"Simpson, Bill (W.R.)" wrote:
Paul Lamar,
I got a lot out of your forum at OSH. When you mentioned Dave Lednicer's
name, you got my attention and improved your credibility with me
immediately. I met Dave while we were both engineering students at The
University of Michigan, he gave me my first ride in an airplane and is truly
a terrific guy.
You made a strong impression on me with the commentary on cooling duct
design, etc. I tried to Find the two books that you mentioned, and have had
some difficulty. I found Compact Heat Exchangers by Kays and London, but
have had difficulty finding Aerodynamics of Propulsion. I am still guessing
at the spelling for the authors: Kuchman and Weber? Please correct me on
this. Any suggestions for a source of this book?
One event of note during the show for me was that the Powersport RV6 has
apparently been having fun getting their cooling together. Did you see it?
If not, here is what I saw:
Primary air intake is a "laughing mouth" below the spinner about 9" wide
and 4 1/2" deep. They have added a NACA duct with an auxiliary inlet about
3" deep by 6" wide below the original in bottom of the cowl, where the cowl
is still enlarging in section area. The original outlet looked commensurate
with the original inlet and was just an overlap below the fuselage. They
placed a rounded edge on the firewall. They then added a fixed "cowl flap"
section opening below the original outlet.
The overall impression that I get is one of "This thing is not cooling
well enough, perhaps some more inlet and outlet area..." The surprising
thing to me is that they made the top surface of the inlet flush with the
propeller spinner. It seems to me that the spinner probably creates a pretty
substantial boundary layer and it is being ingested. I suspect that the
inlet should probably be separated like is used on many turboprops, etc. The
use of the NACA duct below seems ill advised. I wonder if they were cooling
fine in cruise but in climb they had trouble, so the NACA duct on the bottom
and "cowl flap" were added to investigate having a moving cowl flap...
Anyway, I was wondering what your thoughts were on their design.
I look forward to your response.
Bill Simpson
Technical Specialist, Converter Clutch and Damper
Used books on the internet is the best bet. Sometimes people
sell them on Ebay
Kuchemann and Weber. McGraw-Hill. Aerodynamics of Propulsion
1953 Lib of Congress cat card 52-6541
Kays & London "Compact Heat Exchangers" Kriegar Publishing
Malabar Florida. ISBN 1-57524-060-2
Yes I saw it :-)
I agree with your assessment Bill.
Did you get to discuss planetaria's with the people in the Power Sport
booth?:-)
I have taken the liberty of adding you to the list.
If it gets to be too much let me know and I will take you off.
BTW we are widely using the low cost C6/E4OD planetary gear set in our
PSRU's.
Tens of thousands of hours of accumulated successful use so far.
Thanks to Ford :-)
This jpg is what we using to isolate the rotary engine torque pulses.
There are plastic washers and rubber bushings under those large metal
washers.
It is working great. Perhaps you can give us additional insight.
Paul Lamar
///
Hello Bill,
It is nice to hear that people took the time to have a look at our
(Powersport's) RV-6A integration and cowl at Airventure this year. It is a
work in progress which is delivering very good performance. You have made
accurate statements concerning the appearance and sizing of the inlet(s) and
outlet area on our pre-production cowling. We thought that it would be of
value to the list members to know how well this system currently works, and
why it is configured the way it is.
The Powersport RV-6A with its current pre-production cowling cools its
215HP during max power climbs with OAT at 100deg. F During cruise at this
OAT, the oil/water temps are typically 185/180 deg. F. This level of
performance was demonstrated on 5 different days during the manufactures
showcase at Osh. this year. To say that "This thing is not cooling well
enough" is an inaccurate statement. The truth is that it cools very well,
and will be refined to yield even greater efficiency and performance.
We chose to incorporate the "laughing mouth" inlet bellow the spinner to
optimize drag in cruise situations. At the time this decision was made, we
were awaiting new propeller blades from Mt-propeller which promised to have
efficient chord right up to the spinner. Testing with a velocity rake
across the inlet indicated that the new blades were not as efficient inboard
as we had hoped resulting in the top 1/4 to 1/3 of the inlet being
ineffective. Rather than change the whole inlet before Oshkosh, we elected
to install the NACA duct to replace the air that was not flowing in through
the upper area of the original inlet. This addition, while not ideal
lowered temps by 15 to 20 degrees, and improved ground cooling substantially
as you might expect. Our cowl flap is indeed fixed, but not because it
needs to be open in cruise, but because we did not have time to make it
functional for the show.
Those people who contact us directly, or stopped in to our booth at the
show, are/were given honest answers to their questions, and accurate
descriptions of our performance. As always we encourage all individuals
considering a rotary engine to ask questions and get answers to those
questions from several sources. It is all too easy to make inaccurate
statements when the research has not been done. As always we welcome calls
or e-mail to help clarify performance and integration issues.
All the Best,
Keith Holm
Manager
Powersport Aviation
531 Simmon Dr
Osceola WI 54020
P 715-294-2557 F 715-294-3151
keith@powersportaviation.com
www.powersportaviation.com