Thanks for this video! I, as others have wondered the same things. But I have a slight modification to your approach. First, decide at what angle of attack you are unhappy with the wing performance. For example at the stall angle of attack or maybe just past peak lift. Then find the spot on the top of the wing which is horizontal. That is the point where the air is still attached, but the point at which the air will start detaching further down the cord. Put your vortex generators there at that spot. It’s the spot of highest velocity, and the vortex generators will miss that high velocity into the stalling air past that point to keep it attached. This is then why there is not magic percent cord for VG placement. Each wing type will have a different optimum place to mount the VGs which will be close to the position as outlined above. It would be nice to see how this lines up with your findings. ;-)
Interesting work, very good video presentation. I, along with many others, await the results of the actual flight testing. When working with the mysterious and sometimes surprising characteristics of boundary layer aerodynamics, I rely on real life results more than theories or simulations. The best method to demonstrate the actual airflow over the wing is with tufting recorded by video. In the Stolspeed website I don't claim a dramatic reduction in stall speed. 3-5kts in most cases. The main benefit of VGs is improved control response at slow speed and softening the stall to a progressive 'mush', allowing safer flight right down to stall speed without the danger of being dropped on suddenly. I tested the Stolspeed VGs at positions from 12% to as far forward as the airfoil allowed. 12% was too far back, 10% was marginal, and anywhere forward of 10% gave the same results. I couldn't find any such 'sweet spot' that some claim. So I settled on 7%, and that has been successful on most aircraft. Some customers have insisted on placing the VGs at 10% because that is what they have heard and read elsewhere, sometimes with disappointing results.... The Kitfox wing is an interesting situation because some previous experience has indicated that farther forward than usual may be more effective..... On the main wing I found no advantage of spacing the VGs any closer than 90mm. The 60mm spacing on the outer portions of the wings was to assist better aileron control and help prevent tip stall on any aircraft so prone. The 7% of chord that I recommend for the placement of Stolspeed VGs is suitable for the practical limit of AofA for most aircraft being 15-16 degrees. Flying beyond that limit means dragging the aircraft with power behind the power curve, and is considerably challenging and somewhat risky for most pilots. Quite a few busted landing gears due to that technique.... I do a lot of STOL landings off-field in outback Australia and don't ever fly behind the power curve.... I find that a glide approach at 1.3Vs right to ground level then an abrupt round-out and hold off, until with stick all the way back and maybe feed in a little bit of power for the highest AofA in flare, to a slow and gentle touchdown. I find this method to be the safest and most dependable, and STOL enough for any practical need. In really remote areas I can't take the risk of flying behind the power curve.... It will be interesting to see how your actual results at 25 degrees matches the simulation. That is very much behind the power curve, and brings in some real challenges. Be aware that if/when the airflow does break away at that AofA, the result will be a very abrupt and dramatic drop, and no way to immediately recover..... If it happens better be right close to the ground..... It'll be interesting to see if you can actually pull a 25 degree AofA with those flaperons at 40 degrees inducing a major forward pitching moment..... I have concerns about flying any of those STOL ops with flaperons at 40 degrees. The simulation shows the flaperon completely stalled, as you would expect at that AofA to the airflow under the wing. I know of several flaperon-equipped aircraft that have come to grief with flaperons at 30 degrees at take-off. The aircraft jumps off the ground at slow speed, then the torque from 100hp starts a roll to the left, the pilot reacts with right stick which puts the left flaperon at even greater AofA causing it to stall, losing lift and increasing drag on that side, pulling that wing back and down and ending in a messy cartwheel..... Once again, I await a thorough video report of the real life flight testing.
Thanks, JG, for posting your thoughts on VG placement. I'd thought about placing VGs on my GlaStar at 3% of chord, but after reading your recommendations, I'll test at 7% and see what the wool tufts show before committing.
🔔Placement? Back in 69 when I was on 737s, we did a mod that reduced the number of VGs ahead of the ailerons and also increased their angle. I THINK they were shorter too. Boeing said they were as effective yet increased cruise speed 4 kts. $$$$$ (450 kt airplane @ 30,000 ft). All I remember is knocking them off and gluing new ones on. :-)) This was the same time we were rotating/angling the thrust reverser positions from horizontal pivots to 10/4 oclock ( 2/8) because of exhaust "lift" under the wings. Bare in mind the 737s were a new design only a couple years flying.. You are a "good head" Alex and I appreciate your analytical/ pragmatic thinking.🔔👍 viva la landing gear!
Very nice graphics. Was a little confused at first with regard to AOA numbers. I'm used to hearing pitch degrees, but it made sense after all. Thanks !
