I don’t think you have anything to be afraid of. What I ment is that Sharrow have put lots of ressources in R&D for this prop. I was also tempted about making a variation of it then read the patents which really covers from A to Z how to make it.
I am no patent expert, maybe can @pacificmeister chime in ? What do you think Merten ? Is it safe to replicate and post it so everybody can benefit from it ? My guess is that it’s still tricky 
Anyone can copy the design of a patented product and share it if they want to. You just can commercialise it. No one can stop a DIY builder doing their thing. If they could, the 3D printing sites like grabcad would be in violation of loads of patents.
Yes! All good, I am not worried about patents, All I was saying is I will read up about the design a bit more. I was just playing as the shape intrigued me as to how it could be achieved. As the propeller is effectively six blades not three I am not sure what the two pitches should be vs the offset between them vs surface area etc. Hydrodynamics is not a subject I can contribute with. All I did was I spend 15 minuets after seeing the post to see how to loft the ~shape. Any suggestions as to the required parameters ? Note I only used 3 sketches but if this was done for real >5 planes & sketches would be required.
In the video I posted you see a drawing of the blade angles
If a lift board costs 12000usd then a prop for 2000usd with 20% higher performance would be an easy spice to a diy build if you’ve got too much cash. It would be great to see it 
What is this?? A concrete mixer?
Right and in addition, you can commercialize it and pay the piper when they come knocking for patent infringement. Good luck enforcing any patents on a bunch of DIYers. Even if commercialized, make enough changes and it should not be an issue.
Does it work?
So what do you think for dimensions? Keep the hub 65mm and make the blades have an outside diameter of 140mm?
I am getting ready to pull the trigger on the Maytech motor myself. I would love the opportunity to print your prop as well. I just requested access via google. Thanks in advance!!!
Here’s a sharrow prop fusion 360 file:
Any input on what to do next is welcome.
In fact, there is a design error. A sharrow propeller is made of N loops (2 to 9 in the patent). Each loop creates a pair of blades that interestingly share the same leading edge. To understand this, you need to take a 1"x5" strip of paper (10cm x 2.5cm), make a cylinder making each extremity touch each other (no twist) and shift extremities on the same line.
In reality, on pict 3 below we can see that :
1- the two roots of each blade within a loop are not on a straight line
2 - the top of each loop is pinched
You must also read @Sliman_O patent information post 115 above. eg doc n°2 gives rake/roll/skew angles plus Alpha (angle of attack).
Someone commented above that patents are only for commercialization. In the US I believe making and using is protected. Anyway, I didn’t bother to look up the international application, but those US pdf’s are applications. If approved and registered they are still protected from the filing date, but not at the moment. Furthermore, one of the applications had multiple claim rejections and looks to be abandoned. The other US application is on their 2nd claims rejection. You can look this up using the USPTO Public Pair system and entering the application number and then clicking the ‘file wrapper’. I used to be into and quite frequently looked up patents. imho unless you are doing big business or have some groundbreaking novel invention it is a waste of time and specially a waste of time to bother DIYers. I know a guy that had a rock solid patent and sued a large corp and thru the hearings one single world in the claims section was deemed ambiguous and not only did he lose and go bankrupt, but his patent was then basically worthless. Once claims are rejected by a patent examiner during the prosecution process those claims must be revised and narrowed and in case law you begin to start losing anywhere near the breath of protection you had if said claims were not rejected.
Are you all actually getting functional 3d print propellers? I mean ones that actually hold up, don’t crack during real use, etc? Ive printed some strong ass stuff, but Im curious if thats what you all are doing. I gave up on ABS long ago, Petg can handle the heat and has some good strength. PLA imho would,only be useful for prototypes as they can melt in FL if you even breath on them wrong.
Yes, even PLA works well if the print is good.
I had a similar issue with printing the prop. I ended up adding a skirt where the blades begin printing at about .035mm thick, additionally print at a slower speed with some hop and retraction and 100% fill also higher resolution (.016 rather than .02mm layers) It took 28+ hours to print but came out perfect…I have a file with the skirt added to a design I found on another site. If I post the file, I will post the original designers name and website where I found it…
Hope this helps…
Regarding the looped propeller design I would like to share my thoughts here:
I think the main question is if the potential savings due to the improved cavitation make up for the double amount of leading edges. Even if the blades of one loop are in line there must be more losses than for a single blade. But lets pretend the efficiency of the prop is the same there could still be the advantage of blade stiffness for example when 3D-printed. Could be a nice solution for self printed props. Then you also don’t have any patent issue in my opinion. I made a design trial based on a wageningen 3-blade base prop with the smallest blade size adjustable in the tool. I bent one set of wings forward and connected the loop. I want to compare this prop to some regular ones on my build. Printed prop is allready ordered. I probably did not hit the perfect design here and I did no CFD check but anyway I want to test it. Due to the mentioned reasons in the chat above I will not share the design on a plattform but if there is some interest to share some design thoughts you can PM me.
Cheers 
Nice piece of work. As you mention, does doubling the wet surface compensate the drag decrease ? Looking forward to seeing your first test results.
IMHO, the problem is not sharing the STL since the design is public and published in the patent but making a profit selling a printed prop for example.
Completely agree. Just want to avoid any discussion in that direction. Anyone is welcome to make a parallel test with that design 
. Just let me know.
I printed this prop and will be testing as soon as the water warms up and my prototype board is ready for the first dunk and fly sea trial. This is one of two I will be testing and I will post the results when I crunch the numbers…
Here’s a couple pics
