The simple "finger"-explanation of the center of pressure finally made it click for me. I had a lot of lectures in university about all aeronautical subjects and I always took the center of pressure with a shoulder shrug. I could kind of get behind it and I understood the concept of why you need it, could solve problems in exams involving it, but I never had an intuitive feeling for it. Now I do! Thank you!
As an aeronautical engineer who has sat through many lectures as a university student on aerodynamics involving way too math it's nice to hear such a lucid talk and not get lost in the calculus and mathematics. Some of my old profs would do well to emulate more of your style and less mathematical proof!
Agree, I'm specializing in Turbomachinery (so lots of fluid mechanics and blade profiles) and I have the same experience. This basic intuition is what provides the foundation to build the math upon, at least for me. Plus the intuition is just plain fun! Sorry for the pun. ;)
Andrew Carolus and Fredrik Wahlgren: May I ask if you use a CFD software now, or if you only do mathematical models in your work and or hobby? I'm very interested in having some good CFD recommendations for aerodynamics. I'm well read in using and creating these models in software and am just looking for a short/simple wing design cfd software or program for all my tinkering and scientific brain to make all the shapes and cambers it desires. thank you!
Thanks for keeping your explanations simple. You are not talking to aerodynamicists who still cannot agree, but model airplane people who need only a basic understanding, even if that looks in error to the experts. Thanks again
Hear, hear! I am an electrical engineer (digital design) and I do not have the time to take 3 aerospace courses and study partial differential equations (again) to fully understand these concepts. You did it in just under 22 minutes! Excellent piece of work Bruce!
I am 13 and going to be building a wind turbine so I decided to learn some basic aerodynamics. Even I could understand. That was one of the most interesting lectures I have heard
Keep it up Bruce, I've been slacking on your channel a bit (due to new Canadian regulations getting me down) but these videos are universally interesting, so when one pops up on my subscription feed, it's impossible to ignore. Thanks man!
Hello, thanks for this video... I'm not an engineer, just an ex USAF mechanic. Some time ago, while recovering from surgery, I build a paper 3D F-102 from internet plans, later, I figured it may fly as a slingshot glider, and it did ! It exhibited all the characteristics of a fow speed delta, it did the "Delta dance" it landed almost verticaly when it got behing the drag curve, etc... So I build 2 more, and this time with cambered, flat bottom airfoils so I'll get more lift... They didn't fly, they tuck under, the only way to fly 'em was to move the cg way forward and add up elevon... in one case I added a canard and it did well... so from now on I just build symetric airfoils but they also need a bit of up elevator or a Gurney flap... Thanks for your video !
Thank you Bruce. I knew about Reflex, but now I know that reflex applies to flying wings only. I started flying fixed wing aircraft using a flying wing and thought that all aircraft needed a degree of reflex. Now I know that is not the case. I look forward to learning more on Part 2.
Awesome! Been discussing with my mates why flying wings defeats the use of a regular lifting airfoil because of the addition of the reflex. As such, all my flying wing designs have been a simple symmetrical airfoil. Maybe not as efficient but definitely easier to construct and quite stable. Thanks for explaining it well.
Try this part of the explanation of lift: *ruclips.net/video/3MSqbnbKDmM/видео.html* . Cheers, I studied aerodynamics and consulted with some well known experts along the way, specifically on this.. . .
The main problem with flying wings is the total downforce moment that can be generated by the reflexed TE is very limited because of the short arm and this results in a very limited amount of forward CG that can be tolerated. On gliders this isn't too much of a problem since a wide CG range isn't necessary, but not on powered planes. Jim Marske's FW gliders have very good handling and stability and their performance appears to be slightly better than a tailed glider with the same overall plan form. On the Genesis sailplane, a Marske design, he added a small horizontal tail surface at the top of the swept fin. He was strongly against adding it but was pressured into it by the project's financial backers, who thought it would make the airplane easier to sell.
I've long been interested in aircraft, and understood conventional aircraft design, but the lack of tail on flying wings always confused me. I was never sure where the pitch stability came from, thanks so much for this video. I always assumed that because flying wing designs feature swept wings that the wingtip somewhat acted as the tail, but reflex makes a lot of sense. This makes designing an RC flying wing seem a lot less intimidating as well as reflex could just be trimmed into the ailerons. Gonna give it a go!
I fly quadcopters and want to get a plane. I'm trying to decide on a conventional plane or a flying wing. The fact that so many people are using wings instead of planes made me want to check out the pros and cons. I recall a documentary about the first flying wings and them being very unstable and killing some test pilots. I thought the B2 bombers must fly because of computer control of the flight surfaces, correcting thousands of times a second faster than a human could do. I assumes all RC wings had flight controllers with gyros doing the same thing but I see plenty of flying wings that don't have flight controllers. Just an esc, motor, receiver and a couple of servos. This is a really interesting video series. I'm learning a lot. Thanks for making them.
Great basic explanation again. Love the way you cut through the arrogance of some of the 'experts' who love to complicate the issues to claim their knowledge as sacrosanct!
Another very clear video lecture, I first started watching your videos when you explained the advantage of having a proper inlet cowl around a ducted fan in an earlier video.
I thought that you were going to draw the Yin/Yang symbol for a moment there Bruce. A truly well balanced wing. Excellent and informative video! Thanks.
I love watching this guy lol... He's so informative and very inspirationally positive and upbeat... Boy am I glad I joined his channel! Thanks Bruce! (Are all Aussies friendly? Damn Ima move there lol- they sure are not here in the states) and I'm heading straight over to patreon to give some well deserved financial support and bonus content this guy definitely deserves it (no in no way am I conoenapsated nor have I ever even heard of Bruce I'm just sincerely pleased finding his channel)
i was just trying to build a flying wing and stumble upon this video this is very good explaintion of lift and like how things are little bit different for flying wing now i have idea how lift is generated on flying wing i hopefully will going to build a really good flying wing..
More videos sir this helped me a lot because due to the pandemic i can't start college and i'm taking aircraft maintenance technology this is very helpful!!! THANKS
Thanks for details explanation Mr Bruce,even you speak very fast but still can catch some clue and information.....youtube have a undertitle here that can help us...thanks and have a great day
Use to do 100mph LOS wings. Oscillations were a problem to the point that canopies and batteries would eject at high speed. This was especially true if the wing was a bit flexible. Looking forward to the next video.
This principle is what I use on my Control Line Pulse Jets.The wire adds lots of instability for up & down motion so a heavy nose is perhaps the only way to solve it.The down fall is a wing lifting behind the balance point & so it adds drag .Stability sometimes costs speed.The fastest PJs on wire are hardest to fly.Less fun but win races.Most people dont realize the wire has so much drag up & down Any wind lift in front of the wire is no good.But you must have the balance point in front of the wire support point to keep the model square to you.
Conservation of mass and the fact that air is an incompressible fluid explains lift quite simply. It works like this. Since the cross section smaller above the wing in order to pass the same mass of fluid (volume) through a smaller area it mus increase in speed. An increase in fluid speeds results in a decrease in pressure for laminar fluid flow and hence the lift.
Great stuff Bruce. Like the way you simplify, even if the purists aren't all on board :-). Two comments, already partly covered by others: you refer to decollage as being the difference between wing and horizontal stab pitch angle, or off-set. I believe the correct French word is decalage, which means off-set. Decollage = take-off. The stabilising effect in pitch of the conventional tail: speed maybe has a role, but if so the response time is slower as the pressure profile and therefore resultant lift on the tail takes time to develop. The more immediate stabilising effect is the change in alpha the tail is seeing with the speed instantaneously being the same. Love your channel, mate.
I think washout is very important too. By doing this you are creating something similar to reflex at the tips. Combined with the sweep the stabilising effect is produced at a longer moment arm and therefore you need less deflection and force. You can eliminate reflex near the centre of the wing and also reduce the tip stall tenancy and make it wobble less.
You should explain how flying wings WITHOUT reflex work. Such as a simple paper airplane. If you properly place the CG on a piece of foam board, it will glide without any reflex. When you described the symmetrical airfoil flying wing, you had reflex with a your elevons; but you should also explain how symmetrical airfoil flying wings fly without out reflex in the elevons. (My hint to you is Center of Lift vs Center of Pressure.) Excellent videos, keep them coming. I suspect you'll be making a video on the Taylor vs FAA case :-) Also I really like your fixed wing, work bench, and how to videos :-)
I read some of the comment critics. A lot of verbiage. Simply as you stated, air flow over a modified teardrop shape, with an attack angle above horizontal, produces lower pressure (partial vacuum) on the top of a wing. Air deflection, due to declining front to rear chord, produces higher pressure on the bottom of a wing. The differential causing lift. Forward velocity due to the application of thrust increases air velocity over the wing.
Very interesting stuff, this helps me to understand the flight behaviour of my plane better and really explained in a super understandable way! 😊 I am already looking forward to the next video.
10:00 - it's not that simple. If the nose of the aircraft pitches up, that doesn't necessarily mean that it'll slow down. It'll slow down if the angle of attack rises - and if this is the case, the angle of attack of the horizontal stabilizer will change it's angle of attack too (by exactly the same amount). As the AOA (angle of attack) rises, the stabilizer will first produce no induced lift force, then it'll start to create lift, providing desired momentum on the CG. Speed change isn't the main factor here. Another thing is, that as the AOA rises the Cp (center of aerodynamic pressure) moves forward on the main wing (especially for cambered airfoils) closer to CG, so the momentum needed to compensate this force is lower than it was when the AOA was lower. The static longitudinal stability is not always achieved by creating a download on the tail. This is true only for the designs where the CG is placed in front of the Cp of the main wing. Even then, there are situations where the load on the tail is vectored upwards - for example the high angle of attack situation. High angle of attack with unsymmetrical, cambered airfoil, causes the Cp (Center of aerodynamic pressure of the main wing) to move forward - often in front of CG - this way the aircraft wants to rise its nose and we'd like to counteract by applying the positive lift on the tail. Apart from that, great video. Cheers!
THIS is youtube. Sir, I love you video. My plan is to build an fpv-plane in very small. Not done Deltas before and had no idea before. I will watch these videos and see and tell whether it worked :)
Very informative Bruce! I've got a wing built from left over wings from an Air Hogs Titan kid's chuck glider. It has quite a bit of rearward sweep in the wings and some reflex has been applied. Its maiden is still awaiting so I have no idea how it will fly. Wingspan is 47' with some Coroplast winglets at the tips. CG works out to be quite rearward because of the swept wings so getting it to balance there and with some extra given to the nose has been a treat! Had to add quite a bit of dead weight even though using a 3S - 2200 battery. Really no science has been applied to it during its construction but hey, it looks good! :) Looking forward to your continuation on this.
Thank you. Very interesting. I was wondering why they never add dimpling to RC aircart to reduce drag? Golf ball get much further distance with the dimples.
This is great stuff Bruce. Please don't forget to post Part Two and maybe you could do a Part Three on how I can make a flying wing out of my FAA UAS certificate! [Thanks Mr. Taylor)
Great video, I've been watching your reviews for years, two things, air weight about 1275 g per cubic metre so the force is quite high... also consider Coanda effect, the top of the wing generates lift as well as it moves over the trailing edge.. ( ie water will follow the back of the spoon if held under a smooth water flow under a tap ) .... I've wondered for years as a percentage where is the lift ... Newton ( 80 % ) Coanda (15%) Bernoulli (5%) ... Also wondered where the Reynolds numbers fit into this great subject. :-)
Percentage doesn't make sense, though I can confidently say Coanda has nothing to do with free flow over a single airfoil. Coanda is about fluid jets and is a viscous phenomenon; flow curving around an airfoil is a requirement even for inviscid flow. All of the lift is generated by the pressure distribution and all of the lift is generated but the deflection of air downward; both methods work fine.
Decalage is the angular difference between biplane wings. The difference between wing and stabilizer is longitudinal dihedral. More dihedral, more stability. Less dihedral, less stability and more efficiency
Thanks for the excellent video. It brought the following questions to mind. 1) Don't flying wings need washout (where the angle of attack goes down from the chord to the tip) to be stable, or was that a misplaced datum from hang gliding? This would mean a varying airfoil shape as one looks at it going from the root to the tip. But my HK flying wings appear to have the same airfoil along the span and they don't appear to have any washout. 2) Why don't flying wings typically have dihedral? (because they have ailerons to control the roll axis?) 3) Is there an advantage to separating the elevator from the ailerons on a flying wing? It has been suggested that the motion of a separate elevator surface produces less drag than the elevator motion of the full elevons, but this might be relevant only to gliders. 4) Why do most flying wings have swept-back wings? Not all do, some have a perfectly straight leading edge.
1 - Swept flying wings can use washout to give longitudinal stability, basically the tips (being further back) act like a tail. 'Plank' flying wings dont benefit from washout in the same way. But washout is not mandatory on a flying wing, a reflexed airfoil will give the desired positive pitching moment without washout. 2 - Sweep back has a washout like effect so swept rings generally need less or no dihedral.. and yes you are right, flying wings usually have ailerons so dont need much/any dihedral.
Important to note that the relative airflow that the tail "sees" is coming from a different angle than what the wing "sees", due to the wing's downwash. For example, when gust pushes nose up and aircraft slows down, wing is producing less downwash and effective angle of attack of tail is reduced, leading to less tail down force.
Hi Bruce - as an avid and often misguided flying wing enthusiast I would just like to point out a couple of things. In the section on drag you did not mention the two types of drag - profile and induced. Profile drag is from canopies, fuselages, undercarriage and other things sticking out and also skin friction. Induced drag is the drag created from creating lift - more lift more drag. The point is that a wing can be more efficient i.e.: give greater range for a given fuel consumption than a normal plane because it usually has vastly less profile drag as it has no fuselage or tail. Additionally the reduction in lift you mentioned because of the 'reflex' also lowers the induced drag as the reflexed part does not produce any lift so no induced drag only a small bit of profile drag. So overall, all things being equal, a flying wing should have less drag than an equivalent conventional aircraft. However due to all sorts of factors this is rarely realised in practice and the flying wings produced were never so overwhelmingly superior that they swept the skies of everything else. The main problem with flying wing in practice and why they sort of withered on the vine is you can't easily add high lift devices to them i.e.: flaps. Because the wing has nothing really to trim changes in pitch, lowering a flap cannot easily be countered with a lifting surface to cope with the pitch change. So generally flying wings can't really use flaps properly and therefore cannot be landed as easily. The flying wing gliders could not use camber control or any of the other tricks modern gliders use to fly so well. Delta flying wings like the Mirage or Concorde used extreme angles of attack on landing to compensate. And of course they are less stable in yaw because the vertical tails that most of them have do not have enough moment (distance from the wing) to have enough force to affect yaw changes quickly and as I found out to my cost they are very sensitive in pitch and do not like to loaded up to high wing loadings. I like wings mainly because I am a terrible pilot and a wing has less to break, less to fix and less to throw away when I am done with them :-)
The dictionary says, "décollage...cutting...removing, pieces of an original image," so it's either the narrowness of the fuselage between the wings and tail, or it's the counter-lift applied at the tail to keep the plane from nosing-over in level, flight (highly technical)....
Technically (we learned ca '60's) the CP already behind the CG tends further behind at higher speed... We also learned the underside of a wing is cambered too, to slow the air there thus increasing pressure below....
I’ve come across some great videos on circulation theory here on RUclips that I think you’ll quite enjoy. Rather than thinking about Bernoulli and Newton, circulation answers the question and then explains the trailing vortices. Think about why people rough up a cricket ball to get spin, and go from there 👍🏼
Have to interrupt you to say Decalage is the difference in angle of incidence of the two wings of a biplane. What you are referring to is usually called longitudinal dihedral.
I have made a lot a flying wings and I did not put any reflex in them.. They were 30 to 60 degrees back and the the wing was in a variable constant cord with outsides of the wing at -2 to -3 degrees and pitch up about 15 to 20 degrees. They look a V only with 15 degrees pitch up. They hand flight with the biggest one was made out of 2 slip cardboard sheets and it flew 3 blocks with by hand. It was made in 1973.
I think some of this is wrong, especially the explanation of the tail plane stabilising pitch. A flying wing can be made much more efficient if most of the wing has a normal lifting aerofoil while the swept back parts of the wing near the tips has reflex. Relex at the tips of swept back wings have a greater leverage and so greater stability.
Mr. Bruce : Are you familiar with the stepped wing? The leading 1/3 to 1/2 of the wing being twice the thickness of the rear cord area of the wing, without a sloped transition. A straight vertical step. Theoretically eliminates vortex drag. Apparently increases efficiency when properly proportioned. From what I have read, the design works on flat wings.
Another question I have (in addition to forward swept wings you mentioned you would cover in part 2) has to do with semi-circular designs. Are there any benefits of curved wings in regards to flying wings, or is there a good enough reason for keeping most wings with a straight leading and trailing edge? Please cover this in regards to swept-back and swept forward flying wings if you have time. Thank you, and keep up the great informative and educational content!
Very interesting explained in understandable terms. Seems like almost anything will fly with enough power. I hope you can include some explanation of how a wing with only the top airfoil rates in efficiency. That is a wing made from a single layer curved inwards (upwards) on the bottom. Thanks for doing these informative videos. AMA sent a notice that FAA registration is gone, but they said stay tuned ?
Not many RC RUclipsrs doing whiteboard talks about the basic physics. Thank you for producing this!
Years and years searching for a channel that speaks about aerodynamics in a simple AND LOGICAL way... finally I found you!
Brilliant stuff, watched this over breakfast and it's given me something to think about all day.
Thanks for the physics lesson Bruce. Can't wait for lesson 2. Awesome job mate.
Sir, You have rendered this complex topic in a clear, concise and straightforward manner. Outstanding presentation.
Thank you so much for covering this. I looked on the internet and no one covers this content as thoroughly as you do
The simple "finger"-explanation of the center of pressure finally made it click for me. I had a lot of lectures in university about all aeronautical subjects and I always took the center of pressure with a shoulder shrug. I could kind of get behind it and I understood the concept of why you need it, could solve problems in exams involving it, but I never had an intuitive feeling for it. Now I do! Thank you!
And this is why people love your channel. Great video, Bruce.
As an aeronautical engineer who has sat through many lectures as a university student on aerodynamics involving way too math it's nice to hear such a lucid talk and not get lost in the calculus and mathematics. Some of my old profs would do well to emulate more of your style and less mathematical proof!
Agree, I'm specializing in Turbomachinery (so lots of fluid mechanics and blade profiles) and I have the same experience. This basic intuition is what provides the foundation to build the math upon, at least for me. Plus the intuition is just plain fun!
Sorry for the pun. ;)
Andrew Carolus and Fredrik Wahlgren: May I ask if you use a CFD software now, or if you only do mathematical models in your work and or hobby?
I'm very interested in having some good CFD recommendations for aerodynamics. I'm well read in using and creating these models in software and am just looking for a short/simple wing design cfd software or program for all my tinkering and scientific brain to make all the shapes and cambers it desires. thank you!
I love these types of technical videos, thank you Bruce!!
Thanks for keeping your explanations simple. You are not talking to aerodynamicists who still cannot agree, but model airplane people who need only a basic understanding, even if that looks in error to the experts. Thanks again
Hear, hear! I am an electrical engineer (digital design) and I do not have the time to take 3 aerospace courses and study partial differential equations (again) to fully understand these concepts. You did it in just under 22 minutes!
