|A highly engineered VARIEZE|
|December 2004 EZ of the Month|
text by Steve Franseen
Steve Franseen has kindly allowed ez.org to publish this document that describes the finer points of his very fine Varieze, N86EZ that he built in the eighties. The text that follows describes many of the unique features of his EZ. You can literally see the thousands of hours that it took to finish N86EZ. Steve no longer owns N86EZ but it's fine craftsmanship will be around for many years to come.
This plans-built homebuilt project began with the purchase of a project in 1981 from the estate of Mr. Bill Crinich, an IBM engineer, Niwot Colorado. Wings, center section spar, canard / ailerons and unattached winglets and various parts, including nose gear casting, nose strut, landing gear core, and a O-SMOH Continental C-85-12F engine (later sold) were included with project.
The builder, Steve Franseen was an Industrial Designer and Mechanical Engineer and during the years of construction and completion of this project, (Dec. 1981 through Nov. 1987) Steve was employed by a Denver-based international dental manufacturing Company. At that time he was (and remain) heavily involved in 3D Computer Aided Design, (CAD). The availability of 3D CAD modeling and in a few cases CAM played a significant role in some of present unique shape and sweep of the plane as well as hundreds of parts and system components. CAD was used for the design of many of the systems, non-flying surface templates and mechanisms.
Steve served as Manager of Engineering and in the course of that he became good friends with senior tool and die makers, some of which took a participative interest in the construction of 86EZ. One machinist in particular, a Mr. Glenn Clark (now retired) machined many of the components, small parts and assemblies of the plane in his well-equipped home based machine shop over those years, in accordance with my engineering drawings.
As will be appreciated from the descriptions to follow, the building of this aircraft was undertaken with emphasis on accurate metallurgy, materials, and precision. Access to CNC machining, heat-treating and normalizing facilities, metal finishing, tumbling and deburring, heavy machine tools, CAD, and industrial inspection tools all contributed to the excellent, highly engineered airplane that has resulted. This airplane was built with the attitude that with care, attention to fine detail, and comprehensive maintenance, there is no reason that the basic airframe of 86EZ should not be flying many decades into the future, just like the Bonanzas and Cessna 140s manufactured 55 or 60 years ago are still flying.
One other major influence on the design of 86EZ was from 2 close friends, Mike Guthrie and Ben Duarte, who had both guilt very fine Vari Ezes. Both engineers had many hundreds of hours on their planes as the completion of 86EZ was undertaken. They flew their planes very aggressively and had many many pieces of practical real world advice related to the operations of their aircraft that were incorporated into the overall approach to 86EZ.
General Philosophy of design and construction: Rather than build a highly modified racer, with "passing fad" - type features, the approach taken with 86EZ was to avoid anything that reduced dependability, safety and access for maintenance and inspection. As an example of this, forged Venolia automotive racing pistons and cylinder-saving Total Seal™ rings are used, but not as it is normally done: A special set of pistons was ordered that produce a compression ratio of only 8 : 1, (7 : 1 is standard for the Continental O-200) This avoided the intensity of the all too typical 9.5:1 compression ratio used with the O-200 by many for racing. 9.5 : 1 is hard on Continental cylinders designed in the 40s.
In some ways 86EZ is "plain vanilla and by the plans" but in many other ways it is not. Many decisions were made during the construction of this aircraft that were based on safety, durability, dependability, precision, accessibility for maintenance, corrosion resistance, modifications for improved wear and lubrication, low hysterisis of the controls, long range and comfort for pilot and passenger. Because of this effort, non-stop flights such as from Denver to Chicago Meigs, and San Diego to Denver are easily accomplished, typical missions flown in 86EZ. It is an experimental airplane that you can relax in, even coming in to Denver over the Rockies non-stop from the West coast. The airframe has proven to be virtually trouble and annoyance free for 1200+ hrs.
1.) Extended nose: The nose has been extended 7" further forward than plans. This gives the plane a "Long look" and avoids the somewhat short blunted appearance of the noses of some VEs. Extending the nose required photographic enlargement of the forward-most bulkhead (forward of the battery) and several other changes that allowed aft geometry to fair in. Bulkhead F-22 was not changed. The nose extension was not a mere matter of microing on a few additional blocks of foam, and in fact impacted the fairing of the outer top sides and belly skins back to the forward canopy area. Many favorable comments have been received regarding the contouring of the forward fuselage area. Through extending the nose, slightly less epoxy / lead shot ballast was required forward of the forward-most bulkhead for CG purposes: only 6 pounds. With the nose gear extended, the airplane will comfortably stand on all 3 wheels, with about 8 pounds on the nose wheel. There is little worry of it flipping over backwards as with some EZs.
A sealed "Harley" battery is currently installed. The battery, as well as the entire nose rudder pedal area is accessible through a separate removable hatch of maximum permissible size allowing the forward area to accessed for rudder pedal and elevator control inspection, battery maintenance and so on without having to remove the canard. Canard attach bolts are oriented facing forward instead of aft and are accessed through this nose cover hatch.
3.) Nose skid: The nose skid is mounted on a .125", polished 316 stainless plate that is held in place by the 2 upper bolts of the nose strut pivot casting. It extends down the strut about 6 inches but is formed to stand clear of the epoxy / glass gear leg. A lower tab of this plate is bonded to the nose strut with flox and wrapped with Kevlar roving. Two approx. 4-inch-long hardened D-2 tool steel "Ls" capture a hard durometer rectangular strip of ½ inch thick rubber, which is the high-friction, ground-contacting point. The tool steel parts are chrome-plated for corrosion resistance and thermally isolated from the stainless plate through fiberfax ceramic felt. The design intent is this: as with similar aviation axioms: all EZ pilots fall into 2 groups: those that have landed with the nose gear up, and those that will. Typically, the real damage from such events results from intense heat soak into the structure during nose gear-up landing rollout. If such a landing happens, the hard tool-steel skids will take the loads without annealing and being ground away. The ceramic paper and the air gap between the plate and leg will greatly reduce any destructive heat flow into the composite structure.
The hard rubber skid provides a soft dampening when setting the nose down, and good friction. During start-up with the nose down, the plane will not start creeping forward until the throttle is advanced past about 1/3 power.
4.) Shimmy dampener and nose wheel pant, and nose wheel bearings: An early Rutan Newsletter "Mandatory Ground" required that the .093-wall 4130 tubing pressed into the cast aluminum nose wheel fork casting be replaced with .125 (min.) wall tubing because some early problems of explosively divergent nose wheel shimmy were encountered by some when the .093" tubing bent slightly. Slight bending negated the original, per plans shimmy dampening system. To solve all of this, a slightly longer .125 wall 4130N tube was pressed into the nose fork casting. A steel part was turned that cross-bolts into the top of the .125" tube. It has a round land and an upwardly extending stud. The stud passes through and captures a horizontally positioned canvas phenolic tongue attached via a small aluminum flange to the lower gear leg. The flange is held in place via flox /Kevlar roving. The stud accepts a short alternatingly stacked set of stainless Bellville (cupped) washers that are compressed by an MS21042-4 nut on the stud. The stack of Bellville washers creates a compressive load on the phenolic tongue and thus a smooth but positive rotational friction. Not only has this unique approach to a nose wheel shimmy dampener worked perfectly, it has required no adjustment or maintenance whatsoever to maintain the required 3 to 4 pound side load pressure test to caster the nose wheel.
By closing off the top of the tube as described above, it then made it possible to similarly seal the bottom of the tube and install a grease zert to pressurize the tube ID with grease. With a small hole drilled through the tube at a level corresponding to the gap between the top and bottom bushings pressed into the nose fork casting, a grease gun is pumped until a little grease is extruded from the bushings. Such means of grease lubrication has resulted in no evident play or wear in the nose fork pivot bushings for 1200+ hours of operation.
A tightly fitting wheel pant fender, formed from buck-riveted 2024 T351 sheet is attached through the axle bolts, and attached to the top of the fork casting via a 4130 flange. A 4130 strap runs from the axle bolt, around the bottom of the fender to take all of the abuse and various stresses such a wheel pant encounters in operation. The wheel pant has not deteriorated in any way. Its function is to greatly reduce fine gravel abrasion to the prop on take-off. The wheel pant is zinc chromated and white enameled. As for all such assemblies throughout the AC, the original CAD-produced templates and CAD drawings exist if the fender ever needs to be repaired or replaced. All 4130 parts associated with the nose wheel fender were chrome plated for ultimate corrosion resistance, hydrogen embitterment having been considered but deemed (and proven over time) to not be a factor.
Another problem encountered by a few early VE builders was that when the nose wheel axle bolt is tightened enough to properly adjust the tapered nose wheel bearings, the aluminum bearing bosses riding on that axle bolt would tend to turn on that bolt rather than the bearings turning in the wheel. To correct this on 86EZ, 2 small aluminum spacers are located on the axle bolt, inside the wheel, centered between the 2 bearings. The spacers are machined slightly under-length and final bearing in-out tightness was set by trial assembly and re-assembly, placing gauge shims between the spacers. Once set, this allows the main nose wheel axle bolt to be tightened to full, normal torque specification without effecting bearing tightness. This holds everything nicely together in compression, and the wheel turns only on the bearings, not the axle bolt. To accomplish this condition, the inward-facing surfaces of the fork around the axle bolt holes were precisely spot-faced to hold the bearing bosses true. In general, the entire lower end of the nose strut is more highly developed than the rather simple approaches described in the plans.
5.) Nose wheel blister. The standard nose wheel blister has been modified so that instead of being generally bulbous in shape, it has a flattened top surface. This allows that top surface to better serve for mounting equipment, and such. Currently, the cabin lighting dimmer / power supply is mounted there and in the past, a quartz / infrared electric cabin heat unit has been mounted in this location. The electric cabin heater was subsequently removed and sold, but it works well when the 60-amp Cessna alternator (included) is installed. The ragged current surge as it cycled on and off however eventually damaged the Terra electronic course deviation (ECDI) indicator display and the heater surges were hard on the electronics in general. The blower motor was unshielded, which created RF noise through the radio and noise through the electrical system. A surge suppressor / capacitor and a shielding of certain components of the heater could have solved those problems, and a similar infrared quartz heater could be installed. In any event, there are dedicated high-current circuit breaker-controlled terminals rated at 40 amps on top of the nose wheel blister, and mounting hard points for an infra-red heater, should an electrically shielded and surge protected quartz heater be installed in the future.
6.) Nose retract: the torque tube going from the retract crank handle to the nose retract worm gear incorporates 2 small, machined aluminum faces with a milled annular groove. If the 2, #6 screws are loosened, it allows the crank to be "clocked" so that it is always at the six 0-clock position when full up or full down. This is to accommodate normal wear of the thrust bushings in the worm gear and keep the crank symmetrical with the panel and out of the way. The shaft passes through the instrument panel in a self-lubricating molybdenum disulphide reinforced nylon bushing, rather than the little green polyethylene standard bushing. Aft of that, the handle itself is bolted to a small precision-machined 2024 T351 aluminum part that functions as a miniature disk brake. A small, second knob locks or unlocks the disk with thumb and forefinger turning. This allows easy and very positive, one-handed unlocking, cranking, and relocking of the nose gear. It will not slip and allow the nose gear to hang out a few inches in flight or slip and hang down in the hangar when being moved. A machined aluminum knob with 2 sets of pressed-in sealed ball bearings in the main cranking knob all combine for a very trouble-free, smooth, light and functional nose gear cranking mechanism.
7.) Roll Trim: The plane has an excellent electric servo roll trim but it is augmented by a "bungee" type roll trim located at the forward end of the main control system torque tube. It is another small precision-machined mechanism with a sealed ball bearing. It is located under the top surface of the right console just aft of the instrument panel. It is based on a very stiff press-tool-quality tension spring about 2" in length. A small knob passes up through the right console that adjusts the "center" of the bungee force. It is not meant to be a fine-tuning roll trim that would be adjusted frequently in flight. Instead, it provides a moderate stick centering force. The effect of this is to provide a desirable general centering force on the stick in roll that definitely crates a slightly more solid feel to the stick, more in harmony with the pitch. In actuality, once the neutral center point is set, it is almost never changed.
The electric trim is based on a retract servo used in RC model planes. Retract servos are used to retract landing gears on large RC models and thus have one additional level of reduction gearing. Compared to the fast-acting servos, they move much slower, and generate much higher torque. The servo tab on the right wing is activated by such a servo, which in turn is activated by a small centering momentary contact rocker switch just forward of the control stick. All I can say is that it works just right with more authority than is ever needed, and due to its slow response, it can be fine-tuned to hold the nose absolutely still in heading. I will crank it to one extreme to do a roll in that direction, but otherwise it stays within a few degrees of roll neutral in level flight.
8. Consoles and console-mounted controls: According to Burt Rutan, the cockpit consoles are structural and contribute to the stiffness of the fuselage. Once glassed in, they unfortunately make it impossible to access many flight-critical mechanisms such as the control system on the right side and the belly board (air brake) actuation and pitch trim assemblies on the left. To counter that problem, removable access panels are installed.
The belly board pulley, cables and actuator pivot gave a lot of builders problems, and many of the belly boards actuators suffered from alignment problems and they cables could not be kept straight and very tight. To solve this, an aluminum hard point was installed on the console to handle the surprisingly high forces generated when extending the airbrake. Also, small turnbuckles were installed in the actuator cables so their tension could be adjusted, which also allows desirable, exact positioning of the belly board airbrake handle when the airbrake is in the closed position.
9. Instrument panel: The canopy latch, according to plans, extends perpendicularly aft from the instrument panel. By angling the canopy latch downward from a higher attach point on the panel; it was possible to place six, 3 1/8" instruments across the width of the panel. (The radios are 3 1/8 "wide) Below is a picture of the panel. Below that is a description of the instruments.
At the lowest right corner of the panel, partially hidden by the stick is a 2 ¼" recording G-meter.
Directly above that is a dual gauge. It was a combination that never had been ordered before at that time. The manufacturer made new art to silk-screen the bezel; it is a combination system voltage / carburetor air temp. gauge. The quad gauge above that registers cylinder head temp., exhaust gas temp., oil temp. and oil pressure. The oil pressure section of the quad gauge is de-activated in favor of the larger red LED oil pressure gauge to the left of the magneto switch.
Below and to the left of the quad gauge is a red push button switch. It is an aux. "push to transmit" button in the event that the PTT on the control stick fails.
Below the oil pressure LED gauge is a liquid quartz tachometer display. The exact revs are displayed for 1 second, to be replaced with the exact average revs for the next second and so on. This tachometer requires no system voltage and operates from an eddy current produced by a proximity sensor mounted near the prop. Flange. This tachometer works exceedingly well, and is particularly well suited for leaning at high altitude.
Below the tachometer is the Terra 720 channel single nav/com stack. Directly to the left of the radios is the VSI, which indicates to 3000 feet per minute rather than 2000 or 6000. Directly above the VSI is the airspeed indicator, which has green, yellow, and VNE ranges etc. set for this AC. To the left of the airspeed is an electric turn and bank.
Below that is the electronic course deviation indicator, (ECDI), which displays the output of the nav radio. It uses a gas-discharge display and has a few additional features beyond a standard swinging needle VOR head. The brightness of the display is automatically controlled by a photocell and automatically adjusts itself to the ambient lighting conditions of the cockpit.
To the left of the ECDI is an Edo-Air transponder. It is the aux. transponder from a Lear Jet, and is TSOd to squawk to the radio-horizon at 49,000 feet. It is 300 watts whereas most light aircraft transponders are 100 or 150 watts. It is connected to an encoder mounted forward.
Above the transponder are 3 phone jacks. The lower 2 are for the headset when not plugged into the intercom. The top jack is audio output from the radio so a small speaker can be plugged in to listen to ATIS or traffic during pre-flight.