Wouach.... Thanks ! Good video & explanations. The only thing I have to do is only ...to replace all of them at 3% instead of the actual 7-8% ! I started at 10%, recommended by the VG's producer. Forget it, no effect at all in the stall speed full flaps, not a single knot. I have an Eurofox...
Good explanation and modeling. Nothing on an airplane is without compromise somewhere, however. Leading edge VGs also increase drag throughout the speed spectrum...typically more the further forward you install them. You might want to do a follow up vid and touch on the effects on cruise speed and efficiency.
Makes total sense on more anterior placement as the angle of attack increases the further back the old school of placement @ 7% cord length is no longer in contact with laminar (fast moving) air. I believe the camber on a Just Highlander is greater than the Kitfox yet the top of the wing is similar so intuitively my hope is the calculation would be valid for that aircraft as well... Anyway, Bravo on a great study!
Alex Great video. On April 12 I installed Pacific NW Aero LLc VGs on my Kitfox STi wing at 5%. The cord is approx. one and three eights thicker at the center than the standard Kitfox wing and Approx. three inches wider front to aft. I had talked to everyone I could about the placement and everyone had different opinions as to where they go. Jerry at Pacific had the kit at 10% , John from Kitfox told me to experiment with the double sided tape but that others had good results at 4%. Jerry also told me after years of VGs placement on other aircraft you would want a wider spacing closer to the fuselage. Jerry also had a guy from Africa with a standard Kitfox wing with good results at 3%, he is still experimenting. Just thought I would share. Keep the videos coming there great. I'll let you know the results of airspeeds on my first flight this spring. Tom
Yes, no one knows until it is tested. I chose to simulate because I didn't want to install VG's 3 or 4 times to see which location is best. Looking forward to see what you found out.
Such a great and informative video. I don't own a plane at this time, but was curious exactly why people install VG's and their purpose. Thank you for explaing it to me.
Wish you would have made this video about a year ago. Went with best guest-a-mate on my Avid Magnum placed them @ 6% with little result. Time to redo. Thank you for info, nice meaning you @ Tony’s a wile back. Keep up the vlog, great info.
Great video. I like the way you did your analysis to separate myth from fact. It would be also be good to show the theoretical lift coefficients you were coming up with under the different AOA and VG configurations. It is one thing to see separation but I also want to see what the actual lift will be.
I run mine staggered (basically double row that doesn't overlap kind as you showed towards the end), and my 116 sq ft speed wing (RANS) stalls lower than any other speed wings I've heard numbers on. Wasn't what I intended to do originally (long story), but I tried it, and it seemed to work, kept adding them, kept flying slower down to a point. I can touch down sometimes below 40 mph ias, and stalls around 35 in the air. Usual landing speed around 40-42mph which is good for such a tiny wing and a heavy plane. I love VGs! Will be interesting to see what effect you bird has with them (assuming you are installing them?) I think it will bring your stall down at least 3-5mph at high aoa. Maybe more!?
@@AlexDiSessa Pretty sure GKF's VG configuration looked more like a second row of VGs a significant percentage back on the wing for a secondary energizing force -- is this correct? That would be fun to simulate.
Jerry Barr who is from Burlington, WA, at KBVS, did the testing for Micro Vortex Generators in Anacortes, WA. This testing was extensive on his Super Cub and placement was done for a high angle of attack for STOL competition and also routine or standard flying parameters. He took his flight tests for the STOL and went to the Valdez STOL competition and won it. His were placed at s low percentage of chord, like 5% for the backside of the power curve, and at specific spacing and angles which we see from Micro. For routine flying, they are placed at like 10-12% for just slow speed flying near stall airspeeds. What I was seeing in some of your examples is that they were all spaced at the equal distances apart, and that may be the reason KITFOX said they didn’t work that well. It also depends on the airfoil shape/chord, as well. There are also some placements which very the distance from the leading edge, like closer to 5-6% on the inboard wing flap area, and farther back like 8-10% for the aileron section of the wing. Jerry told me he did like 25-30 test flights for each placement test. If you would like to talk to him, leave a comment. here, and I will his permission to call you. The flow parameters you did looked really great. What fluid dynamics modeling app did you use? Thank you for a great presentation! 🛫😎
Alex Di Sessa It might be interesting to include the flaperon as part of the total cord length of the wing and see if there is any difference. I will get Jerry Barr’s number for you and also have him watch this video. 😎
I’m really enjoying the content your putting out there, especially the landing gear dampening system you came up with, I can’t imagine how much time you put into that, I think you have a million dollar concept there! Please keep the good stuff coming & be safe out there. Gary…
Hey Alex, I have always enjoyed your videos, and the last 2 are exceptional. the content is interesting and very well presented. great to see all the simulations, a great new direction for your channel !
Cool vid, I like the approach, btw, you know that there is a way to figure this out, right? Basically you run the model wing in a “wind tunnel” and setting a given airspeed, then you see where the separation occurred at a given (alpha) usually with a vizflow fluid. You then place the VG, 5% before the separation occurs. The problem is leveraging a RIIBBLET airfoil, there is no reliable wind tunnel data for them. The problem with them is that there is some hysteresis happening at those AOA and airspeeds. How I would test it, place a camera looking at 30% of the wing span (measured from the root) please your VGs and spray vizflow on the area, go do some stalls with and without and report back with those videos...
That's an incorrect statement. Putting a model on wind tunnel won't be very accurate because everything needs to be scaled down and the quality won't be the same. Besides, making an accurate tunnel where the flow is proper and you can visualize with smoke is not an easy task. I looked into this.
Alex Di Sessa Hey Alex, I enjoy your videos, but please have a look at this www.nrel.gov/docs/legosti/old/3799.pdf even with current validation, Wind Tunnel data is great for approximation, and the biggest difference might come form the stall characteristics as of a full wing (3D) does behave different than a airfoil section (2D) but the separation limits of the airfoils are very close considering the right RN number, so for this particular purpose, this is very good data if available. So my point was been a Ribblet airfoil, there are no good (as in NASA created) wind tunnel data for them, so you are going blind at it. If there where good wind tunnel data, you could find the separation (approximation) of the airfoil, average these out, and move roughly 5% from the average point toward the LE to get you in exited airflow to prover the H-Vortex that the VG’s need to be successful. Then you could consider if these H-Vortex work ben in the laminar flow or above it... and so on and so on. :) Also note that I recommend a 3D model (full scale for your testing and evaluation) as even on the airframe, there are difference as you move outwards from the prop disturbances... get some vizflow pain to test it out or make your own and evaluate from from video of doing stalls, that would be a great follow up to this vid. 🤩👍 On a side note, biggest problem I see with VG’s (and I have tons of literature to share) is that the values of improvements are roughly in the range of 3% to 8% overall. So considering this, these values fall well inside the noise of the data acquisition instruments and the density/temperature gradient you experience in the atmosphere, so, some swear by them, other not so much. There as documented cases of above 10%, but I suspect most of this comes from the improvements of the hysteresis that occur in certain airfoil & airframe configurations and the disturbances of the prop. If this is accounted, some place VG’s in the 30-40% range of the wing starting at the root. Well, to be very precise on the data, you would need to test your CFD (which is an approximation) with data from the field, but that you’ll mean placing probes an little holes on your beautiful airplane. :) Keep the videos coming, well executed and do serve their purpose.
By preventing the friction caused by the effect of the movement, a gap can be provided between the surface and the air with the coating made by using composite materials, thanks to the frequency that varies according to the measured parameters. However, if the spiral rotation effect can be achieved, as the speed of the flying vehicle increases, the increase in the number of particles per unit square will increase the pressure on the surface, so it can gain continuous acceleration. If we consider it as the minimum friction in the vacuum of space. Physically, the greater the density of matter in an area, the greater the friction. The interactions of atoms with each other at certain speeds are variable. I know it's a little confusing. You can exemplify this as how a drill bit drills through solids.
@@AlexDiSessa It's obvious it wouldn't. You need the vortices start at or just before the topmost part of the curve at the desired alpha. Flaperons are situated way down below. That's why LERXes precede jet fighter wings, not trail behind them.
Alex first u should insert VGs to just upside of the transition zone on airfoil. And dont forget transition point moves upward(leading edge side) when AoA increases. And never use VG's under %10 of chord length. It will cause increase drag and reduce lift.
Nice! You should get in touch with Mike Patey (Draco Builder) he is doing a new project and your Vortex Generator Informations might come in handy ... and you might get some props :-)
At the spacing you suggested, watch out for a vicious stall. (60mm for outer third 90mm for mid length and120mm on the inner third, rule of thumb approximately) also they will increase low speed control,not don't know the effects on the kf setup, looking at your simulation vg's on the flaperon might be a idea worth looking at.
Just learning about these. I have a question on how these would effect say a car with the airfoil upside down from a plane ( sprint car) 5ft x 5ft wing. Would these help improve downforce and effectiveness as well as aid in drag reduction since the air flow would technically be hitting the rollcage/driver at 20 to 30 degrees of attack
I'd love to see wind tunnel video with these installed. Those data animations looked a little too good to be true in my opinion. I've no doubt vortex generators work, but that well? hmmm
Hi Alessio, grazie, great video. I had no idea that the little wedges would do that. Any idea at 0.85 Mach what would happen? I am in Geneva, Svizzera. Dove sei, tu ?
