How Hydrofoils Work

In this video we explain how hydrofoils work. Believe it or not, most of the common explanations of how hydrofoils work are incorrect or incomplete at best. We'll take you through the misconceptions and share an intuitive, easy to understand explanation of where lift comes from. Enjoy!
Special thanks to following channels for making their content available for re-use under creative commons license:
• Dock Step Off Foil Rod...
• Aquila Hydro-Glide Foi...
• Stealth Volga
• Riding small boards is...
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[@sevtecsev]

Fascinating, well presented. And to think, I put a kayak up on a submerged foil around 1960, but I could not paddle so fast for long. I still remember tying a line to the kayak and having a person tow me onto the foil for a sustained ride. As soon as the kayak popped up on the foil, he went head over heels as the foil abruptly reduced the load on the tow rope as it lifted the kayak above the water. I went on to fly possibly the first of what is called the Rogallo Wing and it"s motorized form, the trike. I could have stayed with the hydrofoil!

[@MegaPaul57]

with dc motors and batteries of today i am sure a double v surface piercing foil on a kayak would work with the motors at the bottom of the v but i know i will never get round to it but at least you tried bravo

[@fredhubbard7210]

This video confirms what I have thought about lift for about 50 years. I never believed the first explanations, and this seems to me to be so obvious. Thanks! I feel vindicated.

[@deanaoxo]

I've been working with wings since the late 80's. We talk about this constantly, and i've never seen a better, clearer explanation. I kept wait for you to leave something out like AOA, but nope, covered, not only covered but gave the ratio's as well. Will be bookmarking and sharing this as the number one best explanation for how wings work, especially when thicker skulls insist on arguing. Brilliant.

[@OurKiteLife]

Thanks Dean

[@doodelay]

I was extremely impressed with the quality, presentation style, editing, and thoroughness of the video. You guys are going to have hundreds of thousands of subs one day, and honestly ya'll could broaden the target audience and you'd 100% succeed.

[@OurKiteLife]

Thank you 🙂

[@vichy7661]

@@OurKiteLife the announcer voices confidence, poised yet delicate, carefully refined with hard facts, this girl knows what she is talking about, in contrast to other outta touch who simply voice read words.

[@protovision2010]

great video! re: planes flying upside down, fwiw, when flying an RC model plane upside down, you typically have to add a bit of elevator angle to counteract the 'downward' lift being generated by the inverted wing. Probably similar in real life.

[@jgarbo3541]

Inverted flight also uses Newton's 3rd law, not Bernoulli Effect (or you'd crash). Wing's optimum Angle of Attack is ~4-5°, so when flying inverted you also create a 5° AoA by pushing forward on the yoke, elevator down ( now "up") to point the inverted wing upward. Takes practise because it's counter-intuitive. (Old PPL pilot, C152, and engineer).

[@walkman146]

By adding down elevator when inverted, you are effectively increasing the angle of attack, which then creates lower pressure and lift on the bottom of the inverted wing. Inverted R/C planes that do not have symmetrical wings do not fly great inverted as you are often flying on the verge of a stall because of the angle of attack.

[@SuperstarFx]

This video was clearer than any fluid mechanics textbook in the world

[@koonzipher4692]

Thank you, I have never quite understood hydrofoils. I can only learn by seeing, so descriptions are just words that mean things to everyone else. You taught someone something today

[@salmiakki5638]

Bell didn't invent the telephone, he just marketed it, Antonio Meucci was the inventor

[@marcofrancioni1155]

he didn't invented the telephone neither the hydrofoil since Forlanini and Crocco already build 2 different hydrofoiling boat in 1906 and 1907 while Bell arrived in 1912

[@mucsalto8377]

@@marcofrancioni1155 All great inventions had been made in the "greatest country of the world" - where else?

[@Chris-P]

Baal ....

[@ammakko]

Meucci FTW

[@krusty1974]

@@mucsalto8377 LOL

[@zbeekerm]

As a fluid mechanics PhD and Aerospace engineer I went into this video with trepidation that you’d point to an incomplete/flawed explanation like Bernoulli’s equation which is a specific simplification of the energy equation that can be made under very specific circumstances. I was extremely relieved to see that your explanation focused on conservation of momentum an generally agree with almost everything you said, well done! My only concern is the assertion of a lack of understanding or consensus among scientists and engineers-the bottom line is you need at least all 5 Navier Stokes equations-conservation of mass, conservation of x, y & z momentum and conservation of energy-to fully describe real fluid flow around 3D foils. It’s very complicated and usually impossible to solve with pencil & paper but there is a general understanding.

[@krusty1974]

Nice video. Must point out that the ones well described here are not “different theories of lift” instead they are individual explanations of the various forces acting on a wing all together creating lift.

[@cjames3029]

I know bro but it's a chick doing it so don't expect much lol

[@davem1966]

I'm an engineer and I learned something by this video - very impressive

[@OurKiteLife]

Thanks! Happy to hear :)

[@danlee944]

OMG! The first video I've seen that actually get's the physics of wings correctly! Well done!

[@brianlubiszewski3181]

Much, much, more information then I set out to look for... but I watched it all because it was engaging, informative and well put together. 👏🏻

[@matthewkramer8613]

If you ever try wakeboarding, on the take off, it's best to point the board to the side a bit or you will be fighting the high pressure force from under the board when pointing towards to boat. The shape of a wing can exaggerate this effect to generate lift. Nice video on this topic! In science I think air and water are considered fluids.

[@marcofrancioni1155]

For any Fluid Dynamics expert The vorticity generated by the boundary layer deflects downward the flow and for the conservation of momentum the wing is pushed upwards NO DEBATE

[@kite666G]

Keep going guys! At this rate you'll be the number one kite channel in no time... Thumbs up! Great video.

[@OurKiteLife]

Thanks so much 🙂

[@inthefuns]

"We talked to aerospace engineers and we watched University lectures on fluid mechanics"... you guys are truly next level!

[@joeytilbury3400]

@Sky Man You sound like someone whose very insecure in their intelligence. You dont have the capability to actually understand the science and the math so you start making absurd claims with no evidence backing it up. You're so desperate to convince yourself that you have it all figured out and that the people who were able to actually dedicate themselves to science are a bunch of fools. How sad and pathetic lmao

[@gerhardkutt1748]

No they're not next level. If they talked to aero space engineers they talked to the wrong people, because we are talking HYDRO foils and NOT air foils. Water is incompressible and so using the air foil analogy is TOTALLY incorrect. If they talked about an aircraft in supersonic flight, they would be closer to getting the technical explanation right. Ignore everything she said except for the part about changing the flow direction of water, because that is where the lift occurs. She forgot to mention you can never have just one foil either. They always come in pairs. Leading foil and trailing foil to maintain balance - without 2 foils, instability would occur.

[@russelldawkins9094]

@@gerhardkutt1748 Thank you for injecting a little reason into this blur of confusion, including that of the presenters.

[@tempestive1]

@Sky Man dude, have you ever even scienced? Every word you posted increasingly showed how unaware you are of how it works. You, my friend - and I don't mean this perjoratively - are a textbook case of the Dunning-Kruger effect. And on a side note, doing research shouldn't not be something commendable, it is expectable... If you believe anything without sufficient evidence, you're being irrational *by definition* . I'm not educated on the matter and don't know anything about @Gerhard Kutt 's comment, but this seems like a good demonstration of how easily we can fall for the argument from authority fallacy, and ignore the fact the people who research things "for us" are also fallible.

[@crossleydd42]

@Sky Man Glad you liked it!

[@ArthurRosaTV]

The best and informative kite channel in the world.

[@lindsaygoodwin3140]

Excellent video! I'm about to move to a beach town with a small season for surfing, windsurfing and kite boarding, so I've been looking into wing surfing. This video is very informative and clear. Subscribed!

[@leliasnowdon2668]

nice presentation made it easy for old guys to understand

[@RickMentore]

Your explanation is compensative. I was just looking for an explication on this subject after viewing the America's Cups yacht races. Thank you.

[@blackbluerray]

Thank you for the video!!! Was really searching for a good explanation and you did it. Can’t appreciate it enough

[@OurKiteLife]

Thanks, glad you liked it!

[@rdatta]

Excellent narrative and explanation. Really well done. Would love to see a 2nd part dealing in more detail with upside down wings and flat wings.

[@alexforbes7440]

Thanks for this great explanation. The Bernoulli explanation I was fed at Engg school caused a lot of confusion as it is a complete abstraction from intuition and every day experience and a very inadequate explanation as you point out in your examples which could also include canvas wings. The top of the wing induces suction which in the extreme case in a liquid medium results in Cavitation . This explanation links lift and Cavitation. Great Job and thank you.

[@rebeccacarlson9166]

A really great explanation of how this works!

[@uberdash007]

Representation great choice of words

[@IhorVasutyn]

Blow below the paper it will still lift :). but the speed below is higher :). It is all about the angle of attack and changing the location of fluid. Water pushed down so the wing pushed up. Great explanation

[@watzbaer]

Excellent content. So valuable and well researched. Thank you

[@JamesLamb]

I feel shortchanged by my physics professors! But I never went too deep into fluid dynamics.

[@rembeadgc]

The longer we live, the more we know...if we're open minded.

[@getawaydriver5363]

If you have discernment to sift through the bullshit helps too. Gravity is still just a “theory” and it’s awfully selective.

[@mikebastiat]

People never figure out government is evil though..

[@davidmikoczi]

This is well done! Entertaining and educative. Thank you

[@OurKiteLife]

Thank you 🙂

[@KiranKumarBokkesam]

When you watch this video you almost feel like you understood and then when you watch the lift foil surfboard and the Pegasus, you think again if you really understood it

[@jimpike7445]

As a pilot for 56 years, I don't think I've heard a better explanation!

[@paulsandkuijl]

Excellent explanation! Really awkward that scientists are still debating why lift is created! The Bernouilli explanation was the one that we got explained at our Uni for Aeronautical Engineering. And a thing called Lifting Line Theory. One thing you might want to add to your video though is the Coanda effect which explains why the air 'sticks' to the curved top of the wing and gets thrown down creating lift by using Newton's 3rd law. Great work!

[@JamesDriver40]

No discussion of circulation theory and starting vortices? After all, it is the explanation that ties in with the magnus effect (lift generated by a spinning cylinder or sphere). It is also the theory of lift presented by Whidden and Levitt in the 2016 edition of "The Art and Science of Sails" published by North Sails Group LLC.

[@keremsahin5482]

Many thanks for this explanation video. Have a nice day.

[@qwertyTRiG]

Well, that was enjoyable. I follow a lot of science explanation videos on KZbin, and not any kite surfers, so it's interesting that KZbin knew to recommend me this video.

[@mikefromspace]

Aircraft don't fly upside down efficiently or nearly as fast. The 22.5 angle (median of your mention) is used also in anti-radar/radar absorbing surfaces, as well as sound rooms to cause sound to cancel itself out. Either inward or outward angles do this with sound and rf, or in the application of golf balls; a specfic angle of 22.5d in the convex pit forces air pressure modulations to resist one-another using a 3 phase transition of pressure shared among points. In this case it's a plane against the water itself. The reason 22.5d is naturally vexing to white noise, or water flow just the same, is because of simple geometry regarding all forces in a universal rule; the differences of negative and positive spaces become interlocked among a system of flows to resist penetration by outside flows by working with the flow just enough. 22.5d x 8=360d. It may not seem like a 1 dimensional flow of water pressure could be applied to the 8x geometry, so is it just coincidence? In elementary particle physics, superconductivity was never realized in geometry until I wrote a paper on this in 1996 and Egor Babaev discovered this also on supercomputer 10 years later appx. (ref: type 1.5 superconductivity) My Grampa used to race hydrofoils on Lake Washington. I can tell you, the longer the boat, the safer it can operate at high speed without computers. It is also possible to use a gyroscope, and the mere flow of water can be your computer. There's always a better design for something somewhere just when you think you've got it figured out.

