Welcome to XROX Aerospace The sky is not the limit!!
Welcome to XROX Aerospace The sky is not the limit!!
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MK3A Rebel Stability

Barrowman Kit MK3A Rebel RockSim Stability

I have had a few people express concern about the small size of the fins on the MK3A Rebel.  The design of the Rebel does have smaller than normal fins for a model rocket.  Traditionally, model rockets have used large fins to move the model's center of pressure as far behind the center of gravity as possible, which keeps the rocket stable.  The MK3A Rebel uses a variation on this design by adding a modest amount of weight in the nose and a long body to move the center of gravity forward.  Using these design features instead of large fins, the rocket is still ensured to be stable and provide a unique looking model rocket kit.

A couple of other notes.  Because the nose is 3D printed, it incorporates the additional weight in the design so that no additional materials need to be added when building the kit.  This simplifies assembly.  The nose is designed to weigh 1 oz.  The 3D printing process is able to maintain a tolerance of +- 0.1 oz.

The MK3A Rebel has a static stability margin of 1.72 calibers with a typical Estes D12 motor loaded. This is using the Barrowman method of calculating the center of pressure.  

Using the RockSim stability methodology, the margin increases to 2.58 calibers loaded with the same motor.  If you are curious and would like download the RockSim file, it is available here.  RockSim from Apogee Components was used for the initial design concept and to validate each design iteration until the final design came together.

Happy building and safe flying.


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The sky is not the limit!

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