Directly left of the 3 jacks is a clock. Below the clock are 3 lights. The left light is steady red and lights when oil pressure drops below 12 pounds. When it comes on, the Hobbs meter goes off. It is activated by a pressure switch located just forward of the firewall. That pressure switch is mounted on an aluminum manifold that also includes the oil pressure sender.
The center light glows steady red and indicates when the warning system is defeated. It will light when the warning horn is defeated and is connected to a relay that enables the warning system to reset itself each time an abnormal flight configuration exists. For example, the horn sounds if the throttle is advanced without the canopy being locked or if the throttle is closed and the nose gear is not down and over center-locked. The right light is yellow and flashes when the fuel transfer switch is on. If you will notice above the 3 jacks there is a switch. It turns off all 3 lights off should any of them light up at night interrupting night vision. The altimeter is at the far left of the panel.
Above the altimeter is the canopy latch bracket. Incorporated within that latch bracket is for / aft adjustment to set the tightness of the 3 canopy latches. Above that is a switch that switches the transponder from mode A to Mode C operation.
Only partially visible in the photo above is the nose gear retract crank. Behind and below it (not shown) is a small, angled sub-panel. It contains the ammeter, master switches, main circuit breaker, and a heavy lighted switch for the electric cabin heater (no electric heat is currently installed).
The panel has one additional ply of BID glass on its aft face for additional stiffness.
The radios and the several other critical instruments are internally lighted for night flight. There are also gimballing black-lites mounted on the underside of the canopy that shine down on the unlit instruments. Eyebrow lights light critical flight instruments, and the whole cockpit can be flooded with a map light mounted on the right side of the roll over structure, near the top.
On the right cockpit wall is mounted the switch / fuse panel. Forward of the stick is white OAT gauge. It is an industrial gauge that is accurate, and reads from an alcohol bulb mounted just forward of the nose gear pivot.
The compass is mounted further rearward on the upper right side of the cockpit. The compass is internally lighted and the compass box contains a switch controlling the gimballing black lights that shine down on the instrument panel from the underside of the canopy.
The electrical system has never blown a fuse of tripped a circuit breaker.
10. Rear seat: The center of the floor in the rear seat has non-slip hard point for stepping into the rear seat. There is a gimballing vent on the left. A footrest holds the passengers ankles / feet in a comfortable position. The geometry of the rear seat has been modified to a slightly more upright position by a spacer behind the seat. A guard keeps the passengers right leg from coming into contact with the control tubes. Passengers have commented on the fact that they have not been uncomfortable, even on long flights, and have been able to read and sleep etc. with no problems or complaints.
11. Engine mount extrusions: Per plans engine mount fittings call for 1 inch by 1 inch angle aluminum bolted and bonded to the top and bottom of the center section spar. 1 inch by 1 ½ fittings were instead machined from 2024 T351 aluminum for 86EZ. The wider mounting surfaces that bond to the spar and longerons were vapor blasted for maximum flow adhesion. The forward end of the upper fittings are extended forward of the spar providing a mounting hard point. Corresponding hard points on either side of the rollover structure provide mounting points for installation of a long-range fuel tank in the passenger compartment. Electrical connections are provided for an electric fuel transfer pump. A second fuel tank vent (for such a long-range tank is installed on top of the aux. Fuel tank.
Above: a. special 1 by 1.5 extrusions
12. Brakes: Rosenhan (now Matco) brakes are used. Heat shields are installed to keep heat from the disk from radiating to the gear leg, brake line and brake puck. Axles have been machined with a 3/8" mounting flange and a fillet as the axle diameter transitions from 1-inch diameter to the mounting flange. The original Brock axles have a ¼" flange and no fillet, and several have reportedly broken. The axle is thermally isolated from the gear leg via the use of fiberfax ceramic felt.