Awesome video. As you are simulating have you thought about using biomimicry like hump back whale tubercles to see what results you might get??? (just for fun)!!!
Nice one Alex - looks like a fun CFD session you had there! What airfoil did you use for the CFD model out of interest? - the later KF models use a proprietary airfoil, right? Lastly: In the 25°AoA examples, do you think the flow separation over the top of the flaperon profile is accurately illustrating the cause for the reduced roll authority tendency that flaperons are generally known for, when in the flap-extended position? Hey - aeronautical engineering is every bit as interesting as the flying - keep up the great work!
We scanned my Kitfox wing for the model. I think it was very accurate representation. Although we don't know how much loss of control flaperons have, if there's a loss, it is compensated by its length.
Excellent video bud. I bought the Stolspeed VG.s and Ive been looking for a video like yours that actually explains the VG positioning with some backed up engineering data. I have a piper Tripacer. Different wing but I'm sure will have similar results to your kitfox. Well done. BTW was that 3 degrees to the highest point of your VG or to the beginning of the VG ?
Very interesting indeed, I did a similar test on the Husky and found a very strange orientation of VGs that worked best on the wing but a more conventional arrangement on the empennage. What software did you use for the flow simulation?
If they don't work on a Kitfox wong, then what's up with the Kitfox STi wing? What are the advantages of the four large vg fins on that wing? Also why are the OEM Wilga wing tips shaped as they are on Draco?
The engineering aspect of this was fascinating. Thank you for your use of the scientific method.
This is one of the coolest aviation related videos I've seen in a LONG time.
Thanks, appreciate. Share it!!!
Very interesting. Next is a test of a real airplane without VGs, then attach the VGs and test again.
Thanks for sharing your research! Looking forward to your next video.
Thanks for watching.... your last video though,, man was good.
I am a newbie Kitfox pilot and your giving me lots of ideas for future upgrades. Thanks for doing the engineering analysis and design.
Thanks for this video! I, as others have wondered the same things. But I have a slight modification to your approach. First, decide at what angle of attack you are unhappy with the wing performance. For example at the stall angle of attack or maybe just past peak lift. Then find the spot on the top of the wing which is horizontal. That is the point where the air is still attached, but the point at which the air will start detaching further down the cord. Put your vortex generators there at that spot. It’s the spot of highest velocity, and the vortex generators will miss that high velocity into the stalling air past that point to keep it attached. This is then why there is not magic percent cord for VG placement. Each wing type will have a different optimum place to mount the VGs which will be close to the position as outlined above. It would be nice to see how this lines up with your findings. ;-)
Interesting work, very good video presentation.
I, along with many others, await the results of the actual flight testing. When working with the mysterious and sometimes surprising characteristics of boundary layer aerodynamics, I rely on real life results more than theories or simulations. The best method to demonstrate the actual airflow over the wing is with tufting recorded by video.
In the Stolspeed website I don't claim a dramatic reduction in stall speed. 3-5kts in most cases. The main benefit of VGs is improved control response at slow speed and softening the stall to a progressive 'mush', allowing safer flight right down to stall speed without the danger of being dropped on suddenly.
I tested the Stolspeed VGs at positions from 12% to as far forward as the airfoil allowed. 12% was too far back, 10% was marginal, and anywhere forward of 10% gave the same results. I couldn't find any such 'sweet spot' that some claim. So I settled on 7%, and that has been successful on most aircraft. Some customers have insisted on placing the VGs at 10% because that is what they have heard and read elsewhere, sometimes with disappointing results.... The Kitfox wing is an interesting situation because some previous experience has indicated that farther forward than usual may be more effective..... On the main wing I found no advantage of spacing the VGs any closer than 90mm. The 60mm spacing on the outer portions of the wings was to assist better aileron control and help prevent tip stall on any aircraft so prone.
The 7% of chord that I recommend for the placement of Stolspeed VGs is suitable for the practical limit of AofA for most aircraft being 15-16 degrees. Flying beyond that limit means dragging the aircraft with power behind the power curve, and is considerably challenging and somewhat risky for most pilots. Quite a few busted landing gears due to that technique.... I do a lot of STOL landings off-field in outback Australia and don't ever fly behind the power curve.... I find that a glide approach at 1.3Vs right to ground level then an abrupt round-out and hold off, until with stick all the way back and maybe feed in a little bit of power for the highest AofA in flare, to a slow and gentle touchdown. I find this method to be the safest and most dependable, and STOL enough for any practical need. In really remote areas I can't take the risk of flying behind the power curve....
