Hi All,
I’m planning my L3. I have a 4” fiberglass MadCow DX3 XL, and planning on using an M1350 motor.
However, this combo busts the altitude waiver, bottom line is that I need a planned apogee at about 11,000 AGL. Thought first about adding weight, but need close to 4 KG extra which creates other problems.
Based on earlier discussion, I’m thinking of adding a doubled fiberglass centering ring that sticks out an extra 1/2” and bolting that to the thrust plate — that way I can take it off for a higher waiver. That solution sims out to right at 11k; exactly what I need.
My question is how best to measure or simulate the stress/flutter on the protruding ring. Max velocity per OpenRocket is Mach 1.1. My intuition is that since the centering rings handle the acceleration forces from the motor without problem, they should also easily handle the aerodynamic deceleration forces.
I think it’s fairly straightforward to measure the aerodynamic pressure in free air, but that’s not the situation at the tail end of the rocket. Is it a valid assumption to say that aero forces would be less at the tail than in free air? I’m pretty sure the tail end wouldn’t see supersonic airflow since it’s most likely in the subsonic area behind the shock wave, in which case the pressure in free air would always be greater.
Any ideas or suggestions greatly welcome!
Thanks,
Bill
I’m planning my L3. I have a 4” fiberglass MadCow DX3 XL, and planning on using an M1350 motor.
However, this combo busts the altitude waiver, bottom line is that I need a planned apogee at about 11,000 AGL. Thought first about adding weight, but need close to 4 KG extra which creates other problems.
Based on earlier discussion, I’m thinking of adding a doubled fiberglass centering ring that sticks out an extra 1/2” and bolting that to the thrust plate — that way I can take it off for a higher waiver. That solution sims out to right at 11k; exactly what I need.
My question is how best to measure or simulate the stress/flutter on the protruding ring. Max velocity per OpenRocket is Mach 1.1. My intuition is that since the centering rings handle the acceleration forces from the motor without problem, they should also easily handle the aerodynamic deceleration forces.
I think it’s fairly straightforward to measure the aerodynamic pressure in free air, but that’s not the situation at the tail end of the rocket. Is it a valid assumption to say that aero forces would be less at the tail than in free air? I’m pretty sure the tail end wouldn’t see supersonic airflow since it’s most likely in the subsonic area behind the shock wave, in which case the pressure in free air would always be greater.
Any ideas or suggestions greatly welcome!
Thanks,
Bill