We need a technical and logical discussion.

Any topic with a chance of polarization - Not for the easily offended.

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exhaustgases
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Re: We need a technical and logical discussion.

Post by exhaustgases » Thu Aug 17, 2017 3:34 am

joe 90 wrote:My first plane was a paper one.

It flew OK for a short distance.


It's the differential in pressure between the top and bottom of the wing.
You can't have one without the other.
But the largest part of it will be the vacuum at the top of the wing.
Not true, it's a huge positive pressure at the bottom. What huge vacuum does a carburetor venturi have?
When you skip a rock on water is it the huge vacuum at the top? Or the pressure of the water being impacted that causes it?

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Re: We need a technical and logical discussion.

Post by joe 90 » Thu Aug 17, 2017 4:33 am

Water is different because it's a non compressible fluid.

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Re: We need a technical and logical discussion.

Post by David Redszus » Thu Aug 17, 2017 10:57 am

The air flow speed on the underside of a wing is the same as the wing speed. On the top, the air must travel further in the same amount of time. It moves a lot faster and produces a substantial negative pressure called lift.

Increasing the attack angle, for a given air foil, will eventually cause a stall condition even though under wing pressure is high. At this point we no longer have lift and the pressure becomes drag.

Is it the negative or positive pressure in a carb venturi that draws fuel?

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Re: We need a technical and logical discussion.

Post by Firedome8 » Thu Aug 17, 2017 12:59 pm

David Redszus wrote:The air flow speed on the underside of a wing is the same as the wing speed. On the top, the air must travel further in the same amount of time. It moves a lot faster and produces a substantial negative pressure called lift.

Increasing the attack angle, for a given air foil, will eventually cause a stall condition even though under wing pressure is high. At this point we no longer have lift and the pressure becomes drag.

Is it the negative or positive pressure in a carb venturi that draws fuel?
Does Increasing the attack angle make the air on top break away from the surface and lower the delta p on the top of wing??

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Re: We need a technical and logical discussion.

Post by exhaustgases » Thu Aug 17, 2017 8:00 pm

Okay now its time for the data. What are the psi numbers at the top of the wing. Since the wing is deflecting air down its a positive pressure.
Here is the simplest thing you can do, I did it as a kid. Someone is driving a car at 60mph, you put your hand out side into the airflow and shape it like a wing, you will feel what side the pressure is that causes lift, make sure to give it an angle of attack.
So what is the huge minus pressure in a carburetor venturi? Numbers please, numbers for the top of the wing as well. Venturi is inches of water very low pressure, enough to suck some gas out of the float bowl.

And to answer the venturi question, its the positive pressure in the float bowl that pushes the column of fuel towards the minus pressure, or the lower pressure caused via the venturi. Same thing that fills a cylinder as the piston descends in the bore, that creates a negative or lower than atmospheric pressure and the higher positive pressure pushes the air into the cylinder. Kinda like when a submarine goes to its crush depth its a huge positive pressure pushing in on it.

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Re: We need a technical and logical discussion.

Post by David Redszus » Thu Aug 17, 2017 11:37 pm

Okay now its time for the data.
Damn good idea, enough talk. Time for numbers.
I have selected an airfoil N22, which is cambered with a flat bottom.
What are the psi numbers at the top of the wing.
Aeronautical computations do not use psi because pressure is a function of altitude and velocity.
Instead they use pressure coefficient which is merely a percentage of total pressure.
Since the wing is deflecting air down its a positive pressure.
The N22 airfoil shape has a flat bottom and curved upper surface. It can be flown with a zero
angle of attack since the upper surface causes air to flow faster than the lower surface.

I have calculated pressure coefficients for this wing using three different angles of attack: 0, 5, and 9 degs.
The first column indicates the location along the chord length as a fraction of total chord length.
The second column is the pressure along the lower wing surface.
The third column is the pressure along the upper wing surface.
The fourth column is the ratio of upper to lower pressure.
A negative pressure along the lower surface simply indicates the direction of force; both values produce lift.

Zero attack angle. lift coefficient 0.559.

0.1...-.002.....0.206....103
0.2...-.004.....0.226....56
0.3...-.010.....0.216....22
0.6...-.012.....0.150....13
0.9...-.016.....0.037....2.3

5 deg attack angle. lift coefficient 1.088

0.1...-.017.....0.323....19
0.2...-.014.....0.313....22
0.3...-.016.....0.282....17
0.6...-.031.....0.165....5
0.9...-.056.....0.014....0.25

9 deg attack angle. lift coefficient 0.106.

0.1...-.012.....0.436....36
0.2...-.014.....0.397....28
0.3...-.018.....0.352....19
0.6...-.051.....0.175....3
0.9...-.090.....0.012....0.13
STALL..STALL..STALL...STALL

As can be seen, the upper wing surface produces a much greater lift force than does the lower edge, even as angle of attack is increased to the point of stall. For this airfoil, the leading third of the wing produces the most lift. As we move rearward along the wing, the speeds begin to equalize and the lift above and below the wing become almost identical.

If applied to the venturi of a carburetor, the narrowest part of the throat would produce the strongest fuel signal.
Old man Bernoulli was right. Again. A venturi is simply two airfoils with their curved surfaces facing each other.

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Re: We need a technical and logical discussion.

