3D Printing 3D Printed Sentinel - Which motor?

[kmancali]

Hi, I recently found this 3D printed Sentinel model, which I printed upscaled to a BT-55 size. I weighed the entire thing and it comes out to 4.7oz (133g). I'm wondering if I could go with a D-12 motor, or if I'd be better off with an E-12 motor? Any thoughts? I can share more info if needed.

 

[frogglicker]

Good morning. I looked at the model (really cool design) and it appears to be flyable, but I, personally, would sim this in OpenRocket or RockSim before attempting it. The model maker pushed this before testing, so now you're the Quality Assurance team for him, and that can be sketchy. Just be careful.

Disclaimer: All of this is based on your data, data from the model designer's model page, and very preliminary OpenRocket sim. Nothing here is gospel.

A quick and dirty sim (see attached), and both motors appear to be adequate:

• D12-7: Ave. thrust ~ 10.4N = 7.97:1 Thrust to Weight with ~1,097 feet apogee
• E12-8: Ave. thrust ~ 11.2N = 8.58:1 Thrust to Weight with ~ 1,724 feet apogee

Your milage may vary.

This is only a gross estimate, and I wouldn't trust this alone. I would suggest that you use the attached sim for this rocket using OpenRocket -- it's free -- to get a better feel for how the rocket is going to behave. Regardless of of motors, this rocket sims very over-stable, so it will most likely weather-cock, and it's best to test this with a lot of open space.

Good luck!