Above: a. heat shield
13. Under the cowling: Generally, the engine compartment stays very clean due to the absence of oil from the engine leaking and blowing. The mating surfaces of the crank case were lapped true and flat prior to assembling the engine, and all mating surfaces of engine components and accessory case were likewise trued, degreased deburred and sealed prior to assembly with emphasis on no leaks and an oil tight seal at all points. Due to these efforts, the engine leaks very little oil, and the entire engine compartment stays clean.
14.) Carb heat box: The carburetor heat box is based on 4 type 321 stainless tangs tig-welded to the 321 stainless exhaust pipe on the left side. Thin 316 stainless ends of the box are bolted to the tangs with #4 stainless fasteners and an aluminum box spans the ends, bolted with a series of tiny #2 bolts and MS21042 jet engine nuts. Inside the box is an .050" dia. 17-4 PH stainless spring that has been precipitation hardened for toughness (to avoid heat embrittlement and work hardening). The spring is wrapped around the "wishbone" area of the exhaust pipe for maximum heat transfer to the induction air. The carburetor temp gauge typically shows an 8 degree centigrade increase when full carb. heat is applied. On the "hot" end of both the right and left exhaust pipes, special ¼ 302 /304 stainless exhaust flanges were machined replacing the standard 3/16 flanges. The original flanges tended to warp slightly at the exhaust ports, which permitted some leakage of exhaust gasses around the exhaust gaskets.
15.) Carb, Throttle, mixture linkages: The carburetor was completely overhauled according to Marvel Schebler manual procedures, including throttle shaft, butterfly and shaft bushings, jets and virtually all moving parts. The Marvel Shebler manual is included with the sale of this project. The mixture valve was electro polished for a micro-smooth surface allowing smooth rotation at the bottom of the bowl. All bolts are safety wired. A carburetor air-temp. thermocouple was mounted in the carb. All linkages and cables connecting to the carburetor are precisely aligned, and mounted rigidly on .060 plate aluminum. Return springs likewise are adjusted for adequate tension without overload. All movements were studied and very carefully set up for very smooth and friction free, full range operation. Many accidents have been caused by lack of careful, anticipatory attention to this area. The throttle return springs are redundant and are connected to a thick chromoly tang mounted to the vacuum pump pad. (All carb. linkage return springs need to be examined under magnification at annual inspection to assess wear at their ends due to unavoidable harmonic vibration).
(also note silicone RTV rubber between 2 throttle springs to dampen vibration).
The tachometer proximity sensor sender is mounted on the case centerline via. Custom machined .125" 2024-T351 aluminum flanges. It reads a 60-tooth electro less nickel-plated chrome moly timing wheel mounted between the prop flange and the 5-inch prop extension.
18.) Crankcase ventilation: The crankcase ventilation fitting passes through the accessory case cover. On the inner surface of the cover, a heli arc-welded aluminum baffle shields the vent orifice. The baffle is oriented to shield the orifice from oil splash from the direction of rotation of the timing gears. This greatly reduces the volume of oil mist carried out of the crankcase with crankcase gases.
Based on reports of needle bearings getting loose inside engine without a starter, the needle bearings that support the conventional starter gear inside the accessory case have been removed at assembly of case.
19.) Oil separator and Motor Mount: The oil separator has been opened and 2 "Brillo" pads have been inserted to increase oil condensation. The oil separator is thermally insulated from the firewall with ceramic paper to reduce any potential for heat-soak into firewall structure and into glass of reserve (header) fuel tank.
The bolting of the motor mount to the mounting extrusions is reinforced by chromoly slugs turned and drilled to fit on the inside of the 4 open forward stubs of the motor mount. These allow the 8 AN-4 bolts attaching the engine mount to the airplane to be torqued to full torque without ovalizing or distorting the stubs of the motor mount. Before the motor mount was mounted to the airplane, it was magnafluxed by Aeroprop at Jefferson county airport Denver and it has been completely sloshed with linseed oil.
20.) Belly compartment: Forward of the firewall is a compartment accessible through a cover between gear legs. It contains many components away from the heat and exposure of the engine compartment. Shown below are the fuel filter, pressure switch for the Hobbs / oil pressure warning light, and the Piper fuel valve that replaced the original brass fuel valve.