A recent issue of Sportplane or Kitplane had an article on an Eracer.  The
builder placee vortex generators ahead of a NACA cooling inlet which increased
the air flow.  I have an application for my craft, and I'm trying to find out
the construction dimensions and proper attachment angle.  If anyone has that
info, I would appreciate it.

 

 

Ridge,

 

Jack is in the hangar behind mine.  Because of poor boundary layer characteristics, the vortex generators allowed for the reattachment of the air flow - thus making the NACA duct work a bit better.  This is not the only answer as he has added peculiar high ridges to the ducts to force the air to tumble over and into the ducts.  Again, this is done because of the early detachment of the air flow - we have no idea how much drag has been added.  Also, remember that most of his cooling improvements come from the use of augmenter tubes - thus drawing in cooling air in -- note that the NACA provide very little "pressure" to the incoming air in his application.  If you want to improve the air flow to your NACA ducts, you might want to examine the air flow with some oil streaks - this could very well indicate where to place "Vortex" generators to help.  You might need to also learn how tall the generators have to be to engage actual flowing air.  Generally 30 degrees to the airflow line will create appropriate vortices.