CONTACT! Magazine Issue 97 Thatcher CX4

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Nov - July 2009

Issue #97 CONTACT! ISSUE 97 PAGE 1

PO BOX 1382 Hanford CA 93232-1382 United States of America 559-584-3306

Volume 17 Number 2 November 2008 —July 2009

Issue #97 MISSION CONTACT! Magazine is published bi-monthly by Aeronautics Education Enterprises (AEE), established in 1990 as a nonprofit corporation, to promote aeronautical education. CONTACT! promotes the experimental development, expansion and exchange of aeronautical concepts, information, and experience. In this corporate age of task specialization many individuals have chosen to seek fresh, unencumbered avenues in the pursuit of improvements in aircraft and powerplants. In so doing, they have revitalized the progress of aeronautical design, particularly in the general aviation area. Flight efficiency improvements, in terms of operating costs as well as airframe drag, have come from these efforts. We fully expect that such individual efforts will continue and that they will provide additional incentives for the advancement of aeronautics. EDITORIAL POLICY CONTACT! pages are open to the publication of these individual efforts. Views expressed are exclusively those of the individual authors. Experimenters are encouraged to submit articles and photos of their work. Materials submitted to CONTACT! are welcomed and will become the property of AEE/CONTACT! unless other arrangements are made. Every effort will be made to balance articles reporting on commercial developments. Commercial advertising is not accepted. All rights with respect to reproduction, are reserved. Nothing whole or in part may be reproduced without the permission of the publisher. SUBSCRIPTIONS Six issue subscription in U.S. funds is $25.00 for USA, $35.00 for Canada and Mexico, $47.00 for overseas air orders. CONTACT! is mailed to U.S. addresses at nonprofit organization rates mid January, March, May, July, September and November. Please allow time for processing and delivery of first issue from time of order. ADDRESS CHANGES / RENEWALS The last line of your label contains the number of your last issue. Please check label for correctness. This magazine does not forward. Please notify us of your date of address change consistent with our bimonthly mailing dates to avoid missing any issues. COPYRIGHT 2009 BY AEE, Inc.

In the immortal words of Ricky Ricardo, I have “...some 'splainin to do!” This issue is at least six months past due– at least it’s been six months since the previous magazine was mailed. Without going into gory detail, the short answer is that the economy is to blame– not directly however, since the magazine itself is doing rather well. It’s my personal drafting business (home design) My son Antonio assisted me this year at that’s taken the hit and has Sun ‘n Fun, same as last year. caused me to in essence, go back to work. I’ve certainly taken advantage of the past decade’s housing boom to grow my business to the point where I had multiple employees working for me, and with the help of my son, I’ve been virtually retired for the past several years and had all sorts of unpaid volunteer time to dedicate to the publication of CONTACT! Magazine. But with the collapse of the custom home market here in California, I’ve had to lay everyone off and tend to what little business I have, myself. Continued on page 26


Sadler Vampire Update.— A brief update from the people at Sadler Aircraft. We’ll have more on them after OSH– the promised Part Two.


William Stinson’s Thatcher CX4.— Pat Panzera introduces the CX4 to CONTACT! readers in this article which will certainly not be the last we hear from Thatcher.


Power and Torque.— Jack Kane offers a simple explanation that horsepower and torque are not mutually exclusive. Far too many people are under the wrong impression and we hope this fixes it.

10 Brake Mean Effective Pressure (BMEP) — Jack Kane, who will become a regular contributor, shows a simple way to help separate the wheat from the chaff when it comes to engine manufactures’ claims regarding power.. 12 Angle of Attack.— A how-to on building a simple device that can help reduce the risk of inadvertent stall. 18 A Vibration Study of the Maxwell Propulsion MX1 Subaru Conversion Package.— Gwen Maxwell chronicles the work MPS has done to reduce the effects of torsional vibration using info found in issue #90 of CONTACT! Magazine. 22 My First Alternative Engine Round-Up.— Gwen Maxwell reports on her experience attending CONTACT! Magazine's annual fly-in event. 28 Geared Drives checks in. — Phyllis Ridings brings us up to speed with the latest developments with their Subaru PSRU and their RV-10 firewall forward package based on the Chevy LS series of engines On the cover: David Thatcher, designer of the Thatcher CX4, pilots serial number one over Lake Hancock, FL during Sun 'n Fun 2008 while EAA Chief Photographer Jim Koepnick squeezes the shutter. Photo plane pilot: Bruce Moore. Thanks go to the EAA for allowing us to use this photo.


By Pat Panzera Although the road has been a long one and seemingly riddled with setbacks, Sadler Aircraft Company (Roseburg Oregon) is reporting that their 2-seat LSA, the Vampire, (as reported on in CONTACT! No. 96) should complete the ASTM certification process to qualify as a factory-built S-LSA by the end of August.

These photographs were shot almost six months before being published. We had hoped to have newer photos by now, but these will have to do. After OSH we’ll have a more up-to-date Part 2 feature article, as promised in issue #96.

“Our current prototype is registered as Factory Experiment R and D [research and development] Aircraft” said company Vice President David Littlejohn. “We’ve been working hard on several refinements over our first prototype, most of which were under development long before the loss of our original prototype. We’ve kept the overall cabin width of 50 inches, but there are a lot of subtle changes that pilots should really appreciate.” When asked about the changes, Littlejohn provided CONTACT! Magazine with a laundry-list of items. “We’re waiting until Oshkosh to make most of the announcements. but we appreciate the work CONTACT! does so we are glad to give you and your readers the scoop.” The most noteworthy change in the Vampire is the powerplant. The first generation prototype toyed with an experimental rotary engine that had not yet received ASTM approval for light sport use. (See CONTACT! Magazine, issue #93) When ASTM approval became a problem, Sadler Aircraft looked to both Rotax and Jabiru and in the end, the 120 HP Jabiru 3300 was selected for its higher RPM and simplified cooling systems. In addition to the new engine, the Vampire now sports a split windscreen with large, wide gull-wing doors. The fuselage has also been lowered by four inches, making ingress and egress a breeze. The main gear stance has been broadened by four inches to increase ground stability, and the nose wheel is being moved forward for the same reason. The new pod design accommodates two overnight bags in the nose section.

Both for appearances and a bit of drag reduction, the hinges on the folding wings have been hidden or minimized. There are now a total of three bolts per wing that need to be removed to accomplish the wing fold. Remarkably, the fold can be accomplished by a single person in under two minutes per side.

In addition to the hidden hinges, the wings now also sport Fowler flaps and downward-curved wing tips with integrated LED position and navigation lights – standard with every Vampire. “We’re very excited about the finished product. We wanted to bring a plane to market for under $100,000 that wouldn’t nickel-dime Continued on page 17


Story and photos by Patrick Panzera William Stinson 8550-L Scenic Highway Pensacola, FL 32514 850-471-0123

We caught up with Bill Stinson and David Thatcher at OSH 2008. They were parked in what I consider to be a place of honor, just outside the Homebuilders Headquarters.

Bill’s first attempt at an amateur-built experimental aircraft is certainly a winner. The single seat, all aluminum, semi monocoque construction beauty is powered by a 1915 cc Great Plains Aircraft Supply (GPAS) Volkswagen conversion, reported to make 69 HP max, 65 HP continuous. The first time Bill laid eyes on a CX4, the plane was spotted on the ramp during EAA Chapter 485’s pancake breakfast at Ferguson Field in Pensacola, FL, the very airport where Bill took his first flight. David Thatcher (the designer, builder and pilot of this plane) was standing beside his prototype and was approached by Bill who began to converse with him, not realizing he was the designer. David proceeded to tell Bill that he had plans to develop a builder’s manual and a set of aircraft construction documents for a scratch-built version. Bill didn’t think much more about it until he went to Sun ‘n Fun the next year and saw the airplane there again. Bill sat in it, fell in love with it and made the decision to try his hand at manufacturing an experimental aircraft. Bill Stinson’s flying adventures started back when he was nine years old. A co-worker of his father’s took him for a ride in a Cessna 150. That was of course during the days before Young Eagles (YE) and in a sense, it was a YE flight– having the same impact on young Bill that we YE pilots hope to impart to each child we introduce to flight– one that will last their lifetime.

At Auburn University Bill studied aviation management and ended up administering air medical helicopter programs for the next 15 years. Bill earned his wings and has owned aircraft in the past, but always wanted to build and fly his own. Like many of us, he built his share of model aircraft and worked some with his hands completing honey-dos but had no formal training in metalworking, Mr. Thatcher encouraged him with his creation since his design goal is to allow the builder to complete his project primarily solo, in a two-car garage and in less than a 1,000 hours. With that, and with the construction estimate in the $15,000 range, ($13,500 advertised) Bill decided to take it on as a personal project. It was also very comforting for him to know that he lived in the same city as the designer and that if he had any technical questions, answers were a local phone call away. As it was, Mr. Thatcher would stop by occasionally to check on Bill’s progress. As things normally go, Bill exceeded his $15,000 budget by a little. He opted to have his GPAS engine kit professionally built and test-run by GPAS and he also selected some instrumentation that was a little bit more expensive than he originally planned. Selecting the UMA micro gauges, which are substantially smaller than traditional steam-gauges, thus allowing for more instruments in the same size panel while still retaining that classic steam gauge look. That look is part of Bill’s personal preference for a “little personal make-believe fighter.” Along with going over budget a bit, Bill also missed the mark by exceeding the advertised 850 hours build time by about 100. Not too bad all in all.


GETTING STARTED Beginning with the construction of the center section spar, virtually everything else goes from there. Once the center spar is built and jigged on the bench, the wing panel spars are set for the proper dihedral. Once the assembly is completed, the builder can either set the wing spars aside and attach ribs and skin later to concentrate on the center section, fuselage and empennage, or he can work on the wings first.

knowledge that was imparted to me by David Thatcher, and the friendship that developed over time. Dave is a 77 year old gentleman who was an airplane and power plant mechanic (A&P) and IA all of his life and always wanted to design and build his airplane because he could never afford to buy one. He’s just a genius when it comes to a simple design that was easy for me to put together and certainly his help was invaluable.” Not everyone will have the access to Dave that Bill has enjoyed, due simply to location. However, I’ve been monitoring the CX4 internet builders group for quite some time now, and from Dave’s active roll in the group, I have come to know and respect him through the process. Although I don’t have any immediate plans to build a CX4 myself (although I’d LOVE to), I’m confident that I would develop a lasting relationship with Dave through the process, just as Bill has.


