This an awesome video. I'm Mechanical Engineer and my undegraduate theses was about airfoils. I never see before a better explanation and demonstration of Stall phenomenom and useful devices flor preventing it with a CFD Analysis and field experiment. Congratulations Tom!!!
VGs will increase your skin friction drag (as opposed to induced drag from the wingtip vortices, or planform/area/pressure drag) because they help move fast moving fluid closer to the wing surface. The flow profile RIGHT at the surface of the wing is linear or close to it (for zero pressure gradient boundary layer flow it is linear), and intersects the origin due to the no slip condition. The drag is proportional to the slope of this line (the velocity gradient at the surface) so as you increase the slope/gradient by injecting/mixing faster moving air to the near wall region with the VGs, your skin friction drag goes up. (Also you have losses from the momentum imparted to any vortices persisting in the wake, as well as increased frontal area due to the VGs... on real aircraft these are quite small but on your model the VGs are pretty huge relative the wing cord, so these effects may be competing with or even overwhelming the skin friction increase effects. BTW, your use of the term boundary layer was not quite accurate. It seems that you were confusing the boundary layer with the separation bubble. There is always a boundary layer over any solid surface (assuming continuum mechanics, not rarified flow, or infinitely close to a sharp leading edge) with attached flow. The local skin friction indicates how close you are to having a separation bubble. When the skin friction (proportional to the velocity gradient at the surface) reaches zero due to the pressure gradient, that is where separation happens, as you correctly drew in your diagrams. The region of recirculating flow associated with boundary layer separation and stall is typically called a separation bubble. Interestingly, if you try to design airfoils and fuselages to minimize total skin friction, you WANT to be as close to separated flow as possible over the largest possible area, because local skin friction is proportional to the velocity gradient where the boundary layer meets the vehicle surface. The problem here, however, is that the vehicle is so close to stall/separation that it is not practical or controllable. (i.e., you are near stall at 0 angle of attack, or some small positive angle of attack). With conventional wings, the skin friction (in the airfoil coordinate system) is minimized right before stall. The problem is that, in the coordinate system fixed to the direction of travel, the lift vector in the airfoil coordinate system starts to point backwards in the direction of travel coordinate system, as the pressure differential between the top and bottom of the wings increase. (This will also increase the induced drag.) I'm not sure exactly why the Osprey has the VGs but as you alluded to, there are two main uses for VGs, fences, and other high lift devices like slats and flaps: Delaying stall at low speeds/high AoA, and controllability at these conditions. VGs are particularly useful upstream of control surfaces, since their control authority is derived from redirecting the momentum of the air flowing over them. If the boundary layer separates, then there is no/less airflow over the control surface, and you loose control authority. The Osprey is interesting because from that photograph I see at least 3 types of passive flow control/high lift devices: VGs near the leading edge/quarter chord on the top surface, fences adjacent to the pivoting engine nacels, and fixed leading edge slats running the length of the wing. Any way, super super cool project. Keep up the great work, and good luck in school!
Good to see someone pick up on the fences on the Opsrey - I was watching the airflow at the end of the wings on Tom's model and it definitely looks as if spill from the props is stalling the wing tips; was just thinking fences would be a good mod!
Saludos de Ecuador eres un genio. No que otros solo se ponen hacer piruetas y tomar fotografías y filmar ya se creen expertos. Experto eres tú así es como deben hacer tutoriales bien explicativos. Felicitaciones Maestro
When starting RC flying in the 90's, I got told to build my wings with the wingtips pitched down slightly. That of course decreases the angle of attack at the wingtips which makes them stall after the center of the wing. The same rationale goes behind only adding flaps to the center of the wing. The center part will stall first and you start to loose altitude, but since the wingtips still have nice airflow all the way back to the ailerons, you can still control the descent. Your vortex generators seem to have the same effect! When flying full scale, I've experienced much reduced minimum speed when having vortex generators compared to without. Could it just be that the Osprey just have them there for increased low speed lift? I assume that would take some load off the engines during slow flying.
Pitching down the edges also decreases induced drag. Additionally, giving the edges (where the controlsurfaces has the most leverage) a lower stallspeed increases control near stall- speed
Many years ago when I was learning to fly the school had a Chipmunk aircraft with wool tufts on one wing so it was possible to see exactly the effects you have replicated here. Took me back a very long time...
There were was a team of student engineers who did a senior project at my school that was similar to this aircraft but yours is 100x more successful haha. Really greats visuals! I gotta learn to animate over video like that.
