Group,
 looking to fit a prop to my P ported renesis and need to
 know what actual HP it will generate and not an enthusiastic guess.
 Would I be safe in aiming for 230 HP?  Apparently if the prop is
 too big
 nothing works, so smaller seems to be the aim.  Any suggestions ??  It
 will be a fixed catto prop, and as usual craig Catto has been caught
 many times before with HP in engines.  Actual HP not guesses required.
 Neil.

 What gear ratio is your gear box?

 If it is a 2.85 the prop will turn about 2600 and the engine
 will turn about 7400 and make 250 HP plus or minus 10.

 We need to get a group buy together and find somebody to make ground
 adjustable blades for a Warp Drive type hub. That way you can fine tune
 the pitch without buying a new prop.

 Paul Lamar

 Aren't there other factors that have to be right to get 250hp?  Intake,
 exhaust..  Can't go too big on the pipes, smooth transitions, no big
 restrictions, etc.  A bit of time on a dyno with the complete
 firewall setup
 from the airplane might be money well spent.  Compared to swapping
 props.

 As for the prop, if pitch or diameter are wrong, it's a bigger
 project to
 add material to the prop than it is to take it away. At least for wood
 props, it can be relatively easy to cut the diameter down, or even
 reduce
 the pitch to some extent.  Catto props are composite covered, so it's
 probably a bigger hassle to modify than for a straight wood prop.

 How about buy or borrow another prop to try before committing to one in
 particular.  If you could find a fixed pitch prop from a local Pitts
 or RV
 or Skybolt, you'll have something to use for a baseline. Many/most
 of those
 airplanes have 180hp engines.

 Another thought is to do prototyping with a wood prop of your own
 construction.  If you have gone to the effort of building a whole
 airplane,
 including the powerplant, building a prop may turn out to be that
 difficult,
 by comparison.  There were ads in Sport Aviation for doing this. And
 online.


 Matt-

 I am assuming (possibly incorrectly) that Neil is doing the p-port
 at least as well as I am doing it and he is using a 2.85:1 gear box.

 IMHO the best thing about a welded p-port it is hard to screw up but
 possible.

 I have taken the position that only a ground adjustable prop is worth
 fooling with provided you are not using a constant speed or in the air
 adjustable. I have come to the conclusion there are too many
 variations in aircraft drag to recommend anything else. The Warp
 Drive type adjustable
 pitch hub is becoming an industry standard as even Sensenich is
 supporting it.
 Unfortunately Sensenich does not yet have a blade suitable for our use.

 Randy told me today that Warp drive now has three different all
 carbon  blade designs. Ultra Light, LSA and high power. One of them
 is called Constant Speed Blade Platform. http://www.warpdriveprops.com/

 However I am not yet convinced the WD blade plan-form and twist is yet
 optimum for  the lower drag AC designs. That I why I would like to
 see some
 other companies get in the biz of ground adjustable.

 The high power to weight ratio of rotary powered aircraft and the
 excess length
 of most runways is why I think constant speed props are not worth
 the money.
 Set the pitch for best cruise and let the take off performance be
 what it is.
 We are mostly not building C182's here or cargo aircraft.

 IMHO pure wood props will always have less performance than a metal prop
 due to the lower modulus of elasticity wood. The high modulus of
 elasticity in
 carbon has yet to be taken advantage of. In other word when the tips
 are in
 the transonic range you want a thin blade as the drag of the tips
 becomes
 a significant consumer of HP. Therefor a stiff thin tip is an
 advantage.


 Paul Lamar



 I agree with Matt.  You should be much more conservative with your HP
 estimate for the prop maker.  Powersport was only claiming 210 h.p. and
 I think that is more in line with what the average p-port builder can
 expect.  In aircraft we are seldom able to achieve the same optimum
 numbers produced in dynos and on cars.  Largely that is due to our fixed
 gear ratio an also by imperfections in the design and fabrication of the
 intake and exhaust manifolds, like Matt mentioned.

 With reguard to props, I am still mostly an advocate of fixed pitch
 composite props for our application.  The MT electric c/s is heavy (like
 a lot), expensive (like a REAL LOT), and comes with an RPM limitation
 that you would not want to have to live with (can't remember the number
 off the top of my head).  The IVO is, well, the IVO... search the
 archives.  And Whirlwind, as of the time I called them asking about a
 prop 7 years ago, would not make one that turned in reverse direction or
 with custom blades. (even in ground adjustable form).  Warp Drive and
 Whirlwind both do not make hubs and blades big enough for our application.

 So that pretty much leaves fixed pitch.  I disagree that metal props are
 always faster.  If this is true, then why are all the top finishers,
 indeed most of the fields in the Formula One, Biplane, and Sport classes
 at Reno using composite props?  Kevin Eldridge was the odds on favorite
 to win the 2010 Super Sport class in his Nemisis NXT when an oil line
 blew and overspead his prop causing it to quickly depart the aircraft.
 He credits the fact that he had a composite prop and not a metal prop
 with saving his life because a metal prop would have taken the engine
 with it.  But that's not why he was using a composite prop, he was using
 one because it was fast - and he was doing more than 400mph.

