Excuse my awful English. I find the center of its block too fine. I have built one similar but without helix.
More details can be seen in:
http://www.arkania.org/~jordimarch/i...ewlang=spanish
I don't have elements for of carrying out good mensurations.
36ºC cpu
21ºC atmosphere
measured with MBM 20 minutes CPU-Burn ECSk7s5a XP1800@1643