[@kaf2303]

Interesting, I wasn't aware their were multiple theories on lift. thanks

[@johnbode2756]

Both a flat and curved wings can produce a pressure differential, but the curved wing is more effective in one direction. This is why a flat wing is just as effective whether it’s right side up or up side down. The curved wing is not as effective when upside down, but can still produce a pressure differential.

[@kloug2006]

Thanks for educating us.

[@andrewp7566]

Wow! exelent works! Well done. As a aviation engineer a jast may ad that airplanes can fly down turns becouse the wing has special set of angle off attack. And you can believe or not but a lot of acrobatic airplanes has symmetric aerodynamic profile. So very professional video! My congratulations! I spent a lot of time choosing my fist hydrofoil 633 Moses Onda. Hydrofoils exactly like aircrafts all has own shape and purpose))) and the flight filings so exacting isnt it ?)

[@OurKiteLife]

Thanks for your comment Andrew. We were actually contemplating on trying foiling with the hydrofoil upside down, but decided not to bother as when we dug deeper only certain planes can fly upside down, mostly with symmetrical wings.

[@BooRay1]

great video :D Coming from aero background.. dont be too concerned about how planes fly upside down.... because acrobatic planes have simetrical shape while cargo planes and passanger airliners have more clark-y type profile which generates more lift when flying horizontaly...

[@OurKiteLife]

Thanks for the insight!

[@yinkaoreoluwa9654]

Great video; I appreciate the fact that you took us through the different explanations and research points. Thank you.

[@olliefoxx7165]

Alexander Bell was a prolific inventer. There were so many ground breaking inventions in the early 20th century that are still considered novel today. Impressive minds are found in every generation.

[@miguelvasquez7022]

Hydrofoils seemed like witchcraft until watching this. Thanks for the clear explanation.

[@adamdennis2936]

I was thoroughly excited watching this.

[@ArbitraryOnslaught]

This gives me ideas. Thanka

[@jens6398]

Ever held your hand out the car window, trying to make it 'hover' in mid-air? Then you know how wings work.

[@haveagreatday8248]

yeh dogs do it with their heads all the time. It's also fun but just be careful.

[@malakiblunt]

the (4th) angle of attack explanation is the correct answer as it explains how planes fly upside down,how symmetrical aerofoils work,and also how propellers (air and water screws ) , wind turbines and sails work- And it is also the correct explanation of Newtons 3rd law a wing weather it is in air or water is producing thrust, just like a rocket, by accelerating a mass downwards , All aerofoils do is increase the efficiency of this process by reducing drag , (they also have an important effect on controllability of the craft) The confusion is caused my the imaginary 'lift force' when in reality its just Thrust

[@BrentWebber]

EXCELLENT EXPLANATION.

[@maniac_24-7]

Your statement "it is not clear why wings generate lift" is true, if and only if there is only one method creating lift. But as you mention, there are more than one mechanisms. When planes fly in upright (normal) configuration, the wings generate lift by Bernoullis principal, upside down they create lift using particle kinetic by flying at a significant higher angle of attack. You can see it in any biplane airshow video on youtube.

[@factChecker01]

This is more accurate than a lot of aerodynamic explanations of wing lift. But the "flow turning down implies lift" does very little to explain in detail why it is working. The simple answer is that there is no simple answer. Calculating the lift on a wing requires detailed, piece-by-piece, tracking of the flow in a huge computational fluid dynamics (CFD) calculation. That is why wind tunnel tests are still used to experimentally measure the lift.

[@peergynt9852]

Great video should be a science channel

[@Penncroff]

Very nice video! It would have been nice to put your sources in the description too :)

[@lumrahalam8267]

Wow very simple design.

[@bojames7841]

Well produced video I was looking for something that explained hydrofoil but I kinda think the airplane lead was unnecessary. There are major differences with the interactions of rudders, ailerons & wings. I get that they are wing like and provide lift. I would have liked to hear what some challenges that builders had to overcome before finished products. But it still helps me understand more

[@benjaminlewis671]

Bernoulli, Venturi and Reynolds are my favorite scientists because they explain exactly how fluid mechanics works in everyday life.

[@bradbuckner9496]

Great job.

[@dr.s.p.]

It can fly upside down because you still have ailerons and other controls to achieve the necessary angle and therefore, the necessary lift while upside, only in reverse.

[@k.chriscaldwell4141]

Here is THE explanation of wing generated lift. As a wing moves through a medium, a perfect vacuum is generated at the surface of its backside. This vacuum diverts and accelerates the medium downward along the wing’s backside. This diverted medium creates a low pressure area above the wing that pulls down, “scoops,” and accelerates more of the medium from above down and along the wing’s backside. All of the scooped up and accelerated medium is then shot off and down the wing’s trailing edge. Opposite and equal reaction: Lift. (In some videos of large planes landing, this action can be observed.) Lift is Newtonian, not Bernoullian. However, the low pressures as described does permit the use of mathematical approximations with Bernoulli formulas when designing wings. Sidenote: It can be further deduced that most of the energy that sustains an airplane in flight is extracted from gravity*. Evidence of this is that wing or rotor equipped aircraft have glide ratios or auto-rotation. And then there is the autogyro. Hydrofoil wings probably harvest energy from gravity as well. *Binal-Dynamics. Also seen also in Tensegrity structures.

[@bArda26]

Appreciating your hard work!

[@marsianmynul1824]

amazing description, I really like this kind of video. good job to the team who made this. thanks

[@3DLasers]

You can make a flat sheet a wing if the force of propulsion be it gravity or thrust against the wind is strong enough. It's called shearing which is how jets fly upside-down...

[@angellestat2730]

Better explanation that the ones you can find in the best physics related channels.. really good work.

[@ben3989]

just look at the crazy amount of air a helicopter displaces downwards. A helicopter is the best visual display of what lift is.

[@nrlad2549]

This came out for my spm 2021 . So funny man😂 😅

[@OurKiteLife]

Can you elaborate? We’re curious :) thanks

[@nrlad2549]

@@OurKiteLife well SPM is the important examination in Malaysia tht all malaysian must take it to continue study or to enter the Uni. This thing came out for our physics paper in section C(essay) tht we must answ it. Well , i'm just use the bernoulli principle like aerofoil bcuz i dont know this thing exist. Not so familiar in Malaysia. I said it funny bcuz imma little bit confuse man😅

[@maurolimaok]

I loved the the video and, I need to say, what a beutiful tiny eyes girl! She is mesmerizing! :) Hope this channel grows a lot!

[@OurKiteLife]

Thank you 🙂

[@XMarkxyz]

The telephone was invented by Meucci, Bell was just good at stealing the idea while he worked in the patent office

[@northernwing]

Amazing knowledge shared. Thanks 🙏

[@moroccangladiator]

Thank you. From 🇲🇦

[@Kimbumbala]

Super informative!

[@leonardo8461]

As an Aerospace Engineer I can tell you guys...it's real magic, trust me

[@stokakrishna]

Love watching your videos!!

[@ankleshsingh2964]

Thanks from my heart. Very knowledgeable information 🙏

[@maximrogov7667]

I think that is best explanation for foil.

[@JetSurfingNation]

Great video, thank you for research!! But I can’t believe you did not even mention efoils :)

[@OurKiteLife]

We almost did just had no b-roll and the sentence was getting long. When we mentioned foil being powered by engines, sail or momentum. Now as I am thinking about it, e-foil would classify under engines... :) But yeah should of mentioned

[@ForOdinAndAsgard]

Sails are vertical wings and we know for a fact we get pulled forwards and are not pushed.

[@justcommenting4981]

Nice explanation. Well done.

[@robertmedina3982]

If flat then force is applied to the surface like a brake but when at an angle allows the wing to ride over the force of breaking. So it’s riding on a surface regardless of how deep it is.

[@brunosantos3852]

Wasn't Graham Bell the real guy who invented the telephone, but it was the italian inventor Antonio Giuseppe Meucci (1871). Graham Bell patented his telephone version just after Meucci's in 1876.

[@puo09]

Wow you really did your homework...Wonderful.👏 Thank you !!

[@dandil]

ok I'm going to try to make this as intuitive as possible: the momentum transfer theory is the most correct, just incomplete. A wing, even a flat one, will generate lift due to its angle of attack causing a downward acceleration in the fluid medium. The reason for the hydrofoil shape is to allow the flow on top to stick to the top surface; a sudden transition like on a flat plate will cause the flow to separate away from the top surface, creating massive drag. The gradual slope of a foil allows the flow over the top of the wing to gradually accelerate downward and stay along the surface, rather than separating.

[@corfudreamscapes5369]

Finally, I found an explanation! Thank u.

[@vlaaady]

I rode those "raketss", they are fast and cool!

[@Pahabarabaha]

Next video must be about soft wing of the kite flight principles. How does aerodynamic work on open wing of the kites! Please doit for all of us!

[@homeslipper]

Think parachute. Try jumping off a tall structure with an umbrella. Same effect.

[@stevenmeans4881]

This is a similar engineering concept when desiging skyscrapers. Windows that high are exposed to high winds on the outside which create a vacuum (low pressure) & the windows need to be able to withstand that.

[@propheccy]

guys, this fluid dynamic is called the Coanda-effect. It's why airplanes fly and why this thing works as well. you did all this research but failed to name the effect responsible for all of it lmao. cool video either way...

[@maximrogov7667]

Remember you did video about kite inflated with helium, I think you should do video with one kite filled up with helium and one filled up with heavy gas.

[@OurKiteLife]

We're thinking of comparing kites of different weights (heavy vs light - think Aluula material), to see if there's any difference

[@MultihullCentral1]

Wow that was comprehensive great job

[@belledetector]

Incompressibility and viscosity are the two main factors setting hydrodynamics apart from aerodynamics, but in principle they work the same as air is a gas, and gas is a low density fluid.

[@ShaneHarderPhoto]

Thank you, great video. Question though, for a foil board, you mentioned the rear wing adds stability. Would you be interested in doing another video showing the fluid dynamics of the rear wing? Or how the front wing affects water currents and how the rear wing reacts to those currents to keep the board stable? I'd really really love to better understand these concepts to help me understand better what front/rear wing combo I want to either buy or make. Thank you so much!

[@ebuzertahakanat]

i came here to tell ackchyually but it seems they were expecting me, well played

[@stingerboardsfoilswings739]

great explanation

[@Chris-P]

Very cool, thanks!!

[@petes9878]

I missed seeing 'the wings' which are installed on race cars, which I suppose, are intended to achieve just the opposite of what airplane's wings are used for. I can only surmise that the trailing edge of the race car's 'wing' must be positioned higher in order to accomplish downward 'lift'.

[@NeilSeaver]

TLDR : stick your hand out of car window and it’s that

[@lllPlatinumlll]

The second explanation is correct. The reasons stated that supposedly disprove this explanation are incorrect. It is essentially an energy harvester requiring more and more oncoming fresh molecules to harvest energy from without fresh energy it sinks.

[@aaronchu0427]

Thanks for sharing!

[@TylerKaraszewski]

This is great. I think I've done most of the same research you guys did to make this video, and this is probably the best simple-ish explanation I've seen. Everything else is either so simple as to be wrong (usually covering just the first "equal time" idea from this video) or requires a math degree to understand. You guys did a great job with this. Also, you got my friend Rod downwind foiling here in the Gorge in there, which is cool, too. :)

[@OurKiteLife]

Thanks Tyler. Good to know his name now, Rod, as we used creative commons clips in this video. That particular clip I believe was from foil buzz

[@TylerKaraszewski]

@@OurKiteLife Rod (with a 'd' 😉) Parmenter.

[@CucamongaGuy]

aw man I was about to sub but then I found it this isn't a science channel. Damn good video though