Now You're Talking: In Support of the Fox .35
Background
As a longtime modeler with almost as long an experience flying in AMA competition (since 1954), my primary interest from 1952 to 1966 and then after 1967 to the present has been control line. I've been a Life Member of AMA since 1969 and a Contest Director since 1978 or 1979. Most of the activity has been fun, and when it has not been, I changed my own direction.
Since PAMPA grew into a strong organization, it has been a major factor in revitalizing control line generally. Surveys performed among the PAMPA membership reveal a heavy proportion of members with control-line interests who aren't competitors (yet) and are seeking additional support at the beginner/intermediate levels of participation.
There has been greater inflation in costs related to modeling in the past 15 years than in the previous 25. More than ever, the starting point for beginners is receding from the financial reach of many potential fliers. With recent publicity regarding adding piped exhaust systems to expensive, ball-bearing-equipped, Schnuerle-ported model motors, there may be an appearance of further complication and expense.
One of the leading sources of these exhaust systems has supplied only about a quarter as many pipes as PAMPA's total membership. PAMPA's current president, Ted Fancher, has suggested that the non-expert will benefit almost as well from using the same type of motor by simply choosing lower-pitch props and running more ordinary mufflers for Stunt applications.
Availability and Support
I've seen a few generally negative comments about the old OTS/Classic engine choice, the Fox .35. Old-Time Stunt events fly the 1952 pattern with models pre-dating 1953. Classic events fly modern pattern designs pre-dating 1969. My personal experience was that a Fox .35 is particularly sensitive to fuel-system variations when laid on its side, and I'm not convinced the entire problem is simply that the plug is getting flooded.
Of all the engines we use for control line flying, the major advantage of the Fox is its widespread availability. No matter how "RC-centric" a retail shop may be, it's still about 90% likely that a Fox .35 will be in the display case next to all the Super Blootz 91s. At the present time, the only engine in a close second position is an O.S. FP; it is similarly priced and easily converted from its usual throttle arrangement to an ordinary venturi insert.
A rather high percentage of sport-flyer modelers are both resistant to buying through mail order and are impulse buyers. That Fox .35 is the one sitting out there in all those display cases, and it's also sitting on the shelves in hundreds of thousands of garages. We might wish it were otherwise, and that some other model engine was more common, but the real fact is we'll be using these engines for a long time yet.
I have some qualms about a wholly owned company like Great Planes being owned by a high-volume mail-order outfit like Tower. We had serious problems getting control-line engines and parts from World Engines; the Fox Company has continued to support the control-line fraternity almost religiously. I respect that kind of support.
The Brodbeck family at K&B has also been supportive, of course; however, their products haven't been as predominant in control line as Duke and Betty Fox's engines. Without having seen either company's production figures, it's my feeling that Fox Manufacturing is comparatively larger overall.
Fuel System and Tank Details
Rather than tossing the baby out with the bathwater when we run into the same old fuel-system problems that we've always had with Fox .35s (as far back as I can remember), let's examine why some folks get better results with one of these old workhorses.
For instance, I have a plane we could call a Buster-Ringmaster (I just call it a modified Ringmaster). It flies best with an old Fox .25 — that was a better motor in lots of ways than the .35. When it has the .35 in it, I get very good engine runs with almost none of the characteristic "burps" at inconvenient times.
The tank I use is a square-wedge type; it's a reworked "Don's Combat" tank (a lightweight version of the Veco T21 one-by-two-inch type). The tip-in pressure vent originally ended at the top inside front corner. Now the muffler pressure vent goes to the same place inside the tank, much further outboard. There is also a uniflow vent, which is the usual one I use. Tanks of other types simply haven't worked well with the Fox .35, and I've tried numerous styles.
Tanks tried include:
- Plastic clunks
- Chicken Hoppers
- The antique Perfect Wedge
- The tall Veco/K&B/Claryl/Fox "profile" tanks
- The more recent "oval" tanks
The needle-valve assembly that used to come with the .35 was rather poor. We used a now-extinct replacement from Austin Craft for about twenty years, and an O.S. or SuperTigre unit after that. The primary difference isn't the tank itself; my opinion is that it is the relationship of the fuel supply to the motor. The fuel line should be short and routed very directly; a filter should be located next to the spraybar; and the tank should be sunk into the fuselage so that half of its width is inboard of the spraybar location.
Experience and Recommendations
The basic Fox .35 design goes back to about 1947, which pre-dates profile-type models somewhat. It's a decent, if not great, motor with its limits, and it has earned an honored status in the history books of modeling.
Its range of application remains good, and it has the greatest availability factor of all engines used for control line. Rather than denigrate it now, let's look at possible solutions — beyond my own skunk tanks — that potential competitors in control line can apply to improve their planes' performance.
Bill Dawson San Antonio, Texas
Transcribed from original scans by AI. Minor OCR errors may remain.
