friend, you do not have to wait for another type of propeller to be invented, you can be inspired or copy the propellers of submarines, there are many and with different characteristics, especially nuclear submarines, they have the most efficient propellers in history.
Higher *"peak thrust"* should be great as the goal be to as quickly as possible *"step up"* (transmission re: new Mercury Outboards have an automatic transmission) to *"ON PLANE"* (ride atop the water and On the Level to vastly improve hull efficiency at speed.) Once *"on plane"* can then "step down" (Downshift) to control all three vectors on plane meaning pitch, yaw, and roll the Holy Trinity of Boating. This also can be measure beyond mere time over water versus time over land under water which should yield two different velocities no different from aircraft time at speed in air versus time at speed over "land/water" the latter often surprisingly high/beyond the ahem "speed of sound" ahem. In Boating the effect trying to be created is no different from that which a hydro foil does...only without the hydro foil/propeller only plus shaft.
DID YOU EVER LOOK AT SUBS SCREWS? THEY USED TO HAVE SEVEN SCYTHE BLADES AND FOUR RIDGES ON THE HUB TO CANCEL CAVITATION. THIS WAS DONE TO RID OF NOISE, BUT ONCE YOU CANCEL NOISE COUSING CAVITATION, YOU GET RID OF DRUG INDUCED BY IT. THEY DIDN'T DO NINE BECAUSE BLADES WERE BECOMING FRAGILE. BUT YOU CAN TRY TO PUT THEM IN TWO ROWS. THE HUB ALSO HAS TO HAVE RIDGES AS IT HELPS TO CANCEL CAVITATION. BUT ALL OF THIS ONLY WORKS FOR HYDRODINAMICS, NOT FOR AERODYNAMICS.
@@filgiupo4853 ⚠️ God has said in the Quran: 🔵 { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 ) 🔴 [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 ) 🔵 And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 ) 🔴 But if you do not - and you will never be able to - then fear the Fire, whose fuel is men and stones, prepared for the disbelievers.( 2:24 ) 🔵 And give good tidings to those who believe and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow. Whenever they are provided with a provision of fruit therefrom, they will say, "This is what we were provided with before." And it is given to them in likeness. And they will have therein purified spouses, and they will abide therein eternally. ( 2:25 ) ⚠️ Quran
i mean it sounds bad but even if he stood on bare metal at 24-48VDC he wouldn't feel anything really. one its DC and two, the voltage is too low to pass any real current given the skins resistance.
@@X4Alpha4X 24-48vdc easily passes current through wet skin. If it's the path of least resistance, which it probably isn't in this case. Also, there are a multiple 120vac inverters in play down there.
@@ExtremeSquared i mean yea sure some current will pass, but from foot to foot with wet skin, youre looking at like *maybe* as low as 10,000 ohm (a multimeter says my dry feet are 1,500,000 ohms so im being generous), at 48v thats 0.0048 Amps, thats juuust barely under what you'd need in order to even feel it since google says 0.005 A is the lower threshold for DC. and again, thats the absolute worst case scenario of you standing across the full potential. the most likely failure would be the terminals shorting though the water and dropping in voltage to the point everything would just turn off.
@@X4Alpha4X Soak feet in saline for an hour, then retest. You might be surprised how low skin resistance goes. Like you say, the big safety mechanism here is configuration. Almost all configurations of body / potential have a salt water bridge of lower resistance in the circuit. Maybe some really awkward fall could put 24v from a waterlogged hand to waterlogged feet combined with a connector/wire failure, but that's freak accident territory. For what it's worth, I was really just trying to get the attention of alarmists with my post.
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.
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 😊
The benefit comes when attaining a plane. At low and high speeds, the efficiency gains are marginal. But getting on a plane at 2500rpm vs 3500rpm is a huge benefit.
It's a formula you can find all over yootubez my man... But then, I appreciate, this is done very well. Not being able to afford one battery of this type or capacity... But having univershity degrees that suggest I should... Life Sadly isn't a predictable science.
"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!
You are one of my “instantly watch” RUclipsrs 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
Yep same here! One of the few people I have notifications turned on for and just watch every video without even reading the title - always know it will be interesting. And I'm not into RC or boats either.
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.
