CPD Workshops

Sailboats

by Amy Collins February 18, 2019

This activity was created as part of a Gratnells What’s In My Tray CPD workshop for secondary science teachers and technicians to support practical work and delivery of the curriculum. It can be carried out as a stand-alone activity for students or combined with other activities from the session to form a STEM carousel.

You will need (per team of 4):

  • 1 x Gratnells A3 tray
  • 1 x Gratnells shallow F1 tray with office insert and lid
  • 2 x Gratnells mini tray or food tub e.g. cream cheese or margarine
  • 3 x Wooden skewers
  • 4 x Corks
  • 1 x Water proof tape e.g. insulating tape
  • 2 x A4 card
  • 2 x Scissors
  • 1 x Blue tac
  • 4 x Yoghurt pots
  • 10 x Lollipop or craft sticks
  • 5 x Elastic bands
  • 5 x Foam packing beads
  • 1 x Bubble wrap square approx. 10x10cm
  • 1 x Packing material square approx. 10x10cm
  • 10 x Edx Education Dinosaur Counters
  • 2-3 felt tip pens or other art materials for design/decoration (optional)
  • Sufficient water to half-fill the A3 tray
  • Absorbent cloths or towels to catch any drips or spills

Tip: if you are running this activity as a team challenge, use different coloured card for each team, matched to the colours of the shallow trays and dinosaurs to promote team identity. You can substitute any of the equipment listed for other appropriate recycled or craft materials, but to maintain fairness, each team should be given the same equipment.

Each team will need their own set of equipment, however, at the end of the carousel, after the final race, the boats can be dismantled and much of the equipment reused for future or alternate activities.

This activity also works as an individual challenge, just half the amount of equipment.

Preparation:

  • Organise the equipment into the office inserts of the shallow Gratnells trays and put the lids on.
  • Half fill the A3 trays with water.

What to do:

  • Use any or all of the tray contents to make two sailboats of differing designs, each able to carry five dinosaurs.
  • Mark each boat with your group’s name.
  • The winning boat will be the one that safely carries all its passengers across the sea (A3 tray half filled with water) in the quickest time. You can only use your breath to power the boats.
  • Points will be allocated to the winning team, e.g. fastest sailboat gets 5 points, next team 4 points and so on.

Tidy up time:

  • When you have completed your sailboats, or when the allocated time is up, put your assembled boats on top of your shallow tray and put it to one side until the end of the carousel, you will all be racing against each other at the end of the session.
  • Put a fresh tray of consumables on the table for the next team.

When all participants/teams have completed the activity, conduct the sailing tests. Line the A3 water trays up next to each other, place each boat (two per tray) at the nearest edge of the tray, floating on the water. One person from each team should stand behind each boat. Do a countdown…. 3, 2, 1, blow! Observe which team’s boat reaches the opposite side of the tray first, second, third and so on.

Tip: it can be useful for an observer to stand at 90 degrees to the action, in line with the tray edge/finish line, and video the race using a camera, tablet or smart phone. If it is a close finish, the race can be played back, in slow-motion if needed, to check who has won.

What is happening?

The two main components of a sailboat which enable it to move forward effectively are the sail and the keel. The physics of sailing involves interactions between 1) the wind and the sail and 2) the water and the keel. In our activity, many of the boats may have been built without a keel, reducing the stability of the boat. The principle interaction then becomes the one between the bottom of the boat, known as the hull, and the water.

The force of the wind, your breath in this case, acting on the sailboat is broken down into two components, lift and drag, so much like the considerations that need to be taken into account when building an aeroplane. Air flow over a sail is similar to air flow over an aeroplane wing.

To make the best sailboat, you will need to consider the following factors:

Hydrodynamics – How easily the boat moves through the water, or how much water it ‘pushes’ as it moves. Boats with poor hydrodynamics push a lot of water, this is known as drag or fluid resistance, the formation of surface waves and wave resistance also needs to be considered. To sail quickly and smoothly, you need as little drag and wave resistance as possible.

Buoyancy – When something floats we say it is buoyant. The shape, design and construction of a boat determines its buoyancy and therefore the weight of cargo (dinosaurs in our activity) it can hold. Archimedes’ Principle tells us if the mass of the water displaced is equal or more than the mass of the boat, the boat will float. Therefore, the more water that the boat displaces the better it will float and the more weight it can carry. Once the boat’s mass is heavier than that of the displaced water then it will sink. Some of the objects in the equipment tray are more buoyant than others and displace more water than others. Adding these items to your boat design will increase its buoyancy.

Upthrust – Water pushes upwards with a force called ‘upthrust’. You can feel upthurst if you try to push a light object such as a balloon under water. If the weight of an object placed on the water is equal to or less than the force of the upthrust then it floats. If the force of gravity on the boat is stronger than the force of the upthrust then the boat will sink.

Wind force – The directional thrust comes from the force of your breath (the wind) as you launch your boat. It is important to use the right amount and direction of wind force for your boat’s design or you could topple it over.

Lift – Created when the air blowing in to the sail on the windward surface is pushing harder (has higher pressure) than the air behind the sail on the leeward surface (lower pressure). The pressure difference is what enables the boat to move forward. You can experiment with the shape of your boat’s sail and angle of attack to achieve the most lift (forward movement).

To create the fastest sailboat, all these forces must be in balance. Will your boat sail quickly and smoothly or will it topple and sink?

Other things to try…

  • Discuss the differences in the sailboat designs, why were some more successful than others? Research different sailboat designs and learn as much as you can about what is needed for successful sailing.
  • Modify your design or build a new sailboat based on your observations and research. Take photographs of each design and videos of your boat sailing across the water tray, note the results of your modifications and what you plan to do next.
  • Are there other materials that are be better suited to use for sailboat construction? Collect up a variety of recycled objects and materials and modify your sailboat’s design and construction to put them to best use.
  • Decorate your sailboat with your name, or give the sailboat its own name, number or logo.
  • Make the challenge more exciting by only giving yourselves 5 minutes to build the sailboat.
  • Have a couple of round robin competitions, sailing your boats against each other, to see which is quickest.
  • Share your videos and photographs on social media using #WhatsInMyTray.

Health & Safety

As with all Gratnells Learning Rooms What’s In My Tray activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations.