Cox Medallion .051 NFFS Special
| Beginning Free Flight Power - A Journey, written by Don DeLoach. (Site owner's comment: Don's experiences here are pretty much on track with my own. Questions can be directed to him at ddeloach@comcast.net). Noise. Speed. Altitude. Grace. Those four words say it all about the cult of gas free flight (FF). Watching a model go from 0 to 50 MPH in less than two seconds is a sight to behold. It is something the rubber or glider flyer can simply never experience with their kinder, gentler models. As a longtime rubber flyer I always watched the gas guys and secretly wanted to join them. For a long time I perceived it as being too complex. When I decided to finally try a power model for the first time in early 2003 I made up my mind that I was going to pick the brains of experts instead of trying to reinvent the wheel. I found the experts to be very forthcoming with their advice, and perusing back issues of National Free Flight Society (NFFS) Digest, Model Aviation, and NFFS Symposiums also helped me along. What follows is a narrative of my experience in this fascinating segment of our hobby. From construction to trimming to contest flying I’ve experienced a lot in the last year, and most of the experiences have been good. The purpose of this article is to convince you that learning to fly FF power isn’t as hard as you might think. Anyone with the willingness and patience to learn can be successful in a reasonable amount of time. Scope The article focuses on the construction and flying of the “classic” fixed geometry pylon designs that were popular in plan and kit form during the 1960s, ‘70s and ‘80s. These were mostly balsa, with a smattering of spruce and fiberglass. Of course, high thrustline (HTL) designs were also prevalent during the classic period. Construction techniques and engines for these models are the same but trimming a HTL model is radically different from pylon ships. That information is not contained in this article so consult your local HTL expert for guidance. Basics of FF Power All free flight gas engine models are not created equal. That is to say a relatively underpowered sport model that putts around for 20 seconds before the engine quits is not what this article is about. Real power flying—including AMA Gas, Classic Gas, and F1C/J is a vertical drag race. The objective is to get the model as high as possible in the allotted engine run time. Altitude is basically a function of available power vs. weight and drag. So sizing the model for the engine size is of utmost importance. The hottest .15—a Nelson—on an oversized airframe is going to result in a model that may not get high enough to be competitive. On the other hand just an average engine matched to an ideal sized airframe will be a lot more competitive than you think. So the lesson is to spend time selecting the right size airframe for your engine, not building a model and slapping an engine on afterwards. This is a significant change in philosophy from the rubber classes where you can add or subtract a couple of strands to optimize your power. Engine Choice The kind of engines we are after as free flighters are special. They aren’t the typical sport flying motors you find in modern hobby shops. They have no carburetors or mufflers. They are typically “Schneurle” ported—the most advanced exhaust porting available resulting in maximum power. The best FF engines achieve high RPM, are consistent, and are light. Many of the engines in common use for free flight today are no longer in production. But this doesn’t necessarily mean they are hard to find or expensive. For example, one of the hottest .21s going is also one of the most common and inexpensive, the 1970s vintage K&B 3.5 (.21). On the other hand a Rossi .21 may cost three or four times as much because it is a lot more scarce. t is important to re-emphasize that you don’t need Nelsons or Cyclons to be competitive. An older, cheaper, yet good performing engine perfectly matched to the right sized model will be competitive. Conversely, putting a super-hot engine on an airframe that is too small for it could spell disaster. Don’t start building anything until you’ve decided on the right sized airframe for your chosen engine. See table 1 for a rundown of common FF engines with approximate values and airframe size recommendations. Design Choices There are plenty of proven FF power designs to choose from. See table 2 for parameters of some of the best designs. The classic Pearls and Satellites are still great choices. And there are a few modern designs that are traditionally constructed while using the hottest engines available. Two of the best are the Marval for A/B and the Killerbee for B/C/D. Both were NFFS Model-of-the-Year selections, in 1993 and 2003 respectively. Other proven pylon designs include the Orbiteer, Maverick, Manito, MexiBoy, Shocer, Air Express, Texan, Simplex and Geodetic Galaxie. This is just a partial list. If a power flyer near you has a favorite design that is a consistent winner by all means build it. The Pilfered Pearl is a favorite of my Texas friends so it was my trainer. NFFS plans is a great source for most of the classics, and check the NFFS Symposium archive CD for old model of the year selections. And though is hard to find hobby shops that still stock FF power kits, suppliers like Lee Campbell, Lin Cochran, FAI Supply, and BMJR keep selling kits via mail order. Airfoils This is a major design consideration for fast power models. With such a broad speed range the airfoil has to do it all. If you select too thick an airfoil, your model won’t get high enough. If you select too thin an airfoil, the wing of your model won’t be strong enough and could fail under power or from the G-forces sustained at impact with the ground after DT landing. Undercamber gives a better glide but it slows the climb and makes trimming more difficult. It is a balancing act. As a general rule flat-bottomed airfoils are preferred for power models. They are fast under power and glide well enough to be competitive. Derivatives of the Clark Y or NACA N9 are tough to beat. A little leading edge upsweep is good idea to soften the stall and make the model more stable in wind. The range of thicknesses for a typical fast power model wing is 8-11%. Horizontal stab airfoils should be 1-2% thinner than the wing to make sure the stab doesn’t lift too much. This would result in the model going over the top (the beginnings of an outside loop) under power. Some guys use a little leading edge upsweep or semi-symmetrical sections on the stab to ensure the over-the-top phenomenon doesn’t occur. A good wing thickness is 9.5%, paired with a 7.5% thick stab foil. The combination has given me good results in models with moderate to hot engines. Construction Construction of a FF power model is far different from rubber ships and gliders. This is where as a long time rubber and indoor flier I really got an education. There are four load forces that we must understand and build for. The first is compression. The top spars of both the wing and the stab are under compression during the power phase because they are bearing an aerodynamic load from underneath. Another example of compression is when the model hits the ground after DT. In this case the bottom spars of the wing and stab are under compression.Tension is the force that the bottom spars undergo during the high speed power phase and the top spars undergo upon DT landing. The third force—shear—is thwarted by the use of balsa webs between the top and bottom spars of the wing and stab, especially important toward the center of each. These webs keep the spars from collapsing vertically under extreme bending loads. Most designers agree that the webs should be installed with the grain running vertically. The last and arguably the most important force we have to contend with is torsion. This is the tendency of the wing and stab to twist when air is moving across them. Torsion at high speed can result in flutter, an all too common sight at the average contest where fast power models are being flown. I have seen many a wing flutter and then quickly disintegrate under the stress of a high speed climb. It is crucial for the prospective builder of FF power models to understand and effectively build to resist torsion. Dealing with Torsion The faster a model flies the more torsion-resistant its wing and stab must be. For slower flying models like Nostalgia flimsier structures will often suffice. But we need our high speed wings and stabs to be much more twist resistant. And the majority of this resistance must be built into the structure itself, since plastic coverings like Monokote and mylar add little if any skin strength. Other options to consider are the more traditional coverings like tissue and polyester paper which do offer skin strength when shrunken and doped. But these coverings have their drawbacks. Both tissue and polyester require fuel proofing which adds weight. Japanese tissue does offer excellent stiffness under normal conditions but it slackens under humid conditions making flying in the early morning or in a drizzle a hazardous prospect. Polyester paper offers good puncture resistance while Japanese tissue does not. Generally with the advanced construction techniques available and the many easy to apply fuel proof covering choices, I wouldn’t opt for Japanese tissue anymore except for 1/2A models. There are several ways to build torsional strength into a flying surface. The most common method is the geodetic or union jack rib method. Ribs are placed at 30 to 45 degree angles to the LE and TE along with regular ribs parallel with the airflow. This a time-tested method which results in reasonably lightweight structures that are strong enough for all but the hottest engines. A second method is the balsa D-box which is torsionally stronger than the union jack but also a bit heavier. It is important to note that a D-box is usually necessary on wings greater than 8:1 aspect ratio and on models with very hot engines. The strongest method is the balsa D-box/union jack hybrid. Unfortunately this method is also the heaviest. But it is often necessary for making structures survive the rigors of the hottest engines. Fuselage Construction I have found balsa fuselages to be perfectly adequate for these models. The main consideration is building them dead straight, which is harder than it seems. 36” and 48” strips of angle iron are very helpful in assuring straightness while the glue dries. These are readily available at hardware stores for only a few dollars. Weak spots in a fuselage are typically the areas directly behind the pylon and in front of the stab leading edge. Build extra strength in these areas by using light glass cloth, plywood doublers, and/or carbon strips. Use a slow curing no shrinking glue for framing the fuselage. Titebond or epoxy are both good choices. I have had good results reinforcing my balsa box fuselages with a light coat of epoxy over .75 ounce/sq. ft glass cloth from the nose area back to about the halfway point of the tail boom. Glues For general construction aliphatic wood glue or CA is adequate. For high stress areas like dihedral joints, and securing the stab mount, pylon, wing saddle, and firewall a good quality slow cure epoxy like West Systems is a must. Firewalls This is a topic of utmost importance, for obvious safety reasons. I had heard horror stories of poorly-secured firewalls breaking loose with the engine running. This was not something I wanted to experience first hand so I learned how to do it right. The firewall should be made of high quality 5 layer plywood, with blind nuts for the engine mount. Glue the blind nuts on before securing the mount to the fuselage. Prepare the fuselage by gluing on the cowl cheeks and then sanding in the desired thrust angles. (0 or 1 degree down, 3 degrees left thrust is a good starting place for locked down pylon ships). Use a toothpick to dab some Vaseline or other thick grease into the backs of the blind nuts. Now use slow cure epoxy such as West Systems to attach the firewall to the fuselage. After it dries overnight drill a few 1/8” holes at random angles through the firewall and into the nose cavity as deep as possible. Now cram the holes with epoxy and 1/8” hardwood dowels cutting them flush with the front surface of the firewall. Next cut some strips of 2 ounce fiberglass and lay them up with epoxy from the firewall back down the sides of the fuselage for a couple of inches. Before doing this you may wish to carve out a groove with your Dremel tool for the wire landing skid . A nice final touch for the firewall and cowl is to use Jim O’Reilly’s penny balloon finishing method. Simply blow up a balloon and press it into the front of the firewall. Slowly let the air out of the balloon as you continue to press, inverting the balloon over the cowl area. Try to get the balloon as far back as possible, compressing all of the wet epoxy layup. Let dry overnight, cut off the balloon, and you have a perfectly molded front end. Fuel Proofing Since we will be using high nitro fuels in these models, butyrate dope is not an adequate fuelproofer. I have used DuPont Nason automotive clear coat with good results. It is a two part finish that brushes or sprays easily and is fairly light. Another option is K&B Ultrapoxy which is available in lots of colors. I have also used West Systems epoxy by itself on the front half of the fuselage and a light iron-on covering like Ultrafilm Lite for the tailboom. Make sure the entire fuselage, wing mount, wing center section, stab and rudder are fuel proofed. Covering As mentioned previously, fuelproof iron-on coverings like Monokote, Ultrafilm, Micafilm, and mylar offer a host of advantages to the builder. They are relatively tough, colorful, and easy to apply. Not having to brush or spray on fuel proofing on the flying surfaces really cuts down on the weight. Ultrafilm Lite and SoLite are excellent materials that are about half the weight of regular Monokote. They are great for stabs and smaller model like 1/2As. They have the adhesive already on the back just like