Labels 4 Mnementh including the point at which smoke may begin .
Mooning shot for Specmaster. Short riser block/mount for the pair of fans to be made when they arrive.
That's a good mooning shot, good air flow assured [emoji16]
In all honesty, bean... looking at your stack over my morning cuppa...
With the airtight box it's attached to, that single fan you have in this pic, mounted airtight against half of the stack, would be about PERFECT for max cooling capacity from that heatsink. Something PC weenies often overlook in their quest for crazy thermal solutions, is that it takes TIME for air to collect heat from a heat exchanger, no matter which way it is exchanging heat. They always try to make things with more fans, faster fans, less obstruction... but in terms of consistently pulling heat away from a metal mass, slow and steady wins the race.
You want good volume of air, but slow velocity with finned aluminum. One fan, pulling down half of that stack and then forced to exit out the other half, would be VERY effective in this application. With that stack, it will be VERY hard to get venturi-effect cooling, and you cannot get the velocity needed forcing the air to shift direction 90° like you're talking. I would use the fan you have there, cut a divider sheet out of aluminum flashing or even cardboard, then slip it between the fins at the middle of the stack to divide it in half. Then make your adapter plate out of 3DP (I know you're already thinking about how to do it
) so it fits airtight against one half of the stack pretty much like seen here in your photo.
If you make it from AL flashing, just extend the divider high enough to come up the side of the fan and you'll be 98% there; a little silicone RTV sealer around the few corners & cracks and presto; all done, ready to enjoy!
Bear in mind that good cooling doesn't necessarily meant your heatsink never gets warm; quite the opposite. You want to place the point where conductive heat exchange from the covalent area turns into convective cooling from the fins somewhere in the center of the metal mass. This is done primarily by adjusting the air velocity rather than air volume.
Worst case, you can always go dual fans in a push/pull later or, if you must, cut the crap out of that casting for a dual pusher arrangement... if you must. But, speaking from considerable experience hand-fabbing such stuff for kicks, I really think what you've got in that picture is already a kickass solution that you should at least try out before fucking up what you already have.
Okay, I've made my suggestions... have fun.
mnem
Also, remember the monkey puzzle.