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You guys with nose wheels shouldn't get too excited. One of the reasons that almost all bush planes use tailwheels is that the nose gear is just too fragile for rough field operation. Guess what the other reason is.
FWIW, I've flown a short-legged RV-4 with a 76" dia. prop. I didn't do it very much (long story) but it can be managed by doing all takeoffs & landings tail low.
RE: Tracy's radically improved performance, I'm now flying Chuck Dunlap's old Lyc powered RV-4 (Hi Chuck). It's got a 62" dia 3 blade climb prop because he flew out of high altitude gravel strips. Down here in the lowlands of Mississippi, it turns about 2450 static & will turn over 3000 rpm in level flight. I recently tried a prop originally made for a 180 hp engine, originally 72", cut down to 68" dia., a very bad prop because of the 'surgery'. It was about 5 mph faster at full throttle & turned not quite as high an rpm as the 3 blade, but the takeoff performance was radically different. The extra 6" of diameter probably cut at least 30% off the takeoff roll. Vance Jaqua (sp?) posted a prop efficiency chart on the 'other list' comparing optimized props of various diameters. Bigger (dia.) was always better until speed got over 200, at which time the smaller props became as efficient as the larger ones. I'm pretty excited that Tracy will have the Renesis & big prop debugged by the time my -7 is ready for an engine. (Go for a 76" dia on the RV-8. :-) )
Charlie
Ed Anderson wrote:
Sounds like all around great news on the new gearbox and prop. Keep the reports coming. If such a "retrofit" of a B shell to C internals is possible and economical then that could move the trend toward the 2.85 even quicker. Shucks, if you used NA rotor housings it sounds like you wouldn't even need a muffler {:>). I am somewhat surprised that you can get the same airspeed with only about a 5% difference in rpm - sounds like my initial assumption that a higher rpm (and fuel burn)would be required to get the same airspeed is not valid. Perhaps the much greater pitch gets more work done per revolution. I wonder if possibly the fact that at higher rpm you not only get the benefit of more power strokes per second, but at the higher rpm the airflow in your manifold (assuming you are using the same dia tubes as before) is at a higher velocity and therefore great inertia for stuffing even more air/fuel mixture into the combustion chamber when the port opens. In any case, sounds like all pluses for us guys with nose gears {:>)
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From: Tracy Crook <mailto:lors01@msn.com>
To: Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
Sent: Monday, March 22, 2004 11:02 AM
Subject: [FlyRotary] Re: C mounting on a B plate?? Renesis & RD-1C
drivetesting
The -C drive has very different internals but I will look at the
feasibility of reworking the -B housing to receive the -C guts. I
think it can be done. Yes, the -C bolts right up to the same
adapter plate. I think you are right about the 2.85 becoming the
preferred ratio, but only if you can handle the longer prop. You
nose draggers have the advantage here.
The more I fly it the better I like this setup. The higher rpm
was very disconcerting at first but I acclimated rapidly. And
now that I have digested the fact that the actual rpm difference
at normally used throttle settings is only about 5%, I absolutely
love it. Another good sign is that the manifold pressure is now
more than 5% lower at any given airspeed that I've tested so far. Even if the wear rate is up 5% or so it would be a non issue. One more plus for the 2.85 is something I hesitate to mention. It's kind of like the "engine making oil so I have to drain some
out" thing, kind of unbelievable. It makes sense that there
would be less prop noise but I'm also getting less engine noise. I was getting tired of the increased noise with the Hushpower II
muffler and was almost ready to put the Spintech back on even
though it costs at least 5 - 6 mph in drag. But with the -C drive
things have quieted down substantially. I think part of the
credit for this goes to the difference in RPM moving the
vibrations away from the resonance point of the sheet metal panels
in my RV-4 but even observers on the ground have mentioned
that the engine sounds quieter.
I better shut-up now, this is starting to sound too good to be true.
Tracy
----- Original Message -----
From: Ed Anderson
Sent: Monday, March 22, 2004 8:30 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] C mounting on a B plate?? Renesis & RD-1C
drivetesting
Sounds great thus far, Tracy
Imagine having so much thrust that you can't hold the
aircraft still for maximum static, must be tough {:>). If you
initial observations hold regarding fuel consumption and
performance, then I predict the 285 will soon become the
standard. If the fuel burn/performance is a wash then only
engine wear from higher rpm might be a factor, but since the
rotary seems to only have no/ minimum wear in any case, that
probably will not be a significant factor.
So how much are you given for 2.17:1 trade ins? Seriously,
will the B model mounting plate accommodate the C model gear
box housing (looks like you mount it the same way). I presume
it would not be so simple as swapping out the internals as I
am certain the internal mounting/housing is different in the
two. Third, in case you consider getting rid of that old
performance prop, put me on top of your list.
Ed
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