There appears to be some discontinuity between the surface blends on the prop. I attached an image highlighting the apparent line. I wonder if it’s noticeable to the touch?
Seems crazy if this an artefact left over from the 3d modelling. Maybe where the prop is turned over or repositioned during milling?
They might end up painting it to hide any artefacts. I noticed some nicks and possible scratches. Would be nice if they posted a behind the scenes video of the manufacturing process.
It’s already been said but one (Sharrow, MIT) can patent a product whose benefits are barely convincing but has potential, let the tinkerers finish the development and then appropriate the advances by saying “we told you so”. Among the communities capable of guiding the development are efoilers and drone fans. The former feel the progress in their bodies through their legs, the latter through their hearing and their joysticks.
Here are the April 2023 advances made by the drone community: the donut shape - strong, cheap but a bit small.
Cutting both extremities of the donut is promising as it reduces the round tips whose net gain isn’t finally proven. It transforms a dual loop propeller into a four bladed one…
I might help with the behind the scenes process : They come here, take some design diyers have been working on, slightly tweak them and sell them.
Simple recipe.
Here is my prop for a flipsky 65161 motor, still working on epoxy coating and sanding mine for testing.
This design is around 58% efficiency cruising at 1500 watts, 16 MPH
Looks like a 2 blade version would be around 63%, I left it 3 blade because my board is very difficult to get up on plane and the loss in low speed trust may make it impossible on my setup.
Top speed I am shooting for higher than 25 MPH
https://www.printables.com/model/576544-toroidal-prop-for-efoil
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How do you measure the efficiency?
CFD, output power (linear speed and thrust) / input power (RPM and torque)
You done any correlation of the cfd model?
i’d wait until ridden before stating any efficiency figures.
I confirmed my CFD model using my old wageningen b series 3d printed prop model and this dataset https://deepblue.lib.umich.edu/bitstream/handle/2027.42/91702/Publication_No_237.pdf?sequence=1
Efficiency numbers from riding are a combination of motor efficiency and propeller efficiency, a test stand would be need to actually get propeller efficiency. Hence why people report kw/km here because it is combined efficiency not propeller.
All I am doing here is making the prop that I want for own setup, if it happens to help anybody else I am happy to share. But I am not here to argue with random people online about if my CFD numbers are 100% accurate. I am sure they are not. I am also sure it is not a perfectly optimized design. If I could do that I would own a prop design business.
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Sorry, and exactly. It’s just that 58% and 63% are very exact figures, i’d think both within the uncertainty of your calculation.
I just realized I forgot the tail cone for people that already downloaded the model. It is uploaded now.
CFD’s should be carried with openwater (no motor pod) as well as “behind” condition to fully visualize the water flow.
Both simulations have to be carried in steady state and transient mode to get the efficiency. Transient mode is what will give you something close enough to the reality.
NB : I’m not criticizing you, I’m grateful for you to help the community. I’m just pointing out to where you should focus if you want to improve the designs (I’m not an expert myself but worked with some experts…).
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55-65% efficiency in this diameter is realistic. This could be a good prop
I’m looking to adapt your propeller for a 6374 motor. Do you have any other format besides the stl files on printables? Would be great to try your propeller on a smaller motor.
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I just tried to scale the STL-file with my CAD system (Solidworks) and it worked fine. It imports to a referable solid body. 
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For people wanting to modify my prop to work on other motors, I put the STEP files on printables
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Has anyone actually tested one of these on an efoil, after 158 posts already?
I used mine a few times before it got too cold here in Minnesota. Had some slight rubbing between the motor and the prop itself. Overall efficiency was a little worse than my B-series printed prop (probably due to it rubbing). Overall seems verry similar to my B-series just slightly less concerned about chopping off my fingers.
Awesome! I’ll post the modified propeller for 63XX motors and credit you once I’m done.
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