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March
2009
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Wayne Sprigle’s Mite-T-Mustang
By Wayne Sprigle, EAA 139982wsprigle81@woh.rr.com
Wayne’s Mite-T-Mustang began as a fixed-gear Taylor Titch. Although this photo shows a retractable-gear version of Wayne’s design, it now has fixed gear to meet light-sport aircraft definition.
Jim Miller’s Taylor Titch winning the Mechanix Illustrated Award for Outstanding Workmanship at Oshkosh 1972 was the first in a string of awards. The aircraft is seen here on the cover of the March 1974 issue of Sport Aviation.
There is a lot of detail in this photo, from the chin scoop to the updraft carburetor, the air box, the dual coils, MSD coil joiner, and the intake manifold, all of which are custom.
The PSRU is modified from a Taylor Bird. It has a 2-1 ratio and uses two triple V-belts.
On the exhaust side of the engine a “racing” four-into-one header is attached to the engine with a tail pipe, forming a 270-degree change in direction in order to locate six functioning stacks in the P-51 location for this side of the engine, but this will be changed for a more traditional system.
Working on rear spar attach fitting: The photo shows me dressing the rear spar to receive the bent spar attachment pieces that were formed in my press fixture. In the foreground is the aft portion of the landing gear fixture I designed for my retract system. Notice the bronze bushing in the center.
Preparing for wing center section attachment.
A view of the fixed-gear fixture as well as the pitot-static lines and electrical quick disconnect for the strobe lights, needed since the wings are removable.
Wayne working on his elegant but now obsolete mechanical retractable gear system.
Dallas-production P-51K-5-NT nicknamed Nooky Booky IV served with the 357th Fighter Group, 362nd Fighter Squadron and was piloted by Maj. Leonard “Kit” Carson, credited with 18.5 kills.
Wayne Sprigle of Springfield, Ohio, is recently retired from the 178th Fighter Wing of the Ohio Air National Guard. He reached the rank of Senior Master Sergeant and has always expressed a love affair with the North American P-51 Mustang. In the late 1970s he joined EAA and started looking for a Mustang project he could build from plans, and he found one - almost.
GETTING STARTED
When I decided it was time to build an experimental aircraft, I researched my options for building a scale P-51 Mustang and found that for my income level, the plans or kits available at the time were way out of my league. With more research and my ideas for modifying other designs, I found my solution. One company that stood out was W.A.R. Aircraft Replicas International Inc. of Brandon, Florida. Its offerings were nice, but I did not like the idea of working with that much fiberglass, so my search took me across the pond. I’m a woodworking type and found plans for a wood and fabric Taylor Titch. I selected it because it had the wing planform I needed and the rudder seemed to be easy to change. For those not familiar with the Taylor Titch, it is a plywood stressed-skin structure. The fuselage has curved sides (not flat) and is very strong, resisting torsional loads very well.
MODIFICATIONS
Whoever made the statement “For every change you make, you need seven more to accommodate it” was right. My aircraft is so different from the Titch, the only things that are still Titch are the ailerons, flaps, and horizontal stabilator/elevator. But, my advice to anyone who would want to build a replica fighter by modifying an existing design is don’t. With the changes I have made, I have constructed an awful lot of the smaller parts and assemblies two to five times (not cost-effective).
At this point, my plane is so far removed from what the plans specify, I can’t even call it a modified Taylor Titch, so it is now known as the Mite-T-Mustang. It’s just slightly over half the scale of a full-sized Mustang at 18 feet long with a 21-foot wingspan (including tips). This aircraft (or even the “stock” Titch for that matter) is not for the large person as the cockpit is only 19 inches across the shoulders. You wear the airplane! I don’t think it’s suited for cross-country flying, but it should be fun to bomb around in. The structure is rated +/-9G’s. Now if I can just figure how to get a parachute in this thing…
Here are some of the modifications I made to create the Mite-T-Mustang:
- Widened the firewall to fully enclose the inline water-cooled engine (hence the narrow cockpit).
- Moved the main landing gear out for a 7-foot stance (to allow for originally designed retract).
- Relocated the tail wheel to in front of the horizontal stabilizer, more of a P-51 look.
- Lowered the turtledeck to allow for a two-thirds P-51D canopy from the Airplane Factory.
- Increased the wingspan from 18 feet 6 inches to 21 feet.
- Repositioned the engine due to weight difference of Continental to the Honda Civic engine.
- Designed and installed the cooling system to function in the proper location.
During the course of creating my modifications I have become friends with fellow Titch builder Jim Miller, EAA 6110.
With the information Jim gave me regarding errors and omissions contained in the plans, I feel I will have a safe aircraft so I want to make sure to credit him for that, and I also want to mention that Jim is the 2006 recipient of EAA’s Tony Bingelis Award, where he has been recognized for his involvement as an active volunteer, technical counselor, and aircraft builder. His Titch has won numerous awards since 1972 and is one of only a few aircraft that have been featured on both the front and back covers of EAA Sport Aviation.
I have been working on the Mite-T-Mustang since 1980 with an eight-year hiatus due to another hobby with my horse (I know, I know, horses and airplanes don’t mix).
ENGINE, PROP, and PSRU
My 67-inch diameter, four-blade, ground-adjustable propeller is made by Precision Propeller. I chose this prop for its form over function, and I hope it pays off. I think that a prop not in scale makes the replica look funny (nothing personal to any kit manufacturers). I am not looking for all-out speed as I’m more interested in the look and functionality, but more importantly, I want to fly in the light-sport aircraft category. The prop is rated at 70 hp. My composite spinner was hand made by an airframe and powerplant mechanic. I bought two of them at auction for $5 each.
The upper and lower propeller speed reduction unit (PSRU) pulleys came from C.G.Taylor. His son, Robert Taylor, gave me a set for all the work done for him as a close friend of the family. He also gave me a set of plans for the PSRU from the Taylor Bird aircraft, which I was helping make kits for before they closed the business. I modified the PSRU mount to fit my application, and I’m very pleased with all of it.
My engine is from a 1974 Honda Civic, an EB2 series, with 1234 cc. According to the maintenance manual it produces 55 hp and 70 foot-pounds of torque at 5500 rpm. The torque curve is flat coming in full at around 3000 rpm, and remains there until about 6000. The timing advance comes in full also around 3000 rpm. My 2-to-1 reduction will give 140 foot-pounds at the prop, but due to my PSRU not being a cog belt, I will have some losses, potentially as high as 20 percent in my estimation.
I chose this engine because back in the late 1970s and early 1980s, Geo or Suzuki engines were not being used like they are today, at least to my recollection. I wanted an engine that I could fully enclose in the cowling (without cheeks) and be water-cooled. During my research, the BD-5 was using this engine, and it proved to be reliable. Also around the same time frame Homebuilt Aircraft magazine was doing an article series on a Honda Prelude engine for W.A.R. Replica’s 1/2 size P-51. I felt that the Prelude engine was too large and heavy for my airframe. My Honda Civic with PSRU, alternator, starter, air box, carburetor, tuned exhaust, and racing intake weighs approximately 175 pounds, whereas the Prelude came in at more than 200 without the PSRU.
My Civic engine is all-aluminum, and the main bearings are an assembly like the Cosworth racing engine. When I found out that my model engine was used in racing applications with rpm in the 12,000 range and lasted for a whole season, I felt that 5500 rpm was loafing, so it would be a good choice. I purchased a crate engine from Japan for $500 and then bought a car with the same engine that was overheated. I removed the engine and use it for jigging systems before I installed the crate engine. By the way, after I removed the junk engine, I sold the car for what I paid for it.
The first issue to overcome was the carburetor; I could not use it because it was on top of the engine, which would have made it taller than the cowling. I contacted a speed shop in Connecticut and purchased a racing manifold that used two side-draft carburetors; I also purchased a tuned exhaust header from this same source. Since I did not plan to do any internal modifications, I felt this would be my best bet to optimize available horsepower. But I digress—it ended up that I couldn’t use side-draft carburetors because, again, cowling issues came up, so I made a two-into-one adapter that allowed me to use an updraft carburetor and mount it behind the engine on top of the air box. The air box is made to emulate the intake on the real P-51 in that it has filtered ram air in addition to provisions for carb heat, with surplus airflow being routed to cool the ignition coils and the alternator. The intake (chin scoop) also will have an air outlet to cool the PSRU belt.
Knowing that I didn’t want to over-spin my alternator, I designed and turned a billet crankshaft pulley. The reduction in rpm should do well for my alternator bearings, not to mention the same type of issues with the water pump including cavitation.
The ignition system is copied from William Wynne, the “Corvair Authority.” It consists of a set of dual points in the distributor and two coils coupled together with an MSD coil joiner. I was going to try to make my own dual point mounting plate for the distributor, but a friend at AutoZone told me about the six-cylinder Datsun 240Z engine having stock dual points, and it was interchangeable with the Honda. So we ordered it, and all I have to do now is replace the six-lobe shaft with the four-lobe shaft and I will be golden.
COOLING SYSTEM and EXHAUST
The coolant tank is mounted in the same location as the P-51, between the prop and engine. (See photo.) I fabricated the aluminum pieces and had them welded by a friend. This is also the highest point in the coolant system so I incorporated the filler and cap.
Although I already have an exhaust system that will closely emulate the real thing (on one side anyhow), I’m going to change all this. I will be making a dummy exhaust that will mount to the cowling permanently and will have all tubes open to the engine compartment to allow heat to escape. The actual exhaust will be routed in a more traditional style.
I’m in the process of forming a composite belly scoop. The foam forms the internal plenum to the radiator as per articles I’ve read in CONTACT! magazine. The back half of the scoop also has an adjustable door for regulating coolant temperature (in conjunction with the engine’s thermostat). I plan to make the scoop removable for maintenance and inspection. My coolant lines will be run outside of the fuselage. I’m not pleased with that configuration from an aesthetic standpoint, but at least I won’t get scalded if a leak ever happens.
