Testing Futuristic Propeller Designs on my Solar Powered Boat

this video is sponsored by Factor my 3D printer okay everyone we're here at my boat now so step one we gotta take off the old propeller and now we can put on the new propeller freaky idiot oh oh why are you hurting me because an fdm printed propeller will never be as good as a normal propeller even if it's the best design in the world fact of the matter is you could give the smartest Engineers ever trillions of dollars to design the most efficient toroidal propeller possible and if you fdm printed it on your Ender 3 or whatever and left the surface finish looking like this it would still perform worse than Skippy's injection molded hat propeller ever since MIT came out with this publication about how toroidal propellers can make drones quieter there have been loads of people on YouTube 3D printing various toroidal designs with their fdm printers and testing them out most of them look laughably bad and it seems like people are expecting them to outperform normal off-the-shelf propellers spoiler alert none of them do I want to give toroidal propellers a better chance at proving out their high performance expectations and luckily formlabs offered to SLS print some for me so that I can avoid having to fdm print them myself fdm printers use a hot nozzle to extrude hot plastic while the part is built up in layers SLS printers work by using a laser to Center plastic powder particles together to form the part the benefit of SLS is that you can print any shape without support material and the parts are very strong compared to other 3D printing methods that's not to say that good propellers can't be fdm printed it just takes lots of post-processing my boat has been running on these fdm printed propellers for quite a while and they've been great but it took a lot of sanding fairing compound more sanding and epoxy to get them to the point where they're smooth enough to be comparable in performance with an off-the-shelf propeller while I was designing my own toroidal propeller in onshape I was pretty hopeful that it would outperform my old propeller design but I was also fairly skeptical of some of the claims that I had been seeing online in the last few months there have been loads of tech channels trying to ride the toroidal hype way of the MIT started and with that comes a bunch of clickbaity thumbnails I'm pretty sure these are why so many people in the comments section of my videos seem to think toroidal propellers are going to swoop in from the heavens and save us all some of these are just crazy I mean like what even is that thing it's definitely not a toroidal propeller that's for sure and nowhere have I seen data that says they're 138 more efficient in fact the MIT publication doesn't say that they're more efficient at all it only says that they produce less audible noise while creating a comparable amount of thrust as I was working on my design and looking at it as one does I noticed the two airfoil profiles were stacked in a way that was sort of similar to my multi-element airfoil project having multiple airfoil elements can help keep the flow attached even at Super steep angles of attack and this can lead to a super high coefficient of lift I couldn't help but wonder if this was one of the reasons why toroidal propellers are supposedly more efficient to test this Theory I designed another propeller that was basically the same as the toroidal one but the tip profiles terminate independently like a normal propeller instead of wrapping around and combining together to form the toroidal loop the root profile on both propellers is identical there are plenty of arbitrary differences so it's not a perfect comparison but it still should be interesting so after I had my designs I sent them off to form labs to be printed with their fuse one plus a few weeks later a box of props arrived in the mail to act as a control for the tests I had them print my old three-bladed design as well it's worth noting that the diameter of all these propellers is identical so it should be a pretty fair comparison these are all printed out of nylon I was really impressed at how stiff they are listen to this it almost sounds like they are made of ceramic or something like that here's one of the little hubs that fits on the spline of my motor shaft these are printed separately so that I don't have to reprint the entire propeller if there are any tolerance problems or anything like that the hubs were a bit tight fitting into the props themselves so I had to take advantage of the built-in lathe yet again the hubs screw into the props with six screws and with that we have a pretty slick looking little Thruster assembly so then I took off the old props on my boat and put the new ones on and it was off to the lake you'll notice I have the solar panels mounted on my boat now but that's a topic for a future video so don't forget to subscribe here's another solar boat I got a rooftop panel on this one that's pretty nice there's the mega yacht that one used to look big and now it looks minuscule compared to that thing so it's not even 7am and we're already getting 100 Watts the panel tilted up like that 120 watts and it's also pushing us perfectly perpendicular to the