In a message dated 10/3/2010 2:04:01 A.M. Eastern Daylight Time, echristley@nc.rr.com writes:

    Has there been a compilation of data from folks spinning various
    sizes of fence posts with known HP engines? Results corrected to
    sea level standard day and all of that?
    Where did this come from?
    Thank you.
    Lynn E. Hanover

    I think I've been monitoring this list since forever.  I posted a
    message concerning this technique on Monday, September 11, 2006
    9:02 AM.

    At that time, I had lost the equation information, and I'm very
    happy to see them come around again.  More detailed equations are
    in the alt.rec.aviation.homebuilt newsgroup, if anyone can find an
    archive somewhere that dates back before 2006.  I'm pretty sure
    that it included correction for standard atmosphere, but I haven't
    been able to find it.

    LE Hanover wrote:

Here is a simple mechanism for reducing readings to some standard so that HP readings from any source (that had also been corrected to sea level standard day) can be accurately compared.
http://www.csgnetwork.com/relhumhpcalc.html
Way back when I had a Stuska Dynamometer I used big graphs to pull off the SAE correction data. No computers back then. I talked to "Ohio" George Montgomery (famous racer back then) who built a killer 33 Anglia drag car, about some problems I had getting past a development point. He said connect the dots on your SAE graphs and you will see that the published results are boxed in several areas. And so it was. 95% of those dots were on a straight line. So I got a 48" steel ruler and drew that line omitting the aberrations. No more problems. Thank you SAE.
I had my inlet air temperature bulb inside the air cleaner. I had a weather station beside the dyno. I had a wet bulb sling psychrometer. (because it came with the dyno) The kind you swing around your head. Now they are digital and just spin around a little handle. But, like building my first flow bench, I started getting smart real quick.
You may not know this, bet there is a solid silver fence post in the cellar at the National Bureau of Standards in a velvet lined box, In its center, an SAE-2 bolt pattern. kept at a constant 68 degrees. Its length measured twice per week with a CO2 laser. Cooler you know. doesn't change the length. You can see it with special permission. You must wear a moon suit, so the air in the vault room is not affected by your visit. No pictures please. The seemingly sharp edges actually have a radius. Verified by the annual electron beam sweep, and collection of Gamma ray backscatter.
It is worth the trip. The old guy who is in charge of that thing has the formulas in his head. He knew Eiffel. He instructed in a Jenny. Has a thousand stories, and loves to talk about planes.
Or, you could use fuel flow to calculate HP, and your fence post will not kill any bugs, or worse, and its lack of airflow will not overheat your engine. Spend the fence post building time working on the plane.
But I could be completely wrong.
Lynn E. Hanover