Yes thats what I said, that it will be even louder. Here is what he said about this prop and our specs:
“If the flight speed is only 11 m/s , I you can go for 22x7.4 propellers. You will need at least 3600 RPM for reaching 11.1 m/s ( 40 kmph). And with 160 KV and 47.6V you will be able to reach ~ 5000 RPM loaded.”
You can’t calculate speed without knowing drag. This isn’t a quadcopter… it’s human flight. We need to know thrust values.
But GliderPilot, we DO know speeds already. The wing manufacturers all post the trim speeds of their gliders. Plus or minus a knot here and there due to variations in the loading. Heavy fat pilots through to skinny little blokes in their faired harnesses. A quick check on my phone shows 11m/s is around 21knots. Sounds about right for brakes off trim speed.
I said that wrong… speed doesn’t mean anything without knowing the drag and therefore the thrust required to get that speed. A company that makes drone propellers wouldn’t necessarily know the best prop for PPG without knowing the required thrust.
The very fact that he’s referring to airspeed in choosing props is reassuring IMHO. On a quadcopter, unless it’s acending or descending, there is no airspeed in the plane of thrust. What the guy does know is Available voltage, volume and rate of still air approaching the prop (airspeed) and Motor kV. From this he’s calculated the pitch which will provide the most thrust in the 3500-5000 RPM range. This will not be the quietest though, merely the most efficient.
I received my Batch4 - accidentally Paul sent me the wrong props. Since I will use the KV150 motors with 12S batteries the 22x10 will not work with my weight. The thrust would be only 100 pounds.
There is a OpenPPG owner in GB (180KV/12S/22x10props) who was on a real PPG thrust stand and they measured just short of 130 pounds thrust. This is pretty good since the Paracel one prop electric with 15KW motor (short time19KW) has as well 130 pounds thrust.
Since I need more thrust I came up with my own custom 23x13 props:
Theoretically they should work out great:
From the wattage use I would be pretty close to a one prop electric PPG. From the prop tip speed it could even be less noisy. Unfortunately I will not fly before end of October - I’m looking forward how it will work out in real life!
you came up with your own propellers??
how did you make them?
I researched what would be the theoretically most effective prob for electric PPG’s…
First I looked what other electric PPG’s use as propeller’s.
This manufacturer changes thrust with more blade props:
Paracell’s electric motor with a two blade prop has two modes, cruise with 15KW and launching with 19KW. With 19KW they support max 95kg pilots. In climbing mode they use around 14000 watts, which is
like the OpenPPG. At cruise speed they are between 4400 and 5200 watts, which is much better
than the current OpenPPG.
So I looked closer to the propeller design…
Clearly not what RC model props or Drone props are…
To optimize efficiency you can change:
-number of blades
This prop manufacturer came up with this design:
If you buy just carbon RC electric props you just changed the weight of the prop. Sure it will spool
faster up at acceleration because it is lighter but we don’t need this and it does not change thrust or
tip speed for noise reduction.
To change the prop tip design and change the chord length for my props i shortened 27 inch props!
Interesting is that I only reduced the area of the blade by 7%. So my props are 23 inch but have the
area of a 25 inch prop, which I think is optimal to reduce noise and increase thrust for the KV150 motors with 12S batteries.
With our cage size this is the maybe the best I could do and hope it will work out…
Awesome idea to just cut down a larger prop.
Which model did you buy?
@tarifachris please update us with more info! I’m very curious how this ends up working out. Prop model and cost would be great too.
Hi
I’m new to this forum and the World of electric Paramotors. As I am looking for a as quiet as possible setup I’m curious I’m anybody has tried or made calculations with three bladed props. Wouldn’t that reduce the tip speed for equivalent thrust or is my newbie brain playing tricks om me?
Are they just to expensive?
Thanks for an interesting discussion and to very knowledgeable community.
Best Regards
/Martin
The Benefit of going with more blades is more thrust the noise will be greater since there are more tips the quietest would be those weird one blades props with the counterweight but those are normally massive. I doubt we’d get off the ground with any this small
Ok.
My thinking was/is that with a three bladed prop you could go down in size to maybe a 20 instead of a 22 and keep the same thrust but at the same time reduce the tip speed to below 550 km/h
Smaller props need to go faster to get the same thrust so you don’t want to go smaller… a three blade prop has more area and therefore wouldn’t need to spin as fast but has more tips to create noise.
Increasing the area of a two blade and/or the pitch would slow the prop down and reduce the noise. Just keep in mind that any major changes to the prop will change the amp draw which would require a different KV motor (times four motors gets pretty pricey just to experiment). Or you can change your voltage but that also requires another set of expensive batteries.
I have a batch 2 which is designed to run on 12S. My friend has a batch 4 which is designed to run on 14S while spinning the same size prop because it has lower KV motors (higher volts and lower KV). If we use my batteries with his motor we could play with higher pitch and/or larger area blades. I’ve flown his motor with my batteries and I barely have enough power to take off with the 22x10 props. The amp draw is also really low. Increasing the pitch would increase the thrust and the amp draw back up to what the normal setup produces but the props would be spinning slower and reduce noise.
Were these measured values or calculated values?
Hey guys, I’m getting started on X4 build and have spoken with one of the AEs @ Mejzlik. We discussed the option of testing their stock 22 x 12 CF propellers and and just tolerating whatever torque effects there are from spinning all 4 in the same direction. Does this sound reasonable or a deal killer from the start?
Moving forward they will look at making these in CW CCW versions; however it’s unclear if this would be cost prohibitive to request this as a customization.
“WE” or “WEL” are the 2 variants I’m looking at (Wide, Electric, Light)
Additionally I will be running 100A ESC’s, 180 Kv motors, 14S.
Any thoughts on testing their stock props all spinning in the same direction would be much appreciated.
Actually this is a good combo with 22 x 12 props. You would have to limit full throttle to 90%. Maybe with a spring in the throttle or you program the ESC’s.
You could average 4.7 kilowatts instead the 6.0 kilowatts for the X4.
You can search this forum with the problems with Carbon Props. They slip and needed mayor modification to work.
You don’t want all 4 props to spin in the same direction! This is a deal killer. You will need CW/CCW props!
Would the torque be that bad? Worse than a single prop? I know the X4 frame itself has no torque canceling but I think the Dudek harness comes with cross straps to adjust the arms for torque cancelling.
That’s a big difference!
btw - how are these props working out for you?
Thanks for the feedback, I really appreciate it. As for mounting the props, my geometry allows for “direct” mounting of the props without the standoff, so I’ll just have a 20mm BHC with 4 M3’s instead of one large shaft relying on compression. The Mejzlik props allow for drilling of the hubs, and they sell some drill jigs to DIY this if you choose.
Regarding the props turning all one direction, it would just be for initial testing. Long term I agree this kills one of the perks of the X4 design. I think I’m going to wait and see what Mejzlik says regarding price and lead time for a counter rotating 22x12 WEL (sent in this inquiry earlier today) They only need to produce tooling for one propeller…I will post if and when they respond, even if it’s comical. 
