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Thread: V.G.'s and stall fences.

  1. #21

    Join Date
    Nov 2009
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    Oregon
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    154

    Default Re: V.G.'s and stall fences.

    Did any of you ever test stall fences? Recommended locations with any notable success? Are there any that are easy to install to the surface without having planned for them during the build? Thx guys!

  2. #22
    Senior Member
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    Jan 2011
    Location
    LAWRENCE, KS
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    479

    Default Re: V.G.'s and stall fences.

    I thought a stall fense was something you only found on a Russian swept wing jet fighter. Yes?

  3. #23

    Join Date
    Oct 2011
    Location
    Canada
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    187

    Default Re: V.G.'s and stall fences.

    Stol fence I do not think would do much for the Kitfox.
    as we have full span flapperons. You would normally put them on top of wing at the outboard end of flaps to keep undusturbed air ove the ailerons eg - C 180/185
    Tha being said - you could put on at root of wing and at outer end of wing in line with flapperon to try to hold in the low pressure on top of wing

    Kitfox placement in those pics of Big John are way back -- I thought I read about 5 " ? His look like 6 to 8 " back

    this is about 10% here http://www.cfisher.com/vg.html
    which should be about 5.1 " if I recall.

    I have done thorough flight testing and still have them on my Kitfox - some have fallen off. I would like to experiment more with then to try to find the claims of some folks but I think alot of the gains are not exact.

    I will say the stall is docile to begin on a IV that I have them on and the VG just made it more docile.
    as far as shorter take off ? small gain
    you can cllimb at a a little steeper AOA
    top speed loss ?: None in this case but we only talking a 92 mph cruise now.
    Power on stalls the buffet is non exisitant so you have little or no warning of stall. But when it ready to go you gonna have a fun ride with a instant wing drop -- kick in some rudder to get it more fun

    This is where the VG are not good -- stall forewaring - buffet not there and more. in- experienced pilot could get in trouble in a hurry.

    Be safe out there.
    Last edited by Dave F; 12-27-2011 at 05:38 AM.

  4. #24

    Join Date
    Jun 2011
    Location
    West Columbia, SC
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    125

    Default Re: V.G.'s and stall fences.

    Here are some VG's offered from Aircraft Spruce. I would like to hear from anyone who used any of these products and how it worked for you. One mentioned "all you need is the glue". So what glue did you use? First 2 are sets of plastic, the third is metal.

    6. STOLSPEED VORTEX GENERATORS
    Vortex generators (VGs) are well-proven for better low-speed handling, softening the stall characteristics, and lowering the stall speed, which makes it easier to do slower, gentler landings. Stolspeed VGs are streamlined for less drag and better
    http://www.aircraftspruce.com/catalo.../stolspeed.php - 2.7kb

    05-04458 STOLSPEED VORTEX GENERATORS 80 $69.95

    05-04457 STOLSPEED VORTEX GENERATOR 120 $99.95

    7. AIR WAVE VORTEX GENERATOR
    know for some time now that vortex generators reduce stall speeds and improve the aircraft’s handling performance. vortex generators allow the wing to develop more lift and lower airspeeds. This reduces takeoff speed and improves the rate
    http://www.aircraftspruce.com/catalo...evortexgen.php - 2.5kb

    05-04662 AIRWAVE MICRO VORTEX GENERATOR $55.00

    8. VORTEX GENERATOR FOR EXPERIMENTAL AIRCRAFT
    These Vortex Generators were designed and tested in a wind tunnel as well as on various experimental aircraft. They are formed in pairs so that the shape and angles are built right in.
    http://www.aircraftspruce.com/catalo...xgenerator.php - 1.9kb

    05-01480 HALL VORTEX GEN KIT $184.50
    Dwight B. Van Zanen
    Maple Valley, WA and
    West Columbia, SC
    PP/ASEL/IA
    Avid Mk 4 Aerobat

  5. #25
    Senior Member MotReklaw's Avatar
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    Oct 2009
    Location
    Anniston, AL
    Posts
    300

    Default Re: V.G.'s and stall fences.

    DBVZ,

    I put the stolspeed VGs on a Zenith 701, both the wings and the horizontal stabilizer. I left the slats off. We probably picked up about 3-4 mph and the stall speed seemed to be about the same. But the 701 is almost stall proof anyway. The VGs came with a template to align them with each other and it took about a hour after fixing the self sticking adhesive on each VG. I think the adhesive was a 3M product that came in strips that you trimmed to fit the VGs. I forget the distance from the leading edge that the instructions said to place them, but it was all spelled out in the literature.

