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lgold(at)quantum-associat
Guest

Posted: Tue Jan 22, 2008 10:07 pm Post subject: VGs

Joe,

 VGs are Vortex  Generators. If you Google these words you will find many descriptions,  e.g., http://en.wikipedia.org/wiki/Vortex_generator.

 Even though Chris Heintz  has not recommended them for the 701, some people are replacing their slats with  these VGs.

 Regards,

 Les 



 [quote]         From: owner-zenith-list-server(at)matronics.com    [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of    Joemotis(at)aol.com

Sent: Tuesday, January 22, 2008 7:54    PM

To: zenith-list(at)matronics.com

Subject: Re: Zenith-List:    VGs

   

   OK, I admit my ignorance. What are VG'S Variable geometry ?

    

   Thanks Joe Motis

    

   Do not archive



         Start the year off right. Easy ways to stay in shape in the new year. 

 	  Quote: 	
		  



href="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

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[b]

randy(at)rjhebertassoc.co
Guest

Posted: Wed Jan 23, 2008 5:52 am Post subject: VGs

Joe

 I have  always been reluctant to ask questions like that because of some of the  outbursts that appear on this list.

  

 Last night I  had the opportunity to attend the ASF Seminar on "5 Mistakes pilots  make."

  

 One issue  that came up is a pilots reluctance to ask !!!

 While the  issue was atc/weather it does apply throughout this set of  events

  

 My question  is that an earlier post indicated that VGs will increase wing  loading.

  

 Isn't that  what happens with the wing spar?  Isn't the spar's purpose to direct flow  over the top of the airfoil, thus increasing the wing  loading?

 And then  isn't the wing designed for that?

  

 I Don't  Know.  I am just asking.

  

  

  

  

  

 Randall J  Hebert

  

 Randall J Hebert  & Associates, Inc

 Consulting Civil / Structural  Engineers

 Lafayette, Louisiana

 PH  337-261-1976      -      FX 337-261-1977

  



   From: owner-zenith-list-server(at)matronics.com  [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of  Joemotis(at)aol.com

Sent: Tuesday, January 22, 2008 9:54  PM

To: zenith-list(at)matronics.com

Subject: Re: Zenith-List:  VGs

 

 OK, I admit my ignorance. What are VG'S Variable geometry ?

  

 Thanks Joe Motis

  

 Do not archive



   Start the year off right. Easy ways to stay in shape in the new year. 

[quote]



href="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c

[b]

jd(at)lawsonimaging.ca
Guest

Posted: Wed Jan 23, 2008 6:43 am Post subject: VGs

Les Goldner wrote:

 	  Quote: 	
		   

 

 David,

 I apologize for the outburst. 

 I didn't look at who the sender was until after sending the nasty email. The

 guys from Australia have been pushing VGs hard on this site, sometimes

 without stating that they were selling them, and mistook you for them.

 I know you are not trying to sell VGs and I hope you accept my apology.

 Les 


	


Greetings... I just wanted to chime in here that I am *extremely* happy 

with the VGs I installed on IGGY's elevator, and I'm thankful for the 

R&D done by 'the guys from Australia'. My 701 now has elevator authority 

at low speed, low power settings, and its nasty tendency to drop like a 

brick from 10-15 feet above the strip has bee tamed. I will *not* be 

removing my slats, but I think the elevator VGs are a Good Thing which 

correct one of the very few undesirable flight characteristics that the 

CH701 has.



-- 

Regards,  J.



flying:   Zenith STOL CH701/912 C-IGGY, 500 hrs.

building: Sonex #325 (C-FJNJ), Jabiru 3300/6, 99% completed



-------------------------------------------------

J. Davis, M.Sc. (computer science)

*NIX consulting, SysAdmin

email: jd at lawsonimaging.ca

voice: 519.289.1527 http://www.cleco.ca

c/o Brandywine Aviation 5507 Irish Dr., Appin, ON

N42 47.33  W081 36.50 31/13 2000+ x 60', elev: 740'

-------------------------------------------------



To most people the sky is the limit.

To those who love aviation, the sky is home.

randy(at)rjhebertassoc.co
Guest

Posted: Wed Jan 23, 2008 6:45 am Post subject: VGs

Leading edge slats is what I meant, not  spars.

  

  

  

  

  

  

  

 Randall J  Hebert

  

 Randall J Hebert  & Associates, Inc

 Consulting Civil / Structural  Engineers

 Lafayette, Louisiana

 PH  337-261-1976      -      FX 337-261-1977

  



   From: owner-zenith-list-server(at)matronics.com  [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Randall J.  Hebert

Sent: Wednesday, January 23, 2008 7:39 AM

To:  zenith-list(at)matronics.com

Subject: RE: Zenith-List:  VGs

 

 Joe

 I have  always been reluctant to ask questions like that because of some of the  outbursts that appear on this list.

  

 Last night I  had the opportunity to attend the ASF Seminar on "5 Mistakes pilots  make."

  

 One issue  that came up is a pilots reluctance to ask !!!

 While the  issue was atc/weather it does apply throughout this set of  events

  

 My question  is that an earlier post indicated that VGs will increase wing  loading.

  

 Isn't that  what happens with the wing spar?  Isn't the spar's purpose to direct flow  over the top of the airfoil, thus increasing the wing  loading?

 And then  isn't the wing designed for that?

  

 I Don't  Know.  I am just asking.

  

  

  

  

  

 Randall J  Hebert

  

 Randall J Hebert  & Associates, Inc

 Consulting Civil / Structural  Engineers

 Lafayette, Louisiana

 PH  337-261-1976      -      FX 337-261-1977

  



   From: owner-zenith-list-server(at)matronics.com  [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of  Joemotis(at)aol.com

Sent: Tuesday, January 22, 2008 9:54  PM

To: zenith-list(at)matronics.com

Subject: Re: Zenith-List:  VGs

 

 OK, I admit my ignorance. What are VG'S Variable geometry ?

  

 Thanks Joe Motis

  

 Do not archive



   Start the year off right. Easy ways to stay in shape in the new year. 

[quote]



href="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c





href="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

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[b]

dredmoody(at)cox.net
Guest

Posted: Wed Jan 23, 2008 7:23 am Post subject: VGs

If you review the posts I think you'll find that the VGs are being touted in many cases as a replacement for the slats since they produce less drag and may allow faster and more economical cruising. You are correct in that the effect of the leading edge slats is to keep the laminar flow longer into increasing AOA. The debate is whether slats or VGs do it better. Some guys may want both.... kinda like wearing a belt and suspenders.



The wing was designed for as much load as the anticipated flight enevelope would produce. I don't think that slow flight at high AOA would produce more wing load whether with slats or VGs or both. I think the risk is with the high energy aggressive maneuver. 



Ed



---- "Randall J. Hebert" <randy(at)rjhebertassoc.com> wrote: 

 	  Quote: 	
		   Leading edge slats is what I meant, not spars.

  

  

  

  

  

  

  

 Randall J Hebert

  

 Randall J Hebert & Associates, Inc

 Consulting Civil / Structural Engineers

 Lafayette, Louisiana

 PH 337-261-1976      -     FX 337-261-1977

  

 

 ________________________________

 

 From: owner-zenith-list-server(at)matronics.com

 [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Randall J.

 Hebert

 Sent: Wednesday, January 23, 2008 7:39 AM

 To: zenith-list(at)matronics.com

 Subject: RE: VGs

 

 

 Joe

 I have always been reluctant to ask questions like that because of some

 of the outbursts that appear on this list.

  

 Last night I had the opportunity to attend the ASF Seminar on "5

 Mistakes pilots make."

  

 One issue that came up is a pilots reluctance to ask !!!

 While the issue was atc/weather it does apply throughout this set of

 events

  

 My question is that an earlier post indicated that VGs will increase

 wing loading.

  

 Isn't that what happens with the wing spar?  Isn't the spar's purpose to

 direct flow over the top of the airfoil, thus increasing the wing

 loading?

 And then isn't the wing designed for that?

  

 I Don't Know.  I am just asking.

  

  

  

  

  

 Randall J Hebert

  

 Randall J Hebert & Associates, Inc

 Consulting Civil / Structural Engineers

 Lafayette, Louisiana

 PH 337-261-1976      -     FX 337-261-1977

  

 

 ________________________________

 

 From: owner-zenith-list-server(at)matronics.com

 [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of

 Joemotis(at)aol.com

 Sent: Tuesday, January 22, 2008 9:54 PM

 To: zenith-list(at)matronics.com

 Subject: Re: VGs

 

 

 OK, I admit my ignorance. What are VG'S Variable geometry ?

  

 Thanks Joe Motis

  

 Do not archive

 

 

 

 ________________________________

 

 Start the year off right. Easy ways to stay in shape

 <http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489>

 in the new year. 

 

 

 href="http://www.matronics.com/Navigator?Zenith-List">http://www.matronh

 ref="http://forums.matronics.com">http://forums.matronics.com

 href="http://www.matronics.com/contribution">http://www.matronics.com/c

daveaustin2(at)primus.ca
Guest

Posted: Wed Jan 23, 2008 7:28 am Post subject: VGs

Re VGs and wing loading..

 IMSO,  VGs on the wings only purpose is to  reduce the loss of lift due to higher angles of attack.  They will not give  "extra" lift at normal angle.  They do not seem to add any noticable  drag.

 Even so, I would not advise going into a 90  degree bank with full power at 130 mph just to prove this!

 Dave Austin  601HDS - 912, with VGs on wings  only.  I can hold the nose off the runway down to around 20 mph  IAS.

    [quote][b]

goodings(at)yorku.ca
Guest

Posted: Wed Jan 23, 2008 8:05 am Post subject: VGs

To George Swinford:



What an excellent, succint, splendid description of VGs.  Thank you - it

is the best statement I have seen, particularly with respect to

"energizing the boundary layer"!



John Goodings, C-FGPJ, CH601HD with R912S, Toronto/Carp/Ottawa.



VGs are vortex generators.  They are tiny vanes which project up from

the surface and create a vortex which flows downstream.  The vortex

mixes with the faster moving airstream above the surface and sweeps some

of it down into the slower boundary layer air, adding energy which tends

to keep the boundary layer attached to the surface.  On an airfoil,

keeping the boundary layer attached reduces the speed at which the

airfoil finally stalls.

larry(at)macsmachine.com
Guest

Posted: Wed Jan 23, 2008 8:19 am Post subject: VGs

Well said! And for the record, if you do need to ream someone, that's 

fine too, so long as you add "*do not archive*" below the comment so we 

don't have to

read it over and over again in the archives.



Larry McFarland 601HDS at www.macsmachine.com

do not archive



LRM wrote:

 	  Quote: 	
		   



 I don't see it like the guys from Australia as pushing, more like 

 providing info, which I like.  I wish more people would provide 

 information about their products especially when their seems to be a 

 lot of interest on the list.  Besides when I don't want to read about 

 something I just hit delete. No outburst, just delete.  It takes about 

 a half a second.  I've been on this list and other forums a long time 

 and have gotten into quite a few tit or tats which I have sometimes 

 regretted.  It's easy to get a rep of being an asshole if you are not 

 careful.  So, we should just choose our words more carefully.   Once 

 you hit the enter key, it's in writing and you can't take it back.  

 Take care, LRM  www.airhawg.com.

larry(at)macsmachine.com
Guest

Posted: Wed Jan 23, 2008 8:22 am Post subject: VGs

Hi Joe,

You can read about VG's at this link,

http://www.stolspeed.com/content.php

Good information, well done.



Larry McFarland 601HDS at www.macsmachine.com

do not archive

Joemotis(at)aol.com wrote:

 	  Quote: 	
		   OK, I admit my ignorance. What are VG'S Variable geometry ?

  

 Thanks Joe Motis

  

 Do not archive

victorbravo(at)sbcglobal.
Guest

Posted: Wed Jan 23, 2008 10:04 am Post subject: VGs

The slats create more "attached" flow, likely nothing laminar about it. 

The VG's accomplish the same OVERALL goal as the slats... adding more 

high energy air into the boundary layer... but accomplish this goal 

differently. Although I am not an engineer by any means, I can 

definitely see the difference. The VG's drag some swirling air back 

downward towards the wing surface, which allows the wig to operate at a 

higher AOA without stalling. The slats ACCELERATE the airflow FASTER 

across the top of the wing. I will leave it to the aerodynamicists to 

explain if or how or why one works better.



