What is it? |
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Blue Jay 7 is a highly modified Weedhopper USA, Inc Super Single model ultralight aircraft with Model 40 fuselage tubes. A Super Single is a 2-place airframe delivered with only one seat. This plane was originally christened "Misisipi Flier" by its former owner, whom I bought it from on May 11th, 2001 near Meridian, MS. For the next two months I did
a complete tear-down, inspection, and rebuild, replacing all degraded
hardware and improving, removing, or replacing questionable attachment
schemes for items like the pod, battery, and the owner-made center control
stick, changing it back to the factory location on the right hand side
of the seat. |
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| After a few flights, I discovering that the fuselage was twisted enough to cause a nasty imbalance in the wing's geometry if the wing struts were swapped one side for the other. I replaced all the old fuselage brace tubes, half of which were bent out of symmetry no doubt from a few too many hard landings by the previous own, with all new symmetrical tubing and trigonomically derived bends. The 11-rib wing has a span of 28 feet,
a surface area of 168 sq. ft., and is made from Dacron polyester sail
cloth. It can lift up to 250 pounds of pilot and "cargo," has
a maxium, full-throttle speed of 60 mph, a typical cruise speed of 40
mph, lands and takes-off at 30 mph, climbs at 500 ft/min, and has a range
of around 60 - 70 miles on a 5 gallon tank of regular auto gas mixed with
2 stroke oil at 50:1. |
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The frame is tubular
aircraft-grade 6061 T6 aluminum alloy with 0.095" walls on the front
braces (axle to engine mount brackets) and 0.065" walls for the rest
of the fuselage and wing struts. The wing's leading and trailing edge
spars at the wing strut attachment points and the central section of the
main boom have outer reinforcing sleeves. Everything
is held together with 1/4" and 5/16" military-grade (AN) aircraft
bolts, nuts, washers, clevis pins. |
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Weedhopper's are very stable, easy to fly, 2 axis craft (single stick controls rudder and elevator) with no aerilons or flaps. They are so easy to fly that I taught myself without any instruction. Doing so is not recommended. I simply spent a whole day running up and down Mecosta Morton's (27C) 2,000 foot grass runway west of Mecosta, MI learning how to steer on the ground. Then I started making little "crow hops" that grew higher and longer until there wasn't enough runway left to land. When that happened I was committed to the sky and circled back around at 200 feet off the ground for a perfect landing. Great Fun!! Note: The photo at left is Collegedale
Municipal Airport (3M3), not Mecosta Morton. |
First
Flight |
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On July 15, 2001, I hauled this yet un-named craft to the local airport (3M3) and spent a few hours in the morning practicing slow and high-speed taxiing, turns, and finally crow hops until I was confortably re-acquainted with the way this Weedhopper handled. The movie to the left documents my first extended, 100 foot altitude 'crow hop' down the 4,700 foot runway. This version of the movie was motion tracked and stabilizated in Adobe After Effects to remove the hand-held camera shake. Right-click here if you want to save this 3.8 MB MPEG movie to your harddrive. Otherwise click on the image to view in a new window. |
| When a corner of the notch, which was cut out in the wing by hand by the previous owner to accomodate the engine, ripped in flight in late November, 2001, the time had come to retire the red and black sails, even though the previous owner said were only 2 years old. They had become just to weak for safe flight having been exposed during those 2 years to the sun's direct and indirect UV rays while it was hangared in his open-ended hay barn. So, I promptly replaced them with the current Blue Jay tail feather design in February 2002. These new sails were purchased from Ron Gonci, owner of The Ultralight Store in Winchester, CA. He even custom made them with a properly reinforced engine coutout notch at no extra charge! It was at this time the plane was renamed to "Blue
Jay 7" due to the color scheme and because of a personal faith statement
where the anagram B = "Because," J = "Jesus," and
7 = the number of perfection. |
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The
Engine |
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BJ7 uses a 50 horsepower
Rotax
503, 2 cylinder, 2-stroke powerplant with a dual electronic Capacitive
Discharge Ignition (CDI) system, a GPL
electric starter, free-air cooling ram scoop, a single Bing 54 carburetor,
and a 65" Model B PowerFin
carbon composite adjustable pitch prop that's turned by a 2.58:1 type
'B' gear reduction drive. |
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The engine is mounted in the upright
position, an unconventional orientation compared to the factory standard
of hanging the engine upside down underneath the boom. |
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A heavy-duty, lightweight motor mount is custom made from various 6061 T6 aluminum bar with rubber Barry isolation mounts 9 1/4" apart. This photo shows the current mount using nylon spacers between the engine and the top mounting bar. |
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This photo shows the previous owner's mount using aluminum tube spacers with washers. This design allowed the washers to deform and bend down into the tube. |
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The rest of the engine mount's
structure is made up of two long angle brackets mounted to the boom with
saddle blocks. Two AN5 bolts go through the whole assembly with the front
bolt securing the wing's leading edge root brackets. Attached at the rear
of the engine to the flat upper surface of the angle stock are the muffler
hangers, Key West voltage rectifier/regulator, and starter solenoid. |
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The ram air scoop is a two-piece, fiberglass unit bolted to threaded cylinder head bolt extenders using large washers on either side of the scoop to spread the heavy vibration load over a larger area.
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New Magnecor
brand RFI suppressing spark plug wires are used along with resistive plugs
and caps to help reduce (but not totally eliminate) radio interference
in the aircraft communication band. The spark plug caps are secured from
vibrating off the spark plugs by means of a twisted, form-fitting wire
device made from a coat hanger. It is held by a bolt and washer to a threaded
cylinder head bolt extender. |
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This red sheet of plastic provides
a nice vibration and shock mount for a Mikuni
DF52-21-D dual outlet fuel pump. Regular 1/4" automotive fuel line
is used for the supply line from the tank and squeeze bulb primer (located
above the pilot's head), while blue tinted 1/4" urethane tubing routes
the gas up to the Bing 54 carbeurator. |
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Posi-Lock
connectors are used extensively to butt-connect engine wiring. A braided
copper strap can be seen just to the right of the yellow wires. It is
used to ground the engine block to the fuselage rather than a heavy gauge
insulated wire because a braid has more surface area than a wire and RFI
currents travel on the outside surface of a conductor. Therefore, a braided
strap helps reduce RFI noise. Sheilded audio cable is used for the tach
and ignition kill wires. |
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A plastic project box is used as a junction box for the four temperature sensor leads; 2 EGT and 2 CHT. Shielded, two-conductor audio cable is used to extend the probes down to the instrument panel gages. The farther two-piece aluminum project box contains a
Tomar Neobe
Dual-head Strobe power unit that drives two 20-watt strobe tubes.
Notice the use of ferrite 'clamshell' chokes here and several other places
to reduce RFI, especially on the B+ power supply lines. All this atention
to RFI reduction allows my Icom A4 radio to get down to a squelch level
of 2 (out of 9 levels) for clear, almost noise-free reception of weak,
distant signals. |
The
Cockpit |
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Blue Jay 7 has a fiberglass pod faring and plastic seat tank originally made for the Phantom ultralight and a homemade 3/16" thick Lexan polycarbonate windshield.
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A four-point racing-style seat
belt harness keeps you firmly secured in rough thermals (old photos will be updated soon). |
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A
carbon fiber panel made by fellow flyer Keith Murchison holds the following
instruments (top
left to right): Magellan Meridian Color GPS, altimeter,
dual CHT gage, tachometer, dual
EGT gage,
0 - 80 mph airspeed indicator, and an Icom A4 radio. On the bottom (left to right): ignition kill switches,
starter switch, carburetor primer, strobe
and accessory switches,
and coaxial power jack with its B+ lead wire wrapped around a clamp-on torroid choke . The GPS and radio use RAM mounts, each consisting of a RAM201 4" arm, a RAM202u12 ball base, and a RAM231 ball U-bolt tube mounting base. |
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The carbon fiber panel is about 3/16" thick, therefore needing this supporting framework to give it rigidity and a way to mount it to the pod. Note how the bolts for mounting the RAM ball bases serve double duty by also holding the frame's reinforcing corner joiner plates. The total weight with instrutments is 8 pounds. |
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A Power Sonic, 12 volt, 18 amp sealed lead-acid battery is strapped to the floor of the pod and to its left is a cigarette-lighter jack to power the GPS. A plastic go-kart seat replaces the factory sling backrest and foam padded plywood seat. The foam pad from the original seat and another extra layer of foam padding were added under the seat's thinly padded vinyl slip cover to give a good 2 hours of flying comfort. |
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Modifying the factory nose wheel
steering to extend it up into the pod was accomplished by bolting four, 6" extensions of of 3/16" x 1.5" aluminum bar stock to the front and back of the nose fork using the holes where the original steering tube was mounted. The steering tube was then bolted to the front of the extensions with spacers between each extension. This design has proved to be very strong, easy to assembly and disassemble, and required no welding. |
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The throttle is a standard factory clamp-on lever but uses an extra cut-down wing root bracket to form a cable support and "stop seat." |
Brakes and Gear |
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Blue Jay 7 has drum brakes
on the main landing gear, cable actuated by a modified Harley Davidson
motorcycle clutch lever mounted on the control stick. |
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4.5" diameter Azusa
brake drums were spot welded by the previous owner to the inside of the
main landing gear wheel hub, which in none other than standard Kenda 4.80
x 4.0 x 8 two-ply wheel borrow tires and rims. |
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The band brake pads are mounted to the fuselage via a 3/8 inch bolt running through the multi-junction bracket and two reinforcing plates. The end of the cable is then clamped to the free end of the brake band.
