to reduce the weight and ease to construct. Since the vertical stabilizer is not an airfoil, it will be made out of wooden beams only. The wooden structures may be inaccurate during the cutting and bonding phase, however they would not affect the critical performance of the plane.
Let, on the web or in online databases, filter by thickness and camber with preview images of the airfoil sections. Also, download the data file data in various formats or use the data file data in the tools.
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