However, the reason we have chosen this boxy little airplane that was 

hit so hard with the ugly stick, is that it has the most exceptional 

STOL capability available in any low-cost non-ultralight airplane. Only 

the $100,000+ Monster Cubs, Fieseler Storch, Helio Couirier, and a 

couple of other highly specialized and 10X more expensive aircraft have 

this ability. So speaking only for myself I cannot imagine why you would 

do any modifications that would reduce this ability. If removing the 

slats makes the 701 more fuel efficient, but at the expense of the STOL 

ability, it seems to me you are losing part of the steak in order to get 

another couple of forkfuls of the salad 



The potential problm with VG's is indeed at higher speeds, or flying 

through severe turbulence... where the wing's "delayed" stall could 

allow a gust to apply more bending/twisting loads to the wing.

dredmoody(at)cox.net wrote:

 	  Quote: 	
		   



 If you review the posts I think you'll find that the VGs are being touted in many cases as a replacement for the slats since they produce less drag and may allow faster and more economical cruising. You are correct in that the effect of the leading edge slats is to keep the laminar flow longer into increasing AOA. The debate is whether slats or VGs do it better. Some guys may want both.... kinda like wearing a belt and suspenders.



 The wing was designed for as much load as the anticipated flight enevelope would produce. I don't think that slow flight at high AOA would produce more wing load whether with slats or VGs or both. I think the risk is with the high energy aggressive maneuver. 



 Ed

rsteele(at)rjsit.com
Guest

Posted: Wed Jan 23, 2008 10:14 am Post subject: VGs

INAAE (I'm not an aeronautical engineer) but I think replacing slats  

with VG's is probably a lot safer than adding VGs to an airfoil that  

wasn't designed to have either.  VGs will increase the AOA where  

stall happens.  Maneuvering speed is based on speed at which the wing  

will stall given a certain vertical wind gust.  The stall is  

instantaneous and keeps the wing from being overloaded by the gust.   

By adding VGs it might be possible to increase the stall AOA enough  

where to where the gust over stresses the wing before stall happens.   

Thus you might want to reduce maneuvering speed in a plane  where VGs  

have been added, like a HD/HDS/XL. etc.



Ron

On Jan 23, 2008, at 10:19 AM, <dredmoody(at)cox.net> <dredmoody(at)cox.net>  

wrote:



 	  Quote: 	
		   



 If you review the posts I think you'll find that the VGs are being  

 touted in many cases as a replacement for the slats since they  

 produce less drag and may allow faster and more economical  

 cruising. You are correct in that the effect of the leading edge  

 slats is to keep the laminar flow longer into increasing AOA. The  

 debate is whether slats or VGs do it better. Some guys may want  

 both.... kinda like wearing a belt and suspenders.



 The wing was designed for as much load as the anticipated flight  

 enevelope would produce. I don't think that slow flight at high AOA  

 would produce more wing load whether with slats or VGs or both. I  

 think the risk is with the high energy aggressive maneuver.



 Ed



 ---- "Randall J. Hebert" <randy(at)rjhebertassoc.com> wrote:

> Leading edge slats is what I meant, not spars.

>

> Randall J Hebert

>

> Randall J Hebert & Associates, Inc

> Consulting Civil / Structural Engineers

> Lafayette, Louisiana

> PH 337-261-1976      -     FX 337-261-1977

> ________________________________

>

> From: owner-zenith-list-server(at)matronics.com

> [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of  

> Randall J.

> Hebert

> Sent: Wednesday, January 23, 2008 7:39 AM

> To: zenith-list(at)matronics.com

> Subject: RE: VGs

> Joe

> I have always been reluctant to ask questions like that because of  

> some

> of the outbursts that appear on this list.

>

> Last night I had the opportunity to attend the ASF Seminar on "5

> Mistakes pilots make."

>

> One issue that came up is a pilots reluctance to ask !!!

> While the issue was atc/weather it does apply throughout this set of

> events

>

> My question is that an earlier post indicated that VGs will increase

> wing loading.

>

> Isn't that what happens with the wing spar?  Isn't the spar's  

> purpose to

> direct flow over the top of the airfoil, thus increasing the wing

> loading?

> And then isn't the wing designed for that?

>

> I Don't Know.  I am just asking.

