Is Tacking A Viable Solution To An Overpowering Headwind?

[scro]

Here's a question for both sides of the debate:

In still air, and if the MM's speed over ground was not capped, in which direction could the drone achieve the fastest speed (over ground)? (eg, forwards, diagonally forwards, sideways, backwards etc.)

Assume there are no issues with the drone like bent props, weaker motors.

I've taken some crude photos of the MM for visual reference of surface area when tilted. I should have been more scientific and had the angle of the camera relative to drone set to show a 30 deg tilt, and kept the scale exactly the same.


I am fully in agreement that tacking (zigzagging) into the wind will never make more progress upwind than simply flying directly into the wind (@sar104 and @Meta4 's point). However it's not quite so clear what orientation to have the drone in to minimise its drag (kind-of @fpvaddict 's point, if I've understood right?)

Th MM seems to cap its SOG to max 13m/s so I'm not sure how some valid tests could be done? Perhaps some insight could be gained from motor speeds after doing a few runs along a set path with the drone body in various headings?

It "might" just have least drag when flying backwards!!??

 

[RogerDH]

I’m flabbergasted by your comment that “this has nothing to do with drag”. Absolutely amazing. I didn’t say much more for a reason. If you can’t see the issue in that comment it’s not worth discussing

Looking at the Mini from two orientations in the attached pic, I'm having a hard time understanding your premise that the orientation on the right has less wind drag, but we really don't need to resolve that. As sar104 said, even if that were true, "the optimal solution is always a course directly towards the target at maximum airspeed." That is why it's irrelevant.

 

[Meta4]

In still air, and if the MM's speed over ground was not capped, in which direction could the drone achieve the fastest speed (over ground)? (eg, forwards, diagonally forwards, sideways, backwards etc.)
However it's not quite so clear what orientation to have the drone in to minimise its drag

It makes no difference.
Any difference is trivial and not significant.

 

[Deleted member 114292]

The reason why drag is unimportant in this case is because and, of course I am re-stating what we’ve already said, the aircraft feels no wind meaning it is not subjected to the force of the wind but rather is in a body of air moving with the wind.

 

[scro]

The reason why drag is unimportant in this case is because and, of course I am re-stating what we’ve already said, the aircraft feels no wind meaning it is not subjected to the force of the wind but rather is in a body of air moving with the wind.

I thought the thread started off about trying to make headway into wind? Surely this means not drifting downwind at the same speed as the wind, and hence surely this means moving relative to the surrounding air so drag cannot be discounted on that basis.

There's another very different reason why drag could potentially be discounted, though. I'm currently mulling it over in my head to make sure I'm not just spouting nonsense before putting them into text on here.

 

[Deleted member 114292]

Have you ever seen a hot air balloon and wondered how come if a wind whips up the balloon just doesn’t collapse and fall to the ground?

Because for the balloon there is no wind it’s moving in the body of air and there is no perception of wind.

so what I’m trying to say is that the aircraft is not subjected to any more drag due to the wind but only Subjected to the drag due to its forward motion.

 

[sar104]

Lol! How can I do the math when there aren’t any numbers? I am not going to pretend to know best- regardless of my career and education- like everyone else has. Propulsion by the props are held at a constant in either situation. Whether you are moving forwards, backward or sideways, the output by the props will be the same. The only variables in the hypothetical that can be altered is ground speed and resistance. That’s it! Reducing resistance by minimizing profile of the craft- is the only solution to increase ground speed (without flying with the wind). Whether or not exposed surface area is reduced enough to sufficiently reduce drag that overcomes max output of the motors is the question. No one here knows the answer to that because no one here has the data necessary, myself included

I’m flabbergasted by your comment that “this has nothing to do with drag”. Absolutely amazing. I didn’t say much more for a reason. If you can’t see the issue in that comment it’s not worth discussing

No numbers eh - how silly of me. I presented you with a simple mathematical proof, and you complain there are no numbers in it? Sorry - that's what physicists and engineers (including aeronautical engineers) do - they replace numbers with variables and constants and solve the resulting equations. It doesn't need numbers - that's the entire point of reducing a problem to its governing equations.

So faced with my digital version of the traditional back-of-the-envelope proof, you don't even understand it enough to make a single comment or attempt to dispute it? A JPL aeronautical engineer who doesn't understand the most basic vector arithmetic? I don't think so.

 

[sar104]

Here's a question for both sides of the debate:

In still air, and if the MM's speed over ground was not capped, in which direction could the drone achieve the fastest speed (over ground)? (eg, forwards, diagonally forwards, sideways, backwards etc.)

Assume there are no issues with the drone like bent props, weaker motors.

I've taken some crude photos of the MM for visual reference of surface area when tilted. I should have been more scientific and had the angle of the camera relative to drone set to show a 30 deg tilt, and kept the scale exactly the same.
View attachment 100451

I am fully in agreement that tacking (zigzagging) into the wind will never make more progress upwind than simply flying directly into the wind (@sar104 and @Meta4 's point). However it's not quite so clear what orientation to have the drone in to minimise its drag (kind-of @fpvaddict 's point, if I've understood right?)

Th MM seems to cap its SOG to max 13m/s so I'm not sure how some valid tests could be done? Perhaps some insight could be gained from motor speeds after doing a few runs along a set path with the drone body in various headings?

It "might" just have least drag when flying backwards!!??

It's not a debate. It's yet another random poster touting obviously bogus credentials and trying to obfuscate the problem for whatever reason by yapping about drag. Drag is irrelevant to the problem. Drag is one parameter that determines maximum airspeed, but maximum airspeed is not a variable in this problem, by definition. The aircraft has a maximum airspeed - that is a given. The question is in which direction to use that maximum airspeed in order to make progress into a headwind towards a target. And the answer, which is trivially obvious and easy to prove somewhat formally as I did above, is to fly a course directly towards the target. Anything else results in slower progress towards that target. And if the windspeed exceeds the maximum airspeed, progress towards an upwind target is always negative, on any course.

Now the question of whether maximum airspeed varies with aircraft orientation is a different, and potentially relevant one, as I mentioned above. If it were, for example, capable of higher airspeed flying backwards, or sideways, then its maximum airspeed would be at that orientation and so it would be best to fly in that orientation (backwards or sideways as appropriate) - but still directly towards the target - not zig-zagging. In fact, aside from the Mavic Mini with defective rear props, the Mavics and Phantoms achieve similar airspeeds in all orientations, so even that point is moot.

 

[scro]

Have you ever seen a hot air balloon and wondered how come if a wind whips up the balloon just doesn’t collapse and fall to the ground?

Because for the balloon there is no wind it’s moving in the body of air and there is no perception of wind.

so what I’m trying to say is that the aircraft is not subjected to any more drag due to the wind but only Subjected to the drag due to its forward motion.

I think, ultimately we're in agreement. The presence or lack of wind doesn't specifically change the drag force. The drone's speed relative to the surrounding air (or we could call it "wind") DOES influence drag force. If the drone drifts with the wind there's no drag force. That's the same as hovering over a spot, in still air. If the drone tries to hold position relative to the ground and there is some wind, it has to fight against that wind, and hence experiences a drag force due to there being relative movement between the drone and the surrounding air.

A hot air balloon DRIFTS with the wind, so if you're sitting in the balloon basket you don't feel any wind, as you say, and hence no drag force.

 

[scro]

@sar104 Totally in agreement Tacking is pointless for making progress against a headwind, and drag does not affect this.

Diverging slightly from the original post's topic, and looking at what direction the MM achieves maximum airspeed...

I believe the MM has 2 key things that limit maximum airspeed. I welcome any better knowledge:

1. A cap on speed-over-ground (not airspeed) of 13m/s. It doesn't appear to fly faster than this, even when being pushed along with a strong breeze. In still air that's it's maximum airspeed.
2. Maximum tilt of 30deg, which limits the maximum horizontal thrust available to overcome drag.

It's interesting to hear that other drones achieve similar airspeeds in all directions. This implies that drag doesn't vary much relative to the direction from which air is coming at it. I re-did a set of photos looking at the drone from various angles with a simulated pitch of 30deg. It is not immediately obvious which angle presents the least area for drag. Side-on the body presents a larger area, but the arms present a smaller area.

When flying forwards the rear props appear to be partially in the "shadow" of the front props. Might this have a more significant effect than drag?

 

[sar104]

@sar104 Totally in agreement Tacking is pointless for making progress against a headwind, and drag does not affect this.

Diverging slightly from the original post's topic, and looking at what direction the MM achieves maximum airspeed...

I believe the MM has 2 key things that limit maximum airspeed. I welcome any better knowledge:

1. A cap on speed-over-ground (not airspeed) of 13m/s. It doesn't appear to fly faster than this, even when being pushed along with a strong breeze. In still air that's it's maximum airspeed.
2. Maximum tilt of 30deg, which limits the maximum horizontal thrust available to overcome drag.

