When I first saw this thread I decided to not respond; I’ve written a bunch about my feelings regarding electric flight over the past few years, and reasoned that it was a good time to lay out and see what others had to say. Now I’ve counted to ten (something I’m trying to do with all threads that are controversial, and often with little to no success…) several times before responding on this subject. What I’m passing on here is what I hope will be looked upon as my take, not the only take, on the subject. Everyone is entitled to their own opinions.
My first experience with even semi-modern electric flight came at the 2005 Nats. I was judging at that Nats and after the qualification round I was judging on circle two was finished I strolled down the L-Pad to watch the final qualification flights on circle three. It was very windy that day and as I approached the circle I saw a model cutting through the wind very impressively. And I noted that it must have been fitted with a very good muffler as I could not hear it running. Then it dawned on me that it was electric powered.
I found out that it was Walt Brownell’s Arc Angel. That flight was Walt’s last official for that Nats, and I did something I almost never do; I asked him if I could fly it. He enthusiastically said yes, and we went over to the empty circle four. I got a handle setting and Walt installed a fresh battery. What followed was for me the most dramatic epiphany in my flying career. He launched the Arc Angel and on the takeoff roll I knew my competitive stunt life had changed in an instant. The power was not overwhelming (none of those early electric setups were ultra strong…), but the constant line tension and pace of the flight convinced me that this was the next big thing in stunt. If I have any talent at all, I believe it is in a sort of strategic thinking about coming things.
I thanked Walt for the ride, and then got on my phone and called my buddy and tech guru, Dean Pappas. I asked him if converting my Genesis Extreme was feasible and he said that he’d been waiting for me to come to this conclusion for a while, and he then rattled off all the stuff I’d need to do the conversion. Then he came over to my shop when I returned from the Nats to help with the installation/conversion. When the retrofitted Genesis was ready to fly, Dean installed an RC receiver and hooked it up so that he could make throttle adjustments while I was flying. He sat in the center of the circle with me while he made the adjustments and asked my opinion of how the model felt with each adjustment. Then, armed with his notes, he went home and came up with a method of installing different “scripts” to adjust the RPMs of the motor. Yes, it was unwieldy having to bring a lap top computer along to the field to make these changes, and even then the power was not overwhelming, But, the consistency and the repeatability from flight to flight was amazing.
In my typical habit of rushing to bring a new idea to fruition to quickly, I opted to fly that setup at the upcoming 2006 team trials. Now, it’s true confession time here. The fact that the weather at that team trials never got very windy made it possible for me to showcase the somewhat anemic system to best effect, and I made the team. Looking back, I should have not flown that system there. Now the pressure was on to fly an electric model at the World Championships in Spain the next year. And, I realized that we would need a much more powerful system in order to compete properly in all types of conditions. Dean said he could design such a system, but he needed someone else to write the more sophisticated code required. I drafted a friend who had those skills, but he was not able to focus on the project right away due to family and job issues. I decided to hold off and wait for him to produce what we needed. That was a major mistake. When he did get time to focus on the new system he found a lot of problems and could not solve them quickly. He kept putting off the project, again due to personal issues. I should have at that point just flown a glow model in Spain. I didn’t. I waited until the eleventh hour - almost literally - and received the somewhat rushed system only a day before scheduled to leave for Spain. That was perhaps the biggest mistake of my CL Stunt competition career.
Electric wasn’t ready for prime time, and neither was I with the system I had in place. The result was a dismal placing, well outside the “cut.” That was the only time in my WC competition career that I failed to make it into the finals. And, to add insult to injury, I screwed it up for the rest of my team (Paul Walker and David Fitzgerald) to have a chance at the top spot in the team placing. For the record we finished in third (Bronze Medal) mostly because of their very high placings.
As you are probably all aware, the technological advances in electric flight came hot and heavy globally from that point on. I remember saying to someone back then, “Electric is the worst it’s ever going to be today.” And I still stand by that quote; electric technology is expanding and improving seemingly every day. The batteries are getting better by leaps and bounds, the motors are better and more efficient, the active timer flight management systems are ever improving, the ESCs are getting better, the propeller development for electric flight has improved greatly over the past few years, and our understanding of how to implement all these factors into new airframes that are designed to optimize that mode of power has moved forward dramatically.
Perhaps I should list the reasons why I prefer electric power over glow. But, a disclaimer first. Glow power (to paraphrase SNL’s Garrett Morris…) has been very, very good to me! I have nothing bad to say about glow power, or about those who prefer it over electric. Everyone should go with whatever works best for them.
