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stepinwolf

Joined: 21 Jan 2008
Posts: 133
Location: Canada

Posted: Fri Jan 25, 2008 4:27 pm Post subject: Cabin airfoil

Has anyone built up the section over the cabin as an airfoil, in the same shape as the wing.  I'm not planning to do much flying while looking though the skylight, so I am thinking that by building it in this way, I would have an additional 16 to 17 sq. feet of wing area, not to mention another 4.5' section of slats.



Thanks to those of you, who will take the time to respond to my request for information.



Bob, the 701 scratch

_________________
Long wing + vga's, = lo & slo

rjscep(at)yahoo.com
Guest

Posted: Fri Jan 25, 2008 5:06 pm Post subject: Cabin airfoil

 	  Quote: 	
		   I think the "Savanah" has a straight wing instead

 of the break in the middle...do not archive....

--- stepinwolf <robert.pelland(at)cgocable.ca> wrote:
	




 	  Quote: 	
		   

 <robert.pelland(at)cgocable.ca>

 

 Has anyone built up the section over the cabin as an

 airfoil, in the same shape as the wing.  I'm not

 planning to do much flying while looking though the

 skylight, so I am thinking that by building it in

 this way, I would have an additional 16 to 17 sq.

 feet of wing area, not to mention another 4.5'

 section of slats.

 

 Thanks to those of you, who will take the time to

 respond to my request for information.

 

 Bob, the 701 scratch

 

 --------

 Live each day, as if it was your last

 

 

 

 

 Read this topic online here:

 



http://forums.matronics.com/viewtopic.php?p=160512#160512
	


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kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Fri Jan 25, 2008 8:31 pm Post subject: Re: Cabin airfoil

I have heard of others doing this, one I believe to be quite knowledgeable . But I just can not see how you can get any lift from this. There is no bottom of the airfoil.

_________________
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stepinwolf

Joined: 21 Jan 2008
Posts: 133
Location: Canada

Posted: Sat Jan 26, 2008 3:10 am Post subject: Re: Cabin airfoil

Kevin, thanks for your input.



I am in no way an engineer,  but I always thought that lift was created by the low pressure area on top of the wing.  If we look at most of the light aircraft on the market today, they all seem to have an airfoil over the top of cabin area, so I'm guessing it has to be a factor in the overall performance of the wing.



Bob

_________________
Long wing + vga's, = lo & slo

dredmoody(at)cox.net
Guest

Posted: Sat Jan 26, 2008 4:26 am Post subject: Cabin airfoil

You are partially correct. The rest of the story is  the realtively higher airpressure under the corresponding undersurface of the  plane (the fuselage in this discussion). The differential produces your lift.  Both the shape of the airfoil and the AOA are factors in producing  lift.

  

 Dred

 [quote]   ---

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Sat Jan 26, 2008 4:49 am Post subject: Re: Cabin airfoil

This is my thought too. The shorter path underneath is just as important as the top shape.  You may get lift right as the sides of the cabin were the standard wing tapers down. And it would seem to reduce drag. But you would lose the prop wash on the rear at low speeds. Though the Savannah seems to do just fine with this section over the roof.



My guess is that it just looks nice this way. Early high wing airplanes were all open so there was lift in this area. When they put the cabin on, they simply set the wing on top of it. ( total conjecture on my part by the way :_)  )

Some designs also have a tube running the full span acting as the main spar. This kind of forces the shape over the cabin.

There may still be lift there, but I like I said I have no idea how it would work.

d.goddard(at)ns.sympatico
Guest

Posted: Sat Jan 26, 2008 5:54 am Post subject: Cabin airfoil

This explains a lot about wings, and airfoils.  It appears to be a complex 

subject. http://www.regenpress.com/

Jaybannist(at)cs.com
Guest

Posted: Sat Jan 26, 2008 6:36 am Post subject: Cabin airfoil

Kevin,



A lot of our list posters seem to have bought into the premise that an airplane flies because of the lift provided by the Bernoulli effect of the upper surface of the wing.  In fact, most of the lift is provided by Newton, pushing on the bottom surface of the wing (With enough power, you can fly a barn door).  This speaks very loudly about the "expertise" of some of our most prolific posters, right? 



Jay in Dallas

"kmccune" <kmccune(at)somtel.net> wrote:



 	  Quote: 	
		  



I have heard of others doing this, one I believe to be quite knowledgeable . But I just can not see how you can get any lift from this. There is no bottom of the airfoil.



--------

Kevin

N701DZ Reserved





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=160531#160531

dougsnash(at)yahoo.com
Guest

Posted: Sat Jan 26, 2008 6:47 am Post subject: Cabin airfoil

Bob and Kevin, I am by no means an expert in

aerodynamics so take this with a grain of salt.



Chris Hientz is the master of form follows function. 

He did the wings on the 701 the way he did for one

reason for sure, in a high angle of bank, your

visability out the top will be much better because of

the thinner wing profile at the root.  Additionally,

there has been some mention on this group of prop

blast to the tail feathers through the opening.  I

can't comment on that one but it at least makes sense.



As a comparison, I checked out a Land Africa (rip off

of a rip off of a 701)that a friend of mine was

helping to build.  It had the airfoil shape over the

cabin.  While the Land Africa has a really nice three

angle instrument panel, the cabin top was kind of ugly

in my eyes.  I know, beauty is not something that

whould be used in the same e-mail as anything about a

701.  In all honesty, the change to the cabin looked

to me like it was done to simplify construction of the

wing roots more than provide additional lift.  Lets

face it, fitting those wing roots on the 701 looks

like a bit of a challenge.  I'll see when I get there

in a couple of months.



As for the amount of lift created by the one sided

airfoil, I can explain that a bit.  First, this

information come from the ground school lectures that

I teach to the youth group I work with.  It comes from

their lesson plans and from the ASA ground school DVD

I use as a basis for my lessons.  I am sure there are

more knowledgable people on this list than me that

will fill in the blanks if I am incorrect on my

impressions.



Lift on an airfoil can be broken down into two main

parts.  The first part is called (I think) Plate Lift

and is the effect of the relative wind hitting the

bottom of the wing.  Same idea as sticking your hand

out the window of a car going down the highway.  If I

understand my aerodynamics correctly, this part of the

lift makes up about 60% if the total lift generated by

a wing.  The other 40% is made up by the air being

accellerated over the top of the wing and creating low

pressure ala Bernoulli.



So, providing my understanding of aerodynamic

principals is accurate, you will not gain much by

adding the 4 ft of span to the airfoil shape. 

Especially if the interference of the rear fuselage

has any effect of the efficiency of the airflow over

the airfoil shape.  The big advantage would be not

having to build the tapered wing root.



Again, if someone has a better understanding of this

than me, feel free to straighten us all out.



Doug MacDonald

CH-701 Scratch Builder

NW Ontario, Canada

  

 	  Quote: 	
		   

 <robert.pelland(at)cgocable.ca>

 

 Kevin, thanks for your input.

 

 I am in no way an engineer,  but I always thought

 that lift was created by the low pressure area on

 top of the wing.  If we look at most of the light

 aircraft on the market today, they all seem to have

 an airfoil over the top of cabin area, so I'm

 guessing it has to be a factor in the overall

 performance of the wing.

 

 Bob


	


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notsew_evets(at)frontiern
Guest

Posted: Sat Jan 26, 2008 7:22 am Post subject: Cabin airfoil

I stand correct............

---

notsew_evets(at)frontiern
Guest

Posted: Sat Jan 26, 2008 7:26 am Post subject: Cabin airfoil

Bernoulli ?

Ever watch a DC 9 take off?

Short wings and carries 137 people PLUS baggage.....

There is a lot of Bernoulli happening........Not!

---

lrm(at)skyhawg.com
Guest

Posted: Sat Jan 26, 2008 7:44 am Post subject: Cabin airfoil

One thing not mentioned is the increased headroom for those who might need 

or want it.  The other is the using of the term "rip off".  I remind every 

one that the 701 is in fact a copy of a multitude of parts used by 

previously like aircraft, by no means is it an original design.  I would 

never say it's a rip off, it's just smart engineering of proven concepts and 

parts, as is the Savanna.



LRM, skyhawg.com.

---

Jeyoung65(at)aol.com
Guest

Posted: Sat Jan 26, 2008 7:45 am Post subject: Cabin airfoil

But to get the barn door to fly it must be at an angle to the air flow.  Thus the air flow over the door will appear to be an airfoil. Jerry of Ga

  

  In a message dated 1/26/2008 9:37:18 A.M. Eastern Standard Time,  Jaybannist(at)cs.com writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: Jaybannist(at)cs.com



Kevin,



A lot of    our list posters seem to have bought into the premise that an airplane flies    because of the lift provided by the Bernoulli effect of the upper surface of    the wing.  In fact, most of the lift is provided by Newton, pushing on    the bottom surface of the wing (With enough power, you can fly a barn    door).  This speaks very loudly about the "expertise" of some of our most    prolific posters, right? 



Jay in Dallas

"kmccune"    <kmccune(at)somtel.net> wrote:



 	  Quote: 	
		  --> Zenith-List message posted    by: "kmccune" <kmccune(at)somtel.net>



I have heard of others    doing this, one I believe to be quite knowledgeable . But I just can not see    how you can get any lift from this. There is no bottom of the    airfoil.



--------

Kevin

N701DZ    Reserved





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=160531#160531

&ghe  es  y       -->                 - MATRONICS WEB FORUMS  nbsp;               - List Contribution Web Site  ;                             =========================
	




	




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  [quote][b]

Jaybannist(at)cs.com
Guest

Posted: Sat Jan 26, 2008 8:10 am Post subject: Cabin airfoil

Also true.  For anyone really interested in the lift theory, there is an excellent (and long) item on the subject at www.eskimo.com/~billb/wing/airfoil.html. The true/false session at the end is the most informative.

