My grade 9 draft teacher (yes, before CAD, we had draft classes) worked on the Avro project. And one small correction, the craft used three jet turbines, not one. He actually showed original blue prints of the prototype.
I'm a hovercraft (ground effect vehicle) enthusiast. I've always been mystified as to why the flying platform never succeeded. Thank you for this explanation. Please know that ducted fans are extremely popular among hovercraft designers as horizontal thrust fans. They provide a framework for protective screening that prevents fingers or large objects from contacting the propeller blades as well as the superior performance.
Still doesn't explain why a multi-engine design never arose. Rather than trying to redirect the thrust of the lifting fan, why aren't there additional fans mounted at a 90 degree angle solely to produce forward motion? Seems a rather self-evident solution if rotating the engines proves to be a problem...
@@KuraIthys you are still going to have the unbalance to deal with. The first gyrocopters had the same problem.... would accelerate down the runway until takeoff, then lift up and immediately tip over to upside down because of the difference in lift caused by the difference in air speed between the side of the rotor that was advancing and the side that was retreating. Helicopters solved the problem by changing the pitch of the rotor as it went around using a "swash plate", gyrocopters solved it much simpler by simply allowing the rotor blade to "teeter" back and forth so the advancing blade rises as it moves forward then descends as it retreats on the other side of the craft.
I love the way you communicate information, you give us the facts and examples with a little tongue and cheek fluidly. Always gives me a smile... Cheers
I have just gone back to electronics as a hobby after a 51 year break. I was rather shocked to find that any mention of fans for cooling is almost taboo. I like fans. Heat governs the life of an electronic component. However the fans that are used for PC's, power supples and servers etc. are ducted but have large tip clearances, any thing up to 3mm on a 60mm dia fan. It would cost no more to make this gap 1mm. Maybe they should watch your viseos. Thanks for confirming what I had already guessed, it's just logic. I'm subscribing - great channel
Brilliant.!! Thanks for sharing Bruce, It was so interesting, educational and humorous. I look forward to your findings using the ducts on a quadcopter. Keep up the good work..
Very interesting video Bruce! I think there might be a similar, although less dramatic effect on bare propellers. Not sure what it is, but if you think of the rotating blades as a disc, the rear blades have air being pushed out towards the blade tip whereas the leading edge of the disc gets air angled in towards the root.
One question in parts... what if you are using ducted fans for lift only and a separate thrust device eg small rocket, jet or prop as an example What about a ducted prop for thrust and or a ducted fan for thrust and a ducted fan for lift. I'm only really interested in would it work, and would the complication of mechanical parts an weight make such a system less practical than say a traditional fixed wing set up.
The Bell X22, if I recall correctly, resembled a quad with a tail attached to it. Had 4 tilting ducted fans and operated much like the V22 Osprey does today. It was intended to have V/STOL capability but it was much too finicky. It's a shame only two were ever built though, was a beautiful aircraft.
so much budget spending experimenting with this, but they did recoup some r&d when it was directly applied to VTOL craft. thank you for explaining in excellent detail (without math!) how the deign functioned and why it was a fail :)
It would have been interesting if they had implemented a way to modify parts of the lip. So if the platform was tilting in one direction, then somehow the lop on the opposite side could be changed.
I thought of this too, although in reverse (make the angle/curve of the lip in the direction you are going change to reduce lift on that side). I think that either way the net result is a loss of lift upon changing the shape, creating a need for larger motors. But I sure hope someone is gonna build a drone based on this idea to find out!
I've been thinking about that; but, ultimately I think you would end up reducing your total lift too much. The only solution I can really think of is to change to a different source of lift. So maybe a ducted fan on top of a plane. So you transition to an entirely horizontal flight and use a different lifting surface to maintain altitude.
+Peter Avram Like a helicopter? How about a twin prop, one at the front and one at the back. This would be immune to the effect (as I've explained above) front to back but self stabilizing side to side.
What would happen in an aircraft where you rotate the ducted fan? When it's upgright, it stabilizes the levitation during vertical take-off and landing. And during flight it stabilizes the aircraft in addition to the wings? Or would it fail during the transition?
It sounds like ducts would be best for stable camera quads used in filming. Also, i wonder if one of these could be used with a vertical propeller for movement, kind of like a PPC
Great explanation! Plain and simple aerodynamic lesson that explain why elicopters are and will be much better all round flying crafts that multirotors or any ducted fan configurations...
I think they could have used variable geometry lip to manipulate amount of lift generated on any part of the lip and directing the thrust in that fashion
Thank you very much for this video. This video will be very useful for our model satellite team. If we manage to do it it is basically free stability and thrust.
i paused at 1:37 to say that it seems like the exact problem you get with a jet ski called overstuffing the pump. which can result in bucking and possibly flying off your ski.
Nice presentation Bruce, Thanks heaps! One question though; Did you or anyone ever ty stettin in openable sloths on the duct itself to spoil the effect in the intended direction of travel ?
Hi Bruce, what about if you were to cut out the bottom of the duct thus reducing its effect, but leaving the top and the sides to give some lift, but still gaining something from the lack of vortices' ?
If you wanted to make the thing go forward as well as up, could you not have a trap-door in the side of the duct and open or partially open it to allow some air to thrust it forward?
Like in the previous video, invoking the Bernoulli effect only confuses the issue because it's the vehicle that's moving, not the air. The forward edge of the duct is traveling at the exact same speed as the trailing edge. Since there is no air speed differential between the two surfaces, there can be no Bernoulli effect. But there is a difference in the Coanda effect between the two surfaces. As you point out, it's increased on the leading edge and diminished on the trailing edge. In effect, the trailing edge was stalling because of the steep angle of attack. It was designed to attack in an upward direction, not in a forward direction, so unsurprisingly, it fails to perform well going forward. They could probably make it work by adding a small airfoil above the shroud directing air downward into the trailing half of the duct. An airfoil at that position could be adjusted to have the correct angle of attack and compensate for the loss of the Coanda effect. Of course, with the pilot exposed they don't have many opportunities to reduce drag by creating a slipperier vehicle envelope so the speed is always going to be relatively limited. But they should be able to get it to go as fast as a motorcycle.
I’m interested in using ducted fans for generating thrust (not lift) to propel a hovercraft so they would always be at a fixed pitch (perfectly horizontal parallel to the ground). Would I still benefit from this lip design or better to just go fan in tube like in a swamp boat?
Hey Bruce,I was wondering if you could make a video of your DIY 5.8Ghz 200mW video receiver that's in the same stile as the backpack,tell us how much cheaper and comperabile it is as some not so cheap ones ? Also I was wondering if takeing 3 $2 deversity conrolers could you make a 4 input one that will work like the $25 one that you showed us?
Hi. How would the coanda lip work on a fully forward thrust propeller such as on a paramotor? Would it be stable in the fully forward position, or would it try to flip me onto my back?
Bruce, thanks a lot for your video. It contributed greatly to my understanding of DF Dinamicd. Could you please comment on whether projects on variable coanda lip DF have been completed or are in place?
Can you lower the angle of attack on the rear duct to reduce the amount of lift lost? or take the back on off completely and add something else which either negates or complements the lift on the front?
why they did not add pusher propeller? the platform is horizontal (maximum utilization effectiveness of ducted propeller) and pusher propeller gives speed?
Tell me this. In the design of a photographic stable platform like a surveying style multirotor (slow, stable, steady photos) wouldn't it be beneficial to have the extra stability of the lip?
Hi Bruce interesting I always wonder how they did this with such a high center of Gravity to make this work for the pilot to be on top. What are your thoughts on the Williams X-Jet did they use Gyros for this one or is it the same effect like the platform you are talking about.? cheers for making a video on this
Been watching vids of a quadcopter working quite well on its test flight, using EDFs. They are working in the usual manner for a quad, not swiveling or anything. How is this the case? Is an EDF pulling so much air that the flow from front to back (in the direction of flight) over the lip of the duct is insignificant by comparison?
