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#151
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Electrically Powered Ultralight Aircraft
Charles Vincent wrote:
cavelamb himself wrote: Don't be snotty, Charles. Since the subject is an electrically powered aircraft, the weight issue is not trivial. That's been my issue with this thread from the start. The constraints given here were to fly at the same speed and altitude but at a higher weright. You can increase lift via increased angle of attack only as far as CLmax. No Farther. (You seem to have that part right) Beyond that any increased weight will require increased wing area. Aspect ratio alone won't answer is most cases. And - an electric powered plane would NOT lose weight in flight. No electrons are "consumed" - no change in battery weight. Not really being snotty at all. Frankly, I was in the process of deleting screenfulls of messages on the topic of electric powered airplanes being as the subject really holds no interest for me. For some reason I happened to read "The advantage from the electric engine at cruise is that it uses zero energy" on one message just as I deleted it. Pulling it back from the trash, I felt compelled to respond to it. My mistake. For some reason you are in turn compelled to nit pick my correct assertion because it did not completely cover the relevant aerodynamic theory. In my opinion, it covered enough, but not following the thread, I have no idea what sort of debate has been raging. As I stated elsewhere, I just didn't expect that information required for even the most basic pilot ticket would be the subject of any debate here. In the end, to fly at the same speed and altitude but at a higher weight requires more power be applied, whether you use that power to drag the same wing at a higher angle of attack or a bigger wing doesn't change that. Or you could use more power to drag the wing at a higher speed to generate the lift you needed. All of this ignores the fact that for internal combustion aircraft powerplants, the weight per HP goes down as the power goes up. Last time I looked at it, the opposite is true of electric motors. I don't think an electric assist for an IC engine is going to be viable for aircraft in the near future. Charles I guess I was just over reacting to the swing wing parasol comment. And yes, I can see your point. Higher Cl - or bigger wing. Either will require more power. Which was my point as well. Yep. A lot of this thread has been - well - fanciful? Richard |
#152
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Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Charles Vincent wrote:
cavelamb himself wrote: Not really being snotty at all. Frankly, I was in the process of deleting screenfulls of messages on the topic of electric powered airplanes being as the subject really holds no interest for me. For some reason I happened to read "The advantage from the electric engine at cruise is that it uses zero energy" on one message just as I deleted it. Pulling it back from the trash, I felt compelled to respond to it. Have either of you guys heard of the term "thread drift"? Both of you are responding to the part of the thread that drifted off to the topic of hybrid CARS and how they get good mileage. -- Jim Pennino Remove .spam.sux to reply. |
#153
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Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Morgans wrote:
wrote Unless the added weight is enough to deform the tires, the increase in rolling resistance in the total energy expediture can't be found. Bull hockey. Just because it is not noticeable, or measurable by the lack of sensitivity with the instrument you are currently not using, does not mean that it does not exist. Perhaps you would like a rephrase: Unless the added weight is enough to deform the tires, the increase in rolling resistance compared to the total system energy expediture is so small that it is negligible. Or how about: Unless the added weight is enough to deform the tires, the increase in rolling resistance compared to the total system energy expediture has about the same effect as ****ing in Lake Tahoe. -- Jim Pennino Remove .spam.sux to reply. |
#154
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Electrically Powered Ultralight Aircraft
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#155
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Electrically Powered Ultralight Aircraft
Morgans wrote:
wrote Unless the added weight is enough to deform the tires, the increase in rolling resistance in the total energy expediture can't be found. Bull hockey. Just because it is not noticeable, or measurable by the lack of sensitivity with the instrument you are currently not using, does not mean that it does not exist. More weight on the bearings will cause more rolling resistance. That is fact, not open to dispute. If you say it is, I want to buy the rights to the bearings you are using, so I can patent them and make a fortune. If a bird craps on your windshield, it is more likely to noticeably influence your aerodynamic drag than rolling resistance.....I took Jim's "can't be found" to mean lost in the noise. According to SAE studies, aerodynamic drag accounts for 60% of the resistance that must be overcome for highway cruise, with tires being 25% and driveline friction making up the last 15%. I suspect an electric motor and associated batteries however, are going to deform the tires. The power companies that I work with are doing studies on a number of electric vehicles. I have been told that they run some interesting tires and pressures. Charles |
#156
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Electrically Powered Ultralight Aircraft
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#158
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Electrically Powered Ultralight Aircraft
"Charles Vincent" wrote: Just because it is not noticeable, or measurable by the lack of sensitivity with the instrument you are currently not using, does not mean that it does not exist. More weight on the bearings will cause more rolling resistance. That is fact, not open to dispute. If you say it is, I want to buy the rights to the bearings you are using, so I can patent them and make a fortune. If a bird craps on your windshield, it is more likely to noticeably influence your aerodynamic drag than rolling resistance.....I took Jim's "can't be found" to mean lost in the noise. According to SAE studies, aerodynamic drag accounts for 60% of the resistance that must be overcome for highway cruise, with tires being 25% and driveline friction making up the last 15%. Pardon the intrusion on this interesting discussion, but just how *does* added weight in a car impose extra load on the powerplant besides via bearing friction and tire deformation? Added weight means the powerplant is doing more work to maintain the same speed; there's no way around it, the laws of physics demand it. So where's the extra power going? -- Dan T-182T at BFM |
#159
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Electrically Powered Ultralight Aircraft
Dan Luke wrote:
"Charles Vincent" wrote: Just because it is not noticeable, or measurable by the lack of sensitivity with the instrument you are currently not using, does not mean that it does not exist. More weight on the bearings will cause more rolling resistance. That is fact, not open to dispute. If you say it is, I want to buy the rights to the bearings you are using, so I can patent them and make a fortune. If a bird craps on your windshield, it is more likely to noticeably influence your aerodynamic drag than rolling resistance.....I took Jim's "can't be found" to mean lost in the noise. According to SAE studies, aerodynamic drag accounts for 60% of the resistance that must be overcome for highway cruise, with tires being 25% and driveline friction making up the last 15%. Pardon the intrusion on this interesting discussion, but just how *does* added weight in a car impose extra load on the powerplant besides via bearing friction and tire deformation? Added weight means the powerplant is doing more work to maintain the same speed; there's no way around it, the laws of physics demand it. So where's the extra power going? To accellerate... |
#160
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Electrically Powered Ultralight Aircraft
On Aug 17, 2:19 pm, "Morgans" wrote:
"Phil" wrote IF these can be made practical, they sound ideal for use in an airplane. They are light, and they can be shaped in just about any way to fit inside the airframe. Suppose they were integrated into the airframe and wings such that a large percentage of the airplane consisted of battery. It might be possible to get enough capacity there for a practical general aviation electric plane. I can see the headlines, now. Plane (or car) crashes, and the car's structure electrocutes the occupants. g -- Jim in NC I know you're only half serious, but yes, that would have to be considered. That's a risk in hybrid autos as well. EMTs and firefighters are taking special training to handle the wrecks of these cars. And the gasoline we use for our current airplanes poses the risk of incinerating the occupants in a crash. I am not sure that an electric plane would actually pose more risk. I would think that the increased reliability of the propulsion system would decrease the risk overall. How many people are killed every year in crashes caused by engine failures? |
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