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Land Shorter VG's on Firestar II
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pj.ladd(at)btinternet.com
Guest

Posted: Tue Mar 28, 2006 5:48 am Post subject: Land Shorter VG's on Firestar II

Did I hear someone call for a wind tunnel....?>>



Hey, thats great. Can you do smoke or tufts? Pics would be nice but that is 

asking a bit much.



The position that I am desperately trying to defend here is my contention 

that the tail plane alone does not exert lift. When the elevator is applied 

the tail plane/elevator combination DOES assume a rough airofoil shape and 

consequently produces some lift.

In that case with VG`s on the underside of the tailplane and the elevator in 

the `up` position they would do exactly what they do on the top of a wing. 

Keep the boundary layer from breaking away. That would increase the 

effectiveness of the `up` elevator.



Can you prove or disprove?



Cheers



Pat



do not archive 



--

John Jung

Joined: 10 Jan 2006
Posts: 108
Location: Surprise, AZ, USA

Posted: Tue Mar 28, 2006 6:38 am Post subject: Re: Land Shorter VG's on Firestar II

Group,



I tried a couple of times yesterday to get to talk to Joa from Landshorter. I also e-mailed him with a copy of Chris Mallory's post, so that he could confirm or correct. I will report to the list after I hear from him.



do not archive

_________________
John Jung
Firestar II N6163J
Surprise, AZ

John Jung

Joined: 10 Jan 2006
Posts: 108
Location: Surprise, AZ, USA

Posted: Tue Mar 28, 2006 6:54 am Post subject: Re: Land Shorter VG's on Firestar II

Group,



Joa did respond to the list last night. I should read everything before I reply to anything in the morning. He changed the subject line. 



Anyway, what he accomplished with VGs on the underside of the horizontal stab is exactly the way my Firestar II flys now. So adding them to my stab would be a waste of time and money.

_________________
John Jung
Firestar II N6163J
Surprise, AZ

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Tue Mar 28, 2006 6:55 am Post subject: Land Shorter VG's on Firestar II

Instead of agreeing with or denying your position, let me simply muddy 

the waters:

For the last couple years I have been designing and building radio 

control airplanes out of fan fold insulating foam and typically I have 

given all of them a very thick airfoil because it makes it easier to 

build a light wing, plus creates other good flying attributes. Lately I 

have gone the opposite direction and currently have two airplanes that 

have only a flat sheet wing, reinforced by a carbon fiber tube as a main 

spar. And they fly just as good as the ones with a real airfoil.

Obviously we are talking very light wing loadings here, but in certain 

applications, a flat surface produces all the lift you need. I attached 

some pics, maybe they will go through.



In the case of a Kolb, we have several degrees of incidence between the 

wing and the tail, and if the airplane is properly trimmed, the elevator 

will be exactly aligned with the horizontal stab while in flight, and 

this will be providing the proper downforce to balance the center of 

lift of the wing with the thrust and load of the wing. And if the 

elevator/stab is providing downforce when undeflected, then...?

(And it must of necessity be creating downforce, due to the decalage 

between the wing and the tail. Also, I strongly doubt that the center of 

lift of the Kolb airfoil would ever match the center of gravity of the 

airplane. Because if it would, then no decalage between the wing and 

tail would be necessary. Of course, it would make for a very unpleasant 

to fly, generally unstable airplane)



Richard Pike

MKIII N420P (420ldPoops)

pat ladd wrote:

 	  Quote: 	
		   



 Did I hear someone call for a wind tunnel....?>>



 Hey, thats great. Can you do smoke or tufts? Pics would be nice but that is 

 asking a bit much.



 The position that I am desperately trying to defend here is my contention 

 that the tail plane alone does not exert lift. When the elevator is applied 

 the tail plane/elevator combination DOES assume a rough airofoil shape and 

 consequently produces some lift.

 In that case with VG`s on the underside of the tailplane and the elevator in 

 the `up` position they would do exactly what they do on the top of a wing. 

 Keep the boundary layer from breaking away. That would increase the 

 effectiveness of the `up` elevator.



 Can you prove or disprove?



 Cheers



 Pat



 do not archive

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

n79rt(at)kilocharlie.us
Guest

Posted: Tue Mar 28, 2006 12:16 pm Post subject: Land Shorter VG's on Firestar II

The position that I am desperately trying to defend here is my

contention 

that the tail plane alone does not exert lift. When the elevator is

applied 

the tail plane/elevator combination DOES assume a rough airofoil shape

and 

consequently produces some lift.

In that case with VG`s on the underside of the tailplane and the

elevator in 

the `up` position they would do exactly what they do on the top of a

wing. 

Keep the boundary layer from breaking away. That would increase the 

effectiveness of the `up` elevator.



Can you prove or disprove?



Cheers



Pat



<snip>

OK Pat...I'll answer your question with another question...if a "flat"

surface can't generate lift then how the heck did the Concorde ever fly?

(Or the Mirage, or F-102 Delta Dart)



Point being anything that can deflect air one way will produce lift (or

just call it FORCE) the other way...it's that old "For every action

there is an equal and opposite REACTION" thing...Newton wasn't it?



Jeremy

beauford(at)tampabay.rr.c
Guest

Posted: Tue Mar 28, 2006 5:16 pm Post subject: Land Shorter VG's on Firestar II

Brother Patrick...

Prove...?    Disprove...?  Lift...?  Your induced-airfoil theory makes

intuitive sense to me...



But, nossir, I can only offer my empirical before and after

impressions... flare the little airplane

down in ground effect, power off,  with my flabby butt strapped in the

pointy end, and there is a markedly

reduced tendency to perform a soil-sampling drill when the VG's are

installed on the bottom of the

tail...



