Hi Nick, we just kinda met.... I'm still watching my first video, just paused it, then checked out your channel and I must say I'm happy to meet you. Very in-depth direct info, very well delivered with passion. Well done and I'm excited to learn more. Thank you.

man, thank you so much.. ive been trying to design a waterjet for some time and theres so little information on this subject online, and out of the blue comes this guy and answers every question i had

I was picking my nozzle when my wife handed me a tissue and told me I was being gross . So when you pick your nozzle try to do it in private . DIY tip of the day .

Waterjet for dummies. Deepest respects from a physicist and aviation inspector :)

My father, a boat builder in New Zealand in 1964, accepted Hamilton's, and the world's, first ever jet boat, as a trade-in. He passed it on to Hamilton himself. At the same time he was building a high country deer recovery, flat bottom, 25 footer with two Chrysler Interceptor V8s, with race cams and twin, four barrel, Holly carbs, totalling 800 horsepower. The fastest and most powerful of its day. It could carry a ton across wet gravel, fifty feet, and then into a foot of water.

I just found all your videos with this one. THANK YOU! I feel like I am being informed.

Just today I was designing my waterjet and I had questions, like a light from heaven this video appeared, well in my search results. It's like he knew 4 years ago this day would come, uncanny.

You're the man. I'm from the Philippines and is designing a boat propelled by a jet out of recycled materials.

Great video. Basically confirms everything I already know. And how I know is about 12 years ago after years of racing rc cars I had decided to get into boats, but I wanted to custom build my own. Part way into build while researching stern drives I came across jet pumps made by a company called Graupner. Having a huge love for jet engines I was immediately intrigued. I ended up purchasing a 29mm jet pump with reverser for $80-90. It came completely unassembled so I had to put together which sounded easy (YEAH RIGHT!) Was a pain cuz there was only fraction of mm between impeller & side wall. So lining the drive shaft had to be PERFECT or impeller would scrape. Almost didn't think I was gonna pull it off but somehow I did. All I know is in the years since that thing has taught me ALOT about both the physics as well as the design of those amazing things lol. I still have it which I've installed into a "drive-box" that I use to demonstrate to people. It might only be 1 1/2" diameter and about 10" long but when coupled with a 40k rpm brushless motor it will shoot water 40-50 feet. Impressive little thing. All I know is mostly through observing it and the video essentially just confirmed it all.

The first thing that came to my mind took me by surprise: This is way more more rocket science than your average boating. Instead of "biting into the water" prop style you are dealing with a reaction engine. Very intresting

Water is power source congratulations to everyone involved love sent in vibrations

Would variable angle of attack on the "fancy spiny thing" increase the efficiency range?

Variable geometry exit nozzle? Maybe not like the variable exit nozzle on a fighter jet, but more like the air intake on the SR71 Blackbird. More suitable for mixed flow pump.

One thing that comes to mind when thinking about this is, "why not have the pipe inlet on the front to reduce drag from water changing direction up into the pipe?" At least, on something other than a fast planing vessel where only the bottom of the hull is in contact with the water. I am guessing the reason is that skin friction inside the pipe would be a much greater effect than the gain (discounting the fact that you also have to slightly enlarge your hull to maintain displacement)?

That was great idea for getting rid of, or rather actually keeping the bubbles to stop the damage. Something I would have thought out.

Thanks for all the videos Nick! Very informative.

im studying to be a mech e and this stuff is so fun to watch thank you

Thanks for sharing your video with us, This is great information, I committed with a question on one of your past jet video, it’s almost like this one answered my question, the agency I work for is about to dump about 100k on a new trim setup, after they fail i will show them this video . Cheers

So much answers in this video. Thank you much!

This is really helping me with autonomous/RC robotics water vehicles

Thanks for putting sources down there 👍

I use a variable nozzle that actually changes shape long the curve to maintain peak efficiency. I also use a variable inlet. I use a variable impeller as well which adjusts as speed increases. thanks for these videos they helped me come up with some great designs.

Really informative video, Nick. You always make good stuff. I had one question though. You say that discharging below the waterline is bad because of the higher external pressure. But wouldn't the elevation change increase the stagnation pressure in the water flowing out the nozzle by just as much, thereby canceling that effect out?

Are there nozzles that are flat/rectangular ? A rectangular outlet could very it’s output width.

