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Airfoils on empanage

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shilocom(at)mcmsys.com
Guest

Posted: Sun Sep 17, 2006 7:55 pm Post subject: Airfoils on empanage

Does anyone have some pics or drawings with  dimensions of the "airfoil" type empennage that I think was used on the  Late model 4 and up?  I think it was  an option and used plywood ribs that were either bowed in like a symmetrical  airfoil or maybe just bowed on top like the wing airfoil.  

  

 Also what was the Idea of using it as  opposed to a "flat" surface on the empennage?  

  

 Was it used only on the horizontal and  vertical stabs or did it include the rudder and elevator?  

  

 Is it still used today on the mod VII  etc?  

  

 Blue Skies

Bob Unternaehrer

shilocom(at)mcmsys.com (shilocom(at)mcmsys.com)

roncarolnikko(at)hotmail.
Guest

Posted: Sun Sep 17, 2006 8:40 pm Post subject: Airfoils on empanage

Bob My Speedster has light plywood ribs in the stabs and elavator/rudder.  

Non on the fuselage other than the wooden stringer along each side.   Did 

you ever get your valley redrive to work?  Still tinkering with mine.     

Ron NB Ore

 	  Quote: 	
		  From: "Bob Unternaehrer" <shilocom(at)mcmsys.com>

Reply-To: kitfox-list(at)matronics.com

To: "Kitfox List" <kitfox-list(at)matronics.com>

Subject: Airfoils on empanage

Date: Sun, 17 Sep 2006 23:03:53 -0500



Does anyone have some pics or drawings with dimensions of the "airfoil" 

type empennage that I think was used on the Late model 4 and up?  I think 

it was an option and used plywood ribs that were either bowed in like a 

symmetrical airfoil or maybe just bowed on top like the wing airfoil.



Also what was the Idea of using it as opposed to a "flat" surface on the 

empennage?



Was it used only on the horizontal and vertical stabs or did it include the 

rudder and elevator?



Is it still used today on the mod VII etc?



Blue Skies

Bob Unternaehrer

shilocom(at)mcmsys.com


	


_________________________________________________________________

lcfitt(at)sbcglobal.net
Guest

Posted: Sun Sep 17, 2006 9:26 pm Post subject: Airfoils on empanage

Bob,



The airfoil was not continuous across the Horizontal Stab - elevator, but 

rather ribs that created a rough airfoil shape on the horizontal and 

elevator separately converging at the tube diameters at the hinge line.



I created an overall airfoil shape largely due to ignorance as I had 

purchased the trim tab cutout and didn't know how to create the room in the 

horizontal stab for the servo and U-channel that was the hinge line at the 

trim tab.  I made the ribs of medium density foam with glass laminations on 

the flats.  The foam was 1/4" and there is a drawing on the Sportflight web 

site of the gap seal design.



http://www.sportflight.com/cgi-bin/uploader.pl?action=view&epoch=1041348095



Regarding the airfoil: There was talk on the Lancair list after a couple of 

stall spin accidents where a suggestion was made that the elevator might 

have stalled contributing to the inability of the pilot to recover from the 

stall.  I had never considered this, but the suggestion was made by several 

of the gurus on that list that a properly designed airfoil would reduce the 

tendency of the elevator to stall.



Lowell



---

barry(at)pgtc.com
Guest

Posted: Mon Sep 18, 2006 1:48 am Post subject: Airfoils on empanage

Bob, it was an option on IV when I bought my kit in  about 1996 and I didn't buy the option.  I recall it was simply some ribs  that formed bottom and top of the horizontal and both side of the  verticle.  I'm sure it was for drag reduction and also pretty sure it  helped some.  There were also false ribs for the bottom of the wing, not to  change the shape but to keep the fabric from sinking in so much between the real  ribs and also to reduce drag and help maintain the air foil type.  Same  thing for the fabric covered landing gear, there were ribs for that.  My  IV was very draggy, 95 mph max, even with the 912 S engine.  I  didn't even have fairings on the struts.

  

 After flying it for 5 years, I fabricated fairings  for the struts and picked up 5 mph.

  

 If I had to do it all over again, I would get all  that drag reduction stuff and the metal landing gear.  