Excellent piece of work Bruce!
I am 13 and going to be building a wind turbine so I decided to learn some basic aerodynamics. Even I could understand. That was one of the most interesting lectures I have heard
Keep it up Bruce, I've been slacking on your channel a bit (due to new Canadian regulations getting me down) but these videos are universally interesting, so when one pops up on my subscription feed, it's impossible to ignore. Thanks man!
Hello, thanks for this video... I'm not an engineer, just an ex USAF mechanic. Some time ago, while recovering from surgery, I build a paper 3D F-102 from internet plans, later, I figured it may fly as a slingshot glider, and it did ! It exhibited all the characteristics of a fow speed delta, it did the "Delta dance" it landed almost verticaly when it got behing the drag curve, etc... So I build 2 more, and this time with cambered, flat bottom airfoils so I'll get more lift... They didn't fly, they tuck under, the only way to fly 'em was to move the cg way forward and add up elevon... in one case I added a canard and it did well... so from now on I just build symetric airfoils but they also need a bit of up elevator or a Gurney flap... Thanks for your video !
Thank you Bruce. I knew about Reflex, but now I know that reflex applies to flying wings only. I started flying fixed wing aircraft using a flying wing and thought that all aircraft needed a degree of reflex. Now I know that is not the case. I look forward to learning more on Part 2.
Awesome! Been discussing with my mates why flying wings defeats the use of a regular lifting airfoil because of the addition of the reflex. As such, all my flying wing designs have been a simple symmetrical airfoil. Maybe not as efficient but definitely easier to construct and quite stable. Thanks for explaining it well.
His videos are some of the best. I am using these to help my 14 year old nephew learn flight physics for models.
Try this part of the explanation of lift: *ruclips.net/video/3MSqbnbKDmM/видео.html*
.
Cheers,
I studied aerodynamics and consulted with some well known experts along the way, specifically on this.. . .
Love these whiteboard vids you do Bruce, and you havent done one for ages. Please do more, like explaining decalage in depth so i can tune my glider.
The main problem with flying wings is the total downforce moment that can be generated by the reflexed TE is very limited because of the short arm and this results in a very limited amount of forward CG that can be tolerated. On gliders this isn't too much of a problem since a wide CG range isn't necessary, but not on powered planes. Jim Marske's FW gliders have very good handling and stability and their performance appears to be slightly better than a tailed glider with the same overall plan form. On the Genesis sailplane, a Marske design, he added a small horizontal tail surface at the top of the swept fin. He was strongly against adding it but was pressured into it by the project's financial backers, who thought it would make the airplane easier to sell.
I've long been interested in aircraft, and understood conventional aircraft design, but the lack of tail on flying wings always confused me. I was never sure where the pitch stability came from, thanks so much for this video. I always assumed that because flying wing designs feature swept wings that the wingtip somewhat acted as the tail, but reflex makes a lot of sense. This makes designing an RC flying wing seem a lot less intimidating as well as reflex could just be trimmed into the ailerons. Gonna give it a go!
I keep coming to this video! Thank you for everything ♥️
I fly quadcopters and want to get a plane. I'm trying to decide on a conventional plane or a flying wing. The fact that so many people are using wings instead of planes made me want to check out the pros and cons. I recall a documentary about the first flying wings and them being very unstable and killing some test pilots. I thought the B2 bombers must fly because of computer control of the flight surfaces, correcting thousands of times a second faster than a human could do. I assumes all RC wings had flight controllers with gyros doing the same thing but I see plenty of flying wings that don't have flight controllers. Just an esc, motor, receiver and a couple of servos. This is a really interesting video series. I'm learning a lot. Thanks for making them.
Thanks Bruce. Nice overview. I am currently working on a DLG flying wing design and I appreciate the review of the basics! Looking forward to part 2
Great basic explanation again. Love the way you cut through the arrogance of some of the 'experts' who love to complicate the issues to claim their knowledge as sacrosanct!
I had half a second delay between the video and audio and was entertainined no end. thank you Bruce
Another very clear video lecture, I first started watching your videos when you explained the advantage of having a proper inlet cowl around a ducted fan in an earlier video.
Thanks for " Theory of Flight " 101 .....Brings me back quite a few years !!
You surely know how to share knowledge, and make it fun. I hope someday my wife and I can travel to NZ so I can shake your hand.
I understand reflex now!! Thank you Sir Bruce :)
I thought that you were going to draw the Yin/Yang symbol for a moment there Bruce. A truly well balanced wing. Excellent and informative video! Thanks.
I love watching this guy lol... He's so informative and very inspirationally positive and upbeat... Boy am I glad I joined his channel! Thanks Bruce! (Are all Aussies friendly? Damn Ima move there lol- they sure are not here in the states) and I'm heading straight over to patreon to give some well deserved financial support and bonus content this guy definitely deserves it (no in no way am I conoenapsated nor have I ever even heard of Bruce I'm just sincerely pleased finding his channel)
i was just trying to build a flying wing and stumble upon this video this is very good explaintion of lift and like how things are little bit different for flying wing now i have idea how lift is generated on flying wing i hopefully will going to build a really good flying wing..