I wonder if changing the shape of the lip would change its stability at all. For example, straightening out the lip on one side of the fan would eliminate its lift, causing the fan to tip toward that side.
I'm wondering why no-one has done leading-edge slats/slots/flaps ( or similar) on a duct as a method of reducing the efficiency of the leading-edge as compared to the trailing edge, so that this problem goes away.... seems like a relatively simple approach, and would be mechanically trivial if done right.
I was wondering the same thing. The problem with changing the shape of the duct lip would be that the effect depends on the air speed. The wing form would have to continually change during acceleration and retardation. That would have been a major problem in the 50ies. No problem today when
David Buzz The main problem would be that whatever you do there, you lose lift and you need that to stay in the air. Add to that the fact that it would be mechanically complicated to mount something moving on the circular lip (if it does more that just move up and down, the flaps would need to be able to change in diameter). All of this adds weight, while you already have reduced lift. So you would need a more powerful motor, makes everything heavier (again).
David Buzz I wonder now if the ducted fan's stability in regards to forward movement in air would be compromised if you were to add a thrust motor such as used on a gravity based Hovercraft?
I wonder if you had some type of "turkey feather" controls around the lip of the duct where the lip on the low pressure side would be lowered by some type of servo/control rod setup and cancel out the effect to allow it to go faster or would it cancel the vertical lift altogether? Just a thought...
Can you talk about differences between thrust stand tests and dynamic thrust tests (testing angle of incidence and efficiency) when air is moving past it in operating conditions for quadcopters? People judge a lot on static thrusts stands but certain props dont show the same comparable thrust while flying on a quad. Love your stuff
So now I am curious what the effect with be of having small aerofoils at the outside of the propeller vanes which would surely reduce the turbulence? Is that the reason some airliners have them ?
Cool discretion but I bet it would actually work just fine depending on how sturdy the duct is. The effect would be more of a twist for the arm to resist rather than a force on the craft. Also, if it is a real problem maybe just gradually reduce the lip a little on the front end of the craft. Could still improve efficiency. Lastly, since phantoms usually just hover anyways, wouldn't this make sense for that craft? Putting crash resistance aside.
So....if those parts of the problem that cause the additional Coanda effect of the duct fan are wings rather than fixed parts, can the ducted fans be used for drones?
Have you done a video where you evaluated a multicopter with motor dihedral? I would like to hear your thoughts on motor dihedral and how it affects stability for slow moving camera platforms. (not fast racing miniquads).
Great video! Very educational and easy to understand. Question. What are the effects of a double rotor stack with each rotor turning in opposite directions? With the duct and with out. Thanks!
Very interesting as usual Bruce :) But what if you want the upside of ducted fan, that is reduced turbulence and safety but skip the lip and have a straight edge? You would get less lift then with a lip but you would have less effect of this coanda effect problem you are describing?
Maybe an odd question... If I were to put a grate of sorts over the fan, so air can only move up or down, would that increase lift? I mean, since it keeps air from rotating along with the fan, the difference in airspeed over and under the fan would be even greater in my over simplified reasoning...
If you stick a cone in the back of your thrust tube would it go faster? If you had 2 thrust tubes with a reduction of 15ish%, one 6 inches long and one 3 feet long would there be a difference in thrust horsepower, trust speed, and amp draw?
"I'm so bad at drawing, I can't even draw the curtains on a cold night".
My grade 9 draft teacher (yes, before CAD, we had draft classes) worked on the Avro project. And one small correction, the craft used three jet turbines, not one. He actually showed original blue prints of the prototype.
Too cool. A Canadian low point that was, F you Diefendumbass. We presently have another PM just like that idiot.
I'm a hovercraft (ground effect vehicle) enthusiast. I've always been mystified as to why the flying platform never succeeded. Thank you for this explanation.
Please know that ducted fans are extremely popular among hovercraft designers as horizontal thrust fans. They provide a framework for protective screening that prevents fingers or large objects from contacting the propeller blades as well as the superior performance.