Tom, I want to share some of my experiences with vortex generators and vortilons. (leading edge vortex generators). I owned a Rutan VeriEze full size plane years ago. The main wing is swept back on this plane and when tufted the air flow would sweep out longitudinally and run parallel along the trailing edge of the wing. This was most noticeable at slow speed as the ailerons became very sloppy and AOA was very high on final approach making visibility very poor. Vortex generators were attached along the top of the wing forcing the airflow to run along the chord. This dramatically improved slow flight AOA (slow flight AOA changed from ~10 degrees with no vortex generators to ~
Hi Tom,If possible, could you make a short gliding film with engine turned off? Just to see the real plane performance?Would be interresting how slow you can fly now with the vortex GeneratorsThanks, Peer (Pepponski)
Vortex generators are sometimes added to increase control surface authority.. The Vtol probably has them to still have control of the ailerons/flaps while in the transition from slow forward flight to hover.. I wouldn't say they put them on to lower the stall speed necessarily but more keep the control surfaces active that little bit longer.. I could be wrong, but you can see them on commercial passenger jets also on the elevators. My uncle said there on his glider just at the ailerons and that's what there doing.. Said it keeps the airflow sticking to the ailerons for slow thermal turns..
This is great science! Fun to watch. I just thought of a thing, might the vortex generators be a bit to big, meaning tall and long? Keep it up! Great fun!
The flow profile RIGHT at the surface of the wing is linear or close to it (for zero pressure gradient boundary layer flow it is linear), and intersects the origin due to the no slip condition. The drag is proportional to the slope of this line
Great work and video is excellent ! Real world conditions are so changeable compared to wind tunnel experiments. It is amazing how well you were able to complete this sequence.
Unloading the wing in transition, using the rotors, reduces the wing stall speed. The most efficient way to fly is wing-borne, to exploit the high L/D ratio, so it makes sense to have vortex generators and keep the wing as close to stall as possible. Even past stall, the wing is much more efficient at producing lift than rotors.
Nice Work! I would recommend you to print smaller sizes of the vortex generators (you are getting large amount of drag from those big ones you printed - resulting in wingtip stall) .Try to put the new small ones all across the wing from tip to root. There shouldn't be a large gap between the wing tip and the motor, this area should be smoother.. Extend the flaps full down when you are taking off vertically, this will gain some stability and reduce wing tip stall. Good Luck!!
It would be interesting to see what happens if you reverse the prop direction at each wingtip. Not to be critical, but the right wingtip vortex is counter-clockwise ( en.wikipedia.org/wiki/Wingtip_vortices) so the right prop being clockwise is counter to the tip vortex. Again great video!
Variable pitch vortex generators that cycle straight to full angle of attack mid engine pod transition (not linear, full VG rotation over middle 30' approximately) . not sure if the weight penalty would offset the drag efficiency / controllability gain. you could have a central servo or just 3d print magic a cam wheel on the pods to a drive shaft. this could work on any wing i guess not just for your VTOL Ps i make no claims to any expertise in any field and i'm sure it's been thought of before. this is more of a question.
Came here to say this, but make them retractable as well. Just cam them to raise straight up through slits in the covering, and then to proper angle once clearing the surface, and then back down to surface to lock them in. Cam it all to motor turning from horizontal to vertical. Now I have to go purchase a stinking 3-D printer so I can do this. I suddenly have an overwhelming need to see this in action.
just one observation - The vortex generators on the Osprey are set further rearward than the one's you installed on your wing. This might make a difference in stall speed change.
Tom - a little advice, or at least your thoughts on the subject, please. one of the reasons i have paid such close attention to your vtol videos is that, where i live landing a fixed wing plane will be difficult (too many house closeby). launching i think i can handle. why not use a quad (which i would prefer) ? because i live near the gulf coast in florida, and would like to send out an fpv drone to see what is going on around a little island about 3 miles off the coast. from my house it is about 6 miles each way. so i guess to cover this long a flight i will need a fixed wing. but a landing strip is not available. would a vtol get me enough range ? what about a standard fixed wing plane with a deployable parachute ?
