> > > Here are the specs on the prop:
     > > >
     > > >  MTV-18 (.pdf,  59k)
     > >
     > > >  192 cm / 75.6 in    260 HP     2800
     > > >
     > > > I like your helicopter analogy! If I go the supercharger

route, maybe

     > > > I'll have to install a tail rotor for the vertical stuff.
     > > > I really appreciate this dialogue, Paul, thanks!
     > > > Gordon, I can't find you in the Starduster Registry. Are you

listed?

     > > > Ben

     > >Wow that is a big prop to go 2800 RPM.
     > >
     > >Paul Lamar

     Michael McGee wrote:
     >
     > Kinda like a Harley with after-market pipes setting off car

alarms for blocks.

     > Cool.
     > ..of course the NIMBY's would scream..
     >
     > Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
     > 13B in gestation mode

Ben Baltrusaitis wrote:

Those prop specs are from the MT web site and only match the
airplane/engine combination by horsepower. I contacted MT and they
will make a custom prop for my plane and the rotary engine so
diameter may be adjusted. However, I will be getting a composite
prop so rpm limits of 2800 are fine.

Ben

I think that will work fine.  I ran the Sun 100 race at an engine rpm of
6250 which gave me a prop speed of 2872 rpm.   Everyone who saw me cross the
finish line remarked how quiet it was so tip speed is apparently well below
critical.   On a cool day (59 deg passes for cool in Florida) I turn 6400
rpm at top speed (2941 at the prop) and still don't get that loud cracking
sound that accompanies the tips going sonic so I still haven't hit the
limit.

Doing the math, at tip speed at 2941 is 870 fpm (on 68" prop).  At SL, mach
1 is 1100 fps so looks like enough margin to me.  Yes, I know you can't use
full mach 1 as the limit but even the rule of thumb 85% gives 935 fpm.  Even
if you do push the limit during an aggresive aerobatic routine, who cares?
Go for it Ben.

Tracy

 
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