Aerodynamics

[Bivalve]

Okay, so most of us either have or soon will have our mavics...
It should be pretty clear to anyone that has ever built a model airplane, or has seen a helicopter, or just even looked at a bird that this thing, wonderful as it is, has terrible aerodynamics.

It seems to me that the first and most obvious clean up is going to be to the propellers. Run your finger down the leading edge, and you can feel a small but noticeable ridge, presumably where the mold separates. That ridge is in a critical spot. I'm going to try some wet 500 grit paper and see if I can't clean up a set. Of course, rebalancing them will be necessary.

And then there is the leading edge of the drone itself. It looks like the carapace of a crab maybe. What I think we need is a protruding plastic dome with a NACA vent to feed the grill in front of the fan. That right there would cut an enormous source of drag in forward flight, and would look kind of badass, in my opinion. And then the rectangular sections for the legs are just huge sources of drag. I know, it's more important that it fold, but still...

Oh well. Someone will start making parts to clean up this sucker, and I will soon have a nice clean set of props.

 

[dngrmvpl]

I would say that most of the time, an aerial photography drone will be hovering or moving slowly forwards, backwards and sideways. In these situations, aerodynamics will hardly matter.

Better aerodynamics will allow you gain, maybe, a few mph in forward flight if you go full tilt. But if that is what you want, then all the power to you!

 

[spiderpig]

In theory you could probably design a nose cone for it that could be transparent and somehow still allow airflow that could be more aerodynamic.

Plus, aerodynamics are usually used to help fuel efficiency. When it comes to drones, you have to think of them more as helicopters and less as aircraft. I agree that the propellors feel weird. There is also some markings on them, which I would assume might effect capabilities. But this is just the first version of the Mavic....we'll see what they improve when the next Mavic comes out.

 

[Motley]

I agree with @dngrmvpl, I am not sure what reason there is to be so concerned about aerodynamics. This is an aerial photography quad and, despite the sports mode, is not a racing drone. Also, adding anything aerodynamic to the front is likely to mess with the front vision system.

 

[Will.i.am]

I agree with you that cleaning up the leading edges of the props may help with making them more efficient and reducing noise. As far as the rest of the body, with a top speed of 40mph, improving aerodynamics won't help much other than making it look good.

 

[Tas47]

The most beneficial aerodynamic improvements that I've seen for drones are the airfoil arms designed by some Melbourne Uni (Aus) students.3D Printed Titanium Helps Make This Drone Ready to Fight Fires

 

[John Shaw]

Some considerations...
This isn't an airplane. The airflow is not front to back. This is a quad where the body is immersed in the downwash from the props. I also suspect it isn't laminar flow, but rather turbulent as the air from each prop intermixes with that from the other props. Airflow off props has a circular component. Light airplane vertical fins have an angular offset due to this twisting flow. The downwash angle is going to vary with the speed. Hovering it is straight down, when moving it's a combination of the downwash and the forward motion, which varies with speed. You would have to do a lot of research to figure what's best, and it would be different for a photo task than an long range task. Then any fairing adds weight and you have to trade the drag reduction against the increased weight. More weight requires the props to turn faster to get more lift. If you added fairings to change the shape as described you could easily make it worse in some or all situations. I seriously doubt you could find much benefit and you could easily make it worse.

 

[Bivalve]

Hmm.... I hear what you are saying. I think cleaning up the props has the most benefit, and is the easiest to do. Still, I think a light fairing for the front of the thing might be helpful. I'll have to think about it.

 

[Guitarzan]

I agree with you that cleaning up the leading edges of the props may help with making them more efficient and reducing noise. As far as the rest of the body, with a top speed of 40mph, improving aerodynamics won't help much other than making it look good.

I agree with the leading edge of the prop's airfoil shape, but not the "fuselage" for want of a better description.

 

[flyNfrank]

Improving the aerodynamics without a doubt will increase fly time. @Bivalve mentioned removing a small ridge on the props. Less motor drag lowers the amount of power supply needed to each motor.

The Mavic doesn't need the props to spin faster to increase mph. That comes from the Flight Pitch. Btw, I will give anyone $100 that can tweak the mavic firmware settings to produce faster speeds. You could do so by increasing the overall flight pitch, or by making it stay at a set amount of flight pitch longer. The way dji has it set is, when going full throttle forward the mavic will have like -35 degrees of pitch. And the closer the mavic gets to the set 40mph in sport mode, the pitch will begin to level out.

For those that don't know, the FAA allows hobbyist aircraft to fly up to 100mph.

 

[Motley]

Or buy a racing drone since that is what they were meant for. I personally have no need for my Mavic to go that fast but good luck to those that want/need this.

 

[John Shaw]

Hmm.... I hear what you are saying. I think cleaning up the props has the most benefit, and is the easiest to do. Still, I think a light fairing for the front of the thing might be helpful. I'll have to think about it.

I am skeptical about the forward fairing. I tended to agree on the props but after inspecting mine I think it would be a very minor benefit. The seam is right on the leading edge so it tends to cut directly into the air so there is little flow disruption. However the clean up has no drawback that I can see.

 

[flyNfrank]

Or buy a racing drone since that is what they were meant for. I personally have no need for my Mavic to go that fast but good luck to those that want/need this.

Just because it can go fast doesn't mean you have to fly it that fast each time. The vehicle you drive likely goes 100mph. Knowing it is capable of that speed makes it nice knowing it's there should you ever need to use such speed. Could be a family accident and needing to get to the hospital asap. At least it's there if you need it.

 

[Motley]

That's cool, more power to you, I just don't see a need for my Mavic to need to get to an emergency like that. I am sure you use your drone much differently than I do mine though. I feel we already have people out there doing stuff to ruin the hobby we all enjoy, having a drone that can fly 100 MPH (like the racing quads do) and has long range is just asking for more trouble.

You could look into something like the mostly failed (Kickstarter succeeded but was supposed to ship over a year ago but starting to ship now) Krossblade SkyProwler which transforms to winged flight for longer distance and faster speed.

 

[flyNfrank]

That's cool, more power to you, I just don't see a need for my Mavic to need to get to an emergency like that. I am sure you use your drone much differently than I do mine though. I feel we already have people out there doing stuff to ruin the hobby we all enjoy, having a drone that can fly 100 MPH (like the racing quads do) and has long range is just asking for more trouble.

You could look into something like the mostly failed (Kickstarter succeeded but was supposed to ship over a year ago but starting to ship now) Krossblade SkyProwler which transforms to winged flight for longer distance and faster speed.

In other words, should a firmware update come along that allows your Mavic to fly at the speed it's capable of, you would get rid of it rather then never fly it past it's current 40mph?

 

[Motley]

In other words, should a firmware update come along that allows your Mavic to fly at the speed it's capable of, you would get rid of it rather then never fly it past it's current 40mph?

No, I just wouldn't utilize that extra speed since I don't use my drone for that purpose. If DJI wants to officially support that then that is a different story than asking someone to modify the firmware to allow it.

 

[John Shaw]

Improving the aerodynamics without a doubt will increase fly time. @Bivalve mentioned removing a small ridge on the props. Less motor drag lowers the amount of power supply needed to each motor.

The Mavic doesn't need the props to spin faster to increase mph. That comes from the Flight Pitch. Btw, I will give anyone $100 that can tweak the mavic firmware settings to produce faster speeds. You could do so by increasing the overall flight pitch, or by making it stay at a set amount of flight pitch longer. The way dji has it set is, when going full throttle forward the mavic will have like -35 degrees of pitch. And the closer the mavic gets to the set 40mph in sport mode, the pitch will begin to level out.

For those that don't know, the FAA allows hobbyist aircraft to fly up to 100mph.

I don't know the specific limits for the Mavic, but...
The Mavic must provide enough lift to support it's weight at all times. As the Mavic pitches forward the portion of lift to move forward goes up but the portion to support the weight goes down. In order not to descend it needs to increase the overall thrust until the vertical component equals the weight. How far it can pitch forward is limited because at some point full power can't provide enough vertical component and it sinks out of the sky. Also requiring more power will decrease flight time available. I suspect this law of physics limited what DJI could do in Sport Mode.

 

[Motley]

Agreed, I am sure DJI has done some research to know what the Mavic can handle and have optimized it for the use they advertise it for. You have to also remember that the tiny gimbal controlling that camera can only handle so much, DJI likely didn't want to support a speed that made the camera unstable.

 

[flyNfrank]

I don't know the specific limits for the Mavic, but...
The Mavic must provide enough lift to support it's weight at all times. As the Mavic pitches forward the portion of lift to move forward goes up but the portion to support the weight goes down. In order not to descend it needs to increase the overall thrust until the vertical component equals the weight. How far it can pitch forward is limited because at some point full power can't provide enough vertical component and it sinks out of the sky. Also requiring more power will decrease flight time available. I suspect this law of physics limited what DJI could do in Sport Mode.

I read numerous flight logs daily. The only difference while in sport mode is from flight pitch. Sport mode full throttle starts around -35 degrees pitch and levels off to around -30 degrees pitch to fly around the 45mph number.

 

[John Shaw]

I read numerous flight logs daily. The only difference while in sport mode is from flight pitch. Sport mode full throttle starts around -35 degrees pitch and levels off to around -30 degrees pitch to fly around the 45mph number.

Interesting... That make me think that 30 degrees is all they can handle for level flight. They initially go to 35 degrees to get initial acceleration, accept a slight sink, and then come back to 30 degrees for sustained flight.