Open Rocket's stability on varying diameter

[Murdnunoc]

With this varying diameter body, Open Rocket uses the max diameter to calculate stability.
From the real world, could the average diameter be used to calculate stability?
I'd love it if the rocket would be stable getting the 1 Cal from the average diameter, as it takes quite a bit of nose weight to get it to 1 Cal using the max diameter.
The outer shell is too fragile to support a string for a swing test.
The rocket has flown at Cal using max diameter, but it sure is heavy.
Thanks for thoughts,
Darren

 

[Nytrunner]

Try aiming for 10-12% rocket length

 

[Murdnunoc]

Try aiming for 10-12% rocket length

That would cut the CG/CP spacing in half and save me a couple ounces.
I'm new to rocket aerodynamics, so it'd be a leap of faith!

 

[Reinhard]

Try aiming for 10-12% rocket length

10-15% is what I'm aiming for (based on a number quoted from an old East German artillery handbook). This rocket should fly quite fine, assuming OR is able to accurately model the CP on this exotic geometry.

Reinhard

 

[Nytrunner]

That number comes from sounding rocket design, so take with a grain of salt and reason (this is not exactly a sounding rocket shape lol)

Openrocket does finky things with boattails (reducing transitions)

edit: Just read Reinhard's post. Sounds like the east german's and early nasa were on the same train of thought

 

[Murdnunoc]

Well, Commie NASA sounds trustworthy enough!
I'll pull some weight out of the nose, which will get a safer launch on E20, which is at borderline off-rod velocity now.

 

[Nytrunner]

I used to like flying borderline motors, but have been leaning more towards the "In thrust we trust" mentality lately.

If the motor isn't a clear good lifter for a rocket, I'll choose another and use a lighter rocket for that motor.

Either way, have fun!

 

[SpaceManMat]

It a good idea to put unusual and unproven designs on the next pad out just in case it’s not stable.

 

[Murdnunoc]

With 2 oz. weight reduction, it puts the E20 at 33mph off the rod, versus the 31mph it had before. Worth a shot for me, since actually seeing the flight is most of the fun with this rocket.

 

[Nytrunner]

45 ft/s isn't bad

Take video!