Control Line: Racing
By John Ballard
Racing Fuel
I have had numerous informal and written requests for information on basic fuel composition and the percentages used by top competitors in each racing event. The past few years have produced constant price increases on fuel ingredients, especially nitromethane. In the early 1970s nitro cost approximately $4.50 a gallon, contrasted with 1979 prices of around $20.00 a gallon. I have observed advertisements for preblended fuels in the model magazines and club newsletters. When racing fuel was listed at 40% or 50% nitro content, it could easily cost $25–$35 a gallon, including UPS charges.
Certainly, it is in the racing enthusiast's interest to use only the amount of nitro content required to produce acceptable speed, good pitting, and respectable engine life. I have seen many competitors dose their fuel tanks with 65% or 75% nitro fuel, only to find their air speed very close to the same as with 40–50% fuel—plus they had increased problems with plug life and restarting. In these instances, the lack of satisfactory air speed was obviously the result of one or more other factors.
Basic ingredients
Basic fuel components have not changed drastically since the early 1960s. Don Hoyer sold his Custom Blend racing fuel over the entire Midwest area from the trunk of his car and also by Parcel Post. Don used 5% to 8% nitrobenzene co-solvent to ensure the higher-nitro fuels would accept castor oil as the principal lubricant. With the acute toxicity information available today on nitrobenzene, its use in fuel has been halted. I recall a special racing fuel popular around the Chicago area sold in glass bottles called Wysongs — "This Is It" — hopped up in the late 1960s. Hoyer was the only fuel blender who posted the nitro content on each of his fuels. The general lack of fuel information prompted many competitors to "home-brew" their fuel to control nitro content and ingredient quality.
With the demise of nitrobenzene as a co-solvent, stable fuel solutions required the use of synthetic oils. At about 25% to 30% nitro concentration, castor oil becomes insoluble. A portion of the oil forms globules similar to chicken fat in soup. No amount of mixing will reincorporate the oil. Synthetic oils, on the other hand, are mixable with all concentrations of nitro.
Generally, the synthetic oils used since the mid-1970s include Union Carbide's MA-2270, MA-739, LB-625, LB-525, and LB-1100. The amount of oil used varies, since there are endless opinions on the subject. I use 18% LB-625 and 2% Luberzine N-1. The N-1 is added to improve the wetting properties of the synthetic oil and to minimize engine damage during lean runs.
I think the problem ingredient in present formulas is methyl alcohol (methanol). Typical methanol has between 2%–8% water included, and methanol is a water scavenger. On a humid Midwest day, an open fuel container will pick up another 5%–10% water. Included water causes engines to run hot, and special care must be taken to eliminate the moisture if predictable performance is to be expected. The remaining portion from a jug of fuel used on a humid or rainy day should be set aside and used only for "rich" break-in runs.
Typical 50%-nitro fuel formula
- 25.6 fl oz — Oil — 20%
- 64.0 fl oz — Nitromethane — 50%
- 38.4 fl oz — Methanol — 30%
- 128.0 fl oz — Total — 100%
(128 fl oz = 1 gal.)
Keeping the oil constant at 20%, you may vary the nitro and alcohol as required. Always check your calculation; it must total 128 fluid ounces.
Let's improve participation
When the 1986 AMA rule book comes out, Mr. Jim Ricketts, chairman of the Racing Advisory Committee (RAC), has sent me a summary provided by Bill Lee on the basic feelings of the majority of CL racing competitors who attended the 1983 Nationals. Bill has added some personal opinions (shared by others) on the subject of Rat Race and Slow Rat. I am including Bill's letter and would solicit comments from other racing competitors.
Last year at Westover there was significant conversation among the racing fliers about various changes that could or should be made. I would like to list the ones I'm interested in and ask that you pass them on to the RAC for possible sponsorship.
Rat Race
Rat has gotten so completely out of the realm of reason that only a few compete in it—and those few do so only because they have a capable pilot close by or can count on one being available at contests. If you recall, we made a straw poll at the Nats about the possibility of .21-size engines being specified for Rat. While some were a little reluctant for personal (mostly big-dollar investment) reasons, all recognized the need.
I would like you to ask the RAC to support the following changes, to be incorporated into a new supplemental event for 1986–87 with complete replacement in 1988–89.
This new event would bring forward all existing Rat rules, except for limiting the maximum engine size to 3.5 cc (2.135 cu. in.). Additional topics that might need to be addressed (individually) would be:
- Proposed limitations.
Slow Rat
I would like to pass the following two questions on to the RAC:
- What is the future of Slow Rat?
- What should we do about that future?
Of course, as you would suspect, I have my own answers to those questions.
I believe the future of Slow Rat is very dim. The event's original purpose was to provide an event that could be "gotten into" by a larger portion of CL modelers than Rat, since Rat, even in the mid-1970s, was more than most people could handle. We tried to structure the event to provide an official AMA racing alternative that was at a performance level obtainable by many and flyable by those with lesser skills than required for Rat. The original proposal disallowed Schnuerle-ported engines — a proposal that never made it to the initial set of rules. What has happened is history: a performance curve that has made Slow Rat into another event unreachable by anyone except those with one or two capable pilots at their disposal. The changes this year will help — the 10% fuel will temporarily allow the event back to a lower speed. But I foresee a fairly rapid return to performance levels near where they were before — again, unreachable by the "less-than-great." Slow Rat is decaying in contestant involvement, as all previous events have when allowed to reach too high a performance level.
I do believe something needs to be done if Slow Rat is to be salvaged. I have several suggestions, most of which you've seen before. I would like the RAC to think long and hard on them and maybe support them.
- Engine availability and performance levels must be addressed. There are no competitive .35s available on the market today. K&B .35s are nonexistent. The Tee Dee .36 and OS .36 are no longer available. I propose we allow the use of specially ported .40s as a class of engines that provides a large choice of compatible engines. One such class is the Quickie 500 engines that the RC boys use: front intake, single-bypass-port .40s. There are several different brands here, the most competitive being the Como, K&B, and HB. All are available at any good hobby shop (or they can be purchased at discount from magazine advertisements). This engine class, along with a few others, would be a wise choice. Another class to consider might be the 3.5 cc engines as described above for Rat. Again, we would have a significant decrease in ultimate horsepower but a significant increase in availability.
- Plane configuration. A typical Slow Rat model has 50–60 sq. in. of wing area and is difficult to build like many other types of models. It is a lot of work to put one together. We might consider new classes to permit simpler models — but only if a corresponding decrease in horsepower were made. The Quickie Rat design we use in this area provides an easily built model that is easily flown by someone of virtually any skill level. Even I pilot these things. They can be built with minimal investment of materials or time. The performance level with restricted engines is very reasonable, around 17 seconds and slower. But I would fear this model if it were allowed significant horsepower! Any change here must be accompanied by a decrease in available horsepower.
That's the end of Bill Lee's letter.
Northwest Regionals
The Winston-Salem (NC) AAAA Control Line Meet was one of the highlights of the racing season in the Midwest area. Our Northwest colleagues have developed this type of annual contest in Eugene, OR. The Annual Northwest Regional Control Line Championships over Memorial Day weekend (May 26–27, 1984) will feature all racing events. Certainly, if at all possible, it should be included in your competition calendar.
For more information, write Contest Director John Thompson, 1411 Bryant Avenue, Cottage Grove, OR 97424.
As always, your comments are appreciated.
John C. Ballard 10102 Kimblewick Dr. Louisville, KY 40223.
Transcribed from original scans by AI. Minor OCR errors may remain.
