How to Pump a Hydrofoil

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4 | Flite Performance Electric ($13,700)
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We’ve tried 300+ foils & have shared our experience in 100+ videos. Our recommendations are based on our desire to promote the best products. When viewers use our links and coupon code, we earn a commission. We have established a long list of affiliate partners. This allow us to earn a commission from the sale of nearly every brand. We believe this helps to eliminate any bias from our reviews and recommendations. We want to be transparent with our viewers, so we disclose our financial interests. Wake Thief has affiliate / financial arrangements with AXIS Foils, Takuma, Fliteboard, Beta Foils, Foil Drive, MACKiteboarding, REAL Watersports, Green Hat Kiteboarding, Bbtalkin, and Vibram. The above links are affiliate links, which mean we earn a commission if you purchase through our links. We thank you for your support of our channel and mission.
Safety Warning:
This sport is dangerous. Please be safe. We’d encourage you to thoroughly review all product safety material prior to trying. If you don’t feel safe, do not proceed. This sport is not as easy as it looks. It took us many hours of practice, but we enjoyed the journey. Please use a CGA life vest. Please wear a helmet to protect your head. Please wear a wetsuit to protect from cuts from any sharp edges. Please proceed at your own risk. We review products and share our own personal experience. If you rely on the information in this video, you assume responsibility for results. Wake Thief, LLC.
We want to figure out how to fly forever, but to do that we need to understand how a foils works, how to redesign a foil to reduce its power demand, and how to pump efficiently. It might be possible to fly forever on a hydrofoil! We enlisted the help of some friends: Eirik Bockmann and Todd Reichert. Eirik has a PhD in Hydrodynamics and is the CEO of Wavefoil, a company producing hydrofoils for large vessels. Todd Reichert is an Aerospace Engineer, flapping flight expert, and a celebrity in the human-powered flight community. In today's videos, we share some of what we learned on our journey to figure out how to fly forever
To learn more about Todd Reichert & the Aerovelo team, please visit aerovelo.com.
Kinovea is an open source project, and can be found at www.kinovea.org.

[@andylitespeed]

Just had the floor of our 10hp inflatable catamaran repaired so when the sea state allows we will be ready to get into some tow/pumping. Although we WingFoil, in offshore conditions we get lulls when there is no wind and it is always fun to see how far we can get by pumping till the wind fills in again. Keep up the great work!

[@patterrr]

I love how technical this video is - you know exactly how to communicate with me!

[@WakeThief]

Ha! Glad there's another person on the planet who thinks this way! Once I fly for the first time, I knew I was going to have to go deep ... it was only after a two years of using it, did I realize that I didn't really know how it worked.

[@buffharrypjoter2277]

You deserve way more subscribers for the work you put into these videos. As a kitefoil competitor from a national team getting into pump and surf foiling, I would have never thought about getting into so much technical detail. Thank you for providing so much useful info!

[@WakeThief]

Thank you. I really enjoy learning and sharing what we learn with an audience that cares to watch it. Comments like this is the fuel that keeps me going. I sincerely appreciate it.

[@dtbre]

Awesome video! I loved the in depth analysis. It's my goal this year to build hydrofoil setups, rapid prototype different configurations and learn as much as I can through research and experimentation. Keep up the technical content!

[@WakeThief]

You're welcome. Thanks for the comment and let me know if I can help.

[@perculated7666]

Let me know if you make it, I'm trying to get my first foilboard I live in a little town with HUUGE lakes. I'd love to buy one to foilboard across the lake to the beach. People would love it here!

[@nathanallen6411]

Thank you! I love your science based approach, breakdowns and encouragement. Don’t currently foil, but would like to.

[@WakeThief]

Hi Nathan! Thank you. When you're ready to pull the trigger, I'd be happy to help you. [e-mail]

[@colomacountry]

Man you are leading this foil sport into a whole new era for mankind..awesome very technical videos. You have some smart friends in your corner. Good luck on your research and any new vids!

[@WakeThief]

Thank you so much. The journey has been so much fun. And the journey has brought some amazing people out who are interested in figuring this out. Please stay tuned! More good stuff coming, I promise.

[@user-nu2pj2ch7t]

Great video! Hydrofoil surfing is still in its infancy, however individuals like you pushing the envelope will lead to innovations and hopefully a fully autonomous foil design free from boats or wind using only pumping. I can’t wait for that day!

[@WakeThief]

That’s awesome! Thanks so much for taking the time to leave us this inspirational note! I’m glad we’re not the only ones inspired by this future!

[@REALmattnuzzo]

Nice tech video. Some good info in there. I found the most valuable thing I learned on any foil is getting the wing into the pump zone. The closer the wing is to the surface, the less drag it has and the more efficient you are. There is a sweet spot that is just under the surface where you can put out a lot less effort and get a lot more glide. Someone told me when I was learning to pump that water has weight that grows exponentially as you go down in the water column which makes sense when you feel how much drag the foil has when it is too low.

[@WakeThief]

Thank you, Matt. I love what you guys do at REAL. I’ve been a long time customer. In fact the board I ride in this video (and many videos) and my first pumping foil were from REAL. Your video reviews are great, covering so many products. I’ve learned a lot from you in these videos. Id welcome the chance to meet. I can be reached at [e-mail]. Thanks for the comment.

[@binchicken8871]

Thank you so much for the time you have put into this, very helpful

[@WakeThief]

Thank you for taking the time to leave a comment!

[@matthewcosta3343]

You are a legend!!!! This is my favorite video of yours yet!

[@WakeThief]

Ha. Thanks, Matthew. I think it's my favorite too!

[@hatsbythe100]

with the help of your vids, I am now up to about 35 seconds of pumping. I used to pump on a 85 cm mast from Armstrong, now, with your advice , I moved to a 72 cm mast and got alot more efficiency and speed , The 1850 cm 2 front wing that you trialed is also great and I am getting better. Slowly. I set up the sling shot ( some 12 hours of set up and trails ) , similar to your set up and so am doing about 10 sessions a day. Getting fitter and slowly longer sessions. I am a 53 old surfer/wake boarder so am aspiring to get up to 1 minute and with your help its getting better...Will send some footage in soon. Thanks again for all your tips. Andy in Oz.