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The factory nylon bushings were replaced with 1"
ID x 1 3/8" OD x 1 1/2" long oil-impregnated sintered bronze
bearings. Two were needed for each wheel to span their 3" long hub/spindle.
They are kept from spinning by hex-head set screws threaded in to each
bearing with a matching hole in the standard 54" axle (solid aluminum
or 0.120 wall 304 stainless steel tube). |
Lighting
and Miscellaneous |
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This 20-watt xenon strobe
head, mounted on the front of the pod, is home-made from a 2" ID
PVC plumbing pipe end cap, a Perko
marine fresnel lens, and a 2" disc with a 1" hole to hold the
strobe tube. |
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This one is mounted at the top of the rudder. |
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Close up view of the faired wing struts and method
of attaching them to the main axle with stainless steel tangs. The fairings
are made from 4" thick blue Dow builder's foam cut with a home-made
"hot knife" and covered with vinyl house roof flashing. Click
"Strut Fairing" in the menu above for construction
details and methods. |
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I didn't like the wear and tear of the tail skid,
which is actually a rudder sail protector to prevent the rudder from scraping
on the ground and shredding the Dacron sail cloth, so I added this litle
caster wheel. |
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This airspeed pitot (pee-toe)/static pickup uses
1/4" galvanized steel automotive brake line mounted in a small length
of 1" C-channel stock bolted to the left wing's wing strut junction
bracket using a quick disconnect wing nut. The plugged upper static tube
has eight tiny holes drilled in its side and a rubber disc to adjust
ambient air pressure. The lower pitot tube has a larger 3/8" tube
added to help minimize changes in ram air pressure due to changes in wing
angle of attack. 1/4" ID clear vinyl plumbing line is used to route the two pressures to the ASI gage in the cockpit. |
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When the wings are folded for transport and storage, the whole assembly simply lays in the sails as they are wrapped around the wing spar tubes. The adjustment collar on the static tube is used to adjust static pressure to compensate for inaccurate readings. Air moving over the disc creates lower pressure behind it and higher pressure in front of it. When placed in front of the static port holes, the lower pressure behind the disc increases the indicated airspeed. When placed behind the holes, the higher pressure in front of the disc decreases the indicated airspeed. |
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Here is a simple, but very effective in-flight adjustable elevator trim tab. The tab/flap was made from a single sheet of thin aluminum, bent and riveted to form a wedge shape with upward and downward protruding 'ears' at each end used for attaching a return spring and an actuation cable. The hinge is a 1" OD tube riveted to the tab/flap. 1" ID PVC plumbing fixtures serve as bushings on each end of the tube, while 1" wide straps of sheet aluminum bent around each bushing and bolted to the trailing
edge of the elevator with 10-40 machine screws holds the assembly in place. |
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The actuator cable is nothing more than a common
bike shift or brake cable with a shift lever mounted on the center fuselage
brace in the cockpit. A cable adjuster is mounted to a 1" 'L' bracket
to provide a seat for the cable housing. |
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A return spring that doesn't overpower the friction of the shift lever is the last part of the system. |
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All low speed aircraft exhibit what's known as P-factor,
a propellor inducted yawing to the right or left that can be "tuned
out" by this in-flight adjustable rudder trim system. Instead of
a tab/flap, a simple tension spring is used pull the rudder in the direction
that compensates for the "automatic" turn. Its tension (pulling
force) is adjusted by another bike shifter cable with its shift lever
mounted near the elevator trim lever. Varying the position of the 'L'
bracket with its cable adjuster tunes the base amount of tension needed
to keep the plane in a hands-off trim condition at the minimum cruise engine
power and by adjusting the trim lever the spring
tension is increased to trim for higher engine power. |
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To transport BJ7 from my home garage "hangar" to a suitable
airstrip, I use a 5 x 8 wire mesh floor utility trailer, two 5 ft 2 x 6
planks for ramps, four friction-type clamp tie-down straps with hooks at
each end to secure the axle to the front and rear of the trailer, and 2
rachet-type tie-down straps, one through the engine mount, the other at
the rear just before the sub-fin. Nylon ropes bundle the ribs together and
the wing struts are tied down to the floor of the trailer. The prop is kept
from windmilling with another length of rope. The rudder and stabilizer
are removed and placed on the floor of the trailer when going over 55 mph
(if you have one of these expanded wire floor trailers, lay down
some carpet first so your sails don't get chewed up!). |
Transportation and
Storage |
| Here's a time lapse view of my wings being folded up
for transport. Even though the plane was never designed to do this as
a feature, no modifications were required for it to be done, except for
the addition of milk-jug plastic washers under each LE root bracket so
they could smoothly rotate without grinding against the engine mount. BJ7 has been and is currently being stored in my two-car garage just 2 miles away from the airport, many times trailer and all.
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