Dog-days bits and pieces

Transcription

1 Dog-days bits and pieces If you didn t know, it s been and still is very hot As your editor writes these words, it is well into September and the temperature at my home in Riverside shows 106 degrees on my electronic weather station. It s been a rough flying summer for us in Southern California. July set heat records all over the area and it cooled down a bit during August (if you consider the mid-nineties cool). Temperatures this high put quite a strain on electric motors and batteries, not to mention our aging bodies. Fortunately, most of us modelers have the good common sense not to venture forth and risk health and our expensive equipment with heat that will melt your sunglasses. Of course, there are those of us that try to beat the odds and get our flying fix even though it is quite warm. Here is one very important safety tip: In very high temperature conditions, do not attempt to fly alone! Also, don t charge your flying batteries with your car battery as you stand a good chance of getting stranded and the desert caravan may not arrive for days. Do the math: How many amps can you draw from your car battery until it doesn t have enough power left to start your vehicle? If you have been to the field in the last couple of months, you have no doubt noticed all the many rows of what they say is organic compost located north of the field. It is brought in by large trucks and is offloaded in long rows. The big problem that affects us is that this steady stream of trucks has made the entrance to the field, off the pavement, full of deep ruts and fine powdered dust. When you go into that area you will get some major league bumps and be enveloped in a dust cloud. Just take it easy and drive slowly as you enter because your visibility will be restricted. Recently, Malcolm Oliver has been writing an article each month appearing in Prop Talk. He is an outstanding writer and his articles are very interesting and timely. Please take the time to read them. RRCC CLUB OFFICERS President: Jeff Szueber Vice-President: Bob Baker Secretary: Rob Evans Treasurer: Larry Roberts Safety Coordinator: Jim Bronowski Field Director: Dale Yaney Newsletter Editor: Jim Bronowski Turbine Flying Director: Berry Hou ALL OFFICERS MAY BE CONTACTED AT: NEXT MEETING SATURDAY Sep 15th 10:00 am crowley field

2 Call to Order: President Jeff Szueber called to order the regular meeting of the Riverside RC Club at 10:14 AM on Saturday, August 18th, 2018 at Crowley Field. Minutes of the Previous Meeting: The meeting minutes of the July 2018 meeting were approved as written and published in the August 2018 Prop Talk newsletter by the members present. Old Business: No Old Business was discussed. New Business: No New Business was discussed. Show and Tell/Presentations: Raffle: There was no Show and Tell. 15% fuel Thin CA Glue Medium CA Glue Electric Arming Kit Cable Clips LiPo Battery VTOL Fun-Made Model Meeting Adjourned at 10:41 by Jeff Szueber Minutes Submitted by Robert Evans Dale Yaney and his latest. It flies just great! Cockpit to what airplane? Answer elsewhere in this issue.