It will be interesting to see how your actual results at 25 degrees matches the simulation. That is very much behind the power curve, and brings in some real challenges. Be aware that if/when the airflow does break away at that AofA, the result will be a very abrupt and dramatic drop, and no way to immediately recover..... If it happens better be right close to the ground..... It'll be interesting to see if you can actually pull a 25 degree AofA with those flaperons at 40 degrees inducing a major forward pitching moment.....
I have concerns about flying any of those STOL ops with flaperons at 40 degrees. The simulation shows the flaperon completely stalled, as you would expect at that AofA to the airflow under the wing. I know of several flaperon-equipped aircraft that have come to grief with flaperons at 30 degrees at take-off. The aircraft jumps off the ground at slow speed, then the torque from 100hp starts a roll to the left, the pilot reacts with right stick which puts the left flaperon at even greater AofA causing it to stall, losing lift and increasing drag on that side, pulling that wing back and down and ending in a messy cartwheel.....
Once again, I await a thorough video report of the real life flight testing.
Thanks for the reply. Very thoughtful.
Thanks, JG, for posting your thoughts on VG placement. I'd thought about placing VGs on my GlaStar at 3% of chord, but after reading your recommendations, I'll test at 7% and see what the wool tufts show before committing.
🔔Placement?
Back in 69 when I was on 737s, we did a mod that reduced the number of VGs ahead of the ailerons and also increased their angle.
I THINK they were shorter too.
Boeing said they were as effective yet increased cruise speed 4 kts. $$$$$ (450 kt airplane @ 30,000 ft).
All I remember is knocking them off and gluing new ones on. :-))
This was the same time we were rotating/angling the thrust reverser positions from horizontal pivots to 10/4 oclock ( 2/8) because of exhaust "lift" under the wings.
Bare in mind the 737s were a new design only a couple years flying..
You are a "good head" Alex and I appreciate your analytical/ pragmatic thinking.🔔👍
viva la landing gear!
One year later I came across this video. Thank you for the research and time and effort you put into this study. On to the test video!
Glad it was helpful!
Excellent presentation. Clear progression of the issues, great graphics. 👍
I love that you are using engineering data to help solve the VG questions. Great video
As a retired Bell Helicopter Director of Research Programs I love your innovative, engineering mind!
Chuck
Thanks Chuck!
Thanks Alex, cool simulator graphics. Thank you for sharing all of your findings. Very helpful.
Excited to see the real world benefit in the next video. i think it will be quite interesting and good to see real world numbers. Great information!
Very well done! Love the animations! Finally understand
Very nice graphics. Was a little confused at first with regard to AOA numbers. I'm used to hearing pitch degrees, but it made sense after all. Thanks !
Wouach.... Thanks ! Good video & explanations. The only thing I have to do is only ...to replace all of them at 3% instead of the actual 7-8% ! I started at 10%, recommended by the VG's producer. Forget it, no effect at all in the stall speed full flaps, not a single knot. I have an Eurofox...
Great explanation! It helped my understanding of VG’s much better at different location. Thank you!
Great Video, thanks for doing the real world studies and sharing them.
Good explanation and modeling. Nothing on an airplane is without compromise somewhere, however. Leading edge VGs also increase drag throughout the speed spectrum...typically more the further forward you install them. You might want to do a follow up vid and touch on the effects on cruise speed and efficiency.
Yes, working on the follow up video Part 2
Makes total sense on more anterior placement as the angle of attack increases the further back the old school of placement @ 7% cord length is no longer in contact with laminar (fast moving) air. I believe the camber on a Just Highlander is greater than the Kitfox yet the top of the wing is similar so intuitively my hope is the calculation would be valid for that aircraft as well... Anyway, Bravo on a great study!
Great Video, nicely conducted experiments.
Alex Great video. On April 12 I installed Pacific NW Aero LLc VGs on my Kitfox STi wing at 5%. The cord is approx. one and three eights thicker at the center than the standard Kitfox wing and Approx. three inches wider front to aft. I had talked to everyone I could about the placement and everyone had different opinions as to where they go. Jerry at Pacific had the kit at 10% , John from Kitfox told me to experiment with the double sided tape but that others had good results at 4%. Jerry also told me after years of VGs placement on other aircraft you would want a wider spacing closer to the fuselage. Jerry also had a guy from Africa with a standard Kitfox wing with good results at 3%, he is still experimenting. Just thought I would share. Keep the videos coming there great. I'll let you know the results of airspeeds on my first flight this spring. Tom
Yes, no one knows until it is tested. I chose to simulate because I didn't want to install VG's 3 or 4 times to see which location is best. Looking forward to see what you found out.
