Apogee 00524 Manual - Page 10

Browse online or download pdf Manual for Toy Apogee 00524. Apogee 00524 10 pages. Fin shape science experiment kit

Print Page

Suggestions for Your Fin Shape Science Experiment

How to Eliminate all the Variables That Could Affect Performance

The critical part of any science experiment is to eliminate

all that variables that could affect the results except the

one that you are testing. In this project we've tried our best

to eliminate most of the variables that could affect how the

rocket flies, but here are some other suggestions:

Variable: Fin Area

When we created the fin patterns, we used a computer

program to determine the exact surface area of the fin. We

adjusted the shape to ensure that all the shapes on the

sheets have the same area. If you decide to make your

own, you might have to use a CAD software to find out the

suface area of your custom shapes too. Make sure your

customized fins have a surface area of 4.09 square inches.

Variable: Fin Span

Another variable that people overlook is how far the fin

sticks out from the rocket. This is called the "fin span." The

fin span is critical, because it greatly affects the drag on the

rocket. Again, if you decide to create your own custom fin

shapes, make sure that the fin span distance is 2.5 inches

like the rest of the suggested shapes in this kit.

Variable: Rocket Lift-off Mass

One variable that we have not eliminated in the kit is the

mass of the rocket. As you can guess, the rocket that is

heavier is not going to fly as high as a lighter weight one.

Even though the fins have the same area and theoretically

they should have identical weight, the material they are

made from has an effect on the final weight. The reason

why is that balsa wood is a natural material and one tree

may be denser than another.

In addition, how you attach the fins to the fin can tubes

can also affect the weight of the rocket. The amount of glue

you put on when attaching the fins will vary slightly from one

fin to another.

Because of the varying mass of fin cans, we've included

in the kit a small amount of clay weight. Use the weight to

adjust the mass of the rocket prior to installing the rocket

motor.

Here's a hint: weigh all the fin cans separately. Find the

heaviest one, and put that one on the core tube with the

engine mount. Weigh it again and record the mass.

When you fly the other fin shapes, add a small amount

of clay weight into the payload tube so that the entire rocket

weighs the same as the heaviest fin shape. Between flights,

always weigh the rocket and add or remove clay mass so

that the lift-off weight is the same. This will eliminate the

variable of weight and make sure that you're only testing the

shape of the fin.

Also remember to use the same amount of tape to hold

on the nose cone and the fin can. It is recommended you

measure the length of tape, and use the same length every

time so any extra length of tape won't change the mass of

the rocket. We suggest 4.25 inches long.

Variable: Launch Angle

Eliminate this variable by always launching the rocket

with the launch rod pointed straight up. Don't angle it into

the wind.

Variable: Weather Conditions

This is a hard variable to eliminate. The only way to do

that would be to launch all the fin shapes at the exact same

time so that they are all affected by the same weather (wind,

temperature, humidity). This is a great idea, but it is a bit

impractical because it involves a lot of rockets flying at the

same time and much more sophisticated launch equipment.

The next best thing to do is fly all the rockets on the

same day. Hopefully that will reduce some of the variables

like temperature and humidity since they probably won't

vary much between one launch and the next.

The wind will vary between flights. You never know when

a gust of wind will come through the launch area and affect

the trajectory of the flight. Ideally, you want to fly on a day

with zero wind. If you have a choice, try to schedule your

launches on a calm day.

If there is any breeze, what you should do is fly the

shapes multiple times and average out the results. So if one

shape flew to 200 feet on the first launch and 220 feet on

the next launch, the average altitude for that shape is 210

feet.

But don't fly the same shape in succession. After each

flight change to a different fin shape. Why? Because that

will allow you to test other shapes when the temperature

and humidity are fairly consistent. If you fly one shape four

times in succession, it could be a long time before you get

to the next shape. In the mean time, the temperature could

have changed significantly.

Variable: Rocket Motor Performance

Unfortunately, this one is out of your control. Motors can

vary a little bit in how much thrust they produce. In order to

eliminate this variable, you'll need to fly your rockets many

times and average out the results. Don't just do one flight

per fin shape. The affect of the motor would be too signifi-

cant. The more times you fly the rocket, the better.

I hope this helps you with your project to find the best fin

shape. Please let us know how your experiment turned out.

www.ApogeeRockets.com

Page 1 0