I am finally, after 10 years of false starts, soon to begin construction of
an RV9A.  Even though it is rather soon in the process, I have been
struggling with engine selection.  Over the years I have been considering
the Mazda Rotary as the number one choice on my list.  I have had experience
with a shock cooling situation in the past that helped me make the Rotary
decision.  I do not want to spend the money for an "old" technology engine
that very well may fail me and or cost me even more down the road fro
mandated factory error repairs.  Besides, I am one who believes completely
in the KISS principle.

My question to all and you Paul is this... Since Van's limits the 9A
to 160HP, what engine series would you recommend I begin searching for and
what problem might I run into with this engine during conversion?


Tom H

I think Van has engine weight more in mind than HP.
He assumes you are going to use an AC engine.

He also feels his biz is less threatened if somebody buys the engine from
him and assembles the aircraft exactly like an Ikea furniture kit
and exactly according to the instructions.

Tab A in slot B :) IMHO that amounts to a ploy to get around
the certified aircraft cost and rules. That is also why the
EAA no longer mentions the word "experimental".

Lets us say for the moment you decide to put in a 250 HP rotary
in that weighs the same as a 165 HP Lyc.

What is the downside?

None!

You don't have to use more than 165 HP.

The 165 HP NA Lyc engine becomes 115 HP over 12,000 feet.
The 250 HP NA rotary engine becomes 175 HP over 12,000 feet.
Flat rating without a turbo.

Van's airplanes have strict VNE's. Bad things happen when the VNE is significantly
exceeded. Tails have fluttered and come off. The 9A tail has probably been
improved over the earlier models. Never the less don't exceed the VNE.

It is true. People have gone faster in various competitions with Van's airplanes
than the VNE but they have beefed up the tails in most cases. IMHO I suspect
part of the problem is the vibration characteristic of the aircraft piston engine.
I know engine vibration enters into the equation for flutter. The rotary is much
smoother.

Another factor, for some strange reason, is composite designs
do not seem to have this VNE/tail-flutter problem. IMHO I suspect this is due to
the higher damping characteristics of composites over metal. Carbon fiber movable
control surfaces would have a better stiffness to weight ratio and require less
balance weight. On the other hand there are more RV's out there.

Paul Lamar

 If I may- the downside if there is one is not having an easy drop in
FWF package.  If you have the time to dedicate to making sure the engine and
other FWF items are installed in an "airworthy" fashion, then there is no
downside.  I acknowledge that I will likely have another 100 or more hours
in installing the rotary in my plane, and that's OK.  I priced a couple of
experimental Lycomings, and the costs were in the area of 30K and up
complete.  Used they go from 10K and up with unknown condition.

  The positives are that for less than 4K, I have 2 complete engines.
Yes, for less than the cost of 2 Lycoming cylinder kits I have 2 engines.  I
am taking the time to fabricate my install so that it is plug-n-play.
Meaning, I have a harness that I can unplug and swap the engine out
relatively easily.  The intent is that in the event of an engine issue, in a
day I can replace the engine with my spare.  An A&P wouldn't have your
Lycoming cylinders replaced that fast and you would still have the old motor
in the plane.

  For you, there are RV's flying with rotary engines that can be a good
basis to keep you from re-inventing the wheel.  In my case, I have a fairly
rare plane- a Wheeler Express- and not many examples to use as a guide.
Tracy Crook- the guy that makes most of the PSRUs that we rotary engine guys
use- has a working RV6 and RV10.  The 6 has about 2000 hours on it, not sure
about the 10 but it has a 3 rotor engine, stellar performance, and Tracy is
quite happy with it.  I have lots of pictures of his 10 for reference if you
want to see them.

  The negatives are that there wont be much mechanic help at the
airports that you land at.  Most A&Ps that I talked to wont discuss anything
except an airplane engine, and basically cant or wont work on anything else.
Many of the parts will have to be made specifically for your installation.
We are working on a sort of standard installation based on working installs,
but haven't gotten it together yet.  One other issue that might pop up is
the lack of a place to install the vacuum pump.  I have all the avionics
from my old plane that blew a 54K IO 520D and therefore was not cost
effective to repower.  Without being able to use my engine driven vacuum
pump, some of my expensive instruments are not useable.  One option is to go
all electronic, but I like backup systems.  It might be a bit more difficult
to get insurance, and the resale value might be lower.  But I will be 30K
better off financially building it, so 30K reduction in resale is a wash.

Tracy's installation methods differ from some of what you will see on
this board.  Most of what you see here could be looked at as leading or
bleeding edge.  New stuff, original designs, like mufflers, etc.  Tracy
tends to lean toward tried and true, simple, construction.  His air box is
made from fiberglass with a plywood/ cardboard core.  He din't worry about
the 18 inch runners that are required for maximum HP.  Tracy does not prefer
P ports, he prefers to use a 3 rotor instead of a 2 rotor P port.  To each
his own.

  That being said, I think the engine is worth the work. Simple,
reliable, and inexpensive enough to replace rather than patch.

  Ask questions, get answers. This board is the place to get all the
information that you will need.  And, as someone that is working on the
engine installation at the moment, it is never too early to get started with
it.  My advice is as soon as you get an engine mount, buy a junkyard motor
and mount it.  Start working on all the little time consuming things like
intake, injectors, fuel system, etc.  on the engine mount on a plywood
firewall.  When you are waiting for an airframe part, work on the engine.

Kevin Alderman

A junk yard motor is good advice. Do a mock up with Styrofoam first before
you do a motor mount unless you use this design. Free dimensions on all the
tubes if you choose to go this route. Doc Custer was building one like this
and Jack Hilditch is building a RV9 with a similar arraignment.

I have lost touch with Doc.

I can have a motor mount built for you locally by Do Rite in Ventura CA.

Also read http://www.rotaryeng.net/mm-__instruct.html <http://www.rotaryeng.net/mm-instruct.html>

Also get my book How To Cool Your Wankel still on sale for
$35 cash for the rest of the month.

In the past 12  of the last 15 years many people have had trouble with cooling.

A 3 rotor weighs and cost much more than a 2 rotor if you can even find one.
The weight alone would make it totally unsuitable for a RV9A.


Don't use an off the shelf automotive muffler. Just about everybody has
gone through several including Tracy. In one case the aircraft crashed.
Fortunately the pilot was not hurt.

Contact me on muffler design and I will show you how to build a fail safe
design. Now flying on an RV4.

An automotive smog air pump works well as a vacuum pump.

Don't forget. We have been at this for 15 years.

Paul


Tracy Crook has a RV (Renesis RX8 2 rotor engine) and RV8 (Cosmo 20B 3 rotor engine)............

Kelly Troyer