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