While they appear to be very similar in size the new motor should provide a 33% increase in total impulse. Once the nozzle was fabricated, I was pleased to find out that it actually weighs less than the nozzle from the 3.5" motor. Unfortunately, the shorter nozzle also means that the boat tail is going to be shorter, but I am considering extending it beyond the nozzle exit a bit. The previous flight got to 14,400' and I'm hoping this flight can get close to 18,000'. I am planning on adding another on board camera, or adding a mirror to the existing camera bay to shoot straight down. Maybe I'll do both.
Here are the basic designs of the new motor and the previous motor.
The new nozzle design.
I did a 3D model of the nozzle. This is the first time that I've done this and it was very helpful to be able to rotate around the piece before starting to actually cut metal.
Here is the finished nozzle. It looks just like the 3D model.
This illustrates the basic layout of the motor in the camera rocket (well minus the camera). When I finish the boat tail and decide exactly how I'm going to lay out the cameras for the next flight, I'll do a new illustration.