regular iron on films so they are a snap to use, though a tad heavier than bare mylar. All of these plastics result in an airtight structure so you must poke tiny vent holes in every rib bay on the underside. This is for those sunny, hot days when the surfaces could expand and warp if they are not allowed to breathe. Built-in Trim Settings There is only one safe way to fly locked-down pylon models—to the right under power. There are aerodynamic forces in control involving prop wash on the left side of the pylon. This prop wash is so pronounced that we actually must some LEFT thrust to counteract it at the beginning while the model is accelerating out of this vulnerable condition. Surprisingly these models are very predictable and easy to trim if you build in safe trim settings from the beginning. The three settings I recommend are 1) Washin on the right main panel. 2) Stab tilt for 25-50 second glide circle (either right or left is fine). 3) The aforementioned 3 degrees of left thrust, 0 or 1 degree down thrust. This assumes that there are absolutely no other warps in stab, rudder, wing, or pylon, except for a tiny amount of washout in the wing tips if you so desire. This also assumes that your model CGs at the recommended location and that you have about 2.5 degrees of decalage before the first flight.Typically this decalage will be about 0.5 or 1.0 degree more than you need. But it is better to start with too much than too little. The amount of right main washin varies for the different sizes of wings. For 1/2A 3/32-1/8” at the outer dihedral break is usually enough. For A/B about 1/8-3/16” is needed. C/D requires appx 3/16-1/4” and Super D needs about 1/4-3/8”. By following these recommendations it is amazing how quickly a locked down pylon model will trim out to near perfection in course of 4-8 flights. And in the majority of cases all you will ever need to change is incidence, CG and rudder. Initial thrust settings are typically never tweaked because they are so ineffective at high speeds. More on trimming later. Engine Mounts A lot of flyers use the lightweight glass-filled beam mounts that are so commonly seen at hobby shops today. But I’ve been told by the experts that these are unsafe for our high-revving engines. I’ve followed the lead of these experts and fashioned my own mounts out of 1/8” or 1/4” sheet aircraft aluminum (see figure 1). These are cut out by hand with hacksaw then final shaping is done on a tabletop disk sander. The backplate bolts on the engine are removed and replaced by identical bolts that are at least 1/8” longer. Blue Locktite on the bolts helps them stay put. Use black alloy steel cap screws to secure the engine to the firewall. 2-56s are adequate for .049 to .061 engines. Use 4-40s for .15s up to .45s. For 60’s and larger you should use 6-32s. Timers The only brand of timer I have used in my short career of power flying is the Texas Timer. I’ve used the Max III, IIIA, and 6-gram Micro pinch off. The later is good for 1/2A models because of its light weight (6 grams). But it doesn’t have a DT scroll, only a pinchoff, so you must use a fuse or other timer for DT. It is possible to loop a DT line (under light tension) on the scroll to rig it for quick DT (see Schwartzman, 2001). For most applications The Max series are ideal because they provide fuel shutoff and DT in one unit, eliminating the need for fuses and making accurate DT times possible. The IIIA has an integrated pinchoff while the III requires a remote pinchoff. Either one works great for locked down power models. The Max III and IIIA have a max DT time of three-plus minutes making them perfect for Category II and III contests. For Cat. I the Max I and Max IA are the ones to choose as they run in excess of five minutes. But users of the Max III and IIIA can be prepared for longer Cat I maxes by rigging a backup fuse DT system.I had been told that mechanical timers were prone to failure or damage from engine vibration if not mounted properly. But in over a year of flying with seven different models I have never had a Texas Timer malfunction. Many other flyers have confirmed this with their own experiences. The old KSBs and Seeligs seemed to have more problems with engine vibration than these newer Texas units do. So use what you feel comfortable with but I have found Texas Timers to be top quality units that are reliable, accurate, and durable. Fuel Systems The vast majority of competition power flyers use pressure feed fuel systems these days. You can use crankcase pressure or pacifier/bladder pressure. I have had very good luck with bladder pressure tanks made from thin wall latex tubing. Texas Timers, Larry Davidson, and Doug Galbreath all sell this type of