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Senior Design At 100mph - Part 1
1,392 viewsThis is the story of my senior design project.
A crack team of aerospace engineers and I have been assigned the task of designing and building a radio controlled plane which meets the following criteria.
- Must fly at a speed of 100mph or greater in level flight.
- Must withstand a load of 7g’s
- Must not use an engine with displacement larger than 1 cu in.
- Must be reasonably controllable
- Must have retractable landing gear
And a couple other little details or something. We were given two semesters to design and build said aerovehicle and we are currently at the beginnning of the second semester. All design work is done, the plane is modeled and all the CNC files have been created. In case you are wondering, CNC stands for Computer Numerical Control, and is simply a way of controlling a machine to do what you want it to. In our case, this machine is a highpowered waterjet capable of shearing through stone, metal, or - as in our case- thin sheets of wood. By using the waterjet, we can ensure that we get perfectly cut parts for our construction.
Pieces laid out to send to the waterjet.
But lets go back to the beginning. First of all, we needed a concept for our plane.
Voila! That was easy! And pretty too.
However, this picture was really nothing near a complete design. It was simply a concept for us to visualize the plane, and a model to use in the future as we referred to different features in the design. As you will see, the final design differs quite a bit from our first concept.
Then came all the boring work , like calculating wing size and fuselage length. We also calculated control surface area’s and center of gravity, as well as stability calculations to ensure our plane was not going to be a nightmare to try to fly!
Here is a FLUENT file that shows the pressure distribution on our fuselage. This computer program allowed us to get a rough idea of what kind of drag to expect on our plane’s fuselage. This, in turn, was plugged into our equations to help us see if we could achieve the speed we needed with the drag and thrust we had.
On and on, we calculated and designed for a whole semester. Towards the end, we started to get a good idea of what the plane needed to look like, so we began to model it using a program called Solid Works. This program allowed us to covert our drawings and numbers into parts and pieces that we would need to assemble together to create our plane
Finally, the design was done. Our plane now looks like this:
So let’s examine some features of the plane. This next picture is a side view of the plane. All these pictures are missing a couple stringers, these are long strips of wood running along the length of the plane to give it stiffness and fill out the fuselage profile. They have been omitted for clarity, and displayed are the four main longerons running the length of the fuselage. These will carry a good deal of stress and also serve as supports for the bulkheads in the fuselage, with built-in braces around each bulk head. This can be seen in the next two pictures.
As you can see, there are a lot of little edges and notches that will need to be cut, this is why we are using a CNC waterjet to cut these parts out. The notches in the bulkheads are where the omitted stringers will fit.
The next picture is of the vertical tail assembly.
The vertical tail, or rudder, will be integrated into the fuselage. This will keep weight down, and make the construction process a lot simpler, as we won’t have to make sure we put the rudder on straight. The skeleton of the rudder is cut out of the top vertical longeron, and thin side pieces are sandwhiched on to form the rudder surface.
Now, to access the fuel tank and electronic components, a hatch will have to be cut out of the fuselage. So as not to decrease the stiffness of the fuselage, the lid for the hatch will take compressive and tensile loads as well. This is how we designed it.
The lid itself will have two sets of stringers which are not shown. The half bulkheads at the end of the lid will fit in slots formed by two bulkheads in the fuselage. This tight fit will allow tensile and compressive loads to be transferred through the lid.
The wing is an important part, and our wing will have some tricks to help it withstand the loads it will be experiencing at 100mph.
As you can see, the leading edge of the wing is made up of carbon fiber. This is wrapped around a foam core and attached to a plywood spar. Ribs are attached to the back of the spar and are stiffened with stringers, just like the fuselage. A trailing edge of balsa keeps the aerodynamic shape of the wing and adds to the bending strength. The full wingspan of the plane is a little more than 5 ft. and a specially designed box joins the two halves in the middle.
The wing will be removable from the fuselage, but remain in one long piece. This is mainly to make transportation easier.
Well, thats it for the design part of this project. Next, we will be building a test section of our wing to see if it can withstand the loads it needs for flight.
[...] that we the design phase is complete, our next phase was to construct a test wing to allow us to perform tests that would [...]
[...] Then came all the boring work , like calculating wing size and fuselage length. We also calculated control surface area’s and center of gravity, as well as stability calculations to ensure our plane was not going to be a nightmare to …Next Page [...]
Thats are curiosity facts which will aid me to go forward by the search for much more information.