These are more complex designs but I have some comments on thoughts maybe you should try. 1) I'm not sure you were getting the expected outcomes you wanted due to the fact that on a slow moving model, the Reynolds numbers are simply too low and too close together compared to that of the Ospray. Empirically, I am sure that the VGs probably have more to do with horizontal forward flight than the VTOL capability. Consider your Drag vs. Lift vs. Velocity calculations. 2) Maybe you could investigate having some washout in the wing, to change the angle of attach and make the stalling characteristics at lower speeds more favorable when transitioning and at higher angles of attack. Then you wouldn't have to worry about the added drag and weight which is probably more significant than your attempt (due to #1) to maintain laminar flow over the outer portions of the wing with the VGs. Keep up the good science and I am excited to see your progress. You are an innovator!
really looks like the flow is dominated by the propwash not the forward airspeed when you're going that slow. Also something I've found with tufts is you have to use smaller tufts than you think; the air movement you get inside a separation bubble is really really low energy compared to the attached flow (which i guess is obvious cause that's why it happens). I think this is one of those things where the wing loading vs Rn is soooo different from a full sized plane, especially such a insanely high-wing-loading plane like an Osprey, that you might not want to be looking at Old floater polyhedral r/c gliders used to use these stick on strips that were used by tailors or something, little 1/8 inch paper or fabric with a 1/4-inch zig zag pattern that would trip the boundary layer to avoid a bubble forming. I'm just wondering if there's really enough energy at this scale and this wing loading to get the kind of useful vortex to form that can actually do what you want. I saw you had video from a guy doing CFM on a model of the vortex generators, but did he really have the parameters set to match the scale and speeds of your plane?
I used to work on F-18s in the US Navy, if you look at the wing from the tip, there is definite twist from tip to root, so the root stalls first, is probably why the plane is so good at high alpha flights. I can't tell if your airplane is using any auto pilot gyros or not? How much aerodynamic control are you using, ailerons etc, vs just motor thrust control? Anyway, I'm enjoying watching your process and progress, nice job on the incremental testing. Well done!
What do you think of Adding wingtips to the Motor Mounts, so the Aircraft is slowing down faster at the transition. And you shouldn't need the aileron anymore.
I know this vid is over 2 years old, but why dont you have the vortex generators pop up at the same time your motors transition, and be flush when if forward flight? That would probably solve both concerns
Great project. Great progress. Do you have a link to some more information on the KK2 Setup for that type of plane? Very much like to build one on my own.
I know this video is 4 years old but I thought I'd share my understanding anyways. For low reynolds numbers such as RC scale, especially when approaching low vtol speeds, vorticity means almost nothing. Vortex generators, P factor coefficients, wing twist, variable airfoils, all moot. Even super high aspect ratio wings begin to suffer efficiency losses. What is predominant at this scale are the effects of general pressure, and the only way you can really affect that to any efficient degree is through the positioning and rotational direction of your props (outside-downward).
Good demonstration! I could hear the flight controller changing prop speeds more rapidly when you didn't have the vortex generators on the wings. How hard is it to fly the transition so that the model is not sinking while it has significant forward airspeed? I think that flying forward, sinking, and having the props rotating slowly and flying through their own downwash will be difficult.
Would be interesting to see the difference in this larger style vortex generators and say the smallish ones like you see on the wing of the E-flight ultimate. Also are side force generators fond on wing tips on 3D models also acting as vortex generators? Great stuff thanks for making it available.
hey I know you use catia for modeling and I am assuming you have the student licence. do you pay because you think the skills will transfer to a future job at a bigger company or are there actual advantages to other programs like f360, creo rhino etc.
+Simon Barbarasch I am fortunate enough to be able to get the Catia student licience free from my university, and yes I feel the skills learnt from it will help with future job opportunities. However, once I finish my degree, I will look into free CAD softwares available anyway for hobby use
StantonFPV OK cool. I use solidworks and fusion 360 currently but I'm trying to break away from fusion because not many in the industry use it. strongly recommend for personal use tho. also, do you know anything about Creo and what it's good for and used for?
Very Nice VTOL, I love to build like this.Can you please tell me your KK2 mini VTOL firmware version you used. If you don't mind please give me the detail KK2 settings numbers of your KK2 mini.With Best WishesSoe Moe Aung -Myanmar - Burma
Low forward speed at high angle of attack is where these "should" do most. Not in full powered lift phase (especially in a model aircraft with an "obscene" thrust ratio -compared to a fully laden V22 on short takeoff).. Now the real efficiency gains come from optimal size and placement so they provide maximal benefit in low speed without causing harm to high speed (low angle of attack) flight. Finding an optimal solution may not provide real gains when Hover Power isn't a problem (and scale effect). Great seeing Research in "real time".