[@WakeThief]

Well done! I'd love to see a few videos. Maybe one from a few weeks ago and recent one. Progression is always amazing.

[@surfdocsteve]

Great analytical video. Technique is the key to an efficient pump. I know I have increased my pump time by double with that alone. Then next biggest factor is one's endurance. That's the biggest limiting factor. I used to run 100 mile trail runs so endurance can be achieved but it requires a lot of commitment or genetics. Equipment makes up for one's lack of ability and endurance, but in a very limited fashion. Training is the way to increase your time. Doing land exercises may help but nothing is as good as the real thing. Great video!

[@WakeThief]

Good to hear from you, Steve! I think you're right. No amount of training will overcome technique. I am quite sure the difference between good and very good technique is 1min of pumping. After meeting Todd and Eirik I learned that there's a term called propulsive efficiency, and we think it can swing pretty wildly if you don't pulse at the right time and relax at the right time. It all happens so fast that it's easy to make mistakes. Thanks for the comment. I hope you're well.

[@pieterdutoit5596]

Going well mate. Keep at it, lets see 10 minutes of pumping!

[@WakeThief]

It’s my dream for 2021. Working hard to make it happen. Thanks for the comment!

[@jakubdudek775]

Best pump foil analysis I've seen so far on the net

[@WakeThief]

Ha! Thanks Jakub. Let me know if I can every help. I so appreciate the comment.

[@evanvangelis4907]

Congrats - very insightful!

[@WakeThief]

Ha! Good to hear from you, Evan. Thank you.

[@steinerikgabrielsen2988]

More great instruction for my students - thank you. The physics reminds me of pumping transition in skate/snow board halfpipes. Watching you isolate the variables made me wonder if holding 1 kilo weights in each hand would increase the force generated with your arms up/down motion.

[@WakeThief]

Ha! It’s a great idea. I haven’t tried but I do think it would work! Thanks so much for taking the time to write

[@tommarello01]

I wish more youtubers would present in this manner. Good luck with your goal and here's looking forward to following your progress. Cheers !

[@WakeThief]

Thank you, Tom. I sincerely appreciate you taking the time to write this to us. Very kind of you. You’re a good guy. Thanks again.

[@tommarello01]

@@WakeThief No worries at all. All the best!

[@10GOLDENWOOD20]

Incredible! Thank you!!!

[@jaydee1020]

Science! Subscribed and thanks for sharing your research.

[@WakeThief]

Thank you so much, Jay!

[@learntofoil9085]

I teach foiling and agree with most of what you demonstrate. I believe that the weight of the rider and board play a larger role in the drag formula.

[@WakeThief]

Thanks for the comment! Yes. I totally agree. The heavier you are the faster you need to go. I’d appreciate your thoughts as I continue to make videos.

[@freesurfa9791]

Great instruction here, well done

[@WakeThief]

Thank you!

[@duneme]

Very interesting! I can see this as an Olympic Event as it seems like it does have some physical strength to it and I could see a Race between people occurring!

[@WakeThief]

You’re totally right. Surfing is now in the olympics. Maybe 4 or 8 years from now.

[@christoph4333]

I loved it .. great video ... very interesting ..

[@WakeThief]

Thank you. Christoph.

[@HendoRising]

I get to fly a few times a year behind my buddies boat and BOY... am I hooked. Thanks for the very detailed video. More technical data please. The software video analysis of your pumping is really interesting. From a mechanical standpoint there is a lot of cool things going on. I love seeing the footage laterally stabilized. The whole board and foil-body (wings+fuselage+mast) move in an elliptical fashion. As you "drive" and "float" the foil-body swings forward, and as you "climb" and "load" they swing back. The rear foot and mast board connection area seem to be the central pivot of the whole system of motion. Makes me interested to design a mechanical system that mimics this motion. I'll be loading your video into Kinovea myself. Excited for more BETA foil and foiling videos. Hendric from Germany

[@nathanshields9665]

Super cool! Hope u get there

[@WakeThief]

Thanks, Nathan. I appreciate the note. Still a lot to learn. I wish there wasn't as much to learn and we could just do it.

[@toranaga22]

@@WakeThief but the challenge is the fun part right? I was just thinking the other day, why is foiling so fun? because of the flying feeling and the challenge of riding it. Awesome videos by the way! watched almost all ur vids when i was starting!!

[@WakeThief]

Thanks Toranaga! You’re totally right. It feels much better than it looks. The challenge is certainly fun as well. Thanks for your kind words.

[@richardmatison3591]

This is awesome! Re: the chart at 1 minute. It would be interesting to see if a coordinated elite cyclist or runner could achieve with sustained power of over 400 watts compared to us mortals in the 200-300 range. Lionel Sanders has some great clips. Thanks for delving into the detail Wake Thief. I'm try killing the power on my foil kite as an intro to this.

[@WakeThief]

Thank you, Richard. Appreciate the comment. I think you’re right. I’m, by no means, a good athlete. I think an elite cyclist could probably pump for 20+ minutes with existing foils once they get the technique down … that’s the key. The propulsion efficiency needs to be learned but I have no doubt it can be!

[@franciscorr6396]

Like all the comments, great video! This really helps explain what is going on and how to pump, and the video is really well edited and produced. How did you measure the pressure during the pumping phase? Super interested to know how you came up with these figures and so precise. Keep up the amazing work, really interesting field, mixing science and engineering with weekend fun.

[@WakeThief]

Kinovea is a kinematic software. If you know the mass of limbs and how they accelerate / decelerate you can calculate force vectors and add them up. I was surprised how well it worked. Todd is a genius. thanks so much for taking the time to write a comment. Super kind of you. If I can ever help, please let me know.

[@SANTACRUZDRONES]

Great video. Have you tried a mini trampoline to simulate pumping? I'm wondering how to practice this when not on the water.

[@WakeThief]

I have not, but that's a great idea, Alex. I have a feeling cycling and squats are good training exercises.

[@maca5645]

Wow!,first in depth analysis of the pump i have seen.Great job. I am on the edge of "getting it".I can pump about 10-15 strokes but i still do not know what makes me loose it or not :) This vid will help a lot.Thx! BTW, that optimal pump speed you show in the graphs...is it related to the best Glide or best L/D ratio?

[@WakeThief]

It’s a function of min power of all the drag added up. Some of the drag goes up with speed (viscous drag) and some goes down (induced drag) so there’s a sweet spot. Unfortunately it’s not easy. We see I’m going a bit faster than the min and we think it’s to play it safe and not be so close to the angle of attack in which the foil stalls.

[@FoilingFrenzy]

Very detailed. Thanks

[@WakeThief]

you're welcome! If I can ever help, please let me know.

[@chadseberg]

You make math look COOL!

[@WakeThief]

😂 Thanks.

[@groundbreaker5525]

Also try this !!! ripstick or snake boards designs might help with a power train ...its like the way sharks & snakes move in the water sharks have a hydro foil type design in their movement as well as snakes just a thought ...I love to problem solve ..hope this helps ...ripstick or snakeboard x hydrofoil type system..good luck

[@WakeThief]

Thanks ground breaker. I’ll give it a look. Amazing how much we’ve learned in a short time yet how little we actually know. Thanks for the comment.

[@domingosdellacquaneto4381]

I must try It! Good explanation Obrigado 🙏

[@WakeThief]

Thank you, Obrigado! If I can help let me know

[@cefirmeza]

Nice video. Never really pumped well behind a kite. I plan to explore pumping in one of my next videos. Kite foil wings can pump?

[@WakeThief]

Yes, though I would say there's a limit. At 190lb, I'm not able to pump a low aspect wing with

[@user-tf2nc6qh7i]

너무 멋있습니다. 항상 보면서 많이 배우고 있습니다. 당신의 셋팅의 axis 포일을 사려고 합니다.

[@StandUpMagazin]

Very cool!

[@Mickfoil1]

Really great information. What do you think about longer fuselage to help pumping. What is the length of your fuselage measured from tip of wing to rear chord of tail wing ?

[@WakeThief]

Longer fuse helps. It slows the cadence of pumping down and allows you to leverage the rear wing better for thrusting. The effect is small though, not nearly as significant as changing the front wing.

[@rashoietolan3047]

Remotely Working from the hotel Foil surfing on lunch break 😈😎

[@ZenEndurance]

You should try a double foil, like a biplane wing. Doubles the lift, but puts it pretty much in the same pivot point.

[@WakeThief]

Yes! Horue has a bi-plane adapter for their foils! They just sent one to try. Will see if I can get that too. Thanks for the comment / suggestions.

[@johnmoore5293]

Awsome video! Could you experiment with a foil slightly longer and have the last portion of it somewhat flexible ( made with reinforced silicone (?), rubber, GE had a thermoplastic elastomer "Lomod"). Birds and fish have more flexibility on the end of their foils.

[@WakeThief]

This is a very good idea. We are trying a few different things. I believe the flexible portion lets birds change their foil section to give more or less lift per drag depending on the conditions they're in. How cool, right?

[@nbaquizmasters1]

Amazing video and resources used! Science will help us to improve pumping! So BIG CONGRATULATIONS!! One question: About frecuency of pumping: What happen with a Low aspect Wing Foil. Thicker than the wing foil of the video. Will it more difficult to pump?

[@WakeThief]

Thank you, Jose. I sincerely appreciate you taking the time to write this comment! I find lower aspect ratio wings take more energy to pump. The technique also feels differently. It's hard to isolate whether it's because the wing is thicker or whether its simply a different foil section. I know this isn't a great answer. I have found that HA wings are much easier to pump. They have longer glide between each pump (due to lower drag). This might help explain that piece: kzbin.info/www/bejne/i5m2pnyZp953d68

[@nbaquizmasters1]

@@WakeThief Thanks for your answer. It helps me a lot, I was thinking some similar to your explanation. Thanks for the video, very very informative!

[@anthonyrutten4018]

I love how you took this shit to a whole new level.🤙🏼

[@WakeThief]

Ha! Thank you!

[@pump-foil]

Just throwing an idea here, but how about having a board with a little bit of flex (like for longboards in skating) to to amplify the pumping of the legs ?

[@WakeThief]

That's an interesting idea. I hadn't thought of that. We could use the leverage over the mast and a spring force to generate a pulse. I like it. Will dig into it. Thank you, Irwin.

[@guidolaroque9280]

Foiling changed the game of watersports. Very good explanation of foil pumping. As a windfoiler, I also use this with/when the sail is powered down. I really thought winging would evolve to a windless pumping alternating between foil pumping and horizontally pumping the wing. But ugly inflatable wing are poor aerodynamic wings, the next game changer will be better air wing imho...

[@WakeThief]

Thank you, Guido. Interesting observation. I wish I could hand wing with a 10L board. I really don't like pumping larger boards. We need to figure out an easier way to dock start (it's hard and I'm not very good) and we need a way to water start after we wipe out far from our docks!

[@guidolaroque9280]

@@WakeThief What about the energy transfer point of view (I am not sure of specific english physics vocabulary, so I hope you'll sort it out) : If you consider the rider-Board foil system, it has a kinetic enregy (1/2xMxV^2) and height potential enregy (HxMxg) with the height of the rider COG varying. With no drag force the sum of these two would be a constant, since there are drag forces, the energy is leaked. Then you have to buid up again the toatl energy by 'adding' some height. So foil pumping is somewhat as hoping up a stair again and again... So you have to manage your stamina and your energy level. Reducing the height of the 'stair' is surely the best course of improvement...

[@WakeThief]

This is right. I appreciate the thoughtful comment. The size of the stair step you describe and the time to climb that stair can really affect the energy based on ones propulsive efficiency and the design of the wing. Learning the best way to step up stairs, that minimizes energy, is the goal.

[@BisdremisKostas]

great work . keep going

[@bennguyen1867]

With fast changing in front wings, what are some of the best front wings for pumping? Great teaching video btw.

[@WakeThief]

Thank you! Here’s a link to our last reviews from 2022. kzbin.info/www/bejne/eKnIfJh5Z6-KnK8

[@svenpr9183]

4 stages, just like an ICE-engine: Suck-squeeze-bang-blow Great video. This series should get many brands to improve their game, as there surely is alot of potential. - Would love to see you test the 3'11(119cm) KTS Armstrong foilboard, arguably the stiffest board available. Your slim board likely sacrifices a bit of stiffness which means losing a bit of energy in every pump. It would be very interesting to see if you can feel the difference, or even quantify it. - Would you last longer with a paddle ore, or just go faster?

[@WakeThief]

Ha! I had the same thought about the 4 stroke cycle. Thanks for the comment, Sven. I will try to get that board. You're not the first to suggest it. With an oar and effective paddle to augment the pumping, I think it would help as it would allow me to use more muscles than just my legs and arms swinging!

[@svenpr9183]

@@WakeThief Found a good price on a 2020 Naish Hover 112cm, so it will be my pumping dockstart learning board together with the Naish Ha 1800 this summer. Now I am hoping the flex does not matter! Will be very interesting to see what you find out, though.

[@jeffarcher400]

Reminds me of pumping a bike on a BMX track. In both gravity causes acceleration on the backside of the hump and is increased by pressing. This squirts us up the face of the next hump which is absorbed by the knees. Our weighted pump adds to downslope speed and absorption floats us back to the peak. You said it's all about beating the drag but it's also about lift vs. drag. I'm thinking a biplane design can provide greater lift at slow speeds. Maybe have the second wing higher on the spar so at slow speeds both wings lift but once flying the second wing is clear of the water and there's less drag. Perhaps the second wing could retract up next to the board when not needed. Until there's a way to deep water start it's kinda do or die with no way to rest. Also thinking about catamaran hulls with wings. Then you get added width with less weight and drag. The board itself can be a wing and create it's own lift too.

[@perculated7666]

Awesome video!! where can I get one for a good price?I'm just seeing these for the first time, huge lakes where I live and a beach about 1.5miles across the lake, I want one so bad to surf to the beach,people here would love it!!

[@WakeThief]

Hi Jay - Happy to help. Pls email me at [e-mail]

[@g2999]

Great video - really interesting... I wonder if you've considered a carbon fibre mast? I'm guessing one of the inefficiencies is just the weight of the equipment and the fight against it's inertia - I think your board is already pretty light, but it looks like you are using an Alu mast - have you tried alternatives? Keep up the great content! :-)

[@WakeThief]

Thank you very much. Yes. I’ve tried a number of carbon masts. The weight doesn’t matter much for what I’m doing as it’s close to the pivot point of pumping (unlike nose weight of a board as you pointed out). Lateral stiffness (roll direction) absolutely most important thing. I wish a mast was 25mm thick :)

[@groundbreaker5525]

Hey mate try this for less drag.. use a golf ball bottom design for less drag ..its like the bodyboard morey boogie mach 8TX golf ball bottom dimple surface ultimate speed board... I'm trying to convince team new Zealand to put on the bottom of our boats.. as it stops the friction weight of water sticking to board or boat surface when foil kicks in theres a point where the boat or is heavier ? due too water still being still under boat or board...

[@WakeThief]

Interesting. I’ll check out boats with dimpled bottoms and see if I can learn more.

[@sterlingcrispin]

What about a spoiler or wing on the back of the board to clean up the air coming off of the board and the rider to produce less drag? I bet it could be designed to even produce alternating down force and up force to create more powerful cycles

[@WakeThief]

Interesting idea. You’re right. Wind drag on rider is a surprisingly big force!

[@emsea7279]

Amazing

[@jonathanreinke9392]

Awesome!

[@WakeThief]

Thanks, Jonathan. Great to hear from you!

[@StuartFricke]

any plans to test the new Armstrong High Aspect 1125?

[@WakeThief]

I'm working on it, Stuart. The short answer is yes!

[@tenemax7849]

You need to get your hands on the new Armstrong HA1125 combined with the Flying V 200 rear wing, curious to see what it would do for you. Maybe you can thief one somewhere? LOL

[@WakeThief]

I’m working on it. Please stay tuned

[@Novometix]

Is it Tom Cruise at 1:24 pumping ? What a legend ^^

[@alexanderhagensen509]

I want to start hydro piumping! Can u recommend a good starting setup? Board, foil etc.

[@WakeThief]

Yes. Happy to. Please email me with: (1) your weight, (2) boardsports skill level, and (3) how you mostly want to use it? Big wake, small wake, dock start, hand wing, etc. [e-mail]

[@xyzct]

Awesome video! Thank you!! Perhaps I can get your thoughts on a decision I'm about to make. I am trying to choose between the Armstrong Wing/Surf 4'0"/2.95kg/27L and the 4'5"/3.40kg/34L boards for prone surfing in Oregon. (I'm 6'1" and 80kg, and have been surfing for decades.) My main objective is to become proficient enough at pumping back out to allow linking waves. While I like the additional paddling volume of the 4'5" -- and I am very familiar with different board volumes and how they paddle -- I am worried the extra length and weight over the 4'0" will reduce pumping efficiency, but I have no idea by how much! Any thoughts would be most appreciated.

[@WakeThief]

I’ll try to help! Great question. Thanks for laying it out … please take a look at my Lahoma family friendly hydrofoil review. You can see the effect of swing weight. My honest guess is that it’s not that big of a deal. If you can pump a foil for 2min with the 4ft that extra 5” might steal 20s. I don’t think it would steal 30s. This is just a guess, though I feel pretty confident in it

[@xyzct]

@@WakeThief, awesome! Thank you so much for your thoughtful response; that's very helpful. I'll probably go for the 4'5" then, because the extra 25% in flotation will help significantly in paddling distances and wave-catching, so the loss in pumping efficiency might be worth it. (Damn, it's a world of tradeoffs!) Long live the Generalized Navier Stokes Equation!

[@WakeThief]

😂 I haven’t heard navier stokes in 20yr! Good luck. Let me know how it turns out.

[@OhighOSkater]

It looks like it’s similar to skating. I’d love to give this a try

[@WakeThief]

I’m a former skateboarding and ice skater. Loved both sports. This was right up my alley. Probably yours too. Please let me know if I can help

[@WakeThief]

Especially with a small board like I have. Pumping feels a lot like pumping on a half pipe.

[@OhighOSkater]

@@WakeThief That’s awesome! I actually have a trip to California that I’m planning for after Covid is over, so I think I’m going to add this to the list of things I want to do on that trip. Thank you for being willing to help. I really appreciate it a lot. If I end up with some questions, I’ll leave you a comment. Thank you!