Reasons why I like electric:
1: Consistent, reliable, repeatable performance over dozens - if not hundreds - of flights. Once the system has been adjusted to my liking I can fly for a long while without changing anything. In fact two years ago I put 200 flights on my Crossfire without changing anything!
2: The balance point stays the same throughout the flight. I have found that having the balance point in one place all through the flight makes my control inputs more consistent. As a glow model burns off fuel north of the balance point, the airplane reacts to inputs differently; it becomes progressively more tail heavy. This was found to be a huge benefit in heavy wind near the end of the pattern. With a glow model the balance point has shifted aft significantly due to fuel burn off and the overhead eight becomes more difficult to track. With the electric system there is no balance point shift and the model tends to be much easier to track (steer, if you will) through the overhead maneuver much more solidly.
3: The ability to adjust the vertical (roll) balance point at will by shifting the battery up or down (usually up). I’m convinced that a lot of my trim problems over the years were due to an improper vertical CG location. I have noted over the years that the vast majority of new stunt planes when flown for the first time exhibit a slightly outside wing riding high condition (it is hardly ever the other way around…). Of course the first thought is that there is either a warp in the wing that is causing that, or misaligned flaps that need some “tweaking.” I use mostly foam core wings (duh…), and I’m very careful in cutting, covering, and joining them, so I’m confident that a warp is not the cause. That leaves a flap tweak. In the past when I’ve encountered this situation (fairly often), I immediately went the flap tweak route. And in many cases even though the tweak worked to level the wings, there was something that just didn’t “feel” right. Now I realize that it was a condition of low vertical center of gravity and my flap adjustments were fighting that and causing other problems.
Our models are tethered at the leadouts, and if the vertical center of gravity is too low the weight below the vertical CG swings outward like a pendulum and forces the outside wing high in level flight and low in inverted flight. A good case in point is my beloved Genesis Extreme. It was originally powered by a glow engine (in fact it had two different glow systems installed over time). It initially needed a slight flap tweak to get the wings level, and it never felt right to me, even though it was very successful. When I made the changover to an electric system in that model and it still didn’t feel quite trimmed. Dean Pappas suggested experimenting with the vertical placement of the battery. He suggested moving it up 1/8-inch. I did that and was then immediately able to remove the flap tweak, and the model instantly felt just wonderful. Additional small adjustments in the vertical CG with the battery yielded what was perhaps my best flying plane ever to that point. This is a major trim tool that is not easily available in glow. If you were to move the tank up (or down) to achieve the proper vertical CG, it would affect the engine run (yeah, captain obvious here…). And even if you could use the tank to make such an adjustment, the fuel would burn off throughout the flight and negate the trim change anyway. I suppose you could add weight above or below the tank in a glow model to address the vertical CG location, but that would require adding extra weight, and you might not be able to add it high (or low) enough to cure the problem. The battery adjustment up or down in an electric model does not add any additional weight and it is extremely effective.
4: The ability to use a reverse pitch prop. Some electric stunt fliers don’t agree on this point. It is perhaps a personal thing, or perhaps an airplane specific thing. I believe that the reverse pitch prop gives me more line tension in outside and vertical maneuvers. Every time I’ve tried to switch back to a normal rotation prop I have found that I prefer the reverse pitch better. Being a fan of what I call “Obvious Physics,” The spiral airflow from a normal rotation propeller will eventually hit the inboard side of the vertical fin (rudder) and push it outward, and consequently push the nose inward. Because the fin is so far aft of the balance point of the model this yields what can best be described as a weathervane; it doesn’t take too much pressure on the left side of the fin to move the aft end of the plane outward and the nose inward. But, there’s more… Since most stunt models have a fin that has most of its area above the vertical CG, that spiral airflow when it hits the fin will also cause a left roll component. The reverse pitch prop addresses the yaw part of this very effectively in my opinion, but it has the opposite effect on the roll issue; it tends to make the model roll to the left. I’ve found two solutions to the roll issue; one years ago and by mistake! The Genesis models I flew in the early part of my career had very little vertical fin (dorsal) and also a lower fin (ventral). Those models didn’t seem to be affected so much by the spiral airflow issues because of the low profile of the fins and the fact that their areas were somewhat “balanced” top to bottom. I take no credit here for having that thought when I designed those models… But, I have found that addition of a ventral fin on my models that have an actual vertical fin has negated to a great degree the roll tendencies.
