UPGRADING my Airboat Hydrofoil (Can I Boost Performance?)

Plans for the Mk2 hydrofoil can be found here: www.projectair.co.uk/downloads
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Music by Andrew Applepie
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📌ABOUT
Project Air is all about building DIY aerospace engineering creations, learning about the science behind them and testing to the limit. Make sure to check out the rest of the channel to watch projects on RC planes, drones, rc boats, hydrofoils, hydroplanes, seaplanes, rockets and more. Project Air was started in 2017 by James Whomsley 😎
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[@GunganWorks]

Wow! Thanks for the shout out! It's really awesome to see that you got Mk2 fully foilborne! I think the speed was limited because the foils were simply too large. I noticed it would lift up on the foils at a relatively low speed; and as it accelerated, the foils started skipping on the water like skis, rather than foiling. This tells me the foil-loading (as opposed to wing loading) is too light. I think it would perform much better if the ship was much heavier, or if the foils were 50% or even 25% or their current size, but that can be a project for next time. ;) Congrats on the build and flight! Cheers! -Dave

[@lukeattubato]

Obviously you're the hydrofoil engineer, so correct me where I'm wrong, but when I was watching it looked like it was lifting up too early not because of the size of the hydrofoil, but because of the hydrofoils AOA in the water (and therefore its decalage relative to the airboat), to my mind, that also explains the skipping and the stalling. I don't really understand why a light foil loading would cause the skipping? could you explain further? I get that a light foil loading would cause too much lift when in the water, forcing the boat up quickly out of the water, causing the skipping, but I don't get why it would have so little pitch stability. With a plane this behaviour would be controlled by the size of the horizontal stabiliser. Might a soloution to this be having a larger rear foil or maybe variable pitch on the front foil as well? Sorry for my use of aerodyanmics specific terms, I don't know how well they carry across to hydrofoils :D

[@GunganWorks]

​@@lukeattubato The lift equation: L = 1/2 * ρ * V^2 * Cl * A might clarify. The density of water is approximately 100x more than the density of air, so to produce the same amount of lift in water, the foil area can be 1/100th of a theoretical wing area. So, pretty tiny. Water produces much more lift than you might expect. That's why the foils should be smaller. Now in regard to angle of attack, you are headed in the right direction, the large foil area is accentuated by the high angle of attack. Because these foils are so large, they are very sensitive to AoA; and that AoA sensitivity probably translates to pitch sensitivity as a result. Because physics. What I was seeing, rather than the foils stalling, was classic pitch instability, exactly the same as what you would see in an airplane, except as the nose pitches down, the hull hits the water, and brings the boat to a near stop. I think moving the CG forward would help. It would also let the rear foil get out of the water more easily, too. Secondary to that, because the foils were so large, and had such a high AoA, they were creating so much lift that they would rise out of the water entirely, and start skipping on the water like skis. If the front foil was a continuous V, rather than flat in the middle, this effect would be reduced somewhat. The extra benefit of a deeper V without a flat center section is it would add roll stability. TLDR: Here is what I would do: 1. Reduce the area of both foils by 50% or even 25%, if you really want to go fast. 2. Reshape the front foil to a more aggressive V without a flat center section, I'd try 30° of total dihedral (i.e. if one foil was flat on the table, the other foil would be raised up 30°) 3. Use smaller propellers, to bring the thrust down lower; and use the same coaxial setup as Mk1-either centerline thrust, or, maybe try putting the twin motors farther apart. Centerline thrust will eliminate the torque-roll effect. Wider spacing will mean it takes less thrust to make the boat turn. But the added dihedral might make this unnecessary. 4. Move the CG forward a bit-a few centimeters, at most. 5. Add a lot of expo on the pitch control on the rear foil. It should act more like trim than an elevator. A little goes a looong way. Full disclosure: In reality, my reputation exceeds me. I wrote a research paper on hydrofoils several years ago. That is where I developed the understanding of hydrofoil dynamics. I have not done much with hydrofoils since, except begin designing a human powered hydrofoil (Only so far as brainstorming in my head-I have not yet touched pen-to-paper with that idea.) However, it helps that I have a mechanical engineering degree and an aviation background.