>

> Randall J Hebert

>

> Randall J Hebert & Associates, Inc

> Consulting Civil / Structural Engineers

> Lafayette, Louisiana

> PH 337-261-1976      -     FX 337-261-1977

> ________________________________

>

> From: owner-zenith-list-server(at)matronics.com

> [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of

> Joemotis(at)aol.com

> Sent: Tuesday, January 22, 2008 9:54 PM

> To: zenith-list(at)matronics.com

> Subject: Re: VGs

> OK, I admit my ignorance. What are VG'S Variable geometry ?

>

> Thanks Joe Motis

>

> Do not archive

>

> ________________________________

>

> Start the year off right. Easy ways to stay in shape

> <http://body.aol.com/fitness/winter-exercise? 

> NCID=aolcmp00300000002489>

> in the new year.

> href="http://www.matronics.com/Navigator?Zenith-List">http:// 

> www.matronh

> ref="http://forums.matronics.com">http://forums.matronics.com

> href="http://www.matronics.com/contribution">http:// 

> www.matronics.com/c

>

maarten versteeg

Joined: 15 May 2007
Posts: 37
Location: San Antonio

Posted: Wed Jan 23, 2008 10:21 am Post subject: VGs

Hello Joe,



But the initial guess was not completely off the mark. In

a related avionics field of hang glider flying, VG actually

means variable geometry. In certain hang gliders the sail

tension is changed (reduced) to make the hang glider more

maneuverable during landing phase. This is variable

geometry since the leading edges of the wings are pushed

out less to achieve this reduction of tension.



Regards,

	Maarten

	601xl plans building wings



 	  Quote: 	
		   Time: 10:07:57 PM PST US

 From: "Les Goldner" <lgold(at)quantum-associates.com>

 Subject: RE: VGs

 

 Joe,

 VGs are Vortex Generators. If you Google these words you will find many

 descriptions, e.g., http://en.wikipedia.org/wiki/Vortex_generator.

 Even though Chris Heintz has not recommended them for the 701, some people

 are replacing their slats with these VGs.

 Regards,

 Les 

 

 

   _____  

 

 From: owner-zenith-list-server(at)matronics.com

 [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of

 Joemotis(at)aol.com

 Sent: Tuesday, January 22, 2008 7:54 PM

 Subject: Re: VGs

 

 

 OK, I admit my ignorance. What are VG'S Variable geometry ?

 

 Thanks Joe Motis

 

 Do not archive

_________________
Maarten Versteeg
601XL scratch building wings

kmccune

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

Posted: Wed Jan 23, 2008 10:31 am Post subject: Re: VGs

At least in the case of the 701 we already have the above stated risk of a delayed stall. The VGs may though allow a higher speed when this happens? 



I have not read a single comment that states that VGs by them selves replace the slats. But instead that a longer wing and VGs do. The basic claim is for a more conventional landing and glide ratio. This reduces the drop that results from the high drag of the 701 slats. But while also giving superior STOL performance. Now for a  high angle of attack spot landing the very reasons for removing the slats give it an advantage on short spot landings. Basically places were you shouldn't be landing anyway. (at least for 90% of us anyway)

Now in my case I need some good STOL performance when I eventually start landing at home. But I certainly don't need to take off in 50 feet or land in 100! I will still be kicking the STOL tail of those $100K planes with my little home built plane. I will just have a more comfortable, for me landing experience when I don't need to use a 100% effort landing.

_________________
“Always do what you are afraid to do.”
R.W. Emerson (1803-1882)

"Real freedom is the sustained act of being an individual." WW - 2009

"Life is a good deal...it's worth it" Feb 1969
Dorothy McCune

victorbravo(at)sbcglobal.
Guest

Posted: Wed Jan 23, 2008 11:29 am Post subject: VGs

Putting VG's on is a LOT LESS likely to do harm, than just arbitrarily 

removing the slats!



The "failure mode" of adding VG's  onto the wrong wing (like a Lancair 

leading edge for example) is that you make a bunch more drag and turn a 

laminar low drag airfoil into a higher drag turbulent airfoil. But you 

don't get a major change in the flight handling or the behavior of the wing.



The "failure mode" of removing the slats is that you have effectively 

put a whole different airfoil on the airplane, which will then have 

entirely different pitching moments (twisting force), entirely different 

flow and pressure patterns across control surfaces, etc. This is a LOT 

more risky and requires a LOT more engineering than simply forcing an 

early transition from laminar flow to turbulent flow.