It's interesting to hear that other drones achieve similar airspeeds in all directions. This implies that drag doesn't vary much relative to the direction from which air is coming at it. I re-did a set of photos looking at the drone from various angles with a simulated pitch of 30deg. It is not immediately obvious which angle presents the least area for drag. Side-on the body presents a larger area, but the arms present a smaller area.View attachment 100473

When flying forwards the rear props appear to be partially in the "shadow" of the front props. Might this have a more significant effect than drag?

In the simplest analysis for an object that resembles a box, drag scales with cross-sectional area. The Mavics all present the lowest cross-sectional area on the x-axis, highest on the z-axis, intermediate on the y-axis. So flying forwards or backwards will have the lowest drag, although the difference relative to sideways is reduced as tilt increases and the z-axis comes into play equally for both orientations.

Prop efficiency is a different issue but that simply determines how much motor thrust is required to achieve any given tilt, rather than the airspeed achieved at that tilt. The recent test results that I posted for the Mini showed that relative to forwards or backwards, slightly more tilt is required for equivalent velocity sideways.

 

[fpvaddict]

If the maths in the last few posts is too complicated, post #27 has distilled it down to its simplest form.

No numbers eh - how silly of me. I presented you with a simple mathematical proof, and you complain there are no numbers in it? Sorry - that's what physicists and engineers (including aeronautical engineers) do - they replace numbers with variables and constants and solve the resulting equations. It doesn't need numbers - that's the entire point of reducing a problem to its governing equations.

So faced with my digital version of the traditional back-of-the-envelope proof, you don't even understand it enough to make a single comment or attempt to dispute it? A JPL aeronautical engineer who doesn't understand the most basic vector arithmetic? I don't think so.

You're simply wrong. I do not know the MMs Cd, density, exposed surface area, velocity at max pitch, nor all of the information to even begin determining the Cd of the drone, you want me to replace that data with variables? You clearly haven't a clue in the world what you are talking about. I saw your snide remark towards the other commenter "he isn't". Is this how newcomers are usually treated, or arguments handled? I see plenty of people using personal experience with the drone to explain how this has worked for them, only to met with skepticism and told repeatedly that it has been proven false when it has not. Clearly I am in the wrong forum, I didn't realize this one would be full of bullheaded teenagers bickering to make a point. Where are the admins??

The one who doesn't believe drag plays a factor in combatting wind resistance is telling me I need to replace it with "variables and constants to solve the resulting equations" ...Someone take this boy back to highschool physics class please. Maybe thats what you learned in your intro to Physics course but that is not how it works in the real world. You can't take a variable give it a number, throw it into an equation with some constants and expect specificity in the result. "replace numbers with variables and constants" LOL. My wife is going to get a kick out of this

 

[scro]

Perhaps read the 1st post again. It asks if zig-zagging diagonally across the wind flow would help to make headway against that wind. This question has comprehensively been answered, along with the theory and principles behind that answer. The best way to make headway against a headwind is to fly directly into it. Do this by flying backwards or sideways if you must, but make sure the direction the drone moves (not necessarily the direction the nose of the drone is pointing) is directly into the wind.

In the video in post #62 the drone has been modified by having a camera strapped to its top, and provides a big red herring. To quote the video's author it acts "like a sail". The additional camera changes which direction to point the nose of the drone for optimal progress against the wind, but doesn't change the optimal direction for the drone to move in for optimal progress.

 

[Meta4]

I see plenty of people using personal experience with the drone to explain how this has worked for them, only to met with skepticism and told repeatedly that it has been proven false when it has not.

It's very common in drone forums to see misinformation and misunderstanding.
In response to posts regarding flight incidents, there are usually members making uninformed and confused guesses.
But there are a few members that do understand the physics and some who read recorded flight data to see what actually happens.

Someone take this boy back to highschool physics class please. Maybe thats what you learned in your intro to Physics course but that is not how it works in the real world.

If only you knew ....

btw ...I'm still waiting to hear how a real aeronautical engineer interprets post #27.

 

[sar104]

You're simply wrong. I do not know the MMs Cd, density, exposed surface area, velocity at max pitch, nor all of the information to even begin determining the Cd of the drone, you want me to replace that data with variables? You clearly haven't a clue in the world what you are talking about. I saw your snide remark towards the other commenter "he isn't". Is this how newcomers are usually treated, or arguments handled? I see plenty of people using personal experience with the drone to explain how this has worked for them, only to met with skepticism and told repeatedly that it has been proven false when it has not. Clearly I am in the wrong forum, I didn't realize this one would be full of bullheaded teenagers bickering to make a point. Where are the admins??

The one who doesn't believe drag plays a factor in combatting wind resistance is telling me I need to replace it with "variables and constants to solve the resulting equations" ...Someone take this boy back to highschool physics class please. Maybe thats what you learned in your intro to Physics course but that is not how it works in the real world. You can't take a variable give it a number, throw it into an equation with some constants and expect specificity in the result. "replace numbers with variables and constants" LOL. My wife is going to get a kick out of this

Seriously - you come marching into this thread, spouting pure nonsense and refusing to engage in any kind of technical discussion, and you wonder why I doubt that you have a technical or scientific qualification to your name? Your arguments to date have comprised "appeal to authority", "but a guy on YouTube said so" and "you are wrong because you didn't use any numbers". That's just pathetic. You had an opportunity to rebut my technical argument but instead you chose to be "flabbergasted" - apparently because you cannot understand why the drag coefficient affects maximum airspeed but not optimal course and are too lazy or ignorant to read the proof. You didn't address a single point of it, but you are offended at not being taken seriously? And you don't think that solving basic equations is how it works "in the real world"? If so, then you are really clueless, and trying to convince everyone that you are arguing with "bullheaded teenagers" as an excuse not to have to make sense isn't going to help either.

So yes - you are clearly in the wrong forum because you are way out of your depth in a very shallow subject.

 

[scro]

Time for me to leave this thread. OP's question has been considered, debated, and comprehensively answered, along with a few parallel topics. Thanks to those who've contributed sensible, reasoned responses to try and educate others and go some way to reduce the misinformation that is all-too-common.

I'm off out to fly

 

[fpvaddict]

Seriously - you come marching into this thread, spouting pure nonsense and refusing to engage in any kind of technical discussion, and you wonder why I doubt that you have a technical or scientific qualification to your name? Your arguments to date have comprised "appeal to authority", "but a guy on YouTube said so" and "you are wrong because you didn't use any numbers". That's just pathetic. You had an opportunity to rebut my technical argument but instead you chose to be "flabbergasted" - apparently because you cannot understand why the drag coefficient affects maximum airspeed but not optimal course and are too lazy or ignorant to read the proof. You didn't address a single point of it, but you are offended at not being taken seriously? And you don't think that solving basic equations is how it works "in the real world"? If so, then you are really clueless, and trying to convince everyone that you are arguing with "bullheaded teenagers" as an excuse not to have to make sense isn't going to help either.

So yes - you are clearly in the wrong forum because you are way out of your depth in a very shallow subject.

I came marching in spouting nonsense and refuse to engage in technical discussion... ok . You pretend to offer technical discussion but demonstrate a pretty mediocre understanding of the physics you attempted to explain. How can we debate technicals while ignoring fundamentals? Dunning-Kruger is in effect.

You or someone else posted "math" that doesn't take into account the specifics or properties of the craft under stress. If you are happy with an analysis that uses virtually zero empirical evidence or data to make your determination then that is fine. Everyone is entitled to believe what they will believe. I stick to my original statement that it is plausible, there isn't sufficient (or at least sound) explanation here to prove otherwise. I suggest you take a fundamental fluid mechanics or applied AD course and apply what you learn. As far as this goes, I've spent enough time talking with you here, it's clear you would rather verbally spar with me on an assumption you hold to be a complete truth. I hope in the future you word your responses with more civility and open mindedness than what you have. Good day!

 

[sar104]

I came marching in spouting nonsense and refuse to engage in technical discussion... ok . You pretend to offer technical discussion but demonstrate a pretty mediocre understanding of the physics you attempted to explain. How can we debate technicals while ignoring fundamentals? Dunning-Kruger is in effect.

And yet you were unable to counter even a single technical point in what I posted, and you didn't make even a single technical argument yourself. It's a common enough pattern on forums - show up, claim technical knowledge, assert qualifications, completely avoid/ignore all technical argument, and then act victimized. It doesn't work here.

You or someone else posted "math" that doesn't take into account the specifics or properties of the craft under stress. If you are happy with an analysis that uses virtually zero empirical evidence or data to make your determination then that is fine.

I wrote it and posted it, and you had plenty of opportunity to critique it, but you didn't even try - you just kept referring back to your mantra that it was wrong because ...but drag. You didn't even make a drag argument - you just hid behind being flabbergasted that everyone else didn't agree with you.

Everyone is entitled to believe what they will believe. I stick to my original statement that it is plausible, there isn't sufficient (or at least sound) explanation here to prove otherwise.

Ah - there's the inevitable anti-scientific assertion that everything is just opinion - well played.

I suggest you take a fundamental fluid mechanics or applied AD course and apply what you learn.

