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20B Rotary Powered RV-8 Project
12/20/09 Just an update on my RV-8 / 20B
oil cooling experiments... by Tracy Crook
On the theory that airflow patterns inside the cowl were
blocking airflow through oil cooler, I installed a partial exit duct behind the
radiator directing the airflow downward toward the cowl outlet. It looked
very restrictive but flight tests showed almost no effect on water cooling
(which is OK) but a significant improvement in oil cooling (but still not
good enough). I further restricted the airflow through the rad by
putting some roof ridge vent material inside the inlet diffuser. This gave
a tiny increase in water temp but a further improvement in oil cooling.
Long story short, after several more tests it became apparent that back
pressure under the cowl was having a major effect on the oil cooling.
I have no idea why my instrument did not read the pressure correctly. It
works fine on the bench and is properly referenced to the static system in the
plane. The normal temptation is to keep changing the cooling outlet
scheme until the internal cowl back pressure is low enough to get the cooling
good enough. My belief is that this would lead to a very high drag
solution. You may remember the experiment I did by flying with the cowl
removed. The cooling was never a problem then (except perhaps too much
cooling) but the drag was enormous. The fuel burn was 60% higher at the
test airspeed of 130 mph.
The conclusion I eventually came to was that the rad (because of it's relatively
low air flow resistance) is hogging the airflow capability of the cowl cooling
outlet. (a cowl flap did not have enough effect to fix the problem).
Keep in mind that the oil cooler is a thick AC evaporator core that is very
restrictive. The current experiment is to replace it with a much
less restrictive (to airflow) oil cooler. I found the largest cooler that
would fit in the same location as the AC core and I'm using the same diffuser as
before (slightly modified to fit the larger face of the new cooler). This
cooler is only 2" thick and core volume is 30% less than the AC core.
It is slightly larger in volume than an RX-7 cooler. Without any back
pressure (flying with cowl off), the AC core had way more than enough cooling
capacity (146 F oil temp on a 93 degree day) so I'm hoping that this smaller
cooler will be enough. Should be ready to flight test it this week.
I should point out another symptom. Power setting (and therefore airspeed) had
very little effect on the cooling (i.e., it didn't get much hotter at high
power as long as airspeed went up as well. Things got hot fast in
climb however. This also indicated to me that cooling was limited by
airflow through the system rather than by the oil cooler's ability to transfer
the heat to the air. If the cooler is simply too small, more airflow will
not help much.
Tracy
Another Update: 12/22/09
I was ready to flight test the new oil cooler installation
this morning (or thought I was). OAT was only 41 deg and it took a
long idle time to warm up so used that time to check for oil leaks and saw no
signs. The pattern of oil and water temps looked good so I had high hopes.
Watched temps during takeoff run and continued to see good numbers. Climbed out
to 500 ft and turned left to downwind and thought I smelled a slight whiff of
hot oil. Looked over my shoulder and saw that I was sky-writing with a
dense smoke trail so throttled back to high idle and did a hard 360 to the right
to setup for a downwind landing (almost no wind). The only thing new
was the oil cooler so I was scolding myself for installing this cheap piece of
junk and monitoring the oil pressure to see if this was going to cost me an
engine overhaul. Pressure stayed at 55 - 60 PSI all through the landing so
its OK. The oil cooking off the exhaust system did not ignite.
Wonder if the poor burning qualities of synthetic oil is another good reason to
use it?
On the ground it looked like there was a couple of quarts of Mobile 1 dripping
off the bottom of fuselage and left wing trailing edge. Popped the
cowl top and the entire engine compartment is drenched in oil EXCEPT for the oil
cooler core itself which is dry. The cooler turned out to be OK. The
leak was from the bottom fitting on the cooler. It came equipped with -10
male fittings so I had installed -10 to -8 adapters to match the -8 hoses in the
plane. The tightening procedure needed on these adapters had some
pitfalls. I am always careful to use two wrenches on these fittings so as
not to put torque on the cooler and damage it. These adapters require that
the adapter be put on first using the two wrench method followed by the hose
fitting to the adapter. BUT, one wrench needs to remain on the oil
cooler fitting and the other on the hose fitting. I mistakenly put one on
the adapter and one on the hose fitting. This results in loosening the
adapter to cooler mating thread as you tighten the hose fitting. That's
where the oil was coming from.
Although this was a very brief flight on a cool day, I could tell from the trend
on the oil & water temps that this cooler was going to work much better than
the old one even though it is about 25% smaller in volume. Size really
isn't everything.
