That conclusion was based on measurements of the blade angle, prop rpm & airspeed and calculating angle to airflow along with the assumption that stall would occur when angle exceeded 15 deg.  Then this SWAG was boiled in a pot with observations of how adversely the cooling was affected by the IVO (stalled air blocking inlets).

 

In other words, it's just my best guess.

 

One more  observation on the RD-1C testing.  After about 5 hours of flogging my 89 vintage 13B at engine speeds up to 7050 rpm, I noticed that the oil level was down 1/2 quart.  Had never seen a detectable drop in level before.

 

Tracy (still doing plastic surgery on the RVotter)

 

 

Hi Tracy,

Having an Ivo myself, it interesting that you could estimate 21" of stalled airflow..  How'd ya do that?  What's a cuff? 

Tommy<><

 

 I estimated there was a 21" diameter of stalled airflow on my IVO.   You might try making cuffs for that area.  That's what I'm doing now on my Performance Prop even though it was much better at the root than the IVO. 

 

Tracy (Yuck!  fiberglass)