Second original solution I found, this nozzle use a cap that we can found on some beverages like "Orangina" or "schweppes" (I don't know if you can find this beverages in same "containers" outside of France).

Unlike those on Coca-Cola, which use a seal, these caps ensure the watertightness by a little flange as shown in the drawing below. The internal diameter of this flange is 20 mm, and when the cap is screwed, the flange becomes narrower. To make the nozzle, I hollow out the cap up to the flange. The diameter of the nozzle is then of 20 mm. The watertightness between the launcher and the nozzle is made by screewing the cap.

In blue : the bottle

In black, the cap

In red : the launcher pipe (diam.20 mm)

tuyËre.jpg (5711 octets)

Narrowing the nozzle diameter

This nozzle allows an easy achievement of a T-Nozzle.

With a large opening of the nozzle, the thrust is important, but short.(Thrust is proportional to the nozzle area and the water flow also). Thus, the idea is to keep the power for the take off, then to reduce the diameter of the nozzle with the result that the thrust is less (but however higher than the addition of drag and gravity) and the duration longer.

For that, I design a piece, that a friend (thanks Jean-Pierre) had turn in a PVC cylinder. This part, which is placed on the inner, position itself in the nozzle at the output of the launcher.

To prepare the rocket for the launch, I slip the cap (red on the picture) onto the 20 mm diameter pipe, then the Le montage de la fusée sur le lanceur consiste à poser le bouchon (rouge ici) sur le tube diamètre 20mm, then I put the nozzle reducer onto the inner pipe.

Then I screw the bottle in the cap and shut the release system.

Note that the rocket shown on this picture is not adapted to this kind of nozzle, because when the T-Nozzle is put in position, it stays water inside the rocket. Thus its center of gravity is low. The stability of the rocket will be correct only if the center of pressure is roughly a diameter under de CoG. So, it's necessary to have big fins and as low as possible. I haven't find the good solution yet, but I'm working on.