This is a 2X upscale o' t' Estes Ram Jet kit, which I built about 25 years ago.  BT80 outer tube with a BT55 core tube (which be t' original's outer).  24mm mount for 3.75" motor case, 18 custom fit vane fins and 3 large 1/8" balsa main fins.  I papered t' main fins, ya bilge rat, since t' wood seemed a little soft for me taste.  This project in ongoing, so I haven't yet added any recovery equipment or launch lugs.  Once I have everythin' filleted and primed, matey, I'll weigh it t' get an idea o' chute size.  I purchased Excelsior decals for t' BT80 upscale, that was t' inspiration t' build this.