tubing. Texas Timers also sells a one way check valve for refilling, an inline fuel clamp, and a plastic coupler that mates the tank to the fuel line. Additionally I have found their thin wall silicone fuel line to be excellent and long lasting. I have built little fuel boxes right behind the firewall on my last few models with good results. This keeps the latex tanks out of the sunlight, which makes them last several times longer—two or three contests usually. It also protects the tanks from hanging down and getting pierced by cactus and other flying field hazards upon landing. Some guys put little tank doors that are rubber-banded on, for further protection from the elements. Fuel Two cycle model engine fuel is made of three primary ingredients: methanol, lubricating oil (castor or synthetic), and nitromethane. The brand of fuel you choose is not nearly as important as the percentages of the various ingredients. As a general rule use fuel with at least 20% oil. At least some castor is a good idea for prolonging engine life, though high quality synthetic oils like Klotz offer a tad better performance. The remaining 80% is some mix of methanol and nitromethane, and the greater the percentage of nitro the greater the power. Typically for AMA gas we use 30-70% nitro content. Good fuel brands seen often on the FF field are Powermaster, Wildcat, Omega, and Red Max/FHS Supply. The latter has custom mixing available on every gallon you order. Just call them up and tell them exactly the brew you want. They’ll mix it and ship it to you in 4 one quart bottles. I highly recommend them. Glow Plugs, Props I have had very good results with Fireball plugs in the “Super Cool” heat range which is best for high nitromethane fuels. They are inexpensive, perform well, and are as durable as any I have tested. Other modelers choose the more expensive O.S. or K&B 1L/1S plugs. These all fit the standard thread of model engine heads and are readily available and come in either short or long reach. Consult your engine’s manufacturer to find out whether your engine accepts a short - or long-reach plug. The other size of model glow plug is the Nelson. Many of the newer engines and some aftermarket custom heads (VA, AME and TD. 049) are tapped for this larger size of plug. Unlike standard plugs, Nelsons don’t use a washer and are only made in one length. Whichever size or style plug your engines use, have plenty of extras in your field box. In contest conditions with very high RPM on high nitro fuels you should not expect more than a handful of flights per plug.Props are a major performance consideration as well as being a potential safety hazard. Modern engines turning in excess of 20,000 RPM require props that were engineered for such velocities. Forget about digging out brittle old props and trying to use them with hot engines. If you do this you may be digging bits of prop out of your face or torso when one of these props sheds a blade. APC props by Landing Products are the standard for safety and performance these days. The FF props by APC range from only $1.83 to $3.95 apiece. The following is a list of recommended APC props for the various engine sizes: Table 3: Recommended APC prop sizes. Displacement APC prop diameter x pitch .049/.051 6x2, 6x3, 5.7x3, 5.5x2.5, 5.5x2, 5x3 .061 6x3, 6x2 .09/.10 6.5x2.9, 7x3 .15 7x3, 7x4.19/.21/.23/.25 7.625x3.25, 7.8x4, 8x4, 8x3.75, 8x3.75W .29/.32 9x4; 8.625x3.75, 9x5, 9.5x4.5, 9.625x3.75 .36/.40/.41/.45 9.5x4.5, 10x4, 10.5x4.5.60/.61/.65 11x4, 11x5,11.5x4, 12x4 Support equipment You will need a starter box with electric starter (Sullivan is the best-$50), sealed 12 volt battery ($10), and power panel with a glow plug clip ($25). Other recommend field tools are an adjustable wrench, a four-way glow plug wrench, a set of hex head ball drivers. All the preceding can be bought from your local hobby shop or mail order shop like Tower Hobbies. The battery comes with a trickle charger that you should plug in after every 1 or 2 flying sessions. Build a plywood field box and attach your starter to it with a removable foot switch. This enables you engage the starter with your foot while standing safely behind the prop and holding the model with both hands. Get a 2 ounce disposable syringe from a veterinary supply store for fuelling ($2). Practice starting and needling your engine on several outings before attempting your first flight. Get comfortable with engine, and get in the habit of always standing outside of the prop arc while the engine is running. Surviving the First Flight “A fool learns from his own mistakes. A wise man learns from the mistakes of others.” –Otto von Bismarck Think about it. You wouldn’t teach yourself to walk a tightrope. You