Good explanation and really motivating

The beginning made me laugh you got my sub bro good video

What if the stator blades double as the nozzle? The blades stop the rotation of the water and reduce the circumference for thrust. Remember, water doesn't like to be compressed. I had another thought: what if the impeller blades were spun by the outside (still inside the housing, just outside of the blades)? Maybe variable pitch blades too? This might help with the problems that hydroplanes face with the wings being under water.

To prevent cavitation, serialize dual impeller use 2 steps pressure increase.

Bow thruster advantageous and disadvantageous as for speed/torque to manoeuvre an object/overcome hidrostatic.

I need to click on your earlier waterjet explanations to find out what sized ships can benefit from them as opposed to propeller drive ships.

i would make the active rotary vanes in rings composing the chamber, not as a air turbine in the center, where it blocks the flow...

Your intro 10/10 ape instinct

Do you show somewhere an efficiency comparison between propeller vs. waterjet? the baseline efficiency is always difference between ship speed and speed of accelerated water from the propeller or jet..... I am also not quite sure what efficiency relation you are referring to in the slide shown?

Thanks for information about water jet .Simple.easy to understand

with standard bicycle gearing of course, 28 gears etc

Thanks for the video. It was very informative. I was thinking of putting 3 x 16mm water jets in a cake tin (to be removed with ease) to screw on the bottom of a surfboard. Gathering from this video it wouldn't work. I want to make a motor to get a 9"7' longboard moving at a reasonable pace to have a bit of fun at the beach with the kids. Any suggestions would be much appreciated. Regards. Mick

Great video as usual. Fascinating and compelling.

Hi there. Are there waterjets whose openings can be changed to match the speed like in jet fighter engines?

Srilankan students have won international competitions in waterjjets. That is why I requested this.

cant believe this video is free

Thank you, simple and smooth explanation

I am designing a surfboard with a water jet pump. I only need it to for short burst of energy. What I am trying to accomplish is a 5-15 second boost to help with catching the wave prior to take off. Where can I find water pumps to buy COTS type. Perhaps 1-2 inch diameter.

When a jet is working, its geometry is tilted, and so water comes into a chamber straight, and so exhausted with some angle into a surface. So, is it above or below a water line initially no more maters then imho.

Good video exactly what I was looking for

Thank you for this information.

Apreciate the educational videos.

Very interesting vid! Thanks!

Because a lily shape propeller moves a larger mass of water for a fraction of the power of a conventional one, why are they not used?

Thx 4 this very educating video, which resulted in me to following question: when my jet noozle needs to be above waterline(which makes completly sense to me), how do i determine my waterline during design/construction?

This is so educational.

What about inlet tube shape? Nozzle shape?- different shapes would make variable volumes much easier

I'm a novice here. Trying to learn as much as I can from a physical standpoint. So I may ask silly questions. Every time I think of jet propulsion I think of how it compares to sterndrives, or propeller drive if you will, and why the loss in efficiency compared to the sterndrive. On outboard motors I see for example 60/40 horsepower. So 60 engine horsepower but only 40 horsepower at the impeller? Or is this horsepower being measured by a different means, like thrust? Because thrust can be converted to horsepower in the case of turbine engines so I assume that might also apply to waterjets as well. I can't comprehend how 20 horsepower would be lost from the crankshaft to the impeller since it's a direct connection. My only guess is 20 horsepower is consumed moving water through a narrow passageway under high pressure, and what we get in return is 40 horsepower worth of thrust, if that makes sense. Whereas as the impeller moves a "low volume" of water under high pressure and velocity, the propeller moves a much larger volume of water at lower velocity and "no pressure", so to speak. It's simply under the water it's only job is to move the water rearward the vessel......unless you're going in reverse. First question, is my statement correct, at least partly? Second, theoretically, could a waterjet be designed almost opposite of most current waterjets today where it moves a larger volume of water at a lower velocity and pressure (to a point) like the propeller drive, and be closer to the efficiency of the propeller drive? Yes, I'm aware of the concern about cavitation. For now let us pretend it isn't a factor. The point of all this is I do like jet propulsion but I HATE the loss of efficiency and speed compared to a propeller drive. I would love nothing more than to see the efficiency deficit addressed but until I do, I won't tolerate the loss in speed just so I can operate in shallow water.

