ps. Would someone = precisely define=20 "pressure recovery" for me?

Regards,

Tommy = James<><

Cool in NC, Hot in FL

By pressure = recovery I mean=20 the 'recovery of the dynamic pressure due to the forward velocity = of the=20 airplane, this is what is measured by the airspeed indicator. = There is a=20 formula to calculate dynamic pressure at any given airspeed. = Don't=20 remember it off the top of my head but a web search on "Dynamic air = pressure"=20 will no doubt turn it up. I recommended the ASI instrument = because it=20 takes all the formulas & math out of the measurement. = The=20 pressure goes up as the square of speed (really fast). =20

Example: = The dynamic=20 pressure at 120 mph is 7.6" H2O. Before doing a bit of inlet = work, my=20 right side rad only had around 3.5" pressure at this speed. The = left rad=20 had 8.1" (Super good, got a .5" boost from prop blast). A=20 slight reshaping the right side inlet boosted it from 3.5 to = around=20 5.5 . Doesn't sound like much but remember that = the=20 back side pressure was around 2" which meant that the differential = pressure=20 across the rad (front to back) was only 1.5" By raising the = front side=20 to 5.5 the differential pressure is now 3.5" (more than = doubled!). =20 5.5 is still not great so I'll be doing more work on the inlet to get = it=20 closer to what the left side is getting. I'm explaining = all this=20 in inches of pressure because Paul insisted on using all those water=20 manometers when we did the test. Couldn't fly faster than 120 = for the=20 test because it would blow the water out of the manometers if I = did.=20 Gets much simpler with the ASI instrument.

Keep in mind that = the test=20 only gives you the raw data. Interpretation is still up to = you. =20 For example, Paul Lamar concluded that the right thing to do was to = reduce the=20 back side pressure on the rads (using a cowl flap, louvers in cowl, = etc) since=20 he considers the 'right' value there to be zero. I had the = opposite=20 conclusion.

Here's the thing = that makes=20 it confusing. If you look only at cooling results, Paul = was=20 right. I could have gotten equal or better cooling improvement = by using=20 a cowl flap. BUT, this improvement comes at the expense of = added=20 drag, especially at cruise & top speed (racing). By = improving the=20 pressure recovery instead, I got the improved cooling with = almost no=20 increase in cooling drag. This is the ultimate goal in aircraft = cooling=20 design.

Tracy=20 Crook