is quite important as it is the only means we have of
communicating and sharing of ideas and problems. I will
again ask for contributions from you whether it be hints or
Let's hear from you!!
We have had some problems with
subscriptions since we switched to using a computer for our
mailing lists and for this we apologise. The old adage of
"garbage in-garbage out" seems to be holding true for us as
well. If you have paid for four issues and did not receive
them, please let us know. There have been several important
intems in the past couple of issues that I'm sure you would
want to know about including a sample weight and balance and
flight manual in issue #7. A $12.00 subscription ($16.00
overseas) entitles you to the next four issues.
Bobcat - Supercat
108 sq. ft..
wood and fabric
We sincerely hope all
of you will subscribe. Back issues are available for $3.00
Both Kay and I made the
annual trip to Oshkosh this year and very much enjoyed the
show and meeting with our friends. The first two or three
days were almost unbearably hot but it cooled down later in
the week and turned out to be one of the best conventions
yet. The "Cat" flew hard every day. I now have tached about
180 hours on this aircraft which is much less than I would
like but it seems there is never enough time to go out and
have fun. I did install my side doors recently as cold
weather has finally hit Arkansas. The doors keep me qite
comfortable down to about 30 degrees outsid air temperatoure
so I have still not installed cabin heat. Tempertures here
in our part of the country seldom are below 30 degrees.
Although only a few of you
are using the Ultra-Prop, I thought I would include the
following service bulletin from Competition Aircraft so you
would be aware of the problem.
spinners have been plagued with problems. Almost every
aircraft manufacturer has had difficulties with cracks and
departing spinners because of the enormous vibration energy
at this piont. Service bulletins and "improved spinner
assemblies" are common in the industry. Every hole and
cutout in a spinner or its bulkheads invites stress cracks.
Despite our best effortst o
make the polyester spinner installation on the Ultra-Prop
100% positive, a few reports of spinners coming off tractor
installions and damaging the blades leads us to issue this
service bulletin. The spinner should not be used on
tractor installations. If it comes off, the blade damage
could affect the ultralight's performance during a critical
phase of flight.
On pusher installations,
the pilot must make his own decision with regard to
installation of the spinner. Tests have shown no damage
caused by a departing spinner. Ultra-Prop kits will continue
to be shipped with a spinner, since we don't know how it
will be installed.
All owers of record who
have returned the Owner's Warranty card have been advised of
this service information.
Additional product or
service information can be obtained by calling or writing
Competition Aircraft at 11110 Gopher Mine Trail, Grass
Valley, CA 95949. (916)268-3048.
Now that the service
bulletin on Competition Aircraft's spinner problem has been
printed, I will relate some of our own problems with spun
aluminum spinners. As most of you may know, the company that
manufactured these aluminum spinners has withdrawn them from
the market as most all the units experienced cracking after
a short time. I personally went through four of them in
about a year of use. Not only were they fairly expensive
($50 each) but were also very time consuming to cut and fit
around the prop hub. It would take me an aveage of 3 to 4
tedious hours to cut, sand and very carefully polish the
cutouts to eliminate possible vibration cracks. even with
all that attention, a couple of them only lasted a few hours
before coming completely apart. The aluminum back plate also
was prone to cracking around the prop bolt holes although we
eventually found a solution to that problem.
Well folks, we have finally
come up with a spinner unit that works well and, although
not exactly cheap, is less expensive than the aluminum
cones. the major problem with the spinners has been the lack
stabilizing bulkhead but due to the variety of propeller
thicknesses it was virtually impossible to manufacture
enough different sized bulkheads to accomodate all of them.
The solution we finally
devised is illustrated in the following sketch. A one inch
O.D. aluminum tube is permanently mounted in the nose of the
spiner and when the cone is installed over the prop, this
tube protrudes though the 1" I.D. hole in the prop flange
and prop. This virtually eliminates the nose cone "wobble"
which was causing the vibration cracking.
The spinner and backplate
are molded from high strength ABS plastic and are more
resistant to vibration cracking than the spun aluminum. Note
the .050 aluminum backing plate circle used to reinforce the
the backing plate. The backing and reinforcement plate are
provided with the 1" hole already drilled for different
configurations. the nose cone is attached to the backing
plate with 3/16" AN stainless steel screws, AN washers and
AN lock nuts. These are all prvided in the kit along with
complete instructions. The nose cone will accept most any
type of paint. Price for the complete spinner kit is $40.
A really handy item which
some of you may not know about is a fuel/water separator
funnel appropriately named "Mr. Funnel". Introduced at
Sun-N-Fun a few years ago it is an item I can't seem to do
without. I never put gas in my tank unless it goes though
this gadget. It utilizes a special thrmoplastic coated
stainless steel base with a hydrophobic mesh separator
membrane that has an affinity for petroleum but repels
water. Whew!! Despite the fancy nomenclature it works
Along with the fact that
fiberglass tanks are much less likely to collect
condensation diligent use of this funnel should dramatically
reduce the possibility of water contamintion in the fuel
system. There are two sizes available on the market but the
smaller one (5 1/2" bowl diameter) is your best bet. They
cost around $10 and are well worth the investment. Wicks
Aircraft Supply as well as most other aircraft parts houses
have them in stock. To my knowledge, I've never had a fuel
contamination problem while using this system. Incidentally,
while on the subject of fuel, I have noticed that lower
cylinder head temperature readings using regular leaded gas
than I do with the higher priced unleaded.
I recently had the pleasure
of test flying a supercat built by Dr. Robert Yoak from
Benton, Kentucky. After a hospitable invitation from the
good doctor, Kay and I drove over on a weekend and really
had a good time. Doc's plane is powered with a 447 which
started up very nicely and ran well though the two or three
short flights I made in it. Flight characteristics were very
similar to our prototype but there were a couple of
exceptions which prompted the writing of this article.