3 By Malcolm Oliver he was on the Hacker stand and spent over half an hour with me talking about an electric set-up for the Quique Somenzini 85 YAK 54. I left the show with lots of new knowledge and around $2,500 lighter in the wallet. $1600 of this was spent just on four 22.2V x 5000 mah Duralite batteries! made a ratcheting sound! The following day I was in Diamond Hobbies, when they had a store in San Diego. Lo and behold the guy behind the counter was talking to another customer about exactly the same problem. Apparently caused by voltage drop across the connectors between the ESC and motor, recommending that the 3 leads should be soldered rather than using a connector. Problem solved! Electric Power Systems for R/C Airplanes The Agony and the Ecstasy I really intended to write this article some years ago but I kept shaking my wrist but no words came out of the pen! So, some of my observations here may be old hat but I ve included them to give a complete picture of the pros & cons of electric power systems for R/C airplanes. Since the late 1990 s I d seen a number of people flying electric powered airplanes, usually a TeleMaster or something similar with a large wingspan/wing area. The batteries were NiCads. Very heavy with a low discharge current. Overall, I just dismissed these attempts as having no real future. I went back to flying my glow motor powered planes and enjoyed wiping off the fuel and oil at the end of the days flying. It was 2006 when that light bulb got switched on and I got religion about electric power for almost any powered R/C airplane type. At the 2007 AMA West convention I met Andrew Jesky, I already had a Great Planes Patty Wagstaff Extra 300 and so bought an AXI 5330/F3A and a Jeti Opto 90 ESC which as far as I could determine were both adequate and compatible. This was very much a new experience in trying to match the model/battery/esc/motor combination. Soon it was the time to try out the motor system in the workshop. The plane was tethered to the bench and ready for the first low speed run. Everything was switched on, the ESC initialized and then I opened the throttle - NOTHING. So, I checked all the connections and tried again. Momentarily the prop turned followed by sparks and flames from the ESC. A firework display wasn t what I was hoping for! Fortunately, Hobby Lobby were very helpful and exchanged the ESC for a new one. I thought that I had damaged the ESC when soldering on the Deans connectors. They said no, it was a manufacturing defect. 10 days later I was ready for another system test. This time the prop ran OK except that at anything above 20% throttle the motor In the meantime, my Quique 85 YAK 54 arrived and as it was much easier to locate the long batteries in the model (at that time the batteries were packaged as 3 layers of 2 cells end to end), I decided to use this as my first model. I had also bought a Hacker A60-16L motor which didn t exhibit the ESC connection problem I d experienced with the AXI. Unfortunately, amateur hour happened again. The QQ assembly manual quoted the surface travels as the 3D settings with no indication of the exponential to use. I set the expo at 40% on all surfaces. Apparently QQ uses 85%. Also, the CG was shown as the 3D, more rearward position. The first flight was nail biting! The elevator was super sensitive and the roll rate had to be seen to be believed. Inevitably I ran out of talent on the landing approach. Not only did I re-kit the plane, the $800 batteries were now about an inch shorter and scrap! I called QQ Planes, somewhat tongue in cheek. They offered me a new kit for $200 instead of $650, a deal I gladly accepted. Incidentally they also updated the on-line manual to show 3-rates, each with their expo settings. The next flying

4 session with the new plane was much more successful. I also discovered HobbyKing and Zippy batteries. My wallet breathed a sigh of relief! They were only 10C rating but as a 12S set-up the maximum current capability was more than adequate. Now I use the Zippy Compact design 6S 5000 mah 25-35C batteries. My next adventure was to get improved motor performance. A NEU 1521/1.5Y 1040KV inrunner motor with a 6.7:1 gearbox was the answer. The only drawback is that they cost $555 compared to $260 for a Hacker A60 16/18L out-runner motor. Another benefit was that the NEU motor was some 6-7 ounces lighter than an outrunner. Reducing weight is always a target of mine. All was well with the NEU motor set-up and the airplane performance had improved. Until I got to around 30 flights. Then one of the motor input wires fatigued and burnt out. I had 2 of these motors and the same failure occurred 3 times on them. Fortunately, NEU replaced the motors FOC and after some investigation I found out other users had experienced the same mode of failure. Lo and behold a modified motor was introduced after a couple of years. The stiff wires had been replaced by flexible ones, the wires were supported internally before they exited the motor case and an internal fan was added. I ve not had any failures with the new design on 3 motors over 300 flights. Just to complete the agony of my electric flight experience. I was flying the YAK 54 when, all of a sudden, it appeared that I had a functioning smoke system. One of my batteries had started to emit dark brown smoke. Fortunately, I still had control of the model and managed to land it. With smoke pouring out of the fuselage I removed the batteries and threw them as far away as possible. It turned out that one of the batteries had developed an internal short, the second battery was OK. The airplane wasn t damaged other than a little internal staining from the smoke. But here was the amazing bit of luck. At the time, I used a Castle Creations 10 Amp BEC which can only have a maximum 6S input. The supply battery for it was the one that was OK; phew! Finally, a very important lesson learned was to concentrate on flight preparation and don t be distracted. A few years back as I was installing the flight batteries I started talking to another pilot. I use 6 mm bullet connectors for the power cables as it makes a cleaner, lighter and higher current capacity series installation. Each connector on the battery cables has a PVC cap which I remove as I make each connection BUT this time I had removed both connector caps on one of the batteries, then proceeded to plug them together! BOOM, the direct short blew the connectors apart. Both of my hands were black, and the palm of my right hand burnt. It took nearly three weeks for the burns to heal. Amazingly, once I replaced the connectors, they had completely melted, the battery was OK. So, stepping back for a moment, I decided to review my electric power flight experience compared to the 30 years I had spent using glow motors. Just to complete the tales of woe I ll complete my list of disadvantages first. A whole new technology to learn: matching the motor, propeller, ESC and battery to the model is not as straight forward as choosing a glow motor, primarily due to a lack of experience. There are now a number of Calculators available to help with this task. Check out the Castle Creations, Hacker Motors USA or NEU Motors web sites. The initial investment is more expensive: As well as the motor and ESC you ll need several sets of batteries, I usually have 6, enough for a reasonable day s flying. Another expense is the charger/chargers for the power batteries. Over the last few years the cost of batteries has reduced substantially, helped by HobbyKIng, at the same time the cost of glow fuel has gone up. The motor, ESC and battery is usually heavier than the glow motor equivalent. However due to the lack of vibration there is an opportunity to reduce the airframe weight. Using an inrunner motor also saves weight but adds a significant cost. Your life-time fuel supply is in the air for every flight. In the event of an unintended landing, almost certain to happen at some time, your battery is at risk of destruction.

