So any news about the low-noise propellers for the spark?

[VIRACO]

I thought we would hear something by now about propellers but with the release of the mavic air all the attention is on their new product.

Doubt we will see new propellers for the spark....

Any opinions or rumours? Haven't seen anything on the net.

 

[MannyCAM2001]

That would really be cool completely stealthy.

 

[suprPHREAK]

Spark is already quieter than the Mavic Pro with low noise props, so unlikely. Also, the Mavic Air didn't come with such props, so I don't see any R&D going towards Spark.

 

[cozzykim]

I wonder whether it would be possible to 3D print some modified Spark props.

The low noise ones appear to be a variation of the winglets used to reduce turbulence, and thus noise, on airliners.
Maybe it would be possible to 'recreate' the design of the LN props in a smaller version.

 

[cozzykim]

I note that the genuine Mavic LN props do have the upturned tips necessary for 'winglets'.

Many of the cheap 'Low Noise' copies on ebay, for example, simply have a modified profile with no upturn. It amused me to spot some that even simply have a stripe painted on ordinary profile props.

 

[suprPHREAK]

The low noise ones appear to be a variation of the winglets used to reduce turbulence, and thus noise, on airliners.

You are correct. The swept blade functions exactly the same, reducing turbulence off the tip of the wing (blade), thus reducing noise. Also enhances efficiency, as that turbulence is also drag.

I note that the genuine Mavic LN props do have the upturned tips necessary for 'winglets'.

The only reason they are upturned on airliners is to keep the wing shorter to fit more airports, and even then, only on the smallest planes now have it (Boeing 737, for example, is for small airports). Bigger planes, such as 747/767/777/787 all use raked tips, like the Mavic props. They only serve bigger airports, so size is less of a concern. That said, the new 777X has a wing 7 metres longer than its predecessor, longer even than the bigger 747-8, and so its wingtips fold up, like the wings on a Navy fighter jet.

 

[JPY]

Adding winglet to Spark's tiny props won't make much difference.

 

[cozzykim]

You are correct. The swept blade functions exactly the same, reducing turbulence off the tip of the wing (blade), thus reducing noise. Also enhances efficiency, as that turbulence is also drag.



The only reason they are upturned on airliners is to keep the wing shorter to fit more airports, and even then, only on the smallest planes now have it (Boeing 737, for example, is for small airports). Bigger planes, such as 747/767/777/787 all use raked tips, like the Mavic props. They only serve bigger airports, so size is less of a concern. That said, the new 777X has a wing 7 metres longer than its predecessor, longer even than the bigger 747-8, and so its wingtips fold up, like the wings on a Navy fighter jet.

I'm not sure that's all there is to it, the angle of the winglet also affects wing loading, for example.

The genuine Mavic props appear to have an angled winglet, where some of the copies just have a reshaped flat profile at the prop tip.
As I said, some even just have a painted line to look like there's a winglet.

 

[cozzykim]

Adding winglet to Spark's tiny props won't make much difference.

In what respect?

 

[JPY]

In what respect?

About 15% of Spark's propeller are actually blocked by spark itself. You see, these winglet design spreads out the downwash of those props. The current spark props design pushes wind straight down. So producing a wider downwash would instead be blocked by the top of Spark's body. Furthermore, the winglet design would also require increased pitch which will put more stress on the motors: it decreases rpm but increases torque required.
Spark may not be able to fly stably with those winglet prop

 

[cozzykim]

About 15% of Spark's propeller are actually blocked by spark itself. You see, these winglet design spreads out the downwash of those props. The current spark props design pushes wind straight down. So producing a wider downwash would instead be blocked by the top of Spark's body. Furthermore, the winglet design would also require increased pitch which will put more stress on the motors: it decreases rpm but increases torque.
Spark may not fly stably with those winglet prop

Hmm, maybe, tilted up winglets not so much.

Winglets also reduce drag though, so maybe that would offset any downwash shadow.

You point about downwash shadow is good though, as the shadow is mostly at the end of the prop's radius. This suggests that a fixed prop with less drag and more lift from a fixed blade might be better, by adding lift where it's needed where its effect isn't wasted by the downwash shadow.

It's interesting stuff to think about anyway.

 

[digitalmouse]

The only reason they are upturned on airliners is to keep the wing shorter to fit more airports, and even then, only on the smallest planes now have it (Boeing 737, for example, is for small airports). Bigger planes, such as 747/767/777/787 all use raked tips...

Ha! You made me shoot cola out my nose! I've flown in 747s, 777s, and 787s (not the X models, mind you) - they can have upturned winglets too. Google is your friend! Very little to do with airport size - they make the runways extra wide for a reason ya know, and when parked there is generally a good minimum of 3-4 meter gap between parked planes even for the big boys. The airport just staggers their placement if the gates are too close, or busses out passengers to aircraft waiting on the taxiways/tarmac.

The main points for winglets or sharklets is for noise, more fuel efficiency, and reduce that annoying and dangerous 'vortex drag' that makes takeoffs for following aircraft a scary adventure for us small-engine pilots.

On a Spark, as mentioned earlier, the propwash is blocked by some of the drone's body so winglets will have a minimal effect on efficiency. While the general aerodynamics appear to the the same for creating lift, an aircraft wing and a rotorblade have significant differences in how that lift leaves the lifting surface. You generally don't see winglets on helicopters (or jet engine fans, for that matter), but you do see raked-back rotor-tips, which a Spark might be able to take advantage of. The props wouldn't need to be any bigger/longer, just have the last half-centimeter or so re-designed.

 

[cozzykim]

The props wouldn't need to be any bigger/longer, just have the last half-centimeter or so re-designed.

That's what we need.

 

[jlsparky]

Has anyone experimented successfully by "modifying" the little props?

 

[maumau]

Just to help clarify. The purpose of winglets is to avoid turbulent flow of air at the tip of the aircraft wings from high pressure air, below the wing, toward low pressure air, over the wing. This induces, as said before, less vortex, drag, fuel consumption, etc, and makes the wing more efficient. In case of props, it would be irrealistic to add more weight at the tip due mainly to high centrifugal force and high speed. Better efficiency is obtained by special design and shape of the blades.

 

[cozzykim]

Just to help clarify. The purpose of winglets is to avoid turbulent flow of air at the tip of the aircraft wings from high pressure air, below the wing, toward low pressure air, over the wing. This induces, as said before, less vortex, drag, fuel consumption, etc, and makes the wing more efficient. In case of props, it would be irrealistic to add more weight at the tip due mainly to high centrifugal force and high speed. Better efficiency is obtained by special design and shape of the blades.

The point is that turbulence also = noise, so that any modification to reduce turbulence will not only reduce drag but also noise.

Reshaping the tips of a standard set of blades by removing material so that they are like the Mavic Platinum blades could thus theoretically be done without losing efficiency if it reduced drag and noise.

I don't think you could do it by hand though, as the tolerances to avoid vibration are so small at high RPM, it would have to be done with an accurate jig and maybe laser cutting?

We have a possible* template in the Platinum props.

*Though other differences in the blade may make a direct copy of the Platinum tip shape useless.

Is anyone here an aerodynamics expert?

I guess that this would be pretty easy for DJI, and I'd be buying a few sets of low noise blades like a shot.

 

[MannyCAM2001]

This is all fascinating stuff. It truly is. My hats off to you guys for really knowing this subject matter. I would be one of the first to buy them for my beloved Spark. C’mon DJI Don’t forsake the Spark community on innovative ways to make the Spark really fun. You could literally take off from anywhere without notice.

 

[BrandonW77]

Ha! You made me shoot cola out my nose! I've flown in 747s, 777s, and 787s (not the X models, mind you) - they can have upturned winglets too. Google is your friend! Very little to do with airport size - they make the runways extra wide for a reason ya know, and when parked there is generally a good minimum of 3-4 meter gap between parked planes even for the big boys. The airport just staggers their placement if the gates are too close, or busses out passengers to aircraft waiting on the taxiways/tarmac.

I was just watching a show about one of the new Airbus gigantic planes the other night and they specifically said they had to put the upturned points on the ends of the wings because it allows them to get the necessary lift while still fitting most airport facilities. If they'd not used the upturned tips they would have had to make the wings longer in order for the plane to fly and it would not have fit at some airports. So, yes, airport size is a factor in this discussion as the plane needs to fit in an 80 meter by 80 meter box.

The second limit is the problem of airport layout and noise. It has been agreed with the world's airports that new aircraft will fit in an 80-metre by 80-metre "box". This is to ensure aircraft on the runway and parallel taxiways can pass each other and terminals do not have to be totally rebuilt.

Is There A Limit To How Big Planes Can Get? - Airliners.net

 

[maumau]

I was just watching a show about one of the new Airbus gigantic planes the other night and they specifically said they had to put the upturned points on the ends of the wings because it allows them to get the necessary lift while still fitting most airport facilities. If they'd not used the upturned tips they would have had to make the wings longer in order for the plane to fly and it would not have fit at some airports. So, yes, airport size is a factor in this discussion as the plane needs to fit in an 80 meter by 80 meter box.

The second limit is the problem of airport layout and noise. It has been agreed with the world's airports that new aircraft will fit in an 80-metre by 80-metre "box". This is to ensure aircraft on the runway and parallel taxiways can pass each other and terminals do not have to be totally rebuilt.

Is There A Limit To How Big Planes Can Get? - Airliners.net

This is specific to maybe 1 or couple of giant aircraft. It has nothing to do with the reason why winglets are needed.
Don't forget as well that lift is proportional to cosine of the angle of which the winglet is canted. So if they can bring lift it's a plus in efficiency, but not their main goal.

 

[notime]

You are correct. The swept blade functions exactly the same, reducing turbulence off the tip of the wing (blade), thus reducing noise. Also enhances efficiency, as that turbulence is also drag.



The only reason they are upturned on airliners is to keep the wing shorter to fit more airports, and even then, only on the smallest planes now have it (Boeing 737, for example, is for small airports). Bigger planes, such as 747/767/777/787 all use raked tips, like the Mavic props. They only serve bigger airports, so size is less of a concern. That said, the new 777X has a wing 7 metres longer than its predecessor, longer even than the bigger 747-8, and so its wingtips fold up, like the wings on a Navy fighter jet.

Up turned wing tips helps iliminate vortex and increase lift.

Google it.