Yeah, I don't wanna be mean to the guy, but I really don't see how the curved rectangles on the tips could be anywhere near optimal even for that design. I feel like they should be at least a little rounded in some way, right?

"9/10 chance of winning" *literally got beaten by every other submission this episode* gg, nenad.

@@mitchib1440 Perhaps he thought the chart was reversed, 9/10 chance of loosing? :)

Though I do wonder how that prop would have worked with more power and higher RPMs (assuming it survives that)

Time to short

Pun intended...? :D

​@@apacheandyyou beat me to it

I nearly clicked away and had to come back. Wonderful pun, bravo.

props, haha

props 😎

Dude same…

Wrong. Was a Spai.

@@evanray8413came here to say the same thing lol. That’s probably my military training and bias’s

@Juddly05 I'm just a skeptic. No training at all. 🤪

*_As a long time RC boat enthusiasts you get people come to watch no matter if it's raining cats and dogs outside and the questions never end._*

"so cool. but you doctor yet?"

"See. Look at the graph. I told you it would be bad."

And the huh... I guess it works, but why?

BAHAHAHHA this is gold

THOSE DUCKLINGS HATCHED THEY'RE FUZZBALLS ...yeah low reynolds number ain't shit if prop design is crap

And mock their underconfidence haha

i predict that in 5 years we send a probe to europa

you missed the bit where this was not only and RC channel but an RC aeroplane channel lol.

Honestly it feels like he saw how successful MajorHardwares user submitted PC Fan series was and said “hmm I can do this for propellers” either way I’m here for it

I am pleasantly surprised to find your channel and your testing. Always wondered what the best prop would be. Just fun to watch.

Right? I'm not even into RC stuff, at all, but I subscribed anyway. Fluid dynamics and homebrew engineering is more fun than it seems it would be.

You will be in a good position to appreciate it.

Curious isn't it. I'm similar. He obviously has a serious knack at making things we are NOT interested in interesting.....

Who TF hates water? lol

@@Johnnywhamo​​⁠water is generally always too damn cold and when it comes to low temperatures im a wimpy bitch xD

Fan showdown wishes it could be this good.

At least the fan showdown guy is not shitting on people with his superior opinions and it's just for fun

@@infernus6278 I feel like he was very objective. The results don't lie and aren't just opinions! And I feel like the prop you are probably referring to was given a fair chance, he even told him the angle of attack seemed too low beforehand! Also you gotta keep in mind how many different props (but also wings, hulls, etc) he has created himself, I love that he has some insight and gives a little hypothesis

I was also thinking fan showdown (Major Hardware) or Project Farm

@@jaspervandenameele4834 im not talking about that last objectively shit design, the whole vibe of the episode is wrong

lol good spot

hope he picked it up haha

Prop 43 is sitting on the bottom

Actually 12:07 It explains better what you were referring to.

@@derjoh1986 actually they were talking about a second fallen prop that's visible right before the cutoff.

So many creators drag us through every little side project painfully. I suppose it could still be interesting but there's a limit. I appreciate his judgement.

and the rose goes to the simpler is better

😮 Im a nerd now..

Pc fan design is another one that can get this crazy imo

@@extremechimpout I mean, we're watching a competition about boat propeller efficiency - so I mean, _we are what we are._ Might as well own it. Don't get me wrong. I don't mean it in a derogatory way, quite the opposite.

Lol, very apt description.

Making crowd resourced hulls is a lot of work and filament😀

@@vitsalava1251 I thought he did a video about hull design. Not a competition, but a video about it.

buddy, none of us are all thst technical. lol

Not true! Some of the viewers here are technical, and some are even experts in the field of fluid mechanics. This channel is great because it’s interesting and informative for many types of viewers. It’s awesome and cool a fun stuff!

@@pejoka nope. i call bullshit. we dumb; dumb as hell.

That weak hub vortex caught my eye, indicating the blades are operating at a very good lift to drag ratio. Nice design job.

​@danedmiston9673 thanks!

What if you added dimples like on a golf ball.

​@@FogGoblin Golf ball dimples are a kind of turbulator, you should go read up on how those work (it would take a bit long to write it all up here). Basically they're pretty situational, and only help when the flow is laminar and speeds are fairly low. Under other circumstances they actually increase drag. Boat propellers usually have various stuff (like the skeg and bubble generator) upstream of them that messes up the laminar flow into the blades anyway, so there's probably not much point using turbulators. Also this prop is spinning fast enough that it is mostly outside the range of speeds where they'd be useful.