would enlist the help of an expert and proceed with caution. Back to free flight: DO NOT attempt to fly your model until you have an expert FF power flyer standing beside you. This person will inspect the model making sure everything is A-OK before giving you clearance for the maiden flight.Many a flyer has shredded their first power model because something wasn’t right and they didn’t know better. Don’t sacrifice your model by repeating this mistake! Moreover, don’t even think about taking an untested model to a crowded contest without getting a sanity check from an expert. These are not harmless rubber models. In inexperienced hands they are truly hazardous. The oft-repeated safety mantra for full scale aviation also applies to free flight power flying: “Aviation in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.” –A.G. Lamplugh Trimming The most important aspect to trimming at the beginning is to have a timer with quick DT capability. This is so that if the model gets out of shape and is heading for terra firma the timer will release the stab just in time to prevent a crash. For the first flight set the engine run timer for two seconds and the DT for five seconds. Start the engine and needle it on the rich side of peak RPM with the prop on forward. Let go of the model in a steep angle, about 70-80 degrees, well to the right of the wind (NEVER launch straight into the wind) and with the right wingtip down about ten degrees (see figure 5). The model should climb at a steep angle to the right with no tendency to dip the right wing. The power pattern we are after is a slow right turn simultaneous with a slow left roll. If you observe the model in a tight sideways loop on the way up, slowly begin to crank out incidence until you achieve the desired vertical roll/turn. If the model goes straight up and rolls left without turning right you need to start cranking in tiny bits of right rudder. Do so very gradually as rudder effect is most pronounced at high speed. And be aware that incidence changes also affect the turning/rolling tendencies. Generally, every little bit of incidence you remove results in less right turn. Proceed slowly with 1/4 to 1/2 screw turns on successive quick DT flights inching to up to full run 1 second at a time. Once you’ve got the power pattern and transition looking good on a full run it is time to stop using the quick DT and observe the glide. You can do this little bits at a time by using one revolution on the timer DT scroll (approximately 25-40 seconds of glide time per scroll revolution, depending on the timer). Trim the glide to the edge of a stall with tail weight or by shimming the engine mount to move the CG forward. If you need to vary the stab tilt to produce the desired glide turn width you are also changing the incidence so go back to a quick DT for safety. 1/32” More stab tilt shim equals roughly 1/64” more incidence, so you will have to take some out at the TE or add some at the LE to compensate. As an alternative you can shim the wing platform to change the stab tilt ithout affecting incidence. Remember: proceed slowly. There are several articles that go into FF power trimming in a lot greater detail. The two best are those by Thorkildsen (1996) and Prey (1979). I recommend you read them many times and have an expert flyer by your side as often as possible to give you second opinions on trim changes. You will find that when you are flying the adrenaline is pumping and you are nervous or overly excited. You are not likely to be concentrating on the little quirks the model is exhibiting. Having multiple sets of eyes on the flight will give you lots of insight. The use of a nylon incidence screw under the stab trailing edge is a great benefit, as is a rudder adjust screw. The alternatives of trim tabs and plywood shims just make life more difficult when you are trying to trim your model to perfection. You will need 1/64 and 1/32” plywood shims for trimming the glide turn on the wing saddle and/or stab mount. Some thoughts on Contest Flying Winning at FF power events requires preparation, confidence, consistency, and physical endurance. You must be prepared with well trimmed, well-tested models with which you are very familiar and comfortable. And your engines must perform flawlessly on every run. Don’t let go of your model for an official flight unless the engine is running perfectly. Practice launches until they are perfect every time. Practice them some more with quick DT flights. Trim your model for the flyoff runs. Make sure it transitions consistently on these shorter runs. If you are unsure about this set the timer for a quick DT and check the pattern and transition. The top flyers almost never fail to