frank marriott Posted December 8, 2015 Share Posted December 8, 2015 And does electicity flow -ve to +ve or vice versa Depends on whether you are talking electron flow or convential current flow. Electron flow is easier to explain the workings of a valve but they are getting few and far between. Link to comment Share on other sites More sharing options...
facthunter Posted December 8, 2015 Share Posted December 8, 2015 winglets are like that to fit in hangars. Nev 1 3 Link to comment Share on other sites More sharing options...
spacesailor Posted December 8, 2015 Share Posted December 8, 2015 IBOB There's no such thing in Europe as "30 cm" It's 3 dm JTJR do you mean it's Elliptical at the outer end of the wing span, Or the vertical winglet is elliptical? The ChirPaa (aeromodler plans ) of the 1950's used washout plus elliptical ends to its high lift rib profiles to gain stability to it's Tailless design, (No stabiliser). Winglets were to Shorten the jumbo's wings for use on Normal runways spacesailor Link to comment Share on other sites More sharing options...
djpacro Posted December 8, 2015 Share Posted December 8, 2015 These notes about Spillman's work may help explain the thrust extracted from some surfaces. https://books.google.com.au/books?id=X4pkFU-iRD0C&pg=PA146&lpg=PA146&dq=spillman+sails&source=bl&ots=t63ZlVF0Ol&sig=kB8NZL9whQgRIXIs6qqRpZo1wr4&hl=en&sa=X&ved=0ahUKEwjp_8mrzMvJAhUDiKYKHSRaCpcQ6AEIJTAB#v=onepage&q=spillman%20sails&f=false I also find it helps to stop talking about suction (or, worse still, 'negative pressure'). There is no such thing .... Like many things we can change the datum and it is actually quite useful to talk about negative pressure wrt aeroplanes because the static pressure on the upper surface of the wing (in normal flight) will be less than the static pressure inside the cabin of the aeroplane. Static pressure under the wing will likewise be higher than pressure inside the cabin. So, it all depends on your frame of reference - sitting inside the cabin if you put a tube into the wing connected to a hole on the upper surface near the leading edge - put the other end into your mouth - you will feel the suction.Reminds me of a test I as asked to witness many years ago - the engineer connected a manometer up something like that tube - whoooosh - all the fluid was sucked out. He turned and looked to me, disbelieving what he had just seen. You need a suction gauge, I said. He was a mechanical engineer. 1 Link to comment Share on other sites More sharing options...
IBob Posted December 8, 2015 Share Posted December 8, 2015 These notes about Spillman's work may help explain the thrust extracted from some surfaces. https://books.google.com.au/books?id=X4pkFU-iRD0C&pg=PA146&lpg=PA146&dq=spillman+sails&source=bl&ots=t63ZlVF0Ol&sig=kB8NZL9whQgRIXIs6qqRpZo1wr4&hl=en&sa=X&ved=0ahUKEwjp_8mrzMvJAhUDiKYKHSRaCpcQ6AEIJTAB#v=onepage&q=spillman sails&f=falseLike many things we can change the datum and it is actually quite useful to talk about negative pressure wrt aeroplanes because the static pressure on the upper surface of the wing (in normal flight) will be less than the static pressure inside the cabin of the aeroplane. Static pressure under the wing will likewise be higher than pressure inside the cabin. So, it all depends on your frame of reference - sitting inside the cabin if you put a tube into the wing connected to a hole on the upper surface near the leading edge - put the other end into your mouth - you will feel the suction. Reminds me of a test I as asked to witness many years ago - the engineer connected a manometer up something like that tube - whoooosh - all the fluid was sucked out. He turned and looked to me, disbelieving what he had just seen. You need a suction gauge, I said. He was a mechanical engineer. M...well, where you feel suction in your mouth, I feel the lower pressure in the tube. Not negative, just lower. And where you see fluid sucked out, I see it pushed out by pressure on the high side. I suppose I find it simpler to think and work in absolute pressures. But I'm not suggesting that implies everyone should see it so. Bob Link to comment Share on other sites More sharing options...
Mike Borgelt Posted December 8, 2015 Share Posted December 8, 2015 I do refrigeration controls, amongst other things. And the industrial guys have mostly made it to kiloPascals (kPa) but the freon guys are still talking PSI.I find it easiest to relate it all back to one standard atmospheric pressure, which is: 14.7PSI 1Bar 100kPa 30ft or 10metres of water 30cm mercury Well, not exactly, but close enough for government work! I also find it helps to stop talking about suction (or, worse still, 'negative pressure'). There is no such thing, there are just degrees of pressure, starting with zero at total vacuum and working on up. By the same token, nothing is ever sucked, it's all blown by the great pressure on the other side. Okay, this is basic practical stuff for the layman (and I don't claim to be anything else). I find it helps in my day to day practical work. Oh, and while we're on it (not that we were, but I'm away now) there is no such thing as darkness, either...just different amounts of light. Okay, i'll stop now.......... I do refrigeration controls, amongst other things. And the industrial guys have mostly made it to kiloPascals (kPa) but the freon guys are still talking PSI.I find it easiest to relate it all back to one standard atmospheric pressure, which is: 14.7PSI 1Bar 100kPa 30ft or 10metres of water 30cm mercury Well, not exactly, but close enough for government work! I also find it helps to stop talking about suction (or, worse still, 'negative pressure'). There is no such thing, there are just degrees of pressure, starting with zero at total vacuum and working on up. By the same token, nothing is ever sucked, it's all blown by the great pressure on the other side. Okay, this is basic practical stuff for the layman (and I don't claim to be anything else). I find it helps in my day to day practical work. Oh, and while we're on it (not that we were, but I'm away now) there is no such thing as darkness, either...just different amounts of light. Okay, i'll stop now.......... Try 76 cm of mercury or 760mm for one atmosphere. The Russians used to set their altimeters in mm of Hg. Link to comment Share on other sites More sharing options...
IBob Posted December 8, 2015 Share Posted December 8, 2015 Try 76 cm of mercury or 760mm for one atmosphere. The Russians used to set their altimeters in mm of Hg. Ops, my mistake, thanks Mike. The specific gravity of mercury being 13 point something and all that. Clearly parts grow rusty with disuse....( Link to comment Share on other sites More sharing options...
ayavner Posted December 8, 2015 Share Posted December 8, 2015 4 1 2 Link to comment Share on other sites More sharing options...
RickH Posted December 9, 2015 Share Posted December 9, 2015 The change of direction is caused by the airflow turning around the curve of the wing, or deflecting off the lower side, if you believe that theory.There would be no need for any pressure changes to occur, to uphold this theory. On the other hand, if it's all done with pressure changes as generated by making air travel over dissimilar distances, then lift can be created without the need of angle of attack. In fact lift can be created with zero angle of attack or as aerodynamicists say zero alpha and in fact certain airfoils will generate positive lift with negative angle of attack. and any one who says it is not down to the various laws of physics such as Newton Bernoulli simply does not what he is talking about. Link to comment Share on other sites More sharing options...
fly_tornado Posted December 10, 2015 Share Posted December 10, 2015 which aircraft can fly with a negative angle of attack? Link to comment Share on other sites More sharing options...
pylon500 Posted December 10, 2015 Share Posted December 10, 2015 certain airfoils will generate positive lift with negative angle of attack Basically what I was getting at. I was going to ad some diagrams (but went and had tea instead) Here ya go.....; The bottom surface of the old Clark Y section can have a negative angle (I know, irrelevant) while producing lift, in fact at high speeds even the chord line can be at a negative AoA, and still producing lift! The above polar is for some variations of the Clark Y section, hence the different colour plots. (I just pinched this off the net without reading too much..) The horizontal plot line above is AoA, while the vertical line is the lift coefficient. You can see that at 0° AoA, the wing is still producing about 45% of it's capable lift. Yes, the aircraft would be descending, but it IS flying, not plummeting out of the sky. which aircraft can fly with a negative angle of attack? Most gliders..... Link to comment Share on other sites More sharing options...
facthunter Posted December 10, 2015 Share Posted December 10, 2015 The zero lift line on most assymetric aerofoils is a negative AoA.. Nev 2 Link to comment Share on other sites More sharing options...
facthunter Posted December 10, 2015 Share Posted December 10, 2015 Once you are flying level (cruising) particularly at low level and cold days you have far more lift than you need and your wing won't be efficient as it's not at it's best lift drag angle. You can save fuel in this condition by flying slower, at a lower power setting. Head and tail winds come into this too but that's another story. Nev. Link to comment Share on other sites More sharing options...
RickH Posted December 11, 2015 Share Posted December 11, 2015 If you re- read my post You may note I stated Airfoil. And I would suggest you go and some research on basic aerodynamics so that you may avoid making a fool of yourself before continuing to argue any further on the matter. Link to comment Share on other sites More sharing options...
facthunter Posted December 11, 2015 Share Posted December 11, 2015 RickH for clarity, may I ask who you are referring to?. Nev 1 Link to comment Share on other sites More sharing options...
spacesailor Posted December 11, 2015 Share Posted December 11, 2015 I'll give it a go: an aircraft that fly's with Negative angle of attack AND Zero wing loading. the "SPACESHUTTLE" Even fly's sideways spacesailor Link to comment Share on other sites More sharing options...
facthunter Posted December 11, 2015 Share Posted December 11, 2015 I asked WHO Not WHAT. Nev Link to comment Share on other sites More sharing options...
2tonne Posted December 11, 2015 Share Posted December 11, 2015 I asked WHO Not WHAT. Nev Nev, it appears you are responding to a comment from Spacesailor having yourself responded to Rick about it not being clear who he responded to. I believe Spacesailor was responding to a question posed earlier, perhaps by FT about which aircraft fly with a negative angle of attack. I may have got that somewhat confused though. 1 Link to comment Share on other sites More sharing options...
facthunter Posted December 11, 2015 Share Posted December 11, 2015 2t, I'm confused too That's why I asked. Thanks. Nev Link to comment Share on other sites More sharing options...
spacesailor Posted December 11, 2015 Share Posted December 11, 2015 I was/is confused when reading aviation lawyer speak in all the litterateur (if that's spelled write LoL) spacesailor P.S, Why the Y in an airfield address, The A would make more sense. Link to comment Share on other sites More sharing options...
facthunter Posted December 11, 2015 Share Posted December 11, 2015 I don't see any need to use it here as many aerodromes we use aren't classified. You aren't submitting a flight plan. It's Sydney Kingsford Smith or Bankstown etc as far as I'm concerned. Nev 1 Link to comment Share on other sites More sharing options...
pylon500 Posted December 11, 2015 Share Posted December 11, 2015 Bankstown and or Kingsford Smith? Never heard of those airfoils, now I'm confused. 1 Link to comment Share on other sites More sharing options...
turboplanner Posted December 11, 2015 Share Posted December 11, 2015 Hit the reply button in the box of the person you are commenting about, and then everyone knows who you were referring to. 1 1 Link to comment Share on other sites More sharing options...
pmccarthy Posted December 11, 2015 Share Posted December 11, 2015 I'm so confused now I can't eat my muesli. Link to comment Share on other sites More sharing options...
IBob Posted December 11, 2015 Share Posted December 11, 2015 half cup of rolled oats, add milk or water to soak when you first get up sprinkle with pumpkin & sunflower seeds, add diced dry fruit (I use pears) top off with yoghurt doesn't reduce the confusion, but it's a pleasing daily distraction from it... 1 Link to comment Share on other sites More sharing options...
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