[@lukeattubato]

@@GunganWorks Thank you for the writeup! that really explains most of what I was wanting to know, and confirmed a few of the things I was sure I was right on. I realise now that I was looking at the AOA vs pitch stability thing the wrong way round, I never thought that when you have a surface that has that much effective area, its angle is so much more important. I hadn't thought about it until I read what you wrote, but removing the centre section of the hydrofoil to make it a V shape also seems like a very good way to get the right hydrofoil size. If your hydrofoil is too big, it will raise up higher on the V, making the hydrofoil smaller, and somewhat self correct. Don't be so quick to discredit yourself, I too have a strong avaition background, and I'm soon going to have a degree in electronic engineering, but you sure know a lot more about whats going on than I do. Thanks again for the insight.

[@bobwalden5853]

When I was doing the SWAMBC Fast Electric racing series I tried a Hypercat with a brushed Graupner 700 motor and 12 NiMh cells of 2400mAh. It flattened those in just over 5 minutes and went at about 40 MPH. I later fitted what I called "Ducks Feet" as I couldn't be sure of getting hydrofoils properly designed or adjusted. These were metal triangles about twice as long as wide with the flat edge forwards. The four were fitted on the outside of the catamaran hulls with an angle of incidence at about 10 degrees. It was superb, and turned really well. So well in fact that I kept clipping the marker buoys until one fell off. End of experiment, but then I fitted a 4 foot wing on top, This added some weight so acceleration was a bit slower but the top speed was greatly increased as the wing lifted the hulls from the water. I din't have any control once it was airborne do it would crash in a great splash. Loads of fun, but a real handicap to the other competitors during a race!

[@erick2051]

@@GunganWorks hi Great explanation there! Could you please add more info about wing and foil loading? What is the difference?

[@DeadlyDiddly]

It's always disappointing when you set out to improve something and end up borking it up, but the fact is that the Mk 1 looks like a rescue boat, while Mk 2 look like it'll need rescuing. 😁

[@rmdcade1717]

I'm really digging the new intro card and the extra editing punch in this video.

[@averagecommenter4623]

CAREFUL! Elon musk is going to make an aluminum version of that and call it the cyber boat!

[@MaxMax-dq1lu]

I saw an interview where some1 suggested he make the Cyber truck amphibious & he thought it was a great idea...! So hyydrofoils could b a great optional extra...

[@MadScientist267]

I originally opened the first video hoping to see a cybersomething sink... And now I'm not sure what I'm doing but they're cool to watch

[@MCsCreations]

Beautiful job, dude! Really nice! 😃 Some day I'm going to build one like that!!! 😃

[@thomasmills6789]

Thank you James, I very much enjoyed these hydrofoil videos, as I am in the process of designing a 3D printed hydrofoil of my own. I appreciate how you have been going into the stability/instability issues, because that's what I've been most worried about (my ship is still in the CAD stage, not printed yet!)

[@Project-Air]

Thomas Mills really pleased I could help in some small way 😊 Best of luck with your project!

[@Julius639]

@@Project-Aircan you give me the stl ?

[@RavenRaven-se6lr]

So much fun “Nippy”. Good camera work and Editing.

[@onyxgryne9767]

Split the rudder control to include the fans. Also upgrade the motors to ducted fans. This reminds me of a hovercraft so you may want to adopt that motor design. This will most likely solve the engine stall issue as well . Also reduce the bow lift ,the boat only needs to clear the water it doesn't need to rise so high. For that to work you wouldn't need to use a curved Wing anymore. You could use a flat wing and a single arm to mount it instead. Considering widening the stern Wing as well to balance the lift.

[@pdtech4524]

Excellent work! How about a ducted central prop power system, keeping the weight central might help stability and keep those props out of the water when cornering/banking👍😎

[@ronbrideau8902]

Aluminum can thin foils for razor like smooth flow and on adjustment rail for easy attitude and balance tuning.

[@yungcrow7992]

Not sure if it's been mentioned yet but I noticed in the video that the water that was clipping the rotors was from the front foil, you may want to think about adjusting either the prop length or if you can extend the front foil length it may help.