Per your inquiries...   Smoke is available if you furnish the

Macanudo...  I no longer do tufts... it's a

matter of principle, Sir...  Pictures are most assuredly out of the

question... we have our standards....



Beauford of Brandon

FF#076

Do Not Archive



---

Russ Kinne

Joined: 27 Jan 2006
Posts: 182

Posted: Tue Mar 28, 2006 6:16 pm Post subject: Land Shorter VG's on Firestar II

Pat

As I understand it, the tailplane does create "lift", but in  an   

upward direction -- because it is behind the CG.

In effect, it  keeps the tail DOWN. Which is why it's basically an  

upside-down wing, and the VG's should be on the underside.

I think your contention is wrong, desperate or not. but I could be  

wrong; that happened once. Or twice.

Best,

Russ

do  not archive

On Mar 28, 2006, at 8:43 AM, pat ladd wrote:



 	  Quote: 	
		   



 Did I hear someone call for a wind tunnel....?>>



 Hey, thats great. Can you do smoke or tufts? Pics would be nice but  

 that is

 asking a bit much.



 The position that I am desperately trying to defend here is my  

 contention

 that the tail plane alone does not exert lift. When the elevator is  

 applied

 the tail plane/elevator combination DOES assume a rough airofoil  

 shape and

 consequently produces some lift.

 In that case with VG`s on the underside of the tailplane and the  

 elevator in

 the `up` position they would do exactly what they do on the top of  

 a wing.

 Keep the boundary layer from breaking away. That would increase the

 effectiveness of the `up` elevator.



 Can you prove or disprove?



 Cheers



 Pat



 do not archive



 --

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Wed Mar 29, 2006 6:16 am Post subject: Land Shorter VG's on Firestar II

Possums,



My comment about JOA's lost credibility had to do with his statement 

that the VGs on the tail would enable the standard gear leg Kolb to 

land at high angles of attack without the tail hitting first. This 

could only be true if the tail was generating UPWARDS lift which is 

most definitely not the case in a Kolb with the stick back and nose 

pitching upwards. By definition, a high wing AOA the tail is low, so 

JOAs statement is clearly impossible.



My comment had nothing to do with the location of the VGs on the tail. 

I agree that with the normal configuration horizontal stabilizer (the 

tail lift vector is down) the VGs on the bottom could help generate 

more downward lift at high TAIL AOA. High tail AOA (stick all the way 

back) produces low tail position relative to the rest of the airplane.



I hope this clears up my statement, probably didn't but that is the 

best I can do.



Thom in Buffalo

do not archive

  



       At 07:40 AM 3/27/2006, you wrote:

       >

<jtriddle(at)adelphia.net>

       >

       >This JOA guy has lost all credibility with me due to his 

statement

       >about the tail stalling first causing the tail to be low.

       I don't know about that - if you do a Google Search on

       "horizontal stabilizer" & "vortex generators" you will find out

       that everybody recommends putting them on the "bottom" of

       the Horizontal stabilizer, not just this JOA guy. Even in the

       GA planes.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Possum

Joined: 12 Jan 2006
Posts: 112
Location: Georgia

Posted: Sat Apr 01, 2006 8:12 pm Post subject: Land Shorter VG's on Firestar II

At 09:54 AM 3/28/2006, you wrote:

 	  Quote: 	
		  



Group,



Joa did respond to the list last night. I should read everything 

before I reply to anything in the morning. He changed the subject line.



Anyway, what he accomplished with VGs on the underside of the 

horizontal stab is exactly the way my Firestar II flys now. So 

adding them to my stab would be a waste of time and money.



--------

John Jung


	


John

I'll agree with you on that .... but since I ordered another 20 VGs, 

I thought I would put them on either side of the Rudder.

So, today I spent 45 minutes with my nose stuck up in the air...at 

"what ever angle" it is at 29 - 32 mph and

testing the rudder input. You may not have noticed yet that when you 

slow the stall speed down that much with

the VGs,  the rudder does not respond like it did at 40 mph. Well, I 

think you will recover the difference by

installing those little things ...like he says - in front of the 

rudder hinges. Flying 30+- mph indicated - thermals, not too

bad ( but bad enough that no one else was flying ), still drops a 

wing once in a while, kick the opposite rudder, and it picks it right 

back up again. Used to be sloppy. I've got cars stopping below me - 

thinking I'm some kind of a box-kite ...cool. Another $ 30 well spent !!

planecrazzzy
Guest

Posted: Sun Apr 02, 2006 1:25 pm Post subject: Re: Land Shorter VG's on Firestar II

Hey Possum,

                   Can you post some more pictures ???

.

.  

Thanks,

.

.  Gotta Fly...

 Mike in MN / N381PM

.

.

.

.



[/quote]

John

I'll agree with you on that .... but since I ordered another 20 VGs, 

I thought I would put them on either side of the Rudder.

So, today I spent 45 minutes with my nose stuck up in the air...at 

"what ever angle" it is at 29 - 32 mph and

testing the rudder input. You may not have noticed yet that when you 

slow the stall speed down that much with

the VGs,  the rudder does not respond like it did at 40 mph. Well, I 

think you will recover the difference by

installing those little things ...like he says - in front of the 

rudder hinges. Flying 30+- mph indicated - thermals, not too

bad ( but bad enough that no one else was flying ), still drops a 

wing once in a while, kick the opposite rudder, and it picks it right 

back up again. Used to be sloppy. I've got cars stopping below me - 

thinking I'm some kind of a box-kite ...cool. Another $ 30 well spent !![/quote]

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