The people who removed the slats managed to side-step this problem 

because they put the VG's on after the slats were removed, AND neither 

the slat or no-slat airfoil of the 701 was a critical laminar wing. But 

if you read carefully you will see several warnings to NOT remove the 

slats and fly without VG's.



Try removing the slats on a more critical wing (F-86) and you will see 

some very unsafe side-effects!



If you really want that extra drag reduction and STOL  capability, you 

have to go with the retractable slats, and if you do that you MUST make 

them MANUALLY retractable slats. None of this "airflow-operated slat" 

stuff without you having access to a wind tunnel and a big checkbook! 

You need a bin Johnson Bar lever in the cockpit with a strong detent 

latch. When you pull the lever the slats open and stay open. After you 

have levitated out of the tennis court and have established a positive 

rate of climb at about 50 MPH then you close the slats and enjoy the 

deag reduction, rate of climb, fuel efficiency, trans-sonic cruise, etc.



Sorry to appear a little too authoritative on this subject, but it 

appears that there are children playing with matches here without the 

background to do so. I ain't an engineer either but in aviation I do 

know where amateur knowledge ends and professional knowledge has to take 

over.



 	  Quote: 	
		   



 INAAE (I'm not an aeronautical engineer) but I think replacing slats 

 with VG's is probably a lot safer than adding VGs to an airfoil that 

 wasn't designed to have either.

victorbravo(at)sbcglobal.
Guest

Posted: Wed Jan 23, 2008 11:42 am Post subject: VGs

Forgive my ranting but I do have some amount of exotic STOL experience. 

Not bushplanes, but in high performance racing sailplanes. In 

competition soaring, we often had to make (what would otherwise be 

considered) emergency off-airport landings. I've landed fixed wing 

airplanes (gliders with NO go-around capability) on helicopter pads, 

backyards, farm fields, parking lots, etc.



Believe me, having a BAD glide ratio and a HIGH descent rate is exactly 

what you WANT in STOL operations. I own a Taylorcraft, which can land in 

only 300 feet, but it is not a good STOL plane because it  "floats" and 

glides too well. The real key to STOL is being able to adjust the amount 

of drag, descent rate, and "float" your airplane has.



A better glide is NOT superior STOL performance. Being ale to pull a 

lever and go from good glide to bad glide, low drag to high drag, and 

back and forth as the situation demands... is the absolute key to 

effective and SAFE STOL.



In the 701, the primary lever for this is the throttle. Second lever is 

the control stick. When you pull the first lever all the way back you 

SHOULD be coming down at a 30 or 45 degree angle, making a lot of drag 

and with no tendency to float on touchdown. The second lever adjusts how 

much airspeed (flare authority) you have while descending. When you push 

the first lever forward a little bit, the plane slows or stops 

descending. Adjusting these two levers allows you to hit the spot you 

want to hit at the speed you want to hit it. THAT is STOL ability.



Having an airplane that does NOT come down like a free falling safe when 

you pull the throttle lever back means you have LESS control of where 

and how fast you hit the ground. My T-craft is a GREAT airplane that can 

be used in limited STOL applications, but it suffers from this exact 

problem. It is too efficient at the times you need to make a lot of drag.



Bill

 	  Quote: 	
		   



 The basic claim is for a more conventional landing and glide ratio. This reduces the drop that results from the high drag of the 701 slats. But while also giving superior STOL performance. Now for a  high angle of attack spot landing the very reasons for removing the slats give it an advantage on short spot landings.

kmccune

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

Posted: Wed Jan 23, 2008 2:52 pm Post subject: Re: VGs

We are speaking of a 701.



Here is what Mr Heintz says:

"From a design standpoint, I have no objection to the removal of the leading edge slats (and their attachment brackets) and replacing them with VGs," Now he goes on to say that the STOL ability will diminish. But he is speaking about a standard wing span. Not the long wing, a mod that he has been known to allow.



Thank you for your opinion.

 	  victorbravo(at)sbcglobal. wrote: 	
		  Putting VG's on is a LOT LESS likely to do harm, than just arbitrarily 

removing the slats!