Still doesn't explain why a multi-engine design never arose.
Rather than trying to redirect the thrust of the lifting fan, why aren't there additional fans mounted at a 90 degree angle solely to produce forward motion?
Seems a rather self-evident solution if rotating the engines proves to be a problem...
@@KuraIthys you are still going to have the unbalance to deal with. The first gyrocopters had the same problem.... would accelerate down the runway until takeoff, then lift up and immediately tip over to upside down because of the difference in lift caused by the difference in air speed between the side of the rotor that was advancing and the side that was retreating. Helicopters solved the problem by changing the pitch of the rotor as it went around using a "swash plate", gyrocopters solved it much simpler by simply allowing the rotor blade to "teeter" back and forth so the advancing blade rises as it moves forward then descends as it retreats on the other side of the craft.
I love the way you communicate information, you give us the facts and examples with a little tongue and cheek fluidly.
Always gives me a smile... Cheers
Thanks for your videos. I appreciate your effort in making them. They are well planned and thought out for easy understanding.
I have just gone back to electronics as a hobby after a 51 year break. I was rather shocked to find that any mention of fans for cooling is almost taboo. I like fans. Heat governs the life of an electronic component. However the fans that are used for PC's, power supples and servers etc. are ducted but have large tip clearances, any thing up to 3mm on a 60mm dia fan. It would cost no more to make this gap 1mm. Maybe they should watch your viseos. Thanks for confirming what I had already guessed, it's just logic. I'm subscribing - great channel
Love your presentations and your personality. You make such complicated subjects so easy to understand.
Have you done the test of ducted prop thrust vs non ducted prop thrust...very interested in the results.
Bruce, Did you ever record a video of the thrust stand performance of a ducted vs. unducted propeller?
if you are still interested there is a German bloke that did exactly this
@@ferrarikingdom who is he ? Links? IT seems this man did not do it.
@@davemwangi05 ruclips.net/video/hPUVrRqhyMk/видео.html
this guy tried, but didn't get it yet
ruclips.net/video/QccRbsZVg1Y/видео.html
Perfect. I wanted to make a floating sign that didn't move very fast... Sounds like the self stabling is exactly what I need.
Brilliant.!! Thanks for sharing Bruce, It was so interesting, educational and humorous. I look forward to your findings using the ducts on a quadcopter. Keep up the good work..
This is the 4th video of yours I've watched. I LOVE finding great new teachers with YEARS of content just waiting for me :)
Excellent video and explanation.
Great job of explaining a complex system in a simple manner. Your graphics are good! Thanks!
Thank you for sharing your knowledge Bruce!
Thank you so much for those videos and for the time and effort put into them.
Great video Bruce :) Whiteboard videos are awesome and 100X better than school and more informative!
I really appreciate your knowledge and the clear way you share it.
Thanks for taking the time to do this Bruce. Really interesting.
Very interesting video Bruce! I think there might be a similar, although less dramatic effect on bare propellers. Not sure what it is, but if you think of the rotating blades as a disc, the rear blades have air being pushed out towards the blade tip whereas the leading edge of the disc gets air angled in towards the root.
I wonder what would happen if you could vary sections of the lips, profile
that's a basically how a helicopter works
I was thinking of a bunch interconnected metal flaps like the nozzle of a jet engine, but independently controlled
actually I was thinking that maybe have a sort of mesh that slide modified the shape of that round bevel at the rim
Maybe an even riskier design where it would "stall" the coanda effect by protruding flaps to block airflow on one side of the lip.
Absolutely fascinating...Thank you again.
Love your videos Bruce. Thanks for explaining things in such an easy to understand way.
Super awesome! Thank you and Best regards from Bavaria!
I guess it shows I'm not the youngest to admit I like your whiteboard videos the most. Thanks for the explanation, Bruce.
5:44 "it was too stable"
holy Zephyr
One question in parts...
what if you are using ducted fans for lift only and a separate thrust device eg small rocket, jet or prop as an example
What about a ducted prop for thrust
and or a ducted fan for thrust and a ducted fan for lift.
