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From: "Dave Wilenius" <wilenius@sympatico.ca>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: RE: [FlyRotary] Re: Ground Testing
Date: Tue, 10 Mar 2009 09:53:43 -0400
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"A normally aspired Renesis will work well, but I think will need very=20
careful attention to intake and exhaust optimization to get the power=20
you're probably hoping for."=20

 This seems to go against what I thought was conventional wisdom where =
the
Renesis is lighter and doesn't have the same level of exhaust bark, =
making
it a good choice. If you want between 180-200 hp is this really that =
difficult?

 I was also under the impression that the placement of the exhaust ports =
on the side
housings improved fuel efficiency.

 If you design goal was fuel economy with 180hp would you still opt for =
a turbo REW?

regards,

Dave

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On
Behalf Of John Slade
Sent: 2009-03-09 01:20
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Ground Testing


Welcome, Jim.
You will get differing answers to that question. Mine is "not much=20
beyond the integrity of the engine itself".

Installation of a rotary in a Cozy is fairly tight and, by the way, in=20
my opinion a 20b is a little too big, long and heavy. Apart from test=20
running the engine to be sure that it's been correctly rebuilt, most of=20
what you do on a test stand will be a waste of time and effort. When=20
installed on the plane the engine is dependent on many systems that=20
either can't be effectively duplicated on a test stand, or will have to=20
be re-engineered when installed in the plane.  Sure, if you can get your =

hands on a dyno you can test power and tune, but once you put the engine =

on the plane you'll have to wire the engine into the plane's systems and =

implement fuel, ignition, injection, cooling and exhaust systems that=20
fit in the cowl. Testing those systems in the "real world" is really=20
only possible with air flowing through (and over) the cowl into a prop=20
at 200 mph and at various attitudes.

A normally aspired Renesis will work well, but I think will need very=20
careful attention to intake and exhaust optimization to get the power=20
you're probably hoping for. Next you will need some sort of muffler that =

can hold up. I wasn't keen on hanging a muffler below the fuselage like=20
the RV guys do. There isn't much room for that in a Cozy and it would=20
look very ugly and draggy. Putting a red hot muffler inside the cowl is=20
a heat radiation problem, plus there's very little room. A turbo is=20
relatively small, circular and easily screened for heat. My approach was =

that the easiest way to silence the roar was to install a turbo. This=20
way you don't have to bother with an exhaust system, and the intake=20
system is much less critical. This gives added (and exciting) benefits=20
in take-off and cruise power, but comes with its own complexity. The=20
trick seems to be to use the right turbo. Then, if you use a turbo, the=20
Renesis is a little high in compression ratio and you might be better=20
with a 3rd generation 13B. I'm working with another builder right now on =

his Cozy project. We are duplicating my 13B exactly. That might be a=20
useful indication of whether I consider it a success. The Cozy Girrrls=20
are very knowledgeable on this rotary stuff,  and they also are=20
installing a 3rd gen 13B with a big turbo.

In general, I'd say the rotary is more risky to start with - say the=20
first 50 hours - because every installation is different and errors WILL =

occur. After the first 50 hours I think the rotary is well worth it.=20
It's safer, faster, quieter, very much smoother, and much cheaper to=20
maintain. The devil is in the peripherals. Redundancy is key. I have=20
redundant fuel tanks, filters, pumps, injectors, plugs, ignition=20
computers, batteries. Failure of any item is survivable because I have a =

spare. The problem is that redundancy breeds complexity - this is where=20
the extra build and testing time comes from. I'd recommend the IVO=20
in-flight adjustable prop.

I've seen too many failed rebuilds by people who have much more=20
experience and talent than I, to risk applying my skills to this most=20
critical part. Also, there's enough to do with the peripherals and I=20
didn't need the learning curve. Unless you're determined to rebuild your =

own you might consider using an expert who's done it 1000 times and=20
knows what to modify for aviation build your engine. Given your=20
investment in the plane, a professionally rebuilt engine is cheap=20
insurance. Instead, I'd suggest concentrating your effort on getting the =

peripherals perfect, adding redundancy everywhere you can get it.

Having said all this, my take, for what its worth, would be to forget=20
the engine for a while and spend every spare waking moment building=20
yourself an airframe. Given that you have a few years to make the engine =

decision, use those years to see what happens with other installations.

I hope this helps in your decision process, or at least starts yet=20
another heated discussion you can learn from :).
Regards,
John Slade
Turbo Rotary Cozy, N96PM.
98 hours and purring like a kitten.


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