The "failure mode" of adding VG's  onto the wrong wing (like a Lancair 

leading edge for example) is that you make a bunch more drag and turn a 

laminar low drag airfoil into a higher drag turbulent airfoil. But you 

don't get a major change in the flight handling or the behavior of the wing.



The "failure mode" of removing the slats is that you have effectively 

put a whole different airfoil on the airplane, which will then have 

entirely different pitching moments (twisting force), entirely different 

flow and pressure patterns across control surfaces, etc. This is a LOT 

more risky and requires a LOT more engineering than simply forcing an 

early transition from laminar flow to turbulent flow.



The people who removed the slats managed to side-step this problem 

because they put the VG's on after the slats were removed, AND neither 

the slat or no-slat airfoil of the 701 was a critical laminar wing. But 

if you read carefully you will see several warnings to NOT remove the 

slats and fly without VG's.



Try removing the slats on a more critical wing (F-86) and you will see 

some very unsafe side-effects!



If you really want that extra drag reduction and STOL  capability, you 

have to go with the retractable slats, and if you do that you MUST make 

them MANUALLY retractable slats. None of this "airflow-operated slat" 

stuff without you having access to a wind tunnel and a big checkbook! 

You need a bin Johnson Bar lever in the cockpit with a strong detent 

latch. When you pull the lever the slats open and stay open. After you 

have levitated out of the tennis court and have established a positive 

rate of climb at about 50 MPH then you close the slats and enjoy the 

deag reduction, rate of climb, fuel efficiency, trans-sonic cruise, etc.



Sorry to appear a little too authoritative on this subject, but it 

appears that there are children playing with matches here without the 

background to do so. I ain't an engineer either but in aviation I do 

know where amateur knowledge ends and professional knowledge has to take 

over.



 	  Quote: 	
		   



 INAAE (I'm not an aeronautical engineer) but I think replacing slats 

 with VG's is probably a lot safer than adding VGs to an airfoil that 

 wasn't designed to have either.

keystone(at)gci.net
Guest

Posted: Thu Jan 24, 2008 9:42 am Post subject: VGs

I feel a need to weigh in to this  discussion.

  

 I have flown my 801:

    With slats   
With slats with VGs   
Without slats   
and without slats with VGs  The VGs do not add anything when the slats are  attached.  No improvement on the high end or at slow speeds.

  

 The plane without slats and without VGs is a faster  plane.   I don't have my log book here but it like 8-10  mph faster in cruise but is much faster on the bottom end.  The  plane stalls in a predictable manner.  It is just much much faster.   

  

 The plane without slats but with VGs is as fast as  with no slats.  It is like 8 or 10 mph faster.  The stall is 15 mph or  so faster.  I don't know why it works better on the 701 than the 801.    With VGs I was over the fence at 65 and with slats I was over the  fence as low as 50.

  

 I did not find the center of lift changing  when the slats were removed.  I heard (from this chat room it think) that  if you cover the slats, the plane's center of lift moves forward so  much you need to recalculate CG to remain in the proper %  of MAC.  I do not think the slats they provide much  lift.  I think they accelerate the air over the wing.  There is a hole  in the wing at about 10% of MAC.  

  

 I have long been an advocate for VGs on the bottom  of the horizontal stabilizer.  I fly into soft beaches.  I have always  wanted more elevator control.  VGs on the bottom of the elevator give you  more elevator control.  The VGs on the bottom of the HS add more to the  elevator authority than the larger tail.

  

 JG (the guy from down under) gave me a set of VGs  to experiment with.  I thank him.  The first VGs I made were from  standard L.  1 1/2" long with the front cut off at a 45 degree angle.   I progressed to 1/2"x1/2"x1/16" AL angle, 1" long with the front cut at a 45  degree angle.  I read a study that said the shape doesn't matter.  I  have not found a difference in VGs between the standard L, 1/2 angle or  feathers.  I would say the feather look nicer than the AL VGs.

  

 One nice thing about having the EXPERIMENTAL on the  side of the plane is you can go into phase 1 testing again.  Every time I  make a major change to the plane I approach the flight as if it was the first  flight .  Some changes work some do not.  

  

 I still have plans to modify the wing tip to  increase lift.  So many projects too little time.

  

 Bill Wilcox

 N801BW

 350 hrs

 Valdez, Alaska

 In storage for winter performing 4th condition  inspection.

 Anticipating installing floats this  spring.

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