----- Original Message -----
Sent: Wednesday, March 04, 2009 1:55
PM
Subject: [FlyRotary] Re: Questions on
buying a rotary plane
Glad I woke you guys up! :-)
While it may appear from my post that I was
trying to discourage this guy and am not happy with my rotary powered airplane
that is not the case. I'm very happy with it. Will be even happier once I get
all of the little glitches fixed so I can just fly it.
I simply wanted to make sure William
understands what he's getting into. What appears to be a fairly straight
forward mod is a lot more complicated than it appears and there are potential
pitfalls that are not necessarily obvious.
My bad on the misread regarding fuel
efficiency - he was talking about homebuilt aircraft versus factory
built planes, not rotaries versus certified engines. I think he's still
way off base here which was why I replied to his post.
Al, I dont know anyone who actually
KNOWS what BSFC they acheive with their Lyc/Cont. I know that low .40s is a
published number that is stuck in my head. I know what kind of fuel
consumption I got with my Lyc powered RV-6A at cruise and I know there
are certainly enough flying Lyc powered RVs to pretty firmly establish
a cruise performance baseline. Since there are more flying rotary powered
RVs than other types, seems like we should be able to get at least an idea of
how they compare. Lets challenge the rotary RV fliers here to post real
cruise performance (altitude, TAS, fuel consumption) and answer the question.
Or give me a year and 100 hours and I'll let you know how my RV-4 stacks up
against the -6A for a data point.
As for your performance against
conventional powered Velocities, thats great news. I think thats one of the
significant short comings of our little group here. Common perception is that
rotaries are gas hogs and we dont do anything to accurately document and
advertise our performance.
Mark, I agree that burning Mogas definitely
makes a big difference economy-wise. But that's a red herring. You could
legally burn Mogas in a Lyc/Cont also - just that most guys who are too
conservative to choose an auto conversion are also too conservative to burn
Mogas. Burning Mogas isnt the exclusive territory of the rotary. I
personally know a guy with a 200HP Lyc in an RV-8 who has burned Mogas
exclusively for years. Really what it comes down to is convenience and
comfort. Lets be fair, compare apples to apples, and while we're at
it throw in the additional cost and hassle of having to pour in 2 stroke oil
for your rotary (assuming you do that as most seem to do).
I do totally agree with you on the price of
parts. And that was one of my huge motivations for going this route. But
really the biggest motivation was to do something a little different. When my
RV-4 finally makes it's appearance at a fly-in (hopefully this year) it's not
going to be lost in the sea of belly button RVs that show up.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Monday, March 02, 2009 9:51
PM
Subject: [FlyRotary] Re: Questions on
buying a rotary plane
I dont know
where you got the idea that rotaries are more fuel efficient.
Lycosaurs/Continentals typically have BSFCs in the low .40s. The commonly
accepted number for a rotary is about .50. Some here seem to do better,
others worse.
Mike;
I’m not
disagreeing with the points in your message; but I am wondering if you
know anybody actually flying a Lyc/Cont and achieving BSFC in the low
40’s. I see numbers like .43 or .45 bandied about, but I guess no
one leans enough when flying to get that for fear of burning out a valve –
or worse. I’ve yet to hear from anyone flying a Velocity like mine with
a Lyc who can surpass the speed/fuel burn that I get with the 20B. I don’t
know why – it surprised me; but there it is.
I think in the
real world operation the BSFCs are comparable. I may have a bit
lower drag because of smaller cowl; or other factors.
Al