Construction photos by Wilson Leonard

Spar construction can be intimidating but the plans and construction manual are detailed enough to give confidence to even the novice builder. Bill chose to complete his wings first and get them out of the way before turning his attention to the center section, working toward getting it on its gear. “Once the airplane’s on the landing gear it goes fairly quickly after that.” Bill went on to tell us, “It’s just an enjoyable project and of course I started it because I wanted my own personal airplane, one that I built myself. But I tell ya, the thing that is probably the most rewarding for me is not the bright shiny airplane sitting here in front of us; it was the

There are some components that are available that Thatcher produces and offers to those who purchase a planset. Among these parts are the upper and lower fiberglass cowl halves, the acrylic canopy, and the fiberglass wing and elevator tips. Available from approved vendors are preformed ribs and bulkheads; complete wing and center section spars; aileron sub assembly, quick-build fuselage (includes spars); quick build wings with ailerons, and the engine mount. But it’s not critical that any of these parts be purchased– the builder is free to build them, the plans show how it's done. Details are also provided on fabricating the cowl but for some it may not be as cost-effective as purchasing one pre-made.

WINGS The spar as shown in the photo above is constructed using squeeze rivets (conventional), but that’s about the only place where Avex pull rivets are not used. The plans call for either counter-sunk or dimpled construction (in conjunction with T-88 structural adhesive), but the builder can choose to follow the “Chris Heintz” method of concaving the nose of the rivet puller’s mandrel, folding over the head of the rivet to form a low-profile dome pull rivet.


With three of the primary “performance” instruments at 3-1/8”, there was room for eight more 1-1/4” UMA gauges. On the left side are: Tachometer; manifold pressure; CHT and Volts. On the right are oil pressure; oil temp.; fuel quantity and fuel pressure. No VSI.

The landing gear “borrowed” from a Sonerai II is available off-the-shelf from GPAS, with the complimentary wheel pants from Aircraft Spruce (ACS). The wheels and brakes were also supplied by GPAS and are comprised of standard Azusa aluminum wheels and go-cart style hydraulic disk calipers rated at 1,200 lbs gross. With the CX4’s 850 gross, they should work fine. With master cylinders affixed to each of the rudder pedals, and a full-castering tailwheel (attached to a leaf-spring– both of which are offered by ACS), ground operating the little taildragger is rather “conventional.”


Construction photos by Wilson Leonard

Although the design originally called for the rudder pedals to be suspended from an overhead torque tube fitted between the instruments and the header tank, the most recent iteration has them floor-mounted. This adds almost infinite flexibility with the location and can allow for more leg room as there is substantial distance between the specified pedal location and the back of the firewall. The issues with the old design, as shown above, were a little more involved than just leg room. In the original rudder pedal design, the weld joints were under an eccentric load. Some of the people who looked at this set up worried that at some point the pedals might break off at the weld. David came to agree with that and redesigned the system as shown below.

Keeping it simple, and for the most part, affordable, dictates using off-the-shelf parts where ever possible. The tailwheel and leaf spring are both available from Aircraft Spruce and Wicks Aircraft Supply.

CANOPY The aft section of the sliding canopy operates smoothly through the use of off-the-shelf, cabinet grade full extension drawer glides, sliding aft to clear the seatback bulkhead to allow for easy ingress and egress. The windscreen is robust enough to act as a handhold.

Construction photos by Wilson Leonard

Additionally, the attachment of the brake master cylinder is also eccentrically loaded. This tends to cause the brake extension rod to bend and buckle if applied under heavy pressure. Another point; the new design also gets the rudder pedal controls out of the way so a larger (10.5 gallon) fuel tank can be installed. And as one last good aspect, the new design is being looked at by the LAA in the UK, and they like the new design much better, although they want 1/8" cables instead of the push-pull cables now installed. Hydraulic master cylinders operated by depressing the upper portion of the rudder peddles are incorporated into either iteration of rudder control.

The curvaceous lines of the canopy are reminiscent of the P-38 Lightning or the Supermarine Spitfire. Although the airplane cannot be flown with the canopy slid back, it can be removed for open cockpit flight.

AESTHETICS Mr. Thatcher is an aviation artist, putting brush to canvas on a regular basis. When he was developing his conceptual design, which I’m told had its life begin on a napkin in a McDonald’s restaurant one morning during breakfast, he incorporated certain independent elements into his creation that he admired in other aircraft. The paint


Mr. Thatcher’s personal aircraft, the prototype and serial No. 1, has lived a rough life, having survived both Hurricanes Ivan and Rita and also all of the load testing done to date. Refurbished more than once, it’s become a staple at Sun ‘n Fun for the past few years and hopefully, beginning with 2008, a staple at OSH as well. scheme is classic. I can’t help but believe that the graceful lines of the airframe and complementing paint job probably contribute to a good portion of its success. The affordably and ease of construction are just the icing.

he has been very helpful through this process and very supportive as well. “I would not hesitate to do business with Great Plains again.”

Recognizing the inherent synergistic beauty of the CX4 package, Bill opted to copy it verbatim, save a marginally different instrument panel and a slight color difference in the accent striping. Where Dave chose black, Bill went with dark blue.

The ignition system is typical of most commercially available VW engines to see the market in the past few decades. The setup includes dual ignition with the top set of plugs fired by a Slick 4316 aircraft magneto driven by the crankshaft and hung from the accessory case that houses the internal alternator. The lower plugs are fired by a solid-state, waste-spark (lawnmower style) electronic ignition, with the ignition module driven by the camshaft installed where the original distributor was once resided. It isn’t elegant but it gets the job done.

THE ENGINE As previously noted, Bill opted to deviate a little from the plans by going with the 65 hp 1915 cc engine rather than the 55 hp 1700 cc specified by Thatcher. Although the most common displacement for a 60-65 hp VW is the tried and true 1835, Bill found that it costs the same to up it to 1915, making it the best bang for his buck. 2100 cc is next logical jump in displacement, but the price increases as well by almost $1,300 (for a 5 hp increase) as the crank stroke is increased and modifications to the case are required including a heavy-duty front bearing. For an additional $950, GPAS will build and test-run their kit engine for their customer, a cost that Bill was willing to incur as cheap insurance. Overall, he is very satisfied with his decision and with the personal service received from Steve Bennett, the owner of GPAS, telling us that

A personal watercraft battery (from Wal-Mart) offers plenty of cranking amperage for the geared (Subarustyle) starter, with enough left over to power the 12V electrical system. Continued on page 23 HP @ 3400 RPM


























Long block Cost


Bore (mm) Stroke (mm)

$2547 $2547 $3780 $3780

Prices shown are USD and do not include accessories. Add a minimum of $3500 to complete each engine kit.


Jack Kane has been actively involved in piston engine development since the early 1950s, and has configured, built and modified successful engines for a wide variety of specialized applications and winning race cars. As CEO of EPI, Inc., he has been responsible for the design and development of a line of liquid-cooled aircraft engines, propeller reduction drives, and accessory drive units for various applications. He writes technical articles for Race Engine Technology magazine. Beyond engineering, he is an accomplished machinist, a commercial pilot, certified flight instructor, and has done development, modification and overhaul work on certified (Lycoming, Continental, Orenda) aircraft engines. In his younger days, he was a winning driver in a variety of automobile racing categories including rear-engine formula cars, sports cars, midgets and stock cars, and has won several championships. Jack was a dean's list student in the Electrical Engineering program at the US Air Force Academy. Later, he earned Bachelor of Mechanical Engineering (cum laude) and Master of Science degrees (summa cum laude) from civilian universities. He holds a Masters Degree in engineering. Prior to starting EPI Inc., Jack spent 31 years designing and developing including research and design work on the first generation of Full Authority Digital Engine Controllers (FADEC); design and development of several complex real-time computer operating systems, control systems, and data communication networking systems; subsystems in computerbased controls including GPS, nuclear systems, data acquisition systems, missile flight control systems and satellite communication networking systems. He was a pioneer in the use of multi-level finite state automata to build bulletproof real-time control software systems.

Article and sidebar by Jack Kane

POWER and TORQUE In order to discuss powerplants in any depth, it is essential to understand the concepts of power and torque. However, in order to understand power, we must first understand work and energy. Here is a quick review of work and energy.

WORK Suppose the engine of your car stalls while you’re in line to exit from a flat, level parking lot. You try several times to restart it, but it just won't start. Since you are a considerate person, you decide to push your car out of the way of the people behind you. You get out and go round back and begin to push on the car. Suppose also that you are a fairly strong person, so you exert a horizontal force of 100 pounds on the rear of the car. The car doesn’t move. But you are also a persistent person, so you continue to push on the car for two whole minutes, exerting the same 100 pounds of force. The car still won’t move. Although you will probably be quite tired, you will have done no work. Why? Because work is defined as a force operating through a distance. The car didn’t move, so although there was force, there was no motion. Now you get smart and release the parking brake, and again push with the same constant 100 pound force. The car moves, and it travels 165 feet in two minutes. In that case, you will have produced 16,500 foot-pounds of WORK (100 pounds of force x 165 feet of distance).

ENERGY Later, you have recovered from the parking lot ordeal and are working in your shop. You need to install a 3inch long spring into a 2-inch space. The nature of this particular spring is that it takes 600 pounds of force to compress it one inch.

Jack currently holds a commercial pilot rating in multi-engine, single engine, and glider aircraft, and a private helicopter rating. He has been a certified flight instructor for single and multi-engine aircraft, and has worked as a Part 135 charter pilot, corporate pilot, glider-tow pilot, ferry pilot, and instructor in very-high-performance, tailwheel and aerobatic aircraft.

Using a lever-operated spring compressor, you pull on the lever with a force of 100 pounds and you move the lever 6 inches, causing the compressor to squeeze the spring and shorten it by 1 inch. The spring is now pushing on the compressor with a force of 600 pounds. You have stored the WORK you did on the compressor lever (100 pounds x 1 inch = 600 inch-pounds) in the spring, in the form of ENERGY (600 pounds and 1 inch).

He has PIC experience in a wide variety of aircraft as well as test-flight and demo work in various veryhigh-performance experimentals.

Energy is defined as the capacity of a body to do work, by virtue of the position or condition of the body.

We welcome Jack as a regular contributor to CONTACT! Magazine and look forward to reading his contributions in future issues.

Now suppose there is a 150-pound plate of steel on your bench, resting on four blocks which are 2 inches tall (so the space between the bottom of the plate and the bench is 2 inches). You install the compressed spring into that


space and locate it at exactly the center of gravity of the plate, and release the spring compressor. The spring will lift the steel plate 3/4 of an inch, so the spring has done work on the plate, thereby releasing some of the energy stored in the spring. There are many different forms of energy. There are a few which are of particular interest with respect to powerplants: kinetic energy (the energy contained in a body by virtue of its velocity), potential energy (the energy contained in a body by virtue of its position), chemical energy (energy which can be released by a chemical reaction, such as combustion), and heat energy (energy which can be used to make machines operate).

POWER and TORQUE It often seems that some engine people are confused about the relationship between POWER and TORQUE. For example, I have heard engine builders, camshaft consultants, and other technical experts ask their customers: "Do you want your engine to make horsepower or do you want it to make torque?" The question is posed in a tone which strongly suggests that these experts believe power and torque are somehow mutually exclusive. In fact, the exact opposite is true, and we all need to be clear (all on the same page) on these facts: Power is defined as the amount of work done per unit time, or the rate of doing work. Torque and RPM are the measured quantities of engine output. Power is a quantity which is calculated from torque and RPM, by the following equation: HP = Torque x RPM ÷ 5252 An engine produces power by providing a rotating shaft which can exert a certain amount of torque on a load at a certain RPM. The amount of torque the engine can exert usually varies with RPM. A dynamometer (dyno) substantiates the power an engine produces by applying a load to the engine output shaft by means of a water brake, a generator, an eddy-current absorber, or any other controllable device capable of absorbing power. The dyno control system causes the absorber to exactly match the amount of torque the engine is producing at any given instant. It then measures that torque as well as the instantaneous RPM of the engine shaft, and from those two measurements, it calculates observed power after factoring variables (air temperature, barometric pressure, relative humidity) in order to correct the observed power to the value it would have been if it had been measured at sea level-standard atmospheric conditions (corrected power).

Figure 1 Referring to Figure 1 (above), assume that the handle is attached to the crank-arm so that it is parallel to the supported shaft and is located at a radius of 12" from the center of the shaft. In this example, consider the shaft to be fixed to the wall. Let the arrow represent a 100 lb. force, applied in a direction perpendicular to both the handle and the crank-arm, as shown. Because the shaft is fixed to the wall, the shaft does not turn, but there is a torque of 100 pounds-feet (100 pounds times 1 foot) applied to the shaft. Note that if the crank-arm in the sketch was twice as long (i.e. the handle was located 24" from the center of the shaft), the same 100 pound force applied to the handle would produce 200 lb-ft of torque (100 pounds times 2 feet).

POWER Power is the measure of how much work can be done in a specified time. In the explanation of work and energy at the beginning of the article, By pushing the car you produced 16,500 foot-pounds of work. If you did that work in exactly two minutes, you would have produced 8,250 foot-pounds per minute of power (165 feet x 100 pounds ÷ 2 minutes). In the same way that one ton is a large amount of weight (by definition, 2,000 pounds), one horsepower is a large amount of power. The definition of one horsepower is 33,000 foot-pounds per minute. The power which you produced by pushing your car across the lot (8,250 footpounds-per-minute) equals one quarter horsepower (8,250 ÷ 33,000). OK, all that’s fine, but how does pushing a car across a parking lot relate to rotating machinery? Consider the handle-and-crank-arm sketch from Figure 1, but with these changes:

TORQUE Torque is defined as a force around a given point, applied at a radius from that point. Note that the unit of torque (force) is one pound-foot (often misstated), while the unit of work is one foot-pound.

The handle is still 12" from the center of the shaft, but instead of being fixed to the wall, the shaft now goes through the wall, supported by frictionless bearings, and is attached to a generator behind the wall.


Figure 2 Suppose, as illustrated in the sequence in Figure 2 (above), that a constant force of 100 lbs. is somehow applied to the handle so that the force is always perpendicular to both the handle and the crank-arm as the crank turns. In other words, the "arrow" rotates with the handle and remains in the same position relative to the crank and handle, as shown in the sequence above. (That is called a "tangential force"). If that constant 100 lb. tangential force being applied to the 12" handle (100 lb-ft of torque) causes the shaft to rotate at 2,000 RPM, then the power the shaft is transmitting to the generator behind the wall is 38 HP, calculated as follows: 100 lb-ft of torque (100 lb. x 1 foot) times 2,000 RPM divided by 5,252 = 38 HP. In order to make the concept more clear, here are 5 examples of real-world systems which produce 300 HP. Example 1: How much torque is required to produce 300 HP at 2700 RPM? Since HP = torque x RPM ÷ 5,252, then rearranging the equation to solve for torque produces: torque = HP x 5252 ÷ RPM Answer: torque = 300 x 5252 ÷ 2700 = 584 lb-ft. Example 2: How much torque is required to produce 300 HP at 4,600 RPM? Answer: torque = 300 x 5,252 ÷ 4,600 = 343 lb-ft. Example 3: How much torque is required to produce 300 HP at 8000 RPM? Answer: torque = 300 x 5,252 ÷ 8,000 = 197 lb-ft. Example 4: How much torque does the 41,000 RPM turbine section of a 300 HP gas turbine engine produce? Answer: torque = 300 x 5,252 ÷ 41,000 = 38.4 lb-ft. Example 5: The 300 HP engine in Example 4 drives a gearbox which turns a propeller at 1,591 RPM. How much torque is applied to that shaft? Answer: torque = 300 x 5,252 ÷ 1,591 = 991 lb-ft. (ignoring losses in the gearbox, of course). The point to be taken from those numbers is that a given amount of horsepower can be made from an infinite number of combinations of torque and RPM.

Think of it another way: In cars of equal weight, a 2-liter twin-cam engine that makes 300 HP at 8,000 RPM and 400 HP at 10,000 RPM will get you out of a corner just as well as a 5-liter engine that makes 300 HP at 4,000 RPM and 400 HP at 5,000 RPM.

GENERAL OBSERVATIONS In order to design an engine for a particular application, it is helpful to plot out the optimal power curve for that specific application, then from that design information, determine the torque curve which is required to produce the desired power curve. By evaluating the torque requirements against realistic BMEP (brake mean effective pressure) values you can determine the reasonableness of the target power curve.

Brake Mean Effective Pressure (BMEP) is another very effective yardstick for comparing the performance of one engine to another, and for evaluating the reasonableness of performance claims or requirements. The definition of BMEP is: the average (mean) pressure which, if imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output. Note that BMEP is purely theoretical and has nothing to do with actual cylinder pressures. It is simply an effective comparison tool. If you work through the arithmetic, you find that BMEP is simply a multiple of the torque per cubic inch of displacement. A torque output of 1.0 lb-ft per cubic inch of displacement equals a BMEP of 150.8 psi. in a four-stroke engine and 75.4 psi. in a two-stroke engine. The discussion on the remainder of this page is with respect to four-stroke engines, but it applies equally to two stroke engines if you simply substitute 75.4 everywhere you see 150.8 (cut it in half) If you know the torque and displacement of an engine, a very practical way to calculate BMEP is: BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci) Continued on next page


Typically, the torque peak will occur at a substantially lower RPM than the power peak. The reason is that, in general, the torque curve does not drop off (percentwise) as rapidly as the RPM is increasing (percent-wise). For a race engine, it is often beneficial (within the boundary conditions of the application) to operate the engine well beyond the power peak, in order to produce the maximum power within a required RPM band. However, for an engine which operates in a relatively narrow RPM band, such as an aircraft engine, it is generally a requirement that the engine produce maximum power at the maximum RPM. That requires the torque peak to be fairly close to the maximum RPM.

Note that, with a torque peak of 587 lb-ft at 3,000 RPM, the pink power line peaks at about 375 HP between 3,500 and 3,750 RPM. With the same torque curve moved to the right by 1,500 RPM (black, 587 lb-ft torque peak at 4,500 RPM), the peak power jumps to about 535 HP at 5,000 RPM. Again, moving the same torque curve to the right another 1,500 RPM (blue, 587 lb-ft torque peak at 6,000 RPM) causes the power to peak at about 696 HP at 6,500 RPM.

For an aircraft engine, we typically like to see the torque curve peak at the normal cruise setting and from there, stay essentially flat up to maximum RPM. That positioning of the torque curve would allow the engine to produce significantly more power if it could operate at a higher RPM, but the goal is to optimize the performance within the operating range. An example of that concept is shown Figure 3. The three dashed lines represent three torque curves having exactly the same shape and torque values, but with the peak torque values located at different RPM values (3,000, 4,500, and 6,000 RPM). The solid lines show the power produced by the torque curves of the same color. Figure 3 BMEP- Continued from previous page

This tool is extremely handy to evaluate the performance which is claimed for any particular engine. For example, the 200 HP IO-360 (360 CID) and 300 HP IO540 (540 CID) Lycomings make their rated power at 2,700 RPM. At that RPM, the rated power requires 389 lb-ft and 584 lb-ft of torque respectively. From those torque values, it is easy to see that both engines operate at a BMEP of about 163 PSI. (1.08 lb-ft of torque per cubic inch) at peak power. The BMEP at peak torque is slightly greater. For a long-life, naturally-aspirated, gasoline-fueled, twovalve-per-cylinder, pushrod engine, a BMEP over 200 PSI is difficult to achieve and requires a serious development program and very specialized components. For comparison purposes, let's look at what is commonly believed to be the very pinnacle of engine performance: Formula-1 (Grand Prix). An F1 engine is purpose-built and essentially unrestricted. For 2006, the rules required a 90° V8 engine of 2.4 liters displacement (146.4 CID) with a maximum bore of 98 mm (3.858”) and a required bore spacing of 106.5 mm (4.193”). The resulting stroke to achieve 2.4 liters is 39.75 mm (1.565”) and is implemented with a 180° crankshaft. The typical rod length is approximately 4.016” (102 mm), for a rod/stroke ratio of about 2.57:1. These engines are typically a 4-valve-per cylinder layout with two overhead cams per bank, and

pneumatic valve springs. In addition to the few restrictions stated above, there are the following additional restrictions: (a) no beryllium compounds, (b) no MMC pistons, (c) no variable-length intake pipes, (d) one injector per cylinder, and (e) the requirement that one engine last for two race weekends. At the end of the 2006 season, most of these F1 engines ran up to 20,000 RPM in a race, and made in the vicinity of 750 HP. One engine for which I have the figures made 755 BHP at an astonishing 19,250 RPM. At a peak power of 755 HP, the torque is 206 lb-ft and peakpower BMEP would be 212 psi. (14.63 bar). Peak torque of 214 lb-ft occurred at 17,000 RPM for a BMEP of 220 psi (15.18 bar). There can be no argument that 212 psi at 19,250 RPM is truly amazing. However, let's look at some astounding domestic technology. The 2006 Nextel Cup engine is a severelyrestricted powerplant, being derived from production components. It uses a production-based cast-iron 90° V8 block and 90° steel crankshaft, with a maximum displacement of 358 CID (5.87 liters). A typical configuration has a 4.185" bore with a 3.25" stroke and a 6.20" connecting rod (R/S = 1.91). Cylinder heads are similarly production-based, limited to two valves per cylinder, but highly developed. The valves are operated by a single, engine block-mounted, flat-tappet camshaft. Continued on next page


Using the black curves as an example, note that the engine produces 500 HP at both 4,500 and 5,400 RPM, which means that the engine can do the same amount of work per unit time (power) at 4,500 as it can at 5,400. However, it will last much longer at 4,500, and it will burn less fuel to produce 500 HP at 4,500 RPM than at 5,400 RPM, because the parasitic power losses (power consumed to turn the crankshaft, reciprocating components, valvetrain) increases by the square of the crankshaft speed (RPM).

It is the same as the graph on the previous page, except that the blue torque curve has been altered (as shown by the green line) so that it doesn't drop off as quickly. Note how that causes the green power line to increase well beyond the torque peak. Such a change to the torque curve can be achieved by altering various componentslobe profiles and separation, runner length and/or cross section to name a few. Alterations intended to broaden the torque peak will inevitably reduce the peak torque value, but the desirability is based on the application.

The RPM band within which the engine produces its peak torque is limited. You can tailor a high peak with a very narrow band, or a lower peak value with a wider band. Those characteristics are usually dictated by the parameters of the application for which the engine is intended. An example of that is shown in Figure 4 below.

REAL WORLD EXAMPLES Because the power which a piston engine can produce is directly related to the mass flow of air through the engine, then it stands to reason that any changes which cause the engine to pump more air ("breathe" better) will enable it to make more power. Those changes obviously include the simple approach of operating the engine at a higher RPM. However, that approach has its limitations, as you might have already deduced from the preceding discussion of torque curve location. The target operating range of a high-performance engine is usually determined by deciding the maximum operating speed the engine can survive for the required number of hours- or seconds, as is the case with many dragracing engines. If you are an engine designer, you make that determination based on sophisticated and extensive finite element analysis (FEA) stress and thermal analysis, followed by extensive dyno-cell testing. If you are less sophisticated, perhaps you rely on "rules of thumb", experience, or wishful thinking.

Figure 4 Continued from previous page

That's right, still no rollers and no overhead cam. It is further hobbled by the requirement for a single fourbarrel carburetor. Electronically-controlled ignition is not allowed, and there are minimum weight requirements for the connecting rods and pistons. How does it perform? At the end of the 2006 season, the engines were producing in the neighborhood of 825 HP at 9,000 RPM. They could, however, produce more power at 10,000 RPM, but engine RPM has been restricted by means of a rule limiting the final drive ratio at each venue. 825 HP at 9,000 RPM requires 481 lb-ft of torque, for a peakpower BMEP of nearly 203 PSI (14.0 bar). Peak torque was typically about 520 lb-ft at 7,500 RPM, for a peak BMEP of over 219 psi (15.1 bar). THAT is truly astonishing. Compare the F1 engine figures to the Cup engine figures for a better grip on just how clever these Cup engine guys are. To appreciate the value of this tool (BS detector if you will), suppose someone offers to sell you a 2.8 liter (171 cubic inch) Ford V6 which allegedly makes 230 HP at

As a point of reference, in 2006, Formula One engines routinely reached 20,000 RPM (that's not a typo: twenty thousand!) with a mean piston Continued on page 16

5,000 RPM, and is equipped with the standard iron heads and an aftermarket intake manifold and camshaft. You could evaluate the reasonableness of this claim by calculating that 230 HP at 5,000 RPM requires 242 lb-ft of torque (230 x 5252 รท 5000), and that 242 lb-ft. of torque from 171 cubic inches requires a BMEP of 213 PSI (150.8 x 242 รท 171). You would then dismiss the claim as preposterous because you know that if a guy could do the magic required to make that kind of performance with the stock heads and intake design, he would be renowned as one of the pre-eminent engine gurus in the world. You would later discover that the engine rating of "230" is not actual horsepower. As a matter of fact, in order to get a BMEP value of 214 from our aircraft V8, we had to use extremely well developed, high-flowing, high velocity heads, a speciallydeveloped tuned intake and fuel injection system, very well developed roller-cam profiles and valve train components, and a host of very specialized components which we designed and manufactured. Jack Kane


The author has asked us to keep his contact info anonymous as he’s offering this set of drawings and this brief description for our readers’ edification and wishes to indemnify himself from any mishap that may ensue. Oscar Zuniga, a regular contributor to CONTACT! Magazine, offered to add his handwork art on the next page. The “typical” stall does not include a complete loss of lift. The wing is still making some lift, just not enough to do what we need for it to do. The device depicted in this article has been referred to as an angle of attack meter, a lift management system and an airspeed system. It is probably a little of all of the above. But one thing it certainly does for us is to indicate how much lift we have in “reserve” before things turn ugly. The lift reserve indicator we are talking about is similar to the instrument known commercially as the LRI- Lift Reserve Indicator, manufactured and distributed by InAir Instruments, LLC; 7188 Hollandia Drive, Westerville, Ohio 43081-9319 They offer an unheated unit for $450.00 and a heated version for another $50– plus a nominal shipping fee. The home-made unit consists of a rectangular shaped air stream probe and a commercially available differential pressure gauge. There are two air pressure ports, each on separate faces of the probe. The differential pressure between the two ports yields lift-reserve readouts. The high pressure port on the gauge is connected to the top surface port. The gauge used is a “DWYER MINIHELIC II” pressure gauge. Part number 2-5002.This gauge reads from zero to two inches of water column. The gauge face is removable and is modified by the builder to have 3 separate zones. The first zone is the “red zone” which is from 0 to .5” of water. The second zone (white or yellow) goes from .5” to 1.0” of water. The third zone is from 1.0” to 2.0” of water column. The red zone indicates that the airplane is no longer generating enough lift to sustain level flight The top of the red sector and the bottom of the white or yellow sector is the point that wing is generating “just” enough lift to support the aircraft. During takeoff as the needle clears the red sector and moves into the yellow sector the plane has enough lift for takeoff. On landing the goal is to get the tires to just touch the runway when the needle is one mark from the top of the red sector. (0.4”) You will rotate the probe and repeat landings until the needle is at this point. The probe position should be marked in this position so that it will be evident during a preflight if it has moved. The white or yellow sector is the slow speed region of the aircraft. The final approach on landing is flown with the needle centered in the white or yellow zone. The turn to final should be done with the needle no lower than the white/ green zone.

The green zone indicates ample lift and the needle will most probably be pegged. (2.0”) Of course the builder can use any colors and graphics he chooses. The location of the probe should be out of the propwash and located between 15% and 30% of the wing chord as measured from the leading edge. The angle to start is recommended to be about 50 degrees from the bottom of the wing. A Cessna 172 that was fitted with this device had the probe at 69.5 degrees from the bottom of the wing surface. You will have to determine this on your own plane. It is recommended by some that any AOA gauge be mounted at the top left portion of the instrument panel so that the eyes don’t have to move far from where they look during the landing phase, but that is only if you fly just left-hand patterns or only fly from the left seat.

BETTER THAN AN AIRSPEED INDICATOR? No matter how you slice it, a properly calibrated AOA indicator of any make or design is way better than not having any at all or relying on the ASI or the stall warning system for stall avoidance. Inadvertent stall is just too commonplace and quite frankly, deadly– and totally avoidable. The NTSB records are literally packed with statements that read, “Probable cause of this accident was the pilot’s failure to maintain adequate airspeed, resulting in a stall.” The fallacy here is the reliance upon airspeed over AOA. Had these pilot maintained adequate AOA, airspeed would have been irrelevant– and to a great extent it is irrelevant as the stall speed of a given airframe changes with weight, and/or bank angle. In a 75 degree bank you need double the straight and level stall speed to keep flying; YES... DOUBLE. This instrument takes this into account: if the needle is dropping down through the yellow you are approaching loss of lift no matter what the airspeed says. Once you fly with it, this will quickly become your preferred performance instrument. Several users say they would rather give up their airspeed than the lift reserve or angle of attack indicator. Another commercially available variant of this system is available from Peter Cowan who has assembled a kit: Peter can be reached at and his website has a section where you can read comments from users and see alternative construction and installation methods and techniques.



Oscar Zuniga


Power and Torque continued from page

speed in excess of 5,200 feet per minute, producing over 750 HP @ 19,250 RPM from 146 normally-aspirated cubic inches (2.4 liters) of displacement. By comparison, the Continental A-65 produces 65 hp @ 2,700 RPM with 170 cubic inches of displacement. ~Pat These engines would survive for several hours of racing without substantial degradation in power. The cost of each was more than the cost of the average home. One of the common rules of thumb for aircraft engines (proven by countless examples) is to limit mean piston speed to less than 3,000 fpm. Mean piston speed (mps) is a fundamentally meaningless empiricism, calculated by the following equation: { MPS = Stroke (inches) x RPM / 6 }. So, for example, an engine with a 4-inch stroke at 4,000 RPM has an MPS of 2,667 fpm, and 3,000 fps at 4,500 rpm. However, with the quality of the componentry available today, bottom end concerns at 3,000 fpm are not generally a worry. Of much greater importance is the longevity of the valvetrain. As engine speed increases, the stresses and deflections on the valvetrain components go up exponentially, and generally those components are the first to fail. Having selected an appropriate operating speed, one then designs the air passages (intake manifold plenum and runner size, path and taper, cylinder head port sizes, shapes, tapers, valve sizes, combustion chamber shape, exhaust tube size, length, configuration, etc) and the breathing apparatus (cam lobe lift, duration, velocity, acceleration; valvetrain configuration, spring rates, loads, stresses and resonant frequencies; etc.) to achieve the torque curve which produces the desired power curve. For a real example, consider a 5.0 liter Ford Windsor small-block, built with high-quality bottom-end components. Initially, the engine was equipped with Edelbrock Victor-Jr. aluminum heads, a Performer-RPM dual-plane intake manifold, a 750-CFM four barrel carburetor and a fairly mild camshaft (216-0.544 / 224-0.555 / 112). On the dyno, that combination produced a peak torque of 328 lb-ft at 4,800 RPM. Not a very-impressive BMEP of 164 psi, about the same as an angle-valve Lycoming 360 or 540) and peak power of 331 HP at 6,000 RPM- 31 more ponies than an angle-valve Lycoming IO-540 turning 2,700 RPM.

1992 Honda RA122 F-1 V12 Engine - McLaren MP4/6B & MP4/7A F1 Formula One. DERIVATION OF THE POWER/TORQUE EQUATION Occasionally, after hearing power and torque explained, someone will ask: "OK, if HP = RPM x TORQUE ÷ 5252, where does the 5252 come from?" Here is the answer but don't be put off by the arithmetic; at worst, it requires only 8th grade algebra. By definition, power = force x distance ÷ time. Using the example in Figure 2 on page 10, where a constant tangential force of 100 pounds was applied to the 12" handle rotating at 2,000 RPM, we know the force involved, so to calculate power, we need the distance the handle travels per unit time, expressed as: Power = 100 pounds x distance per minute OK, how far does the crank handle move in one minute? First, determine the distance it moves in one revolution, which in very simple terms is the circumference of a 24” diameter (12” radius) circle.

In order to move the torque curve higher, and thereby produce more power, the heads, intake manifold and cam were replaced with the following components: AFR 205 heads, an Edelbrock Victor-Jr. single-plane intake manifold, and a more aggressive camshaft- 248-0.614 / 254-0.621 / 110. That combination produced a torque curve with essentially the same shape as the first combination, but shifted to a higher RPM band. Peak torque of 335 lb-ft at 5,600 RPM, peak power of 388 HP, at a mean piston speed of 3,400 FPM, but at a valvetrain-killing speed of 6,800 RPM. Both configurations curves are shown in Figure 5.

Figure 5


Sadler Vampire, continued from page 3

Distance per revolution (circumference) = pi x dia. Distance per revolution. = 3.1416 x 2 = 6.283 ft. Now we know how far the crank moves in one revolution. How far does the crank move in one minute? Distance per min. = 6.283 ft .per rev. x 2,000 rev. per min. (RPM) = 12,566 feet per minute.

buyers with extras. When you look at the list of standard features on a Vampire, I think you’ll find the fly-away price more than competitive with virtually every S-LSA on the market” said Littlejohn. “Based on the feedback we’ve received from air shows and emails, we’ve also added a kit option for folks who want to build their own E-LSA or experimental, amateur-built Vampire.”

Now we know enough to calculate the power, defined as: power = force x distance ÷ time so Power = 100 lb x 12,566 ft. per minute = 1,256,600 ft-lb per minute. Swell. But how about horsepower? Remember that one horsepower is defined as 33,000 footpounds of work per minute. Therefore HP = power (ft-lb per min) ÷ 33,000. We have already calculated that the power being applied to the crank-wheel above is 1,256,600 ft-lb per minute. How many HP is that? HP = (1,256,600 ÷ 33,000) = 38.1 HP. Now we combine some stuff we already know to produce the magic 5,252. We already know that: Torque = force x radius. If we divide both sides of that equation by the radius, we get: (a) force = torque ÷ radius Now, if distance per revolution = radius x 2 x pi, then (b) Distance per minute = radius x 2 x pi x RPM And we already know that: (c) Power = force x distance per minute So if we plug the equivalent for force from equation (a) and distance per minute from equation (b) into equation (c), we get: Power = (torque ÷ radius) x (RPM x radius x 2 x pi) Dividing both sides by 33,000 to find HP: torque ÷ radius x RPM x radius x 2 x pi HP = 33,000

The full height of the wings when folded is 8 feet and the overall width is also 8 feet, making the Vampire legally towable without any special permits. And at 19’-4” long, the Vampire will fit in most garages, eliminating the need for a hangar, further reducing operating expenses.

OTHER TECHNICAL TIDBITS Each wing panel is 5 feet wide. Sadler plans to skin each section with a single seamless sheet of 0.016” 2024T3 Alclad aluminum, bonding the skins to the ribs and riveting at the spars. An inner wing panel weighs approximately 33 pounds when complete and the outer wing panel weighs approximately 27 pounds. Not shown in the photo below are the downward-turned tips that will be added. The tips will be made out of composite materials and will not affect wing folding.

By reducing, we get: torque x RPM x 6.28 HP = 33,000 Since 33,000 ÷ 6.2832 = 5,252, therefore: HP = TORQUE x RPM ÷ 5252 Note that at 5,252 RPM, torque and HP are equal. At any RPM below 5,252, the value of torque is greater than the value of HP; Above 5,252 RPM, the value of torque is less than the value of HP. Jack Kane Founder and CEO of EPI Inc. PO Box 115 Amboy, WA 98601 (360) 247-5858

When CONTACT! Magazine questioned Littlejohn about the possibility of a kit for the Sadler Piranha– the 450 HP air-to-ground attack fighter designed by Bill Sadler– Littlejohn just smiled and said “I can neither confirm nor deny these rumors.” Sadler Aircraft is currently accepting orders for the Vampire and expects to begin delivering completed aircraft in November of 2009. Sadler Aircraft, Roseburg, OR • 919-264-6000


By Lawrence D. Kerr and Gwen Maxwell We introduced CONTACT! readers to Maxwell Propulsion in issue #95. I had the pleasure of touring their facilities and flying their demonstrator last year right after OSH. One thing that was mentioned to me while spending time with Gwen Maxwell was that they used information found in one of our articles to work out torsional vibration concerns with their engine package. I asked Gwen if she would be kind enough to write us an article on the process they used, so here it is. ~Pat

ure resulting from torsional vibration. The design requirements included a projected TBO of at least 1,500 hours. While the heart of an automotive conversion for aircraft use is the PSRU, MPS also believes in building quality from the start. All MPS engine packages are based on a Subaru EJ25 STI Turbo block and the stock EJ25 normally aspirated heads. The short block is disassembled, then balanced and blueprinted. The Subaru long block is then coupled with a dual ignition system, custom throttle body, exhaust, cooling, and mounting system. For a very detailed description of the systems and components, see CONTACT! Magazine issue #90.

INTRODUCTION AND BACKGROUND The vibration dampening system between a piston engine and a propeller speed reduction unit (PSRU) must be designed to minimize the potentially damaging effects of the torsional vibrations produced by piston engines on the gears and shafts. Since the early days of converting automotive engines to experimental aircraft use, a variety of PSRU designs have been developed to include torsional vibration dampening between the engine and PSRU, be they gear, belt, or chain driven. The subject of torsional vibration continues to be surrounded by mysticism. One myth is that any level of torsional vibration will inevitably lead to a catastrophic failure of the prop shaft, the gear set, or other flight critical components. In truth, as long as the level of vibration is kept below the fatigue strength of each system component, there will not be a failure due to torsional vibration. It is the responsibility of the engineer/designer to incorporate appropriate safety factors into the design, and then to test the finished product, to ensure the level of reliability one expects in an aircraft. Despite the fact that many designs have experienced mechanical or structural failures, there has been remarkably little scientific testing and analysis done on the effects of engine vibration on the PSRU.

MPS ENGINE AND PSRU In fall 2006 Maxwell Propulsion Systems, Inc. (MPS) made the decision to develop a new geared PSRU. The MPS goal was to bring into the experimental aviation marketplace a scientifically-designed and tested system that would address the critical issues of fatigue and

DEVELOPMENT AND DESIGN CHALLENGES Guided by preliminary market research, the initial MPS PSRU development proceeded along two parallel paths to address the design and testing objectives. The first approach used an automotive-style racing clutch to engage and disengage the PSRU. We chose the Tilton 5.5� rally clutch assembly coupled with the Tilton disc pack and hydraulic release (throw-out) bearing. MPS assembled a complete firewall forward system on a mockup of a GlaStar cockpit/firewall, then mounted this to the flatbed trailer shown in the photo above. This package was ground tested between July and September of 2007. The test results demonstrated that an automotive clutch could effectively minimize the damaging effects of torsional vibration. However, designing an effective process to engage and disengage the clutch would require cumbersome activators that were not pilot-friendly. Given these results, MPS immediately moved to incorporate a one-piece elastomeric coupler from Lord Corporation into the design.


An initial consultation with Lord indicated this could be a cost effective solution, with few modifications required to fit into the design envelope. Unfortunately, initial testing of a prototype unit showed it was not effective at keeping torsional vibration below the desired level. Construction of a more sophisticated unit that allowed testing of elastomeric bushings of a number of different durometer ratings showed little improvement. A parallel investigation into the engine attachment frame design (suggested by Hugh Evans) produced some minor improvements and convinced us it was not the root of the problem. We returned to David Kalivoda at Lord Corporation for more extensive consulting using their proprietary simulation software for coupling design. Feeding estimates for the mass elastic properties of all the mechanical components into the simulation and optimizing wherever possible, gave us our next design iteration. We were able to use off-the-shelf elastomeric bushings housed by a metal plate at a much larger bolt circle diameter to produce the torsional characteristics desired. Construction of a prototype unit, and some initial testing gave us encouraging results. We then followed up with a validation of the entire package as regards its torsional vibration. A key component of the validation procedure of the MX1 engine package included performing a vibration test similar to the one reported in Issue #90 of CONTACT! Magazine, “A Vibration Study of a Mazda 13B Installation in a Van’s RV-6A”, by Steve Boese. The primary purpose of the test was to assure that the torsional coupler between the engine and the gear box was working as designed. In addition, we also wanted to ensure there were no outstanding mechanical resonances that would adversely affect the longevity of the gearbox or engine package. The results of the tests on that final design are described below. These results demonstrated that all observed vibrations fell well below the maximum tolerable level. After approximately 140 hours of ground testing and 260 hours of flight testing in N787MX, MPS believes that their PSRU meets both their design expectations as well as the practical requirements for their Subaru automotive conversion.

ation kit, part number KIT3109MMA7260QE, with a mounting fabricated by our machine shop. The accelerometer has three axes and a selectable range from +/1.5g to +/- 6g maximum. We did not use a sensor on the propeller since the propeller turns more slowly than the engine due to the gearbox, and we were primarily interested in engine-coupled vibrations. We did, however, use a tachometer signal from the ignition controller when required. Data were collected from the accelerometer using a National Instruments USB-6009 Data Acquisition device s/details.cfm?id=770. We also used the National Instruments Signal View software that came with the device, on a Lenovo ThinkPad T61p, to process the data. Signal View is sophisticated enough to provide accelerometer voltage vs. frequency graphs out of the box, but not quite customizable enough to embed calibration data for the accelerometer and provide G-level readings directly. Working backwards from the maximum vibration levels permitted by the machinery vibration severity guide shown in issue #90 and the calibration data for the accelerometer, we calculated max voltage level at each frequency to remain within the acceptable and tolerable ranges for reciprocating engines.

RUNNING THE TEST The engine was started on the test stand (see photo– previous page), and run at medium idle until temps and pressures were within the operating range. We decided to test for vibration levels every 200 RPM from 3,200 to 5,400 RPM. Throttle and prop pitch were adjusted for a typical engine output at each RPM and a ten second sample of the vibration level recorded from the accelerometer. Between readings, the engine RPM was returned to idle. Excluding warm-up, sampling and recording the data took approximately an hour of run time to acquire.