I properly installed the adapters and hose fittings and tested for leaks (none
found) but didn't have enough daylight left for another flight test. Will
try again tomorrow.
Noticed one other oddity during this test. As soon as the O2 sensor got
covered in oil, it quit working. These sensors actually have to 'see' the
outside air at the cold end of the sensor. They compare the O2 in the air
to the O2 in the exhaust and stop working when they can't.
Tracy
9/6/2009: First Flight of
the RVator - Tracy's 20B Powered RV-8!!!!
09-06-09 As reported by Tracy Crook -
Builder/Pilot:
Today there was nothing left to do on the Mazda 20B powered RV-8 but
flight test it.
For those of you not familiar with the rotary engine, The 20B is a 3
rotor version of the 13B which powered the Mazda RX-7. The 20B makes about
300 HP in normally aspirated form. (it was turbocharged in the Japanese
car it came from (never sold in the US). I've been flying an RV-4 with the
Mazda 13B two rotor engine for 15 years, 1850 hrs. TT.
Very hot day (93 F and high humidity) but ground tests of the cooling
system had gone so well that I was confident of cooling in flight.
Plugged in and secured the radio and transponder in the panel (which for some
reason I had neglected to do until this morning) and they both worked with no
problems, always a pleasant surprise.
High speed taxi tests had already been completed and the P-factor was no worse
than the RV-4, in fact I think it has less. This may be premature because
I haven't done a full throttle takeoff yet. The RV-8 has 1.25 degrees
right offset which I think helps a lot. The RV-4 has no offset.
First flight was done without wheel pants or main gear intersection fairings.
Just to make sure there were no surprises, takeoff was done at the same fuel
flow as the RV-4 at WOT. I didn't note the manifold pressure but the
throttle quadrant was barely over 1/2 throttle. Ground run on the -8 feels
more stable than the -4 with considerably more rudder authority (it's physically
bigger so no surprise). The plane broke ground at about the same
point as the -4 but it feels like it levitates off rather than rotates off.
Probably due to the higher wing incidence on the ground than the -4 with the
short gear legs but also due to the longer wing. I had extended both wings
by about 18" so the wing loading and span loading are less than on the -4.
It has about 13% more wing area than stock. This was actually the second
time the -8 had air under the tires since it had floated off ground about a foot
once before during a high speed taxi test.
Airspeed was increasing rapidly after lift off but the ASI was not matching the
visual ques. Normally I expect to see 120 mph at the end of the
runway (2700 ft) but ASI shows only 80. Too late to abort but the airplane is
climbing & sounding very nice. I had been doing a lot of
seat-of-the pants takeoff and simulated dead stick landings (in the -4) in
anticipation of today's tests so I would feel comfortable in the event of
partial or complete panel failure (Blue Mountain EFIS1 with only a
standard ASI for backup). Climb to 1000 feet felt effortless even after
throttling back to 8 GPH. I notice that I'm hunting for information and
not absorbing much due to the very different instrument panel.
Remembering that the EFIS1 has the primary ASI in a speed ribbon format, I hunt
for it and see 0 MPH when I finally find it. The EM2 (an RWS engine
monitor with backup ASI, VSI & Altitude) shows the same airspeed as the
Van's steam gauge, now about 100 MPH. First squawk of the flight and this
means I will do the first landing sans airspeed indicator. I can't seem to
locate the GPS ground speed on the display either. Glad I did all that
practice.
Time to settle in and start evaluating engine performance. I had taken off
with the engine fairly warm so I was not surprised to see oil & water temps
nearing 190 F after climbout. I continue collecting data hoping the
temps will start coming down but it is soon apparent that they are stabilizing
at about 200 on both oil and coolant. Very disappointing, since they
had been well below this on the ground when at the same fuel flow I was
currently flying at (I had backed it down to 5.75 gph by this time).
The plane itself is flying beautifully. The aileron trim is able to trim
out a very slight left wing heavy tendency and the ship feels like it is gliding
through the air effortlessly. No surprise, the plane feels just like an RV
(Magnificent!). At this speed (guessing about 135 mph) the roll response
is only slightly slower than the -4. The ailerons were extended with the
wing so the RV feel has been preserved. I've completed a wide circuit of
the pattern and in position to make an approach so I throttle back and I can
immediately tell that the glide ratio is significantly higher than the -4.