wind there goes the float plane taking off downwind must not be windy enough to really matter so I'm just kind of messing around with this battery efficiency measurement here it's milliamp hours per kilometer and it basically measures the current that the motors are pulling and then it does some math combining it with the GPS speed measured by the GPS unit and the autopilot there and gives you a measurement of milliamp hours per kilometer so that's basically your efficiency another seaplane coming in hot damn look at that thing it almost looks like they had an Old Ship converted into a personal yacht so I'm gonna use this little Beach right here as a home base to swap propellers right now I have the three bladed standard props on there so I'm just gonna restart the flight controller so the data of logging gets reset and just do a big lap around the entire Lake and then come back switch props do it again and I'll just repeat that all four times it's gonna be a long day here we go starting the test so what I ended up doing for this test is putting the boat in steering mode so that the heading is being stabilized by the autopilot the throttle on the other hand is not being controlled by the autopilot I manually set the motor pwm command so the motors are drawing a similar amount of power for each run that way the speed is our dependent variable and power is our independent variable it's like it's a busy day at the dry dock company they're lifting some stuff with the crane got a big old Navy ship over here so we're about halfway through the first test I'm using landmarks to kind of Mark my course around the lake here different houses I'm bouncing off to make my turns so we're gonna head to that big yacht and then turned back to the park and switch props so for all our testing today the boat's running on this 100 amp hour 25 volt lifep04 battery right now the solar panels are making about 400 watts and the motor is pulling about 350 Watts so hopefully the battery voltage will stay pretty constant throughout all of our tests today that does matter because we're looking at milliamp hours per kilometer not Watt hours per kilometer they don't have a watt hours per kilometer in here which is kind of unfortunate here's our next contestants I sure am excited to try these things out it's going to be quite interesting the first thing I noticed when I put on the three bladed SLS printed props is that they're way smoother than these fdm printed props I was using before and it's really strange because in air these things are perfectly balanced there's almost zero vibration but in water they vibrate a lot what I'm thinking is that these blades must be asymmetrical like this thing is producing an asymmetrical thrust relative to the shaft so after doing a lap around the lake with the standard SLS props I pulled up to the beach and switched over to the toroidal props I had no idea what to expect but I was hoping they would push the boat along much faster for the same amount of power so after I got both of those installed it was time for another lap around the lake now one big factor that's super difficult to control during efficiency testing like this is wind speed but luckily the winds seemed pretty consistent throughout the day so I don't think there was much of any bias going on it was a relatively calm day first impressions I thought they feel extremely smooth there's almost no vibration compared to my fdm printed props so these are the ones I just took off I don't know if the toroidal propellers are any smoother than these but they're both way better than the fdm printed props I'm going to warm up my Factor meal in the sun because I don't have a microwave on my boat did you know that you can get pre-made meals shipped right to your door did you know this will save you time that would otherwise be lost on meal prep and going to the grocery store do you know how many more propellers you can 3D print with all that saves time the answer is a lot that's why I love Factor meals they're fresh never frozen meals already in just two minutes it's so convenient choose online from over 34 Chef prepared dietitian approved weekly options featuring premium ingredients such as broccoli leeks truffle butter and asparagus oh boy oh boy I'm excited for my lunch oh yeah that's the stuff right there oh wow you guys look what's behind you a giant ship how neat is that this one is turkey chili and zucchini and it's one of my favorites for sure it's so good it doesn't get much better than this I'll tell you good day at the office factor is also super flexible I can easily adjust my order size or even skip a week when I'm leaving town plus you can round out your meals and replenish your snack Supply with an assortment of over 45 add-ons including these delicious smoothies this summer get factor and enjoy eating well without the hassle simply choose your meals online and enjoy fresh flavor-packed meals delivered straight to your door head to factor75.com or click on the link below and use code RC test flight 50 to get 50 off your first Factor box now back to testing upon powering up the motors I noticed that the toroidal props were pulling about 60 watts less power than these propellers now that doesn't mean it's going the same