Activity 3: Build a Ship!! :D

Activity 3: Buoyancy, Stability, Drag of Surface Vessels

Hello guys, welcome back to our blog! Today's activity is all about water and ship. Our lecturer, Mr Tune has kicked start the lesson by showing us the video of the history of ship. In the ancient time, the Europe countries build the ship for war. When the scientist or engineering first built the ship with 1 layer to locate the cannon, they showed it to the king. The king looked at it and felt that the warship is not strong enough, he wanted the strongest warship to win the war. So the engineers ( which are the carpenters that time)  designed the warship in 2 layers for the cannon.

Then we have some lessons about our today activity. He taught us about the shapes that affect the stability. This is quite related to one of my idea. Initially, one of my idea for our main project is we make the vehicle in a sphere form.

A sphere form vehicle is not that good as it will be easy to capsize. Besides, it is quite tough to find the center gravity of a sphere vehicle to counter the capsize by the buoyancy.

Besides, we also learned the relationship between the shape and the drag coefficient. Based on the lesson, the streamlined body has the least drag coefficient. Yet, we must know which side to face the flow of water else it will increase the drag coefficient of it.

But, if the vessel is not very large, the drag coefficient will not be affected much.

Yeahh! Now is the time for all the geniuses to workout. We have to build out a ship that can able to withstand the weight of 2 bottles/cans and a pump. The pump is for propulsion purpose.

This is the pump.

We have to use the polystyrene foam to make our ship. Because of the insufficient of materials, we have to share 1 big sheet of polystyrene foam with our neighbour.Before starting to cut the polystyrene foam, we must do some calculation first to find out how big we should cut by finding the volume. The volume of the polystyrene foam we cut is larger or equal to the volume of the water displaced.

First of all, we measured the mass of the 2 bottles and the pump.

Then we do some calculations to find out the volume of water displaced and the volume of polystyrene foam to be cut. Let me show you our calculations below:

After that, we think about the shape for our boat. Initially, we came out an idea of making a streamlined body for the boat. We can make it by combining 1 semi-circle and 1 triangle.

Yet after some discussion, we decided to make it simple by using triangle and square only.

Then, we start to draw out the shapes on the polystyrene foam and cut it using the hot wire foam cutter.

We assemble the polystyrene foam using the UHU glue but it is not strong enough. So we use wooden stick to poke them together. We then install the pump to the wooden stick between the half triangle by using the cable ties. To save the usage of polystyrene foam, we decided to secure the water bottles using the perforated steel bands and steel wiring. Ta daaaaaaa! This is our first hand-made boat.

Does it look cool? Like a special combat boat? HAHA

So we felt very excited and quickly went and tested out our boat. Yet, we felt disappointed as the boat capsized. We thought we did wrongly about the support for the water bottles. After trying few times it still capsized!

Suddenly, I feel curious that why are other groups' boat is so big in size but ours is so small. So I went to double check with them and I realized that actually we had the wrong concept in our mind. The volume of the polystyrene foam should be just the polystyrene which the surface is in contact with the water. We should not include the platform but we designed it in such a way that the volume of the platform included the volume of the polystyrene that float on the water. The polystyrene foam that float on water did not have the actual volume it should have. That's the reason why our boat will capsized.

Due to the lack of the time and insufficient of materials, we cannot redo a boat. Thus, our professor, Chung Haw gave an idea that we can add 2 rectangular polystyrene foam in between of the half traingle to balance back to the actual volume. The photo below show the improved boat.

We improved and tried the boat again. And finally this time the boat was able to float on the water. When we powered our the water pump, the boat was able to move forward also. Then, we did a test to the boat to figure out the maximum angle it can withstand without capsize when the boat is tilted to 1 side on the water. Then we conducted a test to figure out the metacentric height of our boat by adding weigh on 1 side of the boat.

The activities we did today is no doubt very useful to us. We can apply all the knowledge we have learnt today in our main project.