Post by exhaustgases » Fri Aug 18, 2017 6:50 pm

Okay, I've been around super expensive metal 727 wings in my younger days, they had many many super small copper tubes feeding to the top of the wing and to the bottom of the wing they were there to measure the pressure. I don't want to see a coefficient, I don't want to see a differential
I want to see a psi or inches of something for each, and angle of attack is set in 2 ways on an aircraft number 1 is the incidence angle, number 2 is what the pilot establishes during flight and power settings.
Use a propeller blade, gosh even the old ww2 video about propellers was smart enough to say the air being pushed back is what makes it work.
And this is why this is in the political section, to prove simple logic is just not existent.

So average carburetor (find some old 1 bbl 6 banger) what is the venturi pressure in inches of H2o ? And what is the inches of H2o on the outside or back side of that venturi? What side would do the lifting? The venturi or the other side? And you know what I'm saying, I know a ring won't lift.

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Re: We need a technical and logical discussion.

Post by exhaustgases » Sat Aug 19, 2017 4:24 am

https://www.youtube.com/watch?v=eoNySabChvA

Here is an efficient wing if you can call it that. Its more of an air scoop, another fine example of how positive pressure is king, the only sucking at the top of this wing is from the air being pulled through the ducting. Its like an excavator digging dirt, first there is the positive pressure to remove the dirt or mud that action like a piston moving down in the cylinder creates the suction. There is not much of an airfoil shape to the upper or front of this turbine fan blade.

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Re: We need a technical and logical discussion.

Post by David Redszus » Sat Aug 19, 2017 2:05 pm

Use a propeller blade, gosh even the old ww2 video about propellers was smart enough to say the air being pushed back is what makes it work.
Sorry, that is hopelessly wrong. Grammar school science. For every action there is an equal and opposite reaction. Think about it. The forward motion produced by the propeller moves the aircraft forward. The airspeed over the wing produces lift. End of story.

Consider. Park an aircraft at the end of a takeoff runway. Give the engine power. The prop backwash flows over the wing. Why doesn't the plane immediately rise in the air? It has lots of pressure under the wing but no airspeed above the wing. As the aircraft moves forward and gains speed, at some point it will produce enough lift to take off.
And this is why this is in the political section, to prove simple logic is just not existent.
Simple logic not grounded on fact is just simple minded opinion, and....completely worthless.
I have posted actual data regarding wing pressure. Where is yours?

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Re: We need a technical and logical discussion.

Post by exhaustgases » Sat Aug 19, 2017 5:26 pm

When an aircraft engine is on a ground stand, the propeller or turbofan blades are cutting into the air just like the air plane wing does. So then use the jet engine blade as the airfoil example the suction at the front is caused by the air being evacuated and forced to the rear, how much simpler can you get? How can you say that a propeller acting like a wing or even the jet fan acting like a wing would propel the engine forward by the sucking action??????????? A rocket engine using your simple science terms of action reaction... has no vacuum in front of it and causes the ship movement by way of movement of a positive pressure gas stream out the rear.
Lift is caused by positive pressure under the wing and some assistance from the airflow over the top as well as helping with stability. Stick your hand out the car window and feel it.

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Re: We need a technical and logical discussion.

Post by joe 90 » Sat Aug 19, 2017 9:16 pm

David Redszus wrote:[

Consider. Park an aircraft at the end of a takeoff runway. Give the engine power. The prop backwash flows over the wing. Why doesn't the plane immediately rise in the air?
?


That's the same as having a sailing ship.
Then mounting an engine driven fan to fill up the sails then wondering why it won't go anywhere.

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Re: We need a technical and logical discussion.

Post by exhaustgases » Sun Aug 20, 2017 1:45 am

joe 90 wrote:
David Redszus wrote:[

Consider. Park an aircraft at the end of a takeoff runway. Give the engine power. The prop backwash flows over the wing. Why doesn't the plane immediately rise in the air?
?


That's the same as having a sailing ship.
Then mounting an engine driven fan to fill up the sails then wondering why it won't go anywhere.
Funny stuff! Your analogy, that is if the engine is also mounted on the ship is like putting a jacking device from a structure on the ship to that sail.
If that engine is mounted on something outside or off the ship then it will move it just fine. That's how the wind does it, its like as huge fan blowing on the sail, but the fan is not mounted on the ship.

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Re: We need a technical and logical discussion.

Post by exhaustgases » Sun Aug 20, 2017 4:51 pm

In the boat example the sail represents a thrust blocking device. In the plane on the ground with the air flow into the wings, if the air flow was the proper speed and proper volume to cover the whole wing then yes it would fly. The difference of that and the sail is airflow. The plane would be similar to a vertal or helicopter only with a stationary wing. It would take so much more propeller area to accomplish that as well as the required HP to turn it, it could not be done very easy.

Oh and to add to the airflow deal with the boat, put something that air flow can act upon to propel the boat if you don't want to use the air thrust from the prop on the engine. Add another propeller that the engine one blows on and connect it to a shaft then to an under water propeller. There you go airflow working and not being stopped by a sail.

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Re: We need a technical and logical discussion.

Post by turbo2256b » Sun Aug 20, 2017 5:07 pm

air going through the carb is louder than exhaust because it can reach the speed of sound.

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Re: We need a technical and logical discussion.

Post by David Redszus » Mon Aug 21, 2017 11:24 am

Please explain how a sailboat can sail into the wind.

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