The radiator is made from 1986 Chevy Caprice air conditioner evaporator. I followed a recommendation in an article I read in CONTACT! magazine. According to the math, this should be large enough for an engine about twice my displacement.
CONSTRUCTION
As previously mentioned, the plane is built from wood and fabric, but mostly wood, with the fuselage (including the integral vertical stabilizer) and the center section using a monocoque, stressed-skin type of construction. The wing and center section are built using the traditional construction technique of a wood rib, but while one side has the typical triangular gussets at each joint, the other side is overlaid with a single sheet of plywood.
PROFESSIONAL HELP
Some might say that anyone who builds a plane, especially with the intent to power it with a car engine, needs professional help, but that’s not exactly what I mean here. I have had professionals assist me with verifying numbers for the appropriate changes I made. I jokingly use the phrase “Made to TLAR standards with engineering backup.” (For those of you who don’t know, TLAR stands for “that looks about right.”) Now that I have described my project and how I went about doing it, I’d like to reiterate that I do not recommend anyone without an engineering background or at least professional assistance do what I have done. At this point in time I have about $16,000 invested. My motto is, “If I can’t buy it, I will make it.” I am a great scrounger. The project just shows that it can be done.
My instrument panel has the usual gauges for a liquid-cooled panel. The circuit breaker panel will be changed so I can replace the fuel transfer switches to make room for an air/fuel stoichiometric gauge and replace the fuel gauge with a fuel pressure gauge since I have two electric fuel pumps. I changed my mind on wing drop tanks for fuel as my engine only burns about 4 gallons per hour and my main tank holds 9 gallons. Bladder control dictates flying time and duration.
The photo shows the obvious throttle quadrant including mixture control. Directly behind the quadrant is my elevator trim control, operated by a twist knob (in the leading edge of the mechanism) mounted to a lead screw that changes the rotary motion of twisting the knob into a push-pull linear action on the cable exiting out of the rear of the device. There is a similar cable actuator located just below the trim control that is used for the coolant exhaust door; it’s operated by loosening the friction knob and sliding forward to close and rearward to open, or of course, anywhere in between. Both of these controls were made by me on my mini mill.
In a few of the photos throughout this article you will see that my plane is configured as a retractable. I spent eight years designing and building the system to work flawlessly, but then the light-sport aircraft category was finalized, and it doesn’t allow for repositionable gear (except for amphibious aircraft). It’s now configured with fixed gear; I just don’t have many photos showing it that way. I have been working on the project for 23 years now with an eight-year hiatus for my interest with eventing horses. That is now behind me, and I am working on the project daily. If work continues at the current pace, I might have it flying in late 2009.
My Estimated Performance Specs:
Cruise: 135 mph at sea level conditions
Stall: 48 mph (without flaps)
Max continuous engine rpm: 4200-5500 takeoff
Length: 18 feet
Span: 21 feet
WARBIRD
As I am retired from the Air National Guard, my former commander and I discussed my aircraft and the possibility to do something special for our unit. Since we do not have an example (on a pedestal) of our first aircraft, the P-51, I have decided to dedicate my aircraft as a flying example. I plan to paint it gray with the stars and bars of the 50s and commemorate the aircraft with the serial number of Maj. Kit Carson from the Yoxford Boys of World War II.
Note: My unit is the current Yoxford Boys (of which I was part for 22 years). The main change to the paint scheme is to not call it Nooky Booky II (Kit’s plane was the original Nooky Booky), but to name it The Yoxford Boy because Kit Carson was the original Yoxford Boy and he was the squadron commander of the 362nd Fighter Squadron, and I am the current Yoxford Boy with the 162nd Fighter Squadron as being part of the 178th Fighter Wing. The designation changed from the 362 to the 162 shortly after WWII.
My N number also commemorates the 178th Fighter Wing, my retirement squadron number, N178FW.
ONE LAST NOTE
I am a member of the Replica Fighters Association. This is a group of people who promote building and flying replica fighter aircraft, bombers included. Our newsletter editor has designed, built, and flown a replica bomber called a Voison of World War I vintage. We also have numerous scale fighters of the P-51 single-seat and tandem, as well as P-47, FW-190, and Spitfire to name a few. Of WWI aircraft we have Fokker D-VIII; of WWII there is an L-19 and others. The group is filled with a vast number of members with knowledge on all types of construction such as electrical wiring, woodworking, composites, and metal.
We have our own building near the flightline at AirVenture and also host several forums. As of this writing the forums for 2009 are not scheduled yet, but I’m sure they will be listed at the Replica Fighters Association’s clubhouse. Please stop in; we are a friendly group. As with any organization, we would love to have you join our group and get the word out about this great club. Besides, we have a great newsletter and magazine printed quarterly.
The Replica Fighters Association also has a presence at Sun ’n Fun as well as Arlington and COPPERSTATE.
Contact information for our group:
Replica Fighters Association
1528 S. Koeller, Box 111
Oshkosh, WI 54901-6167
http://ReplicaFighter.org/wp
Or, if you plan to attend AirVenture, visit with us and admire the replica aircraft parked in our little section. Every aircraft on display is a show of dedication and a huge sense of pride in what our members built.