One last thing about the reverse pitch prop: In the past with normal pitch props I have noted that when flying in dead calm conditions when I hit my own turbulence, the model tended to roll towards me. With the reverse pitch props the model seems to always roll away from me, towards the outside of the circle. That has been comforting…
5: And really for me this could have been number 1… The ability to now make and fly reliable twin motor models with counter rotating props. When I was young I had a love affair with twins (airplanes that is…). I sketched a bunch of them but never actually tried to make one into a stunt model. Getting one glow engine to run consistently well was difficult enough; getting two to run consistently well seemed like a nightmare waiting to happen. To be fair here, there is one guy who had been able to make the glow twin a viable thing, and that is the “Twin Guru,” Gordan Delaney. My hat is off to him for that talent. In fact it was a flight on Gordan’s Pathfinder Profile Twin after a VSC that fully convinced me to go the twin route, only with electric power.
With a normal single engine/motor plane the largest diameter prop you are likely to use these days is 12-inch to maybe 13-inch. And, the spiral airflow from that prop is going around the fuselage and hitting the vertical fin as discussed above. With a twin the ability to use two nominally 10-inch diameter props yields a whole bunch more disc span. That means a lot more of the wing, flaps, stabilizer and elevators are covered with accelerated air. That means more lift. And none of that spiral air flow is going around the fuselage and hitting the vertical fin… With an electric twin you can also counter rotate the props (typically we run a standard direction prop on the inboard side and a reverse pitch prop on the inboard side. With electric, twins are easy (again, we are talking here about airplanes…).
6: The obvious stuff. Electric is quiet and clean. I can now fly at a field that is 1/4-mile from my house at 6 AM. That field is surrounded by homes, and no one even knows I’m there in the morning.
Electric has little to no vibration to weaken the airframe. Some have surmised that this is NOT a good thing as some electric models have shown a tendency to hunt in level flight, and that may be the byproduct of not enough vibration in the system to break the stiction of the controls. I’ve had one or two that exhibited this trait, but was able to trim it out successfully. Interestingly, none of the twins I and my friends have built for electric have shown any tendency to hunt. Perhaps the two motors set up just enough harmonic resonance to induce just enough vibration to break the stiction.
The timer allows an electric flier to do nominally 4 one minute, twenty second runs on one battery. That’s a big plus for initial trimming and handle setting; no need to fly a whole flight to make those adjustments.
My clothes and my car no longer smell of castor oil. Big plus when I want to sneak out and get a few flights while my wife is at work; she doesn’t even know I went out! Oh, rats, now she’ll know…
Add to the above that the new active timers are ever evolving with new features. Retracts are a cinch now, and an adjustable 2-4 break has become the norm. There are also features that add power when the nose is lifted (from upright or inverted flight), and even a G-Force feature that was a tremendous plus a couple of years ago at the Nats when it was extremely windy. Overhead and vertical tension was not a problem.
Finishes will last longer, and stress cracks are virtually a thing of the past with electric power.
And lastly, cost, or lack thereof. A gallon of glow fuel today is nominally priced between $25.00 and $30.00. The modern competition stunt model gets at most 20 flights per gallon (some of the larger displacement engines get significantly less than 20 flights per gallon). The batteries we have been using for the past several years can be purchased for nominally 50 to 70 dollars, but sometimes they have holiday specials at greatly reduced prices; most of us buy our batteries when one of those sales are on, and typically save 25 to 40 percent. So, let’s say the price of a battery is $60.00, or the same cost as two gallons of fuel. The minute you pass 40 flights on a battery the cost per flight as compared to glow begins to drop. Of course you will need more than one battery, but if you fly a lot, the cost per flight will eventually come down, and continue to drop over time. Treat your batteries well and they will last for years.
Factoring into the cost thing is an intangible for many fliers. If you have to travel a distance to a field at which glow can be flown without ticking off the neighbors with noise, the cost of gasoline for your car and the wear and tear can become a factor. Many have local fields that might be pressed into service if there was no noise issue. Just sayin’. Having said that, as my old friend, Dean Pappas always says, “There is only one hobby… Spending money!”
In closing this rather long missive, the bottom line is use what turns YOU on. Glow or electric; they each have their plusses and minuses. Pick what turns you on and have fun flying Stunt!
Bob Hunt