Toroidal Propeller Testing on my Electric Surfboard 

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I enjoy your RC related content, but I wanted to comment about the sponsor Fum. Fum and other similar products use essential oils for the "flavourings" and currently the long-term effects of inhaling them in this manner is not well understood with limited data. Fum's own "Science and safety" section contains two reports, both of which were commissioned by them and neither of which were peer-reviewed or published in any journals. As for whether they may be harmful with long term use is not for me to say, but I would encourage people to be sceptical of numerous claims made by them and companies selling similar products.

You should definitely use that V8 for another project soon. Nobody ever goes beyond just starting them up on their desk and letting them run. It was soooo cool to actually see it being used to power something.

Sharrow props probably dont have a negative angle of attack, the examples you're looking at probably rotate the opposite way you're considering. It's common on multi-outboard boats to have counter rotating lower units on the engine to correct for prop walk and other torques on the hull.

The search for greater propeller efficiency is admirable. Have you looked into the Hobie Mirage Drive systems based on fish/seal fins? I'd like to see you bring your rigorous testing to that type of propulsion some day.

For your longer distance runs,You might want to try a rimdrive thruster. A rimdrive is basically its own motor with no shaft, the propeller is inverted without a center core (think of a donut with pointy teeth) in use they are practically weedless. I have seen video of commercial versions spiting out pieces of net that would disable a conventional prop. Weeds have to be the main concern on long distance autonomous missions, especially durring mid summer.

I would imagine the efficiency gain from toroidal props comes into play when you are at the limits of tip speed and the normal prop starts cavitating, so you gain a little bit of speed from a smaller prop. You usually want a prop that the engine is capable to rev up to max rpm (set by the manufacturer at which it usually starts cavitating and where the power peak is) for maximum power and so the engine has enough power to get it planing if its a smaller engine, this is not a problem with electric motors because you get instant torque

It's impressive that you can figure all this stuff out! You are so smart! I can't wait to see what you come up with next!

Have you considered measuring output shaft torque and RPM in order to determine prop efficiency? In other words, remove the motor efficiency from the picture. This would make the comparison of the different propeller designs more general across applications.

I love this design contest. Can't wait to see more videos of the deathmatch of props

10:44 @MajorHardware 's "Fan Showdown" series version 2.0 and I'm absolutely stoked for it and the ensuing collab video.

I went to school at University of Washington and watching your videos makes me remember everything great about the Pacific Northwest. I love seeing you take in all the great sights at Lake Union, Greenlake, or wherever you happen to find yourself. Great video, and I look forward to seeing more!

I just love your Boating and Propeller testing Videos. Thank you!

that is a great video of scientific thought process, definitely better then anything I had during grammar school or university looking forward to your next video 🤩

Your dedication is stellar.

Love the scientific approach and that you're willing to dive into topics which are often the point of the entire career of a dedicated specialist. You don't have to be as knowledgeable as a specialist to get a lot out of the experiments, and you could still trip over something nobody knows yet.

Bro never gives up in a good way

Old guy superfan here! After years of life experience, I assure you, you always get better results using a positive angle with the tip.

Props.. this is a very informative an interesting video! Respect for your effort!

Babe wake up new rctestflight toroidal propeller video just dropped

Nice video, glad you've revisited the torroid

I love the underwater slo motion shots of the propeller and thank you so much to making the propeller competition!

cant wait to see the next installment of these experiments, really like this prop design mini-series

It would be cool if you did something like the fan showdown but for props, you would need some sort of indoor testing area with a way to measure thrust and power draw

I'm hooked on all your boat related content, this is good stuff. Especially since it throws in my other favorite subject of 3d printing.

