<< A wad of drinking straws (with the jackets removed :) is a good way to straighten out your airflow.>> Way ahead of you on that! I've been making small honeycombs out of straws using CA glue to see if that would work, and if I think I have the patience to make a unit out of hundreds or maybe thousands of them. It looks doable. << Put the fans on the outgoing side for best straightness, though it will lower the air pressure in the box. >> Yep, our wind tunnel will suck. That looks like the best thing to do. there would just be too much turbulence with an axial fan ahead of the test section. A centrifugal blower was considered, but that thing would probably be much bigger, heavier, and more oddly shaped than a fan. I've wondered if we'd be able to get a good current going through the test section, but with a 24" industrial fan I think we'll do alright. I'll be sure to keep the list updated, as I still hope to do data logging with PIC's, which even keeps it on topic... :) -Tony -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads