If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#51
|
|||
|
|||
Alan Baker Edict: No more Suction References (was visualizationof the lift distribution...)
Alan Baker wrote:
No one understands "suction" to actually mean a pulling force. Remember folks: no more talk of sucking soda through a straw! Just suck it up! ... don't pretend that there is a force acting upward on the surface of the liquid inside the straw... ...because you'll be wrong. You still don't get it Alan. This level of attention to minutiae is impressive in Junior High science classes, and paradoxically is quite correct but trivial. Get over it. Just so you can savor the general idea - let me phrase the general concept so it won't trip your OC reaction: In the general case, two thirds of the lift provided by a wing is due to the depression over the upper surface - (actually towards the front...) and a third due to the air flow over the lower surface. THERE. Are you happy now? Brian W |
#52
|
|||
|
|||
visualisation of the lift distribution over a wing
On Nov 30, 12:19 am, Alan Baker wrote:
Nope. I'm making the point that the upper surface contributes absolutely *no* lifting force. None. Zero. In fact, it provides a downward force. Every time. Sorry, Alan, old boy, I find must disagree. Disagree all you want, it won't make the upper surface of the wing experience anything but a downward force. In actuality, BOTH surfaces are below ambient pressure. ('splain why?) Bernoulli. But without that reduction of the pressure across the top curve of the wing, the pressure below it can't do much at all, can it? Which I never disagreed with. But anyone who thinks the upper surface of the wing is experiencing anything but a downward force is just sadly misinformed. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg Unfortunately for you, Alan, I have some actual observations of a fabric-covered wing in flight. My Jodel, being a fabric-covered low- wing aircraft, has a top surface easily observed during flight. The fabric actually pulls up between the ribs in flight. It actually does. And near the trailing edge, it's pushed down just a little between the ribs. Which agrees perfectly with the distribution of lift on airfoil diagrams. And don't give me any baloney about pressure inside the wing bulging the fabric.If that was the case, it would all bulge, not just the 90% aft of the leading edge. http://www.cartage.org.lb/en/themes/...y/Velocity.htm I have a picture here of a biplane that had a poor fabric job. The fabric hadn't been tensioned properly during application, and the view from above of the wing in flight showed the fabric bulging upward between the ribs quite amazingly. Positive pressure on the top surface sure isn't going to do that. There really isn't much substitute for actual observation. Flights of imagination are usually way out to lunch. We have a few guys of in homebuiltairplanes.com who are similarly convinced that all the experts are wrong and have been for 150 years. Dan |
#53
|
|||
|
|||
Alan Baker Edict: No more Suction References (was visualization of the lift distribution...)
In article ,
brian whatcott wrote: Alan Baker wrote: No one understands "suction" to actually mean a pulling force. Remember folks: no more talk of sucking soda through a straw! Just suck it up! ... don't pretend that there is a force acting upward on the surface of the liquid inside the straw... ...because you'll be wrong. You still don't get it Alan. This level of attention to minutiae is impressive in Junior High science classes, and paradoxically is quite correct but trivial. Get over it. Just so you can savor the general idea - let me phrase the general concept so it won't trip your OC reaction: In the general case, two thirds of the lift provided by a wing is due to the depression over the upper surface - (actually towards the front...) and a third due to the air flow over the lower surface. THERE. Are you happy now? Brian W I was happy to begin with. Read my initial reply: "Ummmm... It sort of depends what you mean. If you mean that suction is actually providing an upward force, you're quite mistaken. If you mean that the difference in pressure between upper and lower surfaces is 2/3 the result of lower pressure on the upper surface, then you might be right. I don't know." You see, I never had any problem sorting out the "minutiae" from the important. But a whole bunch of people (well, *some* people) jumped in and certainly made statements that they actually believe the air was pulling up on the wing. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#55
|
|||
|
|||
BTW, visualisation of the lift distribution over a wing
In article ,
Alan Baker wrote: But without that reduction of the pressure across the top curve of the wing, the pressure below it can't do much at all, can it? Which I never disagreed with. But anyone who thinks the upper surface of the wing is experiencing anything but a downward force is just sadly misinformed. Unfortunately for you, Alan, I have some actual observations of a fabric-covered wing in flight. My Jodel, being a fabric-covered low- wing aircraft, has a top surface easily observed during flight. The fabric actually pulls up between the ribs in flight. It actually does. And near the trailing edge, it's pushed down just a little between the ribs. Which agrees perfectly with the distribution of lift on airfoil diagrams. And it is only deflected upward by the fact that the air *pushing* on the bottom of the fabric's surface is doing so with greater force than the air *pushing* down from above. And don't give me any baloney about pressure inside the wing bulging the fabric.If that was the case, it would all bulge, not just the 90% aft of the leading edge. I would only bulge where the air is at lower pressure than the air inside the wing. http://www.cartage.org.lb/en/themes/...mics/FlyingDyn am ics/Aerodynamics/SelectedTopics/Velocity/Velocity/Velocity.htm I have a picture here of a biplane that had a poor fabric job. The fabric hadn't been tensioned properly during application, and the view from above of the wing in flight showed the fabric bulging upward between the ribs quite amazingly. Positive pressure on the top surface sure isn't going to do that. Not on it's own, no. But greater positive pressure on the bottom surface than on the top surface sure is and does. There really isn't much substitute for actual observation. Flights of imagination are usually way out to lunch. We have a few guys of in homebuiltairplanes.com who are similarly convinced that all the experts are wrong and have been for 150 years. Observation can lead you astray: and that is clearly the case here if you actually think that air can *pull* on a surface. BTW, Brian: This is precisely why I bother with "minutiae". The PP clearly believes that the air is actually pulling... -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#56
|
|||
|
|||
BTW, visualisation of the lift distribution over a wing
Alan Baker wrote:
This is precisely why I bother with "minutiae". The PP clearly believes that the air is actually pulling... I'm with Einstein. It's relative. If I'm floating above a wing in flight and the wing is "climbing" it looks like it's being sucked toward me. If I'm floating below a wing in flight and the wing is "climbing" it looks like it's being pushed away from me. In all reality, as an airplane USER, I don't really care what is really happening. I know how to manipulate the controls I have to make it do what I want it to do. |
#57
|
|||
|
|||
visualisation of the lift distribution over a wing
Alan Baker wrote:
Observation can lead you astray: and that is clearly the case here if you actually think that air can *pull* on a surface. Why can't air PULL on a surface? Air is made up of molecules. Molecules have mass. Anything with mass can attract anything else with mass, can't it? |
#58
|
|||
|
|||
visualisation of the lift distribution over a wing
In article ,
Scott wrote: Alan Baker wrote: Observation can lead you astray: and that is clearly the case here if you actually think that air can *pull* on a surface. Why can't air PULL on a surface? Air is made up of molecules. Molecules have mass. Anything with mass can attract anything else with mass, can't it? Gravity? You're not serious. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#59
|
|||
|
|||
visualisation of the lift distribution over a wing
On Sat, 28 Nov 2009 19:07:16 -0600, brian whatcott
wrote: Stealth Pilot wrote: /snip/ it is the air below pushing you up that lifts the wing. Stealth Pilot In most circumstances, suction on the upper surface contributes about 2/3 rds of the lift, and pressure on the lower surface contributes about 1/3 rd. That's one reason which rib stitching for rag wings is a biggy. Brian W I have never noticed the fabric lifting on my wings, however I have seen the fuel siphon out of a wing tank due to an improperly applied fuel cap. |
#60
|
|||
|
|||
visualisation of the lift distribution over a wing
In article ,
Ed wrote: On Sat, 28 Nov 2009 19:07:16 -0600, brian whatcott wrote: Stealth Pilot wrote: /snip/ it is the air below pushing you up that lifts the wing. Stealth Pilot In most circumstances, suction on the upper surface contributes about 2/3 rds of the lift, and pressure on the lower surface contributes about 1/3 rd. That's one reason which rib stitching for rag wings is a biggy. Brian W I have never noticed the fabric lifting on my wings, however I have seen the fuel siphon out of a wing tank due to an improperly applied fuel cap. And greater pressure in the tank than outside of it... -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Pressure Distribution Charts | sisu1a | Soaring | 0 | September 21st 08 05:53 PM |
Soundwaves Boost Wing Lift | [email protected] | Home Built | 30 | September 5th 05 10:21 PM |
747 weight distribution | Robin | General Aviation | 25 | June 22nd 05 03:53 AM |
Distribution of armor on a B-52 | B2431 | Military Aviation | 12 | August 16th 04 09:07 PM |
Alternator load distribution in a Baron | Viperdoc | Owning | 7 | December 9th 03 10:27 PM |