|
Empty Weight: |
325 lbs. |
| Gross
Weight: |
650 lbs. |
| Wing Span: |
27.2 ft. |
| Wing Area: |
108 sq.
ft.. |
| Engine:
|
447 Rotax |
| Cruise
Speed: |
70 mph. |
| Stall
Speed: |
27 mph. |
| VNE: |
85 mph. |
|
Construction: |
wood and
fabric |
| Building
time: |
400 hours. |
approaching it has picked up quite a bit. We now have
shipped about 240 kits and close to 700 sets of construction
drawings worldwide with a reported 60 aircraft completed and
flying. An accumulated flying time of several thousand hours
seems to have proven the integrity of the basic design. Several
of our overseas builders are now enjoying flying their projects
and a couple are featured in this issue. We will attempt to get
this issue out to all 700 builders even though we only have
about 250 paid subscriptions. The newsletter 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 complete stories.
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. We
sincerely hope all of you will subscribe. Back issues are
available for $3.00 per copy.
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.
SPINNER PROBLEMS
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.
ULTRA-PROP SERVICE BULLETIN #2
Historically, propeller 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.
Spinner Solutions
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 of a
 front
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.
Fuel Funnel
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 beautifully.
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.
Test Flight
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 looking at 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 done.
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
flyer.
Rotax
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 certain.
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 all.
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
test flights.
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 modifications.
http://communities.msn.com/BobcatandSupercat
http://www.foxberry.net/bobcat_flyer/
Bowdler Aviation, Inc.
1370 Howell Rd.
Beavercreek, OH 45434-6828
(513)426-9868
Brief: Supercat
CATSCRATCHES
Newsletter for Bobcat and Supercat builders. I do have all of the old newsletters and copies are
available at:
kenneth@tctelco.net
|