5 Flight times are generally shorter. However, if you set-up a flight timer controlled by the throttle stick you can then have confidence that you maximize the flight time to the use the full (about 85%) capacity of the battery. Obviously, this takes 2-3 test flights to get right. I actually set up 2 timers, one to give the total flight time, controlled by the throttle-cut switch and throttle stick. The second to give a power on time controlled by the throttle stick over the range ON 5% - 100% - 3% OFF. This timer is also controlled by the throttle-cut switch. Usually a 7-minute power on time translates to a total flight time of 9-10 minutes. No noise, I like some noise but from an environmental/neighborly point of view the lack of noise is good. Fortunately, with larger electric applications there is some propeller noise which helps. What I don t understand is how anyone gets satisfaction from flying the numerous smaller electric powered warbirds available. They look great but silent, no thanks. I d be very tempted to go back to a glow engine or a small gas engine. However, for larger electric applications there is hope on board audio systems! This will be the subject of another article. So that s the Agony over with so now let s deal with the Ecstasy! A completely clean airplane after every flight. It only requires a polish every so often using some car wax/detailing spray. Gone are the days of spraying the plane with 409 and then wiping off the oil. Also finding a stain on the car carpet from oil which has drained out of the muffler is a thing of the past. No oil-soaked airframes or fuel compartments full of fuel because a fuel tank hose has split or come off. Another benefit is that when refueling there s no spilt fuel degrading the tarmac or grass surface of the pit area. No endless flipping of the propeller, the glow plug has burnt-out, the glow igniter battery is discharged, or the fuel has become contaminated with moisture. You have none of these problems with electric power. No cut fingers, how many of you have had your finger bitten by a propeller? That risk has gone, flight line safety is immediately improved. No needle valve settings to worry about, that critical idle setting isn t a concern anymore and there is no risk of a lean or rich engine run and minimal risk having to execute a dead stick landing. The rest of the fliers in the pits don t have to listen to your screaming engine as you adjust the needle valve attempting to extract the last ounce of reliable power. Throttle response is consistent, upright or inverted there s no momentary cough as the engine clears its throat and you take a deep breath. The motor response is always reliable, instantaneous and consistent. There s no vibration, engine mount bolts don t come loose, or the muffler falls off, so you end up with a lean running engine and poor/no idle. You just hope that the fuel tank pressure hose stays attached, or you end up playing hunt the muffler all over the flying field. Motor power is unaffected by altitude, obviously propeller performance is still affected but for glow engines high altitude flying is hit by a double whammy. The CG is always constant, the CG doesn t change as the fuel load reduces. One thing is certain that if the CG does change on an electric airplane then something is seriously wrong! Decals, covering material and trim don t peel off. You can be assured that your model will look just as good in a years time as it does today. I like to have decals on my airplanes representing the manufacturers of the equipment that I m using. So constantly having to replace them is a pain I don t need. They brighten up the plane, which for me increases my satisfaction when flying. Also, for paint trim you are not restricted to using fuel proof paints. There is also the added benefit that when you get tired of the plane, its resale value will be higher. So that s about it on the disadvantages and benefits of electric powered airplanes. I m totally sold on electric power, it takes away a complete area of concern when flying allowing me to focus on my flying skills and boy do they need some focus! Oh, for a pair of 18-year-old eyes, together with the hand/eye coordination and reaction time to go with them. That s all for now, don t forget that flight line check before every flight. Malcolm P-39 Airacobra Cockpit

6 RIVERSIDE RADIO CONTROL CLUB P.O. Box 295 Homeland, CA 92548