The longer wing is having more effect than I thought it would even with the
heavier engine. This -8 with a 20B ended up weighing about 70 pounds more
than the average one equipped with an 0 - 360 and fixed pitch prop and about the
same as one equipped with an IO - 360 with constant speed prop. Empty
weight (but with oil) is 1150 lbs. All the attention to weight control has
paid off. I throttle up for a go around and the FBW throttle responds
well, no detectable throttle lag at all.
The higher than expected oil and water temps are distracting me from data
gathering (Rats, I haven't had time to replace the EM2 engine monitor with a
data logging EM3 yet) so I make a few more circuits of the field and setup for
an approach. I crank in more flaps early to kill off the airspeed and
excess glide ratio and intentionally do not look at the ASI to avoid being
confused. Wheel landing touchdown is perfect and now I glance at the ASI
and see 40 MPH. Obviously wrong.
All in all, a great first flight. The RV-8 is going to be exactly the
airplane I was hoping for. Still a lot of testing and tweaking to
do.
Want to see and hear the 20B
run? Click this link:
http://www.youtube.com/watch?v
=IF95pMwAWpY
(video taken by Bob Perkinson at the
2007 Rotary Roundup)
NOTE! this page is in reverse chronological
order. Latest postings are at the top so that returning dial-up folks
won't have to wait for everything to load to see the latest.
Welcome to the Official Project page for Tracy's 20B
RV-8. The engine was built by Bruce Turrentine,
and other parts are slowing filtering into the shop. We will use this page
to keep you updated on our progress.
(If all photos do not load at first, hit
the REFRESH button on your browser toolbar).
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| 3/10/07 The Peterson oil filter gives
you complete freedom to locate it in any available space. Here is is
shown with an Adel clamp mount on the gear drive adapter plate. |
Here are the two diffusers I made for the
radiator and oil coolers. The one on the right is the oil cooler and
this shape and configuration has been well proven. The rad diffuser
is a new design that I hope will work well but is not yet tested in
flight. |
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| The two round inlets on the James Aircraft "Holey
Cowl" mate up with the two diffusers. This is the Lycoming version of
the cowl. James AC also makes a cowl for the rotary which uses the
open space under the engine for heat exchanger
location. |
The exhaust header was sent to Jet Hot for ceramic
coating. I chose the Jet Hot 2000 process (good up to 2000 deg F)
instead of the more popular chrome-look version because the chrome finish
version is only good up to 1300 degrees. Rotary exhaust headers get
a lot hotter than that. This should reduce under-cowl
temperatures significantly. |
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| I used another "shoe-box" style manifold that
limits the runner length to around 11.5" If kept clean, this
still gives good results. 16" would be better but room is
always a problem. Notice the lack of throttle cable. The
throttle body is an RX-8 part and is fly-by-wire. FBW controllers
will soon be available from RWS. The black line leading to the
plenum is the manifold pressure connection for the EC2. |
Still a lot of details to clean up at this point but all the
basics are in. The vertical canister next to the Griffin radiator is
an oil accumulator. It is included in this installation to
filter out the rather harsh pressure pulses from the gear type oil pump
which can cause problems with oil coolers made from AC evaporator
cores. They are made from thin wall aluminum and there have been a
few failures due to the pulses causing metal fatigue in the tanks of the
cores. |
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| 10- 27-06: The 20B RAN as part of
the Rotary Roundup 2006 festivities. The
20B sounds VERY different compared to the 13B. (It's a GOOD
difference!) Why this should be is kind of a mystery. |
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| 4/14/2006 - Tracy is creating a LOT
of dry wall dust in the hangar- something to do with creating molds
for the cooling ducts. This is a LOT of work for a one time use
mold, but that is the plan, according to Tracy. This is the mold for
the radiator. The oil cooler mold is also complete but I don't
have a photo to post yet. |
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| January 31, 2006: Tracy gave me
this photo today. (What you can't see is all the bead board wood
fabrication that is going on just to the right of this photo. I
GUESS that is a step up from the hairspray can that we used to fly on the
RV-4). Anyway, he didn't give me any details about the photo, but
here it is.... |
| December 22, 2005
There has been a lot of progress on the -8 but most of it does not lend
itself to photos. A lot of fiberglass work (yuck), design work
on cooling system, canopy skirt trimming/fitting/trimming again/etc
(double yuck), instrument panel planning/cutting/fitting/etc (it is
now complete), firewall & fuselage insulation & sound
proofing. It isn't apparent in the photos but the engine mount has
been replaced. Originally I had planned to install an RD-1B gear
drive (left hand rotation) but change plans to an RD-1C with right hand
rotation. This required an engine mount with opposite offset.
