Back in 2012 the user "Mozzie" (https://www.planetminecraft.com/member/mozzie/) uploaded a map called "USS Excelsior, USS Enterprise & USS Reliant - New 1.7.4 update" (https://www.planetminecraft.com/project/uss-excelsior-uss-reliant-abandoned/). In my opinion these were the best minecraft star trek ships ever made. The scaling is perfect too, not to big or small. Well anyway over a year ago the download link died and the map was lost forever, until today. I am re uploading Mozzie's minecraft star ship enterprise and relent. I take no credit for this of course I am doing this to save this amazing map from being lost forever. I have modified the ships a bit to fix bugs from the conversion from 1.7 to 1.12. So yes these should work fine in 1.12. Again I take no credit for this.
I also recommend you play with your render distance somewhat high.

The download includes a world file with the enterprise and reliant plus the schematic files for just the ships.