A square law function curve plotted on these charts will show the
effect of prop load. Prop load HP is at least a square law and maybe
as much as a cube law. A series of these curves overlaid on these
charts could represent different prop pitches.

Paul Lamar

Hi Paul,

If you have any idea what formula to use, we can put it on the charts as
well.  Here is an example where I added (arbitrarily) y=6*x^2 and
y=7*x^2 curves as examples.  I also cut the HP in half so you don't have
to.

Bob White

--
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (soon)

Not what I had in mind. You start at zero RPM and zero HP and pick a number K that
when multiplied times RPM squared generates  a HP consumption curve that intersects
the HP peak on these curves. Lets say K is 0.000005102 or 5.102 times ten to the minus sixth
multiplied by 7000 RPM squared or 49,000,000 will equal 250 HP.

Prop load = K Times RPM squared. Dithering K a bit up and down will plot a series
of closely spaced curves on either side of the HP peak. these will then
represent fixed pitch props with slightly different pitches.

This is coming in from the back door as we lack HP consumption curves for
most available props.

Perhaps Vance can supply us with actual prop HP consumption curves
as a function of RPM, pitch  and diameter. That will allow us to pick a prop
that will match the HP available from the rotary engine and or tailor
the HP available to suit individual needs.

Paul Lamar

This chart from Donald Crawford's book  "A Practical Guide to
Airplane Performance and Design" is close to what we are looking for.
It illustrate how changing the pitch can alter the HP consumption
of the prop while keeping the diameter constant.

Paul Lamar
 
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