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 Blue
Jay 7 is a highly modified Weedhopper
USA, Inc Super Single model ultralight aircraft. A Super Single
is a 2-place airframe delivered with only one seat. The 2-place air
frame has been replaced, except for the boom, with Model 40 style fuselage
tubes.
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.
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 are reinforced with sleeves of tubing
on the outside. Everything is held together with 1/4" and 5/16"
military-grade (AN) aircraft hardware (bolts, nuts, washers, clevis
pins).
 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!!
Other than the obvious color
order and scheme that mimic the tail feathers of a Blue Jay bird, I have
a personal anagram for my "BJ7" call sign. Being a Christian,
B = "Because," J = "Jesus," and
7 is the number of perfection.
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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. The Ultralight Store (Winchester, California) made the new, blue jay colored sail set in February,
2002, with a custom cutout in the wing for the engine at no extra charge! |
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A heavy-duty, lightweight
motor mount is custom made from various T6 6061 aluminum stocks with Barry
rubber 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 'clmapshell' chokes here and several other places to reduce RFI. 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. |
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Blue Jay 7 has a fiberglass faring and plastic seat tank originally made
for the Phantom ultralight and a homemade 3/16" Lexan polycarbonate windshield. |
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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 on a RAM mount, altimeter,
dual CHT gage,
90 degree sweep 0 - 8000 rpm tachometer, dual EGT gage, 0 - 80 mph airspeed indicator, and an Icom A4 radio also on a RAM mount. On the bottom left to right are: ignition kill switches, starter switch, carburetor primer, strobes and landing lights switches, and a coaxial jack to power the radio.
A Power Sonic, 12 volt, 18 amp sealed lead-acid battery is strapped to the floor of the pod and to its left, strapped to the seat tube is a cigarette-lighter jack to power the GPS. |
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Modifying the factory nose wheel steering
to fit the pod was simple. A 6" extension, made from four pieces
of 3/16" x 1.5" aluminum bar stock, brings the cross bar foot
steering tube up inside the faring. Two bars are used on each side to
sandwich the nose fork at the bottom and spacers at the top with the cross
tube mounted to the top front of the assembly. |
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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."
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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 are spot welded 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). |
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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. See the menu link 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, damaging and shredding the Dacron sail cloth, so I added this litle caster wheel. |
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The airspeed indicator gage in the instrument panel uses these two tubes to measure the pressure difference between air ramming into the larger one and flowing past the upper one. The upper tube is called the Static tube. Its open end is plugged, but its sides have a couple tiny holes drilled in it. This measures the ambient air pressure (air flowing past the holes does not create any pressure or vacuum). The lower tube is called the Pitot (pee - toe) tube. Air rams into its open end creating pressure because its other end is connected to the gage and prevents air from flowing through the tube. The difference in pressures is directly proportional to your speed through the air. |
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The whole assembly is mounted to the bottom of the left wing with a wing nut, making for easy removal when folding up the wings... it simply lays in the sails as they are wrapped around the wing spar tubes.
The position of the little black disc on the static tube is used to correct differences in the system that cause an inaccurate reading. |
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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 simply two 1" wide straps of aluminum, one at each end of a 1" OD tube riveted to the flap. 1" ID PVC pipe fittings are used as bushings. The assembly is bolted to the trailing edge of the elevator with 10-40 machine screws. |
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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. By varying the position of the 'L' bracket with its cable adjuster, tune the base amount of tension needed to keep a plane in hands-off trim condition at a minimum cruise engine power can be finely tuned and then by adjusting the trim lever the spring tension is increased to trim for different engine powers. |
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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!!!). |