[@dave7421]

Your gonna do very well in life and it will be very well deserved. Great work on all your videos. !!

[@itsnola8095]

Did i find the very helpful Dave?

[@dralloc6228]

What a nice boat ! Nice very boat ! Nice water boat with very nice boat !

[@fishyerik]

They're to small, to be stable with narrow hydrofoils, pushing center of gravity so high up, will make them unstable. I recommend try replacing the center hydrofoil with separate outward pointing "arms", so you can get wide support even when you are going fast and the hull is as high up as it can be. Like on Hydros HY41. As Dave already pointed out, you should do a redesign of the foils anyway. Maybe make it easy to switch foils, so you easily can try different designs, and replace when they break.

[@danielfreytes8297]

I'd love to see how well a dynamic foil work. ( i.e. a foil that moves like an elevon. )

[@Matt_Barnes]

Have you considered using ducted propellers? It would really up your thrust from each prop, and maybe it could help improve the power/authority of the differential thrust in turns because the thrust of each prop would be vectored more effectively. By focusing the thrust using a duct around the prop you might increase the leverage the prop has against the boat's hull. Also, it'd help keep the props from clipping the water. Very cool project by the way!

[@dansanders7577]

I'm in danga of gettin water in my wellies ! Much love from the U.S. !

[@anirbansengupta8465]

Great job buddy!!!

[@andreasvox8068]

Have you checked the CG of the Mk2 against its roll axis? When it's hydrofoiling it should roll around the center point of the front hydrofoil, and it can only be stable if the CG is below that point.

[@matthewellis3004]

That is a challenging project. Keep on prospecting

[@earthworm94]

Just an off topic note about what you said. In most conventional aircrafts (general aviation, airliners, etc...), you want the center of mass forward of center of lift. In case the aircraft stalls, the plane would dive head-first so you can regain airflow on the wing from the front to the back which allows you to regain control. If the center of mass is at the center of lift, it's likely that the aircraft could dive tail-first, and not allow the wings to generate the lift required to get out of a stall.

[@Dblackarialallstars]

How did you program the differential thrust? Ive been wanting to do this on my air boat as well. Oh and Great content! Keep up the great work!

[@j.d.3875]

great, subscribed

[@Fm-ss4uj]

If you add a duct around the 2nd plane props and add a servo to move propellers up and down you will get much greater lift and will maximize thrust along with increasing maneuverability.

[@oscarpinchen4431]

Yes please to jet tip helicopters! :D I've always wanted to know how feasible such a project is. ^_^ Also, Nippy McShippyFace's contraprops look ace! ^_^

[@aleksszukovskis2074]

Hey. I have and idea! How about you coat the wings with something hydrophobic to reduce friction?

[@mattdumbrill8324]

Liking the project, look forward to thr next video

[@Project-Air]

Thanks for watching!

[@Drunken_Hamster]

Put the propellers/motors from the mk2 on the front of the boat, and make them spin in the opposite directions they do currently. Your problem is the torque of the motor and thrust of the prop wants to lean the boat away from the turn rather than into it. You can also dial in some thrust "toe in" as well as a bit of up angle to further correct this tendency.

[@derschwartzadder]

Nice experiments. I can't help but wonder if having the rudder and rear foil pitch coupled together is also part of your issue. I imagine having a separate rudder and foil would help you out.

[@tsugumorihoney2288]

beside it is pretty old tech which already made in use and all he need just use examples from real life instead of doing this fails

[@j.c.cannon2112]

One of the issues for the rear foil not lifting maybe the location of your motors and the thrust vectors they are creating. Due to the angular mounting and the height above the craft, each motor is also producing a slight downwards force that increases exponentially with more thrust. This may be making downforce that the rear foil's lift has to overcome. Moving the motors lower or even out to the side would make them more in line with the centers of lift and mass on a y-axis and moving them closer to the front would give more stability.

[@lisandronicoletti8567]

My suggestion as an naval engineering student is to change the shape of the main foil, so that looks like the foil the hydroptère, two different foils with the shape of a V aiming outwards, therefore when the boat gains some speed it raises, but because of that there is less foil in the water, which causes less lift, eventually the boat will reach a balance.

