I recon, initially, only 0 carbon is opposing torsion anyway. This is for the first torsion angles. 0/90 in a sense of 0 being the mast length.
Only if there is carbon placed on extreme low angles, it would kick in initially. But does anyone build in such a way? So, we can simplify and say the 0 degree carbon is a low angle.
And this is why, initially, some masts are stiff, coz they have heaps of 0 (uni). But, passing a low degree in torsion will snap mast on the micro scale. After than, will snap big time. However, we are not passing this point when riding. For example, a concrete beam is stiff, but will snap big time in torsion - when you reach the torsion strength. Again, it feels stiff right?
Even if you build only with UNI, it will be stiff. It does not matter on which 15/30/45... angle you place your carbon coz you'll never ever reach this angles initially. But, they are important if and only if we pass low angles.
What it does matter for torsion, as you know, is a SPIRAL reinforcement in high angles (in torsion direction, it would be almost 90, lets say 89 initially, than 88...). But we can't wrap the mast in spiral motion. However, big sailing masts are wrapped this way. Even windsurfing masts are. This is where biax kicks in in HF mast.
So, if we have all degrees between 45 and 90 ( biax covering degrees from 0-45), than the mast would be super strong in torsion. That is 45 layers, each side. Plus UNI for bending.
Did not read the above post before posted.
I take back wraping a sailing mast in spiral according to this:
https://carbonsugar.com/construction/wh ... -breaking/
However, that's from 2007...