RE>>      Hi Paul-

RE>>      I'm still looking for a prop to use when first testing/tuning the
RE>>      engine.  My thought was to get a prop -- any prop -- that would at least
RE>>      prevent the engine from over-speeding, but not necessarily be one I
RE>>      could fly.

RE>>      Well, I've just tripped across a prop that might do both, and at a very
RE>>      modest price (compared to the $2500 I was looking at with performance
RE>>      props).

RE>>      Anyway -- my question is whether this is a flight candidate.  I know
RE>>      there are a couple of folks on here with magic prop software, perhaps
RE>>      they could run the numbers & tell me if this would work for me.

RE>>      Attached is a photo of the prop data plate.  Airplane is Mustang II.
RE>>      VNe
RE>>      is 235mph.  Desired cruise is anything north of 200MPH. 13B at 230HP.
RE>>      Tracy's rd-1c redrive.  Typical prop on a M2 is 68" 2-blade.  I *really*
RE>>      want good climb performance, since my field is at 6873' and summer
RE>>      DA is
RE>>      typically 9000' - 10000'.  6000' long runway.

RE>>      Mark

RE>>      I don't think that 60 inch prop is going to give you good take off
RE>>      performance.
RE>>      Should or could be stalled for a long time on the runway. I think
RE>>      you need
RE>>      a much longer prop. Perhaps 3 blade. Around 70 inches. Maybe 72 inches.
RE>>      With less pitch.

RE>>      That prop might be OK for Dave's turbo engine.



RE>> The prop in question is a 3 blade - not sure if that was obvious.  In
RE>> any case, it would be interesting to know what the numbers for this one
RE>> work out to be.  One of my desirements is to find a way to tame the
RE>> 13b's fuel thirst at cruise.  That may be unrealistic, I know.  My fuel
RE>> tank is only 23 gallons usable - so I have an issue right off the bat if
RE>> I can't get consumption down somehow.  Performance props was
RE>> recommending prop-limiting the RPM by having a really aggressive pitch
RE>> (although not quite so aggressive as this).  They also thought 70 or 72
RE>> inches was the right number for a 3-blade.  But .. I could get this one
RE>> instantly at 1/3 the price.  So I'm trying to see if it would work as
RE>> something to get me flying for a while.

RE>> Mark Supinski


RE>> It might be worth buying. Since it is a Catto you can probably get what
RE>> you payed for it if it is not damaged.

RE>> A crude way of calculating pitch figure 80% slip at 200 MPH at cruise RPM.

RE>> In theory 70 inch pitch at 2700 RPM is  189,000 inches per minute
RE>> or 15,790 feet per minute or 262 feet per second or 178 MPH
RE>> at no slip. At 20% slip that is only 142 MPH. A lot depends on how
RE>> they measure pitch angle but that is true pitch.

RE>> Let's run their numbers... 60 inch pitch at 3137 RPM or 188,220... 15,680
RE>> 261 feet per second 178 MPH at no slip. Interesting.
RE>> Obviously pitch is measured with a protractor on the bottom
RE>> of the blade airfoil. The real true pitch is higher than this.
RE>> I'll need to plot a typical prop airfoil to figure the difference.

RE>> Takeoff will be what ever you get.

RE>> Check my math :)

RE>> ------------------------------------------------------

RE>> "Pitch is the measured of the length of the cylinder of air thus moved by the prop in
RE>> one complete revolution, assuming 100% efficiency. It therefore gives a theoretical
RE>> speed for the airplane, for any rpm. But not all props have the same efficiency.
RE>> Theoretical speed = rpm x pitch x eff."

RE>> Pitch is usually measured at 75% of the radius.
RE>> Is in the ball park of 26 to 32 degrees in terms of blade angles.

RE>> --------------------------------------------------------------

RE>> This is interesting.
RE>> http://www.nclra.org/Programs/PropCalculator.html

RE>> You put in 200 MPH, 30 inch radius, 25 degrees,  2500 RPM and you get
RE>> 98" pitch.

RE>> Lets see 35r times .75 is 26.25r for a 70" dia prop
RE>> lets try that radius.

RE>> We get 88 pitch. Now we are getting in the ball park.
RE>> The 3/4 radius is the key.

RE>> Still not making sense.

RE>> Paul Lamar ...No rotor no motor.


RE> Hello Paul and Mark,
RE> I purchased a prop from Lonnie Prince for my Mustang 2. The cost was
RE> around $850 US and is wood with carbon fiber covering. Size is 68X78 P
RE> Tip. Info given to Lonnie was the Renesis engine at 250 hp at 8500 rpm and
RE> 3000 prop rpm. I figured with the extra breathing of the engine
RE> without the Renesis restrictive manifold there would be a bit more
RE> than 250 hp there. Any extra hp will be a bonus.
RE> Regards Don Dunbar

RE> ------------------------------------------------------

RE> Don, your current  PSRU is only 2.17 to one. You will play hell getting
RE> 8500 RPM.  You need to change the PSRU around to a 3.17 version
RE> which you can do with the planet set that is in there now.
RE> You just have to machine the teeth off the planet carrier,
RE> fix the ring gear to the housing and take power off the planet carrier.
RE> Then of course your prop will rotate in the correct direction.
RE> The reverse of what it would do now.

RE> Paul Lamar

-------------------------

My drive is 2.87. This is a new PSRU unit that I am building. It is
similar to the earlier version.