So any news about the low-noise propellers for the spark?
- Thread starter VIRACO
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BrandonW77
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On the show I was watching it was the reason winglets were needed. I wasn't saying that applies to all winglets, just giving an example of where it did apply.
They can't produce their own lift, (or very little, as they're almost vertical), what they do is improve the lift/drag coefficient of the main aerofoil surface by reducing drag and vortex turbulence at the end of the wing where air would normally 'fall over' the end of a flat wing from the high pressure underside to the low pressure upper side, producing the vortices as the wing moves forward.
Birds have similar devices, eagles and such have winglets (feathers) that lift up at the ends, and some birds have feathers on the upper side of the wing that lift when there's a risk of very low pressure forming a cavity or vortex.
Birds have similar devices, eagles and such have winglets (feathers) that lift up at the ends, and some birds have feathers on the upper side of the wing that lift when there's a risk of very low pressure forming a cavity or vortex.
digitalmouse
Active Member
Yes, but you also said "The only reason they are upturned on airliners is to keep the wing shorter to fit more airports..." which is what made me laugh in the first place. It's clearly a false statement, or at the very least an inaccurate one.
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No it isnt. You said upturned tips is were to fit more airports, which is false.
Is this the SparkPilots forum, you know, the one where we're all here because we have a common interest in our Sparks, or is it mumsnet where we have to win the argument at any cost? 
Even if they weren't quieter we could park more Sparks in a given area if the prop tips were turned up. Back on topic; I would definitely spend a bit of cash to get quieter props.
digitalmouse
Active Member
I suspect it may be up to those of us with the time to experiment using 3D printers to solve this. Afterwards, if someone cracks the problem, DJI or some aspiring Asian-based company re-seller like GearBest or BangGood or Alibaba will pick it up and create an aftermarket version en-masse through one of the hundreds of little companies that do that sort of thing.
digitalmouse
Active Member
max59, could the Mavic Air props be used without cutting? It looked like there might be enough room to let them run without collision. If not you could measure any overlap and just trim off that amount, plus a millimeter or two for good measure, and leaving the angled taper in place. and sanding the ends to a point or a shallow curved tip would make it cut through the air better.
Alternatively, you probably could have just trimmed off the white marker area, leaving more airfoil. The props would turn a wee bit slower since there would be more lifting surface in flight, and in principle give you a lower db value.
Whatever methods that did work, the next question is whether you save weight or added weight to affect flight time - one of the Spark's weakest links compared to it's Mavic siblings.
Alternatively, you probably could have just trimmed off the white marker area, leaving more airfoil. The props would turn a wee bit slower since there would be more lifting surface in flight, and in principle give you a lower db value.
Whatever methods that did work, the next question is whether you save weight or added weight to affect flight time - one of the Spark's weakest links compared to it's Mavic siblings.
digitalmouse
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I’ll have a crack at this 
Sparks have a 4.7” prop with a 3” pitch. We know this from the markings.
Mavic Airs, the internet tells me have 5.3” prop with a 3.2” pitch.
As all of the “use mavic air props on a spark” involve cutting a “bullnose” style prop end I doubt that there’s going to be any massive reduction in noise overall. Except for the lower rotation speed for the same amount of lift.
Maybe a redesigned prop tip along the lines of those on a Mavic Platinum will work better?
Sparks have a 4.7” prop with a 3” pitch. We know this from the markings.
Mavic Airs, the internet tells me have 5.3” prop with a 3.2” pitch.
As all of the “use mavic air props on a spark” involve cutting a “bullnose” style prop end I doubt that there’s going to be any massive reduction in noise overall. Except for the lower rotation speed for the same amount of lift.
Maybe a redesigned prop tip along the lines of those on a Mavic Platinum will work better?
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