Alley Cat
Several times over the years, the Alley Cat has been referenced at out
flying field as having been a good design. I had one in the late
seventies and it remained in my memory to be a favorite. It was
the only plane I've built that required not one bit of trim, which in
itself says that the design had some merit.
It was a .40 size low wing
design by Ed Keck and produced by Southern RC. A half dozen or so
were built by locals. Others have related similar, that several
Alley Cats were built in their area. Ironically, there were
more Alley Cats locally than Chaos or Taurus.
A couple of weeks ago, one of
the old timers at our field, a retired orthopedic doctor, asked if I
wanted the Alley Cat stored in his attic. My mind raced for a
moment... gosh, it would be a hoot to fly one again.
Then as usual the counter
arguments came to mind, it was a tricycle gear plane and not that
suitable to our rough field, it was glow and I've been moving away from
glow, it was a .40 size and I've been into larger planes, it was a
sport/pattern plane and I've been into sport/scale.
The course of thought
reversed again to an awareness that I did have an unused engine and
radio gear and an empty building board. In the end, the pros to
accept
outweighed the cons. It would definitely be a hoot to fly an
Alley Cat again. That one had survived the years was good fortune.
The first action after
getting the plane on my board was to asses it needs. It had
suffered a mishap and was in a stage of repair when put into
storage. The damage to the underbelly just aft of F3 had been
repaired and filled but needed sanding and repainting. The nose
wheel had very minimal and inadequate left turn and the strut had a
slight port side cant. The airframe, more especially the wing
seemed a bit heavy perhaps due to the automotive enamel paint job....
though I had to remember that the wing contained the struts and wheels
for the mains. The control surfaces were fitted very tight and
didn't have a lot of movement. The canopy had shrunken an popped
the joint around it. Otherwise the plane was in
excellent condition. Sighting the wing, there was no hint
of warp. The doctor was/is one of the most meticulous builders I've
known.
Second step was to retrieve
the intended engine and verify it worthy of the refurbish. The HB
.40 PDP had remained for thirty years in an American Revolution
helicopter hanging on the wall. Expectantly it was froze but
unexpectedly only a very slight amount of heat was needed to loosen
it. The Perry carb needed no heat for the barrel to move
easily. There was no rust at the intake valve area so after
having oiled well and found to flip freely, no disassemble was done and
it was mounted in the test stand where it started on the
second hand flip.
There were some carb issues
however as the top end didn't seem to richen properly and it wouldn't
idle so the carb was pulled and taken to the bench. For those
who remember, the Perry carb has a very small C clip best removed by
inserting the carb in a sandwich bag to prevent the C clip from flying
off. I suspected debris in the
small slit of the idle circuit but was surprised to discover that this
Perry had a screen around the idle circuit, I'd not seen that
before. After cleaning the
screen, a small flashlight was aimed into the barrel to observe the
needle seat opening and it looked to be too small with only a sliver of
light getting through. Blowing it out revealed a
better sized hole and the obvious revelation that something there had
been the source of the carb problem.
Refitted, the motor started
easily, with top end now able to be richened and with a slight bit of
leaning of the idle mixture, the engine was purring 13,200 top and a
good reasonable idle and smooth transition... the engine was
fine. It really
didn't have much running time on it. The American Revolution was
sold as a combo with engine and initially was released with a K&B
.40 but owners were encouraged to refit with the HB .40 for better
performance and I'd done that but didn't fly the chopper much after
doing so.
A new motor mount was in my
junk box that fit the engine but with different hole spacings than
existed in the firewall so the mount was drilled to match the
existing mounting holes in the firewall.
The original tank was not
with the plane so
required a trip to the LHS for an 8oz tank and to Walmart for a can of
touch up paint. The nose wheel strut was removed and replaced
with a
straight one from the junk box and given a flat spot to produce a
steering arm position that allowed adequate turn in both
directions. The steering arm locking screw with a slotted head
was traded for a hex socket head. The tank was fitted with longer
exit tubes than come stock so that the tank could be parked aft about
an inch to allow for steering arm travel and have the tube extent
through the firewall just above the radial engine mount. A heavy
nylon line was
fitted around the tank both to facilitate pulling it out and anchoring
it
from moving forward.
When preparing to install servos, a problem quickly became
evident. With the servo rails aft in the wing cavity, there was
not clearance between new JR servos and the aileron torque rods.
