Predicting Altitude and Speed vs. Grams of Weight

Here is an interesting collection of data from all my flights in the last few years.  It shows the various motors I've used, and the measured altitude with each flight.  The horizontal axis shows the weight of the rocket in grams (not including the motor's weight).

From this, you should be able to roughly predict the altitude your rocket will reach based on the motor and the weight of the rocket.  Of course this does not take into consideration the diameter of the rocket and the total drag it creates, but it does show the actual altitudes with typical models and the typical aerodynamic drag they produce.  These are all generally traditional rocket designs, nothing with super-heavy payloads or large wings or other drag-producing features.

Let's look at a typical motor, the B6-4, which is represented with an orange circle.  In the chart we see that a smaller rocket weighing only about 25-30 grams (1 oz.) has flown anywhere from about 450 to 550 feet.  That same motor in a heavier rocket of 80+ grams (about 3 oz.), has reached about 140 to 150 feet.  You can see that a given motor and weight will achieve a certain altitude range with not a lot of variation.  The C6-3 motors though (dark red triangles), do show a lot of variation, but of course this is for a variety of models.

So the weight of the model and the motor are a good indicator of the expected altitude, but it can also indicate the top speed of the model as shown in the following graph.

This time, using the motor size and the weight of the model, you should be able to accurately estimate the top speed of the rocket.  Let's say we are using a C11-5 motor in a rocket that weighs about 4 oz or 110 grams. The blue squares above 100-110 grams shows that these rockets reach about 100 to 110 mph.

Look way, way up above the 100 gram mark.  See that little blue square there?  That was the Vector Force, which I flew with a composite D21 motor. Yes, it reached a top speed of 282 mph!  Also notice the cluster of purple diamonds in the 30-40 gram zone.  Those little rockets have broken the 200 mph mark four times.

It takes a lot of time to add new dots to these charts, but over the last couple of years I have been recording all this flight data, and the charts will only get better over time with more complete data, but for the most part this is enough flights to give you an idea of how high and how fast your rocket will go, all you need is a good, accurate jeweler's scale (I got one for less than $10).