More videos sir this helped me a lot because due to the pandemic i can't start college and i'm taking aircraft maintenance technology this is very helpful!!! THANKS
Thanks for details explanation Mr Bruce,even you speak very fast but still can catch some clue and information.....youtube have a undertitle here that can help us...thanks and have a great day
'Décalage' is the correct word, it quite simply means 'Offset'. Nice show very lively: Thanks
Great work, very easy to follow - keep it coming!
Use to do 100mph LOS wings. Oscillations were a problem to the point that canopies and batteries would eject at high speed. This was especially true if the wing was a bit flexible. Looking forward to the next video.
Thank you. My old man was designing "flying barn doors" for years. I never knew why his drawings worked.
This principle is what I use on my Control Line Pulse Jets.The wire adds lots of instability for up & down motion so a heavy nose is perhaps the only way to solve it.The down fall is a wing lifting behind the balance point & so it adds drag .Stability sometimes costs speed.The fastest PJs on wire are hardest to fly.Less fun but win races.Most people dont realize the wire has so much drag up & down Any wind lift in front of the wire is no good.But you must have the balance point in front of the wire support point to keep the model square to you.
easy to listen too, simple explanations. Good stuff mate.
Excellent Vid series!!! I will be sure to pass these on to my followers!!!
Thanks for all your great vids over the years!!!
Conservation of mass and the fact that air is an incompressible fluid explains lift quite simply. It works like this. Since the cross section smaller above the wing in order to pass the same mass of fluid (volume) through a smaller area it mus increase in speed. An increase in fluid speeds results in a decrease in pressure for laminar fluid flow and hence the lift.
Great stuff Bruce. Like the way you simplify, even if the purists aren't all on board :-). Two comments, already partly covered by others: you refer to decollage as being the difference between wing and horizontal stab pitch angle, or off-set. I believe the correct French word is decalage, which means off-set. Decollage = take-off.
The stabilising effect in pitch of the conventional tail: speed maybe has a role, but if so the response time is slower as the pressure profile and therefore resultant lift on the tail takes time to develop. The more immediate stabilising effect is the change in alpha the tail is seeing with the speed instantaneously being the same.
Love your channel, mate.
I think washout is very important too. By doing this you are creating something similar to reflex at the tips. Combined with the sweep the stabilising effect is produced at a longer moment arm and therefore you need less deflection and force. You can eliminate reflex near the centre of the wing and also reduce the tip stall tenancy and make it wobble less.
You are presenting the info in a very pleasant manner!
You should explain how flying wings WITHOUT reflex work. Such as a simple paper airplane. If you properly place the CG on a piece of foam board, it will glide without any reflex. When you described the symmetrical airfoil flying wing, you had reflex with a your elevons; but you should also explain how symmetrical airfoil flying wings fly without out reflex in the elevons. (My hint to you is Center of Lift vs Center of Pressure.)
Excellent videos, keep them coming. I suspect you'll be making a video on the Taylor vs FAA case :-)
Also I really like your fixed wing, work bench, and how to videos :-)
wing tip washout .wing sweep.aileron with reverse airfoil like the mitchel wing ultralight.
I read some of the comment critics. A lot of verbiage. Simply as you stated, air flow over a modified teardrop shape, with an attack angle above horizontal, produces lower pressure (partial vacuum) on the top of a wing. Air deflection, due to declining front to rear chord, produces higher pressure on the bottom of a wing. The differential causing lift. Forward velocity due to the application of thrust increases air velocity over the wing.
Very interesting stuff, this helps me to understand the flight behaviour of my plane better and really explained in a super understandable way! 😊
I am already looking forward to the next video.
Thanks Bruce, a really clear explanation. I'm looking forward to the next instalment!
10:00 - it's not that simple. If the nose of the aircraft pitches up, that doesn't necessarily mean that it'll slow down. It'll slow down if the angle of attack rises - and if this is the case, the angle of attack of the horizontal stabilizer will change it's angle of attack too (by exactly the same amount). As the AOA (angle of attack) rises, the stabilizer will first produce no induced lift force, then it'll start to create lift, providing desired momentum on the CG. Speed change isn't the main factor here.
Another thing is, that as the AOA rises the Cp (center of aerodynamic pressure) moves forward on the main wing (especially for cambered airfoils) closer to CG, so the momentum needed to compensate this force is lower than it was when the AOA was lower.
The static longitudinal stability is not always achieved by creating a download on the tail. This is true only for the designs where the CG is placed in front of the Cp of the main wing. Even then, there are situations where the load on the tail is vectored upwards - for example the high angle of attack situation. High angle of attack with unsymmetrical, cambered airfoil, causes the Cp (Center of aerodynamic pressure of the main wing) to move forward - often in front of CG - this way the aircraft wants to rise its nose and we'd like to counteract by applying the positive lift on the tail.