Love your videos man, been watching for a while and... Dude, it is only in the stillshot at like 0:57 seconds in... And I'm no aeroplane engineer or anything, but the tips of your wings are open???????? I cannot imagine this helping anything, at all, and perhaps the vortex generators would help if they where acting on a.... closed system, not an open one ;)... Just my 3 cents worth.
El perfil aerodinámico, tiene el borde de ataque muy agudo..... Haz el borde de ataque mas redondeado, para que se porte mejor el perfil en bajas velocidades...
Great job ... I was tarted to think about two rotor vtol and check in youtube if somebody done it already. I have noticed that this is not a simple task to do and as far as I can see you use very scientific approach to do it. I don't have much background with a rc planes and this will be the difficult part for me. I am intended to use your research as a base and see what will happen.
tom - very interesting. I eagerly await each of your videos to see the issues and progress. please keep it up. I noticed that you don't seem to have any way for people to donate to your projects. I hope that that is because you are earning such a large salary that you can easily fund this yourself. if that isn't the case, how about patrion or paypal viewer contributions ?
+youpattube1 currently I feel my channel is just starting to grow and I would prefer not to ask for donations yet. Haha unfortunately I'm not earning a salary at all yet due to being a student, but the youtube ad revenue keeps my hobby running and the videos coming. Thanks!
Shark scales? Not sure if this has been suggested before, but have you heard how the design of denticle scales in mako sharks are being trialled to increase efficiency in airfoils? Would you consider 3d printing a skin of shark scales and test efficiencies vs normal airfoil skin? royalsocietypublishing.org/doi/10.1098/rsif.2017.0828
Ad the other reason they r on the real thing is because b4 they had them on pilots crashed when landing ad as soon they put them on the crashes pretty much stoped so that’s y they r on as it stoped the crashes in landing as it used to just Stall be4 it land if that makes sense
vortex generators on a vtol plane aren't that usefull really, they decrease you stall speed, wich means you can fly slower (usefull for cropdusters of firefighting planes and such) but on a vtol you can already fly as slow as you want. the reason they are on the Osprey is probably to make it easier for the engines in slow flight. this will reduce fuel consumption. For you it's easier to fly when using them but thats because the explained 2 stall speeds because you only have vortex generators on half of each wing. if you look at the osprey, his entire wingspan has it so this wont happen with the osprey
Make a mechanism for vortex generators that goes UP/Down with the servo at the wing Tip. When you are full forward Vortex generators are down in the wing...when transition to vertical starts they rise from the wing. All that to impact efficiency while full forward with less drag.
This an awesome video. I'm Mechanical Engineer and my undegraduate theses was about airfoils. I never see before a better explanation and demonstration of Stall phenomenom and useful devices flor preventing it with a CFD Analysis and field experiment. Congratulations Tom!!!
VGs will increase your skin friction drag (as opposed to induced drag from the wingtip vortices, or planform/area/pressure drag) because they help move fast moving fluid closer to the wing surface. The flow profile RIGHT at the surface of the wing is linear or close to it (for zero pressure gradient boundary layer flow it is linear), and intersects the origin due to the no slip condition. The drag is proportional to the slope of this line (the velocity gradient at the surface) so as you increase the slope/gradient by injecting/mixing faster moving air to the near wall region with the VGs, your skin friction drag goes up. (Also you have losses from the momentum imparted to any vortices persisting in the wake, as well as increased frontal area due to the VGs... on real aircraft these are quite small but on your model the VGs are pretty huge relative the wing cord, so these effects may be competing with or even overwhelming the skin friction increase effects.
BTW, your use of the term boundary layer was not quite accurate. It seems that you were confusing the boundary layer with the separation bubble. There is always a boundary layer over any solid surface (assuming continuum mechanics, not rarified flow, or infinitely close to a sharp leading edge) with attached flow. The local skin friction indicates how close you are to having a separation bubble. When the skin friction (proportional to the velocity gradient at the surface) reaches zero due to the pressure gradient, that is where separation happens, as you correctly drew in your diagrams. The region of recirculating flow associated with boundary layer separation and stall is typically called a separation bubble.
Interestingly, if you try to design airfoils and fuselages to minimize total skin friction, you WANT to be as close to separated flow as possible over the largest possible area, because local skin friction is proportional to the velocity gradient where the boundary layer meets the vehicle surface. The problem here, however, is that the vehicle is so close to stall/separation that it is not practical or controllable. (i.e., you are near stall at 0 angle of attack, or some small positive angle of attack).