PROCESSED DATA Critical vibration frequencies are usually the first and second order, or 1X and 2X the engine RPM. Levels for

TEST CELL SETUP The engine package, with its attachment frame, was bolted to a test stand consisting of the cabin structure of a GlaStar kit plane, complete with firewall and a simplified instrument panel. Instruments included a tachometer, manifold pressure, engine oil temp, engine coolant temp, gear box temp, and exhaust gas temperatures from each cylinder. As seen in the adjacent photo, controls included the ignition and throttle. The cabin structure was bolted securely to a small trailer, allowing extended engine testing to take place on the far side of the Arlington, WA airport in an area designated by the airport authority for this purpose.

DATA COLLECTION AND SOFTWARE The accelerometer used was the same as the one used by Steve Boese, a Freescale Semiconductor, Inc.


these were read from the accelerometer data, along with the highest peak that was NOT a first or second order vibration. The data from every sample are shown in the

table below. The chart to the right shows that the first and second order vibration levels are well below the maximum tolerable level.

3,200 RPM

4,800 RPM

4,000 RPM

5,400 RPM


PSRU INSPECTIONS In addition to the vibration analysis conducted on the MX1 PSRU, we also conducted a detailed examination of the PSRU during a complete tear-down following 75 hours of ground testing as well as a visual inspection through a borescope after approximately 120 hours. Neither of these inspections revealed any wear beyond a normal break-in polish on either the pinion or driven gears. Bearings were still within nominal limits at 75 hours, and the torsional coupling components were in original condition. Driven gear, 75 hours

CONCLUSIONS We are pleased that the test results demonstrated vibration levels of the final MX1 system design were at acceptable levels, with only two minor excursions into the lower levels of the tolerable zone. The PSRU longevity continues to be evaluated; however, initial inspections appear to corroborate that the design specifications for a 1,500 hour TBO have been met or exceeded. As we continue to accrue actual flight hours on the first production PSRU now installed on N787MX, we continue to evaluate the system for evidence of gear wear. The total number of hours is nearly 400 (140 ground test and 260 flight test). We expect to do a complete tear-down inspection after AirVenture 2009 when the system will have approximately 450 hours logged. We would like to acknowledge Mr. Steve Boese, his friend Doug Dempsey, and DLI Engineering for their willingness to share their knowledge and experience with the readers of CONTACT! Magazine. Our sincere appreciation also to the engineering staff at Lord Corporation and Mr. Hugh Evans for sharing their expertise.

Pinion gear, 75 hours


An update from Maxwell Propulsions By Gwen Maxwell Every year for the past six years, CONTACT! Magazine has hosted a fly-in event focusing on alternative engines. We do our best to have quality forums by inviting vendors and experimenters to present their products and/or accomplishments. In the past we’ve had notables such as Klaus Savier of Light Speed, Jess Meyers of Belted Air Power, Joe Horvath of Revmaster, Scott Casler of Hummel Engines– just to name a few. This year we chose to go with somewhat of an all-Subaru theme and were able to entice Maxwell Propulsion Systems to join us. They gave a very informative talk not just on their products but on Subarus in general. The following is a brief account of their experience with our growing event. We appreciate their attendance and are grateful for their professional attitude. They brought their “A” game and presented their program as if they were at a much larger venue. The people who took advantage of the familiarization flights being offered truly benefited. As the story goes, last March Pat Panzera called me and asked if Maxwell Propulsion Systems could bring our Sportsman to CONTACT! Magazine’s “Alternative Engine Roundup.” To be honest, this was way down on my seemingly endless list of Must Do’s. Among other things my left thumb and I had just had a run-in with a razor blade where the razor blade won. As a result, I was in a cast and not very functional. But Pat was persistent and made some pretty strong arguments for wanting MPS to represent the Subaru piece of the alternative engine market. So, I approached our test pilot, Ephraim, with Pat’s suggestion. Any of you who know Ephraim know that my task was pretty simple, Ephraim simply lives, and loves, to fly! That easily the decision was made. Bright and early Friday, March 27th, N787MX (aka the Maxwell Dreamliner) was fueled and filled with snacks, materials for the forum and the survival gear required for all cross-country sojourns. The weather in the greater Seattle area (we are based out of Arlington WA) was cooperating quite nicely with light tailwinds. After a refueling stop in Medford OR, 8.9 flight hours and 1,140 miles later, we arrived at the tiny albeit very hospitable Jean, Nevada airport. The normally aspirated 165 HP system burned an average of 7.6 gph at 115 knots. The Saturday forums were broad-based, informative, and well attended. I personally appreciated having an audience dedicated to the true spirit of experimental aviation– the alternative powerplant enthusiasts. Their questions were good, their interest genuine and with luck, perhaps I can help some of them get flying behind a

Photo: Rick Lindstrom Ephraim Carter and Gwen Maxwell, in front of the MPS “Dreamliner” (see the cover of issue #95) at the 6th annual Alternative Engine Round-up Subaru! Our caterer, aka Pat Panzera and his ablebodied assistants did an amazing job organizing the agenda, venue, and food, including a continental breakfast, pizza lunch and sirloin tip and roasted chicken dinner. Burgers were on the menu but the upgrade was welcomed. Having been responsible for similar events, I know how much energy it takes to organize them so it was, in my humble opinion, a hats-off event. Sunday morning found us back in N787MX. Alas, on this 1,177 mile return trip the weather was not quite so accommodating. We encountered headwinds of 50+ kts, dropping our average ground speed considerably. Refueling in Reno was certainly an interesting event. We encountered low ceilings north of Grants Pass, OR and returned to the Grants Pass airport for refueling. The weather eventually cleared and we were on our way again, with incredible head winds once more. Nevertheless, in addition to time passing, the miles passed as well. Finally, 10.5 hours of flying brought us back to KAWO- tired, and both VERY glad to be on home turf once again. We toasted to one very successful trip and I can now say I have flown in a small aircraft on a serious cross-country! Addendum: the cross-country story gets better. A month later Ephraim and I left Arlington for the Alaska Airman’s show in Anchorage. Total round-trip flight time was 38 hours. The day after we returned I told Dominic and Craig, “We have to finish the Turbo!” Being guys, they sort of listened to me but rather than a turbo, MPS is now offering a 195+ hp normally aspirated engine package. This system will be the one we will fly to AirVenture 2009. Initial flight tests showed 130 kts cruise and less than 9 gph. N787MX should have the Sportsman cowl (the current cowl is for the GlaStar), a tuned exhaust, side vented radiators, and new livery for our flight to


Continued from page 7 ons. The landing speed that works for Bill is 60 mph on approach. A comfortable cruise is 120 mph with 130 mph possible at 3100 RPM at about 22 inches of mercury on the manifold pressure (MP) gauge. Top speed is 135 mph. Bill’s preference is to operate the engine at 2900 rpm, or about 19 inches of MP which usually nets 120 mph. Fuel burn at this “cruise” setting is approximately three gallons per hour, running automobile fuel– 40 miles per gallon in no-wind conditions.

Photo courtesy Bill Stinson

The wheel pants and the spinner are off the shelf from Aircraft Spruce. The 54” diameter by 44” pitch wooden prop is provided by Tennessee Propellers. The float bowl carb is a very simple and proven updraft unit made by Zenith and features a cable-controlled choke, low speed idle bleed screw, mid to high range fully cockpit adjustable mixture control, idle adjustment screw, and a float bowl vent to help prevent vapor lock. GPAS recommends the use of either an electric or mechanical fuel pump, or no pump at all if you have at least .5 pounds of fuel pressure by gravity feed and can flow a minimum of 10 to 12 gallons per hour at your highest angle of attack. If you are going to run auto fuel, a fuel pump is a must according to GPAS.

PERFORMANCE The reported stall speed on Bill’s plane meets the design target of 40 mph. There are no flaps, just full-span ailer-

The CX4 is reported to be a very stable and yet fun-to-fly aircraft. With ample dihedral in the wing, additional dihedral in the tips, full-span ailerons and sufficient elevator control for balance in all three axes, the plane is responsive but by no means a squirrelly airplane. Bill reports that it’s very its very rewarding to fly in smooth air, with his feet off the rudder pedals and his hands off the control stick. When properly trimmed and it will fly straight and level for a long time. But when it’s time to have fun, very small control inputs are all it takes, “...basically look, think, and you’re turning- but I expect if you were really to yank the control stick you could roll this thing on a fairly tight axis. I have not tried any aerobatics and I don’t plan to.” The dihedral in the tips is not as great as it appears. there is an illusion that the wingtips are upswept even though the top of the wing is a straight line from root to tip. Sighting down the wing, it becomes evident that the wingtip dihedral is all in the bottom surface. David says that the only reason he the wingtips as he did was for aesthetic purposes; no particular aerodynamic reason. But I can’t help but to think that there is some benefit gained over the traditional alternative of bluntly terminating the wing at the tip.

This photo of Dave Thatcher’s prototype during Sun ‘n Fun 2009 clearly shows the straight line of the wing.


74, hence N74CX. Admittedly “kind of cheesy” as Bill put it, but also because he liked saying the abbreviated callsign Four Charley X-ray. With completed paperwork and a deal struck with a designated airworthiness representative (DAR) the inspection took place once the payment was made. Airworthiness certificate was issued that same day with no snag in the registration process at all.

This screen-shot of a video of Bill’s first flight shows exactly what he stated; the tail came off the ground in under six seconds with gentle acceleration. During take-off, the tail lifts almost immediately. Once ready for departure, Bill applies full power and immediately puts the control stick in a position slightly forward of neutral and the tail lifts within a few seconds. By simply holding it in that position until the airspeed indicator reads 60 mph on the air speed indicator, a slight release of pressure gets him airborne within about a 500 foot roll. For slow flight, with stall at 40 mph, Bill is very comfortable flying 60 all day long. “I’ve had no sluggishness in the controls in slow flight. Out over the Gulf of Mexico is where I did most of my 40 hours of Phase I testing, taking advantage of the nice smooth air over the water. It was very easy to hold altitude during slow flight and the controls continued to have complete authority. In the stalls, it’s very similar to how a Cessna product stalls in the sense that it’s more of a mush and a settle; you don’t have a surprise break and it doesn’t tend to drop a wing one way or the other.”

An exhaustive builders log with lots of detailed photos is credited for the ease with which the inspection was completed. If there was anything that the DAR wanted to see but couldn’t because it was covered or closed, Bill provided an acceptable photo.

PLANS $360 includes shipping for a comprehensive set of handdrawn plans complete with a color builders manual. Mr. Thatcher was kind enough to provide a complimentary set of plans to us for evaluation. I was a little surprised to see so many pages dedicated to such a small and simple plane, but since I’m a big fan of detail, they sure work for me. Each of the 15 photocopied 36” wide by 18” tall pages is packed with information, painstakingly handdrawn by David but noted mechanically. In almost every case where text (notes and dimensions, etc.) are required, it appears that David pasted computer-generated strips of paper to the original drawings. This makes for some very comprehensive reading.

In rough air, it’s comforting to know that the elevators and the rudder are mass-balanced.

NIGHT FLIGHT? Bill set up his CX4 for night flying and has it certificated that way as well. Although he’s not anticipating flying at night he does fly around an area in Pensacola where there’s a high volume of military training aircraft, so his desire was visibility. Selecting a combination navigation, position and strobe light system, Bill opted to use LED (light emitting diode) technology over incandescent. As an emerging technology it seems clear that LED for aircraft lighting is making incandescent a thing of the past.

THE PAPERWORK Certificating it with the FAA as the first customer-built version was actually straightforward. Bill reserved his N number as soon as he received his plans, serial number

Length– 18’-3” Wingspan– 24’-0” Height– 4’-8”




Wing Span






Wing Area

84.4 sqft

Empty Weight

520 lbs

Gross Weight

850 lbs

Useful Load

330 lbs

Wing Loading

10.7 lbs per sqft


9 Gallons

Fuel Type

92 Octane Auto


1700 cc-2180 cc VW

Electrical System

22a 12v— Alternator


Hydraulic Disc/Toe Brakes


All metal 6061-T6***

Design Load

4.5 Gs


Heater and Vent Performance**


125 mph @ 3000 rpm

Stall (Vso)

In addition to the well-written color building manual, Our set included two amended pages and one sheet of fullscale drawings of the turtle deck, windscreen and windscreen skirt. Support is best handled by way of the internet Yahoo group. Although I’m sure that Dave will answer any and all questions by phone, posting your issue or concern on the Yahoo group will usually net an almost real-time answer from someone who has already been there. Additionally, other members have posted photos and links to assist other builders.

A LITTLE ABOUT DAVID THATCHER SR. The thing that has always attracted David Thatcher to airplanes is their beauty and graceful lines. From the time he was a boy, he wanted to design and build an airplane incorporating all the elements he liked best. It also needed to be simple and economical to build and operate. A closed cockpit was important for year-round flying enjoyment, but with a removable canopy for open-cockpit flight. The cockpit needed to be big enough to handle a 6' plus person comfortably, so a wooden mockup of the cockpit was constructed first.

40 mph

Rate of Climb @ Vy

825 fpm @ 75 mph

Best Angle of Climb @ Vx

63 mph

Never Exceed Speed Vne

165 mph

Take-Off Roll

700 ft

Best Descent Speed

65 mph

Plans and manual printed in color

$360 includes shipping

Construction Time

Est. 850 hours

Cost of Materials


David’s credentials include being a graduate of EmbryRiddle School of Aeronautics for Aircraft Mechanics and continually active in general aviation for over 50 years, with countless hours of hands-on experience in sheet metal, welding, engine build-up, and all the other skills necessary to be an aircraft mechanic. Now that he’s retired, he found he had the time, space and most importantly, permission from his wife to build an airplane, one which might be well received by other homebuilders that do not have unlimited funding but share Dave’s dream.


 

A special thanks to David Thatcher, Bill Stinson, and Wilson (Will) Leonard for their help with this article. Will and His brother Phil built twin CX4s which will be featured in

Aircraft may be flown with canopy off Wings removable for transport in 20 minutes

Specifications are based on Mr. Thatcher's standard prototype **Performance is based on 750 lbs with a 1700 cc VW Engine ***Cowling and wing tips are made from fiberglass

Products available directly from Thatcher Canopy




Windscreen retainer


Canopy and windscreen bows with skirts


Canopy latch


Control stick with boot


Rudder pedals and assembly


Elevator horn Exhaust system Nylon bearing set

$85.00 $200.00 $21.00

an upcoming issue, perhaps even the next issue. For more info: Thatcher CX4 1020 E. Jordan St. Unit A Pensacola, Fl. 32503 Phone: (850) 712-4539


SWITCH ON! Continued from page 2

It will be a struggle for me from here on out, but I vow to handle it with the best of my abilitie and return to a more “regular” publication schedule.

ROTARY WING AIRCRAFT By design, we do not exclude rotary aircraft (helicopters and gyros) but if the pages seem void of such modes of experimental pleasure, it’s not our intent. If it leaves the ground and uses an “alternative engine”, or is unique in any way, it’s fair game for us. But remember, our magazine is subscriber-driven, so if we don’t get rotary-wing articles submitted to us, we can’t publish them. I personally subscribe to two publications dedicated to experimental rotorcraft. One is simply called Rotorcraft and the other is Experimental Helo (pronounced hee-low) As the name indicates, Experimental Helo is a bimonthly publication dedicated to those ships that have the engine hooked to the rotor, whereas Rotorcraft is the Popular Rotorcraft Association’s (PRA) bimonthly magazine that is free to its members and is dedicated to both autogiros (gyroplanes) and helicopters. Publishers of both of these magazines have been gracious enough to offer us the ability to reprint in CONTACT! Magazine, any article I deem appropriate. So look forward to seeing the occasional rotary-wing ship grace the pages. And if you know of or have a ship that belongs in our pages, please let me know. ADVERTISING In my previous editorial I asked for feedback on the idea of including innocuous advertising within the pages of CONTACT! Long story short, due to your feedback I’ve decided that it’s not in our best interest to include ads at this time. The following is just a smattering of replies. Bear in mind, the vast majority of those who replied to me are in favor, but those who objected had some very insightful reasoning that can’t be ignored. For the sake of space, the following are some of the comments I received that are in favor of advertising. I’ll print the ones who swayed my decision in the next issue. Pat, CONTACT! is my favorite magazine, and is the one magazine that I subscribe to that I will drop everything else to read it cover to cover when a new issue arrives. If limited advertising will help ensure the continued health of this magazine, then I am in favor of it. I certainly don't object to some advertising, because I will often go thru current and back issues of my magazines when I am looking for information and possible sources for a specific product or supplies. I value your ability to publish negative information about a product or design when it is warranted, and the advertising policy that you propose should ensure that that ability remains unhampered. Keep up the good work. Richard Gent Pat, I'm fine with non conflict of interest ads. I'd even be OK with a sort of resource listing of product sources, as long as it was clear to them that their ad does not dictate what the magazine says about them. For example a

ing of redrive manufacturers by automobile type and the HP of the converted engines and weights. (Followed by real world weights listed by subscribers so the manufacturer is not temped to deflate/cheat). And/or a listing of new products, but it can only be considered as "new" in 2 issues. Should Contact or a subscriber decide to test the product and post the results pro or con, it would come out after the brief listing had run. Example: the wind powered generator that GPAS now sells. As I don't normally check their website, I would not have known about it but I saw it in a Barnstormers ad. And because I plan to use a Suzuki G13BB engine with EFI, I need more power than the little device can produced to maintain my electrical needs. But, if it made minimal drag in normal use, and extended my alternator failure flight time from 15 minutes to 45 minutes, it might be worthwhile to me. Sort of a consumer reports for AC homebuilders to separate hype from reality. But that information is unknown to me. Unfortunately, so many claims by manufacturers are just wrong/inflated, knowing we base decisions on that data, but there is no one source to debunk that and keep them honest. I'm thinking of the EPA site where they list fuel mileage claims, but they take the real world input of consumers and post the average of that data. Gary Van Meter Gary, what you describe is exactly what CONTACT! has been doing since day one. The thing is, we don’t have the resources to check these things in-house, but we hope to be there one day. For now, we rely on our readers to supply us with the info on products, the pros and cons of the applications, etc. With little exception, we are the only magazine that reports on the good AND the bad of experimental aviation. ~Pat Hello Pat, I got my magazine a few days ago and as usual have read it from cover to cover on the first day. I love CONTACT! articles because they are about actual airplanes and engines. I like the magazine better than the EAA's. I don't have a problem with advertising and do enjoy seeing the ads for products and services. If it helps gets another page or two of articles about how-to on airplanes then it is a benefit to all. I have just finished reading the EAA's Experimenter with you as the editor. It had a good format. I liked the articles on the Flying Squirrel and the BD-4. I have the plans for the BD-4 that I had purchased in the Jim Bede book a few months ago. I have been reading and thinking about the BD-4 and wondering how hard it would be to convert to the LSA rules. I may have to get the Flying Squirrel plans next, just to keep learning about building techniques. Keep up the good work, with CONTACT! and EAA Experimenter, I will get to build a plane for myself someday soon. Best Regards, Kent Moore Thanks Kent, I don’t think the BD-4 will ever make it as an LSA as it’s just too heavy. With an advertised empty weight of 990 lbs, 50-100 of which you might be able to shave off with the use of the proper engine (Jab 3300?) it leaves you with a single-place aircraft at best, if you want to go somewhere, two small people if you only want a


splash of gas. For a single-place LSA, the Flying Squirrel looks like a hoot to build and fly. I’d advise going that way long before I’d advise trying to make an LSA compliant BD-4. It’s just too efficient an airplane to not want to put a big motor in and go real fast. ~Pat Hello Pat, Although I am not an advocate of converting auto engines for use in aircraft, as a faithful reader of CONTACT!, I have long admired the content of the magazine for communicating both the advantages and pitfalls of converting auto engines. It is a valuable instrument in furthering the state of the art. Unlike some other publications that usually portray the most rosy picture of “how I built”, but in reality, PAID someone to build, my $200,000 airplane, CONTACT! is really providing a valuable educational service to our community. I am sure that it is a challenge to get each volume into the mail. Thank you for your effort. Sincerely, Gerard Blake Gerard, it is indeed a challenge, more so now than ever before. My goal has always been to build CONTACT! to a point where we can hire a staff to take it to the next level, something I can’t do by myself. That was part of the reason for thinking that advertising could be an answer. My time is obviously best spent finding and publishing interesting articles, not necessarily finding and keeping subscribers– or even writing articles for that matter. There are people who can do these chores WAY better than I, but not many are willing to work for free. One thing that would help right off the bat is if our readers would renew their subscriptions without me having to send out reminders. This robs us of resources, both financial and manpower. ~Pat Dear Pat, You've outdone yourself again. I thoroughly enjoyed the most recent issue, and read it cover-to-cover (twice!) I am most interested in the Sadler Vampire and find the design intriguing. Of course (as you could probably guess, based on my flying background) I deplore the anemic performance to which LSAs are limited, but would really like to get my hands on a Piranha. I hope to read more about it in future issues of CONTACT! You requested feedback regarding accepting advertising, so here is some: Once upon a time, there was a magazine that detailed the vibrant experimental spirit that permeated the homebuilt-aircraft community. Within its pages, homebuilders showed off their latest accomplishments; they shared helpful tips and techniques; they published detailed instructions for building planes, modifying auto engines, etc. I refer, of course, to Sport Aviation, which has regrettably long since lost its touch with the hangar experimenter. CONTACT!, as I see it, fills the niche that Sport Aviation abandoned. Yours is the only magazine that covers experimental aviation. It is the only one that serves as a detailed exchange of technical ideas. It is the only one that has any substance regarding home-brewed powerplants. Sport Aviation, unfortunately, has degenerated into a pile of worthless platitudes about how fun it is to fly, and has ceded the field it once monopolized to whomever cared to pick up the pieces - in this case, Mick Myal and then Pat Panzera, through CONTACT!