  

 Barry West

  

 [quote]   ---

jimlc(at)att.net
Guest

Posted: Mon Sep 18, 2006 7:46 am Post subject: Airfoils on empanage

Bob,

 I have all of the foils on my Series 5 and will be working on my plane today.  I will take pictures and send them to you.  As I remember when I purchased my kit, they were standard on the Speedsters and an option for me.  I think they might have even been called Speedster air foils.

 Jim Crowder



 At 10:03 PM 9/17/2006, you wrote:

 [quote]Does anyone have some pics or drawings with dimensions of the "airfoil" type empennage that I think was used on the Late model 4 and up?  I think it was an option and used plywood ribs that were either bowed in like a symmetrical airfoil or maybe just bowed on top like the wing airfoil.  

  

 Also what was the Idea of using it as opposed to a "flat" surface on the empennage?  

  

 Was it used only on the horizontal and vertical stabs or did it include the rudder and elevator?  

  

 Is it still used today on the mod VII etc?  

  

 Blue Skies

 Bob Unternaehrer

 shilocom(at)mcmsys.com (shilocom(at)mcmsys.com)

 

  	  Quote: 	
		  

[/b] 	
[b]

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Mon Sep 18, 2006 11:46 am Post subject: Airfoils on empanage

On Sep 18, 2006, at 7:24 AM, Lowell Fitt wrote:

 	  Quote: 	
		   I had never considered this, but the suggestion was made by several of 

 the gurus on that list that a properly designed airfoil would reduce 

 the tendency of the elevator to stall.


	


This is an interesting subject, Lowell, and as you probably know, I 

have experimented for years with airfoils in the X-Plane flight 

simulator. It is the reason a French friend helped Kurt to make a good 

profile for his wing struts.

 From this "digital experience" I know that any profile has a 

coefficient of lift, of drag and moment. Depending of the profile, the 

stall angle may vary from 16 to 20 degrees. The simulator comes with a 

good library of standard airfoils, most of them NACA. From that, it is 

obvious that a good lifting airfoil will stall later than say, a flat 

plate. But it is not very much, we are talking of a couple of degrees 

of AoA.

However, the rudder and elevator is an airfoil that changes shape. 

Stick and pedals will change the profile, making it with more or less 

camber. How does that affect the angle of stall? Here, digital 

modelling is more uncertain. A rudder with an angle is not like say, my 

under-cambered wing.

Will a volumetric control surface work better than a flat plate? 

Certainly because it will give more lift, which is then translated into 

rotation moment in one or the other axis. Will the stalling of it be 

delayed? I think so, but IMHO, only by a very small margin.

My sailboat is very special. The rudder is hanging from a small "keel" 

called a skeg. The rudder and the skeg are shaped as a NACA profile, 

the rudder being faired in the skeg, a bit like your foam and 

glassfiber gap sealing. It creates a super powerful rudder and a ship 

that can be steered with the little finger, even in a gale wind. So, an 

good airfoil is better than a flat plate, that's for sure.



Cheers,

Michel

_________________
Kitfox 3 - Jabiru 2200

janderson412(at)hotmail.c
Guest

Posted: Mon Sep 18, 2006 1:06 pm Post subject: Airfoils on empanage

Yes, the effort is surely worth it re drag reduction. I've gone to a bit of 

effort on this and still air cruise is 100kts (GPS) Series V EA81





From: "Barry West" <barry(at)pgtc.com>

Reply-To: kitfox-list(at)matronics.com

To: <kitfox-list(at)matronics.com>

Subject: Re: Airfoils on empanage

Date: Mon, 18 Sep 2006 04:50:19 -0500

Bob, it was an option on IV when I bought my kit in about 1996 and I didn't 

buy the option.  I recall it was simply some ribs that formed bottom and top 

of the horizontal and both side of the verticle.  I'm sure it was for drag 

reduction and also pretty sure it helped some.  There were also false ribs 

for the bottom of the wing, not to change the shape but to keep the fabric 

from sinking in so much between the real ribs and also to reduce drag and 

help maintain the air foil type.  Same thing for the fabric covered landing 

gear, there were ribs for that.  My IV was very draggy, 95 mph max, even 

with the 912 S engine.  I didn't even have fairings on the struts.



After flying it for 5 years, I fabricated fairings for the struts and picked 

up 5 mph.



If I had to do it all over again, I would get all that drag reduction stuff 

and the metal landing gear.