@@flat-earther I have a question if you're a flat earther explain to me when a boat is moving away why does it look like it's going over a curve and not a straight line?
@@flat-earther this is from a website that has research, Follow ships on the horizon If you’ve been next to a port lately, or just strolled down a beach and stared off vacantly into the horizon, you might have noticed a very interesting phenomenon: Approaching ships do not just “appear” out of the horizon like they should have if the world was flat, but rather seem to emerge from beneath the sea. But, you say, ships do not submerge and rise up again as they approach our view (except in Pirates of the Caribbean, but we are hereby assuming that was a fictitious movie series). The reason ships appear as if they “emerge from the waves” is because the world is not flat: It’s round.
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!
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.
Ship at 5:56 is USNS Vice Admiral K.R. Wheeler, there should be a smaller sister ship around named USNS Fast Tempo. Together they are TRANSCOM's Offshore Petroleum Distribution System.
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! 👍
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.
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
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
It's the same with just about everything you design. A customer designs antennas for mobile phone networks. They spend months on a theoretical design, simulate it using the most advanced software available, and then build a prototypes to test that what the simulations and models claim is what really happens when you use them. Most of the time it's close, but sometimes they get a surprise. These computations are pretty heavy. I remember that before the code was revised to use the GPU's the fastest computer we could build would take several hours to simulate the radiation patterns of the antenna. It's the same with fluid dynamics. We know a lot of how it may work, but once we've worked with the known theories and designed something that works well in fluid dynamic simulation we have to build and test a prototype to see just how close to the simulated results we get. The software has gotten so good that usually there's very little difference between theory and practice, but every now and then there's a surprise. And this is especially true when trying to invent a new profile or radically different design like these toroidal propellers. There hasn't been anywhere near as much data for these shapes to verify the computation models against the real world results.
@@blahorgaslisk7763 it's especially true for something like a propeller that works in a very dynamic environment. Simulation software usually works like a wind tunnel, exposing the test subject to a stable environment, while a propeller will constantly encounter variations in the speed and direction of movement and even density of the material it's propelling through, and the uniformity of those values over it. The way it deals with those variations can both affect its performance and be independent of its performance in a stable environment. And we'd be simulating for months if we wanted to test a decent range of situations.
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 didnt think this would be interesting at all. But Im hooked, Im really enjoying this. He explains everything thats going on in and out of water. Thanks for taking ur time to make this video and explain.
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!
I was thinking this same thing, it seems like he just squared it off which is not part of any toroidal that I've seen. They usually come down to a very slim edge at the transition point of the tip.
lmao this is the first time ive seen a discord handle shared in public like this after the number discriminators were removed and i think i might not hate the change after all
@@r0cketm00se3 Thanks! And the sheer number of different blade designs, even if made from cheap print-at-home materials with proper smoothing (like he did in the video) would reduce the need to spend lots of money to have a company print them, so having that many different designs would help narrow down the science behind the fact.
@@redgopnik2227 I have nothing against the new way, I just think that the change will break a lot of things, including older messages on the internet. If people were still able to use the old way to send friend invites, in perpetuity, just no way for new people to get that exclusive invite code, then I think a lot less people will dislike the change. Unfortunately, small changes from big websites and apps will have a huge effect, because they are inevitably used by a lot of people, and in many cases by a lot of other apps, too. Like how the Reddit API caused Reddit to lose stock value, and some investors are already suing for fraud (because he or someone he knows most likely sold their shares before the announcement), using the "going public" as an excuse for the inevitable fall of the company.
Have you seen a Sharrow prop? they are a commercially sold toridal prop that's been on the market for like 30 years Expensive as sin, but supposed to be "the bees knees"
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 👨
Awesome video. Love how honest you are. So many RUclipsrs 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.
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 .
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.
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 vortices dont necessarily need to be at the tips. For a lift distribution where lift goes to zero and it's derivative also goes to zero the vortices can be moved inboard. This has been experimentally demonstrated on the nasa prandtl aircraft, and may also be the case for some birds.
honestly I think you can get rid of them if you make a design that cancels out them like noise canceling headphones you can possibly cancel out the tip vortex with another tip vortex like noise canceling headphones do with sound because sound is using air
@beatyoubeachyt8303 A wing with finite length has force up in some areas, and not in others. As such the air must circulate in order for the net system vorticity to be zero, which in the far field should be true. There will be vorticies, just maybe not at the tip
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!