This left two choices, move the servos fully forward in the bay or use
other than standard servos on hand. Moving the rails would mean
extending
the rudder and elevator push rods and keeping them below the aileron
servo and push rods and above the battery and receiver making it
difficult to get at the battery and receiver. Then I remembered
that I was working with a 70's vintage plane, maybe I should check some
70's vintage servos for fit. Yep, some old Futaba servos would
work. New connectors have now been soldered on and the servos
excercised and working fine.
The servos have now been installed for rudder/nosewheel, elevator and
throttle. The linkage for rudder and elevator existed but
throttle and nose gear got reworked. An interesting aside
about the throttle linkage is the good doctor had decided to gang all
three servos beside each other rather than two aft with the throttle
servo forward and cross wise, probably because of the likelhood of it
fouling with the aileron servo in the wing. Doing so however was
a close fit and left inadequate space for a long enough throttle arm to
get the required travel. To remedy, he obtained greater throw by
actuating an intermediary arm having greater throw... quite
clever. This linkage employed a technique sometimes used in those
days before throws could be set in a transmitter. The scheme used
a quick link on the control arm but with no set screw so that the
linkage rod slides fore and aft through the quick link. Each side
of the quick link on the rod are position a spring and then a wheel
collar so that the springs on both sides of a quick link compensate for
any overthrow either direction to prevent loading the servo. Of
course modern radios don't require those kind of heroic efforts as the
travel can be adjusted simply within the transmitter.
For the reader who might be interested, the other way that was often
employed on throttle linkage was the use of a blank servo disk having
no holes. It was a bit simpler with no springs or wheel
collars. A quick link was mounted to the control rod and
tightened in approximately the position needed. The throttle was
positioned fully open and the servo to high throttle position and at
that point, the quick link pin was scribed accross the surface of the
plate scratching an arc. Repeated for low throttle position left
two arcs with an intersecting point that was drilled for the quick pin
mounting position. It worked great but the plate was large and
there was no room for the plate with the three servos side to side in
this installation.
Yet to do is fit a servo to the mount in the wing for the ailerons.
Following that are the filling of the canopy edge cracks and finally,
the paint touch up. I'm in hopes that the canopy will not have to
be removed and because the fuelage all ready has a two tone paint
scheme, to possibly repaint over the trim color and expand its area to
cover the repair area. That way, no paint matching will be
critical.
With engine and all radio gear in place, I put the wing on to ensure no
fouling of the aileron linkage and when setting the plane on the floor,
it quickly settled on its tail.... hmmm a nose wheel plane isn't
supposed to do that. Six ounces added to the engine compartment
were needed just to get the nose to stay down. Likely 8-10 will
be needed for flight, which will put all up weight about 6lbs 2-4
oz. That is 18-20oz heavier than the .40 size P-51 that I
recently refurbished. Of course, the P-51 is smaller with less
wing inches. I've no recollection of having to add so much weight
but that was too long ago to remember. Most likely the issue is
the automotive paint but I'll certainly check the aft of the plane for
dirt dobbers or a rats nest. The plane originally had a tuned
pipe that may have added a fair amount of nose weight.
I'm a bit disheartened.... it realy needs lightened but I'm not willing
to refinish it. I might save an ounce or two by moving the servos
forward but that means reworking all the linkages and that doesn't
thrill me. Have to sleep on it.
After having slept on it... the numbers were ran showing wing loading
with the additional weight needed will be around 23 oz sq ft.
That is a reasonable number that should produce good flight so perhaps
I was just dealing with the shock factor of having to add 8-10 oz...,
which no modeler likes to do.
Update: the paint repair is finished and a final balance done and 12 oz
are needed in the nose. If there were space for the flight
battery under the fuel tank, less would be required. Will have to
look at such a possibility.
And... the work
continues.
December 2010
The Alley Cat flew again. It was faster than I'd recalled
though I'm certain the HB-40 is a stronger engine than on mine years
ago. Even though the plane required 3/4 lbs of lead in the engine
bay, the vertical was really good... not unlimited but given that the
plane was fast anyway, it would climb a very long way before running
out of steam. The roll was slow due to the tight fitted ailerons
but it was in fact a hoot to fly one again though I no longer enjoy
flying a plane as fast as it scooted.
February 2010
It was fun to fly the Alley
Cat again but I had no room for it and it wasn't a plane desired to
keep in the hanger so as per my discussion with George who gave it to
me, I passed it to a worthy candidate who needed an intermediate
aerobatic trainer. He is very happy to get it and is ready in his
development for it.