[@iansmartel5473]

On full size hydrofoils there are trim tabs for the steering.

[@onewire59]

You need to check the angle of attack on the rear foil. It looks like it's angled downward and that will cause the rear of the boat to dive rather than rise up.

[@donaldasayers]

You need fully submerged straight foils with active control of individual foil angle of attack. Should be easy with an arduino, a plane type auto pilot and a small radar to establish height above the water. ;-)

[@gaius_enceladus]

You should try making a *catamaran* version (or even a trimaran!). Since they would be much more stable, you could really focus in on the hydrofoil side of things - no need to worry about stability!

[@rexaredim]

Hello. Waiting for the next video l. Good luck. On your helicopter 😀😀😀👍

[@OzAndyify]

Looks like a bit of tweaking of the rear foil's pitch angle will get the mk1 up. Please continue!

[@NBC_NCO]

Aim your tail foil the other direction. From the short bit I could could see of it... its driving the rear of the boat down forcing the nose up vs lifting with the front foil . In a airplane this ,your current would work fine.

[@modelrc9500]

What you need to do is tilt the back foil up (like the opposite of a wing on the back of a car)

[@borissabo2923]

Hi, nice project . I saw that you have roll stability problem. The thing is , that you have too big V angle on outer foils, so lift goes directly towards Center mass, it should go higher than CM , to be stable. Try to reduce angle by 1/2

[@JayH275]

I think removing the horizontal part of the front foil and rebalancing it would probably work. The reason the mk 2 was so unstable was because it rose too high on the front foil, which meant that the angled parts of the foil weren't being used as they were mostly out of the water. So the craft was essentially balancing on the fairly narrow horizontal part of the foil and not using the angled sides for stability. The issue was worsened by the mk 2 having a fairly high centre of mass due to the wooden construction. Because of this heavy weight the foil would stall when turning the craft since a lot of the weight would be transferred to the angled sides of the foil, which weren't actually in the water and weren't supporting the boat. The mk 1 didn't suffer from this due to it's light weight. It was also essentially surfing on the foil, instead of foiling. I would suggest two short horizontal foils on either side of the boat, as seen on the USS Flagstaff PGH-1.

[@BaddaBigBoom]

Looks like great fun! I have a couple of Aeromodeller books from the 1960s that have some pretty radical hydrofoil designs, I think one or two of them may be Jetex powered, I'll see if I can find them. I'd quite like to make a working scale model of Bluebird, maybe with a couple of design modifications to avoid what happened in real life :-( Thumbs up/subbed.

[@marshal7102]

You should always use a rudder with a hydrofoil. differential thrust works better with airplanes and quad copters. The rudder will help initiate a lean to the direction of turn by moving the stern in the opposite direction of the turn.

[@Taverius]

I don't think you're actually generating hydrodynamic lift yet, but do keep in mind the different aspect ratios of the foils will cause the higher aspect foil to stall first. It's also going to cause one to generate lift before the other. For simplicity, use similar aspect foils front and rear to start with. Also, flat rear foils cause the rear to lose lift and sink in a turn, unlike the front.

[@djquick]

Change the direction of rotation of motors on the Mk II. It will help it to bank into the direction of the turn when using differential thrust.

[@johnparrish9215]

Something that is very fast and very stable is the Australian Foil Assisted Catamarans. Not quite as fast as a true hydrofoil but very stable and easy to use in real life.

[@thercproject9309]

The differential on the mk 2 were causing roll, you should use the mk1 counter rotating props and mix is with steering so it leans into turns Sweet video as always!

[@martindinner3621]

So intentional torque steer? Cool idea!

[@SqueezeboxOfDelights]

Nippy McShippyface

[@GunganWorks]

Nippy McCyberface

[@hoppotopopticus6793]

I wonder if it would be feasable to build something that rises out of the water as a hydrofoil, then utilizes ground effect to cruise like an Ecranoplan.

[@martinndirangu2844]

Cyber boats...😹😹🔥🔥💯

[@tomaruba]

this is awesome. Is there going to be a Mk 3

[@fergusstockman542]

the nippy shippy is more lick a hydroplane than a hydrofoil when it gets up to speed the front wing skips over the water it doesn't use lift.