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.
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.
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!
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!!
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.
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
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.
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.)
(playing catchup because youtube sucks.) I swear, a lot of the issues with others mindsets you voice on your channel are things I typically sigh out while watching other creators video's. Probably why this is my favorite channel.
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
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!
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!
I appreciate that you aren't stating things you are doing through trial and error and experience and of fact which is a problem I have with a lot of other hobbyist.
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.
@@SoloRenegade so when an aircraft is not stalled at a specific aoa and speed, if it keeps the aoa constant and starts reducing speed it will never stall?
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.
They have indeed been at it for a long time, but have yet to resent any evidence of it having an advantage to speak of against any reasonable run of the mill 4 bladed prop.
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!
@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
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
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.
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.
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.
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.
15:20 Yes, sunscreen will reduce the efficiency of your panels, but not by much. Its meant to work with skin to diffract near-UV radiation, doesn't do that so well with a non-porous synthetic surface.
I never realized how interested I would be in propeller testing like this. I could easily watch hours of this content. I’d love to see more prop testing, but only if you enjoy it and it’s doable for you!
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.
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 video and it was not too long. The details were fun as you went through them. I gained a large amount of information as a layperson and aspiring diy boat builder!
Once you've resolved the weird spanwise water flow at the roots, your design's positive AoA compression ends vs. negative AoA anti-vortex ends on the toroidal design is probably worth a test.
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.
how do you test the conversion efficiency in a tub? we would know only how much resistance each propeller has, not if that power is getting wasted or converted to thrust efficiently
@@FAB1150 I do lots of testing of outboard on test tanks, even on the low HP motors like 4hp, after a little bit of gas you hear de motor have less resistance and then more. These props move a lot of water! Even in a pool, you will create very large currents, it has lots to do with the depth of the water.
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 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...
As I reviewed the video several times in slow motion, I am about 90% certain that those wooden RC props are tractor configuration props. You need pusher props. Also, we would expect 2 blades props to vibrate more because the prop as a whole is more affected when the blade passes the shadow of the mount structure. Another factor is that when a two bladed prop is vertical, it is *much* easier to turn around the vertical axis (like a change in steering input). So if you are changing the steering input at all, it produces judder. The assembly moves a lot when the prop is vertical, and then moves much less when the prop is horizontal. These are the same reasons big wind turbines pretty much never have two blades. With three blades, any time one blade is vertical, the two blades are very much *not* vertical. No judder. Outstanding episode, great thought process, great presentation, great execution, great data, and excellent correction in methods once you discovered the weird outlying data.
how you don't have 10m+ SUBS i'll never know, you do the coolest stuff, that as kids we only dreamed of doing. im almost 40 and im fascinated with all your videos.
I think I'd be tempted to do a lower pitch on the leading blade on the toroidal and higher on the rear blade to test - as as you mentioned earlier, it does resemble a stacked airfoil - if you're using multifoils that are offset you usually use the leading airfoil to feed air through the slot gap to keep flow attached to the higher AoA foil behind it, be interesting if the same holds for a prop.
The air plane props could also be shaking because of the difference in depth. Barely below water to fairly deep. The other props used were closer to the axis of rotation and their tips didn’t change in depth as much.
Some people in the comments under videos about toroidal propellers mentioned that the efficiency of a propeller highly depends on its speed. Each propeller is most efficient at a certain speed. And I think the main advantage of the toroidal propellers is that there's a wider range where they can operate efficiently compared to a normal propeller. And a lot of the huge efficiency claims made for toroidal propellers are made at a speed where a standard propeller is not running very efficiently. But for something like a cargo ship where it will just be travelling at a constant speed, they can just get a standard propeller optimised for the speed it is expected to run at.
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.
The Torqeedo props are worth looking into. I had the Cruise 4.0 outboard and that 3 blade prop didn't go fast but seemed damn efficient. They do boast about how much engineering they put into their prop design. Would love to see how they compare as I bet you could come up with an adaptor with little trouble.
I think pushing water out from the toroid isn't the same effect as on a normal plane, as the toroid prop is esentially a double-decker, meaning the lower outward wash from the top blade collides with the wall and upper inward wash from the lower blade, essentially destroying both vortecies.
I'm not a pilot but, upwind is against the wind, which would create more lift at a slower speed. If you were going downwind, you would need to match the wind speed before you start getting any lift, at which point you already have that much more friction on the water.
The way they presented it, they were definitely talking about audible noise above the water surface, but until I saw that, i was gonna say they could be talking about noise transmitted via the water. if you're designing a torpedo or subhunting ship, it's a good idea to have the quietest possible propellers, so it wouldn't be unwarranted to talk about noise transmitted into water sharrow sounds like they're full of it though.
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!
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
Awesome video on many levels! Suggestions, a canopy for your boat of solar panels using more panels, extra power, plus shade. Sand propellers with 1000-1200 sandpaper in the direction of the flow lines as best you can? (sand one way, in the direction of flow). Time consuming, but? Umm, getting off the efficient usage of electricity subject, how about 90% Hydrogen Peroxide- Silver Screen propulsion? Pure thrust!!! Rather loud, needs to be fully submerged. Ripped the bottom of my Starcraft boat out on Lake Candlewood CT in the late 80s experimenting with that. No analytics, So much foolishness back then, slalom skiing on lunch trays from the high school cafeteria, Ya-hoo 😅
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This made me think that if I put a magnifying glass on it, will it increase the energy or will it just burn? 15:00
friend, you do not have to wait for another type of propeller to be invented, you can be inspired or copy the propellers of submarines, there are many and with different characteristics, especially nuclear submarines, they have the most efficient propellers in history.
Higher *"peak thrust"* should be great as the goal be to as quickly as possible *"step up"* (transmission re: new Mercury Outboards have an automatic transmission) to *"ON PLANE"* (ride atop the water and On the Level to vastly improve hull efficiency at speed.)
Once *"on plane"* can then "step down" (Downshift) to control all three vectors on plane meaning pitch, yaw, and roll the Holy Trinity of Boating. This also can be measure beyond mere time over water versus time over land under water which should yield two different velocities no different from aircraft time at speed in air versus time at speed over "land/water" the latter often surprisingly high/beyond the ahem "speed of sound" ahem. In Boating the effect trying to be created is no different from that which a hydro foil does...only without the hydro foil/propeller only plus shaft.
DID YOU EVER LOOK AT SUBS SCREWS?
THEY USED TO HAVE SEVEN SCYTHE BLADES AND FOUR RIDGES ON THE HUB TO CANCEL CAVITATION.
THIS WAS DONE TO RID OF NOISE,
BUT ONCE YOU CANCEL NOISE COUSING CAVITATION, YOU GET RID OF DRUG INDUCED BY IT.
THEY DIDN'T DO NINE BECAUSE BLADES WERE BECOMING FRAGILE.
BUT YOU CAN TRY TO PUT THEM IN TWO ROWS.
THE HUB ALSO HAS TO HAVE RIDGES AS IT HELPS TO CANCEL CAVITATION.
BUT ALL OF THIS ONLY WORKS FOR HYDRODINAMICS, NOT FOR AERODYNAMICS.
1 I like the boat 2😊3 The prop discussions not for us. 5 where we at 6 let's worry about energy consumption and storage in collection
The air bubble test at 21:22 is awesome. Great work, I enjoyed this video.
Thanks Dustin!!! Means a lot. Big fan of your videos!
you guys need a colab
Agree! That was a great visualization
@@rctestflight He heard you utter the word "laminar" at 34:43 and was drawn like a shark to blood lol
You two should collab!
Finally someone just 3d prints the traditional design to be able to compare it with a 3d printed new design.
Yup, very clever and it makes sense at least!
🤦
@@filgiupo4853 ⚠️ God has said in the Quran:
🔵 { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 )
🔴 [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 )
🔵 And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 )
🔴 But if you do not - and you will never be able to - then fear the Fire, whose fuel is men and stones, prepared for the disbelievers.( 2:24 )
🔵 And give good tidings to those who believe and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow. Whenever they are provided with a provision of fruit therefrom, they will say, "This is what we were provided with before." And it is given to them in likeness. And they will have therein purified spouses, and they will abide therein eternally. ( 2:25 )
⚠️ Quran
@@1islam1 The fuck? You good?