Jay in Dallas

Jeyoung65(at)aol.com wrote:

 	  Quote: 	
		  But to get the barn door to fly it must be at an angle to the air flow.  Thus 

the air flow over the door will appear to be an airfoil. Jerry of Ga

In a message dated 1/26/2008 9:37:18 A.M. Eastern Standard Time,  

Jaybannist(at)cs.com writes:

Kevin,

A lot of  our list posters seem to have bought into the premise that an 

airplane flies  because of the lift provided by the Bernoulli effect of the upper 

surface of  the wing.  In fact, most of the lift is provided by Newton, pushing 

on  the bottom surface of the wing (With enough power, you can fly a barn  

door).  This speaks very loudly about the "expertise" of some of our most  

prolific posters, right? 

Jay in Dallas

"kmccune"  <kmccune(at)somtel.net> wrote:

>--> Zenith-List message posted  by: "kmccune" <kmccune(at)somtel.net>

>

>I have heard of others  doing this, one I believe to be quite knowledgeable 

. But I just can not see  how you can get any lift from this. There is no 

bottom of the  airfoil.

>

>--------

>Kevin

>N701DZ  Reserved

>

>

>Read this topic online  here:

>

>http://forums.matronics.com/viewtopic.php?p=160531#160531

>

**************Biggest Grammy Award surprises of all time on AOL Music.     

(http://music.aol.com/grammys/pictures/never-won-a-grammy?NCID=aolcmp003000000025

4

dougsnash(at)yahoo.com
Guest

Posted: Sat Jan 26, 2008 9:04 am Post subject: Cabin airfoil

Okay, for sake of argument, we'll agree to disagree on

the relationship between the CH-701 and the Savannah. 

Third hand knowledge (take it for what it's worth)is

that the Savannah boys in Alberta have commented that

the Land Africa is a rip off of the Savannah.  

Doug MacDonald

CH-701 Scratch builder

NW Ontario, Canada



Do not archive



--- LRM <lrm(at)skyhawg.com> wrote:



 	  Quote: 	
		   

 <lrm(at)skyhawg.com>

 

 One thing not mentioned is the increased headroom

 for those who might need 

 or want it.  The other is the using of the term "rip

 off".  I remind every 

 one that the 701 is in fact a copy of a multitude of

 parts used by 

 previously like aircraft, by no means is it an

 original design.  I would 

 never say it's a rip off, it's just smart

 engineering of proven concepts and 

 parts, as is the Savanna.

 

 LRM, skyhawg.com.

 


	


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jmcburney(at)pobox.com
Guest

Posted: Sat Jan 26, 2008 9:13 am Post subject: Cabin airfoil

Hi, all,



You would lose some (maybe "a little") control authority from the

tailfeathers due to blanking of some of the prop's discharge air.



Just a thought.



Jim

CH-801

DeltaHawk diesel

Augusta GA USA

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Sat Jan 26, 2008 11:11 am Post subject: Re: Cabin airfoil

Its funny , but I am having a hard time figuring out who agrees with whom!  



Do not archive

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Sat Jan 26, 2008 12:34 pm Post subject: Re: Cabin airfoil

I can assure you all that the 701 lexan roof is creating lift just as it is. When on the ground the top of the lexan window is very tight to the cross brace. I have to push very hard to create any gap. When in flight I can almost get my fingers between the cross brace and the lexan. What I don't know is if it would create more lift if it was a filled in airfoil conforming to the top of the wing. Because the windshield  actually blends into the top lexan, it is in a crude way creating an airfoil.

_________________
Ron Lee
Tucson, Arizona

victorbravo(at)sbcglobal.
Guest

Posted: Sat Jan 26, 2008 1:25 pm Post subject: Cabin airfoil

Jaybannist(at)cs.com wrote:

 	  Quote: 	
		   In fact, most of the lift is provided by Newton, pushing on the bottom surface of the wing (With enough power, you can fly a barn door).  This speaks very loudly about the "expertise" of some of our most prolific posters, right? 

Louder than you think 
	




The real expert aerodynamicists out there have explained that the 

circulation flow pattern around the airfoil, and the amount of air being 

displaced downward, contributes far more than the Bernoulli effect or 

the "planing" effect you mention. I am not an expert on the circulation 

theory but I am aware that all of the real, employed, expert level 

aerodynamics people 100% believe in it.

victorbravo(at)sbcglobal.
Guest

Posted: Sat Jan 26, 2008 1:47 pm Post subject: Cabin airfoil

Larry, I'd be interested to know what design or designs the 701 is a 

copy of.Using this logic you could say that the P-51 or the Stealth 

fighter is an amalgam of previously designed parts.



LRM wrote:

 	  Quote: 	
		    I remind every one that the 701 is in fact a copy of a multitude of 

 parts used by previously like aircraft, by no means is it an original 

 design.

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