Blimp

Mylar was difficult to obtain. Party balloons made of mylar in shops were constructed in the factory themselves before being shipped to the shops. Companies making mylar were based mostly in China, and only shipped to European countries. Samples requested were excessively costly as well. Upon extensive research we chanced upon 2 private suppliers. One was Mr Tony Avak who supplied 12 micron mylar, which is thinner and lighter than mylar used in common party balloons, and often used in the construction of micro indoor blimps, which requires the use of an adhesive called HeatnBond. Another was Ms Fluffy who supplied commercial mylar, which bonded upon heating.

The blimp was constructed using two separate halves called ‘gores’ as per the steps below:

1. We cut out a full sized paper pattern made of newspaper.
2. We laid the mylar sheet flat on the floor, put the pattern on it, and cut out two gores of mylar according to the pattern, leaving a margin of 3cm.
3. On the 3cm margin of the mylar sheet, we put down approximately 1cm width of heatnbond strips, and tacked them down temporarily using the hobby iron at 250 degrees fahrenheit.
4. The mylar gores was then placed on top of each other with the valve (see below) at one of the ends and ironed using the hobby iron at around 325 degrees fahrenheit using a cloth sock on the iron.
5. The envelope was then flipped to the other side and ironed on that surface.

The Figure 2 above represents the schematics of the balloon valve. The heatnbond was tacked on the sides of a rectangular mylar piece as shown using the hobby iron at 250 degrees fahrenheit, and another identical mylar piece was ironed on the first using the hobby iron at 275 degrees fahrenheit.

First blimp was constructed in an ellipsoid shape similar to the commercial shark airswimmer. However we used a household iron which temperature could not be controlled accurately, resulting in the mylar melting and forming holes. Thus the balloon could not be inflated properly, however even when partially inflated could lift 120g, which was much more than we expected.

Second blimp was also constructed in an ellipsoid shape, but with slightly smaller parameters. This time we used a hobby iron at 275 degrees Fahrenheit. Sealing the balloon was much more effective, however small holes still formed on the perimeter of the balloon near the heat seal boundary, deflating the balloon within a short amount of time. These could have been due to excessive heat stress and abrasion on the mylar.

The third blimp was built in an octagonal shape, to reduce the number of HeatnBond joints.

However, small holes still appear on the perimeter near the Heat-n-Bond. We concluded that this mylar is likely to be too thin and switched to another mylar.

The fourth blimp was constructed with the exact same dimensions as the third, however this time Mylar of approximate thickness of 30 microns was used instead. This mylar also had a special aspect: one side was laminated while the other was shiny and metallized, and ironing two laminated sides together would form a strong seal. This made the balloon much less tedious to construct. Furthermore, with the added strength of the mylar, strong heat of 375 degrees fahrenheit could be applied to seal the rims without melting the mylar or creating cracks. However, we still utilized the Heat N Bond in creating the balloon valve, as we needed the metallized sides to stick to each other, and for the valve to be completely integrated with the seal of the balloon.

This new blimp worked well, however as the curved part of the valve was integrated to the seal as well the valve could not hold in the helium as strong as it was supposed to. Hence we taped it together to prevent helium from leaking, and this seemed sufficient. However the octagonal shape of the balloon hindered the forward thrust provided by the tail due to its non-aerodynamic shape, thus it could go forward only at a very slow pace. Hence all the following balloons made were ellipsoidal, with the back octagonal to provide sufficient area for purchase for the tail structure.

For the fifth blimp, we attempted to use Euler’s Method to create an ellipsoidal shape, however due to a misunderstanding of an instruction, the blimp was constructed far wider than it should have been. This resulted in a bigger blimp than expected. Eventually, however, we found this extra upthrust useful as we were able to have a bit more free weight to work around with. Below is a video demonstrating that the blimp needs a significant amount of ballast for it to be near neutral.

It also ended up being the most durable blimp we have constructed so far. A successful field test was consequently conducted with this balloon (warning – long video).

INSERT TEST FLIGHT VIDEO HERE

For the sixth blimp, we reduced the length and width of the blimp to make it smaller. Also, this time, we properly executed Euler’s method in creating an ellipsoid. However, both of these changes resulted in the blimp being way smaller than what we expected, which could only lift a weight of 60g, and thereby rather useless.

For the seventh blimp, we increased the length of the blimp while keeping the width the same as we wanted to make it more aerodynamical. However this balloon had some micro leaks and could not stay fully inflated for long.

For the eighth blimp, we decreased the length of the blimp slightly, but otherwise kept the same dimensions as we wanted to fix the source of the micro leaks. However, we were unsuccessful as the resulting balloon leaked faster than all the others. We could not pinpoint a specific source of the leaks: the valve was taped down fully to ensure that it was not the cause of leaks. It was thus theorized that the ironing technique of the mylar was problematic leading to a weak seam, however this was highly unlikely as we have had a lot of practice with ironing the mylar, all other precautions taken as well.