Question about Open Rocket and transitions

[SDramstad]

I am playing with a design that has a 2.6 inch nosecone and a long (18 inch) transition out to a 4 inch diameter 4 inch long body tube. What I am seeing in open rocket is the stability of this rocket goes negative with the long transition but positive if I make it a 4 inch body tube instead of the transition. This is counter intuitive to me. The taper should move the CP toward the back not move it forward. Can anyone explain this to me?

 

[SDramstad]

@neil_w Any Ideas? Aren't you the Open Rocket guru?

 

[SpaceX76]

Could you post the .ork file.

 

[neil_w]

Hmm, I just did a quick experiment and wasn't able to reproduce what you're describing, probably because I'm not doing it right. Posting the ORK file would (as always) be great, but also just screenshots of the different configurations would be ideal.

 

[SDramstad]

Now I cant get it to repeat. Weird......

 

[SDramstad]

Maybe the nose cone weight changed enough to move the CG back