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
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
When starting from scratch and instruments need to be purchased, the new EFIS
is the way to go. Paul and some others on here are working on Tablet based
instruments. If nothing else they will work as back-ups for low $ invested. I
understand when you already have a complement of instruments you want to use
rather than investing in new. To each their own on what to install. It is your
aircraft and what floats your boat is good as it is yours and your dime. There
is always hecklers about but most of them may not have a plane. If they do,
they can use what they want, as long as it is safe!
Dale Davies
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