11yr old science fair prj - weight placement

My 11 year old son just had his science fair project approved. His school requires him to follow the scientific method but only 2 months to complete the project.

His project is about the stability of flight being affected by the placement of payload. He wants to have some sort of dense weight placed on the rocket and to repeat the experiment with the weight being in 5 different places.

One part he didn't think through was what kind of weight to attach and how to attach it.

I am letting him think this one through for awhile but I would like to have some worthy suggestion in case he doesn't come up with one.

He is looking to build a single stage rocket. Probably about 18 inches.

Any recommendations or thoughts? I could really use some help on how to guide him.

Many thanks.

Stephen

This could be similar to attempted projects I've seen locally where a student thinks they can launch a rocket or series of rockets and progressively either remove fins or move them up the rocket.

This teaches nothing and there is no theory to prove or new area to explore. Stability is a fundamental of model rocketry. Testing what makes a rocket go unstable is DANGEROUS.

Use the known laws of stability and test some other variable such as drag effects of fin size shape or thickness and airfoil. Never exceed the max liftoff weight of a motor.

I appreciate the response and I am now concerned that you said this is dangerous. I will have my son talk to his teacher and hopefully they will allow him to change his project. They approve the project by the student posing a scientific question without doing any research.

I am very new to model rockets, how would you measure the drag if he were to change fin size etc... ?

Thank you for your quick response and warning about it being dangerous.

doing this with an actual rocket (low power) can be difficult to measure since there are other factors that will have a greater influence on altitude(wind and variations in motor thrust)...but one could use a rocket with a payload section and a low cost altimeter like the altimeter 1 (or two) by 'jolly logic'. I gather from my reading that, the main goal is the methods one follows to (hopefully) get the data. figuring out how to change the fins and the number of test flights per fin type. to get data with out spending a fortune in motors...I would suggest a normal fin followed by an exaggerated draggy fin (mayhap a slip cover made from 1/8" Styrofoam held on with tape). of course a virtual rocket flight would give you some additional data points ('Open Rocket' is a free rocket design software that lets you design and simulate flights). hope this helps
Rex

Build several similar rockets and use an Estes Altimeter to measure the altitude of each flight.

Each model will have different fins. One 'normal' with a nice airfoil shape (you'l need to sand them) and another with 'normal' fins and no airfoil. Then another 2 can have fins twice the size (which makes it more stable, but should add drag) with and without airfoil.

So, everything is identical except for the fins so you are measuring the effect of one single variable.

Also, you need to select a motor that will allow the model to go up and reach apogee before ejection for all flights. This will ensure that you reach the actual apogee and are not ejecting "on the way up" before reaching the peak altitude. You might be able to do this with an average model and B6-4 motors but you might have to get B6-6 motors if the model is too lightweight and high performance. Try to get motors with the same date code on the label to minimize any motor variables from batch to batch. Teachers are impressed when you point out how you try to identify all possible variables and eliminate them so that you are indeed measuring only one variable (fin drag in this case).

https://www.estesrockets.com/002246-estesr-altimeter

https://www.estesrockets.com/002422-reflectortm

https://www.estesrockets.com/media/instructions/002422_REFLECTOR.pdf

stephenl said:

I appreciate the response and I am now concerned that you said this is dangerous. I will have my son talk to his teacher and hopefully they will allow him to change his project. They approve the project by the student posing a scientific question without doing any research.

I am very new to model rockets, how would you measure the drag if he were to change fin size etc... ?

Thank you for your quick response and warning about it being dangerous.

Click to expand...

For extra points (and more time flying rockets ) he'll need to do more than one flight in each configuration. Take the average of the altitudes measured for that configuration. This should reduce the effect of variables such as exact motor performance, drag on the rod, and what the air is doing when the rocket launches.

a thought that occurred to me, there is one aspect of rocketry that gets less attention is the recovery aspect. specifically parachutes. a study on the effects of shape on descent rates could be useful, also can be done indoors and cheap . all one would need is a cheap trash bag or two(the cheaper ones are better for chutes than the expensive bags), some thread and a bit of tape. add about 14g of weight... to get one started a square 12" x 12" has the same surface area as a circle 13.5" in diameter.
Rex

Rex R said:

a thought that occurred to me, there is one aspect of rocketry that gets less attention is the recovery aspect. specifically parachutes. a study on the effects of shape on descent rates could be useful, also can be done indoors and cheap . all one would need is a cheap trash bag or two(the cheaper ones are better for chutes than the expensive bags), some thread and a bit of tape. add about 14g of weight... to get one started a square 12" x 12" has the same surface area as a circle 13.5" in diameter.
Rex

Click to expand...

Rex has a great idea. You would want a lot of altitude to give a long drop time, thus indoor might be a challenge, though it does remove wind as a variable. Reason being, is 1% - 10% of a 1-2 second drop is harder to measure than 1% - 10% of a 30-50 second drop. Plus, rockets just make it more fun (IMHO).

A huge thanks to everyone for the ideas. He is going to talk to his teacher tomorrow to switch the project. Last year's science fair had the challenge of accurately measuring something over a small period of time. we tried everything from stop watches to the camera on an ipad. Ultimately we found a kit online with a led display that measures to the thousandth of a second and you can rig all sorts of ways to start the timer and end it.

Thanks again.