Excellent video ,looking forward to seeing the next video with them mounted on your wing.
Great stuff, your graphics are excellent and the content is excellent. Very nice work.
Such a great and informative video. I don't own a plane at this time, but was curious exactly why people install VG's and their purpose. Thank you for explaing it to me.
Glad it was helpful!
Well done. Outstanding graphics!
Good video, great info; I enjoy the engineering "stuff" as much as the flying... follow-up video will be interesting , thanks👍
Wish you would have made this video about a year ago. Went with best guest-a-mate on my Avid Magnum placed them @ 6% with little result. Time to redo. Thank you for info, nice meaning you @ Tony’s a wile back. Keep up the vlog, great info.
yeah, great meeting you. Your Avid is awesome!
Great video. I like the way you did your analysis to separate myth from fact. It would be also be good to show the theoretical lift coefficients you were coming up with under the different AOA and VG configurations. It is one thing to see separation but I also want to see what the actual lift will be.
I run mine staggered (basically double row that doesn't overlap kind as you showed towards the end), and my 116 sq ft speed wing (RANS) stalls lower than any other speed wings I've heard numbers on. Wasn't what I intended to do originally (long story), but I tried it, and it seemed to work, kept adding them, kept flying slower down to a point. I can touch down sometimes below 40 mph ias, and stalls around 35 in the air. Usual landing speed around 40-42mph which is good for such a tiny wing and a heavy plane. I love VGs! Will be interesting to see what effect you bird has with them (assuming you are installing them?) I think it will bring your stall down at least 3-5mph at high aoa. Maybe more!?
The staggered was not bad at all, very close to the 3% simulation.
@@AlexDiSessa Pretty sure GKF's VG configuration looked more like a second row of VGs a significant percentage back on the wing for a secondary energizing force -- is this correct? That would be fun to simulate.
excellent communication skills.
Great video Alex!!!! Love it! Cool animation.... and... interesting information. 🤔👍👍👍
Jerry Barr who is from Burlington, WA, at KBVS, did the testing for Micro Vortex Generators in Anacortes, WA. This testing was extensive on his Super Cub and placement was done for a high angle of attack for STOL competition and also routine or standard flying parameters. He took his flight tests for the STOL and went to the Valdez STOL competition and won it. His were placed at s low percentage of chord, like 5% for the backside of the power curve, and at specific spacing and angles which we see from Micro. For routine flying, they are placed at like 10-12% for just slow speed flying near stall airspeeds. What I was seeing in some of your examples is that they were all spaced at the equal distances apart, and that may be the reason KITFOX said they didn’t work that well. It also depends on the airfoil shape/chord, as well. There are also some placements which very the distance from the leading edge, like closer to 5-6% on the inboard wing flap area, and farther back like 8-10% for the aileron section of the wing. Jerry told me he did like 25-30 test flights for each placement test. If you would like to talk to him, leave a comment. here, and I will his permission to call you. The flow parameters you did looked really great. What fluid dynamics modeling app did you use? Thank you for a great presentation! 🛫😎
Thanks for the info. I like to talk to him after my real flying tests..
Alex Di Sessa It might be interesting to include the flaperon as part of the total cord length of the wing and see if there is any difference. I will get Jerry Barr’s number for you and also have him watch this video. 😎
I've been waiting for this one. Thanks Alex nicely done
Very interesting! Looking forward to the real life test video!
This is true testing and great info.
Glad you liked it
Nice! Now add leading edge slats with the VG’s present. Now that’ll really improve things at 25 degrees AOA!
I’m really enjoying the content your putting out there, especially the landing gear dampening system you came up with, I can’t imagine how much time you put into that, I think you have a million dollar concept there! Please keep the good stuff coming & be safe out there. Gary…
Very informative video thanks for posting
Which software did you use for the analysis?
Been watching You for some time, and I must say, This was Your best video ever. BRAVO.
Thanks
very good video and very well explained!!!!
Very nice info, thx u so much bro 👍
Wow you are one smart man!
Very interesting study!
Alex, you're my hero.
LOL!!
Great work! I am interested in seeing how the VGs affect the drag of the wing
Hey Alex, I have always enjoyed your videos, and the last 2 are exceptional. the content is interesting and very well presented. great to see all the simulations, a great new direction for your channel !
Thanks
Itz another "Bell Ringer" Alex.
Excellent explanation.
