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Yarr, Matey! If’n ye want to be sailing the seven seas in yer very own pirate ship, ye’ll first have to understand how a ship works! Ships be complicated machines, aye, with mainsails and topsails and bilge pumps and rudders, and all of ‘em have different jobs. But since ye are just wee pirates-in-training, we’ll start simple: a seaworthy pirate ship needs to float, and if’n it ain’t built right, it won’t float right! Ta really understand it ye need to build and test out a few basic ships yerself!
Materials:
- A bathtub full of water
- Aluminum foil
- Masking tape
- Small weights like marbles or metal washers
Process:
- Tear off a few square sheets of aluminum foil. You’ll use them to make a few basic ships.
- Fold one of your foil sheets into a wide, flat-bottomed shape by folding up the sides just a couple of inches away from the edges and taping the corners to help stop water from leaking in.
- Fold another into kind of a cone shape, with a big point towards the bottom.
- Fold a third one around a large glass so it takes the shape of the glass.
- Form a hypothesis: which of these three shapes do you think will float the best?
- One at a time, test your hypothesis by putting the foil boat in your bathtub and then gently placing your weights onto it. The one that holds the most before it sinks is the most buoyant, meaning it floats the best.
- Experiment with other ship shapes based on what worked well!
Summary
Buoyancy is the ability of something to float. Real ships are made of wood, which is buoyant and floaty already, but enough weight on top of anything will make it less buoyant and cause it to sink. The chances are that the flat-bottomed shape you made was the most buoyant, and that’s because it has a larger surface area than the other shapes. More of the foil was in contact with the water, which means that there was more water underneath it pushing up on it, so it could support more weight before it sunk. The other shapes had less water pushing up on them, which made them less buoyant.
Flat-bottomed boats exist, but they don’t leave much space for things like pirates, cannons, and loot. They also don’t move through the water very well, even though they float really well. Shipwrights, the people who build ships, made sure that ships had a wide bottom to increase buoyancy but also had a smooth shape to cut through the water.
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