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Search: Posts Made By: KenLitko
Showing results 1 to 25 of 243
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Forum: Aerodynamics
03-30-2005, 12:28 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

A flat plate wing will only provide lift at positive alpha... true.

Blowing air over a flat plate (piece of paper, balsa, tissue, whatever), on only the top side, works fine for creating a force...
Forum: Aerodynamics
03-29-2005, 05:17 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Adam_one,

It works just fine if it is flat. I have done this plenty of times myself. The lift is more for a curved piece of paper and the paper rises more.... this doesn't mean that the flat...
Forum: Aerodynamics
03-23-2005, 03:53 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

you are right on with all the forces summing to zero... Newton's laws state that an object in motion (steady level flight) will remain in motion (same speed, direction) unless acted upon by a force...
Forum: Aerodynamics
03-23-2005, 03:29 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

More than likely what is happening is you are balancing a teeter totter.... the weight of the aircraft is sitting at a position near the AC that also balances the moment of the wing.

If you...
Forum: Aerodynamics
03-23-2005, 02:25 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Reflex is built into a flying wing for longitudinal stability... it takes the place of the tail by balancing out the pitching moment of the wing (mostly... still needs to be trimmed for different...
Forum: Aerodynamics
03-23-2005, 02:18 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Drag acts through the AC... thrust acts at the point of application... which is not at the AC.

Likewise, weight acts at the CG, which is likely not at the AC of the wing.
Forum: Aerodynamics
03-23-2005, 02:02 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

adam_one,

Thrust and drag forces exist, but they do not act through the AC of the wing. If they do not act through the same point, you CANNOT sum the vectors.

Ken - www.litkoaero.com
Forum: Aerodynamics
03-22-2005, 06:52 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

LouW,

I can assure you I have read all the posts.

I just can't get satisfactory answers to my questions... I am still trying to find out what replaces all this downwashed air. Are we...
Forum: Aerodynamics
03-22-2005, 04:04 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

First two questions answered, but not the third.

Ok... so we pull some air down, and some air above it replaces that air. Basically... the downwash that is "sent down" and lifts our wing must be...
Forum: Aerodynamics
03-22-2005, 03:19 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

adam_one,

There is still a very fundamental thing... very central to your argument... that you have not answered, even though I have asked you numerous times now...

What is replacing all...
Forum: Aerodynamics
03-22-2005, 10:45 AM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

There is a perfect balance of forces between the pressure on the skin of the wing and the air all around it.

My coffee cup sits on my desk, my desk pushes up on my coffee cup... perfect balance...
Forum: Aerodynamics
03-21-2005, 04:14 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

adam_one, I'm not answering any of your questions till you answer mine.

I think that's only fair :-)

Ken - www.litkoaero.com
Forum: Aerodynamics
03-21-2005, 03:14 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

OK... my last response... I do have real work to do :-)

Wings and Helicopters do not work the same way... the flow through a helicopter disc is non-steady and compressible and is better related...
Forum: Aerodynamics
03-21-2005, 02:12 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

How does that contradict what I am saying? It appears to have a very strong upturn at the end of the sheet, outboard of the wing... judging by the size of the flow indicator.

Are you telling me...
Forum: Aerodynamics
03-21-2005, 01:50 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Yeah yeah yeah... :-)

BTW... I corrected the "F=ma"... which still applies, but replaced it with the "downward momentum thingy" :-)

Back to our regularly scheduled program...

OK......
Forum: Aerodynamics
03-21-2005, 01:45 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

So, the "trailing edge downwash" and the "wing tip vortex downwash" lead to two different types of downward momentum..... One that carries momentum and creates lift... and one that just whistles on...
Forum: Aerodynamics
03-21-2005, 01:37 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Looking at a wing from the tip, inboard... with the windward edge at the left, the flow is turned in the _clockwise_ direction.

The NASA web pages degenerate into a "net downward momentum lifts...
Forum: Aerodynamics
03-21-2005, 12:49 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

adam_one,

The above site says that the flow is turned, not "sent down". Turning something and shoving it in one direction are two different things.

"Turned flow" = circulation

The air...
Forum: Aerodynamics
03-21-2005, 12:27 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

That's correct.... from the freestream, turned up (upwash), turned over the airfoil, turned down (downwash) and turned back to the freestream (well mostly anyway... there is probably a lot of...
Forum: Aerodynamics
03-21-2005, 12:00 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Not quite... wingtip votices do not cause induced drag.. they ARE induced drag. Wingtip votices are the price we pay for having a REAL wing. We would have more lift if we didn't have them.

We...
Forum: Aerodynamics
03-21-2005, 11:41 AM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

Why? Why is that necessary. Prove it. This statement is nothing other than a hypothesis with no proof behind it.

Here is my proof...

The wing is sending air down, but it is also sending air...
Forum: Aerodynamics
03-19-2005, 12:42 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

OK... vortices exist... So we have upwash next to and behind the wing? Can you quantify how that affects lift? After all... if we are moving mass upwards it follows that it carries momentum...
Forum: Aerodynamics
03-18-2005, 03:03 PM
Replies: 195
Views: 28,808
Posted By KenLitko

RE: Reflexed Airfoil and Flying Wings - Downwash?

!!!!! - Troll Warning - !!!!! -> But I thought that this was some actual food for thought.

For the uninitiated.. I support the argument that momentum is involved in lift... but net momentum is...
Forum: Aerodynamics
02-21-2005, 04:40 PM
Replies: 206
Views: 23,079
Posted By KenLitko

RE: Jef Raskin article on aerodynamics in Fly RC Magazine

Tim,

The airfoil is simply a better wing, but a flat plate operates under the same principles. The only difference is the amount of lift created.

You said:

"Nor would a wing, laying on...
Forum: Aerodynamics
02-21-2005, 01:47 PM
Replies: 206
Views: 23,079
Posted By KenLitko

RE: Jef Raskin article on aerodynamics in Fly RC Magazine

Tim,

That's not exactly a precise experiment.

If the pressure is lower on the top of the flat plate, there will be a force that shoves it upwards.... whether or not that force is large...
Showing results 1 to 25 of 243
 
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