This information is so useful that I can better design 3D printing waterjet

Okay, here’s a freebie……sort of!😜 You don’t like Bulbous Bows because of the thin parameters of usefulness? What if I had a way to negotiate that issue, and make it useful on almost any boat\ship you put it on?

So I have a couple of questions: 1. Could the inlet be placed at the front of the boat to utilize the pressure created by the bow wave to facilitate water intake, reducing the distance the water needs to rise before ejecting from the nozzle, and allowing for a more interesting configuration of engines, pumps and nozzles? 2. Is it absolutely vital to have the waterjet at the rear of the boat? For example on a large displacement hull could the nozzles be placed on the sides of the hull above the waterline with buckets to control the flow fore and aft thus making even the largest of ships able to "strafe" without issue. If the waterjet is above the waterline it wouldn't interfere with hydrodynamics. My biggest concern would be bucket wear.

I want to make a water jet unit for a 19hp engine what diameter should the impeller be? Is there some sort of calculator of how to build it otherwise it will just be a spinny thing in a tube

i wonder if anyone ever tought of putting a CVT gearbox on the back of the diesel engine. that way the diesel can run at its most efficient rpm ( 2000 rpm for example ) and the input rpm of the jet can be varied by the use of the CVT gearbox so basically the engine runs a constant rpm and then use the CVT to vary the jets rpm or have a variable outlet size like usd on military jet engines

I would like to thank you very much for your videos explaining how waterjet works and I am learning a whole lot. I am trying to design a kayak truster using an aluminum pipe of 2 inches diameter. If I want to create a nice jet what diameter would you recommend the nozzle to be? I came up with 2 inches to 1.5 inches reducer but I don't know how to calculate the ratio. would you be able to suggest something? Is 2 inches to 1.5 inches good enough compression or should I go from 2 to 1 inch? Thanks much

Hi, I am working on a pedal bike design for pedal boats and thought that a waterjet that you could design for something like with a Bafang mid motor mixed with a Spatium water bike as example. I think the jet would be possible

Can you please Nick make videos about Towing Tanks?!, the accuracy of the results compared to the post sea trials? Different types of tanks and latest techniques?? Thank you

Great explanation :) So now i have a question.. Im building an RC model of a yacht Project Infinty by Dorries yachts and because me being me this means that i'm not building a 1m model but a model that will be 3m long (1:30 scale) and i would like it to be powerfull enough to pull a skier on water (total weight of the model est. to be arround 120-130kg ) So how can i calculate how big impeller do i need and how powerfull engine to run it? (Im going to do it with dual jet powered by an electric motor I'd be very gratefull for any sort of information. Thanks

Can nozzles resize themselves based on water pressure?

Jetboards generally use a nozzle including stator vanes to increase waterflow velocity and efficiency. Commercial boards use boosterjet setup; the rider is controlling the board by shifting his/her weight.

About the outlet jet : when you want to move forward, wouldn't be more efficient to push yourself into a back solid wall (water = higher viscosity) instead of a gas (air)?

Have you ever seen the old French Mirage jets? They had a "mouse" that moved forward and backwards to alter airflow. Could something like that be used to alter nozzle volume? Have you seen how Banks turbochargers work? What about that idea for altering waterflow?

What about the efficiency of a propeller as a semi jet propulsion unit?? A propeller style jet pump without the nozzle. I am curious. Can it be tucked under the watercraft like a jet pump and be efficient??? Could this be your next content??

Is it worth using a waterjet on a British NarrowBoat (60ft v 12ft flat bottom barge operating in very shallow water with a max speed of 7-8 knots) Traditionally propellers are used but get fowled up regularly due to water debris.

Why not have variable nozzles, like the garden hose, or a modern fighter jet?

Hey mid design of some sort of board for water travel and ocean clean up in a fun way. Was wondering, does the angle of the impeller matter after the water jet is primed? my idea was to angle the impeller ( 45 dgrees maybe? for a guess) and have a larger then normal impeller, not deep inside the tube but closer towards to inlet, making a lower rpm possible, and washing away the cavitation! i figured that, if an impeller was angled, there would be a quick grab of the vehicle , so pulling down parralled to the angle of the impeller, but once primed the water jet then would still thrust forward. it'll be a personal water craft with very light parts, like an Eskateboard. the impeller could be mounted to shoot water straight up and fill a smaller tube directed out the back for thrust. i know i' have to test but some advice of the idea would help, think RC car that vaacuums at the bottom in order to drive up a wall, then a water shot out the back for propulsion! dope video, i'll definitly subscribe as i have quite a few water gadgets i have to develop! Thanks Jay Masters

Hi, would a Waterjet make sense for underwater propulsion (beneath the waterline) or would an old-fashion propeller be the better choice for that?