It would have been suicidal not to make this offset change considering the
enormous P factor that the 300 HP 20B will have.
Oh yeah, my brother Barry and I also built the hydraulically
operated hangar doors on the south hangar so I'll have room to
assemble all these airplane pieces and Barry can get more use out of that
Kolb Twinstar (located behind the RV-8 in the left photo below). |
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| After looking at how the cooling ducts would be arranged in
the cowl, I decided that the James Aircraft "Holey Cowl" with
the round inlets would be much easier to work with. It is also a
little longer than the stock cowl so it will require a shorter collar
behind the spinner. Remember that the 20B is about 6 1/2 "
longer than the 13B. The cowl has only been roughly trimmed to
fit in these photos.
I bought the custom exhaust manifold in the interest of actually
getting this thing done. (thanks to Kevin Lane). |
View through the left side cooling inlet.
No, it wasn't snowing in my hangar. That's fiberglass trimming
residue on the exhaust manifold. Tape covered all engine ports
during this operation. After working with the RV-4, the -8 is pure
pleasure with all that room. The 20B looks kind of like an O - 540
with all the cylinders removed. Plenty of room for oil & water
coolers on the sides. Oil cooler will go on this side. |
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| View through right side cooling inlet. The single
Griffin radiator will be mounted parallel with the motor mount
tubes. The air duct will be a wedge shape routing air to the outside
of the rad. Rad is a GRI-2-28185-X ordered from Summit
racing. I know it will cool a 13B and I'm hoping it will do well on
the 20B. |
Front view of the "Holey Cowl". The Lower
inlet for the Lycoming carb has been amputated and the lower chin-line of
the cowl cleaned up. That lower scoop on the cowl is the only thing
on an RV that isn't pure visual poetry (IMO : ) If you are using the
stock cowl, order the IO - 360 version which does not have the scoop. |
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| January 24, 2004: Truly a
momentous day in my book - Tracy resumed work on the RV-8
today! I bucked a few rivets and now wing 1 is on the bench for
closure. Tracy's decided to make Sunday "RV-8 Day". One
day a week is certainly better than zero! He also trial fit a Renesis
crank angle sensor on the 20B. Fits perfectly and 2 lbs lighter than
the 13B set up. |
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| December 30, 2002: Engine Update:
The modified Conversion Concepts engine mount is fitted and
installed. An oil pan solution has been developed - Tracy plans to
use the 13B oil pan with modified engine mount. The 20B intake
manifold has been developed and is under constructions, including the fuel
rail. |
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| Plane Update: Interior floor skins
are in (including the dreaded nut plates). Canopy frame is fitted and
installed. Landing gear installed. Canopy is trimmed (don't ask how
much plastic dust this created), cut and drilled to the frame. |
| September 22, 2002: Tracy has the front
rudder cables hooked up and has basically completed the fuselage floor and
walls, with the exception of the rear rudder pedal assembly (good thing I
asked him about that... he "forgot"!). He's been working
on perfecting the curve for the front luggage compartment (I LOVE that
phrase!) lid. Looking good so far! |
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| September 3, 2002: I was working on the
web site when I detected the familiar sound of a "come along"
being used in the hangar to hoist something really heavy. I grabbed
the camera - ran down the stairs and found Tracy with the 20B as seen
below. He'd just received a drawing of the proposed engine mount
plate from Fred Breese; made a wooden template and was fitting the
template to the engine. |
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| September 2, 2002: Barry and Tracy finally
removed the 13B from the "donor mobile" (that project only took
8 months!). The best news is that the spare RX-7 is now in the
hangar and out of the yard. |
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| August, 2002: Back on the RV-8R after
Oshkosh. Tracy is making progress on the floor and wall skins.
