Archive for July, 2008

Rocket Nozzle How To

Thursday, July 17th, 2008

I have created a guide on how to create the rocket nozzles we used on our recent rockets:-

Possible reasons for Louie veering off course

Saturday, July 12th, 2008

Over the last few days I have been watching the videos from the competition over and over to try an get to the bottom of Louie veering off course at the start of the launch. I have also been discussing the problem at the Yahoo Water Rocket mailing list (see:

One thing is for sure, that the rocket is stable in flight, its centre of gravity is well above its centre of pressure. Also the rocket only seems to be unstable at low velocity’s, this confirms that once sufficient velocity has been achieved and drag is being generated by the fins, the rocket is stable.

Various reasons have been suggested for why the rocket is unstable at low speeds, including cross winds, not enough pressure, a bent rocket or a off centred nozzle.

The low launch pressure means that the rocket will have low take off velocity so the fins won’t generate drag for the first several meters of flight, during this period the rocket will be very susceptible to external forces that may try to steer the rocket off course.

Of the remaining causes I suspect the most likely one might be the off centred nozzle. I can’t confirm since the nozzles have since been removed from the rockets and some unfortunately lost.

One very good suggestion was to angle the fins along the vertical plane by 5 degrees, this should put the rocket into a spin thus canceling out any off centred nozzle or bent rocket. The only thing that remains to be seen is if the rocket will be traveling fast enough for the fins to make the rocket spin. I intend to test this next week and report the results.

Some pictures from the competition

Sunday, July 6th, 2008

Video from the competition

Sunday, July 6th, 2008

I know its been a long time since the competition but I have been busy with so many things, I haven’t had a chance to update the site. I should now have a couple of weeks free to start working on the rockets again. First task I have set myself is to start uploading some of the pictures and videos from the competition last month.

Below is the video of Louie taking off and then veering to the right and heading into a load of trees.

I was quite disappointed that it didn’t launch straight, I intend to do some slow motion replay to try and work out what happened.

If anybody has any ideas why it did that, please let me know.