Water rockets - What's on the board

On the edge of the field, there are 2 'observing stations': a tripod with a board onto which you tape a sheet of paper. There is a plumb line so that you can align the edge of the sheet with vertical. On it, there is a PVC tube, which pivots on a nail and is held with a cork.

When there is a launch, observers follow the bottle by looking through the PVC tube, and leave the tube at the highest point. Draw a line along the tube and number it.

After 5 or so launches, remove the sheets and bring them to the board.

Then, on the board, I do the following (6) steps:

It shows that there is a sweet spot: too much water and it is harder to lift all that weight off the ground, too little and you have no mass to expel and make you go.
On this day, a height of 112 feet was reached with 1/2 cup of water (in a 1-liter bottle at 60 psi).

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Hubert van Hecke
Last modified: Tue May 9 22:36:25 CDT 2017