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Old 3rd February 2013, 01:15 PM   #241
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Originally Posted by TjW View Post
It might work that way. But I suspect that the pilot will be the least-optimized part of the helicopter, and that keeping the percentage of non-optimal parts to a minimum is the better strategy.
True, but I’m working on the perhaps deluded belief that the power output of my pilots will be more optimised than the currently used pedal-crank method.
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Old 3rd February 2013, 01:20 PM   #242
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Originally Posted by tsig View Post
Would you vary the angle of attack along the blade since the tip if the blade moves much faster than the base?
To get optimum performance? You'd have to.
And at these low velocities, the difference in Reynolds number from root to tip will be significant as well.
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Old 3rd February 2013, 01:25 PM   #243
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Originally Posted by Marcus View Post
Okay, but he better know how much combined power his athletes are going to be producing on the day.
I won't be waiting until “the day” to now that. I hope to be able to know that to a "satisfactory" degree even before I build the wings. It constant amazes me that people seem to build complete machines only to find out the component parts don't work. If my transmission system doesn’t provide enough power I will stop building and think of another approach or give up completely. I wouldn’t apply to win the prize until I had proven I could win it will successful prior testing.
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Old 3rd February 2013, 01:28 PM   #244
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Originally Posted by TjW View Post
To get optimum performance? You'd have to.
And at these low velocities, the difference in Reynolds number from root to tip will be significant as well.
Hope youíre still around if and when I get to building the wings
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Old 3rd February 2013, 01:34 PM   #245
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Thought my design would get more negative comments. Early days I guess
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Old 3rd February 2013, 01:36 PM   #246
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Originally Posted by AmishmanDan View Post
I know the feeling about the level of sharing details. I haven't wanted to share much until the day of public launch.
So if there's no day of public launch you will never share anything?
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Old 3rd February 2013, 01:41 PM   #247
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Originally Posted by TjW View Post
To get optimum performance? You'd have to.
And at these low velocities, the difference in Reynolds number from root to tip will be significant as well.
Have been thinking of active wing designs where the wing twists itself according to the pressure applied to it along it's length.
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Old 3rd February 2013, 01:43 PM   #248
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Old 3rd February 2013, 01:45 PM   #249
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Originally Posted by Marcus View Post
It really sounds like you are doing this by feel, so I guess you won't be collecting data about the power output of your pilots and using that to design the wings. So now I'm wondering, how are you going to design the wings?
By feel?
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Old 3rd February 2013, 01:59 PM   #250
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Originally Posted by dlorde View Post
By feel?
But not as blind a feel as braille
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Old 3rd February 2013, 02:02 PM   #251
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Originally Posted by ynot View Post
I won't be waiting until ďthe dayĒ to now that. I hope to be able to know that to a "satisfactory" degree even before I build the wings. I constant amazes me that people seem to build complete machines only to find out the component parts don't work. If my transmission system doesnít provide enough power I will stop building and think of another approach or give up completely. I wouldnít apply to win the prize until I had proven I could win it will successful prior testing.
It's good that you will be testing your pilots performance, presumably you will be using that information to build the wings. What I meant, though, is that there is a lot of variability to athletic performance, you won't know exactly how much power you will be getting on test day. In an ideal world the pilots would structure their training to be able to peak at test time, but that would probably be too much to ask. Because this feat is such a near thing, a 5% difference could spell the difference between success and failure.

I don't know the first thing about rowing, but if they have sprinters, that's what you will need. In both running and cycling the difference between sprinters and endurance specialists is pretty dramatic, with large differences in the percentages of fast twitch and slow twitch muscle fibers.
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Old 3rd February 2013, 02:06 PM   #252
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Originally Posted by dlorde View Post
By feel?
It wasn't sounding like he was planning simulations or testing, but he made it clear in a subsequent post that he will at least be testing the pilots power output.
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Old 3rd February 2013, 02:12 PM   #253
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Originally Posted by Marcus View Post
It's good that you will be testing your pilots performance, presumably you will be using that information to build the wings. What I meant, though, is that there is a lot of variability to athletic performance, you won't know exactly how much power you will be getting on test day. In an ideal world the pilots would structure their training to be able to peak at test time, but that would probably be too much to ask. Because this feat is such a near thing, a 5% difference could spell the difference between success and failure.

I don't know the first thing about rowing, but if they have sprinters, that's what you will need. In both running and cycling the difference between sprinters and endurance specialists is pretty dramatic, with large differences in the percentages of fast twitch and slow twitch muscle fibers.
Think a rowing action is one of the most powerful human energy actions (if not the most). Important to remember this is only a 60 second (plus a bit) effort and my pilots would be applying their power with a slower, more powerful action than pedalling a crank. More like pushing a car than pedalling a bike.
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Old 3rd February 2013, 02:13 PM   #254
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Originally Posted by Marcus View Post
It wasn't sounding like he was planning simulations or testing, but he made it clear in a subsequent post that he will at least be testing the pilots power output.
I will be testing every component part before it all comes together as an HPH.
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Old 3rd February 2013, 02:49 PM   #255
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Originally Posted by ynot View Post
Have been thinking of active wing designs where the wing twists itself according to the pressure applied to it along it's length.
Well, it will do that anyway. On something long and skinny, torsional stiffness is something you'll need to design for.

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I AGREE


Sailplane wings are generally way stronger than they need to be in bending, because they're designed to be stiff enough.

And of course, it doesn't have to be high speed flutter.
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I AGREE


You can make an airfoil that is stable (returns to a particular AOA) by reflexing the airfoil.
The thing is, such airfoils don't have high lift coefficients. Which leads to increasing the area, which means more structure, which means more weight, which requires more power.
Most airfoils have a reasonably broad L/D peak. I think I'd settle for designing for that peak, and just keeping torsional rigidity in mind during the design.

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Old 3rd February 2013, 04:14 PM   #256
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Originally Posted by TjW View Post
Well, it will do that anyway. On something long and skinny, torsional stiffness is something you'll need to design for.

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I AGREE


Sailplane wings are generally way stronger than they need to be in bending, because they're designed to be stiff enough.

And of course, it doesn't have to be high speed flutter.
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You can make an airfoil that is stable (returns to a particular AOA) by reflexing the airfoil.
The thing is, such airfoils don't have high lift coefficients. Which leads to increasing the area, which means more structure, which means more weight, which requires more power.
Most airfoils have a reasonably broad L/D peak. I think I'd settle for designing for that peak, and just keeping torsional rigidity in mind during the design.
You design the wings and I will build them
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Old 3rd February 2013, 06:30 PM   #257
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Originally Posted by ynot View Post
You design the wings and I will build them
I don't think that would work very well. For something like this to work, it has to be right on the hairy edge of breaking. So typically, it has to be designed very close to the edge, then iterated to make the stuff that broke stronger, and the stuff that didn't break lighter.

I've never tried to build that close to the edge. My aircraft have all used conventional approaches both as to aerodynamics and structure, and then proof-loading to the design limit. So they probably could have been lighter, but they were light enough and strong enough for my purposes.

I would feel really bad for someone else to spend their money on my ideas and have it not work. So please take anything I say with a grain of salt. Though I think they're pretty mainstream ideas, they're only my opinions. If all they do is point you in the direction of the real expert opinions, I'll be happy.

All the stuff I've been kibitzing about is just first-order considerations: stuff you need to look at before or while doing the back-of-the-envelope calculations.

I'm moderately interested in the problem, but having built stuff before, I know it isn't a project I would complete, so I'm unlikely to start it.
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Old 3rd February 2013, 06:50 PM   #258
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Originally Posted by TjW View Post
I don't think that would work very well. For something like this to work, it has to be right on the hairy edge of breaking. So typically, it has to be designed very close to the edge, then iterated to make the stuff that broke stronger, and the stuff that didn't break lighter.

I've never tried to build that close to the edge. My aircraft have all used conventional approaches both as to aerodynamics and structure, and then proof-loading to the design limit. So they probably could have been lighter, but they were light enough and strong enough for my purposes.

I would feel really bad for someone else to spend their money on my ideas and have it not work. So please take anything I say with a grain of salt. Though I think they're pretty mainstream ideas, they're only my opinions. If all they do is point you in the direction of the real expert opinions, I'll be happy.

All the stuff I've been kibitzing about is just first-order considerations: stuff you need to look at before or while doing the back-of-the-envelope calculations.

I'm moderately interested in the problem, but having built stuff before, I know it isn't a project I would complete, so I'm unlikely to start it.
You're too modest and I was mainly joking anyway. I've found your comments so far to be very informatiive and helpful so thanks again. As per your comment on AmDan's thread the internet is one of the best modern resource tools we have
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Old 4th February 2013, 11:46 AM   #259
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Has anybody looked into air-pressure stiffened rotor blades?
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Old 4th February 2013, 01:15 PM   #260
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Originally Posted by BenBurch View Post
Has anybody looked into air-pressure stiffened rotor blades?
I’ve questioned whether pressurising the tubes used for wing spars would stiffen them . . .
Originally Posted by ynot View Post
Could the structural integrity of a thin walled aluminium tube be strengthened by filling it with compressed air?
I’m also looking at ways of pre-stressing wings with compression rather than expansion.

What material do you imagine inflated rotor blades could be made of?
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Old 4th February 2013, 02:09 PM   #261
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The Atlas team are going to have another prize attempt on Feb 8 - http://www.aerovelo.com/2013/02/04/truss-modifications-for-friday-prize-attempt/

Don’t know why they have to have a prize attempt to test if they can win the prize. If they can’t achieve all conditions during pre-attempt testing why do they think they might be able to do so during a prize attempt? I still think this is more to do with publicity for fundraising than an actual attempt. Once again I don’t think they are “very, very close” but I wish them all the best and hope I’m proven wrong.
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Old 4th February 2013, 02:18 PM   #262
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Originally Posted by ynot View Post
The Atlas team are going to have another prize attempt on Feb 8 - http://www.aerovelo.com/2013/02/04/truss-modifications-for-friday-prize-attempt/

Donít know why they have to have a prize attempt to test if they can win the prize. If they canít achieve all conditions during pre-attempt testing why do they think they might be able to do so during a prize attempt? I still think this is more to do with publicity for fundraising than an actual attempt.
It may be that it takes them a lot of time and effort to set it up for a test and then disassemble it afterwards, and that every time they test it, there's a real chance of damaging or destroying it. If so, they might not want to do many (any!) unofficial flights.
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Old 4th February 2013, 02:29 PM   #263
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Originally Posted by dasmiller View Post
It may be that it takes them a lot of time and effort to set it up for a test and then disassemble it afterwards, and that every time they test it, there's a real chance of damaging or destroying it. If so, they might not want to do many (any!) unofficial flights.
But surley they need to test the completed craft to at least see if their modifications work or not.
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Old 8th February 2013, 01:44 PM   #264
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The Atlas team (AeroVelo) are currently conducting test flights for their AHS Sikorsky Prize attempt today. So far everything is apparently going ďgreatĒ.
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Old 8th February 2013, 02:51 PM   #265
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An interesting vid of the Gamera Teams progress to date - http://www.youtube.com/watch?feature...&v=MkZ2bTWvRns

Will be interesting to see what improvements Gamera III has
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Old 8th February 2013, 03:15 PM   #266
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Think the Atlas Team are just testing today as it doesn't seem to be an official AHS Sikorsky Prize attempt. No mention of it on the AHS site or that they are present at the "attempt".
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Old 9th February 2013, 01:44 PM   #267
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A few Tweets from the Atlas Team about how well their trim testing flights were going and then nothing further reported on Twitter or their website. I‘m sure any good news would have been quickly reported so I think it can be assumed that things didn‘t go as well as they hoped they would have.

I asked them if it was an official AHS Sikorsky Prize attempt or just testing but didn’t get a reply.

Wonder if the Gamera Team’s new improvements will take the prize before my backyard effort even gets off the drawing board . . .

“The team is currently designing a control system to remain within the required 10m x 10m box during flight, and that we will be flying in late winter/early spring 2013 with our sights set on the AHS Sikorsky Prize.” - http://www.agrc.umd.edu/gamera/index.html
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Old 9th February 2013, 07:05 PM   #268
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Originally Posted by ynot View Post
A few Tweets from the Atlas Team about how well their trim testing flights were going and then nothing further reported on Twitter or their website. IĎm sure any good news would have been quickly reported so I think it can be assumed that things didnĎt go as well as they hoped they would have.

I asked them if it was an official AHS Sikorsky Prize attempt or just testing but didnít get a reply.

Wonder if the Gamera Teamís new improvements will take the prize before my backyard effort even gets off the drawing board . . .

ďThe team is currently designing a control system to remain within the required 10m x 10m box during flight, and that we will be flying in late winter/early spring 2013 with our sights set on the AHS Sikorsky Prize.Ē - http://www.agrc.umd.edu/gamera/index.html
Thanks for the updates on the teams. Reading your replies are better than signing up for a twitter.

Wait!?! You are only still at the drawing board?? It seems that it is easier to talk about building something than attempting to build it, let alone actually building it.
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Old 9th February 2013, 09:32 PM   #269
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Originally Posted by AmishmanDan View Post
Thanks for the updates on the teams. Reading your replies are better than signing up for a twitter.
Never thought I would sign up to Twitter and only did so to follow the Atlas attempt.

Originally Posted by AmishmanDan View Post
Wait!?! You are only still at the drawing board?? It seems that it is easier to talk about building something than attempting to build it, let alone actually building it.
I've only been at this for about five weeks so have hardly had much time to do much beyond the drawing board. Have built quite a few models and full sized test components in that time however. Spent most of today building part of what will become a full sized HPH for test pusposes. It's not being built for flying purposes so not too concerned with weight in this build.

But I agree that talk is cheap and easy. Trouble is talk is all you have given us so far. At least I've given a few concept drawings and word descriptions. How about you do at least that much so we know you're more than just talk.
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Old 9th February 2013, 11:18 PM   #270
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Originally Posted by ynot View Post
I've only been at this for about five weeks so have hardly had much time to do much beyond the drawing board. Have built quite a few models and full sized test components in that time however. Spent most of today building part of what will become a full sized HPH for test pusposes. It's not being built for flying purposes so not too concerned with weight in this build.
Good for you! I am glad that you are striving to achieve your goal. I hope that your project brings you success.

Originally Posted by ynot View Post
But I agree that talk is cheap and easy. Trouble is talk is all you have given us so far. At least I've given a few concept drawings and word descriptions. How about you do at least that much so we know you're more than just talk.
Is it important that you know that I am more than just talk? Would a picture or a video lessen the cynical, (not to be confused with skeptical) comments? My purpose in sharing my project was not to win you over, nor to ask your opinion or even to provide conclusive evidence that I indeed, am more than talk.

I am a bit fragile and certain that I couldn't handle the harsh and hurtful words that most certainly would follow. Some people assume that I am unsure about the definition or proper use of the word efficient, I am unable to imagine what would be said about IGOR. Since I don't have any 'mates' or a team of engineers to assist me, I rely on encouragement and positive feedback to give me added strength to continue striving towards my goal. Sharing my project on a limited basis has aided me in learning to relate to people, reminded me to keep my guard up and has hardened my idealistic resolve to make the most out of what I am and what I have.
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Old 10th February 2013, 12:51 AM   #271
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Originally Posted by AmishmanDan View Post
Is it important that you know that I am more than just talk? Would a picture or a video lessen the cynical, (not to be confused with skeptical) comments? My purpose in sharing my project was not to win you over, nor to ask your opinion or even to provide conclusive evidence that I indeed, am more than talk.
Not overly important to me and I'm happy to believe that you have at least built something. Your post seemed to be saying that I was all talk and I was saying in reply that, that would be more applicable to you than me.

But you haven't shared your project at all, you have merely shared your story and dream of your project.

Originally Posted by AmishmanDan View Post
I am a bit fragile and certain that I couldn't handle the harsh and hurtful words that most certainly would follow. Some people assume that I am unsure about the definition or proper use of the word efficient, I am unable to imagine what would be said about IGOR. Since I don't have any 'mates' or a team of engineers to assist me, I rely on encouragement and positive feedback to give me added strength to continue striving towards my goal. Sharing my project on a limited basis has aided me in learning to relate to people, reminded me to keep my guard up and has hardened my idealistic resolve to make the most out of what I am and what I have.
However unpaletable it sometimes may be the truth is far more positive than false positive feedback. There's nothing positive about denying reality or being lied to, especially by yourself.

Repeat of two of my favourite positive sayings . . .

"A positive attitude is often the last refuge of failure"

"If to make it happen you have to believe, then it's make believe"
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Old 10th February 2013, 12:57 AM   #272
rjh01
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On the edge of modern aircraft wings are small wing lets to reduce air turbulence. I wonder if these can be added on the wings of the helicopter for the same reason.
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Old 10th February 2013, 06:56 AM   #273
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Originally Posted by rjh01 View Post
On the edge of modern aircraft wings are small wing lets to reduce air turbulence. I wonder if these can be added on the wings of the helicopter for the same reason.
Great thinking!!

(Phys.org)ó"An airplane's vortex generators, which look like small fins on its surface, improve the plane's aerodynamics similar to the way in which the dimples on a golf ball improve the ball's aerodynamics: by delaying "boundary layer separation." While this mechanism is widely known, a new study has shown that vortex generators can improve a plane's aerodynamics in a second way, and the researchers demonstrate this way in a wind tunnel for the first time."

"One advantage of using vortex generators to delay the transition to turbulence is that the mechanism is entirely passive, so it doesn't require the addition of extra energy into the system."

"The controllable streak amplitude, which is a function of the MVG height among other things, and the fact that the streaks are very robust in terms of stability, gives the method the potential to be used in real applications," Talamelli said. "It can be applied to aerodynamic bodies, which are mainly interested by reducing the skin-friction drag."

Read more at: http://phys.org/news/2012-09-scienti...ortex.html#jCp

Control the flow of air, achieving maximum productivity of the system with minimum wasted effort or expense.
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Old 10th February 2013, 07:42 AM   #274
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Originally Posted by ynot View Post
However unpaletable it sometimes may be the truth is far more positive than false positive feedback. There's nothing positive about denying reality or being lied to, especially by yourself.
Does truth need to be draped with a spirit? If someone asked me a question, I can answer with a very true statement, that is mean spirited. I can also offer unsolicited truth that is mean spirited.

Denying reality is not the same as filtering reality. Truth is often packaged within opinion.
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Old 10th February 2013, 07:52 AM   #275
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Originally Posted by ynot View Post
Your post seemed to be saying that I was all talk and I was saying in reply that, that would be more applicable to you than me.

But you haven't shared your project at all, you have merely shared your story and dream of your project.
Talking about doing something, attempting to do something, and doing something applies to us all. It is equally applicable to you or me. Four different scenarios.

1. Amishman Dan/IGOR - Five years of talk, study and attempting. Two years building and attempting; very little talk with no shows. One thread; all talk and no show.
2. AeroVelo/Atlas - Multiple years of study. Years and multiple projects of doing. Two years building, lots of talk and still attempting.
3. UMaryland/Gamera - Ideal example of idea becomes a study, multiple attempts, doing, more attempts, more doing...
4. Jarno Smeets (AKA)Floris Kaayk/ ďHuman BirdwingsĒ An online adventure and invention story in which wings were developed in a do-it-yourself manner. A lot of talk and "proof of doing".

Of the four, the "Human Birdwings" was the most talked about and contained a false positive reality. If you have to see it to believe that it happened, don't bother believing in it. It can been seen and not happen. Hopes and visions are often better than reality.
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Old 10th February 2013, 08:08 AM   #276
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Originally Posted by rjh01 View Post
On the edge of modern aircraft wings are small wing lets to reduce air turbulence. I wonder if these can be added on the wings of the helicopter for the same reason.
I'm sure winglets could help, but an actual increase in span is more effective at reducing drag than a winglet of similar height.
Gamera seems to have gotten the power requirements down to a manageable level.
Now they need to keep it from wandering out of the box.
It will be interesting to see how they approach the control problem.
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Old 10th February 2013, 12:28 PM   #277
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The Atlas had structural failure as I suspected - "After many trimming flights, we started began testing the controls, but unfortunately upon full actuation the blades were thrown out of balance and a rotor ended up striking a line and snapping a spar."

More here - http://www.aerovelo.com/2013/02/10/t...light-testing/
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Old 10th February 2013, 01:28 PM   #278
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Originally Posted by AmishmanDan View Post
Does truth need to be draped with a spirit? If someone asked me a question, I can answer with a very true statement, that is mean spirited. I can also offer unsolicited truth that is mean spirited.

Denying reality is not the same as filtering reality. Truth is often packaged within opinion.
Truth (reality) is independent of emotions. How much we consider emotions in presenting truth is up to the individual and is usually “filtered” according to the subject matter being discussed. We’re discussing an inanimate piece of machinery here, not exactly a subject that normally needs to be “draped” in emotion. That you have made your HPH project more emotional than intellectual is your choice, but don’t expect others to adopt or share your choice.
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Last edited by ynot; 10th February 2013 at 01:56 PM.
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Old 10th February 2013, 01:30 PM   #279
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Originally Posted by AmishmanDan View Post
Hopes and visions are often better than reality.
Only if youíre pandering to your emotions.
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Old 10th February 2013, 01:36 PM   #280
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Originally Posted by TjW View Post
I'm sure winglets could help, but an actual increase in span is more effective at reducing drag than a winglet of similar height.
Gamera seems to have gotten the power requirements down to a manageable level.
Now they need to keep it from wandering out of the box.
It will be interesting to see how they approach the control problem.
The Gamera Team claim that extending their wings (about a metre or less I think) “reduced power requirement by 12%”.
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