Results are in!
The propeller adapted from the thingiverse model on post number 24.
It worked but pulled 1500w @ 20kmh, I normally pull around 1000w or less @ 20kmh on my cut down flipsky propeller.
It also made a strange whooshing noise like a washing machine 
My lakes are frozen now, had to break about half an inch of ice to get to a small open water streak yesterday. I’ve changed board, wings and stab and i have some learning to do - no propeller testing for me for quite a while
In hibernation until spring 
This is how it should be done 
So now, we know what to expect and what to look for. It will be interesting to position the dedicated efoil results in a diagram like this one found in the above submarine video :
'https://youtu.be/w90gM7bGdvk?t=364
Another point is where to position the costly (*) jet option offered in 2023 by Fliteboard, Takuma, Foil, Manta (…) +Audi in the above diagram. If it is worse than today’s MIT prop (so left of diagram), called to improve with time:
1 - a jet could become pointless since the MIT prop type has just been proven safe,
2 - brands should offer a welll designed MIT prop for 2024,
3 - @VeFoil , @RC_guy, @Bufadore, @mkefoil, @phillhydrofoilismyli, @Mantafoils Transport Canada will have to review their copy - as an open prop blade can be safe at 4000 rpm although less efficient than a classic “Wageningen style” propeller 
(*) costly because more Wh for same range, so bigger Wh battery (20-30% ?) + bigger front wing recommended, ex Takuma delivers the jet option with a 1750cm2 front wing + reinforced mast and plate, instead of a 1500cm2 and standard mast for the prop option.
'https://takuma.com/en/accueil/358-1330-efoil-carver.html#/72-battery-20a/172-propulsion-jet
a new reinforced mast and a top plate design.
**The Jet propulsion is delivered with the Kujira Helium 1750 wing**
I think it is worth it to go on with different shapes of the sharrow.because @HamburgHarbourFoiler showed that it is near by his best perfoming props at the moment. If it get very close in the next step or even equal it would bring more safety on the other side.
A first commercial toroidal prop at 239usd. Performance should be better than a jet and safe without duct as demonstrated by the merciless “courgette test”.
This propeller (…) was tested in a lab environment with Lift Efoils under variable conditions. Better performance of up to 25% compared with the Lift stock Aluminum prop may be achieved at cruise speeds of up to 17 MPH. You should be able to increase your riding time
(…)
If you ride a board other than a Fliteboard or Lift, please let us know and we will adapt this prop to your board for no additional cost.
This 25% improvement smells like creative marketing to me. I’d rather see the power curve at speed and not thrust per amp.
They say that the toroidal prop superiority based upon Thrust vs Amp is only valid up to 17mph probably because the toroidal prop is probably a disaster in terms of efficiency past 20mph.
Your power curve at speed point:
Let’s take an example at 68A: LIFT 65lbs, Tor. prop v2.2.2 R1 76lbs, thus a 76-65=11lbs improvement.
Making the assumption that the Thrust vs Amp curve is correct, why would this 11/65= 17% improvement be unsignificant ?
Exactly. “Thrust over Amps” tells you absolutely nothing.
If you just lower a random propellers pitch you’ll already getting better numbers there.
Right! This is what i mean. For the user only thing that matters is the ”power needed”@“speed x”
Since propeller efficiency is what it is, one optimum pitch for one speed you can easily skew the numbers by comparing apples and pears. I’ve seen this done extensively in boat propeller advertising.
If you instead provide power curves from zero to x m/s in the same conditions then the results can be objectively compared.
As much as I would like to see a prop like this become suitable for the efoil community this vendor seems kind of sketchy.
The website lists minimal documentation on a relatively expensive part. No other products on the site other than some board “trailers”. No business address or phone number listed. No refund on the “beta” product etc. makes me skeptical on whether this product is even worth trying.
Safe until you get a finger or toe in the curve and then it’s goodbye body part. Also that prop looks terrible!
This cannot happen in a situation where the prop is rotating because the limb is ejected. This makes the toroidal prop less dangerous than a rotating folding prop. Cuts with folding props haven’t been reported yet whereas the risk exists.
At rest the situation you describe means 1-inserting your toe or finger in a loop blade 2-pull the trigger
This is not impossible but rather improbable
If you fall into the direction the prop is spinning, it is entirely possible to get a finger or toe into the prop.
This deserves to be tested 
With industrial machines during initial safety testing I’ve seen people use carrots so simulate a finger…if it breaks a carrot, it will break a finger.
a very interesting video from Daniel for you Toroidal builders.
A really informative video comparing different quality prop styles, materials (no FDM but PA12) and surface finishes where two efoil 65161 motors are used to power the boat…
No, it won’t. Carrots obviously don’t have skin and bone, and ligaments are really strong. I’ve been crack climbing for some 20 years and when those feet slip and your fingerlock is secure you get to test how solid the human body actually is. It’s unbelievably strong.
I think a propeller bruise is totally acceptable, but a cut off finger is not, probably most plastic propellers are ok in this regard - but probably not the steel or alu ones.
Started playing around with some designs in solidworks a few days ago, turns out it is pretty difficult to get right…
After may iterations I have what I believe should be a 7in pitch equivalent prop. (front blade is 7in pitch, rear is probably closer to 9 because the water begins to spin around the prop after the first blade affecting the angle of attack of the second.)
Ignore overall force, I have my motor mount, no wing in the model.
Data at 2300 rpm, 14 mph