I'm only really interested in would it work, and would the complication of mechanical parts an weight make such a system less practical than say a traditional fixed wing set up.
Nicely explained, thanks Bruce.
The Bell X22, if I recall correctly, resembled a quad with a tail attached to it. Had 4 tilting ducted fans and operated much like the V22 Osprey does today. It was intended to have V/STOL capability but it was much too finicky. It's a shame only two were ever built though, was a beautiful aircraft.
so much budget spending experimenting with this, but they did recoup some r&d when it was directly applied to VTOL craft.
thank you for explaining in excellent detail (without math!) how the deign functioned and why it was a fail :)
It would have been interesting if they had implemented a way to modify parts of the lip. So if the platform was tilting in one direction, then somehow the lop on the opposite side could be changed.
I thought of this too, although in reverse (make the angle/curve of the lip in the direction you are going change to reduce lift on that side). I think that either way the net result is a loss of lift upon changing the shape, creating a need for larger motors. But I sure hope someone is gonna build a drone based on this idea to find out!
That's what I was about to say :D
I've been thinking about that; but, ultimately I think you would end up reducing your total lift too much. The only solution I can really think of is to change to a different source of lift. So maybe a ducted fan on top of a plane. So you transition to an entirely horizontal flight and use a different lifting surface to maintain altitude.
A quad with ducted props should be immune to the effect, as I explained above.
+Peter Avram Like a helicopter? How about a twin prop, one at the front and one at the back. This would be immune to the effect (as I've explained above) front to back but self stabilizing side to side.
What would happen in an aircraft where you rotate the ducted fan? When it's upgright, it stabilizes the levitation during vertical take-off and landing. And during flight it stabilizes the aircraft in addition to the wings? Or would it fail during the transition?
Excellent explanation of these effects on movement on ducted systems. Well done sir.
Thanks for the video! It was very instructional and entertaining.
It sounds like ducts would be best for stable camera quads used in filming.
Also, i wonder if one of these could be used with a vertical propeller for movement, kind of like a PPC
***** This is what I was thinking...
***** Probably not, airflow is still across duct in one direction tilted or not.
*****
Bruce, do you have an email? I'm going to buy my first quadcopter parts from online, I'd like to run my budget and the list by you. Owen
owenkilleen I'm not bruce, nor do i care
***** you tube won't let me post a comment straight in my own comment field. David
A good explaiination how ducts work. Thanks for posting!!
Great explanation! Plain and simple aerodynamic lesson that explain why elicopters are and will be much better all round flying crafts that multirotors or any ducted fan configurations...
I think they could have used variable geometry lip to manipulate amount of lift generated on any part of the lip and directing the thrust in that fashion
Thank you very much for this video. This video will be very useful for our model satellite team. If we manage to do it it is basically free stability and thrust.
Thanks for the very helpful explanation!
very informative and easily explained. keep up the good work bruce... just love your videos...
Very interesting. Thank you Bruce.
Very important information! Thank you!
i paused at 1:37 to say that it seems like the exact problem you get with a jet ski called overstuffing the pump. which can result in bucking and possibly flying off your ski.
I'd love to see a sort of "drone trailer" that used one of these ducts and is simply a pull-behind for a quad that provides a huge battery bank.
Nice presentation Bruce, Thanks heaps! One question though; Did you or anyone ever ty stettin in openable sloths on the duct itself to spoil the effect in the intended direction of travel ?
What if you had a partially ducted fan? Only have the ducts on the side, for example, leaving forwards and backwards flight unaffected.
Thanks for clearing that up! :)
Very interesting bruce,i cant wait to see your video of them in use,i do enjoy your channel
Does moving the prop up or down in the duct make a difference?
This is awesome yet simple information. Thanks
Thank you so much for the video. I think Mr Tesla figured this out. Let me get back to you on how to make it work.
Very, very informative video. Thanks for the great work!!!
Awesome explation 👌 thxxx mutch 🍀 and lovely greetings from Germany 😘
Thanks Bruce. I am so curious to see how your ducts work out. Especially on a miniquad
Another very informative video, Bruce.
Excellent video my friend!
Hi Bruce, what about if you were to cut out the bottom of the duct thus reducing its effect, but leaving the top and the sides to give some lift, but still gaining something from the lack of vortices' ?
If you wanted to make the thing go forward as well as up, could you not have a trap-door in the side of the duct and open or partially open it to allow some air to thrust it forward?
Great explanation Bruce. Would the Hiller flying platform or a quad be better if you coupled it with a pusher prop?
Like in the previous video, invoking the Bernoulli effect only confuses the issue because it's the vehicle that's moving, not the air. The forward edge of the duct is traveling at the exact same speed as the trailing edge. Since there is no air speed differential between the two surfaces, there can be no Bernoulli effect.
But there is a difference in the Coanda effect between the two surfaces. As you point out, it's increased on the leading edge and diminished on the trailing edge. In effect, the trailing edge was stalling because of the steep angle of attack. It was designed to attack in an upward direction, not in a forward direction, so unsurprisingly, it fails to perform well going forward.
They could probably make it work by adding a small airfoil above the shroud directing air downward into the trailing half of the duct. An airfoil at that position could be adjusted to have the correct angle of attack and compensate for the loss of the Coanda effect. Of course, with the pilot exposed they don't have many opportunities to reduce drag by creating a slipperier vehicle envelope so the speed is always going to be relatively limited. But they should be able to get it to go as fast as a motorcycle.
Another great video. I can se this used on larger slow flying video quads.
You're awesome. Even better than the Discovery chanel. Hope there will be a second video about the antennas.
what about another set of ducted props to provide the needed forward thrust.
I’m interested in using ducted fans for generating thrust (not lift) to propel a hovercraft so they would always be at a fixed pitch (perfectly horizontal parallel to the ground). Would I still benefit from this lip design or better to just go fan in tube like in a swamp boat?
Hey Bruce,I was wondering if you could make a video of your DIY 5.8Ghz 200mW video receiver that's in the same stile as the backpack,tell us how much cheaper and comperabile it is as some not so cheap ones ? Also I was wondering if takeing 3 $2 deversity conrolers could you make a 4 input one that will work like the $25 one that you showed us?
Hi. How would the coanda lip work on a fully forward thrust propeller such as on a paramotor? Would it be stable in the fully forward position, or would it try to flip me onto my back?
Rally interesting and inspiring. Thank you! More of the same please!
Bruce, thanks a lot for your video. It contributed greatly to my understanding of DF Dinamicd. Could you please comment on whether projects on variable coanda lip DF have been completed or are in place?
Nice bit of info and also history stuff =D
Cheers Bruce!
Can you lower the angle of attack on the rear duct to reduce the amount of lift lost? or take the back on off completely and add something else which either negates or complements the lift on the front?
why they did not add pusher propeller? the platform is horizontal (maximum utilization effectiveness of ducted propeller) and pusher propeller gives speed?
would not work as the air will still rush past the duct perpendicular... even worse than the duct is angled...
Thanks for that, Bruce!
Thanks a lot for that Bruce, very interesting.
Thank you for explaining that. As a young boy I bought a flying model called the flying platform
Tell me this. In the design of a photographic stable platform like a surveying style multirotor (slow, stable, steady photos) wouldn't it be beneficial to have the extra stability of the lip?
Hi Bruce interesting I always wonder how they did this with such a high center of Gravity to make this work for the pilot to be on top. What are your thoughts on the Williams X-Jet did they use Gyros for this one or is it the same effect like the platform you are talking about.? cheers for making a video on this
Been watching vids of a quadcopter working quite well on its test flight, using EDFs. They are working in the usual manner for a quad, not swiveling or anything. How is this the case? Is an EDF pulling so much air that the flow from front to back (in the direction of flight) over the lip of the duct is insignificant by comparison?
Hello. Does it make sense to add one propeller perpendicular to the ones that push up ? Will the model go forward while staying flat ?
I wonder if changing the shape of the lip would change its stability at all. For example, straightening out the lip on one side of the fan would eliminate its lift, causing the fan to tip toward that side.
Thanks a lot, Bruce!
I'm wondering why no-one has done leading-edge slats/slots/flaps ( or similar) on a duct as a method of reducing the efficiency of the leading-edge as compared to the trailing edge, so that this problem goes away.... seems like a relatively simple approach, and would be mechanically trivial if done right.
I was wondering the same thing. The problem with changing the shape of the duct lip would be that the effect depends on the air speed. The wing form would have to continually change during acceleration and retardation. That would have been a major problem in the 50ies. No problem today when
David Buzz
The main problem would be that whatever you do there, you lose lift and you need that to stay in the air. Add to that the fact that it would be mechanically complicated to mount something moving on the circular lip (if it does more that just move up and down, the flaps would need to be able to change in diameter). All of this adds weight, while you already have reduced lift. So you would need a more powerful motor, makes everything heavier (again).
David Buzz you mean like this?
David Buzz I wonder now if the ducted fan's stability in regards to forward movement in air would be compromised if you were to add a thrust motor such as used on a gravity based Hovercraft?
16 mph is four times walking pace.
Also, it is able to fly in a straight line whereas a ground vehicle needs to follow the roads.
John Morley costs a lot more fuel than a land-based vehicle though
Would the Martin jet pack experience the same issues with stabilisation since it doesn't have the overturned lip? i.e. no area to push up against
I wonder if you had some type of "turkey feather" controls around the lip of the duct where the lip on the low pressure side would be lowered by some type of servo/control rod setup and cancel out the effect to allow it to go faster or would it cancel the vertical lift altogether? Just a thought...
Can you talk about differences between thrust stand tests and dynamic thrust tests (testing angle of incidence and efficiency) when air is moving past it in operating conditions for quadcopters? People judge a lot on static thrusts stands but certain props dont show the same comparable thrust while flying on a quad. Love your stuff
So now I am curious what the effect with be of having small aerofoils at the outside of the propeller vanes which would surely reduce the turbulence? Is that the reason some airliners have them ?
Cool discretion but I bet it would actually work just fine depending on how sturdy the duct is. The effect would be more of a twist for the arm to resist rather than a force on the craft. Also, if it is a real problem maybe just gradually reduce the lip a little on the front end of the craft. Could still improve efficiency. Lastly, since phantoms usually just hover anyways, wouldn't this make sense for that craft? Putting crash resistance aside.
So....if those parts of the problem that cause the additional Coanda effect of the duct fan are wings rather than fixed parts, can the ducted fans be used for drones?
Have you done a video where you evaluated a multicopter with motor dihedral? I would like to hear your thoughts on motor dihedral and how it affects stability for slow moving camera platforms. (not fast racing miniquads).
Great video! Very educational and easy to understand.
Question.
What are the effects of a double rotor stack with each rotor turning in opposite directions?
With the duct and with out. Thanks!
Thanks for posting this interesting video.
Very interesting as usual Bruce :) But what if you want the upside of ducted fan, that is reduced turbulence and safety but skip the lip and have a straight edge? You would get less lift then with a lip but you would have less effect of this coanda effect problem you are describing?
I'm thinking maybe rotating the 'input airfoil' might have improved this.
Anyway, just a thought.
great info thanks Bruce!
Great video. Does the Parrot AR Drone count ?
Maybe an odd question... If I were to put a grate of sorts over the fan, so air can only move up or down, would that increase lift? I mean, since it keeps air from rotating along with the fan, the difference in airspeed over and under the fan would be even greater in my over simplified reasoning...
Thanks for the explanation.
Very interesting video. Thanks Bruce keep them coming. ps how did you crack the left lens in your glasses?
If you stick a cone in the back of your thrust tube would it go faster? If you had 2 thrust tubes with a reduction of 15ish%, one 6 inches long and one 3 feet long would there be a difference in thrust horsepower, trust speed, and amp draw?