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#11
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Another E glider concept
The chines are improve handling at Mach 3.Â* Don't you remember the SR-71?
And didn't the ending credits say that it was a Master's Thesis in design or something similar? On 8/17/2020 5:40 AM, Martin Gregorie wrote: On Sun, 16 Aug 2020 20:04:19 -0700, Marc Ramsey wrote: On Sunday, August 16, 2020 at 6:19:27 PM UTC-7, wrote: If you mean the fins on either side of the nose clearly marked "sensor", likely angle of attack vanes. Not very useful when the motor is running... Not thinking about the sensor fin. at 0:25 in the video. The horizontal line mid screen a few inches below the canopy. Looks like a transition between a flatish underbelly and vertical cockpit upper side. Looks like the chines under a boat? I see what you mean, the odd transition between the upper and lower fuselage profile that extends to the tail. Perhaps structural, or for style? I find it hard to believe it does much for the aerodynamics except produce a bit of drag. Graphical artifact? In the top view just from the right it looks as though it sticks out as far as the sensor does and is blurred, while from the top left it only seems to extend a cm or so and in other views it just looks like a blurred line along the fuselage. -- Dan, 5J |
#12
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Another E glider concept
Ventus_a wrote on 8/16/2020 6:14 PM:
Jonathan St. Cloud;1027640 Wrote: https://www.youtube.com/watch?v=ZIYU2zkGQFQ Interesting concept although on first look got to wonder if he was dreaming of an updated, stretched and powered 2 seat Salto that could fly him to fame and fortune (just kidding about the fortune) I hope someone will read the thesis and tell us the goal of the concept. It does make me wonder if the current FES could be adapted to a three blade propeller, with all blades external as they are now. Slightly higher drag when gliding, but a 50% increase in power capability by the propeller (or more ground clearance and some power increase). -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#13
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Another E glider concept
The Main factors for power from a propeller are diameter, pitch and rpm, not the number of blades.
An increase from 2 to 3 blades gives at best about 10-15% more drag if the remaining is constant. However the efficiency of the propeller drops by 5-10% and this is a major drawback in electrical propulsion system for gliders. |
#14
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Another E glider concept
Per Carlin wrote on 8/17/2020 12:58 PM:
The Main factors for power from a propeller are diameter, pitch and rpm, not the number of blades. An increase from 2 to 3 blades gives at best about 10-15% more drag if the remaining is constant. However the efficiency of the propeller drops by 5-10% and this is a major drawback in electrical propulsion system for gliders. I think something is missing in your explanation: for example, 3, 4 and 5 blades are common on airplanes, and wind turbines routinely use 3 blades. My understanding is tip speed is the ultimate limit on the power a propeller can absorb, so adding a 3rd should 50% more power capability. Take a look at this bad boy - Five blades! https://hartzellprop.com/are-more-pr...blades-better/ The Hartzell site also discusses reasons for choosing more blades -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#15
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Another E glider concept
When the propeller spins backwards in the demo reel, confidence that the engineers will make an airworthy aircraft is instantly flushed down the toilet.
On Monday, August 17, 2020 at 1:39:31 PM UTC-7, Eric Greenwell wrote: Per Carlin wrote on 8/17/2020 12:58 PM: The Main factors for power from a propeller are diameter, pitch and rpm, not the number of blades. An increase from 2 to 3 blades gives at best about 10-15% more drag if the remaining is constant. However the efficiency of the propeller drops by 5-10% and this is a major drawback in electrical propulsion system for gliders. I think something is missing in your explanation: for example, 3, 4 and 5 blades are common on airplanes, and wind turbines routinely use 3 blades. My understanding is tip speed is the ultimate limit on the power a propeller can absorb, so adding a 3rd should 50% more power capability. Take a look at this bad boy - Five blades! https://hartzellprop.com/are-more-pr...blades-better/ The Hartzell site also discusses reasons for choosing more blades -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#16
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Another E glider concept
On Monday, August 17, 2020 at 8:01:08 PM UTC-4, Cumungus wrote:
When the propeller spins backwards in the demo reel, confidence that the engineers will make an airworthy aircraft is instantly flushed down the toilet. That feature is for backing into your parking space. |
#17
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Another E glider concept
It looks like this is a masters thesis project for a curriculum in industrial design. Of course, much of it is not functional in the ways that are important to soaring flight. But there are some interesting design concepts here that we should not dismiss out of hand.
We have to be careful about rejecting ideas that seem impractical, especially when advances in various technologies can be combined in ways that make the orthodoxy irrelevant. The next time you find yourself yelling "get off my lawn!," stop and reflect whether the lawn is really yours. --Bob K. |
#18
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Another E glider concept
On Tuesday, August 18, 2020 at 6:42:12 PM UTC-7, Bob Kuykendall wrote:
It looks like this is a masters thesis project for a curriculum in industrial design. Of course, much of it is not functional in the ways that are important to soaring flight. But there are some interesting design concepts here that we should not dismiss out of hand. We have to be careful about rejecting ideas that seem impractical, especially when advances in various technologies can be combined in ways that make the orthodoxy irrelevant. The next time you find yourself yelling "get off my lawn!," stop and reflect whether the lawn is really yours. --Bob K. Don't confuse this with a real, aerodynamical design concept, because it is not. You will end up chasing your tail if you do. |
#19
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Another E glider concept
On Tuesday, August 18, 2020 at 3:01:45 AM UTC+2, Dave Nadler wrote:
On Monday, August 17, 2020 at 8:01:08 PM UTC-4, Cumungus wrote: When the propeller spins backwards in the demo reel, confidence that the engineers will make an airworthy aircraft is instantly flushed down the toilet. That feature is for backing into your parking space. Or for landing downwind on golf courses.. |
#20
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Another E glider concept
Chris Wedgwood wrote on 8/19/2020 7:33 AM:
On Tuesday, August 18, 2020 at 3:01:45 AM UTC+2, Dave Nadler wrote: On Monday, August 17, 2020 at 8:01:08 PM UTC-4, Cumungus wrote: When the propeller spins backwards in the demo reel, confidence that the engineers will make an airworthy aircraft is instantly flushed down the toilet. That feature is for backing into your parking space. Or for landing downwind on golf courses.. That's an interesting idea, sort of the modern tail parachute like I had on my H301. It was enormously powerful, but not controllable, just deployed or not. An electrically powered propeller could be used to provide adjustable drag from zero to "a lot". The design issue is keeping the propeller from folding backwards when you want it to produce drag. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
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