    Good luck,

    Added: I bought mine from the guy who makes them in Australia. He's done a lot of testing and I believe he's on the web at this address: http://www.stolspeed.com/
    Last edited by MotReklaw; 02-17-2012 at 08:32 AM. Reason: additional info.
    Tommy Walker in Alabama

  6. #26

    Join Date
    Jun 2011
    Location
    West Columbia, SC
    Posts
    125

    Default Re: V.G.'s and stall fences.

    Found them. Part 2420-SP for $289. Not much detail in the catalog, like how many and how attached. Aluminum. Thanks.
    Dwight B. Van Zanen
    Maple Valley, WA and
    West Columbia, SC
    PP/ASEL/IA
    Avid Mk 4 Aerobat

  7. #27

    Join Date
    Jun 2011
    Location
    West Columbia, SC
    Posts
    125

    Default Re: V.G.'s and stall fences.

    Comment on this plan please:

    I have the short Avid Aerobat wings. I am thinking the 120 piece STOLSPEED VG's will be more than enough for both wings and tail. The other brand is 100 for both. I suspect if I need to cut anywhere on VG's, it should be very near the fuselage where prop wash will have some effect and a partial wing stall has least leverage.

    Thanks for your advice.
    Last edited by DBVZ; 02-17-2012 at 11:58 AM.
    Dwight B. Van Zanen
    Maple Valley, WA and
    West Columbia, SC
    PP/ASEL/IA
    Avid Mk 4 Aerobat

  8. #28
    Senior Member MotReklaw's Avatar
    Join Date
    Oct 2009
    Location
    Anniston, AL
    Posts
    300

    Talking Re: V.G.'s and stall fences.

    DBVZ,

    I think the spacing for the VGs was different in the area where the prop wash was for the 701. I would assume that that would hold true for the KF.

    Funny think about the tail VGs on the 701.... One would think they went on the leading edge of the stabilizer, but no, they were placed on the elevator and in normal flight they were hidden from the slip stream by the horizontal stabilizer. They were not exposed to the slip stream until the flare while landing. That presumably gave you more elevator control at the flare....

    (But, we ain't building a 701 are we)!

    been there done that!
    Tommy Walker in Alabama

  9. #29

    Join Date
    Jun 2011
    Location
    West Columbia, SC
    Posts
    125

    Default Re: V.G.'s and stall fences.

    These guys post a diagram of the tail showing them all just ahead of the rudder and elevator, and it looks like 3" spacing. On the vertical stab it shows them all 5* off level flight. I assume the diagrams from each mfg will have similar recommended positioning.

    http://www.aircraftspruce.com/catalo...s/05-04662.jpg
    Dwight B. Van Zanen
    Maple Valley, WA and
    West Columbia, SC
    PP/ASEL/IA
    Avid Mk 4 Aerobat

  10. #30
    kitfoxnick's Avatar
    Join Date
    Jun 2008
    Location
    Northeastern, MD
    Posts
    199

    Default Re: V.G.'s and stall fences.

    The vg's that come from Kitfox come with everything you need, right down to a little tape measure. They have vinyl decal material that is a template that you apply to the wing. It makes placement really easy. As far as placement, they're installed further apart near the wing root so that the inboard will stall first and the stall will progress outboard. I installed mine at 8% of cord after talking with the owner of Pacific Northwest Aero who is the owner of the company that the Mcbeans get them from.

    Some people don't have much good to say about the vg's, but they made such a dramatic difference in slow flight. The plane is rock solid with very little mush. If you power off stall, with the stick all the way back, the airplane stalls then breaks, and instantly recovers without ever letting the stick forward. Power on the break is more abrupt with little warning. You used to be able to spin mine without much trouble, just stall it uncoordinated. With the vg's, it took three attempts before I could get it to spin. I would stall it uncoordinated and as the wing would drop a little bit it would recover. I've never flown something where you could stall it with the stick back and the ball off to the side and it wouldn't spin, or at least spiral. The plane just kinda slides off to the side, stalling and recovering. I was finally able to get it to spin by stalling it then kicking the rudder abruptly.

    I like my vg's

    Nick W.
    Nick W
    IV 1200
    912Ul
    Warp Taper Tip

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