Testing Futuristic Propeller Designs on my Solar Powered Boat 

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Finally someone just 3d prints the traditional design to be able to compare it with a 3d printed new design.

19:10 Standing barefoot in a boat full of batteries and Chinese power supplies while it's raining definitely demonstrates your dedication to science.

I am astounded by your knowledge of technology. I’m 60 years old and I am known among my friends and family as someone who can build or fix anything. Metal fab, wood fab, automobiles etc. . I’m not computer illiterate but my knowledge is like two fingered chopsticks on a piano compared to the symphonies you compose. My mind is just not geared towards what you are so good at. I am envious but all I can say is “GOOD FOR YOU”. You apply yourself with a passion and have earned your knowledge. I think you are destined for great things.

At 14:38 in, I lived in a houseboat on that dock in 1980-81. The plant covered house is exactly as it was then. That's just off Lynn Street in Seattle on Lake Union, across the street from Mike's Grocery. We had a Laser sailboat and the lake was our back yard!

can you build a submarine, that can be driven with a controller?

The air bubble test at 21:22 is awesome. Great work, I enjoyed this video.

Thank you for addressing the issue of print quality. Every video I've seen about 3d printed toroidal propellers uses some abomination made on a $150 3d printer. It's nice to see someone go with a good print quality and smooth surface finish. I also found it interesting how you discussed the thought process behind your CAD design, and how different design choices could impact the propeller's performance.

I'M SUDDENLY SO INTERESTED IN E-BOATS AND THE EFFICIENCY OF THEIR PROPULSION SYSTEMS. Phenomenal video. My brain enjoyed all 36 minutes of it.

As an engineer, I really appreciate the way you present your videos. You build cool things, explain your thought process and provide high quality shots while cracking subtle humor 😊

I’d build a static test rig that sits in a swimming pool or pond and measures the force output. That way you can easily step through a series of speeds and get a graph of kN/Wh plotted against rpm. It would also make it more viable to keep printing a bunch of rough FDM props for rapidly testing new designs.

Big respect! Its ppl like you that makes the human race and planet earth go forward. Seriously, thank you!!

Great shots of Lake Union, esp the little steam boat! There's a seaplane base just right of where you said "these are probably scrap" that I used to fly in and out of, super fun!

You are one of my “instantly watch” RU-vidrs and I don’t do anything with boats or RC anything. You are just so good and explaining stuff and have a good sense of humor. I love you

Mad props to you for doing all that testing.

One thing I have learned about props is, there is a sweet spot at speed verses revs UNLESS you can vary the prop geometry. Cheers Mike!

This video is for engineers only. Too bad I couldn't stay and watch the rest of the video, my head was going to explode. Good research, I hope your invention comes to fruition .

"I promise were finished prop testing" why,? That's what I'm here for. These videos could be an hour and I'd still watch till the credits. Love your stuff!

That ship 5:01 is actually called Sherpa, built at van Lent in The Netherlands. It's only a couple years old, purpose build as an exploration yacht. I've seen her many times when she was being finished at the yard. Cool to see she is at the other side of the ocean now.

Great vid! Really enjoyed it. Idea: With the two motors put a different prop on each one to see if the boat tends to go let or right to find the more efficient prop.

Just looking at your OnShape sketches... wow! That's SOME work, well above my level. Thanks for leaving them public, hopefully studying yours, might improve my skills! 👍

OK I totally was not expecting that awesome demo with the bubble tube. That came out EPIC. You make filming this stuff look effortless.

On your standard prop blades you need to cup the top edge of the blades. It helps a lot on Boat props less cavitation.

I gotta be honest, I accidently clicked on this video. And Im glad I did. I did not know that I am into propeller design and efficiency. That was pretty cool. And you presented it well, I like your demeanor. U just got another sub. And thank you for opening a whole new interst for me.

At 32:06 - your theory on vibration is probably spot on. Have a look at why windmills all have an odd number of blades. Great video!

I think your problem is that you basically have two parallel blades which are connected abruptly. In other words, at 23:00 you can see that the center of the blade in the image (the line made from the middle of the distance between the inner and outer line) look like a square/rectangle with rounded corners. I think that by elongating the toroid, so that it looks more like half an egg or like a semi-circle or semi-oval, you would get more continuity for the flow, and the higher angle of attack would mean that instead of making a vortex, the water would continue along the blade, from the beginning to the outside to back into the center at the end, and end up either not making a vortex or making only a smaller vortex in the center of the axis of rotation. Also, I think you need to watch the angle of attack not only at from outside in, but also from top to bottom (slicing the blades in CAD/ONSHAPE). Your toroidal propeller starts at 45 degrees from the direction of flow (of air or water), then go to 60 degrees on the outside, then back to 45 degrees. You could try making it 30-45-30 degrees, the higher angle of attack reducing the stalling. Also, I think the propellers they currently sell are simply moving the vortex from the tip of the blades to between 1 third to half of the outside to the inside, which lead to the vortexes being smaller due to the smaller tangential speed at that radius/diameter (when compared to the radius/diameter of the whole wing, form the center). Also, please make a few more blades, one with normal blades angled 45 degrees from front to back (like the top blade at 26:53) to push the water inwards, one with the angle -45 degrees to push the water outwards, then another one with double blades at 45 degrees, then another one with double blades at -45 degrees, then another one which to start with 45 degrees blades then below them to have -45 degrees blades even if they're not connected making them look like a rhomb, then another pair which to have the -45 degrees blades then below them the 45 degrees blades looking like an X, all with the same radius/diameter as the normal ones you already printed, then another one which to be a normal propeller with winglets which to have an average of 45 degrees of angle side to side (60 degrees of angle from the tip of the blade which cuts the water, and 30 degrees of angle from the tip which merges the water together or creates cavitation, the average 45 degrees basically making the winglet, when looking from the outside of the blade to the axis of rotation, moving down and to the side of the blade). This will give you the best range of test data, in my opinion, which could help you design a much more efficient propeller. If you have any questions, feel free to contact me on discord @Sapioit for more details. I'm looking forward to the results of your tests!

10:30 I think it's important to note that for a foil of finite span, there will always be a tip vortex if it is generating lift at all. You can reduce it, but never get rid of it completely.

the flow visualization is darn cool! it's one thing to see these things in CFD simulations like SolidWorks, but to see the actual physics at work is totally another thing!

You could account for wind velocity by driving around a circuit course-corrected by speed-through-water rather than landmarks, which ia speed-over-ground. So drive one direction for set time, and calculate your velocity by water not landmarks (ground), change angle and repeat.

Awesome work! Let me say that designing things like this is EXTREMELY difficult. Many fluid flows don't act as you expect, especially in real world conditions. This makes real world testing incredibly important for optimization. Mad respect

i really appreciate your testing you did, not just 2 days but 3 days of testing (plus reading/researching/sanding/editing) is a lot of work! Loved the air visualization on the prop too, very clever

Don't stop prop testing, that was honestly very informative!

I don't think I learned a single thing from the video.. I just watched it because it was satisfying to see the propellers pushing water 😅

I want more prop testing seriously when you do testing like this. I think are some of your best videos.

You could add a load cell to the transom and measure the force applied by the propeller vs the power consumed. This would be a faster way of testing, and you could ramp up power and get a performance curve.

I appreciate that your sponsor segment was actually fun and amusing to watch. Not just an ad, but some fun content. Kudos.

50 watt-hr/km is 12.4 mi/kW-hr. That's really good. My Rivian gets 2.5 mi/kW-hr. Of course I'm have 7000 lbm truck going 75 mi/hr. Nice work.

Interesting. I did a lot of prop testing with my solar electric boat, but one advantage I had was that my hull is a wide beam catamaran with each motor mounted behind each hull, so I use independent thrust of each motor to steer the boat, which means the simplest way to test and compare props is to put one on one motor and a different one on the other and see which one overtakes the other causing the boat to steer in one direction or the other at various speeds while monitoring power consumption and speed. So far, the Torqeedo props seem to be the most efficient highest performance props available. I think stiffness of material, chord profile, and tip sweep are all factors that play into this. Also, I think a cavitation plate helps and since I’ve added remote electric trim and raised my motors, I’ve found they perform better closer to the surface just under the cavitation plates allowing my hulls to semi-plane.

Sharrow has been doing toroidal boat props waaaaay before MIT's publicity-laden drone prop. And when it comes to efficency, both Sharrow and MIT say that ducted propellers are more efficient. Toroidal is just lighter than ducted setups and does not have the debris issue that ducted props do.

Really interesting! The higher vibration of the FDM may come from the fast that they are not as stiff as the nylon - so the blades actually flap around a bit. I have been casting some propellers for electric outboards (we are breaking lots on our shallow stretch of river). I started with a hard resin and it worked great, but there were significant vibrations and eventually the propellers self destructed at the join of the blade to the shaft. So then I put 10% milled carbon fibre in the resin and this made a HUGE difference - as good as the OEM ones and they were lasting way longer (never sure if it is self destruction now or user error). I then added a 6 hour soak at 50degrees Centrgrade, which stiffened them even more and they are now performing really well - I have to be careful not to take them out of the mould when they are green or I can deform the geometry, so a 12 hour cure, then a 6 hour bake and they are super stiff (but a bit more brittle!!) Love this kind of content!

Lay 2 sheets of kitchen paper flat in the bottom of a large plastic tub Pour some acetone onto the paper Place the propellers ( etc etc) into the tub Put lid on tub. The fumes from the Acetone will go to work "smoothing" off Normally***, it takes a couple of hours in the tub for propellers etc to become smooth *** keep a eye on the items Whist in the tub because if left too long ... They will just completely melt Hope this helps

The noise reduction is supposed to be in the context of marine life, not occupants on the boat itself. It would be another interesting factor to test under water for at different distances and positions from the prop if you do another round.

I love how thorough your investigations are compared to other youtubers, most of them do one iteration and then make conclusions. You seem to really try to understand all the aspects of the problem. Thank you for your content man 👨

damn! Now I can't stop thinking about the sunscreen on the solar panel! Please do that experiment! Humanity needs to know!

I love your idea for the air bubble test! and then your idea to use the shutter speed to see what's happening more easily!

Much respect for the amount of work you put into your videos, this was a big undertaking and it was an informative and fun watch too.

This channel is one of the few that I hit the like button before the video even starts. Idk why propeller/impeller designs are so interesting, but they are.

The biggest problem with toroidal propellers is that if they do not maintain their form that is if they receive pitting and wear and tear that ruins. Their foil form it rapidly deteriorates all of the advantages that you gain from it and its cost is astronomically higher than using a much simpler, cheaper and more robust propeller.

I learned something I never knew about propeller efficiency Thank you for sharing your experience and life with us ❤

I love what you are doing and especially your humble approach. You say you are not a scientist, just a youtuber. Yet you are methodically testing a theory, providing blueprints through an open-source platform and recording the experiments and uploading them to an accessible media platform. Feels like science to me. The best kind of science.

I would think that the one of the reasons the toroidal and bi-blade props are so much less efficient is because the pitch is too steep. That would make sense based on what you found with the air bubbles, that the blades are in a stall.

Awesome video. Love how honest you are. So many RU-vidrs made a design, with crap materials or printer, and then called it a day. You admit there is more to it than just copying the look, and say it looks good. When there is much more nuance into it. It is like a sword like a Falcata or Kurki. What seperates a good one from a knock off is not just the profile or how it looks in 2d space. Yet whether it has a good distil taper as well. Cheap ones will knock out the shape, and it is basically flat metal piece with a small edge. Instead of the spine or length of blade having different widths to balance it. It makes a huge difference in any sword really.

I designed the Myflon / Dyflon 3:42 Bearings for the Apache A64 then went in to develop an idea I used from my Chemistry Background that allowed me to make self Lubricating Bearings for the Space Shuttle Wing Flap Bearings. All the while sitting looking out behind the City of Hope Rabbit Farm. This was in the 1980’s a lot has changed since this period in time. Now I sit around refining Gold from Circuit Boards in a Vented Booth! And Restoring Mopars More fun!

If a wing is deigned for high speed, it should have a small aspect ratio to reduce form drag. It feels like the same rule should apply to propeller. As how fast a boat propeller generally spin, maybe winglets will cause more form drag than the induced drag it decreased... Also, wings stalls at a certain angle of attack, so it doesn't really matter how fast it is spinned. If it is stalled and a certain AOA, it stall at all speed.

You should build an aquarium air pump into your boat so you can do bubble tests with the push of a button 😁

One of the major differences i noticed in Sharrow Marine props vs 3d model you are using is the blade angle, not necessarily pitch but the way stern facing part of the blade is angled. So the loop is angled more aggressively toward the center of the prop. I would try prop design to perfect it further from there.

Talking about the vibration in the two blades prop. Looks up vibration in even vs odd number of props. For example, most windmills are 3 bladed for a reason. Also, notice that the original toroidal props are elongated, not round, but still closed. That would prevent water slipping off the end, but would generate less lateral vortex.

You know, you can just set up a large tub of water at your house, then run each design and get the same efficient data to sort out the best design 😃 And you can also quickly FDM print all different designs you think will be good to test, as long as you keep them all "rough" you can still sort out the best design from the efficiency data. Then send the best design to get laser printed, sand it, polished it and finally test it on your boat.

theres a reason i love your channel always giving the straight facts

Awesome Video! I love to watch your DIY tests where you try everything with the things you have available! I hope there is a followup video coming! 😁

Love the experimenting and data collation. Thankyou for the upload

In regards to this ingenious design that MIT claims to have discovered I suggest you look up the "ship's screw" by Josef Ressel from 1826! If it wasn't for a mechanical problem of the motor during the first test today we could have this type of propellers in much more use!

To test the thrust efficiency. Couldn’t you put the boat in a pool and have it push against a horizontally mounted scale and see how much pressure it puts against the scale. You could also test how much throttle it takes to achieve a certain pressure on the scale. The lake experiment is cool, but there seems to be a lot of variables that can’t be mitigated. Love your videos. So much trial and errors and refinement. Great work.

The vessel in your video the VADM KR WHEELER I helped put the supper structure on in 2007 in Larose Louisiana. I ran a tug boat that held and positioned the large barge crane that put the super structure on the hull. Awesome to see her again!!

That was really interesting, the amount of work you do in the background to get these all set up and working must be crazy!

Would be cool to see a test of those asymmetric low noise drone props used by Zipline. (They look a bit like your "biplane" prop but with only one pair of blades and an opposing counterweight.)

I’m very glad someone can spend so much time testing things out and we can all benefit from a 36 minute TLDR video

Yep. One of your favourite meals. So favourite that you have to read the box to say what it is.

I recently watched a video on microwave cooking by America's Test Kitchen where they basically said it's better to microwave at lower power settings for a longer time than it is cooking at full power. At the lower power setting the food is cooked more evenly. As someone who has used pre cooked dinners in the past (not Factor, they are new to me) I found out I got better taste and texture by putting them in a pan/skillet/pot than with keeping them in the plastic containers and microwaving them.

I love your spirit of inquiry, prototyping, testing, evaluation. Despite the tools being 21st century the spirit of your work makes me think of ways I might also describe the natural philosophers of the early modern period.

the sharrow propeller was WAY different than yours. This was a good vid. Would be interested in a second attempt. May be interview an expert on props for fun.

I'll give you something from submarine tech to think about: If you really want to mitigate the vortices and possibility of staling and make the prop that is appropriate for larger thrust range, surround props with a cone that is slimming towards the end (squirting end), by some marginal degree - let's say 5 - 15 degree. Also make that cone part of your prop, not a separate housing. That way the water that is being pushed out through the cone get's compressed and mitigates the stall effect. Now your prop will not magically get more efficient, but you will get flatter efficiency curve ... and also wider. If you want to make it extra fun you can print it from clear vinyl to see what's happening inside of the cone. Submarine props are purpose designed for specific power plant - hence they can optimise those to the worlds end ... of the shelf props will be used on different power plants, different use cases etc etc - hence old school props are still the king. Good luck on your project.

The comparison between your bubble testing footage and CFD results really shows the power of current CFD tech... Just amazing.

Something that i think would be interesting to see is the performance through rpm ranges represented on a graph. The thing that tryly interests me about it is when you mentioned the forward sweep of the lower blade on the bi-blade prop. Typically forward swept wings on planes have some interesting effects in transonic flight vs typical and rearward swept wings. 14:46

Little Info from an aerospace engineer: turbulent flow makes a foil stall less, not more. So the rougher texture should have less stalling. On aircraft wings you often have little structures to create turbulent flow, so the flow does not stall (especially where control surfaces are)

*The best propeller ever invented is the Vintage 1906 / 2 Blade Spoon type used on most long tail boots. Tough, anti-fouling, self-cleaning, can run in mud and rocks and gives mega thrust cheaply.*

As you probably know, to achieve Bernoulli effects, smoothness is required. Generally, I see water propellers are mainly Achimedes (just throwing water backwards). Bernoulli is pressure differences, resulting in more efficiency. Like helicopters versus wings, to hold up an aircraft. In air at STP, just one-eighth of an inch, cancels Bernoulli, for a certain area. On my Piper one cold day, scattered frost (far less than anything with a one-eighth inch profile) kept my rental plane in ground effect, until my instructor flexed the wings enough to break off the frost. It brings to mind whether creating "frost" with paint, on the bottoms of plane wings, could achieve higher lift at slower speeds, at the expense of increased drag. After all, Bernoulli is acting on the bottoms of wings, too. What few realize, is that methods to reduce fluid velocity on the "negative" side of any wing surface. Price is turbulence, where fluid recombines, at the rear. My sailboat's sail, works because of the "pocket" sewn into the sailcloth. It's not flat, after all. It's why a single surface "wing" can achieve Bernoulli, that "catching and slowing down", of the passing airflow.

Another interesting episode, your improvised bubble flow visualization is ingenious and very effective.

I love how you absolutely went down the rabbit hole on testing for this. Would be REALLY cool to see you do load tests with some kind of water-based wind tunnel. Could help you narrow down on a better prop design

Testing-footage with ducks and boats and people is the most interesting thing on this channel.

Thanks! I have a 30ft sailing yacht that I have been running off 3 solar powered electric motors for 9 years. My boat needs no fuel, she's powered by the wind and sun. I have 4 8D commercial batteries set up for a 24v system. I works good for me. I still need to sail for long distance trips but getting around my general area on electric power is no problem. I have 300lbs of thrust which 95% as much as the recommended gas engine size. I really enjoyed your prop analysis. I always keep my eye out for better props. Keep up the good work!

I think the Real use case for toroidal propellers is in siring peanutbutter. Think about it, the vibrations caused by a normal stiring device or spoon would turn the butter into unrefined oil. Thus a toroidal propeller would keep it at optimal eating consistency at all times. Seems revolutionary to me...

Your underwater bubble trails look great, nice work!

I just discovered this video and am impressed. The engineering legwork you did behind the scenes is top-shelf quality. Combined with the tight narrative and the video editing choices, this content is excellent! Thank you for publishing this!

Props for redoing the test

I love the testing and especially the evil twin brother action. I was thinking a good test that eliminates a few variables would be to put one pf each type prop on and see if the boat turns with equal power on each motor. in calm wind of course.

Awesome video man, love to follow your geeky adventures. It is what I would do if I had the time, but at least I get to watch your journey. Loving the process of your videos and how you explain things. Keep them coming.

I can offer another brilliant idea, the only thing I don’t know is whether your engines have enough power to implement it-You can use something like a hydrofoil This will increase the speed due to the fact that the surface of contact with the water will be reduced.And a huge greeting to you from Ukraine.

I was not expecting to enjoy this video as much as I am. I like how casual and humble you are!

These videos are so informative and entertaining, keep up these awesome projects! Made me get into flying RC planes and even learned how to build my own plane with your help. Thank you

the rule of thumb I've always heard is that the less blades on your prop, the higher your efficiency. The issues of deploying a single bladed prop are left to the reader.

Props! No pun intended. Any man with this much time is very focused.... and not on women😂.

Congratulations... on the one mill plus... always like your videos!! It would b nice if you consider to bring Gwen back for a few videos!! I'm pretty sure it'll improve your ratings!!

Damn, this is an amazing set of tests! Really amazing work, and incredibly thorough!

Love your commitment to accurate testing. Respect.

"You're not really supposed to do that but it's fine" describes my life

@RCTF, Speaking as a retired Professional Pilot, We can agree that a by product of Lift (or Thrust in your case) will always be some percentage drag component. Additionally, the Cavitation your seeing could be described as "Boundry Layer Flow Separation", which is often influenced by Relative Foil Chord Angle and Texture. Conditionally, it would also seem a design with "more Surface Area" will be more likely to be less efficient due to aggregate surface volume and Relative Drag. Fixed Blade aircraft propellers are typically designed for a specific efficiency, Climb Thrust, or Cruise. "Constant Speed" Aircraft Propellers tend to bridge that design through Pitch adjustability to a specific RPM. Thanks for sharing your experiment.

I would love to see you set up some sort of water tunnel thing (like a wind tunnel but water) and isolate a lot of variables for testing the different propellers. Sure maybe you won't be able to spend a day or 3 out on the water but it would be scientific and thats cool

One real advantage I think you'd get with toroidal props is that they would be far less likely to get snagged up in seaweed. The seaweed has a much more tricky path to navigate, to get itself wrapped around the hub, and will just be pushed away constantly, as long as the prop keeps moving.

27:25 OR, as an *alternative to experimental wanderings,* there is sometimes the option of having a much better *understanding* of each phenomenon involved in propulsion *before* the design phase, and a much more realistic *hydrodynamic model* than a simple "hey, I heard about a new propeller design and I want to see if it can magically change everything by *imitating* it without knowing yet how it actually works". Sellers care about names and objects sounding or looking as good as "Fibonacci", "Toroidal", "Hydrophobic", "Hypercavitating", "Ultralaminar", "Bionic", "Anti-vortex", "IA-made" etc… while engineers care about real things: mass, movement, energy form, transfer, viscosity, drag, lift, acceleration, reaction, coupling, resonance, stability, optimisation methods, etc. Engineers make better propellers for each purpose, not sellers. Design types *emerge from* the methods, they *are not* the methods.