👍😎
Love the landing gear.
Thanks
Well Done!!, Thank you sir.
Awesome work!
Great video. Thanks !
Well done. Thanks . Could you run a simulation for the sti wing.
Good info. Keep up the good work.
Thanks 👍
Great presentation
Thank you!
Excellent!
Cool vid, I like the approach, btw, you know that there is a way to figure this out, right? Basically you run the model wing in a “wind tunnel” and setting a given airspeed, then you see where the separation occurred at a given (alpha) usually with a vizflow fluid. You then place the VG, 5% before the separation occurs. The problem is leveraging a RIIBBLET airfoil, there is no reliable wind tunnel data for them. The problem with them is that there is some hysteresis happening at those AOA and airspeeds. How I would test it, place a camera looking at 30% of the wing span (measured from the root) please your VGs and spray vizflow on the area, go do some stalls with and without and report back with those videos...
That's an incorrect statement. Putting a model on wind tunnel won't be very accurate because everything needs to be scaled down and the quality won't be the same. Besides, making an accurate tunnel where the flow is proper and you can visualize with smoke is not an easy task. I looked into this.
Alex Di Sessa Hey Alex, I enjoy your videos, but please have a look at this www.nrel.gov/docs/legosti/old/3799.pdf even with current validation, Wind Tunnel data is great for approximation, and the biggest difference might come form the stall characteristics as of a full wing (3D) does behave different than a airfoil section (2D) but the separation limits of the airfoils are very close considering the right RN number, so for this particular purpose, this is very good data if available. So my point was been a Ribblet airfoil, there are no good (as in NASA created) wind tunnel data for them, so you are going blind at it. If there where good wind tunnel data, you could find the separation (approximation) of the airfoil, average these out, and move roughly 5% from the average point toward the LE to get you in exited airflow to prover the H-Vortex that the VG’s need to be successful. Then you could consider if these H-Vortex work ben in the laminar flow or above it... and so on and so on. :) Also note that I recommend a 3D model (full scale for your testing and evaluation) as even on the airframe, there are difference as you move outwards from the prop disturbances... get some vizflow pain to test it out or make your own and evaluate from from video of doing stalls, that would be a great follow up to this vid. 🤩👍
On a side note, biggest problem I see with VG’s (and I have tons of literature to share) is that the values of improvements are roughly in the range of 3% to 8% overall. So considering this, these values fall well inside the noise of the data acquisition instruments and the density/temperature gradient you experience in the atmosphere, so, some swear by them, other not so much. There as documented cases of above 10%, but I suspect most of this comes from the improvements of the hysteresis that occur in certain airfoil & airframe configurations and the disturbances of the prop. If this is accounted, some place VG’s in the 30-40% range of the wing starting at the root. Well, to be very precise on the data, you would need to test your CFD (which is an approximation) with data from the field, but that you’ll mean placing probes an little holes on your beautiful airplane. :)
Keep the videos coming, well executed and do serve their purpose.
1:36 pls flip the smoke image
Interesting content. Thanks
Excellent and informative video Alex! One day I’d like to do a simulation with slats installed on a cub wing! Keep it up!
Thanks.
it may be beneficial to ad vg in wind turbines....any thoughts?
probably not...
Lmao, “...and paint them! Don’t be lazy! Make them look good.” 😂
😂
Love your videos man
Thanks
By preventing the friction caused by the effect of the movement, a gap can be provided between the surface and the air with the coating made by using composite materials, thanks to the frequency that varies according to the measured parameters. However, if the spiral rotation effect can be achieved, as the speed of the flying vehicle increases, the increase in the number of particles per unit square will increase the pressure on the surface, so it can gain continuous acceleration. If we consider it as the minimum friction in the vacuum of space. Physically, the greater the density of matter in an area, the greater the friction. The interactions of atoms with each other at certain speeds are variable. I know it's a little confusing. You can exemplify this as how a drill bit drills through solids.
Try putting VGs on the top of the flapperons and see if that helps!
Tried. Didn't.
@@AlexDiSessa It's obvious it wouldn't. You need the vortices start at or just before the topmost part of the curve at the desired alpha. Flaperons are situated way down below.
That's why LERXes precede jet fighter wings, not trail behind them.
Great stuff! Smart!
Superb explanation...😀
Thank you 🙂
Another great vid!
Yah got down into the weeds on this one Alex, but I enjoyed it... Thnx, and the next time you're out here in SOFLO (F45) maybe we can meetup???
Thanks. I just left!!
Alex first u should insert VGs to just upside of the transition zone on airfoil. And dont forget transition point moves upward(leading edge side) when AoA increases. And never use VG's under %10 of chord length. It will cause increase drag and reduce lift.