Apart from that, great video.
Cheers!
fascinating explanation of the flying wings and how it works and the physics beyond it .
Well done and to the point! Thank you for the lecture!
THIS is youtube. Sir, I love you video. My plan is to build an fpv-plane in very small. Not done Deltas before and had no idea before. I will watch these videos and see and tell whether it worked :)
Nice explanations thanks. I've understood it better than before.
Very informative Bruce! I've got a wing built from left over wings from an Air Hogs Titan kid's chuck glider. It has quite a bit of rearward sweep in the wings and some reflex has been applied. Its maiden is still awaiting so I have no idea how it will fly. Wingspan is 47' with some Coroplast winglets at the tips. CG works out to be quite rearward because of the swept wings so getting it to balance there and with some extra given to the nose has been a treat! Had to add quite a bit of dead weight even though using a 3S - 2200 battery. Really no science has been applied to it during its construction but hey, it looks good! :) Looking forward to your continuation on this.
Thank you. Very interesting. I was wondering why they never add dimpling to RC aircart to reduce drag? Golf ball get much further distance with the dimples.
Dimples cause tons of turbulence which isn't a problem for a ball but a plane would struggle
Excellent Bruce. Looking forward to next episode.
This is great stuff Bruce. Please don't forget to post Part Two and maybe you could do a Part Three on how I can make a flying wing out of my FAA UAS certificate! [Thanks Mr. Taylor)
Great video, I've been watching your reviews for years, two things, air weight about 1275 g per cubic metre so the force is quite high... also consider Coanda effect, the top of the wing generates lift as well as it moves over the trailing edge.. ( ie water will follow the back of the spoon if held under a smooth water flow under a tap ) .... I've wondered for years as a percentage where is the lift ... Newton ( 80 % ) Coanda (15%) Bernoulli (5%) ... Also wondered where the Reynolds numbers fit into this great subject. :-)
Percentage doesn't make sense, though I can confidently say Coanda has nothing to do with free flow over a single airfoil. Coanda is about fluid jets and is a viscous phenomenon; flow curving around an airfoil is a requirement even for inviscid flow. All of the lift is generated by the pressure distribution and all of the lift is generated but the deflection of air downward; both methods work fine.
Decalage is the angular difference between biplane wings. The difference between wing and stabilizer is longitudinal dihedral. More dihedral, more stability. Less dihedral, less stability and more efficiency
You are the Bob Ross of model flying!!!!
Brilliantly explained Bruce .......
Amazing vidéo Bruce, as usual ! ;) Thanks a lot for all what you do !
I really do wish you would do more of these aerodynamic lessons. Fantastic stuff.
finally the aerodynamics continue
:3
Thanks for the excellent video. It brought the following questions to mind.
1) Don't flying wings need washout (where the angle of attack goes down from the chord to the tip) to be stable, or was that a misplaced datum from hang gliding? This would mean a varying airfoil shape as one looks at it going from the root to the tip. But my HK flying wings appear to have the same airfoil along the span and they don't appear to have any washout.
2) Why don't flying wings typically have dihedral? (because they have ailerons to control the roll axis?)
3) Is there an advantage to separating the elevator from the ailerons on a flying wing? It has been suggested that the motion of a separate elevator surface produces less drag than the elevator motion of the full elevons, but this might be relevant only to gliders.
4) Why do most flying wings have swept-back wings? Not all do, some have a perfectly straight leading edge.
1 - Swept flying wings can use washout to give longitudinal stability, basically the tips (being further back) act like a tail. 'Plank' flying wings dont benefit from washout in the same way. But washout is not mandatory on a flying wing, a reflexed airfoil will give the desired positive pitching moment without washout.
2 - Sweep back has a washout like effect so swept rings generally need less or no dihedral.. and yes you are right, flying wings usually have ailerons so dont need much/any dihedral.
Important to note that the relative airflow that the tail "sees" is coming from a different angle than what the wing "sees", due to the wing's downwash.
For example, when gust pushes nose up and aircraft slows down, wing is producing less downwash and effective angle of attack of tail is reduced, leading to less tail down force.
Hi Bruce - as an avid and often misguided flying wing enthusiast I would just like to point out a couple of things. In the section on drag you did not mention the two types of drag - profile and induced.
Profile drag is from canopies, fuselages, undercarriage and other things sticking out and also skin friction. Induced drag is the drag created from creating lift - more lift more drag.
The point is that a wing can be more efficient i.e.: give greater range for a given fuel consumption than a normal plane because it usually has vastly less profile drag as it has no fuselage or tail. Additionally the reduction in lift you mentioned because of the 'reflex' also lowers the induced drag as the reflexed part does not produce any lift so no induced drag only a small bit of profile drag. So overall, all things being equal, a flying wing should have less drag than an equivalent conventional aircraft. However due to all sorts of factors this is rarely realised in practice and the flying wings produced were never so overwhelmingly superior that they swept the skies of everything else.
The main problem with flying wing in practice and why they sort of withered on the vine is you can't easily add high lift devices to them i.e.: flaps. Because the wing has nothing really to trim changes in pitch, lowering a flap cannot easily be countered with a lifting surface to cope with the pitch change. So generally flying wings can't really use flaps properly and therefore cannot be landed as easily. The flying wing gliders could not use camber control or any of the other tricks modern gliders use to fly so well. Delta flying wings like the Mirage or Concorde used extreme angles of attack on landing to compensate.
And of course they are less stable in yaw because the vertical tails that most of them have do not have enough moment (distance from the wing) to have enough force to affect yaw changes quickly and as I found out to my cost they are very sensitive in pitch and do not like to loaded up to high wing loadings.
I like wings mainly because I am a terrible pilot and a wing has less to break, less to fix and less to throw away when I am done with them :-)
The dictionary says, "décollage...cutting...removing, pieces of an original image," so it's either the narrowness of the fuselage between the wings and tail, or it's the counter-lift applied at the tail to keep the plane from nosing-over in level, flight (highly technical)....
Technically (we learned ca '60's) the CP already behind the CG tends further behind at higher speed... We also learned the underside of a wing is cambered too, to slow the air there thus increasing pressure below....
What you quote is the artistic meaning. The aeronautical meaning is "to take off"...
Excellent video! can't wait for the follow up.
I’ve come across some great videos on circulation theory here on RUclips that I think you’ll quite enjoy. Rather than thinking about Bernoulli and Newton, circulation answers the question and then explains the trailing vortices. Think about why people rough up a cricket ball to get spin, and go from there 👍🏼
Really exellent explanations!
I really learned new stuff to day! Thank you!!
I'm really enlightened. Thanks.
Have to interrupt you to say Decalage is the difference in angle of incidence of the two wings of a biplane. What you are referring to is usually called longitudinal dihedral.
I have made a lot a flying wings and I did not put any reflex in them.. They were 30 to 60 degrees back and the the wing was in a variable constant cord with outsides of the wing at -2 to -3 degrees and pitch up about 15 to 20 degrees. They look a V only with 15 degrees pitch up. They hand flight with the biggest one was made out of 2 slip cardboard sheets and it flew 3 blocks with by hand. It was made in 1973.
Thank's for the lesson !! im not mother language but i understood all about pretty easy for me !!
I Love the whiteboard stuff. Thanks Bruce!
Great video! Hope to see more technical content in the future like this!
Thank you for all the knowledge.... very informative... hope we get more like this
I think some of this is wrong, especially the explanation of the tail plane stabilising pitch.
A flying wing can be made much more efficient if most of the wing has a normal lifting aerofoil while the swept back parts of the wing near the tips has reflex. Relex at the tips of swept back wings have a greater leverage and so greater stability.
...every members dog wants to fly... LOL... love your videos... keep em coming. very interesting and informative
Thank you very much Brus, I really like your white board video series, greetings from Poland. :)
Mr. Bruce : Are you familiar with the stepped wing? The leading 1/3 to 1/2 of the wing being twice the thickness of the rear cord area of the wing, without a sloped transition. A straight vertical step. Theoretically eliminates vortex drag. Apparently increases efficiency when properly proportioned. From what I have read, the design works on flat wings.
pitch up causes angle of attack of tail to increase, which increases lift of tail (i.e., decreasing downward force).
A gift to us all. Thank you
awesome tutorial Bruce! Thanks for feeding my brain!
Nice video. Thanks Bruce.
Thank you Bruce. I have learned a TON from you
Top man, Bruce - interesting as ever!
Thanks for this awesome video. will jump to the 2nd part now
Great video Bruce. I've always wondered why flying wings wag...for example mine.
Another question I have (in addition to forward swept wings you mentioned you would cover in part 2) has to do with semi-circular designs. Are there any benefits of curved wings in regards to flying wings, or is there a good enough reason for keeping most wings with a straight leading and trailing edge? Please cover this in regards to swept-back and swept forward flying wings if you have time. Thank you, and keep up the great informative and educational content!
Hang gliders have reflex to prevent luffing stalls. Also washout is a twist in the wing to prevent tip stalling.
Looking forward to 102.
awesome explaining, thanks!
Very interesting explained in understandable terms. Seems like almost anything will fly with enough power. I hope you can include some explanation of how a wing with only the top airfoil rates in efficiency. That is a wing made from a single layer curved inwards (upwards) on the bottom. Thanks for doing these informative videos. AMA sent a notice that FAA registration is gone, but they said stay tuned ?
This answers so many questions!
Need another VLOG mate. That US man beat the FAA in court and would enjoy your commentary:)
Noted 17:48 : Nothing is Simple in AeroDynamics.
We say "aerodynamic decalage", not "decolage"... Decolage means "to take off" ;-)