[@OhighOSkater]

@@WakeThief Carving is probably my favorite part about skating, so I think I’ll love this. I look forward to giving it a try!

[@WakeThief]

You bet! If you’re looking for some connections in CA let me know or join some of the Facebook groups. This sport is such a tight knit community. Probably because it’s small and probably because those who’ve done it are completely hooked. It’s as close to flying as I will ever see! [e-mail]

[@chrisb4419]

I don't even foil, I do surf... This video is fantastic, and inspiring...

[@WakeThief]

Thanks for the comment, Chris! I so appreciate it. If you ever want to foil, you'll figure it out in no time. I've never even foil surfed in the ocean yet! If you want to explore getting a foil, let me know. I'd be happy to help. [e-mail]

[@chrisb4419]

@@WakeThief Thanks! Seems like there's a lot to consider! We do have a good spot nearby with soft shoaling waves, just gotta take the plunge... I love the physics explanations!

[@WakeThief]

@@chrisb4419 if I can ever help you find one, I’d be happy to. [e-mail]

[@chrisb4419]

thanks for the generous offer!

[@aterxter3437]

I am just thinking about it, I don't pretend to have the whole knowledge about airfoils, but thanks to my physics lessons giving me an introduction to fluid dynamics, I think that some aspects of the problem of reducing the power need can be understood and optimised without requiring too much experimentation. As I learned, the usual expresions of lift and drag of a wing (1/2*volumetric mass*surface*lift coefficient*speed^2) are available in imcompressible flow, a valid hypothesis in air below mach .2 and nearly always usable in liquids (still below mach 1, but mach 1 in water is 5times higher than in air), and by knowing the usual speed at which you glide (I have no idea as I have never tried), you could easily calculate the Reynolds number associated with the wing (volumetric mass(kg/m^3)*speed(m/s)*characteristic distance (the wing's cord, in m)/fluid's viscosity (around 1*10^-3 Pl (standard unit, for Poiseuil, one of the great scientist in fluid dynamics)for water if I recall correctly), with the Reynolds number, we can know the performances of a particular airfoil, listed on the website airfoiltools.com Thus having an idea of the behavior of a wing without needing extensive experimentation. In my opinion, the main thing would be first to see the coefficients of lift and drag associated with the Reynolds number, in the span of incline of the foil, which can be calculated from the videos.

[@WakeThief]

You nailed it. Please check out our video about how foils work. It just breaks down all of what you just shared.

[@camofpv]

I've no idea why I've watched this but that was impressive

[@WakeThief]

Lol. Thank you. I totally love your comment. You’re probably wondering why the hell are these guys doing this … reality is it’s amazing, like flying

[@tofertarget]

Possibly the front wing to pump for long durations could be the following: Super long high aspect with small winglets at the tips to reduce pressure drag; thicker camber to the inside of the wing section to be most efficient at slow speeds...like a glider flying over heat swells in the air. Wing tips section should begin to thin out and taper. Possibly some flex at the tips, but not much. Finally the smallest thinnest rear stabilizer with higher flex with the angle of incidence very close to that of the front wing on a long thin fuselage, much like the high efficient gliders of today. The thickness of the camber or wing cross section is the tough one. In water, more research needed. All this to be able to get some assistance from the flex of the wing tips and rear stab, but not add much drag in the flex, and fly at very slow speeds. Pumping required could then be at a much slower cadence, maybe 1/second, tiring muscles before cardio, and allows for brief recovery during the glide. love to talk more. Navy fighter pilot, Clamp

[@WakeThief]

Chris! This is epic. Thanks so much for sharing. Most of this I understand and makes sense to me. As we dig further, I'd love to reach back out. Please email me at [e-mail]. I couldn't agree more with the 1Hz being key. Thank you!

[@jeduthunoosthuis2735]

As an engineer I found this super insightful and interesting. Thank you!

[@WakeThief]

Thank you, Jeduthun! I hope it helps you learn to pump better! I so appreciate the comment.

[@DRK_MTB_406]

💡Whacky idea here💡if you held small weights in your hands (.5-2lbs) you would be able to create more driving force through the up swing of your arms? Of course you’d be heavier, but mitigated by swinging the weights back down. *I don’t foil yet, but love the physics and your approach to analysis*

[@WakeThief]

I don’t see why not! We’ve found that the best pumping board has some flex but not too much. I think there’s a lot still to learn here.

[@DRK_MTB_406]

@@WakeThief absolutely, some flex could distribute the energy return throughout the climb phase. Looking forward to seeing more from this channel. Thank you 🙏

[@bbolman27]

Could you start doing this while stationary in the water or do you need something to propel you first to move? Cheers mate

[@WakeThief]

I wish. That’s a roadblock for unlimited expansion of this sport! Right now I have to swim home :(

[@jackmarkmcgill]

Very interesting

[@WakeThief]

Thanks, Jack!

[@jamiebennett3857]

Hello, Wow, great data. I commented on another video but this graph has it all. I can't make out the mast drag but I can see the 'spray'. From my understanding this is the 'release' of the water from the tailing edge of the mast. What is the order of the values, or do you have a zoomed in graph to make out the order and relative drag. I can't make out where mast profile is in relation to screws and fuselage (virtually equal) with spray below. Hmm, so interesting. I hope you can help me understand this a bit more. Cheers!

[@WakeThief]

Thanks, Jamie. Yes, and I'm now finding the the mast spray is more significant for some foils than others. Good luck on your journey!

[@jamiebennett3857]

@@WakeThief Cheers! Thanks for such inspiring videos. Thanks for reply on the other video with related drag calculations. I still can't really make out what you've shown for mast drag and spray drag but it seems minimal in comparison to others. I can appreciate it might be estimated but can you confirm that it's lower than the line I see for fuselage and screws, it appears less than half. I'm struggling to discern each graph line.

[@WakeThief]

@@jamiebennett3857 please email me. Happy to send you a higher res copy! I’m sorry it’s not legible!

[@timob4870]

I’m getting a sore right knee from pumping (my back knee). I try to keep it properly aligned without any twist. Have you had any knee issues and if so did you find a way to fix it?

[@WakeThief]

It's funny you ask. My right knee had an old injury that plagued me when I started foiling. After all the pumping I did it has gone away. Perhaps the foiling was good therapy for it?!?! I'm not an expert here, but I would think pumping a foil is a nice low impact exercise that should help not aggravate. Perhaps you can try sliding your mast further back to load your front leg a bit more?

[@NCLSUGRT]

have you considered getting a full carbon foil for less weight and better hydrodynamics

[@WakeThief]

I have tried some and they are much lighter. I think weight matters, certainly more for aerials, so full carbon is a good idea.

[@londono007]

What about having 2 foils in the same board, one for stability and the other one for impulses

[@WakeThief]

That’s a great thought. I’ve seen architectures like that and currently feel like a larger rear wing helps pumping. I’ll dig into it. Thanks for the comment

[@FoilPowell]

Have you considered possibly a small bike frame or a set of handlebars so you could pump it more like a bicycle in a pump track? I feel like this is the missing link but having a hard time getting anyone to listen. If you try it please tag me so I can see! I'm subscribed.

[@WakeThief]

Will do. I think that's a good idea, as it's a great way to deliver more force/power, but I'm not really sure how we'd get all the timing right through the four phases.

[@FoilPowell]

@@WakeThief the pump timing and technique may change do to the added strength power and precision enabled with four points of contact. Time will tell. It may even change foil design, Wing placement, depth etc.

[@garyjohnson4575]

Would hand wings, help reduce the recovery between the phases?

[@WakeThief]

Absolutely. And it might be the only suggestion to get back to the dock when you’re stranded out in the middle of the water. The only thing I that a hand wing requires a higher volume board which isn’t as good for pumping as the small board I use here because you lose energy swinging a bigger board up and down in each pump.

[@silversurfer666]

Aint it an option to make the frontwing more flexible? Especially at the tips. Works for a Stingray. ..

[@WakeThief]

Interesting idea. I’ve generally found flex to be bad but the flexing front wings haven’t bothered me much. Maybe this is why!

[@silversurfer666]

@@WakeThief no idea what material to use thats light, strong and flexibel, though...

[@flmason]

Is it possible to start without assistance in the middle of the water, from a standstill... like after one has fallen off?

[@WakeThief]

No. I wish there were. This is a shortcoming of this sport that I’d love to figure out!

[@booger808]

Do you think you could maybe figure out some pumping drills someone could do on land? Just to help with the timing and the various foot pressures?

[@WakeThief]

That's a great idea, Andy. Let me think about that. It would be as simple as a sequence to follow with foot pressure to a beat of a song! Fabulous idea.

[@WakeThief]

Said another way, I should find a song with the right rhythm and explain a step sequence.

[@booger808]

That would be awesome! By the way, this video has some great stuff! Thanks for posting it really helps a lot!

[@cefirmeza]

In my opinion the best drill on land is pumping a bamboo deck longboard such as loaded boards. I used to ride it for years and could pump for miles on flat ground without touching the ground. It really helped me getting into the foiling riding skills.

[@toirt-ls6qs]

So if you fall in the middle of the lake do you have to swim back to the edge or what do you do

[@WakeThief]

😂 swim back to my dock! I wish I had a better answer

[@antonmaier2263]

i had the exact same idea and my conclusion was to use a different wing design. what is your wing area?

[@WakeThief]

This wing is 1780sqcm and 115cm span

[@antonmaier2263]

@@WakeThief what you need is a more efficient plane design to reduce drag considerably. Higher aspect ratio, optimize for a specific cruise speed, ootimze liftdistribution for less induced drag and maybe get even rid of the fuselage and backwing

[@WakeThief]

Great ideas. Thank you Anton.

[@oceanglider]

Have you done an analysis of the Axis 1120?

[@WakeThief]

We haven’t done a formal review but I have clocked some hours on the 1120. A slower, higher drag foil than the 1150 but the extra area helps heavier riders fly at the speed I like to fly at … flying slower helps conserve energy to fly longer.

[@oceanglider]

@@WakeThief Thank you. Just what I wanted to know. You're 190 and I'm 210. If you don't mind me asking, have you experienced the 500 anhedral tail? Thanks again. Your videos are great.

[@WakeThief]

Thank you, William! I have not. I’m not really a fan of the anhedral rear wings. I will like they create an instability for me … I’m sure I can learn and correct for it. You’re right to increase rear wing area if front wing goes up, so 460 might be a good option or the 450/475 progressive. If I can help, please don’t hesitate to email me. [e-mail]

[@antonmaier2263]

which software did you use to generate this speed/power-graph

[@WakeThief]

Excel. We built an excel-based on model of the physics.

[@Tel--wg8te]

May I point at one spotted mistake: it's omission of the air drag created by rider. At speeds of 4-5 m/s it's quite big not to be put in the overall drag equation.

[@WakeThief]

You’re exactly right. It matters quite a bit. Particularly if there’s a headwind! We have it in the graph. Look at the bottom of the legend. Thanks for the thoughtful comment.

[@Tel--wg8te]

@@WakeThief If you're meaning "rider" and "wing profile drag" these are at radio of 1:5 @5m/s on the chart. I'd assume the ratio is about 1:2 or even 1:1. So rider's air drag is quite significant at the speed. I know it very good from biking, exactly at 5m/s wind drag becoming very noticeable. All this told about calm conditions, if windy just add/substract head/trail wind's speed and "rider's air drag" graph will move to either side respectively. Greets!

[@hughdunbar9823]

So a high aspect ratio foil is better for pumping? I bought my first foil for winging, a F-one Gravity 1800. I am guessing that's not ideal to pump with?

[@WakeThief]

That should be good. I think it’s fairly high aspect if I remember correctly. It’s on my list to review.

[@hughdunbar9823]

@@WakeThief Thanks, I answered my question by watching more of your vids. We are experienced wake foil surfers (on a Ride Engine 980 or something similar, quite small) and we picked up wings and I have a F one rigid board, at 110 litres. I am 98kgs so it's tricky but doable, I just need more wind! Thanks for the reply and the vids!

[@WakeThief]

@@hughdunbar9823 you bet! Let me know if I can ever help.

[@hughdunbar9823]

@@WakeThief Will do. Also, I wanted to say, I love the 'wake thief' name, and concept. Cruising around looking to steal rides on other boats is awesome. Kudos!

[@deltazulu302]

Had to comment

[@MichaelRainabbaRichardson]

Anyone that's done this and pumped half pipes on skates/boards, would you consider the process similar?

[@WakeThief]

Yes, Michael. I skateboarded as a teenager. Very similar feeling! I would've said that as a description if I felt like many folks knew that feeling, but unfortunately they don't.

[@paulosilva-dm1qb]

What if the bord itself was designed as an airfoil as well....??? I think that would generate an upward force wich in turn would decrease the sinking force...What i imagined is that we must have a way to keep the board up in the air for longer..Of course a wing would help..

[@WakeThief]

That would certainly help reduce it's drag in the air! I don't think the speed is enough for it to be a significant factor compared to the front wing flying through the water, but I love the idea!

[@danielschechter8130]

I think that getting to 30 minutes is really just a matter of strength and stamina, both of which can be developed by training. Of course, 30 minutes is not "forever." The thing looks cool. There's no way I could ever do it.

[@WakeThief]

You're absolutely right. 30min is enough. I don't think 30min can be done on this foil, I think we will need bigger wings, but I have no doubt it will happen. Thanks for the comment.

[@jjouh]

Probably you will need to get a thinner and longer mast. Thinner: less drag. Longer (1m): more ample strokes. The Mast does not need to be very stiff like in kitefoil because no lateral forces. So get a custom carbon mast, maybe 1cm width is possible?

[@WakeThief]

I had the same thought Julien but realized that even a slightly thinner mast introduced lateral rigidity issues that made pumping less efficient. Even though a thinner mast will drag less the lack of rigidity just isn’t worth it. Perhaps a thinner and more rigid mast will be available in the future. Thanks for the comment, Julien! I appreciate you taking the time to share

[@jjouh]

@@WakeThief axxis mast are 16 or 19mm Of width. High modulus carbon mast are 14 or less and stiffer then aluminium. Also I imagine the cord of the mast has an impact on drag.

[@WakeThief]

It’s a great point. I need to try carbon. Here’s when I compared the 16 and 19mm masts: kzbin.info/www/bejne/hn3Fpp9uftZ4kKM. I’d love your feedback.

[@jjouh]

@@WakeThief interesting test and conclusion! The profile of the mast also is an issue. Also it would be interesting for you (us) to test without the stabilizer. Some kitefoiler do it without stabs, it s definitely more manoeuvrable but I wonder if pumping and gliding would be impacted?

[@WakeThief]

Ha! That was a fun day. kzbin.info/www/bejne/r4bKl6Csf7F6r5I it worked but pumping was impossible. Made me realize that rear wing matters. Keep the ideas coming Julien! Some of the ideas I had that I thought were dumb proved to work out, like the dolphin fin.

[@joalindkvist947]

The ANSWER: Make the fuselage flexible so that the stabilizer wing moves like a dolphins tail. Did it work? Good luck from Joa in Sweden

[@WakeThief]

Thanks Joa. It did work but wasn’t clear that this new way of pumping was better. It was different. Just not sure better. Please check our dolphin tail video out.

[@melvinmahe1520]

Try with nunchaku in both hand for add power

[@WakeThief]

That's actually a great idea. Maybe carry some dumbbells in my hands!

[@bryanbilbrey9014]

You should try wearing jumping stilts to pump the hydro foil

[@GrantAllenVideo]

Total novice here. But what about adding weights or dumbbells to your hands to give them more weight to throw around. I know that’s more excursion, but it would shift energy away from your legs into your arms.

[@WakeThief]

Ha! That's a brilliant idea, Grant. It would seriously help!

[@novak2033]

Would foot straps be of any help?

[@WakeThief]

Yes! Like a cyclist! It’s on our list. Thank you for the thoughtful comment.

[@SANTACRUZDRONES]

So at 2:16 if you are critiquing yourself, what were you doing wrong? Or was going to an HA wing a major factor?

[@WakeThief]

That was my very first attempt pumping a foil. I didn’t really know what I was doing except trying to copy what I had seen. Learning when to apply force and for how long is an important factor. Learning the speed to do all this at is important. And then there’s a right frequency and amplitude at each pump. It’s dialing in those four things that is the difference between a few seconds and a minute or more. Honestly I just tried and tried and tried with many failures before it just clicked and started to work. With each foil there’s a different speed frequency and amplitude and force pulse duration. Thanks for the insightful question. And yes, switching from LA to HA changes all three more than changing from one HA to another, in my experience.

[@SANTACRUZDRONES]

@@WakeThief All my buddies that have switched to Axis HA foils are blowing me away pumping, if I wasn't so invested in Armstrong I would switch. I have been slowly progressing on the HS1850. Waiting for it to click, thanks again for the replies and a great vid.

[@WakeThief]

The HS1850 is a good setup. If long distance pumping is your desire, I’d recommend practicing and breaking 90s on the HS1850. With ok fitness and good technique it’s possible if you’re

[@Heathbarbcrunch2]

Also like a swing

[@xscale]

I have three questions, likely all equally foolish: 1. Do you lose energy by changing the board's angle of attack when all you want is to change the wing's angle of attack? Could a hinge system change the wing's angle without you having to pitch the board back and forth? 2. Could you make a wing that's more dolphin shaped in cross-section and fill the hollow with air in order to increase buoyancy and obtain lift that way? 3. Could you make the wing flexible so that it would flap in the water like your human-powered-flight friend's flexible wing flaps in air? Or is this the same question as question 1?

[@WakeThief]

Brilliant. 1 makes a lot of sense. It’s such a departure from how it’s done today with more moving parts but would do exactly as you say. We lose a lot of energy swinging the board. 2. That approach makes sense but unfortunately the volume of the wing is so low that it won’t make a huge difference but in theory yes. 3. I think the flapping in the pitch direction will work. I worry that the roll direction really needs the rigidity for stability. Thanks for sharing these ideas, Peter. Keep them coming!

