[Amps] Force cooled heatsink aerodynamics

[Alan Ibbetson]

I'm planning on using one of these in my solid sate PA project

http://www.farnell.com/datasheets/17645.pdf

and I'm curious to know what is inside the box between the fan and the 
cooler matrix in the second "V" variant in the datasheet to give it the 
20% improvement in performance. They call it an "air flow chamber".

Has anyone had something like this apart? Is the 30mm deep box empty and 
just giving the airflow a chance to stop spinning so much before it has 
to enter the honeycomb? Or are there fixed blades which are shaped to 
guide the air, in the way they do with some gas turbines?

I am asking because the heatsink will be carrying a large RF voltage 
which I doubt the insulation on the low voltage fan can withstand, so I 
need some some sort of insulated coupling between the fan and heatsink 
anyway and I thought I might as well try to duplicate the manufacturer's 
metal one.

73, Alan G3XAQ