Airfoil tail

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Airfoil tail

Postby danerazz » Wed Oct 31, 2012 10:14 pm

Any thoughts on airfoil ribs on the tail?

Yes, I am just digging for little things to do.
Dane

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Re: Airfoil tail

Postby rmullins » Thu Nov 01, 2012 8:02 am

It's less draggy (faster) Thought about doing it myself...
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Re: Airfoil tail

Postby danerazz » Thu Nov 01, 2012 10:57 am

Kinda playing with the idea of making some symmetrical plywood ribs, just to add a little shape. Nothing crazy, just a little bit.
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Re: Airfoil tail

Postby Johnny C! » Thu Nov 01, 2012 12:51 pm

I am sure you guys understand this,
but I want to mention it for the record.

A significant change to the control
surfaces like that will make you
a test pilot.

Please be careful.

John
There are many things that happen really fast when you are
flying an airplane. There is no sense in rushing any of the others.

I would much rather be looking down at the runway, than up at it.

Duane Sorenson & Rick Norton Gone West 6/8/09. Godspeed
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Re: Airfoil tail

Postby danerazz » Thu Nov 01, 2012 1:53 pm

Oh, I get it. It can be well mitigated by keeping things symmetrical.
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Re: Airfoil tail

Postby Dave Krall CFII SEL SES » Thu Nov 01, 2012 2:37 pm

danerazz wrote:Oh, I get it. It can be well mitigated by keeping things symmetrical.


Why symetrical, just for less drag and more speed?

If I did mine it would be with much more airfoil on the lower surface to give more nose up lift, combating forward CG.
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Re: Airfoil tail

Postby danerazz » Thu Nov 01, 2012 4:31 pm

Dave Krall CFII SEL SES wrote:
danerazz wrote:Oh, I get it. It can be well mitigated by keeping things symmetrical.


Why symetrical, just for less drag and more speed?

If I did mine it would be with much more airfoil on the lower surface to give more nose up lift, combating forward CG.


Partly for ease of construction, and partly to avoid any nasty surprises during testing.
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Re: Airfoil tail

Postby Dave Krall CFII SEL SES » Sun Jan 06, 2013 7:47 pm

danerazz wrote:
Dave Krall CFII SEL SES wrote:
danerazz wrote:Oh, I get it. It can be well mitigated by keeping things symmetrical.


Why symetrical, just for less drag and more speed?

If I did mine it would be with much more airfoil on the lower surface to give more nose up lift, combating forward CG.


Partly for ease of construction, and partly to avoid any nasty surprises during testing.


Whichever airfoil shape was chosen, for an elevator already covered, I think ribs similar to our false ribs could each be inserted through a slit in the aft edge of the fabric, with adhesive already applied along the edges, then rotated 90 degrees and adjusted through a similar forward slit for final drying and tape slits closed.

Even an aggressive asymetrical elevator airfoil to help raise the nose is nothing that can't be overcome with aggressive control stick forces, in the unlikely event it is required.
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Re: Airfoil tail

Postby BDA » Tue Dec 13, 2016 2:18 pm

If I dig up this old thread - can anyone respond with results from their experience in trying this???

Airfoil selection?
Thickness??
Just stabilizer - or Elevator too?
Pitch change?
Change to Horizontal Stab angle?
Speed or drag change?


And Vertical and Rudder airfoil changes??

I am building and want to try this after flying the Factory plane with the "Flying Tail", will have to have this figured out soon for my project.

I used "Airfoil Tools .com" to Plot NACA 0012 symmetrical ribs in the correct lengths for the HS only. Then cut out MDF forms in those sizes and hammered out aluminum ribs using those forms.

I will attempt to post pictures of these on the HS next week.

Undecided on whether to add thickness to the leading edge of the elevator to get it out of the "disturbed boundry layer"

Undecided on whether to add airfoil section to Vertical and /or the rudder
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Mods in progress: Wing extensions, Airfoil tail ribs
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Re: Airfoil tail

Postby AV8R Paul » Tue Dec 13, 2016 7:24 pm

What made you decide on the NACA0012 airfoil. I have been contemplating building a Super STOL, I currently have a Kitfox but I like the SuperSTOL, it has both the Horizontal stabilizer & rudder, and also the Vertical Stabilizer & Rudder, and to me it just looks like it's finished. I have flow Kitfox's with both strait tails and with airfoils, the airfoil does make it more responsive control authority. I would prefer the horizontal stabilizer & rudder, and also the vertical stabilizer & rudder. I think it looks better and I am positive it will give both a lot more control authority. I'll be watching your posts. I personally would make them out of AC Grade Birch Plywood, a lot easier to build, and the weight wouldn't be that significantly different.

BDA wrote:If I dig up this old thread - can anyone respond with results from their experience in trying this???

Airfoil selection?
Thickness??
Just stabilizer - or Elevator too?
Pitch change?
Change to Horizontal Stab angle?
Speed or drag change?


And Vertical and Rudder airfoil changes??

I am building and want to try this after flying the Factory plane with the "Flying Tail", will have to have this figured out soon for my project.

