What's the best way to create an average curve from this closed curve?

Hi there. I’m currently busy on a project and I cant figure out how to find the average curves for the following closed curve.

This is my closed curve. I need the average curves of the 3 “blades” to also meet at the middle of my closed curve at 0,0.

The blue is my best attempt that I created using tweencurves. However the average curves don’t meet in the middle they stop just short, and extending the curves doesn’t seem to work correctly either. What techniques/commands can I use to achieve my desired result?

Here is the Rhino file:

Average Curve.3dm (2.0 MB)

Thanks in advance!

Hi Neil - I don’t know if you can do better than the tween to get about the right curve and then make your own clean curve on top of it.
I’d be inclined to split the inputs up in here somewhere:



Thanks Pascal appreciate it. I thought there might not be better way to do it than what I did before, but just wanted to make sure.