What is your guys's opinion of a variable nozzle kind of like the afterburner of a jet engine. It could give you optimal flow angles through different velocities

if the jet is above water, pushing against air wont push the boat forward??? :P

I was wondering if the principle of Dyson's bladeless fan concept can be used to propel water vehicle, especially a sub to reduce sound while increasing speed compared to conventional propeller design.

In jet engines and I think large ship propellers, we know that moving a large volume of the medium at a slow speed is much more efficient than moving a smaller volume fast. That's why jet engines have huge fans now. I don't see this mentioned in water jets, but they must obey the same principle.

hmm it's kind of interesting to see the nozzle trade off between speed and propulsive efficiency from rocket design also present in water jet design. IE: sea level nozzle need to be small so the exhaust pressure match the ambient pressure, while vacuum nozzle need to be gigantic because ambient pressure is effectively zero. There was some attempt to use an aerospike nozzle that turn the nozzle curve surface inward and let the ambient pressure form the shape of the perfect nozzle regardless of ambient pressure. Unfortunately aerospike nozzle didn't work out because rocket exhaust is way too hot, and aerospike has much higher surface relative to flow rate compare to a traditional nozzle. But in marine propulsion, I don't think cooling is an issue, so maybe aerospike nozzle could work in marine scenario, so you effectively have a variable shape nozzle that works for all speed.

Is there any research about the advantage to using toroidal shaped impeller blades in a jet system?

You stated that a fully submerged pump is BAD. So how does an efoil pump design work when placed close to foils? It is permanently submerged at that point. Does this mean they are highly inefficient? Commercial Efoils with jet pumps do exist now, so are they all underpowered/inefficient for torque and rpm specs similar to a prop driven efoil using same motor? Problem for me currently is that prop driven efoils are still illegal to use in Canada (but legal to sell). They must be a jet pump design to use without being fined $300. Thanks in advance.

Where is the cavitation video you mentioned?

In the case of a hydrofoil is it still more efficient to lift the water up above the waterline than to have it submerged?

great video. btw, I was wondering how they design their impeller blades. is it just like an open propeller? is does it have a special geometry in it particular for its application?

Idea was simple water comes in destabilize form a gas and continuing to fuel water if so .... Or fuel is key to igniting the jet flame ... H20 ... Is not really Oxygen alone but potentially ignitable....flame escaping the rear.. Terry Hawkerman. Building A mini jet engine was educational ..

Por favor ..( la traduccion al castellsno)

What propulsive effect does one get from the force of the water pressing against the sloped top of the inlet?

There one major flaw in this whole concept of waterjet, why use a middle/central shaft that gets in the way, and why not use a whole tube? Why divert the water to get inside in the first place ? Multiples outside spinning shaft can achieve much more power efficency then single central shaft. Also using multiple side shaft to spin the inner propeler means, you get more propeler surface, and no middle shaft in the way. Let the tube flow througj the water, as the water flow throw the tube. It's called a Tubemarine.

New subscriber... Thank for tje video sir

Are there any nacelle style water jets that look like submerged aerojets?

witch propeller use for moto engin 110cc ?

What if you change where the water comes from?

So if I understood correctly, all these outboard engines where a waterjet pump system replaces the prop driven lower unit, which are used on back of some boats for use in shallow water, are not being used correctly as the whole jet assembly is completely submerged ?

Buenas tardes Agame un favor y me dicen como pido uno para Colombia gracias

Very good!! Thanks for share!!

Great video. Off subject question....what's the purpose of the ring moving between hands during the video?

- What is the best Naval Architect? - The Nickest Architect is best Architect.

good video I hope you keep update :)

hi , would it be possible to use water jets on a personal sub , i'm in the middle of working out which propulsion system would be best and also the kind of battery set up to put in it , thanks

Hey nice video but how do we seal the water from entering the boat at such high pressure

Cool

Layman here: Can you make a video about the prospect of submarine jets?

The best is a screw pump jet. An engineering catalog should have a variety of screw pump s.

Excellent