[@xscale]

@@WakeThief not brilliant, merely creatively stupid - I know very little about foiling, I have spent time paddling surfskis, and pumping longboards - but wing blades on paddles and the angles on ldp boards are very different problems to yours. Still I'd love to see you succeed - and it looks like you have the right crew to help you there! One more idea that might be useful ... with long-distance pumping boards they use brackets to get the angles you need. That means you can use any truck you like, whcih means you don't have to reinvent the trucks. Perhaps you could get the flapping by mounting the existing foil on a bracket that has the extra moment, and then mount that bracket on the post? Again that's probably a stupid idea. But I generally find that good ideas aren't too far from stupid ones ...

[@WakeThief]

@@xscale isn’t that the truth. We tried a flapping dolphin tail and have more work to do there. Thanks for taking the time to share, Peter.

[@robadair]

It seems like 2 pumps per second will require too much energy to be sustainable over a long term (30 minutes or more). I think a slower cadence and longer glide periods would allow needed rests. Watch surfers connecting multiple waves and they are gliding long distances between waves. It may be that the next generation of equipment will allow this; super thin foils with short chords and long spans much like your 1150.

[@Tel--wg8te]

Foil surfers use energy of the waves to have a rest during glide time. No miracle here also

[@robadair]

@@Tel--wg8te whoosh

[@dordagiovex9989]

1-lower necessary wing speed with bigger wing surface. Power is proporzional to the cube of speed. 2-decrease drag with extreme aspect ratio. If ur wing will be similar to a glider wing u can hope for 50 glide ratio: 50 meters forward losing 1 meter of altitude

[@dejayrezme8617]

Right, I was wondering the same thing! A larger or oversized wing would seem like it will be slower but also more efficient in keeping you out of the water. I think the power is only roughly linear proportional to the speed because every size of optimized wing will be only as large as to overcome gravity, so you're dealing only with induced drag and the "cube of speed" factor cancels out because the faster you design your hydrofoil for the small the foil can be. At least up to a limit until you reach too high speeds and very thin wings and deal with cavitation. So you cannot make your wing arbitrarily wide and short. I think this is what the Reynolds number expresses. I'm not sure this is actually true though, I've only played around a bit with the numbers.

[@WakeThief]

1 - Nailed it! 2 - Nailed it! If we go too big in area, the viscous drag dominates ... If we go too small, we go too fast and the velocity cubed dominates ... there's a sweet spot unfortunately and many variables to optimize. Thanks for this! Super simply said. I wish I said it this simply in the video!

[@WakeThief]

You're totally right ... as chord length goes down Re goes down and drag goes up non-linearly ... same thing happens with speed. So you again, there's a desire to go faster, but not too fast as power goes up with cube of speed ... it's a super fun optimization problem (#engineersdream) and we haven't even addressed stability yet!!!! Thanks for engaging and sharing via this comment. Please keep the ideas coming. We hear you!!!! [e-mail]

[@dordagiovex9989]

@@WakeThief I did a few calculations. I assume that you place the wing at the optimal angle, where the induced drag is equal to 0-lift drag. en.wikipedia.org/wiki/Lift-to-drag_ratio. Then using the lift equation and the drag power=D*v I obtain power=weight^(3/2) / b * (cd0/Ar) ^1/4 . b is the wingspan Ar aspect ratio (roughly span/cord) cd0 the 0-lift drag coefficient. So doubling span with equal area (which dictates glide speed) you should more than half your effort. Another way to write this is power= (weight/b) ^3/2 * (cd0*S) ^1/4 where S is the wing surface. To optimize make the wing as wide and as thin as you can structurally and.. Lose weight ;)

[@dordagiovex9989]

Also.. It is strange that the wider wing u built requires more effort and goes faster than the smaller one. Did you reduce the angle of attack of the wing? That would reduce lift making it faster and possibly less efficient if the angle is different from the optimal one

[@Synaps4]

Hi wake thief! Two things I noticed that might help you. One I noticed that longer boards allow you to shift more weight forward. I think there is a missed opportunity to generate a lot of extra power with the leverage gained by shifting your weight entirely out over the front foot. Current boards are almost certainly not configured to be used this way but if you want to get more power by spreading your effort per time out, use leverage. This multiplies the effect of your normal bodyweight on the foil so you wont need to push as hard to get the same force. Second, when pumping you were often going faster than the minimum flight speed of your board. it should go without saying that to pump longer, one way to do it is to slow down. This synergizes nicely with part 1. So in summary I think the ideal long term pump foil board will use leverage and weight shift rather than just pushing hard on the board, and it will go slower than youre used to. It will probably have a slow rocking cadence rather than the frenetic pumping commonly seen today.

[@WakeThief]

Well said. I certainly agree with slowing down but I do find that if you get your body too far ahead of where the foil pivots, pumping efficiency goes way down. Your point about leverage is good but it’s also important your body doesn’t crouch down. It’s easier to stand straight with feet closer together for 10min than it is to wall sit for 10min in order to get your front foot more forward. I also find bigger boards have more swing weight which steals energy with the extra inertia.

[@Pablo-qd7if]

Have you computed how much energy is wasted to change the AoA? My point is, in the sudden pitch change when the drive begins. At this moment the stab will be pushing upwards a lot, reducing the pitch rate. That force has to be cancelled by the front wing. So basically youll have lots of extra induced drag in both winga . Might be worth doing the math to see how much you're wasting there... have you tried stabless?

[@Pablo-qd7if]

A quick test could be comparing the stationary power you require (level flight) compared to the average power youre applying when pumping. If they are not similar, then theres room for improvement here

[@WakeThief]

Yes, the biggest loss comes from drag force, and when you pitch the nose up, there' both drag force and lift force pointing backwards (holding you back). And yes, it comes from both the front wing and rear wing. It's why we try to go weightless during that portion (so that the lift force (which equals ones weight on the board) is as low as possible. I have tried flying stabless. Controlling pitch was very hard and I wasn't able to pump as a result. A stab is a necessary evil, unfortunately. however, if you could spring load it to help when you want it too and not be as detrimental when you don't, that would be a good innovation!

[@WakeThief]

Excellent point.

[@Pablo-qd7if]

@@WakeThief i see. Thanks a lot for the reply and congrats for the channel! Super informative and motivational! (Next week i"ll build a small board and start pumping) it looks fun and challenging for a quick dip

[@WakeThief]

@@Pablo-qd7if awesome! Please let me know if I can help in any way. Good luck!