Help with servo-release parachute deployment!

[user 46401]

Hi!
I'm designing my first rocket, from scratch and it's using a pi as a flight computer.
I need help with parachute deployment- I'm going to be working with a nosecone that is held in by a servo tab, so when apogee/lack of thrust isn't detected, the servo tab is moved out and the door is opened.
I don't know how to get the means to either design, or rescale a 3D printing STL/CAD work to either add the door, or rescale to the appropriate nosecone diameter. I am terrible with CAD lol.
Does anybody have a 9cm nosecone STL file with a parachute door, or know how I can modify a different diameter file to get it to the right size?
That or any non-charge-based parachute deployment systems.
Thanks!

 

[Voyager1]

You might find inspiration on this site:
http://www.aircommandrockets.com/construction_7.htmThis is a servo-based side-deployment method for a water rocket, but it might give you some ideas to adapt to your particular application.