RADIO CONTROL AEROBATICS
Eric Henderson, 303 Shady Ln., Marlton NJ 08053; E-mail: [email protected]
There is a pair of new engines aimed at the Pattern market: the 3M Mintor 1.40 and the Mintor 1.70. Both are rear-exhaust engines produced by an Italian company, and they have been designed, engineered, and manufactured to meet the needs of modern F3A models. The manufacturer of the new engines states:
“Until now, very few engines on the market have been able to meet these demands; in fact, other than the Japanese Yamada and O.S. models, there are no other valid alternatives on the competitive field. [This firm may not be familiar with the German-made Webra 1.45, and you can debate the word ‘valid.’]
“Mintor srl, a Bergamo company specialized in precision mechanics for over thirty years, has achieved its aim by providing top performance at a very attractive price. The engines were created from an innovative structural design and processing procedures that are not found in large-scale standard production.
“Hours were spent working towards the goals set the moment the project was started; from months of bench tests and flight tests, to adjustments and meticulous fine-tuning, resulting in the final version.
“All the engine parts that are normally cast (crankcase, pumps, piston, carburetor, etc.) are machined from solid aluminum instead of castings. Only the best aeronautical aluminum has been used, allowing a reduction in weight and total absence of micro-porosity, as well as much greater structural rigidity than even the best castings available on the market.
“Finally, all the engine parts have been subjected to anodizing and anti-corrosion treatment which protects them against the effects of nitro-methane.”
Manufacturers’ claims are one thing. The proof of the pudding, however, is in the eating. The 1.70 version was fitted to my “year 2000” Hydeout. It used to be the home of a YS 140 L, then most recently it hosted a YS 140 DZ. When changing engines, the center of gravity (CG) is often affected. A good practice is to drill a 1/16-inch-diameter hole in each side of the fuselage where it (not the assembled airplane, but the fuselage itself) balances. This is best done after the flight tests. Then any subsequent changes to the fuselage configuration can be checked on the bench to see if they have changed the balance. Things that can cause weight changes are servos, batteries, pipes, mounts, spinners, and, of course, engines.
It is interesting to see how much variance there is in the weights of our current choice of two-meter power plants. The following engines were weighed with headers included, but no propeller nuts or washers. The YSs had the steel CD header without the Teflon connectors. The two-stroke engines had their aluminum headers, but no silicone connectors.
At all times the Mintor engine transitioned flawlessly and only quit when the fuel tank was empty. This is probably because the twin-plug head does its job.
Now we have many choices:
- O.S. 1.40s (EFIs and RXs)
- YS 140s
- Webra 1.45s
- O.S. 1.60s (FXs and FRs)
- Mintor 1.40s and 1.70s
- Soon: Webra 1.60s, etc.
The Pattern scene gets more intriguing with all of these choices—unless you are indecisive!
Engine Mounts
There is a time when a two-stroke engine idles so low that it "bounces" as much as a four-stroke at idle. They both smooth out at 2,000–2,500 rpm. The best setup is a non-nose-ring isolation mount such as the Type A Hyde Mount.
All current nose rings seem to add airframe vibration. They provide poor isolation compared with mounts and must be set with no side pressure to be effective. Nose-ring installations tend to cause aileron “buzz” at certain in-flight rpm settings. This can kill the digital aileron servo and drain battery power. The four-stroke is the worst culprit by far.
The smoothest setup is a two-stroke with no nose ring. Newer airplanes have room for a bigger “hockey puck” rear plate. Models with fiberglass cowls are much easier to install without Herculean engineering of a nose-ring support.
There is a flood of Pattern Almost Ready to Flys (ARFs) coming into the USA, including:
- Top-end Tai-Ji
- Low-end Tai-Ji
- Swallow
- Stream 50
- Zen
- TT Imagine
- Focus
- Focus II
- Majestic
- Advance
- Javelin
- EZ Hydeout
There is also a raft of so-called 3-D airplanes such as the U-Can-Do, Freestyle, and Giles, plus a bunch of aerobatic sport models.
This influx at club fields creates a veritable harvest that precision aerobatics enthusiasts should prepare to reap. As a reader of this column, you are an agent: every one of you has the power to run an aerobatics fun-fly.
Do a clinic in the morning and a simple contest in the afternoon. Contact your National Society of Radio Controlled Aerobatics (NSRCA) vice president (see www.nsrca.org). Ask fellow NSRCA members to help you. Give presentations at your club. Sell (don’t just tell) the fun and challenge of following a schedule and doing it well, and add the pleasure of taking a model home in one piece after a fun-fly!
Frank Granelli, NSRCA District 1 vice president (AMA Districts 1 and 11), showed what can be done. He hooked up with Vlad Camera of the PARCS (Pennsylvania Avenue Radio Control Society) club, which flies at Floyd Bennett Field in Brooklyn, New York. Frank and his wife Ann ran a Pattern clinic. In early May he recruited me, Rick Wallace, and Joe Lachowski as judges and ran a Pattern contest at the end of the month. He coached every pilot through every flight. That is what is needed to build a better Pattern world.
The challenge is: can you pick up the gauntlet and do something similar? We have more troops on the ground than we realize. You can reach newcomers and ex-Pattern fliers who are ready to come back. Imagine the growth we could create if each one of us found one more Pattern pilot or ran one more contest. Think bold!
I was at my local hobby shop because of the spring weather, and the owner asked to borrow my YS 91 engine. He wanted to put it in a newly arrived Creek Hobbies Quest .90 ARF. I had ordered one at the February Westchester Radio Aero Modelers show, so I declined to lend the engine and took my Quest home with me.
The model comes with an instructional compact disc that you can print out and save on your personal computer. By saving it in a data format you can read it online and look like you’re working. The best part is that you can add your own construction notes and sequencing.
The YS 91 engine and the RX/servos, etc., are ready to install because the Swallow I mentioned previously has gone to a good home in Brooklyn. With the scales still on the bench from weighing the engine, it was natural to weigh the primary components. In general, ARFs of the past have been on the heavy side. Not the Quest.
Parts and weights (ounces):
- Stabilizer: 5.2
- Rudder: 1.2
- Wheelpants: 2.0
- Undercarriage: 6.0
- Long cowl: 5.0
- Wing 1: 14.0
- Wing 2: 14.0
- Canopy: 3.8
- Fuselage including fin and wing fairing: 25.8
That is 72 ounces (4.5 pounds) before assembly and “ironware” is added. I figure there is approximately 3 pounds of additional stuff, yielding a 7.5-pound model with a YS 91 on the front. It looks promising in the greater-than-1:1 power-to-weight department. If not, there’s a YS 110 coming soon. The kit box’s predicted weight is 3.4–3.8 kilograms.
The model has a 72.5-inch wingspan, which will make it visible at Pattern distances. It is also billed as 3-D-capable, which will attract more than Pattern pilots. There’s that opportunity again where you can “snag” a potential precision aerobatics pilot! Last but not least, this airplane is a candidate for artistic aerobatics set to music.
It’s time to go build (assemble).
MA
Transcribed from original scans by AI. Minor OCR errors may remain.