Maybe you could try using some removable adhesive like command strips and try several locations before attaching them permanently.
Nice!
You should get in touch with Mike Patey (Draco Builder) he is doing a new project and your Vortex Generator Informations might come in handy ... and you might get some props :-)
Mike's twin Mark just put out a video field testing vgs on his plane.
At the spacing you suggested, watch out for a vicious stall. (60mm for outer third 90mm for mid length and120mm on the inner third, rule of thumb approximately) also they will increase low speed control,not don't know the effects on the kf setup, looking at your simulation vg's on the flaperon might be a idea worth looking at.
What basis makes you suggest a vicious stall? Love to know more about it.
Show de bola !!
Just learning about these. I have a question on how these would effect say a car with the airfoil upside down from a plane ( sprint car) 5ft x 5ft wing. Would these help improve downforce and effectiveness as well as aid in drag reduction since the air flow would technically be hitting the rollcage/driver at 20 to 30 degrees of attack
Hey. Do you know the name of the wing profile that is used on the Kitfox STI?
Sorry, don't know.
So what would happen in your simulation model if you placed VG's on the wing and on the Flaperon? I'd love to see your simulation model on that?
❤️❤️❤️❤️❤️
Love the love!!!
nice, which software do you use for your cfd ?
I'd love to see wind tunnel video with these installed. Those data animations looked a little too good to be true in my opinion. I've no doubt vortex generators work, but that well? hmmm
I found it very informative here about vg,but anyway whats the software for the animation ? Thanks cheers 🍻🍻
Ottimo per la mia auto da crono scalata. Ciao
what CFD did you use for the simulations?
As I understand it. AoA is the angle between your flight path and the angle of your wing. Not the angle of the wing relative to the ground.
But very interesting video
Thanks correct. I guess the graphics had the AOA angle reference line from a horizontal plane not the relative air in motion.
It looks like flow separation over the aileron... If it matters, little VG's for them?
Does not effect. We tried.
What cfd application are you using?
Hi Alessio, grazie, great video. I had no idea that the little wedges would do that. Any idea at 0.85 Mach what would happen? I am in Geneva, Svizzera. Dove sei, tu ?
Should I call them VGs (vortex generators) or wedges ?
They are called Vortex Generators... Jets have them as well.
@@AlexDiSessa Do you have an idea of their efficiency at 11'000 m and Mach 0.8 ? I actually never saw them on cruise airliners.
Yeh to the Flying Cowboys.
Thank you for this video! Could you explain the reason why they need to be twisted? 👍
For the air to hit and create the vortex
I'm switching my answer from Backcountry flying to Aviation engineering
Thanks for the video !
Is it ANSYS you used for the CFD ? or which software was it ? thanks
Solidworks
Have you done any research on RC Planes?
Awesome video. As you are simulating have you thought about using biomimicry like hump back whale tubercles to see what results you might get??? (just for fun)!!!
VGs on the flaperons would be interesting .
No difference. We played with that.
Alex Di Sessa Cheers!
Nice one Alex - looks like a fun CFD session you had there! What airfoil did you use for the CFD model out of interest? - the later KF models use a proprietary airfoil, right? Lastly: In the 25°AoA examples, do you think the flow separation over the top of the flaperon profile is accurately illustrating the cause for the reduced roll authority tendency that flaperons are generally known for, when in the flap-extended position? Hey - aeronautical engineering is every bit as interesting as the flying - keep up the great work!
We scanned my Kitfox wing for the model. I think it was very accurate representation. Although we don't know how much loss of control flaperons have, if there's a loss, it is compensated by its length.
Excellent video bud. I bought the Stolspeed VG.s and Ive been looking for a video like yours that actually explains the VG positioning with some backed up engineering data. I have a piper Tripacer. Different wing but I'm sure will have similar results to your kitfox. Well done. BTW was that 3 degrees to the highest point of your VG or to the beginning of the VG ?
measurement was from the tip of the VG
Very interesting indeed, I did a similar test on the Husky and found a very strange orientation of VGs that worked best on the wing but a more conventional arrangement on the empennage. What software did you use for the flow simulation?
This is a great analysis; good to see some myths being busted. What CFD program were you using here?
Solidworks
@@AlexDiSessa Figures. I'll keep looking for something more... affordable!
If they don't work on a Kitfox wong, then what's up with the Kitfox STi wing? What are the advantages of the four large vg fins on that wing? Also why are the OEM Wilga wing tips shaped as they are on Draco?
I believe the STI wing is a complete new wing profile, different than speedster wing