Paul  I respectfully disagree. One of the biggest troubles for some
systems, like  a 20B
RV-10 will be the lack of a CS prop. That is saying that a fixed  pitch
won't work at all
but carrying enough pitch for cruse/top speed  will lengthen takeoff
distance by a
significant amount.
Bill  Jepson

Not if you start with a p-port 3 rotor. How many RV10 out there  have 375
HP?

Paul Lamar

I also disagree about the need for a  PRSU that will handle a CS prop, but
when I looked at the Variprop website,  its only rated for 300hp. If a NA
20B P-Port will make 375hp (not sure  about that), I'm not sure it would
hold
up. Certainly the 20B P-Port will  make more that 300 hp in any case. I
think the greatest need is for a PRSU  that will take a CS prop. At this
point, everyone just has to settle for  what we can get and hope for a new
product!!

Don

Don,
I'm  in total agreement with Paul that a P-port 20B will make major HP. In
a talk  with
Daryl Drummond he said you would have to intentionally hold it back to
make only 300!
I agree that it would be best if the CS could be a light  one. Senstitch
(sorry I never
could
spell their name right) Is doing a  new all composite CS. Egg Subaru has
been selling them.
They have several  blade configurations. Just a possibility.
Bill Jepson



I sure hope your right because I'd love to pull 375 hp without a  turbo!!!!
I also agree that lighter is better when selecting a CS  prop.  I thought
we were debating the need for a PSRU that would handle a  CS prop -vs- one
that just takes a fixed pitch prop (ie. which is more  desperately needed by
the experimental aircraft engine community).  I  vote for the PSRU that can
handle the loads placed on it by a CS Prop.  It  that existed, I'm betting
that many of us would no longer be buying fixed pitch  props for our rotary
applications!!
Don

We tested two P-port engines on the Mazdatrix dyno. A 13B and an RX8. They both pulled about 250 HP or more at 7500 RPM. That is 125 HP per rotor times three is 375 HP.

P-port 13B engines back in the 1980's were getting 300 HP at 9000 RPM.
That is 150 HP per rotor. 450 HP for a 3 rotor. The Mazda Lemans engine got 690 HP
at 9000 RPM. That is 517 hp for a 3 rotor version. The current 3 rotor RX8 in the Rolex GT class are getting about that amount of HP before the rule limiting the RPM to 8000.

None of these engines had turbos. Two rotor turbo engines have made 800 HP. A 3 rotor turbo engine makes about 1400 HP. A four rotor turbo engine has made 1800 HP. All more or less stock Mazda parts.

Don, You must start reading the web site.

If  you have a lot of HP the airplane gets off the ground faster and climbs out faster. You have less of a need for a constant speed prop. The main reason for a constant speed prop is to enhance the thrust during the take off run and climb out.

                      AIRCRAFT SIMULATION V71
                    Copyright June 1997 Paul Lamar
                    paul-lamar-la@worldnet.att.net

                                     Gross weight  1500
            Equivalent square feet with gear down.  4
Equivalent flat plate in square feet with gear up.  3
                  Initial static thrust in pounds.  500
            Pounds per mph that thrust is reduced. 1.00
                                         Wing span  25
                                         Wing Area  100


Time   Net     Accel   Velocity   Distance    Cl     HP Out   Excess   Climb
Sec    Thrust  FPS^2    MPH        Feet       Req.   Total  HP Avail.  Pot. FPM
 0.63   500   10.66       5         2      292.18       6       6      0
 1.32   499   10.64      10         9       64.50      13      13      0
 2.01   498   10.62      15        21       27.59      19      19      0
 2.70   496   10.58      20        39       15.25      26      26      0
 3.40   494   10.53      25        61        9.62      33      32      0
 4.10   491   10.47      30        89        6.63      39      39      0
 4.80   487   10.40      35       122        4.85      46      45      0
 5.51   483   10.31      40       161        3.70      53      51      0
 6.22   479   10.22      45       205        2.92      59      57      0
 6.94   474   10.11      50       254        2.36      66      63      0
 7.67   469   10.00      55       310        1.94      73      68      0
 8.41   463    9.87      60       372        1.63      79      73      0
 9.16   456    9.73      65       440        1.39      86      78      0


My C182 has a constant speed prop and I can barely measure the difference in MPG.
It helps greatly in taking off however as I only have 230 HP for a 3000 pound gross weight airplane. You guys will have 50% more HP for about the same gross weight.

Paul Lamar