Now you are projecting, and rather over-optimistically I'm afraid. It's never a good idea to wave your own qualifications up front in an attempt to further an argument on the internet, not least because you generally don't know who you are arguing with. Aside from the fact that this problem has nothing to do with fluid mechanics, you haven't applied any to the discussion. But be my guest and do so if you want to waste more of everyone's time.

As far as this goes, I've spent enough time talking with you here, it's clear you would rather verbally spar with me on an assumption you hold to be a complete truth. I hope in the future you word your responses with more civility and open mindedness than what you have. Good day!

No - I'd far rather that you had either accepted or disputed my technical argument, point by point, rather than hiding behind alleged qualifications and a complete lack of any argument of your own. Normally you would have landed on my ignore list almost immediately, but what you are pushing is a debunked bad idea that will end up unnecessarily losing aircraft if employed by anyone misled by your posts. You got what you deserved in terms of response.

 

[fpvaddict]

And yet you were unable to counter even a single technical point in what I posted, and you didn't make even a single technical argument yourself. It's a common enough pattern on forums - show up, claim technical knowledge, assert qualifications, completely avoid/ignore all technical argument, and then act victimized. It doesn't work here.


I wrote it and posted it, and you had plenty of opportunity to critique it, but you didn't even try - you just kept referring back to your mantra that it was wrong because ...but drag. You didn't even make a drag argument - you just hid behind being flabbergasted that everyone else didn't agree with you.


Ah - there's the inevitable anti-scientific assertion that everything is just opinion - well played.


Now you are projecting, and rather over-optimistically I'm afraid. It's never a good idea to wave your own qualifications up front in an attempt to further an argument on the internet, not least because you generally don't know who you are arguing with. Aside from the fact that this problem has nothing to do with fluid mechanics, you haven't applied any to the discussion. But be my guest and do so if you want to waste more of everyone's time.


No - I'd far rather that you had either accepted or disputed my technical argument, point by point, rather than hiding behind alleged qualifications and a complete lack of any argument of your own. Normally you would have landed on my ignore list almost immediately, but what you are pushing is a debunked bad idea that will end up unnecessarily losing aircraft if employed by anyone misled by your posts. You got what you deserved in terms of response.

This very well should be my last post on this topic. You haven't made any technical points, you don't know the aerodynamics of the aircraft, much like myself, and therefore cannot support any "technical" evidence. We all have only used basic theories of aerodynamics to speculate on the ability of the aircraft to reduce drag given the hypothetical posted by OP. I didn't come in here asserting qualifications, I simply stated my career, where we use wind tunnels on a weekly basis. I've made it perfectly clear that I don't claim to have a higher or greater opinion than any of you, nor am I asserting what my position as the ultimate truth. I even mentioned that I am relatively new to drones as a whole, I grew up flying other types of RC. So please refrain from putting words in my mouth.

This has come down to pointing out that you can not conclusively state your opinion as true. I've made plenty of observations but you choose to ignore and/or pretend that I didn't. Surface area increase is relatively proportional to drag increase. If you double a surface area of a craft, you have doubled the drag. If you decrease the surface area exposed by half, you have, for all intents and purposes, halved the amount of drag resistance on the craft. Drag and ground speed are inversely proportional. Until you have tested the resistance of the craft at the various positions during flight in a wind tunnel, you do not have technical data, you have speculation. If flying pitched/rolled at an angle reduces surface area, you have reduced drag. If you reduce drag sufficiently, you may increase ground speed. I cant make this any simpler than that.

 

[Zbip57]

If flying pitched/rolled at an angle reduces surface area, you have reduced drag. If you reduce drag sufficiently, you may increase ground speed. I cant make this any simpler than that.

Nobody in this thread (including sar104) has disputed that assertion. It is possible that flying the drone at some particular angle of attack (backwards, forwards, or sideways, or any combination thereof) might effectively minimize the drone's coefficient of drag, thereby increasing its potential maximum airspeed. That is not the issue being disputed here.

If you have measured and discovered that the drone has the least amount of drag and flies fastest when it's aimed (for example) straight backwards, that would be great. In that hypothetical case we'd know that there is some small advantage to flying backwards, rather than forwards when fighting against a headwind.

However, the only question at issue here is, would you make better progress flying home against a strong headwind if you then fly a STRAIGHT path home (with the drone's tail end leading the way), or would you make better progress flying a ZIG-ZAG path (with the drone's tail always leading the way pointing first off to the left, then off to the right, etc).

Zig-zag tacking accomplishes nothing other than wasting extra battery power covering that increased distance traveled.