zine. True, Sport Aviation accepts advertising, but we must remember that it always has. When it was a good magazine it accepted advertising, and it still does now that it is full of drivel. The advertising itself is neither here nor there; the difference between SA then and SA now is that its editors have lost their focus, their leadership, and their understanding of what the magazine was and should be. To be pithy, its editors do not edit! So how would advertising affect CONTACT! Magazine? It would not. CONTACT! will retain or lose its connection with the true homebuilding spirit based on the integrity of the leadership at the helm, not based on how the funds are raised. As long as you remain in charge, I have no doubt that it will continue to be an interesting read which provides a detailed exchange of technical ideas while at the same time maintaining a detached, critical eye through which to view new products. Ask yourself this, Pat: would you have refrained from printing anything about NSI's catastrophic prop failures simply because you had once printed an ad paid for by Lance Wheeler? The answer is, "of course not," and that is why I think you need not worry that the quality of your magazine will suffer if you accept advertising. I will make one timid suggestion if you do decide to accept advertising: though part of CONTACT!’s charm is in its folksy, homegrown spirit, that persona is...ahem...sometimes a bit more liberally spiced with misspellings and questionable grammar than a magazine hoping to attract advertising dollars might ideally be. For once I'm in a position to offer help: I will be happy to volunteer as a proofreader if you care to accept my services. Regardless of what you decide, expect me to be a subscriber for a long time. Keep up the good work, my friend! Respectfully, B.W. (Ben) Stone Thank you Ben, your offer to help is certainly welcomed and your attitude in doing so is possibly the answer to some of my issues. I do have several volunteers onboard with me and a few regular contributors whose help I could not do without. My proofers do a very good job in my opinion, as I see what they have to start with— my work!— fourth grade at best, and of course, always a last minute rush. I’m absolutely thrilled at the number of errors and omissions they catch and in the short time in which they do it. Having one more can’t hurt!

PRIVACY I recently received a note from a subscriber asking that we not share his personal information. We will NEVER! share any information we have on any of our readers, past or present. Any and all information we collect is for the purposes of serving you better, not for selling or distributing to others in any way. On occasion we’ll get inquiries on an author by people wishing to reach them and in those cases, we’ll usually pass their info along to the author or otherwise gain permission from the author before we proceed. I just want to assure all our readers that your information is, and will remain, private. Patrick Panzera


Phyllis Ridings Administrative Assistant to Bud Warren (936) 672-6639 The new firewall forward package by Geared Drives is shaking out nicely. Our customer and friend, Bill Gipson, has completed his Phase I flight tests with no engine related issues and he is all smiles these days. Performance exceeds projections. On take-off, applying power slowly until rudder authority kicks in is taking some getting used to. There is a lot of torque available to the prop, considerably more than the airplane was designed to handle. The official total empty weight of N730WL is 1727 lbs, which is 207 lbs heavier than the advertised empty weight of 1520 lbs. This includes 23 lbs of lead in the tail in order to keep the center of gravity in the acceptable range. Like most RV builders, Bill also has a lot of extras that Van’s does not factor in, such as a heater, additional instrumentation, etc. Odds are good that N730WL weighs about the same as the average tricked-out RV10. Either way, there is still 973 lbs useful load available for fuel and passengers when respecting the 2700 gross. Bill has not pushed the envelope yet, but Bud flew the first 10 hours in this plane and reports 3,500 rpm @ 24” mp nets 188 kts, burning 11.2 gph @ 5-6,000’. Reducing mp to 20” nets 159 kts burning 7.8-9 gph. A cruise climb at 20” mp and 3,500 rpm nets 2,500 fpm. Bud also warns that one can easily bust Vne at just about any altitude. He once found himself indicating 195 kts in the pattern. The plane should be good for 200 kts no problem, and if you need some serious economy, 159 kts can be maintained at 18” mp.

Larry had extensive time with an Eggenfellner engine and PSRU in his 9. Bud made three changes to the installation. 1) New PSRU. 2) Constant-speed prop and 3) replaced the two smaller radiators with one large one. Note that no changes were made to the cowl— the PSRU is a direct bolt-up swap. In addition to better performance from the ability to run a true constant-speed prop, the engine now runs cooler- never seeing temps over 180° where 250-270° was the norm previously. The new PSRU is not very attractive per se, but it is just a prototype. If Bud goes into production, a proprietary casting will be implemented. As with the prototype, the production unit will be a bolt-on assembly, designed with the homebuilder in mind. Thanks for your support and we look forward to meeting CONTACT! readers wherever we go. Phyllis Ridings

Bud has several projects going all at the same time. One such is a Glasair that had 400 hours on an IO-540. When Bud removed it intact and weighed it, the scales tipped 530 lbs! Another notable milestone is the success of the Subaru PSRU prototype. This is a double reduction drive with all of the same features as the original PSRU such as its own oil pump and filtration system, centrifugal clutch and flywheel assembly, and drive port for a prop governor. It can accommodate virtually any ratio you want and can be changed on a whim. Larry Perryman with his RV-9A made the trek from Conroe, TX to Lakeland, FL this past Sun ‘n Fun and the PSRU didn’t miss a beat. Larry also reports that he has doubled his climb rate and has picked up 25 MPH—all due to the use of the Hartzell constant-speed propeller.

The unassuming “box” does nothing more than support four gears, plumbing for the prop oil, and have the robustness to handle a heavy prop. Note too that the thrust line is maintained.


Classified ads– minimum $15 donation from subscribers. All ads must include a price. No commercial ads allowed. Ads will run for 3 consecutive issues or until sold. Must be renewed after the 3rd printing. CONTACT! Magazine reserves the right to refuse any ad. FOR SALE: Miscellaneous parts. One of our supporters donated the contents of his garage. Listed below is a smattering of what we have available, and the value we declared for his donation. No reasonable offer will be refused. Please contact Pat Panzera with your questions or offer. CONTACT! Magazine, 559-584-3306 Subaru 2.0 engine, extra head REDUCED MORE New Mazda A10 engine Brock master brake cylinders Vari-Eze Vari-Eze spinner SOLD! Dragonfly project, no engine Dragonfly project, no engine Dragonfly project, ready to taxi

$650 $600 $308 $150 $1,500 $5,000 $9,500

DONATE YOUR PLANE, PARTS OR PLANS: The first ever “for aviators by aviators” charity needs your support. Receive tax benefits for a charitable contribution, donating your plane or any of your surplus parts and/or materials. See page 22 of CONTACT! issue #72 or visit for information on our 501 (c)(3) charity. CONTACT! Magazine (559) 584-3306

For Sale: B0208/MFI-9 (Messerschmitt built) A unique recreation of the mini-coin Biafra Baby #BB905. Historically accurate and documented. New zero-time TMX IO-240. A highly maneuverable small ship for a small pilot. Registered Experimental/Exhibition warbird. New prop, paint, interior, instruments, wheels and brakes. NOT LSA qualified. Contact for brochure or go to for images under “current project.” Priced at $38k FL59 Ft. Myers FL. Partial or full trades for aircraft or vintage racecar considered. Don Black 107 For Sale: Instruments- Falcon GH-002 3 1/8" Vacuum Attitude Gyro ACS 10-22955 $250 * Airborne 1J7-1/D9-18-1 Filter ACS $25 * 4" Venturi ACS 15050 $35 (has fiberglass streamlined housing) These units have about 300 hours total.* CONTACT! Magazine (559) 584-3306 103 For Sale: Subaru EJ-22 Firewall Forward. 300 hours TT w/o any problems. Ross redrive, all electronics, engine mount and some spare Subaru parts included. See CONTACT! issues #6 and #8 for a full description of this engine as installed on a Dragonfly. $5,000 Ruidoso NM. Randy (575) 937-3586 102 For Sale: Two RV6 Motor mounts for 4.3L Chevrolet V-6. One tail dragger, one with nose wheel. $1,000 each. Ruidoso NM. Randy (575) 937-3586 102

Wanted: Tuned port fuel injection system for my Ford Windsor 351W (See CONTACT! issue 16) which would be fed by my McCulloch (Paxton) supercharger, with each cylinder's injector adjustable and all mixture leanable. For Sale: Prince P-tip propeller with Gates 2.67:1 PSRU and Polychain Kevlar belts, Used 40+ hours on O'Neill Magnum V8 “Pickup” with modified Ford 351W, with and without McCulloch (Paxton) supercharger, 260 to 380 HP. Spinner included. Engine not included. $800 For Sale: Torsional vib. damper, for Lyc O-320. $180 For Sale: Female molds for wingtips for NACA 4412 airfoil, 63" chord. $170. Terrence O'Neill 103

ALTERNATIVE ENGINES VOLUME 3 The third in the series from Mick Myal is available only through CONTACT! Magazine. See the back inside cover wrap of this issue for ordering info or visit For Sale: 3.8L Ford V6 with Blanton redrive, as pulled from an RV-6 shown on by searching for “V-6 airplane engine” (yellow plane). Includes three-blade Warp Drive prop, all manuals and engine instruments. $2,000.00 Buyer pays shipping from Benbrook TX. (817)692-6742 Richard 102

ALTERNATIVE ENGINES VOLUME 2 Once again available! See the back inside cover wrap of this issue for ordering info or visit For Sale: Glasair 1 TD kit. Fairly complete, unstarted kit with extras. $4500.00 Located in Hanford California. Please contact Pat Panzera with your questions or offer. CONTACT! Magazine, 559-584-3306 106 For Sale: Ross Redrive with aluminum flywheel. $1800.00 For Sale: Warp Drive Propeller threeblade, 66” diameter, left-hand rotation with nickel leading edges. Comes with spinner. $500.00 Or buy both for $2000 total. These components were bolted to a Subaru EA-81 and tested for a maximum of 30 minutes only. Buyer pays shipping from Las Vegas NV 89104. Don Thompson (702) 236-1691 106

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Issue #106

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