speed that's just based on the motor pwm setting that doesn't necessarily correlate to efficiency so we'll still have to do our lap around the lake and then look at the data and see if they're more efficient or not so to compensate for this I re-trimmed the throttle pwm so that the motors were pulling the same amount of power as they were with the previous props it was pretty interesting that the toroidal props are easier for the motors to spin with less rotational resistance so this brings up the question was the extra energy being used by the other propellers all getting wasted as rotational resistance or were they effective in converting that energy into thrust we'll have to wait and see we got a goose chase look at them go I'm winning winning this race you got nothing on me gooses look at that crusty old boat the Pacific Hunter it looks like it's decommissioned getting ready for scrap this one probably too yeah whoa whoa whoa stop look at that you know what that is that's a tip Vortex this is really significant because they say toroidal propellers are more efficient because of the reduction of the tip Vortex so this footage goes to show that it's not entirely eliminated at least not with my design now I feel like this is a good time to talk about some of the design decisions that I made when I was pulling this propeller design straight out of my ax which is exactly where it came from I didn't do any cfd or optimizations or anything like that so you can take this test with a grain of salt one of the interesting things I had to think about was the angle of attack of the mid profile of the toroid I chose to give it a slightly positive angle of attack because this way it would generate lift outwards and push water inwards the reason why I thought pushing water inwards might be good is that it could pull in extra water from the sides and increase the velocity of the prop wash increased velocity might lead to higher Peak thrust but not necessarily better efficiency this is all just speculation now to argue against my design choice if I were to have made the middle of the toroid have a negative angle of attack it would push water outwards this might make the flow kind of expand as it passes through the propeller which would reduce the velocity of the prop wash at first thought this doesn't seem good but this negative angle at the tip that pushes water outwards is also known as a winglet which are commonly used on airplanes to approve the efficiency it's the same principle they also push air outwards now with no winglet the high pressure from the bottom of the wing wraps around to fill the low pressure on the top of the wing this is what causes a wingtip Vortex vortices are bad because they take energy to make and this is energy that gets taken away from the plane when the winglet is added it pushes air outwards which fights against the vortex rotating up from the bottom this results in a weaker Vortex and a more efficient airplane same deal with the toroidal propeller you might have a Vortex that would be doing something like this and the tip would be pushing air outwards and fighting against it if that's true maybe I should have given the middle of the toroid a negative angle of attack rather than a positive one like I did now this is all just total speculation I'm a YouTuber not an aerospace engineer so if you really care about the technical details here don't listen to me coming in for a landing looks like we're doing 430 Watts from the solar panel that's pretty good back to the nerd stuff for just a sec while I was looking at this view here I had another idea maybe this section of the toroid is pushing air this way and this section is pushing air this way look at those angles that's like half a wingtip Vortex already I have no idea if that's what's really going on but if it is contributing to the vortex it could potentially be making the toroidal propeller less efficient just a thought I had so next we're going to try out these things definitely quite an abnormal boat propeller foreign so I'm calling this design the bi-blade propeller okay let's go when I went to trim the throttle so that the motors were pulling the same amount of Watts as with the other propellers I noticed that these bi-blade props were drawing 20 watts more power than the throatal propellers and 40 Watts less power than the standard props these ones also feel extremely smooth I didn't see any tip vortexes with the buy blades but we'll test that more later on these props are spinning fast I promise it's just the high shutter speed of the camera that makes them look slow it's high noon and I'm doing 450 Watts from the solar panels that's pretty good okay we're rolling into home base here and we're gonna switch over to the two bladed fdm propellers I initially wasn't planning on testing these fdm props but I thought you know what it's a beautiful day and I have unlimited free energy from the Sun so what's another lap around the lake huh let's give it a go my color choices here have nothing to do with Ukraine I just really like yellow and blue now this is kind of an unfair comparison to the other props because these ones are sanded and painted with epoxy so that they're glassy smooth the SLS props have a pretty matte