Al, if you are talking about their RV FWF package, I'm amazed that the Egg
setup cools as well as it does. That is the crudest cooling duct I can
imagine (flat sided sheet metal box behind the inlets) and it would not
work at all if it were not for external diffusion helping them out. Could
be wrong, but I think their "flow restriction" idea is a dead end idea just as
the NPG was.
----- Original Message -----
Sent: Thursday, February 02, 2006 6:45
PM
Subject: [FlyRotary] Re: Suitability of
NPG for Rotary Engine use
Hey Dave, I hear you about cooling. I fly the exact same engine as the
Egg guys. Same fuel burn, same cruise speed. I can get my coolant temp to rise
only by extended taxi during hot weather. I then take off full throttle from
sea level to 12k ft, and it cools during the climb back to normal 200F
operating temp. My coolant pressure never exceeds 7psi. Using 50/50 glycol
mix. So I have a huge safety margin.
The Egg guys have had a significant cooling problem for years. Finally
resorted to using Evans. Yet they still are unable to achieve the same robust
cooling.
So both aircraft are producing the same work. What's the
difference???......I don't know. That's one of the problems with cooling. It's
so difficult to measure the characteristics that count. This is a familiar
pattern. All of the most difficult problems businesses have always involve
this same pattern. If you can't readily measure it, then we make the wrong
decisions and don't have a clue. Rumors and assumptions survive year after
year.
Egg guys just recently made some progress. They found that all their
radiators had flow restriction. Yet they are still not there.
So I have some theories. I place little value in theory however. I
suspect all the RV's suffer from high velocity, turbulent air. My radiator is
placed 6" directly behind a NACA. The air is slowed down, doesn't have
to turn any corners. I would sure be quick to test that theory. I notice that
NSI RV's place radiator near firewall. Slower moving air. But I don't have any
info on their cooling efficiency.
They say to "dig wide", not deep when pursuing problems. Meaning, don't
try to finesse a problem. Try all manner of solutions. Find ways to measure
the airflow. I used atmospheric pressure sensors on each side of
radiator.
Good luck
BTW, based on your descriptions, I too would give strong
consideration to Evans. I deliberately overheated my engine many times
during taxi runs. Familiar with the boil over cascading failure. Learned a
lot.
The HP is the easy part. Get the cooling right first.
Lynn E. Hanover
Very true. Will the "right" cooling system please stand up!
My cooling system is too small for the power I wanted to be
able to use. I could still outrun any 160 hp RV-6 and outperform
those with 180 hp and fixed pitch props.
But I was out-climbed by the guys with 180hp and c/s props and outrun
by the 200 h.p. crowd.
This should have been good enough. Flying n.a. there were no
cooling issues at all.
But I am starting to think that cooling is like money. No
matter how much you have, its never quite enough.
My current plan it to go from a 2" rad to a 3" rad of the same or
larger surface area. I will also add some fresh intake
ducting, a cowl flap, and spray system.
That should allow me to easily beat the 200h.p. guys.... but then
there is always the tri-aviathon...
Any suggestions? :-)
--
Dave Leonard
Turbo
Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://membersaol.com/_ht_a/vp4skydoc/index.html
-al wick
Artificial intelligence in
cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on
engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk
assessment, Glass panel design
info:
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