Paul,
Just wanted to let the group know that N981MP, a Long Ez, with a Mazda
13B made its first flight
today from Kissimmee Gateway Airport (ISM) Florida. After many
high speed taxis I made one trip
around the pattern.
The engine is a 1988 13B with Tracys' EC2 and RD-1. The biggest problem
I was concerned with
was the cooling. I basically used the same setup Tracy used on his RV.
Two AC condensers and
and a after market oil cooler were used for the engine coolant. Two
after market oil coolers in series
for the oil cooler. The engine would idle on the ground for 30 minutes
without overheating. The pusher
configuration pulls a lot of air through the cowling if you have it
sealed tight. I put 10 hours on the
engine before I flew it.
On the short trip around the pattern temps never exceeded 180 - 190 F on
the coolant and 170 F
on the oil. I think I need a prop with less pitch for takeoff as I was
not able to get the engine much
over 5000 rpm on climb out.
Attached is a photo of the aircraft. I'll try and get some pictures of
the engine this week and post
them.
Mike Perry
N981MP
----------------------------------------------------
Congratulations Mike. Can't wait to see the pictures of
"under the hood". What was the outside air temperature
when you flew it? What brand of prop is that?
Pitch? Diameter? I assume the RD-1 is 2.17:1 gear ratio.
> Paul Lamar
----------------------------------------------------
Great, Mike!
I had similar takeoff rpm with the 20B on my Velocity. With the prop
pitched for best cruise, that may not be far off the mark. I think we
best
wait until we get up to speed out of the pattern before drawing any
conclusions about the prop pitch.
Is that a Catto prop?
You have the advantage of being able to fly your plane. I'm stuck
depending
on a test pilot who is too busy to get here to fly. My insurance won't
cover me until I get 15 hrs dual in M and M.
Al
------------------------------------------
Congratulations Mike.
I am also interested in hearing the numbers on your prop.
For reference my prop is 62" diameter by 68" pitch, 3 blade. I see about
5000 RPM when I rotate at 75 to 80 knots.
Climb at 100 knots it goes up to about 5400.
Max. level flight WOT is about 6400.
2.17 RD-1B. Stock 1986 NA engine no porting.
Perry Mick
Paul
The outside air temp was approximately 90 F on the first flight. I
fabricated the prop using an old DOS program from Bates Engineering to
optimize the design and give me the proper shape and cord of the blades.
http://www.geocities.com/aeroopt/index.html The prop was constructed using
Al Wicks method of carving the shape out of laminated wood then covered with
many layers of fiber glass.
http://www.maddyhome.com/canardpages/pages/alwick/prop.html The prop has a
62" diameter and 75" "geometric pitch".
After looking again at the numbers, I should of had about 2300 rpm at the
prop with 5000 rpm on the engine tach and 2.17 gear reduction. I had added
a "Tiny Tach" that I think was set up for a two stroke engine, but was
giving me pretty close to what I was seeing with the optical tach at idle.
Climbing out I only saw 2100 rpm on the tiny tach. This 200 rpm difference
is probably the error when I add 3000 rpm from the engine to the prop tach
readings. Burt Rutan in one of his newsletters recommended 2350 prop rpm as
a minimum for takeoff with an O-235.
Attached are some more photos. The engine mount has no shock mounts.
Vibration has not been a problem. The exhaust is a heavy Racing Beat flange
with stainless tubes into a 4 inch diameter can with the tail pipe out the
rear. I added a stainless shield over the exhaust to protect one radiator
and the wing root. Two MSD fuel pumps and the old heavy Mazda ignition
coils.
The main radiator is a GM condenser behind the NACA duck with an exit duct
back to the prop. The second condenser is in the right wing root with an
intake duck on the top rightside of the cowl. One additional cooler was
added in the left rear wing root area. This one takes coolant off the
heater port at the rear block. I don't know how much this affects the
overall cooling. I have one temperature sensor at the top of the water pump
where the original sensor was, plus another where the return from all three
radiators return lines come back together just before entering the water
pump.
The oil cooler is two after market coolers in series which gives me about 280
cubic inches. I think the Mazda cooler was around 180. My oil temperatures
have never been a problem. This was overkill after hearing all the high oil
temperature problems I was hearing several years ago. The coolers are
mounted with small rubber shock mounts from the metal brackets attached to
the left side near the spark plugs.
Mike Perry
N981MP
------------------------------------------
Nice work Perry.
Do you have a boost pump on those MSD's pumps?. I am surprised
they are priming so far up from the tanks.
IMHO part of your 5000 RPM problem is the dynamic
chamber. Dynamic chambers are good for torque at 3000 RPM
not 5000 or 6500 RPM. You would be better off with four
bell mouths and a simple plenum with an axial butterfly
throttle. No sharp right angles if possible. Do you have
a filter between the ram air scoop and the TB? If so try
taking it out.
What are the dimensions of the ram air scoop opening? Looks
like it could be a bit bigger. Sorry about all the questions.
A few more pics would help.
The prop pitch is a bit high. A quick and dirty fix is to cut
an inch off the diameter one inch at a time. Or do a p-port :)
Your cooling is good at 90F however I would not draw too many
conclusions about the cooling until you get the RPM up 6000 or
6500 on take off. Heat rejection to the coolant is directly
proportional to HP. 5000 RPM to 6500 RPM would be about 30% more HP.
Paul Lamar
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