[@diveflyfish]

Would adding a "air Thrust modulating" elevator help keep it on step?

[@guritche]

Very cool

[@sebastianobeltrami8742]

Great project guy. Sebastiano from Italy

[@Project-Air]

Thanks Sebastiano!

[@mdriyasatali]

Very nice

[@colaoliver1587]

My father was a hydrofoil test engineer in the 60's so I grew up with the things. I watched your video and it appears the front foil's lift has more to do with the angle of attack of the foil than with the hydrodynamic forces due foil shape. Like a hand out a car window. The bow of the craft pops out of the water at a very slow speed and you can see the foil bouncing over the water with water splashing over the foil at higher speeds. In short you have the illusion of a true hydrofoil. If there was true lift from foil shape one would expect the bow and stern of the craft to rise out of the water evenly. I had similar issues with models I made and pulled through the water as a child. I would encourage you to continue your work. Find a foil shape that really works at the speeds you craft will go. Too flat, no lift. Too much shape cavitation at speed and loss of lift. May require some clever testing. If there is true lift due to foil shape the foil will rise to a point where at a given velocity lift equals load and the craft will move smoothly over the water.

[@colaoliver1587]

@mw w I do not know the design parameters, however I just Googled "Hydrofoil Foil Sections" and all manner of papers popped up. Have look at this site: airfoiltools.com/airfoil/details?airfoil=e817-il. This should keep you busy. Good Luck C

[@skippyfpvexperimentalrc6755]

Yay another video

[@1212354a]

I had such high hopes for the Mark 2! It looked the part, but didn't perform. Reminded me of a flying boat with the props too close to the water. All hail the "Nippy Shippy!"

[@Project-Air]

Same here! It's just sometimes how it goes. The Nippy Shippy was a reminder, however, that simpler and more basic is sometimes better.

[@westcoastrider3008]

On the mark one, I think if you change the rudders planning angle , you will rase it.

[@campanaro_99]

I like how this channel is called projectAIR

[@johnnyllooddte3415]

2 solutions.. 1.. change the angle of rear foil 2..you need a keel(s) in the water to stabilize both boats.. you can put a1/4- 1/2 inch keel on both sides in front foils and 2 on the ends of the rear

[@johnnyllooddte3415]

just look at the new race sail boats

[@Fm-ss4uj]

You can attach some foam to the bottom that will lift it higher out of water making it easier for lift.

[@absodell5872]

what are your top flight spots

[@kenj7153]

looking at the video I am thinking the front foils should be moved a bit further forward. The balance should be better then

[@robertvanderpolii5746]

I have 2 observations. A. At some point it looked like the foils stopped providing lift due to shape and started hydroplaning on top of the water. B. I think the stability would be improved by eliminating the flat section in the middle of the forward foil and extending them out further laterally. Looking at early full sized hydrofoils that didn't use active control, the forward foils tended to have lots of dihedral, which would aid in stability. www.navsource.org/archives/09/78/09780113.jpg upload.wikimedia.org/wikipedia/commons/9/91/HMCS_Bras_d%27Or_03.jpg

[@atomicsmith]

Slight change to the rear foil's angle of attack??

[@jamescunliffe9872]

Adjust the thrust angle of the motors so the rear end can climb out of the water,ie counter intuitive nosedive!!!!

[@laprepper]

Ice on the lake, Christ man how far North are you over in the UK? 😄😁😂

[@catwithabat7163]

This is cool

[@dannyh.s.1936]

Well I’m not that intelligent with what you do but here are my suggestions for Hydrofoil MK II’s design fails: you could try put 2 counter-rotating propellers that could have adjustable speed for one to add in steering. And as for the water-spraying problem just lower the propellers.

[@alecbruyns4490]

A long screw could be used to adjust the angle of the rear foil. The bottom of the front foil is too narrow. It should have a wider base, for stability.

[@villiamjohansson4219]

Maybe move the props a bit to the front i have a feeling they are pushing the tail down

[@jacknewby3892]

Wait wait wait wait wait, I don't know why but I was under the impression that you were already using differential thrust. God dam it that's usually what you do when you have a twin motor craft.