Daniel, I enjoyed this video on propeller testing. Years ago, I was involved in designing a solar/electric boat for a collegiate competition called Solar Splash. The propeller design was critical, and we came to learn about the Wageningen Institute in the Netherlands. They were the leaders back then in propeller analysis. But in addition to pitch and diameter, there were other important parameters such as EAR (expanded area ratio), the airfoil shape, and more. I'm sure these also factor into the toroidal design. The best way to measure the efficiency would be to get a true measurement of the torque the motor is providing, which is not an easy thing to measure although you could build a cradle dynamometer if you really want to get serious. But if you can measure, torque, RPM, voltage and current, you could probably come to some meaningful conclusions. Keep up all the great videos.

your no-fat style of video editing is the best 👌👌👌

Interesting video and cool builds!

Love your scientific research videos like the data breakdown is my favorite 😂

I could watch a montage of the props spinning underwater in slo-mo all day. Its soothing watching the cavitation etc.

Great video man!

nice iteration of the fan showdown. this will be sick

I do think your results are still valid, but I noticed that the propeller boss is a different shape for the toroidal. Ideally, it would be best to control for that variable as well.

I literally have the exact same setup for charging bigger batteries, even with the y splitter as adapter between the power monitor and the battery. Glad to see that my jank is also his jank :D

With your toroidal design the fins are behind each other, while in the pictures of Sharrow they don't seem to overlap like that. Maybe that improves efficiency

I think it would be better to have a constant speed of the boat, then measure the power used over a set distance of travel. I think this would be the easiest and most accurate comparison because you eliminate the variable of drag from the boat moving at a different speed which can have a SIGNIFICANT impact on efficiency of the hull itself, making it difficult to know what contribution the prop really has.

wooh its the fan showdown but propellers, i dig it!

Oscar is a ledge, I learned so much when I was working with an ODrive!

Oh boy, some competition to the fan showdown! Just in a very different environment.

Your videos just get better and better! Love to see your projects and it's fun to see where you test stuff since I live near Seattle.

I am a retired drag boat racer and have fooled around with some off the wall designs with the help of a pretty popular prop builder (Kindsvater).. Our props are nothing like what you are doing but this level of geeky? should have at least 1M subscribers.. Have no idea why but I like watching your videos....

Love it! I keep smiling every time he starts because it sounds JUST like the Jetsons car XD

People at the marina wondering what’s happening. “Ohhhh, that’s just Daniel. No worries!!” 😂🤣👍🏼

The prop competition is just like Major Hardware's fan showdown

You should look at making a 3 blade prop but with cupped tips on the blades. Stops/slows down water spilling off the blades for more thrust. Also the there is a prop type know as the" chopper" where the top inch to 1 1 1/2 of the blade is cut off square.

You are doing the science the rest of us wish we had time to do!

I commend you for these prop experiments. I have a boat and it is over propped on purpose. It is cost prohibitive to increase power and torque to match it, and it is cost prohibitive to buy props to try to tune it. These props are Bronze, but if I could use lost wax and per blade resin printing to cast a replacement in aluminium alloy I could test without huge cost. Just substantial effort. One option might be to make the boat hybrid and couple a pair of Nissan leaf motors to the shaft directly after the transmission. Then we could get the RPM up in bursts assisted by those. Or putter around on only those silently. Or long distance with only diesel.

Gotta love the Jetsons sound it makes!

Another really cool idea you could investigate (though I think it would be considerable more difficult) is wave-devouring propulsion. It would be sick to see that pulled off with your little Boston Whaler

What a great way to wake up new rc test flight

Broski, your engineering skills are ace, but your shilling skills are scary good. Your ads are the best.

Doing a fan.. I mean propeller show-down? Neat!

The negative tip bit was great.

Now you just need to find something else to use that mini v8 for

I'm liking the rctestprop series.

Lol the sup when it wheelied. Classic rctestflight

could you create a water 'wind' tunnel that is a big racetrack of water and then measure flow from each prop? Would perhaps allow for far faster testing of a larger sample of submissions.

First there Major Hardware's Fan Showdown! Cant wait dor RC Testflights Prop Showdown!

Looking forward to the prop competition episode.

I feel like the unmanned board could be useful as an emergency lifeguard, since it can tread water much faster than a person could. Also, I think you need some new Teva's. They're lookin pretty bare.

Great video ! Question: how do you stay safe on the paddle board around all the big boats / ships ? You must be almost invisible how low you are to the water !

Researching sharrow's propeller, it claims to be more efficient at the RPM that boats run at 80% of the time (3000 engine RPM), both lower and higher rpm was less efficient in third party tests. So maybe a RPM test to see if their is any differences in performance? Love your videos!

some interesting results

Very cool man. Superspeed.

Love the R&D on this thanks power boat

Hey, notice the huge air trail from your toroidal propeller downstream of the bulbous center? And how it’s so much larger than the ones from the traditional propellers? That’s drag. And the shape has everything to do with it. Give it the same cone shape as the traditional propellers and you’ll see a fairly big change in efficiency.

All credit to you and your efforts rc ! Keep it up and really like the freshness and immediacy of your approach. Given the potential of your influence, and for the sake of your safety in case you get tossed, would really like to see you wearing an LJ and set a really good example!!!!

Another option for testing would be to fix the speed and measure/log the current draw. It might be interesting to do this at a few different velocities to see if the data is linear and if not, perhaps curves will intersect?

I like this guy, he really smart

cute nail polish @11:31

Phase current is a proxy for torque. It was still a valid test for efficiency of torque to speed

Could you take a look at tubercle propellers? There's a guy on here called Robert Murray-Smith who's making tubercle fans and turbines, which is interesting. They take inspiration from the lumps on whale fins. If you do another RC boat waypoint journey, then could you do a demonstration of how bulbous bows improve efficiency? I've always found it unintuitive that adding one massive lump to the front of a boat improves efficiency so much compared to a knife-edge.

@rctestflight testing community propellers sounds like awesome idea. I'd like to see some 'bionic propellers' thrown in the mix.

I'd like to see a 2 kw waterjet jet on that paddleboard! Jet impellers are really easy but the straighten-squeeze bits are a bit tricky. A dude called Xjet devised a four hole output that prints easily and works really well (less wall friction than vane designs). This design also allows the motor to be mounted at the back of the unit without a shaft and bearings being needed. The four output holes wrap around the motor.

There was a study recently that explored a more jagged design of props, mimicking whale fins with barnacles. I’d be interested to see how those performed as they’re supposed to cut down on underwater noise.

One big difference I see between the "MIT" props and the Sharrow is that the Sharrow is raked significantly aft so that the effective diameter at the leading edge is quite small, achieving maximum diameter near the trailing edge. I wonder if this may have something to do with the efficiency?

I know it seems simple but have you tried just using a simplistic acoustic resonance pump with piezoelectric? Or something similar? A larger into a medium into several smaller will be able to operate much more efficiently at specific speeds for the given input power.

Propeller Showdown Season 1. Lets go!

YES! LOVE that we're going to get a "Fan Showdown" for props! shoutout @MajorHardware!

I love the idea of a prop design competition. Major Hardware did a similar competition with PC fans. Might want to check it out. He had some very wierd submissions.

There 'was' a firm called 'Innerspace' that did ROV props, among other things. The guy that ran it was instrumental for reducing noise on subs. The props were a side gig done in a corner of his shop. - old family anecdote.

Could do a flexible resin like on a toroidal so that it operates as different speeds. So you compress the toroidal prop and the diameter increases. And you extend the job and the Prop diameter gets smaller and runs different speeds and efficiency to see impact.

Thank you!

when looking at the toroidal props straight on, the silver ones have front and back fins on an angle, so 3 pairs shows all six sides. Your printed ones have the front and bottom fins directly on top of each other, so they only show 3 fins from the front straight on.

you should definitely test higher angle of attack and even 4 bladed designs that also have a smaller diameter, less leveraging force on the water might mean the motor can still work efficiently while pushing a similar volume

On bigger ships they use Azipods and those are always mounted the otherway around then the way you mount the propeller. Just an observation.

