PreComp oddity

Dear all,
this is my first post about PreComp so forgive me if dummy questions will follow.
I’ve seen other posts in this forum about PreComp and also a clear statement on the download page about a not further specified bug.

I’ve layed up a quite complex blade (>30 sections with uni, bi, multi axial + gelcoat + foam core) with 2 webs then I went down experimenting some mods to the original number of webs, section chord length and layup.


  • if I reduce the number of webs on a section, no change in torsional stiffness is achieved (that means “exactly the same numbers for GJ!!!” up to the precision printed out by PreComp); even if the blade section drops from 3cell to 1cell(no webs), GJ is still the same.
  • changing chord length or layup affect stffnesses, both axial and torsional, as expected

The behavior pointed out first is out of my expectation; I recall from studies that torsional stiffness generally increase as the number of cells on a wing section increase.

Am I wrong? or is that torsional behavior related to the bug I found on the PreComp page (otherwise, what is that PreComp bug about)?

Any suggestion about the problem is appreciated.