Week Five 5/4/2017

     This week, the group continued to expand upon our ability to heat shrink objects of varying dimensions. Whereas during week 4, only small, solid objects such as markers were wrapped, this week, a a roll of tape was wrapped. This is important because it has one critical difference: there is an air gap. In wrapping the roll of tape, it was found that slowly, constantly moving the heat gun from a distance of about half a meter worked the best to evenly heat the shrink wrap, resulting in what is seen in Fig. 1.

Figure 1: The tape roll
with a very smooth, tense
surface after heating

     The key for success in this materials test was both slow heating and the rigid frame of the tape roll.  

     Using knowledge gained from that testing, we then tried to apply those heating principles to the kite. Knowing that the small diameter of the frame's carbon fiber rods would poke through the heat shrink, cardboard ends were added to the rods to spread the force over a larger area and decrease the likelihood of a tear. Onto these cardboard stoppers, string was attached between each end of the kite using sliding knots, which created a very tense frame.

     The entire kite was put between two sheets of heat shrink, and then it was sealed inside using a wood engraving tool. Excess wrap was cut off, and then the heating process commenced. 

     The result found was twofold. The first result was that by heating the top layer of the kite more than the bottom layer, a curvature will form, the severity of which is dictated by the difference in heat applied to each layer. The second, and more important, result was that as the curvature described above and pictured in Fig. 2 occurred, it decreased the distance between the 4 tips of the kite. This means that the strings that previously created a very tense frame for the heat shrink to adhere to were now limp and useless. This made the kite bow and made it incredibly three dimensional, which created a lot of drag forces and made flight a laughable concept.

Figure 2: The balloon-like structure of the kite created severe curvature as a result of a less rigid frame

    The main conclusion to be drawn from this iteration of the kite is that an entirely rigid frame must be made, and the next iteration will replace string with carbon fiber rods. These will prevent the 3-D balloon-like structure pictured in figure 2, and will allow for a thin profile, more rigid frame, and a tense kite skin.