max out. The flyoffs are where contests are decided and records are set. Confidence is a crucial state of mind. I often see nervous flyers with far superior models get beaten by their more cool-headed competitors. Don’t watch your competitors too much or hang around ogling at the scoreboard. If your competitors have Nelson engines and you have K&Bs, they are sure to get higher than you. You can’t change this. Change what you can. Get your launches perfect every time. Pick air carefully. Know your model’s true dead air potential so you know if you need to pick good air or simply avoid down air to max. And no matter how good your competition is, all it takes is one bad launch to drop a max and his day is done. Consistency and physical endurance go hand in hand. At big meets in good weather FF power events can become max marathons. Start maxing early to put pressure on your competitors. Retrieve, refuel, and fly quickly. You never know when you will have a twenty or thirty max day started. Acknowledgements I wish to extend my thanks to the following flying friends who have shared their lifetimes of wisdom in the fine art of free flight power: Marvin Mace, Russ “Bear” Snyder, Bill Lovins, Chuck Etherington, Terry Thorkildsen, Jerry Murphy, Dave Wineland, Bill Gieskieng, Gene Smith, Bob Hanford, Doug Galbreath, Bob DeShields, Mike Fedor, Bob Combs, Steve Jones, Roger Coleman, Joe Wagner and Joe Menanno. Good Luck and Thermals to All! Originally published in the 37th ANNUAL REPORT of the NATIONAL FREE FLIGHT SOCIETY SYMPOSIUM 2004 Recommended Reading Designs Augustus, Bruce. 1993. “Northern Light F1J” Twenty-Sixth Annual Report of the NFFS Symposium(pp. 122-123). Davis, CA: NFFS. Backer, Russ. January 1978. “Simplex 300.” Model Aviation. (pp. 32-92). Reston, VA: Academy of Model Aeronautics. Booth, Bill Jr. Aug.-Sept. 1997. “Quicksilver 1/2A.” Free Flight. (pp 4-5) Davis, CA: NFFS. Clem, Jim. November 2000. “1/2A Country Boy.” Free Flight. (pp 4-5) Davis, CA: NFFS. Covalt, Richard. March 1984. “Son-of-Pearl 535.” Free Flight. (pp 10-11) Davis, CA: NFFS. DeLoach, Don. November 2003. “Pearls of Seguin.” Free Flight. Davis, CA: NFFS. Hanford, Bob. August-Sept 1998. “NXS 1/2A.” Free Flight. (pp 8-9) Davis, CA: NFFS. Lynch, Bill. Aug.-Sept. 1997. “Laser 660.” Free Flight. (pp 15-16) Davis, CA: NFFS. Morris, Gil. September 2002. “Introducing Pop-Up for 1/2A, F1J, and F1P.” Free Flight. (pp 6-8) Davis, CA: NFFS. Morris, Gil. 1990. “Matchsticks 1/2A” Twenty-Third Annual Report of the NFFS Symposium(pp.111-112). Davis, CA: NFFS. Morris, Gil. 1980. “Toothpicks 1/2A.” Thirteenth Annual Symposium of the NFFS (pp.140-141). Davis, CA: NFFS. Pailet, Jean. February 2000. “Genie II.” Free Flight. (pp 18-19) Davis, CA: NFFS. Platt, Dave. 1995. “Slow-Worm 432” Twenty-Eighth Annual Report of the NFFS Symposium(pp.T13-T14). Davis, . Prey, Ralph. Sept-Dec. 1980. “The Witch Hawk 500.” Free Flight. (pp 3-6) Davis, CA: NFFS. Simpson, Reid. October 2003. “Reid Simpson’s Pea Shooter for F1P.” Free Flight. (pp 15-18) Davis, CA: NFFS. Thorkildsen, Terry. 1991. “Astrostar 600.” Report of the Twenty-Fourth Annual Symposium of the NFFS (pp.84-86).Davis, CA: NFFS. Thorkildsen, Terry. June 1990. “A-B Astrostar.” Model Aviation. (pp.66-197). Reston, VA: Academy of Model Aeronautics.Aeronautics. Valerius, Mark. August-September 1989. “Rum Runner 405.” Free Flight. (pp 10-11) Davis, CA: NFFS. Woodrey, Mark. 1980 “Shocair A/B.” Thirteenth Annual Symposium of the NFFS (pp.138-139). Davis, CA: NFFS. Engines Beecroft, Bob. October 2000. “Time to Make a Stand.” Free Flight. (pp 14-15; 19) Davis, CA: NFFS. Galbreath, Doug. October 1999. “Small Nostalgia Engines.” Free Flight. (pp 22-23; 29) Davis, CA: NFFS. Howard, Hal. November 2000. “Getting a Better Buzz from a Cox Reed Valve Engine, Part 1.” Free Flight. (pp 6-8) Davis, CA: NFFS. Howard, Hal. November 2000. “Getting a Better Buzz from a Cox Reed Valve Engine, Part 2.” Free Flight. (pp 16-17) Davis, CA: NFFS. Howard, Hal. November 2000. “Getting a Better Buzz from a Cox Reed Valve Engine, Part 3.” Free Flight. (pp 8-10, 13) Davis, CA: NFFS. Johannes, Bob. November 2001. “The .049 and .061 Cyclons: Taming the Whirlwind” Free Flight. (pp 8-10) Davis, CA: NFFS. Lee, Glen. January 1979. “All About Two-Cycle Engines, Part One.” Model Aviation. (pp. 10-94) Reston, VA: AMA. Lee, Glen. February 1979. “All About Two-Cycle Engines, Part Two.” Model Aviation. (pp. 46-105) Reston, VA: AMA. Lorbiecki, John. February 1997. “Spring Engine Tune-ups.” Free Flight. (p. 9) Davis, CA: NFFS. Lorbiecki, John. May 1998. “The Care and Feeding of Pistons and Liners.” Free Flight. (pp. 20-21) Davis, CA: NFFS. Nelson, Dick. 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