With conventional wings, the skin friction (in the airfoil coordinate system) is minimized right before stall. The problem is that, in the coordinate system fixed to the direction of travel, the lift vector in the airfoil coordinate system starts to point backwards in the direction of travel coordinate system, as the pressure differential between the top and bottom of the wings increase. (This will also increase the induced drag.)
I'm not sure exactly why the Osprey has the VGs but as you alluded to, there are two main uses for VGs, fences, and other high lift devices like slats and flaps: Delaying stall at low speeds/high AoA, and controllability at these conditions. VGs are particularly useful upstream of control surfaces, since their control authority is derived from redirecting the momentum of the air flowing over them. If the boundary layer separates, then there is no/less airflow over the control surface, and you loose control authority.
The Osprey is interesting because from that photograph I see at least 3 types of passive flow control/high lift devices: VGs near the leading edge/quarter chord on the top surface, fences adjacent to the pivoting engine nacels, and fixed leading edge slats running the length of the wing.
Any way, super super cool project. Keep up the great work, and good luck in school!
Good to see someone pick up on the fences on the Opsrey - I was watching the airflow at the end of the wings on Tom's model and it definitely looks as if spill from the props is stalling the wing tips; was just thinking fences would be a good mod!
Saludos de Ecuador eres un genio. No que otros solo se ponen hacer piruetas y tomar fotografías y filmar ya se creen expertos.
Experto eres tú así es como deben hacer tutoriales bien explicativos.
Felicitaciones Maestro
When starting RC flying in the 90's, I got told to build my wings with the wingtips pitched down slightly. That of course decreases the angle of attack at the wingtips which makes them stall after the center of the wing. The same rationale goes behind only adding flaps to the center of the wing. The center part will stall first and you start to loose altitude, but since the wingtips still have nice airflow all the way back to the ailerons, you can still control the descent. Your vortex generators seem to have the same effect!
When flying full scale, I've experienced much reduced minimum speed when having vortex generators compared to without. Could it just be that the Osprey just have them there for increased low speed lift? I assume that would take some load off the engines during slow flying.
Pitching down the edges also decreases induced drag. Additionally, giving the edges (where the controlsurfaces has the most leverage) a lower stallspeed increases control near stall- speed
Many years ago when I was learning to fly the school had a Chipmunk aircraft with wool tufts on one wing so it was possible to see exactly the effects you have replicated here. Took me back a very long time...
This is one of you best explanation videos. I really enjoyed it thank you
There were was a team of student engineers who did a senior project at my school that was similar to this aircraft but yours is 100x more successful haha. Really greats visuals! I gotta learn to animate over video like that.
Haha it was pretty easy making the animations in photoshop, thanks!
Tom, I want to share some of my experiences with vortex generators and vortilons. (leading edge vortex generators). I owned a Rutan VeriEze full size plane years ago. The main wing is swept back on this plane and when tufted the air flow would sweep out longitudinally and run parallel along the trailing edge of the wing. This was most noticeable at slow speed as the ailerons became very sloppy and AOA was very high on final approach making visibility very poor.
Vortex generators were attached along the top of the wing forcing the airflow to run along the chord. This dramatically improved slow flight AOA (slow flight AOA changed from ~10 degrees with no vortex generators to ~
Hi Tom,If possible, could you make a short gliding film with engine turned off? Just to see the real plane performance?Would be interresting how slow you can fly now with the vortex GeneratorsThanks, Peer (Pepponski)
Fellow RC-ginger here.
Nice work dude, awesome video.
Good visual on the Vortex Generator function.
Vortex generators are sometimes added to increase control surface authority.. The Vtol probably has them to still have control of the ailerons/flaps while in the transition from slow forward flight to hover..
I wouldn't say they put them on to lower the stall speed necessarily but more keep the control surfaces active that little bit longer.. I could be wrong, but you can see them on commercial passenger jets also on the elevators. My uncle said there on his glider just at the ailerons and that's what there doing.. Said it keeps the airflow sticking to the ailerons for slow thermal turns..
This is great science! Fun to watch. I just thought of a thing, might the vortex generators be a bit to big, meaning tall and long? Keep it up! Great fun!
Like your experimental approach Tom. Nice work!
The flow profile RIGHT at the surface of the wing is linear or close to it (for zero pressure gradient boundary layer flow it is linear), and intersects the origin due to the no slip condition. The drag is proportional to the slope of this line
Great work and video is excellent ! Real world conditions are so changeable compared to wind tunnel experiments. It is amazing how well you were able to complete this sequence.