I used "Airfoil Tools .com" to Plot NACA 0012 symmetrical ribs in the correct lengths for the HS only. Then cut out MDF forms in those sizes and hammered out aluminum ribs using those forms.

I will attempt to post pictures of these on the HS next week.

Undecided on whether to add thickness to the leading edge of the elevator to get it out of the "disturbed boundry layer"

Undecided on whether to add airfoil section to Vertical and /or the rudder
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Re: Airfoil tail

Postby BDA » Wed Dec 14, 2016 1:56 am

Hi Paul,
thankyou for the Info on the kitfox

The airfoil tools program has a comparison page to compare lift and drag between anything in their library, I chose the 0012 for its relatively high lift over drag ratio for a symetrical a.f.
It is also fairly common in comercial aircraft.

From what I have read 008 is more for faster aircraft

0010 middle of the road and slower aircraft

0012 for good slow speed performance
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Re: Airfoil tail

Postby moving2time » Wed Dec 14, 2016 12:15 pm

This is something that I have always been interested in doing to my Highlander when I build it. To get the most out of the modification I believe you would also need to modify the hinge design to get the proper seal with the airfoil shape all the way through the trailing edge of the control surfaces. This would require grinding off the existing hinges and welding on newly designed hinges extended out to incorporate the forward leading edge of the control surfaces. This is clearly a "during construction" type of project unless you want to tear apart your flying tail surfaces including recovering the fuselage to incorporate the vertical stabilizer modifications. The advantages must not be to terribly noticeable or I would think the factory would have incorporated them to begin with unless it was just a simplicity choice over performance. The laws of aerodynamics would say the airfoil is superior but will the performance changes be noticeable to the average pilot. The biggest benefit may be the increase in speed yet still maintain the same stall speed. I believe that flying tail surfaces would be a great addition to the Highlander or Super STOL. Actually, I thought I heard Troy mention that he was looking at offering flying tail surfaces. Anyone else heard any rumblings about this? Joe b
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Re: Airfoil tail

Postby BDA » Wed Dec 14, 2016 7:25 pm

They have said (on youtube) they will be building and selling airfoil tail, the XL at the factory has airfoil in the Horizontal surface only and is a real improvement from what I can tell between the several SS that I have flown.

I am sure that building the horizontal and elevator with one continuous airfoil would be the largest improvement - but - just doing the Horizontal seems to have made a big enough difference to me.

Not sure why their plans to make these have stalled - Troy won't even talk about them with me, little disappointed with that.
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Re: Airfoil tail

Postby BDA » Sat Dec 17, 2016 5:41 pm

Anyone else done this and have results to share??

Videos of a flat tail taxiing with the tail up vs airfoil taxiing with tail up??

Has anyone played with making the leading edge of the elevator slightly thicker that the edge of the stabilizer to accelerate the turbulent layer again?
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Mods in progress: Wing extensions, Airfoil tail ribs
Goal: 15mph no wind
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Re: Airfoil tail

Postby av8rps » Sun Dec 18, 2016 12:24 am

When Kitfox introduced their Model 4 Speedster in the early 90's they added airfoiled tailfeathers claiming it provided more speed and better handling. Sounded good to me, but after flying Avid Flyers for 20 years without airfoiled tailfeathers, I really couldn't imagine what all the hype was about. It looked to me like they were just adding a lot of build time, and weight.

I own a Kitfox 4 these days and it has the small Speedster ribs in only the horizontal stab and elevator, utilizing the standard hinges (like the Highlander has). I have no ribs in the vertical fin or rudder. So how does it fly? It flies very nice, but honestly I can't tell the difference between ones with ribs and one without. (Oh, and my Highlander sock as it is handles similarly well ). In summary, I do think it helps. But I don't believe it is all that significant on our 100 mph airplanes.

I think there is much better streamlining a person could do that would give better payback in the speed area on our Just aircraft. Like doing something about the cables holding the tail together. Cable is horrible for speed. Landing gear cleanup would be next. Cover it and streamline leading and trailing edges. Make airfoiled covers over gear bungees. And wing struts... according to books I've read a 1 inch thick tube needs a fairing 4.25 inches in chord to properly reduce the drag of that tube. My Kitfox has that much wider chord wingstrut fairing, and from all I can tell it works. The Kitfox crowd will tell you if you don't streamline wing struts it will cost you 10 to 12 mph. Ok, so what's wrong with our struts on our Just aircraft? Simple, while streamlined tubing material is used, the chord is not wide enough. If I recall correctly it's about 2.3 inches wide. It would be better at 4.3 inches imho. I am convinced if a person addressed those areas on our airplanes it would help. But the reality is on the Highlander, that undercambered wing hits a wall much over 100 mph. So there's only so much that can be done unless you change the wing airfoil.

And on the Super STOL you not only have a thick, draggy wing to contend with, but also a huge draggy landing gear dangling under the aircraft. The drag factor on that gear alone probably negates most other drag reducing efforts.

BUT...with all that said, our aircraft are just such great little bush planes just the way they are. So do we really want to compromise any of that? Our aircraft are pretty durable and effective as they are, but start adding fairings all over the place and you're probably going to lose some of that backcountry ruggedness we so enjoy now.
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