@@nerd1000ify Thank you for reply. Last comment, what if someone printed a Prop that was more like a Driveshaft and have gears that are pushed by boat moving. Or why cannot you add a prop in front and in rear? I lack intelligence but I can beat you all in imagination.

Yeah. It's clear he didn't check rpms or only tested it for static thrust. Interesting idea, just not optimized for situation.

Kinda hard to imagine why such a supposedly “brilliant “ designer would miss the obvious scaling issue so badly.

I predict an inverse correlation

I think I have seen several other studies where longer length is thought to be more efficient, which is helpful for solar powered systems.

@@vahnlewis9749 certainly, the longer the wing the more of it behaves like the infinite 2D wing which is almost always far more efficient. The traditional theory is that vortex related drag (proportional to lift squared, thrust in this context) scales inversely with the oswald efficiency (wing/prop design) and inversely to pi * the aspect ratio

@@youngbloodbear9662 As an aerospace engineer, I would love to ask you a question about how airfoils work. I am a sailor by the way. There are two lifts on a wing, one is the Bernoulli, and the other is sometimes called Newton. Bernoulli suggest the lift on a wing relates to a vacuum produce above the wing due to the separation produced by the wing shape. The Newton force is the force of the wind pushing on the underside of the wing. I think both of these are involved in lift, but I think in many cases the Newton force is larger than the Bernoulli. Is there any reference that describes the magnitude of these two forces on wing addressing the factors of foil speed and foil angle?

@@vahnlewis9749 i don’t have a good paper to reference off the top of my head, but I can say very confidently that in most cases, most of the time, the ‘newton’ lift is significantly more important than the ‘Bernoulli’ vacuum based lift. What is really critical though is the difference between the surfaces, breaking it into components is just semantics, its the net pressure differential that generates the force. Its also important to note that if newton lift was the only thing that mattered, wings wouldn’t stall in the way they do, if the bottom surface were the only part that mattered, we wouldn’t care if flow separated from the other side, but in reality you drop like a rock. Even if the vacuum isn’t as strong as many would imply, that steady low pressure flow is still necessary for the higher pressure on the bottom to push against, because it isn’t *that* strong either. A good example is a big heavy fighter jet might have a wing loading of around 80 pounds per square foot of wing, thats only half a PSI total on average in level flight, and thats newton and bernoulli combined… even pulling maximum G’s that’s only 1/3 of an atmosphere difference in pressure. The reality though is that these simple breakdowns of newton vs bernoulli aren’t capturing the full picture. If you take a step back and look at the effect on the airflow, treat the wing as a black box, what you need to see is how much momentum is being imparted into the flow, and that force has to be reflected in the wing, basically just an abstraction of newton. When you do this, it turns out that you can back out a parameter called circulation which is equal to the lift. The more the wing causes the air to curve around it and change direction, the more force it generates, and thats due to both pushing from the bottom surface and from the suction over the top. This doesn’t factor more complex interactions with viscous flow and vortices etc but thats the gist. One last caveat is for highly supersonic objects, newtonian flow is almost perfectly accurate, the more supersonic the less these ideas of suction have time to really take any effect

@@vahnlewis9749 Lift is created by the difference of the pressures under and above the wing. It involves both vacuum above the wing and excessive pressure below the wing. But vacuum can have around 3 times more deviation from atmospheric pressure than excessive pressure below the wing, so the most of the lift is created by that vacuum. Maybe i didn't wrote it clear, English is not my native. So here is formula of what i meant: P_above - P_atmospheric ≈ - 3 * (P_below - P_atmospheric) It is important to understand that without pressure below the wing, there wouldn't be any lift so both create it and both are used in Bernoulli lift. And Newton lift is just excessive pressure below the wing which is included in Bernoulli lift

MARITIME RESEARCH INSTITUTE NETHERLANDS is located in Wageningen.

Wagon ninja?

@@Alex-zi1nb close enough!

Right! Here before Elon hires him for a high-level position at SpaceX 🙋‍♂️

Rounding the edge at the start of the vortex could help a lot by driving through seaweed too

Crazy I was going to comment that’s if you hadn’t 😂

why? what's at 13:04?

watch techingredients video about electric catamaran propeller. he did the testing and arrived at a 3 blade ccw pusher prop being the way to go I believe. i kept hoping one of the designs was going to be similar to that but none were:\

​@@tylerlaird91yet...

@@jumpsneak 😄

we nerds are more fun anyways ;)

Why?

​@@denisivanov1140more knowladge. I like to be a nerd when it comes to stuff like this. Also made a underwater drone. Multiple times 😁

Most patents are done in hopes of it being used somewhere else and owning rights

@@frankdobs But at least they should have even the slightest chance of being useful.

considering it was mentioned to be "quieter and more efficient than a regular drone propeller" im assuming this design was made with air in mind and not water. water really just is a different ballgame.

@@thegforce522 but it was submitted for a water challenge...

@@mitchib1440 yup, seems the submitter underestimated how vastly different water props are. it would also make more sense as to why the pitch was lower, and why the efficiency curve was going up. it is probably made for much higher rpm and lower torque applications.

It clearly couldn't reach higher speeds, anyway you can see it almost at plateau in the end of the curve, and with the "corrected parameter" calculated at the apex it was still dead last

@@8paolo96 Well, it was so clear to me that i didnt think to even mention it

Remember they designed this prop for the 400 watt motor with a target speed aswell, if it didn't reach full efficiency then it was badly setup for this motor. All props regardless of style or design need to be correctly sized (diameter and pitch) for the motor driving them this is standard in the boating world. Also given how badly the prop performed and the angle on the graph it should likely would never reach a efficiency remotely close to the other props, also note the design was intended for metal it should have been altered for plastic (knowing it was going to be printed) as it may not have broken but it may have been flexing altering the intended pitch angle and hurting the efficiency more. The final nail in the coffin for this design really is the flow, the goal of a prop is to push water backwards any water moving in any other direction is a huge efficiency loss and those swirling vortexs moving at the outer edges of the blade looked to be around 20% of the blade lenght a huge section of the blade that was effectively fighting its ability to push water backwards

The propeller on that motor couldn’t reach higher speeds, so how does the efficiency past that point matter if it is unable to run at those speeds? It did reach its efficiency peak for that motor.

@@DumbGoogle-yz9cr Resin is actually extremely inflexible, it will shatter with not much more bend than metal would. The fact it didn't break already tells it wasn't flexing, it was just so inefficient that it couldn't perform well enough to break itself.

It's so cool!

Looks like a Kelvin-Helmholtz instability. 😏 (I think I learned that from Veritasium ..)

If the airsped is below ~100 m/s you consider it incompressible as the effect is neglectable. The only real difference, apart from viscosity, is cavitation.

For that guy with the patent, the problem is somewhere else. Even for air, his propeller would be shit. You can compare it a bit to airplanes. He built a bipline-equivalent. Biplanes only advantage is structural integrity. It is easier to build them more rigid. That's why they were mostly used early on when materials etc. were not so advanced. The most efficient airplanes are gliders (yes, the concept of aspect ratio does apply to propellers).

If pressure differences would be negligible then cavitation would not be an issue, so your statement is invalid.

@@falcofranz5005 Well, happy to disagree. First, read my comment. I wrote, "negligible compared to that". I did not write "non existent". And what I wrote is true. Water is not compressible, while air is hugely compressible. Completely different in this regard. Cavitation is a very special effect. It only happens at a very low pressure, and suddenly. It does not happen at high pressure. And it happens at a special case. In all the other pressures, and pressure differences it does not appear, and does not have any effect on the effectiveness of the propeller. Like 99% of the time. While air pressure differences affects the effectiveness of the propeller 100% of the time. So it is truly negligible compared, and it can be handled very differently than other aerodynamic effects.

I think we both agree that the flow dynamics in air and water are very different, since water is incompressible and can undergo a phase change. Also the viscosity is different so the production and dissipation of turbulence is also different. Also the speed of sound is higher in water so shocks are unlikely to appear (cavitation will occure before that). What we disagree on is the term „negligible“, which I think is wrong here, because cavitation is a phenomenon that indicates drastic pressure drops. And since cavitation is very lossy it is in my eyes a defining factor and not a negligible effect.

thinking the same thing, now i have to go check that out see if anything's new.