Calculating The Stability Of Your Model Rocket
There are many different factors that help to determine the flight capabilities of model rockets. For a model rocket to be considered stable it must be able to resist the drag coefficient in order to reach its maximum altitude while in flight. If a model rocket is unstable there is the chance of serious injury occurring. You should always find out roughly how stable your model will be before launching it.
There are a few different ways that you can do this. One method involves using the center of gravity and center of pressure. There are a few things you will need to gather to be able to figure these. You will need some scissors, a pencil, a ruler, some string and a piece of cardboard. The first step will be to locate your rocket's center of gravity. The center of gravity is the specific point that your rocket rotates around.
To find this you will need to tie the string around the middle of the rocket. You can then begin to move the string back and forth until you find the point at which it is able to balance horizontally. Once you find this point you should make a note of it. Next you will find the center of pressure. This is the point on the rocket that is affected the most by air pressure or drag. Take the piece of cardboard and trace the profile of the rocket on it. Cut the profile out and balance it on the edge of the ruler. This will give you the rough center of pressure.
Mark the balance point on the cardboard profile and you will then be able to make any adjustments necessary. The next step is to try a string test out on the model rocket itself. Tie the string around the center of gravity and then you can swing the model around in circles making certain not to let it go. If you have properly found the CG then the rocket will point into the direction you are swinging it rather than having a wobbling motion.
By roughly calculating the CG and CP in this method you can then begin to adjust your rocket design to lessen or change these values for a longer, shorter, higher or lower flight time or path. For those that have a love of high mathematics, there is a way to calculate the CP much more accurately called the Barrowman Method. This method involves a great deal of computations but this can be offset by finding spreadsheet templates online that are free and will calculate the CP for you with just a few inputs on your part.