with this version
OS: Ubuntu 20.04.1 LTS (XFCE/xubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.24847 (Git) AppImage
Build type: Release
Branch: master
Hash: 20e756306d9aa624fcbf465f0345d721673ce720
Python version: 3.9.2
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.1
Locale: German/Germany (de_DE)
the file is even larger after the deletion and recalculation
but with this version of realthunder
OS: Ubuntu 20.04.1 LTS (XFCE/xubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 2021.504.24301 +3511 (Git) AppImage
Build type: Release
Branch: LinkStage3
Hash: b8cd87c34a66a8f7a8177f483cebf79e29273813
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.1
OCC version: 7.4.0
Locale: German/Germany (de_DE)
the file is smaller even without the deletion process. here is the file