Guy each video you do would take a year for me ! Great job !
Unloading the wing in transition, using the rotors, reduces the wing stall speed. The most efficient way to fly is wing-borne, to exploit the high L/D ratio, so it makes sense to have vortex generators and keep the wing as close to stall as possible. Even past stall, the wing is much more efficient at producing lift than rotors.
Very interesting video, great work to visualize the stall effect and the vortex generators effect.
Nice Work! I would recommend you to print smaller sizes of the vortex generators (you are getting large amount of drag from those big ones you printed - resulting in wingtip stall) .Try to put the new small ones all across the wing from tip to root.
There shouldn't be a large gap between the wing tip and the motor, this area should be smoother..
Extend the flaps full down when you are taking off vertically, this will gain some stability and reduce wing tip stall.
Good Luck!!
Excellent video and great work on your concept VTOL. I have been thinking about making one for a while but am unsure of how to set it up for hovering.
It would be interesting to see what happens if you reverse the prop direction at each wingtip.
Not to be critical, but the right wingtip vortex is counter-clockwise ( en.wikipedia.org/wiki/Wingtip_vortices) so the right prop being clockwise is counter to the tip vortex. Again great video!
I like the way the elevator works. is there a name for this? I mean, when a whole lot more of the tail moves than on normal elevators
Variable pitch vortex generators that cycle straight to full angle of attack mid engine pod transition (not linear, full VG rotation over middle 30' approximately) . not sure if the weight penalty would offset the drag efficiency / controllability gain. you could have a central servo or just 3d print magic a cam wheel on the pods to a drive shaft. this could work on any wing i guess not just for your VTOL
Ps i make no claims to any expertise in any field and i'm sure it's been thought of before. this is more of a question.
Came here to say this, but make them retractable as well. Just cam them to raise straight up through slits in the covering, and then to proper angle once clearing the surface, and then back down to surface to lock them in. Cam it all to motor turning from horizontal to vertical. Now I have to go purchase a stinking 3-D printer so I can do this. I suddenly have an overwhelming need to see this in action.
Tom, try wing fences - a la Mig 15. I have used them to good effect on my models. Tried VGs and slats too to lesser benefit. Best regds. Peter
just one observation - The vortex generators on the Osprey are set further rearward than the one's you installed on your wing. This might make a difference in stall speed change.
Tom -
a little advice, or at least your thoughts on the subject, please. one of the reasons i have paid such close attention to your vtol videos is that, where i live landing a fixed wing plane will be difficult (too many house closeby). launching i think i can handle. why not use a quad (which i would prefer) ? because i live near the gulf coast in florida, and would like to send out an fpv drone to see what is going on around a little island about 3 miles off the coast. from my house it is about 6 miles each way. so i guess to cover this long a flight i will need a fixed wing. but a landing strip is not available. would a vtol get me enough range ? what about a standard fixed wing plane with a deployable parachute ?
These are more complex designs but I have some comments on thoughts maybe you should try.
1) I'm not sure you were getting the expected outcomes you wanted due to the fact that on a slow moving model, the Reynolds numbers are simply too low and too close together compared to that of the Ospray. Empirically, I am sure that the VGs probably have more to do with horizontal forward flight than the VTOL capability. Consider your Drag vs. Lift vs. Velocity calculations.
2) Maybe you could investigate having some washout in the wing, to change the angle of attach and make the stalling characteristics at lower speeds more favorable when transitioning and at higher angles of attack. Then you wouldn't have to worry about the added drag and weight which is probably more significant than your attempt (due to #1) to maintain laminar flow over the outer portions of the wing with the VGs.
Keep up the good science and I am excited to see your progress. You are an innovator!
Amazing video. Thank you for combining your high-tech graphics with footage ;) Seriously though, really good content.
Thanks!
depends on the engine prop configuration, speed of the craft and the type lift involved..sometimes yes sometimes no
hello, you have great skills in explaining. I think I learned something.
As always, a great video Tom!
really looks like the flow is dominated by the propwash not the forward airspeed when you're going that slow. Also something I've found with tufts is you have to use smaller tufts than you think; the air movement you get inside a separation bubble is really really low energy compared to the attached flow (which i guess is obvious cause that's why it happens).