The RV-8 has a "double walled" fuselage, which is really nice,
but involves installation of a LOT of nut plates. He also installed
the flap linkage and actuator. |
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| June 23, 2002: Even if nothing else is getting
done on this project, we're doing a good job spending money on equipment for the mythical
rotary powered RV8R. We are now the proud owners of a Blue Mountain
Avionics (www.bluemountainavionics.com)
"glass cockpit". I continue to be amazed at the number of
hours that can be spent admiring new equipment instead of actually working
on the plane :) |
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| The Blue Mountain arrives. |
The only difference between the men and the
boys is the cost of their toys! |
| May 3, 4, 5 2002 : Bernie Kerr, Rob Kermanj,
Bob Brumwell, Barry Crook and Donna Crook all pitched in (with
doughnut delivery support from my Dad and step Mom) to help get the walls
up on the hangar and the floor painted. We can't thank them enough
for coming the "Hangar Building Party". See the results
below. (This was Bernie's idea but there may be method in his
madness. He is putting a rotary in an RV-9 and maybe, if the hangar
gets done, Barry can start working on the long awaited RWS engine
mounts... starting with the RV-9/6/7 series aircraft). Now.. how long will
it take before we get the doors installed? |
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| Hanger wall #1 ... completed |
Note "swinging" design to all for
flood water flow through and painted floor. |
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| Barry, Donna, Rob, Bob, Tracy & Bernie |
Bob and Rob on the move |
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February 2, 2002: More progress on the hangar - the roof is complete
(see photo below). The tiny figure in the photo is me - that provides an
idea how large the building is. Looks like it will be a wonderful
location for the annual Fly In this year. Tracy also completed the
wing extension on wing #1, plus fabricated all the parts for the extension
of the 2nd wing. |
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January 20, 2001 - When you build more planes, you have to build
more places to store them. Tracy focuses on the new hangar for
much of December, but went back to giving the RV-8R the attention she
deserves this month. He is making excellent progress on the wing
extension on wing #1. |
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12/25/01 - New hangar in its "modern
Stonehenge" phase. |
The wing was extended 1 additional rib bay as shown
here. The added length is 12.75 inches per wing. |
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Wing spar extension |
The RV-8R as she looks today. (Shop getting crowded) |
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November 25, 2001 - Finally completed the last piece of the tail
feathers and ready to start the wing lengthening project. Also
making progress on putting up another building at Shady Bend to store the
various airplanes that won't fit under the house. (Laura's Note:
I've decided Tracy has a really rough life... too many airplanes to
store!!!! What do I have to do to get too much jewelry to store :)) |
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September 9, 2001: Completed the vertical stabilizer tonight
and hung it up to keep the horizontal stabilizer company. On to the
elevators. Will be posting the rationale behind extending the wings
in an upcoming update. |
October 21, 2001 Completed Right Elevator (this
"interior" picture was taken for our builder's log.
Elevator is now assembled... and a thing of beauty, I might add) |
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September 2, 2001: Completed the horizontal stabilizer. I set
my first rivets on the plane last weekend, and, considering I had not
riveted since we built the RV-4, I did a good job! They even passed
the Otter Inspection. |
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Horizontal stabilizer completed. |
Tracy's "zoot" lightweight landing gear.
It sure cost a lot of money to save 12 pounds! |
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August 19, 2001 Progress has been slow on the
RV-8R primarily due to the oppressive Florida summer heat. Gee,
seems like in the winter, progress is always slow due to the cold.
Does anybody besides me, see a problem here? Like.. why didn't Tracy
build a heated/cooled workshop? Anyway, we've also had a huge
response to the EC2 upgrade offer, which is taking Tracy's time. He
is also wrapping up 2 magazine articles - one for KitPlanes and one for
CONTACT! Below are the latest updates from
Tracy. |
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The horizontal stabilizer mounted on the jig.
Ready for skins. |
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| Skin dimpled and primed - ready to assemble |
Original shipping carton - "High
Value" is right! |
| July 11, 2001 Apparently our
kit was truly on a slow boat from China - or maybe the Philippines - but
it finally arrived today! Laura was in Atlanta working, so no photos
were taken of the truck arrival or the team of 4 friends and neighbors who
helped with the unloading process (unfortunately). Laura has already laid
down the law - THIS time there will be no airplane parts in the living
area of the house (Yeah - right. How long will that last?). Now the
REAL fun begins... |
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| Airplane in a box. |
Uncrating the RV-8R as the RVotter
looks on. |
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| Looking at the
internal structure brings back memories of building the RV-4. The RVotter
looked like this after about 2 years of steady work. |
Contemplating the first mod to
the RV-8R. The wings will be stretched 1 foot each. |
February 25, 2001: 1st parts of the RV-8R (the name of
Tracy's RV-8) completed
February 6, 2001: Both the engine and the empennage kit
arrived on the same day. Tracy's brother Barry is also building an RV-8,
and his empennage was also delivered.
December 26, 2000: We did it!! The
RV-8QB has been ordered. Laura wrote the big check on Christmas day - she
required a glass of wine to get her through the trauma (and this from a girl who
probably only drinks 4 glasses of wine in a year).
Engine Installation Drawings
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Real World Solutions, Inc