textured surface and I decided to leave it as is because it would have taken a lot of sanding to get them smooth and if they all have the same surface finish then it's still a fair comparison once I find which propellers perform best I'll sand them smooth and use them on my boat until the next breakthrough propeller shape is invented we're getting Max oil solar power now 500 watts amazing that means we're charging the battery at 150 watts because the motors are pulling 350 Watts coming in hot and another one you can hardly see that house because they have so many plants around it wild and it's all floating too that's crazy one of the really weird things about this propeller is that this lower blade here is actually swept forward so it's like angled forward you know like that one weird fighter jet it's very abnormal especially for a propeller so yeah this is just all around a super odd design if I put sunscreen on my solar panels will they make less power the best part about all this is that if you want any of these propeller designs you can have them for free I designed them in onshape which is a cloud native CAD platform that makes sharing files super easy so to get access to these all you got to do is click on the link in the description and create an on-shape account for free then you'll have access to all the source sketches and everything so you can go in and tweak every little dimension and make changes and do whatever you want to these propellers so again check the link in the description and create a free on-chip account and start messing with these yourself how much drag in milliamp hours per kilometer do you think this hat makes probably like five look at that there's a sand barge coming through wow that must have so much inertia I wonder how long it takes to stop this kayakers better watch out and we're going home back to the dock time to review the data so when I got home and checked to the SD card and the autopilot there was no data on it this wasn't a huge issue though because I also had all the Telemetry data that mission planner had logged however on a few of the runs it must have started feeding data into the milliamp hours per kilometer equation before the boat was moving because the values started out weirdly small and then gradually got bigger and bigger this is a problem though because if super small numbers are a part of the data set then it's going to screw up the readings for the whole run so what I ended up doing was manually going through and pulling out power and velocity data from various locations from each lap and then averaging them together to get Watt hours per kilometer and here's the data this seems right to me it correctly reflects how I felt each propeller design was doing during the tests so I feel pretty confident about it for those of you who like myself don't math too good big rectangle bad small rectangle good the toroidal propeller performed the worst and the fdm propellers with the smooth glossy surface finish to perform to the best despite few feeling good about these results I didn't feel like I put enough thought into planning these tests to begin with so I decided to redo it welcome back to the science boat for another day of testing this time around I programmed the boat to hold a consistent speed so that speed is our independent variable and power is our dependent variable additionally I'm using a separate flight controller to log the data so that I can arm and disarm it to start and stop the data acquisition while the boat is already moving this will eliminate the issue from yesterday where it was factoring bad data into the milliamp hours per kilometer equation so I have a lot more batteries today because I'm trying to keep the voltage as consistent as possible for all the tests I've got these two AO lithium 12 volt batteries wired in series and those are connected to all these 24 volt batteries that are in parallel they're in parallel with the ones in series over here you're not really supposed to do that but it's fine and then it gets even jankier over here I have this one big Eco flow it's running this lab bench top power supply that's charging everything at about 270 watts and then we're also getting about 80 Watts from the solar panels right now even though it's cloudy look at that boat wow so yeah this lab bench top power supply has actually worked pretty well at keeping the voltage of these bigger lithium iron phosphate batteries pretty high like almost full so cruise control is set at 1.6 meters per second and we're utilizing 300 and about 300 and I don't know 80 watts to do that speed so this little uh lab benchtop power supply right here is doing 270 Watts so it's providing most of our power which is kind of hilarious so once again I use this beach as a home base to swap between all four types of propellers there goes the Coast Guard I wonder if they've got toroidal propellers nope the data from last time suggested that the toroidal propellers were less efficient and it's kind of looking like we're getting the same results today we're pulling like 630 Watts to go 1.6 meters per second and there's not any more wind than there was on the last run so it definitely seems like they're using a lot more power to do the same speed let's double check that our speed is actually 1.6 meters per second sure is so the weather is not exactly cooperating everything is wet now it's misting real hard at least it's not windy though I put a trash bag over the computer to try and keep it dry yeah it's just unpleasant I'm all wet boat's all wet no good despite the wetness the data looks good for the most part here's a look at our independent variable it looks like the autopilot did a pretty good job at keeping the boat right around 1.6 meters per second for all but the buy Blade run I have no idea why but there was more error for that one but it still looked like it would average out at about 1.6 meters per second so here's the milliamp hours per kilometer data straight from the logs we have the same results as the previous day but the difference in efficiency seems to be more significant maybe this is because the boat was heavier with more batteries and rainwater not sure after that I used a program called MAV Explorer to get Watt hours per kilometer graphs out of the data here's the data from all four runs and here it is all averaged together it pretty much looks identical to the milliamp hours per kilometer graph the toroidal prop was the worst and the smooth prop was the best big surprise totally didn't need to waste all day redoing the tests oh wowie the fire boat is squirting oh that was a pirate ship after that round of testing I tried to do some higher speed testing and I was able to get upwards of like 2.5 or 3 meters per second with the normal propellers but I only had 24 volt batteries with me on this day and I really need more voltage to go much faster I've tested on a 12s before but I really need a 20s to get Max performance out of these motors and escs one interesting thing was that with the toroidal and bi-blade props I couldn't even get the boat going faster than like 1.8 meters per second and at that speed I was hitting the current limit on the escs wow that's a baby goose got chicken mush for lunch today when I went to Nepal a few years ago I saw people eating with their hands for the first time and at first it was kind of startling honestly like you never see that in Western countries but then I realized that it's actually kind of nice to have your hands smell like Curry all day oh there's a duck all right duck oh geez that's an aggressive duck look at that it's attacking me that Duck's not even very nice look at that look at that I probably shouldn't be feeding this duck rice the waterfowl experts say only Wonder Bread after that I taped a tube onto the motors and ran it up to my mouth so that I could blow air down into the propellers and better visualize the flow with the standard prop you can clearly see that there's quite a bit of Vortex action going on it looks awesome but these vortexes are not great for efficiency in this shot here there's even a Vortex clinging onto the center of the prop how cool is that looks like a snake here's some really crisp vortexes it takes energy to make these things and that's energy that's not going into pushing the boat forward that's why they're bad with the Beyblade propeller it looks like the air bubbles get Blended up much more this would suggest that there's more turbulence around the blades it even looks like bubbles are clinging onto the blades as they spin to me this seems like it indicates that the blades are stalled if this is true it could totally be why these props are not performing as well as the standard props one thing worth noting is that I was filming this while putting like 1500 watts into each motor way more power than during the efficiency tests so if the blades are stalled now it doesn't necessarily mean that they were stalled during all the testing the toroidal props had a similar result but with fewer vortices visible around the tips I wasn't seeing any of the acute vortexes I was seeing on the toroidal propeller yesterday again probably because this time the props were spinning way faster if we slow it way down you can see how the bubbles are sticking to the forward most blade at the toroidal propeller so yeah it was probably stalled the vortices we saw on the normal propellers aren't good for efficiency either but they're nowhere near as bad as a stall so why were the blades stalled my guess is that it's a combination of the angle of attack cord length and airfoil profile if we go into onshape and measure the pitch of the blades you can see that we're looking at about 35 degrees at the root this is pretty steep but it doesn't seem like it's too steep most speedboat propellers have similarly steep if not steeper pitch at the root the blades twist as they go outwards and in the middle they were at 26 degrees the way I was using these propellers is about as far from speed boating as you can get so I definitely should have designed them with a lower pitch I was initially hoping to do higher speed tests with them but that didn't work out I think maybe one of the biggest problems with these props was the airfoil profile typically props get really sharp at the tips and mine were pretty chubby in comparison I made the decision to keep them a bit thicker due to the fact that they were just going to be made out of plastic not metal the profile at the top looks more like a banana than an airfoil profile and the one at the bottom looks much worse if it were easy to make a nice airfoil profile throughout the toroidal loop I would have done that but it's not easy or at least my cad skills are not quite at that level the profiles of the bio blades are identical to the toroidal propeller at the root but they are a bit better at the tips the trailing Edge is probably still too thick to perform well let's compare all this to the normal propeller I was testing against it has a 29 degree pitch angle at the root for comparison that's six degrees less than the other props and at the tip the pitch angle goes down to 18 degrees furthermore it has a much deeper cord and a deeper cord can deal with higher angles of attack without stalling as easily the other props had a much shorter cord length so this makes them more likely to stall this is the same reason why you never see an airplane with a high aspect ratio Wing flying at high angles of attack like this deep cord Delta Yak that I built when I was little so after these two days of testing I've learned that my toroidal propellers suck does this mean that alter oil propellers suck no absolutely not if you believe the data that Cheryl Marine puts out about their propellers then it's possible that toroidal propellers could be upwards of twice as efficient as a normal propeller at certain speeds now I'm not saying that they're fudging their numbers or anything like that but in general when any given company is trying to sell you a product I always just try and automatically assume that the numbers are getting fudged a little again I'm not saying their data isn't true but I would just like to see more data from unbiased sources I've only been able to find one form post from someone that seemed like they had no Financial stake in their claims and they saw an 11 efficiency increase at displacement speeds and a one percent efficiency increase at planning speeds this is really interesting because most of charo's data suggests that they are seeing the biggest Improvement at mid-range planing speeds not slow speeds so it's kind of backwards also I couldn't help but notice that some of the stuff on their website totally smells like marketing BS here they say most of the boat noise is caused by tip vortices are you sure about that I mean I've never heard an underwater tip vortices before all I hear when I'm on a boat is engine noise and water splashing now it would make sense that the boat would be quieter if the engine is running at less RPM to achieve that speed but noise from the tip Vortex I mean come on that's only a thing with air propellers again I don't know anything about this company so I probably should just give them the benefit of the doubt and say that they're great and all that and again I'm just a YouTuber with a shitty electric boat so don't trust me on anything but it would be nice to get some real unbiased scientific data on this stuff like with a detailed test procedure and all that because after all a 105 efficiency increase is a huge claim to make when I see that a propeller is this much more efficient I can't help but wonder why it's not more commonly used the maritime Transportation industry uses hundreds of millions if not billions of dollars worth of fuel every single day you would think that if there was a magical propeller out there that would just hand them even just like five percent more fuel efficiency than the economic incentives of adopting that propeller design would be more than enough to make it happen even if it costs way more to manufacture then again chero is a relatively new company so maybe it will just take more time for their design to catch on I wouldn't be all that surprised if we do start seeing cargo ships using toroidal propellers in the next few years now Cheryl Marine does hold a patent for this propeller design so that could be why it's not more commonly used the speed at which it gets adopted by the maritime industry is limited by the speed at which they can scale up their manufacturing operation so maybe it'll catch on over time it's kind of funny I didn't see this patent until after I had already received my to Royal propellers in the mail but the drawing in their patent looks way more like the ones I drew up in CAD than it does any of the propellers that they currently sell most of theirs have way more of a rake to them or sweep in the airplane World their patent also covers drone propellers so it'll be interesting to see if they go after Fox ear or any other companies that are trying to sell toroidal drone propellers Fox ear recently started selling this propeller that they call the donut and it seems to perform no better or worse than any other standard fpv propeller although I have heard a lot of people say that they really aren't any quieter like the Mit paper said they might be so back to my design it is a bit of a bummer that my boat didn't instantly get 105 more efficient but that's not really unexpected to design an efficient propeller it takes a lot of testing and iteration on the design and these days cfd is a big part of it I did none of this for my design so yeah no surprise that it didn't turn out working very well well we're back out on the lake again I was having nightmares that the rough surface finish on the SLS props was causing them to stall and screwing up the tests so last night I sanded them and today we're going to test them out again you probably thought I was done with science but let me tell you something gosh darn it I'm never done with science I'm about to get run down by a seaplane so what I did last night was painted these props with epoxy and let it cure and then this morning I sanded them down smooth now if you look closely they look kind of scratched but I can assure you that they feel extremely smooth to the touch so I did both of the three bladed normal props and then I did one of the toroidal props I'm gonna do an efficiency test with the normal three-bladed props so that I can compare the raw surface finish to the new sanded surface finish but I also did one of the toroidal props just so that I can see if it was the rough surface finish that was causing the flow separation and the cavitation around the blades I won't bore you with more testing footage so let's just jump to the results here's the watt hour per kilometer measurement for each lap the two bladed prop was still more efficient this is not surprising though because in general it's common that the fewer Blades of propeller has the more efficient it will be more blades can lead to higher Peak thrust but fewer blades is better for efficiency so the two bladed prop was 13 better this is only a one percent improvement from yesterday when it was 14 better these results suggest the surface finish isn't super important but I'm not sure I totally trust this data to have more confidence in the result I would need to do more test runs for more data points I'm using the two bladed props as a control here I can't really compare the non-sanded three-bladed props to the sanded three-bladed props across two different days because the boat weighed different amounts on each day the thought of going the rest of my life with inefficient bow propellers has really put me into a state of impression like what if I just never achieve my dreams and it's all just because my boat isn't efficient enough I can't let that happen so I have these wait are those airplane propellers yeah they are I've seen people on the internet use airplane propellers on low RPM boat motors and apparently they're really efficient so I'm gonna give it a try so these are xor wooden propellers and the propellers in their default form just won't fit on these motors the shaft is too wide so I had to get creative here and machine some brackets on my stepcraft m1000 out of carbon fiber and I also machined the propellers themselves I had to build a nice little fixture to hold the propeller while the End Mill went in and drilled four holes and then cut off one of the blades so now we have these wooden blades mounted out further from Center and that allows me to attach them to this spline hub thing I've been using I don't really know what to expect efficiency wise but I do expect that the motors will have a lot more rotational resistance and not want to spin very fast and I think if I do try and force them to spin very fast these things might just snap so I'm guessing that they're going to be good for low speed efficiency but not for high speed driving whatsoever we'll see so obviously there's going to be a ton of drag around the center section but that's fine for now this is just going to be a quick test I'm sure a lot of people are thinking that you can't just slap a huge propeller onto a motor that's designed for a smaller one and generally that's true but in this case these motors are using field oriented control more specifically the vesque motor control software and they're operating in torque control mode so the motor doesn't care what RPM it's spinning at it's just trying to hit its torque set point so that should work in theory but will it work in real life let's find out I'm a little concerned because there seems to be a lot of like ultra low frequency vibration I don't even know if we're going to be able to hit the target speed for the efficiency test which is 1.6 meters per second let's try it throttling up one problem that I didn't foresee was that the diameter of the prop is so big that the tips get really close to sticking out of the water throttling up oh God the whole oh God the motors are jiggling oh no I don't know about this they're really vibrating bad this is no good let's try and put it in speed control mode oh nope nope nope nope nope nope nope nope nope too much vibration not good I'm not going to do that that's sketchy my Motors are going to fall off and the steering servo is going to strip bam I was really hoping that would be super efficient look at that it's a steam ship I'm gonna do a little test here and see how smooth they spin in the air foreign they seem pretty smooth in the air so I don't think it's a balance issue my guess is that the vibration is caused by when the blade passes through the turbulence that's caused by this part here while blowing air into the props I noticed bubbles sticking to the forward surface just like they were doing with the toroidal propellers so maybe the blades are stalled I'm not actually sure if bubbles clinging to the blades are cause or effect of a stall it's possible that the blade could briefly stall out when it chops through the big pocket of air and then the bubbles just cling to the turbulence for a while I think I'll revisit this High aspect ratio blade stuff in a future video but for now this video is already way too long so let's move on I wanted to get some underwater footage of the sanded toroidal propellers in hopes the smoother surface finish would eliminate the stall or whatever was causing bubbles to stick to the blades the answer is no also if I screw with the frame rate to make it match the RPM we can more clearly see what's going on it looks like a stall or cavitation or something is originating at the root of the upper blade [Music] oh here's lower RPM looks like it's still happening the standard prop looks like it has a little bit of clinging bubbles too but not nearly as bad and only near the root the reason why this video is so much better than the underwater video from yesterday is it was more sunny on this day so the camera's shutter speed was higher [Music] so remember how earlier in this video I was talking about how I wasn't sure if I gave the center profile of the toroid the correct angle of attack yeah so while I was reading through the patent that Cheryl Marine has on these propellers and it turns out they actually do have a positive angle of attack just like my propeller so that was great to hear it means my propeller is more representative of theirs and also they really have a lot of data and details on all the different angles throughout the profiles in the toroid and that was really reassuring to me it kind of suggests that they truly did all the research and development work to make these propellers super efficient so I don't think they're selling snake oil I think they are legit and I think their propellers are legitimately more efficient but I would just like to see more data on it because like 105 efficiency gain is a huge claim and for all I know the props they were comparing against could have been some of the worst props out there maybe if they compared their toroidal propellers to some super high-end regular propellers they would have been much less impressive not sure so at the very last second on the same day I uploaded this video I got the chance to run these propeller models through air shaper which is a super easy to use cloud-based simulation program for aerodynamic analysis I didn't have enough time to really dive into the results but at a glance you can see that the surface flow lines of the regular propeller look pretty much like you would expect them to nice and laminar however if we take a look at the toroidal propeller the lines are kind of all over the place the most interesting thing I saw was at the root of the front blade we have a lot of spanwise flow going on not cord wise flow like you would want on a propeller I interpreted this as meaning the root of the blade has way too much sweep if the blade entered the Hub at more of a perpendicular angle we might have avoided this problem altogether and maybe even prevented the stall that I was seeing on the underwater footage this explains why normal boat propellers have these lobe shaped blades where the root comes out of the Hub at a perfectly perpendicular angle or even is swept forward in some cases super interesting stuff on the normal propeller I noticed a high pressure area area at the trailing Edge on the top of the blade and a low pressure area on the trailing Edge on the bottom of the blade I'm not really sure what's going on here but maybe if I could find some way to eliminate this the performance could be improved even further so I've been doing all these tests with this power Queen 25 volt 100 amp hour lifep04 battery and this one's really nice because it doesn't cut out like all my other ones do with the other ones if you give it too much throttle the BMS trips and it does like an over current fault or something like that but this one I've been able to go up to like 3 500 watts and it keeps going so that's awesome so now we're going to have a little fun I've got this duct battery 12s 8p battery connected we're reading 49.6 volts we're going to see how fast we can go we're also going to see if these SLS props can handle the power and that's Full Throttle at 5000 Watts right there only 2.5 meters per second and the esc's are already going to Thermal fold back so when they get too hot the power drops and then makes weird noise is apparently but we can hit 5000 Watts for a little while so I just need to get liquid cooling going on these motor drivers have tubes in them for liquid cooling I just don't have it set up yet these also take up to a 20s lipo and these motors are rated for a 20s Max so in order to hit full power with this setup I need a bigger battery wow look at that thing what do you mean you can't just fdm print a propeller look how fast that thing is going wow someone owns that thing it just drives it around for fun I promise we're finished prop testing hope you learned something I sure did thanks for watching bye

Channel: rctestflight

Views: 1,795,206

Keywords: Toroidal, propeller, 3D print, 3D printed, boat, electric

Id: 93ZYL0GYw6E

Length: 36min 57sec (2217 seconds)

Published: Fri Jun 23 2023