Barry West



---

smokey_bear_40220(at)yaho
Guest

Posted: Mon Sep 18, 2006 3:23 pm Post subject: Airfoils on empanage

Very well written Michel,

I don't have my airfoil book unpacked yet, but I seem

to remember a difference in stall around 4 degrees

between flat plate and a medium thin airfoil.

Thicker airfoils go to higher AOA's before stall. 

Eventually you get round.  Does a ball ever stall, or

is it always stalled?  What is the AOA of a ball

anyway?

Leading edge geometry makes a big difference, but for

our tails, it is the same nose on a flat or profiled

tail.

The much modified, and I think improved, tail section

made by Lowell is on my computer as near ultimate

perfection for the job.  His "eye balled engineering"

has made his plane go fast ya' know.  What a gap seal!

 Be interesting to do a wind tunnel comparison.

Remember the problems that the Cessna Cardinal had on

the first models?  The tail would stall in the flare

and you'd land nose first.  An inverted slot was added

to improve the downward lift before stalling and that

fixed it.  If you look at an old F-4 tail, it has

inverted slots too, plus a multicurved profile.

Flat plates have a problem with a thicker boundry

layer that the elevator can hide in.  Movement inside

of this boundry layer does little, making it feel like

the elevator is in the "loose stearing" mode.  I

understand SS twisted the elevator to allow one side

to be at the top of the boundry layer while the other

side is at the bottom.  This way, any movement got a

response.  It reduces flutter too.

A profiled airfoil fills this boundry layer shadow and

keeps it thin and attached.  Better elevator response

and less drag.

The big difference is when you displace the

elevator/rudder a large amount and try to keep the

lifting side (usually the bottom) from stalling.  A

good curved profile will do better than a sudden

change in a flat plate.

Then there is that gap....

So a profiled tail should give a little better control

with a little less drag.  A good gap seal should do

about as much good again, on top of that.

Results may vary....

Kurt S.  S-5

--- Michel Verheughe <michel(at)online.no> wrote:

 	  Quote: 	
		   On Sep 18, 2006, at 7:24 AM, Lowell Fitt wrote:

 > I had never considered this, but the suggestion

 was made by several of 

 > the gurus on that list that a properly designed

 airfoil would reduce 

 > the tendency of the elevator to stall.

 This is an interesting subject, Lowell, and as you

 probably know, I 

 have experimented for years with airfoils in the

 X-Plane flight 

 simulator. It is the reason a French friend helped

 Kurt to make a good 

 profile for his wing struts.

  From this "digital experience" I know that any

 profile has a 

 coefficient of lift, of drag and moment. Depending

 of the profile, the 

 stall angle may vary from 16 to 20 degrees. The

 simulator comes with a 

 good library of standard airfoils, most of them

 NACA. From that, it is 

 obvious that a good lifting airfoil will stall later

 than say, a flat 

 plate. But it is not very much, we are talking of a

 couple of degrees 

 of AoA.

 However, the rudder and elevator is an airfoil that

 changes shape. 

 Stick and pedals will change the profile, making it

 with more or less 

 camber. How does that affect the angle of stall?

 Here, digital 

 modelling is more uncertain. A rudder with an angle

 is not like say, my 

 under-cambered wing.

 Will a volumetric control surface work better than a

 flat plate? 

 Certainly because it will give more lift, which is

 then translated into 

 rotation moment in one or the other axis. Will the

 stalling of it be 

 delayed? I think so, but IMHO, only by a very small

 margin.

 My sailboat is very special. The rudder is hanging

 from a small "keel" 

 called a skeg. The rudder and the skeg are shaped as

 a NACA profile, 

 the rudder being faired in the skeg, a bit like your

 foam and 

 glassfiber gap sealing. It creates a super powerful

 rudder and a ship 

 that can be steered with the little finger, even in

 a gale wind. So, an 

 good airfoil is better than a flat plate, that's for

 sure.

 Cheers,

 Michel

__________________________________________________

smokey_bear_40220(at)yaho
Guest

Posted: Mon Sep 18, 2006 3:41 pm Post subject: Airfoils on empanage

I used the plywood ribs for the H. Stab, but used a

copy machine and only the one largest rib as a

template for the V. Stab.  I just resized the largest

rib down with the copier to fit in each smaller space

using the copy machine. Then I cut foam for the rib,

but you can stick to the plywood if you want.



Kurt S.



--- Bob Unternaehrer <shilocom(at)mcmsys.com> wrote:



 	  Quote: 	
		   Does anyone have some pics or drawings with

 dimensions of the "airfoil" type empennage that I

 think was used on the Late model 4 and up?  I think

 it was an option and used plywood ribs that were

 either bowed in like a symmetrical airfoil or maybe

 just bowed on top like the wing airfoil.  

 

 Also what was the Idea of using it as opposed to a

 "flat" surface on the empennage?  

 

 Was it used only on the horizontal and vertical

 stabs or did it include the rudder and elevator?  

 

 Is it still used today on the mod VII etc?  

 

 Blue Skies

 Bob Unternaehrer

 shilocom(at)mcmsys.com


	


__________________________________________________

dan(at)azshowersolutions.
Guest

Posted: Mon Sep 18, 2006 4:31 pm Post subject: Airfoils on empanage

Kurt, I just picked up this thread so forgive if redundancy occurs...I am about to put ribs in my vertical stab and wondered what kind of foam did you use and how thick? did you wrap them w/ anything? 

  Thanks,

  Dan



kurt schrader <smokey_bear_40220(at)yahoo.com> wrote:

  [quote]--> Kitfox-List message posted by: kurt schrader 



I used the plywood ribs for the H. Stab, but used a

copy machine and only the one largest rib as a

template for the V. Stab. I just resized the largest

rib down with the copier to fit in each smaller space

using the copy machine. Then I cut foam for the rib,

but you can stick to the plywood if you want.



Kurt S.



--- Bob Unternaehrer wrote:



[quote] Does anyone have some pics or drawings with

 dimensions of [quote][b]

smokey_bear_40220(at)yaho
Guest

Posted: Mon Sep 18, 2006 5:38 pm Post subject: Airfoils on empanage

Hey Dan,



ACS has some great yellow foam something like SS used

for gap seals, but a little lighter.  I think I used

2" thick and doubled where needed.  A 4' x 4' piece.



I just shaped the foam in as a full leading edge piece

to the widest part, with 3 ribs - top, bottom and

middle - back from there.  The top and bottom plywood

ribs were the sanding forms to shape to.  Looks almost

solid.  A big hotwire would have been easier....



You can epoxy some very light fiberglass over the

foam, but I just covered with fabric and left it that

way.  It will probably destroy the foam when I need to

recover later though.  The polybrush probably

penetrated the surface of the foam for a bit and I

expect it will rip out with the fabric in another 25

years.  Always hangared.  



Not a hard job to redo the foam though.  Next time I

will use the epoxy and light glass over it.  The model

hobby shops have the best light weight glass I found.



I weighed the parts, but forgot by now how much it

added.  I seem to remember 6 oz max without the

fiberglass.  You can hollow out the foam, careful to

leave a web, and offset the weight of the glass a

little.  My tail still came in light and I am nose

heavy, so it wouldn't have been a problem to glass it.



If you haven't covered the H stab, now is the time to

put in a good gap seal.  Just add a piece of foam to

the rear of the stab, front of the elevator, or both,

your choice, and leave enough room for the fabric. 

Shape to allow full control movement and glass on.



I didn't do it and now have to use tape.  The foam is

just a little more aerodynamic.



Kurt S.



--- Dan Billingsley <dan(at)azshowersolutions.com> wrote:



 	  Quote: 	
		   Kurt, I just picked up this thread so forgive if

 redundancy occurs...I am about to put ribs in my

 vertical stab and wondered what kind of foam did you

 use and how thick? did you wrap them w/ anything? 

   Thanks,

   Dan


	


__________________________________________________

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Tue Sep 19, 2006 4:55 am Post subject: Airfoils on empanage

 	  Quote: 	
		   From: kurt schrader [smokey_bear_40220(at)yahoo.com]

 Remember the problems that the Cessna Cardinal had on

 the first models?


	


Sir, no Sir! At the time I was only flirting with the sea - my first love - and cardinal were only the points of the compass rose! 



 	  Quote: 	
		   I understand SS twisted the elevator to allow one side

 to be at the top of the boundry layer while the other

 side is at the bottom. 


	


Well, my Denney's model 3 has already that, Kurt. Maybe SkyStar increased it.



 	  Quote: 	
		   A good curved profile will do better than a sudden

 change in a flat plate.


