ATEC Zephyr for sale

[facthunter]

Unless you're ambitious. Nev

[aro]

17 minutes ago, turboplanner said:

There's no sucking.

What's your definition of sucking? I would say it's a force generated by reduced air pressure...

[aro]

Duplicate

Edited Wednesday at 11:26 PM by aro

[facthunter]

You rely on a difference of pressure A column of water will only rise 32 feet no matter how hard you SUCK, the ambient pressure limits how high the water  is elevated above the surface of where you got it from.   Nev

[turboplanner]

44 minutes ago, aro said:

What's your definition of sucking? I would say it's a force generated by reduced air pressure...

Here are two explanations of Bernoulli's principle.

 

https://www.youtube.com/watch?v=XP6oqIic4lo

The bag doesn't have any way of sucking the air in.

 

https://www.youtube.com/watch?v=724noDp_cz8

[aro]

1 hour ago, turboplanner said:

Here are two explanations of Bernoulli's principle.

 

You didn't give your definition of suction. Everything is just higher or lower pressure, but it's often a useful mental model to describe something as suction. If you want to say it's not suction, provide the definition you're using.

 

Here is an example of suction from the Bernoulli effect:

 

Pretty much every explanation of wing lift using the Bernoulli effect gets it wrong, so it's not very useful in that case. It just muddies the water usually. 

[turboplanner]

12 minutes ago, aro said:

 

You didn't give your definition of suction. 

 

 

I didn't give my definition for phases of the moon either because neither are involved.

 

The saddest thing about this thread is that the poor person trying to sell an aircraft which may well have 30 years of structural integrity if he/she follows qualified knowledge, may have a lot more trouble getting a buyer, and from the spinoff crap, sooner or later someone who followed ignorant advice is possibly going to have an engine failure and perhaps a fatal landing.

[aro]

13 minutes ago, turboplanner said:

I didn't give my definition for phases of the moon either because neither are involved.

 

What's not involved?

[aro]

Here's a definition of suction:

 

"the act or process of exerting a force upon a solid, liquid, or gaseous body by reason of reduced air pressure over part of its surface"

 

I think it's fair to say we are exerting a force on a solid body (the wing) by reason of reduced air pressure over it's surface.

 

https://www.merriam-webster.com/dictionary/suction

[facthunter]

You reduce the force that is already there thereby creating  a difference of pressures. Suction is a pretty nebulous concept in science.   You can't apply suction in a Vaccuum because there's NO pressure already.  So no difference to produce a force.. Wings don't work at all in Space.  Nev

[aro]

1 minute ago, facthunter said:

Suction is a pretty nebulous concept in science.

 

Yes. As I said:

 

1 hour ago, aro said:

Everything is just higher or lower pressure, but it's often a useful mental model to describe something as suction.

 

[facthunter]

I was backing you up. but I've also added other info relative to it.. Science teachers often get this wrong THEY are not REAL Science Teachers and should pay for the Damage done to young Minds. Nev

[Geoff_H]

Most of the theory is a starting point.  Practical experience overrides it all. Bernoulli's theorem is a two dimension equation about every balance, great for simple aeronautical thing.  Fantastic for pitot calls, usable but not perfect for a 3 dimensional wing.  Air flowing in a duct at low velocities is different to high velocities. If you really want to calculate wing lifts moment and drag accurately you need to it like finite element does stress.  Every air molecule affects the nearest molecules in a different way and its the collective use forces of all these molecules that let us fly.  This site is not a mathematical site, nor an ego site.  The 3d lift of air around a body should use the 'del' operator mathematics for calculation,  but who cares.  After weeks of mathematics something will be assumed incorrectly and the whole calculation is crap. As an engineer for over 40 years it's just about very intelligent assumptions (i have had many wrong ones too).   It doesn't matter, we just use our collective experiences and we get there in the end.  I believe that this site for us to use our collective experiences,  sure there will be lots of errors, and lots of good advice.  If we work together we will have a lot of enjoyment.   We all contribute something from a different set of previous experiences. Turbo i enjoy your enthusiasm on this site bringing me learning from our collective minds.   Good on you.