1.2 Making a rocket  (Page 2/2)

Assignment 3:

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Use the sketch in Appendix 1. It is important to give the rocket tail-fins so that it will be able to stand upright for the launch (See Appendix 1). Stick the page onto cardboard. Cut out the fin. Use the template of the fin and trace four fins on thicker, more rigid cardboard. Cut them out carefully. Fold on the dotted line and stick the fins around the bottle at equal distances. (Look at the sketch to see exactly where.)

Assignment 4:

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NB:

Do you know how to enlarge this sketch of a fin according to scale/proportional to a fin of ± 20 cm?

• Draw squares across the sketch: 4 in the breadth and 8 in the length..
• In this case, each square is 5 mm by 5 mm.
• Draw squares of 30 mm by 30 mm on an A4 sheet of paper – 4 in the breadth and 8 in the length (8 x 30 mm = 240 mm that will give a fin of ± 20 cm).
• Now trace the pattern onto the larger squares.
• Now you have a fin of ± 20 cm

Assignment 5:

Decide which type of body fin will be the most suitable and draw a clear freehand sketch of your choice

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Assignment 6:

To make a final drawing (correct size with captions) of the body fin on a sheet of paper. use it as a template to trace onto a thicker sheet of cardboard. (use the method as explained in assignment 4).

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Assignment 7:

To build the body of the rocket according to the following instructions

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Instructions

Make the body of the rocket by following the instructions below. Cut one 2ℓ bottle right through along the second line just below the sticker (Sketch 1). The part that has the cork in it will be the top section of your rocket. The intact bottle with the opening pointing down forms the lower section of your rocket. You need a weight in the top section of your rocket.

Why?

• The rocket is not balanced when the engine is in the lower section. That is the heavier section. You have to find a centre of gravity, so that the mass can be spread proportionally on both sides.
• It is therefore necessary to put something heavy in the upper section of your rocket so that the rocket can be more stable.
• When the fuel is added, the lower section of the rocket will be even heavier.
• When a rocket is stable, it continues flying vertically upwards, without overturning and losing direction.
• So put a few fairly big pebbles in a plastic bank coin pouch and stick it firmly to the bottom on the outside of the intact bottle that is being held upside-down (Sketch 2).
• Now put the top section of the bottle that has been cut through on top and stick it firmly to the intact bottle with masking tape/strong wide adhesive tape (Sketch 3).

Assignment 8:

In the space below, draw a top view of the position of the fins. use a protractor and pocket calculator for correct spacing

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Now affix the fins as planned. Once the rocket has been tentatively completed, it is now necessary to find your rocket’s centre of gravity and its centre of pressure.

Assessment