Upon close examination of
the plane, I found a discrepancy in the tail surface flying
wires that might be worthy of mention here. The two aluminum
tangs that connect the bottom horizontal stabilizer flying
wires to the fuselage bracket "E" as shown on plate #10 of
the construction drawings were installed incorrectly. After
the plans again, I can see how the mistake could easily be
made. Dr. Yoak had both of the tangs installed on the top
side which produces an uneven pull on the "E" bracket. I had
intended that one of the tangs should be on the top and the
other one on the bottom to produce an even pulling force.
This may not be a critical point but the tangs should be
installed correctly to insure even pressures.
Hopefully, the sketch on
the following page will show how this installation should be
The one thing that really
caught my attention in test flying this plane was the fact
that I had absolutely no ground steering control! It became
immediately obvious as I started taxiing out to the runway.
The only directional control I had was with differential
braking. Rudder pedal input had no effect. We played a bit
with the springs that he had attached to the rudder horn and
the tail wheel control arm but with no success at all. I
thought that we could stretch the springs enough that the
tail wheel would move when rudder was applied but no matter
how tight they were stretched, the tail wheel would not
respond. I had heard of this complaint fron other builders
but didn't realize the extent of the problem until I
actually tried to ground steer one of these puppies with the
"tension only" type springs. It just simply can't be done!
The "fix" which I've been
using all along (and failed to pass along in the newsletter)
is the use of the type of spring employed by the "big boys"
. Instead of tension, it is a compression spring. they are
available in most good hardware stores and are sold as
aluminum screen door springs (usually in a repair kit). The
sketch on the following page illustrates what they look
like. Short sections of small chain and "S" hooks are used
to connect the springs to the rudder horn and the steering
arm. The chains are used for tension adjustment.
The springs should be quite
tight to give adequate ground steering
control. An advantage that might not be immediately ovious
is that using this type of spring eliminates concern over
breakage of the spring connection. If it does break,
directional control may be sloppy but not totally lost.
At any rate, by holding the
brakes and applying full power, I was able to get Doc's
plane in the air from a grass runway adjoining the paved
surface. At full power the rudder takes over immediately and
provided enought directional control to fly off grass. But
please do as I say and not as I do! Don't attempt test
flying without adequate ground steering. Set up correctly
these Cats exhibit really easy ground steering but can be a
real bear if not done properly.
One other note on Dr.
Yoak's plane.When I flew it, he had not yet installed the
aileron gap seals so I didn't know what to expect for roll
control. I was a bit concerned on the first test flight but
the ailerons seen to work just fine. Hope the Doc won't
think I'm being too critical of his project as I think that
with a few adjustments it will prove to be an excellent
Very little news to pass
along about Rotax engines in this newsletter but a couple of
things might be of interest. A good friend of mine that flys
a Weedhopper(?) with a 277 Rotax has had some problems with
the pins that keep the carburetor floats in position. He has
had to replace both the pins and floats after a reported
several hundred hours of flying time. Apparently, vibration
is again the culprit causing the wear. The steel pins were
extremely worn as well as the tube manufactured inside the
floats. I tend to think the engine installation in the
weedhopper allows much more vibration than our "Cat" mounts
but it caused enough concern that I pulled the float bowl
off mine just to check it. Our's showed no wear so I snapped
the float bowl back on but I will try to check it as we
accumulate more flying time.
Another thing I learned of
only recently is that Rotax does not recommend scraping
carbon buildup from the cylinder heads every 100 operational
hours as reported in one of our recent newsletters.
Apparently, if you are using synthetic oil such as Bel-Ray,
very little carbon buildup occurs and the chance of a piece
of carbon droping into the cylinders and getting between the
ring and piston when you are scraping could cause more
damage than if left alone. You still may want to pull the
head every 100 hours or so and check the carbon just to be
We are mixing the Bel-Ray
at 60 to 1 per Rotax Suggestions and find that it works just
fine. If you do use Bel-Ray, it's much less expensive if you
buy it by the gallon. We try to keep it in stock, Price is
$22.00 per gallon.
A Determined Pilot!!
I've been intending to
write about Charlie Curtis from Millington, Tennessee and
his Supercat project for some time now and I suppose this is
as good a time as any. Charlie's story is a bit different as
he has a physical obstacle to overcome that I'm sure most of
us would find insurmountable. He is a paraplegic due to a
motorcycle accident several years ago and is confined to a
wheel chair for motivation.
before his accident, he was
a pilot and in recent years has taken up the fine sport of
radio control model airplanes to satisfy his flying urge. He
became interested in the Bobcat a couple of years ago and
decided that he wanted to build one in large part to the
fact that it appeared to be a large model airplane. His
courage and determination should be an inspiration to us
Charlie has completed his
project and the test flying date should be arriving shortly.
He asked me to fly the plane initially since we are located
not far from him. I got a call from him the other day
expecting to hear it was ready but of all the luck, his
house had burned down and was a total loss though his plane
was not damaged. As soon as he gets situated again, I expect
to hear from him and will be more than happy to make the
You may not be able to
determine from the picture of his cat on page 5, but he has
cut off a portion of the inboard section of the aileron
which enables him to pull his wheel chair up to the rear
spar of the wing. A small section of the right hand portion
of the cockpit side wall folds down and provides him
entrance to the cockpit. Rudder control is via a hand
operated stick although the stock rudder pedals are left
intact allowing normal operation. I have not personally seen
the aircraft but it looks really well built in the pictures.
Power is a Rotax 447 and the plane has all the latest
1370 Howell Rd.
Beavercreek, OH 45434-6828
Manufacturer no longer in business.
Newsletter for Bobcat and Supercat builders. I do have all
of the old newsletters and copies are available at: