Test how hull shape affects a small foil boat

Use identically sized squares to make one narrow boat and one broad one. Keep similar side heights and test them in the same basin.

Make two foil hulls from equal squares and plan to use identical small masses. Decide how to mark an observation when two readings fall too close together to separate. Even spacing on a sheet is useful only to the extent you can see where a feature crosses each line. A visible range can carry more meaning than a single estimated digit that your instrument cannot resolve.

The broader outline may carry more in a stable position before its lowest edge meets the water. Write the independent change at the start of each row and keep the outcome beside it. Include anything about a failed run that would matter to somebody repeating the setup. If you later make a neat graph, keep the rough record as well so it remains possible to inspect the reasons for leaving out a point.

Place identical dry weights one at a time near the centre, distributing them evenly. Record whether each boat leaks, tips or settles until water enters.

A crease with a pinhole can end an otherwise balanced trial early. Use the empty setup once before introducing the change you want to study. A baseline can show motion from a loose support, light falling on the screen from another direction or variation in the way the sample starts. Record what you see at that stage as part of the experiment.

Test the empty hull for leaks and record what fails first in loaded trials. Write one prediction alongside the setup. It helps to describe what would be observed if that prediction were right, including a direction, a clearer pattern or a measurable difference. This makes room for the outcome to disagree with what you expected and gives you a better question for a second run.

Match wall height and read the waterline from the side before adding the next mass. Put the observations into order and keep the raw measurements or drawings. A result can be useful at more than one level. The direction of a change may be unmistakable while the exact size is uncertain. Describe the strongest pattern the records support and qualify measurements that depend on a faint boundary or a moving object.

Write a row for each run and keep apparently odd results in the record. Mark things that went wrong, such as a shifted surface, uneven starting point or missed time, before judging the pattern. Changing how you record the behaviour halfway through can make two otherwise similar trials difficult to compare. Explain the outcome in a sentence that a reader can check against the figures or sketch. Use a second sentence for a proposed cause. If you can imagine a different cause that fits the same observations, describe a small test that would help distinguish the two. Comparing those predictions can make a follow-up clearer than simply repeating the same demonstration. Add small loads near the middle rather than near the lowest corner, then record the effect of a deliberate offset separately. End with a short account linking the changed condition, the observation, and its likely explanation. Include one uncertainty that would matter if you repeated it. This separates the physical idea explored by the demonstration from limits created by a household setup and gives another person a way to test the same claim.

Redesign the weaker hull with the same foil area and describe exactly what changed. Sketch your apparatus before you start and use the sketch to identify where each observation will be made. Write down the starting state before changing it. If another person repeats the trial, knowing the relative positions can matter more than the brand or appearance of the materials.