@@1islam1ow does this apply to anything in the video?
19:10 Standing barefoot in a boat full of batteries and Chinese power supplies while it's raining definitely demonstrates your dedication to science.
Hahahahahha
i mean it sounds bad but even if he stood on bare metal at 24-48VDC he wouldn't feel anything really. one its DC and two, the voltage is too low to pass any real current given the skins resistance.
@@X4Alpha4X 24-48vdc easily passes current through wet skin. If it's the path of least resistance, which it probably isn't in this case. Also, there are a multiple 120vac inverters in play down there.
@@ExtremeSquared i mean yea sure some current will pass, but from foot to foot with wet skin, youre looking at like *maybe* as low as 10,000 ohm (a multimeter says my dry feet are 1,500,000 ohms so im being generous), at 48v thats 0.0048 Amps, thats juuust barely under what you'd need in order to even feel it since google says 0.005 A is the lower threshold for DC. and again, thats the absolute worst case scenario of you standing across the full potential. the most likely failure would be the terminals shorting though the water and dropping in voltage to the point everything would just turn off.
@@X4Alpha4X Soak feet in saline for an hour, then retest. You might be surprised how low skin resistance goes. Like you say, the big safety mechanism here is configuration. Almost all configurations of body / potential have a salt water bridge of lower resistance in the circuit. Maybe some really awkward fall could put 24v from a waterlogged hand to waterlogged feet combined with a connector/wire failure, but that's freak accident territory.
For what it's worth, I was really just trying to get the attention of alarmists with my post.
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.
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 😊
hi erikp, have you become a flat earther yet?
The benefit comes when attaining a plane. At low and high speeds, the efficiency gains are marginal. But getting on a plane at 2500rpm vs 3500rpm is a huge benefit.
@@flat-earther Why would someone become a flat earther?
@@fuckednegativemind because we were all lied to when we were taught that the earth is a ball flying in a vacuum
It's a formula you can find all over yootubez my man... But then, I appreciate, this is done very well.
Not being able to afford one battery of this type or capacity... But having univershity degrees that suggest I should...
Life Sadly isn't a predictable science.
"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!
You are one of my “instantly watch” RUclipsrs 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
I don’t even read his titles, I just click. Every single video is awesome, regardless of what I’m in the mood for.
Yep same here! One of the few people I have notifications turned on for and just watch every video without even reading the title - always know it will be interesting. And I'm not into RC or boats either.
I mean, this really is just an engineering channel with "rc vehicles" as a cover story :P
If it's a neon green profile pic in the feed, yes please.
@@coarse_snadYep, you're exactly right. The RC is mostly just for his testing platforms. 😂
Big respect! Its ppl like you that makes the human race and planet earth go forward. Seriously, thank you!!
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!
OK I totally was not expecting that awesome demo with the bubble tube. That came out EPIC.
You make filming this stuff look effortless.
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.
hi Scrogan, have you become a flat earther yet?
@@flat-earther I have a question if you're a flat earther explain to me when a boat is moving away why does it look like it's going over a curve and not a straight line?
@@STAR-GAMING50 Why does the farthest street light in a row of street lights look lower than the ones closer to me?
@@flat-earther this is from a website that has research, Follow ships on the horizon
If you’ve been next to a port lately, or just strolled down a beach and stared off vacantly into the horizon, you might have noticed a very interesting phenomenon: Approaching ships do not just “appear” out of the horizon like they should have if the world was flat, but rather seem to emerge from beneath the sea.
But, you say, ships do not submerge and rise up again as they approach our view (except in Pirates of the Caribbean, but we are hereby assuming that was a fictitious movie series). The reason ships appear as if they “emerge from the waves” is because the world is not flat: It’s round.
@@flat-earthershut up bot
can you build a submarine, that can be driven with a controller?
Then you should look at the titanic
LMFAOOOO
So edgy
They tested it already, wasn't a good idea.....
Make sure it's only safe to like a third the of the depth you're planning on taking other people too!!!
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!
Thanks, I was wondering where this is, it is so cool!!
I appreciate that your sponsor segment was actually fun and amusing to watch. Not just an ad, but some fun content. Kudos.
On your standard prop blades you need to cup the top edge of the blades. It helps a lot on Boat props less cavitation.
You mean make it more like the other design... you don't say...
Mad props to you for doing all that testing.
You're why we can't have nice things.
Love the use of "props" in your comment😂😂
Came here to say the same. Great minds etc.
I see what you did there
@@tvuser9529 What saying is that? "Great minds think alike, fools never differ"? 😈
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.
Ship at 5:56 is USNS Vice Admiral K.R. Wheeler, there should be a smaller sister ship around named USNS Fast Tempo. Together they are TRANSCOM's Offshore Petroleum Distribution System.
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! 👍
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.
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
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
It's the same with just about everything you design. A customer designs antennas for mobile phone networks. They spend months on a theoretical design, simulate it using the most advanced software available, and then build a prototypes to test that what the simulations and models claim is what really happens when you use them. Most of the time it's close, but sometimes they get a surprise. These computations are pretty heavy. I remember that before the code was revised to use the GPU's the fastest computer we could build would take several hours to simulate the radiation patterns of the antenna.
It's the same with fluid dynamics. We know a lot of how it may work, but once we've worked with the known theories and designed something that works well in fluid dynamic simulation we have to build and test a prototype to see just how close to the simulated results we get.
The software has gotten so good that usually there's very little difference between theory and practice, but every now and then there's a surprise. And this is especially true when trying to invent a new profile or radically different design like these toroidal propellers. There hasn't been anywhere near as much data for these shapes to verify the computation models against the real world results.
@@blahorgaslisk7763 it's especially true for something like a propeller that works in a very dynamic environment. Simulation software usually works like a wind tunnel, exposing the test subject to a stable environment, while a propeller will constantly encounter variations in the speed and direction of movement and even density of the material it's propelling through, and the uniformity of those values over it. The way it deals with those variations can both affect its performance and be independent of its performance in a stable environment. And we'd be simulating for months if we wanted to test a decent range of situations.
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.
melon
melon
I didnt think this would be interesting at all.
But Im hooked, Im really enjoying this.
He explains everything thats going on in and out of water.
Thanks for taking ur time to make this video and explain.
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!
I was thinking this same thing, it seems like he just squared it off which is not part of any toroidal that I've seen. They usually come down to a very slim edge at the transition point of the tip.
lmao this is the first time ive seen a discord handle shared in public like this after the number discriminators were removed and i think i might not hate the change after all
@@r0cketm00se3 Thanks! And the sheer number of different blade designs, even if made from cheap print-at-home materials with proper smoothing (like he did in the video) would reduce the need to spend lots of money to have a company print them, so having that many different designs would help narrow down the science behind the fact.
@@redgopnik2227 I have nothing against the new way, I just think that the change will break a lot of things, including older messages on the internet. If people were still able to use the old way to send friend invites, in perpetuity, just no way for new people to get that exclusive invite code, then I think a lot less people will dislike the change. Unfortunately, small changes from big websites and apps will have a huge effect, because they are inevitably used by a lot of people, and in many cases by a lot of other apps, too. Like how the Reddit API caused Reddit to lose stock value, and some investors are already suing for fraud (because he or someone he knows most likely sold their shares before the announcement), using the "going public" as an excuse for the inevitable fall of the company.
Have you seen a Sharrow prop? they are a commercially sold toridal prop that's been on the market for like 30 years
Expensive as sin, but supposed to be "the bees knees"
I want more prop testing seriously when you do testing like this. I think are some of your best videos.
seriously. Inject that science directly into my veins
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 👨
Awesome video. Love how honest you are. So many RUclipsrs 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.
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 .
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.
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 vortices dont necessarily need to be at the tips. For a lift distribution where lift goes to zero and it's derivative also goes to zero the vortices can be moved inboard. This has been experimentally demonstrated on the nasa prandtl aircraft, and may also be the case for some birds.
honestly I think you can get rid of them if you make a design that cancels out them like noise canceling headphones you can possibly cancel out the tip vortex with another tip vortex like noise canceling headphones do with sound because sound is using air
@beatyoubeachyt8303 A wing with finite length has force up in some areas, and not in others. As such the air must circulate in order for the net system vorticity to be zero, which in the far field should be true.
There will be vorticies, just maybe not at the tip
Duct
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.
Don't stop prop testing, that was honestly very informative!
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!
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.
I’m very glad someone can spend so much time testing things out and we can all benefit from a 36 minute TLDR video
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.
The blades are very narrow as well. Looks not very efficient to me, it is more like an air prop.
@@nielsdebakker3283 I agree. They have a lot less surface area too, which I think is a big factor
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!
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!!
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.
yeah but where's he going to get a pool from, pool salesman?
That’s the hard part? Where to get a pool? If that stopped him, he should just shut the whole RUclips channel down.
The bay is a large pool. You could just anchor and tie up anywhere along the shore. However, not moving changes all the dynamics of the system.
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
theres a reason i love your channel always giving the straight facts
The comparison between your bubble testing footage and CFD results really shows the power of current CFD tech... Just amazing.
I was not expecting to enjoy this video as much as I am. I like how casual and humble you are!
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.
You should build an aquarium air pump into your boat so you can do bubble tests with the push of a button 😁
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 came here to ask the same thing!
(playing catchup because youtube sucks.) I swear, a lot of the issues with others mindsets you voice on your channel are things I typically sigh out while watching other creators video's. Probably why this is my favorite channel.
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!
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
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!
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!
I appreciate that you aren't stating things you are doing through trial and error and experience and of fact which is a problem I have with a lot of other hobbyist.
Just amazed that you got 2 days of sun in Seattle.
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.
changing prop RPM changes the angle of attack.
last time i checked wings stall at a specific speed for a given angle of attack, right?
@@kyriakos_kyriakos9103 wings stall at a specific angle of attack, regardless of speed.
@@SoloRenegade so when an aircraft is not stalled at a specific aoa and speed, if it keeps the aoa constant and starts reducing speed it will never stall?
@@SoloRenegade how does change rpm changes AOA? Is variable pitch prop a thing in boat?
Another interesting episode, your improvised bubble flow visualization is ingenious and very effective.
wondering though if the bubbles won't contribute to flow detaching from the "airfoil" ("waterfoil"?)
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.
I too, watched the video.
They have indeed been at it for a long time, but have yet to resent any evidence of it having an advantage to speak of against any reasonable run of the mill 4 bladed prop.
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!
@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
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
Damn, this is an amazing set of tests! Really amazing work, and incredibly thorough!
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.
You're expecting too much from this idiot youtuber lol
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.
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.
Yeah the shape doesn't match and those are the only efficient ones i seen in production that people say that work.
Your underwater bubble trails look great, nice work!
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.
Thank you so much for pointing out the most obvious issue with 3D printed propellers so many seemed to have missed.
15:20 Yes, sunscreen will reduce the efficiency of your panels, but not by much. Its meant to work with skin to diffract near-UV radiation, doesn't do that so well with a non-porous synthetic surface.
I never realized how interested I would be in propeller testing like this. I could easily watch hours of this content. I’d love to see more prop testing, but only if you enjoy it and it’s doable for you!
Love your commitment to accurate testing. Respect.
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.
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.
Props for redoing the test
That was pretty cool. Also shows how "new and better" concepts can sometimes be very hard to actually get right in the real world.
Awesome video and it was not too long. The details were fun as you went through them. I gained a large amount of information as a layperson and aspiring diy boat builder!
Once you've resolved the weird spanwise water flow at the roots, your design's positive AoA compression ends vs. negative AoA anti-vortex ends on the toroidal design is probably worth a test.
That was really interesting, the amount of work you do in the background to get these all set up and working must be crazy!
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 😅
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.
how do you test the conversion efficiency in a tub? we would know only how much resistance each propeller has, not if that power is getting wasted or converted to thrust efficiently
It's definitely not the same
Maybe in a pool, something small as a bathtub or tub would have all sorts of turbulence coming back from the propeller itself
@@FAB1150 I do lots of testing of outboard on test tanks, even on the low HP motors like 4hp, after a little bit of gas you hear de motor have less resistance and then more. These props move a lot of water! Even in a pool, you will create very large currents, it has lots to do with the depth of the water.
That would be a static thrust test so by defintion the efficiency is always 0
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 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...
underrated comment
Hahahaha nice throwback
As I reviewed the video several times in slow motion, I am about 90% certain that those wooden RC props are tractor configuration props. You need pusher props.
Also, we would expect 2 blades props to vibrate more because the prop as a whole is more affected when the blade passes the shadow of the mount structure. Another factor is that when a two bladed prop is vertical, it is *much* easier to turn around the vertical axis (like a change in steering input). So if you are changing the steering input at all, it produces judder. The assembly moves a lot when the prop is vertical, and then moves much less when the prop is horizontal. These are the same reasons big wind turbines pretty much never have two blades. With three blades, any time one blade is vertical, the two blades are very much *not* vertical. No judder.
Outstanding episode, great thought process, great presentation, great execution, great data, and excellent correction in methods once you discovered the weird outlying data.
how you don't have 10m+ SUBS i'll never know, you do the coolest stuff, that as kids we only dreamed of doing. im almost 40 and im fascinated with all your videos.
"You're not really supposed to do that but it's fine" describes my life
like i say a at my friend's fab shop
we make barely happen every day
I think I'd be tempted to do a lower pitch on the leading blade on the toroidal and higher on the rear blade to test - as as you mentioned earlier, it does resemble a stacked airfoil - if you're using multifoils that are offset you usually use the leading airfoil to feed air through the slot gap to keep flow attached to the higher AoA foil behind it, be interesting if the same holds for a prop.
The air plane props could also be shaking because of the difference in depth. Barely below water to fairly deep. The other props used were closer to the axis of rotation and their tips didn’t change in depth as much.
Some people in the comments under videos about toroidal propellers mentioned that the efficiency of a propeller highly depends on its speed.
Each propeller is most efficient at a certain speed. And I think the main advantage of the toroidal propellers is that there's a wider range where they can operate efficiently compared to a normal propeller. And a lot of the huge efficiency claims made for toroidal propellers are made at a speed where a standard propeller is not running very efficiently.
But for something like a cargo ship where it will just be travelling at a constant speed, they can just get a standard propeller optimised for the speed it is expected to run at.
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.
Can you make a single blade propeller?
That seems like fun and I really would be interested in the results...
Vibration.
@@bvisel4558 counter weight
Single blade is the most efficient design, at least through air anyway.
ruclips.net/video/py7AX4eTyIk/видео.html
@@gavinprikril881especially in water, the unbalanced thrust would be just as much of a problem as unbalanced weight
The Torqeedo props are worth looking into. I had the Cruise 4.0 outboard and that 3 blade prop didn't go fast but seemed damn efficient. They do boast about how much engineering they put into their prop design. Would love to see how they compare as I bet you could come up with an adaptor with little trouble.
I think pushing water out from the toroid isn't the same effect as on a normal plane, as the toroid prop is esentially a double-decker, meaning the lower outward wash from the top blade collides with the wall and upper inward wash from the lower blade, essentially destroying both vortecies.
The toroidal prop video that RC RUclips needed
@4:33 isn't downwind what you would want to do? Get some extra air flowing under the wings to provide some "free" lift, so you can take off earlier?
I'm not a pilot but, upwind is against the wind, which would create more lift at a slower speed.
If you were going downwind, you would need to match the wind speed before you start getting any lift, at which point you already have that much more friction on the water.
The way they presented it, they were definitely talking about audible noise above the water surface, but until I saw that, i was gonna say they could be talking about noise transmitted via the water.
if you're designing a torpedo or subhunting ship, it's a good idea to have the quietest possible propellers, so it wouldn't be unwarranted to talk about noise transmitted into water
sharrow sounds like they're full of it though.
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!
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
Awesome video on many levels!
Suggestions, a canopy for your boat of solar panels using more panels, extra power, plus shade.
Sand propellers with 1000-1200 sandpaper in the direction of the flow lines as best you can? (sand one way, in the direction of flow). Time consuming, but?
Umm, getting off the efficient usage of electricity subject, how about 90% Hydrogen Peroxide- Silver Screen propulsion? Pure thrust!!! Rather loud, needs to be fully submerged. Ripped the bottom of my Starcraft boat out on Lake Candlewood CT in the late 80s experimenting with that. No analytics, So much foolishness back then, slalom skiing on lunch trays from the high school cafeteria, Ya-hoo 😅