I think this is one of those things where the wing loading vs Rn is soooo different from a full sized plane, especially such a insanely high-wing-loading plane like an Osprey, that you might not want to be looking at
Old floater polyhedral r/c gliders used to use these stick on strips that were used by tailors or something, little 1/8 inch paper or fabric with a 1/4-inch zig zag pattern that would trip the boundary layer to avoid a bubble forming.
I'm just wondering if there's really enough energy at this scale and this wing loading to get the kind of useful vortex to form that can actually do what you want. I saw you had video from a guy doing CFM on a model of the vortex generators, but did he really have the parameters set to match the scale and speeds of your plane?
I used to work on F-18s in the US Navy, if you look at the wing from the tip, there is definite twist from tip to root, so the root stalls first, is probably why the plane is so good at high alpha flights. I can't tell if your airplane is using any auto pilot gyros or not? How much aerodynamic control are you using, ailerons etc, vs just motor thrust control? Anyway, I'm enjoying watching your process and progress, nice job on the incremental testing. Well done!
Clearly they are effective, they only help when the transition isn't perfect. So as your piloting skills improve the less you will need them.
What do you think of Adding wingtips to the Motor Mounts, so the Aircraft is slowing down faster at the transition.
And you shouldn't need the aileron anymore.
you should add winglets cos that sharp wing edge is just a drag magnet.
I love this project!
I know this vid is over 2 years old, but why dont you have the vortex generators pop up at the same time your motors transition, and be flush when if forward flight? That would probably solve both concerns
Great project. Great progress. Do you have a link to some more information on the KK2 Setup for that type of plane? Very much like to build one on my own.
I know this video is 4 years old but I thought I'd share my understanding anyways. For low reynolds numbers such as RC scale, especially when approaching low vtol speeds, vorticity means almost nothing. Vortex generators, P factor coefficients, wing twist, variable airfoils, all moot. Even super high aspect ratio wings begin to suffer efficiency losses. What is predominant at this scale are the effects of general pressure, and the only way you can really affect that to any efficient degree is through the positioning and rotational direction of your props (outside-downward).
Very nice. Well described and illustrated.
nice job mate I was wondering if there are any rules or formulas for the actual height of the wing as in thickness compared to chord and length
Really enjoying content, really informative 👍
Nice work! Are your props rotating with or against the tip vortices?
+Gary Paisley the props are rotating with the tip vortices. So if looking from the back, the prop on the right is rotating clockwise. Thanks!
Good demonstration! I could hear the flight controller changing prop speeds more rapidly when you didn't have the vortex generators on the wings. How hard is it to fly the transition so that the model is not sinking while it has significant forward airspeed? I think that flying forward, sinking, and having the props rotating slowly and flying through their own downwash will be difficult.
Would it help if the vortex generators were bigger ? Or that they stretched further aft towards the trailing edge ?
great video, how about golf ball type dimples on the top of the wing? would that provide more lift at slower speeds
Would be interesting to see the difference in this larger style vortex generators and say the smallish ones like you see on the wing of the E-flight ultimate. Also are side force generators fond on wing tips on 3D models also acting as vortex generators? Great stuff thanks for making it available.
You seem to be good with multirotors - could you do a video on how to set up a tricopter with no FC, only basic gyros? or is this too complicated?
Why not just put vortex generators on the whole wing?
Great video, as usual!
Great job do you have a link for the stl files for the motor tilt etc would like to try and work on making a Vtol plane Thanks
VG's don't do much at low Re's. i.e. Small wings at low airspeeds.
I'd say a better thing to try is a leading edge slot.
Tyler H i agree with you. Even better could be a suction at certain point of upper face of wing...
You make great videos, this one especially!
Thanks!
Just found your channel, awesome video's man. Very well done, I'm hooked!
Well build Vtol man. Awesome!
When you have the motors lifting the plane the pressure under the wing will be lowered.
Very interesting, science in practice!
hey I know you use catia for modeling and I am assuming you have the student licence. do you pay because you think the skills will transfer to a future job at a bigger company or are there actual advantages to other programs like f360, creo rhino etc.
+Simon Barbarasch I am fortunate enough to be able to get the Catia student licience free from my university, and yes I feel the skills learnt from it will help with future job opportunities. However, once I finish my degree, I will look into free CAD softwares available anyway for hobby use
StantonFPV OK cool. I use solidworks and fusion 360 currently but I'm trying to break away from fusion because not many in the industry use it. strongly recommend for personal use tho. also, do you know anything about Creo and what it's good for and used for?
