Recently i built a Test Stand which could hold a water rocket so that it could be analysed by a high-speed camera (and hopefully a load cell in the future).
Below is a video of three different nozzles being tested.

The intention of the test stand is to measure flow rates and analyse the effects of different nozzles. Because the tests are static, the water is not held down like it would in flight so the water is free to splash up, allowing some air to escape before the water. Despite this, this stand will allow me to test and analyse the effects of air/water mixing and De laval nozzle designs for water rocketry, experiments I hope to begin these holidays.

    This video show the recent testing of a new avionics bay, onboard camera and a spiral nozzle.
    The Avionics bay is lighter and a better lay out then the previous design, but once again the altimeter did not register the flight. So some more testing wil be made.
    The Onboard camera worked well but placing it on a 1.25L rocket made the footage erratic.
    The Spiral nozzle seemed to work well and displays a good exhaust plume.