 If there is a difference in modulus that disadvantages composite props,
 then it is so small that it does not overcome the other advantages that
 composite props offer in terms of efficiency.  Not to mention ease and
 cost of production

 Although the Catto has an epoxy layer, it is not difficult to re-pitch.
 Craig took a few degrees out of mine in just a couple of days for
 minimal cost.  Matt is right, Craig said that it is easier to remove
 pitch than to add it.  But still, go with about 210 hp. when having your
 prop made.  Getting a loaner would be nice if you can find one.Or,
 maybe start with a used prop that you can re-sell for about the same
 price that you paid once you get some performance numbers.
 --
 David Leonard

 Turbo Rotary RV-6 N4VY
 http://N4VY.RotaryRoster.net
 http://RotaryRoster.net

 A P-port intake manifold is one simple bent tube
 so it is entirely smooth from intake to port. There are
 no parts that mismatch. That is one reason I advocate  p-ports.
 The manifold is easy to make and hard to screw up.

 The design is an exact copy (port timing and tubes size) of the P-port
 Mazda used to win Le Mans. That engine had 620 HP
 at 7500 RPM. That is 155 HP per rotor or 310 HP for a 2 rotor
 so if anything I am being widely conservative by claiming
 only 250 HP at 7500 RPM.

 The Power Sport p-ports had smaller diameter tubes and the power
 was 215 HP (and not 210 HP) at only 6000 RPM and not at 7500 RPM.
 Power is torque times RPM and torque in a p-port rotary is nearly
 constant.



 Mazda 2 rotor p-port road racing engines have been generating over
 300 HP since the late 1970's.

 The vast majority of people going for p-ports are using a
 2.85:1 gear box that rotates in the right direction.

 The modulus of elasticity of carbon is 3 times higher than aluminum
 so in theory it should be better.

 What I said about that was:
 "IMHO pure wood props will always have less performance than a metal prop
 due to the lower modulus of elasticity wood. The high modulus of
 elasticity in  carbon has yet to be taken advantage of."

 Perhaps I was wrong about carbon not yet being taken advantage of.

 I said nothing about the modulus of elasticity of composites being lower
 that metal. Tracy Saylor, who demonstrated the fastest RV6 in the world
 at 238 MPH in the Sun 100 race told me his CS metal prop was 15 to 20 MPH
faster
 than a so called composite CS MT prop which he tried and which is mostly
wood.


 Despite running MT props the twin Power Sport RV8's were faster than
 a 200 HP  IO-360 owned by Van's at a comprehensive performance test done
back
 in 2007.  See the last attachment. The fuel burn test was rigged showing
 the Power Sport engines to burn far more fuel than they really do.

 I have an RX8 P-port sitting in my hangar ready to go into Mike Wills RV4.
 I will be building a new gear box that rotates in the right direction
 for it.

 We are now leaving Sunday to pick it up.

 Do you want to race? :) You should beat me hands down with a turbo :)

 Paul Lamar

I agree with Paul that p-ports should be easy to make power with.  It's
mechanically and aerodynamically simple and direct.

However, some aspect of the induction system might still have a problem that
could limit horsepower. The plenum, throttle body (carb?) filter setup, air
inlet, etc might not be packaged properly to make horsepower.  Will a fuel
cloud blow out of the inlet when on tap, causing a massive (or subtle) lean
loss of power?

That said, I think you won't know how well it's going to do until you run it
with all of the stuff installed.

I hope Neil's engine makes his target horsepower, be it 230, 250, or
whatever. But I think there are too many variables.

Is Neil's engine installation a copy of another, known performance, setup?
 How does it differ?

And then, what about the exhaust?

This is the nature of experimental engines.

I can't recall the details of Neil's airplane. No offense to him, but, I've
seen people do all sorts of funny stuff on an experimental aircraft (or car)
engine and then wonder why it has serious performance problems.

I am confident that the engine can make 230-250 hp in the rpm range being
discussed. But, if there's something amiss in the overall system, will Neil
spend the time tweaking it to match the prop? Or will he change to a prop
that works with the horsepower being produced?

As for props..

Fixed pitch metal props are not allowed at Reno..  In early days, racers
were using cut down and grossly repitched (forcibly twisted) factory metal
props, and then turned them to a much higher rpm than they were engineered
for. They apparently had some spectacular failures. Fatalities, I believe.
 I bet the f1's and biplanes would use metal props if a metal prop could be
proven safe enough under race conditions.

Not all composite prop blades are created equal. I believe the MT props are
not optimized for high cruise speed.  The thicker blade tips might have been
designed for a long service life while using relatively ordinary materials.
 It seems MT might be due for some redesign.

Hartzell has been making some sophisticated swept-tip composite props the
last few years. Side by side tests show them to be as fast, if not faster
than the comparable metal prop.

Some prop rpm restrictions aren't about the prop so much as being driven by
a 4 cylinder direct drive engine with torsionally active crankshaft. A
gear-reduced rotary may have significantly different torsional behavior, and
may be subject to different rpm limitations (don't idle too low)..

Composite and wood props are lighter, which can help torsional problems.


Regards,

Matt-

We ran it and flew it Matt. Mustang II. No fuel cloud with fuel injection.
The cloud is caused by the reverse flow through a carb. The venturi cannot
tell the difference so fuel comes out regardless of the flow direction.

Mark Steitle is flying one as FI p-port 3 rotor.

Paul Lama


I have always been of the belief that the "fuel cloud", actually
flow reversal caused by the exhaust pressure on overlap, lowers
potential HP in select rpm ranges (depends on pipe lengths),
and probably overall HP as well.
Anyone ready to experiment with the Tesla Valvular Conduit?
See patent 1,329,559

Dan F