[@Aboriginal_Alien]

Dude your nailing the concept here just add a sail and you have the basic form of the future of global transportation of consumer goods. Imagine massive solar powered sailing hydrofoil Ekranoplan drones driven by AI in concert with weather satellites transporting global resources!

[@eslanek785]

You need to change the angle of the motors, they have to point their nose down, because when the hydrofoil lifts from the front, the motors go up, and they do a plane effect, and try to take off. Maybe putting the motors in the front will help with water splashes and with stability

[@jdubbfam37]

Would it still be the same if you where to put the props in the front ? And make them adjustable through a servo?

[@jdubbfam37]

Front pul rear drag I'm guessing center of gravity?

[@964cuplove]

Isn’t the high Position oft driving force contributing to the turn instability ?

[@72mardy]

Thats what I was wondering

[@GamingLegend377]

On the mk 2 add 2 mini sub fans on the bottom and remove the fans on the top

[@ganeshfakatkar]

Main advantage of airboat is there are no immersed part, which helps it operate in shallow water, marshy area and ice. Hence, try aerofoil instead of hydrofoil. Anyway, I liked your experiment.

[@_improve_achieve_]

mate listen. i wouldnt mind to see a rocket on a boat/\. love u ur actually amazing

[@scottstewart5784]

Is it just me, or does the front foil on HMS Nippy Shippy (AKA Nippy McNipFace) seem to be on top of the water rather than under the water? It looks like it's skipping over the water. Is that the intended action?

[@quik3199]

I think you should make the front hydrofoil the same on the back

[@MrJhalmoes]

Are the props contra rotating?

[@didierneeferc]

Makerknife!!!! i got the red one!

[@thomasaltruda]

I don’t think the front airfoil is stalling, I think it doesn’t have enough angle of incidence, and when the rear of the boat rises, the angle change of the boat puts the front foil at a negative angle, sucking the front down.

[@clayman0430]

Isn't center of mass usually in front of center of lift in airplanes?

[@austingonzalez1148]

One recommendation for better videos. At the end, describe lessons learned/what you're going to try to improve next. Tom Statton does a go job of this and at the end of the episode I'm usually thinking about whats going to happen next. This ending felt like you're done with hydrofoils.

[@Project-Air]

Thanks for the feedback ☺️ I am pretty much done with hydrofoils for the time being though.

[@unknownip6741]

"water in ma wellies"

[@martindinner3621]

You may want to take a look at Alexander Graham Bell's work on the HD-4. He was using a different style of surface piercing foil, but he was approaching it from an aeronautical/air boat angle like you are. Not finding much hard data on it, but found some good stats and two pictures of the scale prototype. americanhistory.si.edu/collections/search/object/nmah_844113

[@jojoAW101]

"I'm sure nothing is going to go wrong there" haha well we'll see

[@Project-Air]

😁

[@Raycefan]

While flooring the MKII didn’t help, it was hilarious

[@sammwangi7565]

am not a huge expert or anything but i think you could 3d print something to protect the fans from water should be light as well you could look it up on thingiverse

[@diogonunes1865]

What if you remove the bottom part of the front hydrofoil, would it make it more stable?(mk2) Or if you have a larger rear hydrofoil, would it be more balanced?(mk1)

[@Project-Air]

I definitely think adding some rear lifting surfaces to the MK1 might help - however as I mentioned in the video I really like the way it performs at the moment despite it not behaving like a true hydrofoil. ☺️

[@diogonunes1865]

@@Project-Air also, just wondering, if you have a wingtip type of device in the tip (as the name... suggests...) would help prevent water going to the propellers

[@philliplarocque9328]

Love when people say it's very cold and I survive yearly with usually a bunch of -40c days lol

[@philliplarocque9328]

Like the video though.

[@sh.erms_3923]

now lets consider the fact that PeterSripol made a tugboat a hydrofoil first try

[@Topn08_]

Well I noticed that you were mentioning my name during the video😂

[@air-headedaviator1805]

Nice

[@BEUNanim]

You are stupendously awesome I

[@garyjohnson4575]

Maybe you need more weight in the foil, like the keel on a sailboat...