	


Yes, and that's where simulation is doing a poor job because if standard NACA airfoils can be tested in a wind tunnel and the data transfered to a digital model, such oddity as an angled flat plate, cannot.

Likewise, an open or sealed gap is not modelable in a simulator. Unless one uses CFD (Computerized Fluid Dynamics) which would exclude real-time simulation since it is so complex and time consuming.



Then there is one last factor; a computer model is "clean." Reality never is. Do you remember that Mathias made a model for my "Avid" wing? It flew very well in the simulator. Too well! That's because our wings are never as perfect as a model. And how could they be with fabric on ribs?



Cheers,

Michel

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

dan(at)azshowersolutions.
Guest

Posted: Tue Sep 19, 2006 5:01 am Post subject: Airfoils on empanage

Thanks for the info Kurt :>)

  Dan



kurt schrader <smokey_bear_40220(at)yahoo.com> wrote:

  [quote]--> Kitfox-List message posted by: kurt schrader 



Hey Dan,



ACS has some great yellow foam something like SS used

for gap seals, but a little lighter. I think I used

2" thick and doubled where needed. A 4' x 4' piece.



I just shaped the foam in as a full leading edge piece

to the widest part, with 3 ribs - top, bottom and

middle - back from there. The top and bottom plywood

ribs were the sanding forms to shape to. Looks almost

solid. A big hotwire would have been easier....



You can epoxy some very light fiberglass over the

foam, but I just covered with fabric and left it that

way. It will probably destroy the foam when I need to

recover later though. The  polybrush probably

penetrated the surface of the foam for a bit and I

expect it will rip out with the fabric in another 25

years. Always hangared. 



Not a hard job to redo the foam though. Next time I

will use the epoxy and light glass over it. The model

hobby shops have the best light weight glass I found.



I weighed the parts, but forgot by now how much it

added. I seem to remember 6 oz max without the

fiberglass. You can hollow out the foam, careful to

leave a web, and offset the weight of the glass a

little. My tail still came in light and I am nose

heavy, so it wouldn't have been a problem to glass it.



If you haven't covered the H stab, now is the time to

put in a good gap seal. Just add a piece of foam to

the rear of the stab, front of the elevator, or both,

your choice, and leave enough room for the fabric. 

Shape to allow full control movement and glass on.



I didn't do it and now have to use [quote][b]

kerrjohna(at)comcast.net
Guest

Posted: Tue Sep 19, 2006 10:11 am Post subject: Airfoils on empanage

I was in the aviation section of Walmart earlier this week and again saw the rolls of gap sealing tape (clear contact paper). One roll will do 10 Kitfoxes for under a $1 per plane.  It is what I used 10 years ago and it is still in place.

  

 John Kerr

  

 [quote]-------------- Original message -------------- 

From: kurt schrader <smokey_bear_40220(at)yahoo.com> 



[quote] --> Kitfox-List message posted by: kurt schrader 

 

 Hey Dan, 

 

 ACS has some great yellow foam something like SS used 

 for gap seals, but a little lighter. I think I used 

 2" thick and doubled where needed. A 4' x 4' piece. 

 

 I just shaped the foam in as a full leading edge piece 

 to the widest part, with 3 ribs - top, bottom and 

 middle - back from there. The top and bottom plywood 

 ribs were the sanding forms to shape to. Looks almost 

 solid. A big hotwire would have been easier.... 

 

 You can epoxy some very light fiberglass over the 

 foam, but I just covered with fabric and left it that 

 way. It will probably dest  roy th e foam when I need to 

 recover later though. The polybrush probably 

 penetrated the surface of the foam for a bit and I 

 expect it will rip out with the fabric in another 25 

 years. Always hangared.  

 

 Not a hard job to redo the foam though. Next time I 

 will use the epoxy and light glass over it. The model 

 hobby shops have the best light weight glass I found. 

 

 I weighed the parts, but forgot by now how much it 

 added. I seem to remember 6 oz max without the 

 fiberglass. You can hollow out the foam, careful to 

 leave a web, and offset the weight of the glass a 

 little. My tail still came in light and I am nose 

 heavy, so it wouldn't have been a problem to glass it. 

 

 If you haven't covered the H stab, now is the time to 

 put in a good gap seal. Just add a piece of foam to 

 the rear of the stab, front of the elevator, or b  oth, <  h &amp  >   [quote][b]

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