Was noticing some ventilation happening around the 15 minute mark, you may want to think about adding a cavitation plate (horribly named but that's what they are called) to increase efficiency and the life of your propellers.

If you expect to go through with the propeller contest, a bit more rules would be required. Something like @MajorHardware did with his fan showdown. On a different note, would it be more fair to have a different gear ration for larger props, so they get more torque, but less RPM, while getting the same amount of power?

You need a test cell! If you keep going down this rabbit hole into propellars, which is totally cool, you need better testing and data collection for how many props you are making. I have a few suggestions. I might suggest getting one of those large metal pig troughs at your local farmgoods store to put in the backyard or garage for testing propellars. I might mount a motor/prop assembly at the bottom of a swing arm mounted to the top of the water trough, so that the arm hangs down into the water. You would then run the motor/prop in the water and have the arm pull on a force sensor, then convert that force to find the force exerted by the prop at the end of the arm. You should then divide that force by the power you are drawing to get a specific unit, like newton/watt, that you can use to compare everything, like even high speed and low speed efficiency for different sized props at different speeds. I can't think of a way to convert that to water speed somehow, but I would be very interested to see comparisons between low speed and high speed efficiencies, since I vaguely remember that ship's fuel consumption increased ^3 with speed. Was that equation only for vessels moving through the water, or does that cubic fuel efficiency equation count for propellars too? On the test cell arm, you should pick a motor assembly you like very much that is well made and replacable, then don't change it, for repeatability. I wonder if you could couple the test motor to an identical motor and read the power produced on the other side, like a dynamometer, to measure losses in your motor to compare different speeds or different motors. You could also use the test cell to measure parasitic losses from linkages between motors and props. With a test cell, you could use a bench-mounted power supply for your test motor, like they have in school, for better consistency and to be easier for data collection on power draw. I think it is time for a good test cell, maybe even one that could double as a hot tub - that reminds me, use the same water temp between tests, for conistency with viscosity. A good test setup will make it easier and faster to compare prop designs and dig deeper into the subject with better results. It would be a good for a cheap winter time project too. Then, I'd love follow-up videos to get comparisons between force per watt versus distance traveled out on the open water. This method would also make it easier to compare drag created by different boat hulls. I love your show, man. I watch every episode when I see them. Your cadence, filming, and editting are on point, don't change anything like that. Just keep doing neat shit like you always do, and you're gonna be great.

I might of missed this tidbit, but what about measuring speed through water rather than over land? Current and tides variable can be eliminated. and you only have the wind variable to contend with.

Dude that is cool 🙂

Looking forward to the "fan showdown of propellers" 😂

Instead of the fan showdown, it's gonna be the Prop Showdown!

This might support what you say at the end "which is more efficient in general?" I think the point of the Tordial is it's not most efficient at peak, it's efficient across the range.

to compare fairly you must print several diameter of each design and run the test with constant battery power

I'm sure one can design a toroidal prop that is more efficient at a given speed, but there's clearly alot to making that work. No doubt recovering tip losses is a worthwhile goal. I do wonder how efficient a sub screw is, you know, the ones designed to not cavitate. There are pictures of quasi modern ones online if you dig for them, might be something interesting to take a crack at.

A word of caution. Although paddle boards generally do not, all mechanically propelled vessels do require registration. Along with requiring a registration, comes the need for code compliand lighting, and mandatory lifejackets. You will probably not have any trouble, but you could get ticketed if spotted on public waterways.

Your three-bladed toroidal propeller doesn't look like the one in the pictures that you shown. They look like they would have been a 6 blade propeller with the end tips connected. So if you move the bottom three blades to the center gap of the top blades it might be better and more efficient.

I noticed that there are big thick vortices at the propellor hub. Have you considered adding an aero-hydrodynamic 'nosecone'?

I really want to do that prop design competition!