Very Nice VTOL, I love to build like this.Can you please tell me your KK2 mini VTOL firmware version you used. If you don't mind please give me the detail KK2 settings numbers of your KK2 mini.With Best WishesSoe Moe Aung -Myanmar - Burma
Low forward speed at high angle of attack is where these "should" do most. Not in full powered lift phase (especially in a model aircraft with an "obscene" thrust ratio -compared to a fully laden V22 on short takeoff)..
Now the real efficiency gains come from optimal size and placement so they provide maximal benefit in low speed without causing harm to high speed (low angle of attack) flight. Finding an optimal solution may not provide real gains when Hover Power isn't a problem (and scale effect).
Great seeing Research in "real time".
Great things.. I really enjoyed your video.
Thanks for sharing.
Damn dude, great stuff. keep it up!
what about ducting the prop?
Love your videos man, been watching for a while and... Dude, it is only in the stillshot at like 0:57 seconds in... And I'm no aeroplane engineer or anything, but the tips of your wings are open???????? I cannot imagine this helping anything, at all, and perhaps the vortex generators would help if they where acting on a.... closed system, not an open one ;)... Just my 3 cents worth.
Really interesting! 👍
El perfil aerodinámico, tiene el borde de ataque muy agudo..... Haz el borde de ataque mas redondeado, para que se porte mejor el perfil en bajas velocidades...
Great job ... I was tarted to think about two rotor vtol and check in youtube if somebody done it already.
I have noticed that this is not a simple task to do and as far as I can see you use very scientific approach to do it.
I don't have much background with a rc planes and this will be the difficult part for me.
I am intended to use your research as a base and see what will happen.
Think you can make a rc glider?
Nice video, but it is well known that air don't compress belov 100m/s in any substantial way.
Great video, very informational! :D love your videos :))
At the Reynolds number of models, vortex generators are of scant little use.
Would slats not work better on high alpha maneuvers?
+GeeTR 63-71 possibly yes, however I have yet to test this. Maybe a future video idea ;)
Yea slats may give you better high alpha performance - granted this is not a fighter but who cares. :)
What type of 3d printer do you have?
Awesome Tom!
R.I.P Sam Sheperd :(
Does anybody know what music this is? thanks!
In my experience, the vortex generators do not need to be that large.
tom - very interesting. I eagerly await each of your videos to see the issues and progress. please keep it up. I noticed that you don't seem to have any way for people to donate to your projects. I hope that that is because you are earning such a large salary that you can easily fund this yourself. if that isn't the case, how about patrion or paypal viewer contributions ?
+youpattube1 currently I feel my channel is just starting to grow and I would prefer not to ask for donations yet. Haha unfortunately I'm not earning a salary at all yet due to being a student, but the youtube ad revenue keeps my hobby running and the videos coming. Thanks!
Awesome!
Sam Shepherd had died in a bike accident recently. RIP
RIP Samm Shepherd
I sincerely wonder who would give this an honest thumbs down, and why.
Shark scales? Not sure if this has been suggested before, but have you heard how the design of denticle scales in mako sharks are being trialled to increase efficiency in airfoils? Would you consider 3d printing a skin of shark scales and test efficiencies vs normal airfoil skin?
royalsocietypublishing.org/doi/10.1098/rsif.2017.0828
The Vortex Generators are even on the V22 Osprey RC model: (th-cam.com/video/m4y51yMRnEM/w-d-xo.html)
Ad the other reason they r on the real thing is because b4 they had them on pilots crashed when landing ad as soon they put them on the crashes pretty much stoped so that’s y they r on as it stoped the crashes in landing as it used to just Stall be4 it land if that makes sense
RC Rockstar!
It's cool
Make about tubercle blade
vortex generators on a vtol plane aren't that usefull really, they decrease you stall speed, wich means you can fly slower (usefull for cropdusters of firefighting planes and such) but on a vtol you can already fly as slow as you want. the reason they are on the Osprey is probably to make it easier for the engines in slow flight. this will reduce fuel consumption. For you it's easier to fly when using them but thats because the explained 2 stall speeds because you only have vortex generators on half of each wing. if you look at the osprey, his entire wingspan has it so this wont happen with the osprey
I'd use dental floss instead of string.
Молодец!!! Жаль не понимаю что говоришь... =)
tom pls help
bro i came for spoilers in the desc, you let me down, unsub
Stool
Make a mechanism for vortex generators that goes UP/Down with the servo at the wing Tip. When you are full forward Vortex generators are down in the wing...when transition to vertical starts they rise from the wing. All that to impact efficiency while full forward with less drag.