RE: Reflexed Airfoil and Flying Wings - Downwash?  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       


Composite-ARF Extra 260 3m - RTF
Seller:  snobird
Details:   $4,900.00   |  8/21/2008   |  Classified Ad
We will rotate YOUR AD in this spot if you select "Forum Featured" when placing or editing your ad!

All Forums >> RC Airplanes >> Aerodynamics >> RE: Reflexed Airfoil and Flying Wings - Downwash?
Page: <<   < prev  1 2 3 4 5 6 7 [8]

Login
Message << Older Topic   Newer Topic >>
RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 2:02:01 PM   
dick Hanson



Posts: 9920
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		adam- that is true of any lifting surface.
You may not agree with my simple theory of lift -but it makes sense to me . (post 168)

_____________________________

I am watching you
Libby

(in reply to BMatthews)
       Post #: 176

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 5:28:11 PM   
KenLitko


 

Posts: 243
Joined: 1/3/2003
From: Crown Point, IN,
Status: offline
quote:

ORIGINAL: adam_one

KenLitko and dick Hanson,
Notice that the flat plate creates lift only when it has a positive AOA, and when there is air flowing through both the top and bottom. It doesn't work if you only blow over the top while the air at the bottom is standing still.
You may test it using a hair dryer blowing only over the top side.


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 to push the flat plate -into- the stream of lower pressure air. The moving air on top has a lower overall pressure than the ambient air on the bottom.

The force is small, you may need to blow harder. You may also be having trouble attaching the flow to the surface... once you satisfy those requirements it works just fine.

Ken - www.litkoaero.com

_____________________________

Ken - http://www.litkoaero.com/
R/C Aircraft Laser Cutting and Design

(in reply to adam_one)
       Post #: 177

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 5:48:47 PM   
adam_one


 

Posts: 398
Joined: 2/26/2003
From: Stockholm, SWEDEN
Status: offline
quote:

ORIGINAL: dick Hanson

adam- that is true of any lifting surface.
You may not agree with my simple theory of lift -but it makes sense to me . (post 168)

Dick,
Both the air and the water are fluids and behave therefore in the same way despite differences in their density and viscosity. Aerodynamics and hydrodynamics are very much alike.
If I understood your description well, it sounds close to the truth, but you're just looking at only one side of the coin (pressure differential) as most people do, maybe because it is easier to measure and to understand.


< Message edited by adam_one -- 3/30/2005 6:11:58 PM >

_____________________________

http://adamone.rchomepage.com

(in reply to dick Hanson)
       Post #: 178

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 5:58:54 PM   
adam_one


 

Posts: 398
Joined: 2/26/2003
From: Stockholm, SWEDEN
Status: offline
quote:

ORIGINAL: KenLitko

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 to push the flat plate -into- the stream of lower pressure air. The moving air on top has a lower overall pressure than the ambient air on the bottom.

The force is small, you may need to blow harder. You may also be having trouble attaching the flow to the surface... once you satisfy those requirements it works just fine.

Ken - www.litkoaero.com


Take a piece of a flat light foam plate and blow air only over the top side (with help of a hair dryer) - it will never lift as long as you don't blow at the bottom side, I promise


_____________________________

http://adamone.rchomepage.com

(in reply to KenLitko)
       Post #: 179

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 7:46:43 PM   
dick Hanson



Posts: 9920
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		I try to always reduce any "variable" to absolutely minimum usable information.
In this case - "lift" is simply, at least to me a matter of taming a common phenomena to do work.
The airfoils everybody fusses over, are shapes which are compromises using available material for a particular task.
This situation has been getting better since men first started makong aircraft -or models of aircraft or any flying device.
Imagine you had NO constraints on the strength of material to build wings to do a task.
what would the wings look like then ?
If YOUR theory is adapable - draw an ideal wing to replace the wings on -say - a Piper Cub.
This is the fun part of modeling to me .
given the new motors and super light building material I found that most of what I was told years back - can be modified - a lot.

_____________________________

I am watching you
Libby

(in reply to adam_one)
       Post #: 180

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 8:05:45 PM   
adam_one


 

Posts: 398
Joined: 2/26/2003
From: Stockholm, SWEDEN
Status: offline
quote:

If YOUR theory is adapable - draw an ideal wing to replace the wings on -say - a Piper Cub.

Dick,
It is not about my own theory, it's about physics laws.

As for the "ideal" wing, you have to tell the actual size of the plane, the weight, at what max speed it is intended to fly, stall speed, whether it should be a STOL… etc.
In fact, there's no single simple answer, it's most a compromise.



< Message edited by adam_one -- 3/30/2005 9:35:23 PM >

_____________________________

http://adamone.rchomepage.com

(in reply to dick Hanson)
       Post #: 181

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/30/2005 10:08:44 PM   
dick Hanson



Posts: 9920
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		that iswhy I suggested a "typical level flight aircraft "-a Cub

_____________________________

I am watching you
Libby

(in reply to adam_one)
       Post #: 182

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/31/2005 3:00:33 PM   
adam_one


 

Posts: 398
Joined: 2/26/2003
From: Stockholm, SWEDEN
Status: offline 		If you are referring to the full-size Cub, then I would say that I think the actual wing is a good compromise considering the plane's purpose and the power to weight ratio. But of course, it might not be the ideal wing for everybody.
Have you any suggestion for a better wing to the full-size Cub?


_____________________________

http://adamone.rchomepage.com

(in reply to dick Hanson)
       Post #: 183

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/31/2005 7:48:43 PM   
dick Hanson



Posts: 9920
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		sure clip 6' from it and stuf in a bigger engine.

_____________________________

I am watching you
Libby

(in reply to adam_one)
       Post #: 184

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/31/2005 8:03:53 PM   
adam_one


 

Posts: 398
Joined: 2/26/2003
From: Stockholm, SWEDEN
Status: offline
quote:

ORIGINAL: dick Hanson

sure clip 6' from it and stuf in a bigger engine.

Then I guess you'd get a faster Cub but also higher stall speed.

_____________________________

http://adamone.rchomepage.com

(in reply to dick Hanson)
       Post #: 185

RE: Reflexed Airfoil and Flying Wings - Downwash? - 3/31/2005 8:31:28 PM   
BMatthews



Posts: 8865
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		An more aerobatic. But it's been done...

Sig's scale model of Hazel's clipped wing cub.

In truth I don't think you can really come up with a better wing for the Cub. As a trainer and casual flyabout from the pre-ultralight days that continues to offer a low cost user friendly way to get closer to clouds it's pretty much a winner. Sure it's not fast or hotly aerobatic but that wasn't its mission.


_____________________________

Bruce-
Proudly wasting balsa since 1965.

Free Flighters go that extra mile........

(in reply to adam_one)
       Post #: 186

RE: Reflexed Airfoil and Flying Wings - Downwash? - 4/1/2005 6:46:22 AM   
Oryx


 

Posts: 198
Joined: 6/17/2002
From: Pretoria, SOUTH AFRICA
Status: offline
quote:

ORIGINAL: dick Hanson

sure clip 6' from it and stuf in a bigger engine.


- Probably slightly faster, bit more maneuvrable (especially roll-rate due to less roll inertia) and better climb rate due to more power (although now also a bit heavier).

- Also higher stall speed, shorter duration and range (important for those that still like to do cross-country with a Cub), less forgiving, more fatique and higher stresses due to additional torque, more expensive to maintain and operate, will lose more speed in turns due to higher induced drag (higher wing loading), more care will have to be taken when opening or closing the throttle quickly (more torque) especially in ground operations and when aborting landings, heavier pitch control forces due to more forward CG, etc...

In general, it will lose many of the characteristics that Cub flyers love so much.

(in reply to dick Hanson)
       Post #: 187

Page:   <<   < prev  1 2 3 4 5 6 7 [8]
All Forums >> RC Airplanes >> Aerodynamics >> RE: Reflexed Airfoil and Flying Wings - Downwash?
Page: <<   < prev  1 2 3 4 5 6 7 [8]





Jump to: