Week 3 – Buoyancy, Stability & Drag

On Monday the 2nd of November 2015, we learnt about buoyancy, stability and drag of floating vessels. There was a short lecture on the concepts behind drag and buoyancy, followed by a mini activity. We found the weeks’ lesson to be really helpful as our project involves making a floatation device which can also fully submerge. I feel that this week’s lesson was very insightful and helped give us some direction before embarking on our project. Even though there was a short lecture conducted about the topic, we only learnt so much from it but the in-class activity really helped us apply the concepts.

In the class activity, we were tasked with creating a boat made out of Styrofoam which could carry 2 canned drinks but still could float without our support. It also had to be able to move via a water pump.

So we sat down and discussed the design of our boat first before figuring out the calculations. But what we did not realise was that we had to do the calculations first THEN deliberate about the design of the boat. It was tough and time-consuming at first but with the help of our lecturer, Mr Tune, we were set on the right track.

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After performing the necessary calculations, we moved on to the design of the boat. We wanted to make the front of the boat curved to reduce its drag while making the rear of the boat straight to allow the fluid to flow smoothly without creating any wakes. They are many different types of hulls we could have made but we wanted the boat to be as stable as possible. After some research, we found the catamaran hull to be the most stable among all the hulls. With regards to the load used, we did not have any canned drinks so we used Ajay’s water bottle, making sure that it was of an equivalent weight as the cans we would have used. We had to ensure that the weight of the bottle was correct, so we adjusted the amount of water inside the bottle accordingly. Subsequently, we had to secure the bottle onto the boat such that it did not shift around too much. As such, we made barriers along the sides of the boat’s platform.

WK3 - Constructing the Imps Boat

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Upon completion of the design stage, next came fabrication. Thomas cut the Styrofoam into our desired shapes using a Styrofoam cutter which was a lot more suitable than penknives. However, the tricky part was sticking them together. We only had super glue to stick them together but it took up too much time as we had to wait for the glue to dry up. To speed up the process, we decided to use satay sticks as supporting shafts and to our surprise, was really effective. So yeah, we managed to complete the body of the vessel but after that, we still had to attach the pump below the boat. We cut out a small slot beneath the boat for the pump such that it wouldn’t stick out too much. In order to fully secure the pump to the boat, we used a cable tie to tie the pump to the boat’s base.

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Everything was in place but the big question still remained, would our boat actually move and float with the load? So we proceeded to test it out. We placed it in the water, hoping it would float, and thankfully it did! We then turned the pump on and were full of joy seeing that the boat could and move quite quickly! It was also very stable.

So we went back into class, feeling very satisfied that everything worked, until we realised we forgot to install an angle finder on the boat… What a great way to spoil our celebration haha. But building the angle finder was simple enough. It did not take much time but after we were done, we headed out again to find the maximum lateral and longitudinal angles of the boat before it overturned. After that was complete, we finally relaxed and took a group photo – of the boats, not us! I saw the other groups’ boats and they were very interesting as well, each having their own unique design. I did not see any of their boats fail, so congratulations to all of us! 🙂

I really hoped this week’s lesson helped all of you as much as it helped my group for the final year project and yeah, looking forward to seeing all of the groups’ final projects at the end of the semester! 😀

Ryanfranco Lagdameo


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