Can wheeled vehicle run on the surface of water at high speed?

[Wavewacker]

Actually, I "skipped" a concrete block throwing it off the back of my boat, I've skipped round pebbles, rocks of varied shapes, they don't need to be "flat" they just need a surface area that will "glance off" the water surface.

I have no idea of the physics involved in reducing friction of any surface over water, I might suggest grease or air, either may work.

I'm still at a loss in understanding why this has any practical application, if you can explain that I'd be interested.

 

[portacruise]

Yes, I believe just about anything can be made to skip when dropped into water from a moving boat, depending on how much power is being used to propel it. But I haven't tried it from a stopped boat, though I expect most of those things wouldn't skip as much as an arm thrown flat Rock. I used to be able to skip a carefully chosen Flat Rock 5 to 7 bounces using my arm throw. The Flat Rock will have a spin to it so that may be part of it. I can't do those bounces with a Round Rock and I haven't tried it with a concrete block- but wouldn't expect five bounces.

I can't see any practical applications at the present time either, but who knows what surprises lie in the future..

 

[jehardiman]

https://www.researchgate.net/publication/2168050_The_physics_of_stone_skipping

 

[portacruise]

The 2014 Stone Skipping World Record - Kurt Steiner's 88 skips | The Kid Should See This https://thekidshouldseethis.com/post/the-2014-stone-skipping-world-record-kurt-steiner-with-88-skips

If a water vehicle could bounce in the air like a skipping rock, it would save energy, compared to the high power continuous sliding that is being done in some of the previous videos?

 

[mitchgrunes]

It's possible no one has yet made motorcycles buzzing you closely on the water illegal, because it isn't common yet. The motorcyclist in the Pipe Dreams video was buzzing boaters. I sure hope it doesn't become common.

I submit to you that the motorcycle is effectively a PWC, and should follow the same rules.

In Maryland, "A PWC may not be operated at greater than 6 knots (6.9 miles per hour) within 100 feet of another vessel except in a crossing or overtaking situation in accordance with the navigation rules." See also.

In New Jersey PWC are barred from "Operating a speed such that the PWC cannot be stopped safely" - the motorcyclist CAN'T stop safely, because he would sink if he stopped.

Regardless, if it becomes common, they should to be banned if they behave like that.

One paddle conveniently held at neck level as the motorcycle passed could have taken him down. If one buzzed by me that close, I would be frightened, so that might have been instinctive.

Let me see if I understand how it worked: The treads in the tires act like paddle-wheels, and drive the motorcycle forwards. It might not work with normal treads. The two little skis next to the wheels are the reason the motorcycle planes - it rides on the surface tension.

A snowmobile might behave in the same way.

Would it sink if something like an oil slick, or detergent (surfactant), weakened surface tension? Seaweed often produces calm (dark) wakes that resemble oil slicks, at least as viewed by imaging radar, presumably because they add something to the water. Maybe they could make the motorcycle sink too?

If a motorcycle or snowmobile sunk, it might not be very good for the engine...

 

[ondarvr]

The Pipe Dreams video is just that, a produced video. The "buzzing" of the other small watercraft was part of the production to highlight the differences. It wasn't just filming some guy on a joyride, and this isn't common, it was done years ago and people aren't really pursuing it as an actual activity, more of just a stunt for attention and advertising.

Proving that what is possible in traveling on, under or over water isn't always a practical solution.

 

[mitchgrunes]

The Pipe Dreams video is just that, a produced video.

Maybe so. But there are a fair number of people who watch videos, then try to copy the stunts.

Here is another crazy water stunt video, claiming to show water running, though I'm not sure it isn't fake:

And there are others that "cheat", by using the power of a PWC - much like bare foot water skiing.

But they don't show someone making a nuisance of themselves.

Now this one I believe.

 

[slboatdesing]

I'm still at a loss in understanding why this has any practical application, if you can explain that I'd be interested.

All very interesting, running on water.

The simplest way to explain this is as follows: see how the water skier skis on water. If the skis were wide enough, he would maybe be able to ski with a smaller angle of attack for the skis.

How do you reduce friction between the water and the skis? Teflon? Water repellent substances? What if you attach rollers to the underneath of the skis- would the ski boat be able to pull the skier with less power applied? If so, that means that it works, somehow the coefficient of friction has been reduced between the skis and the water.

My initial idea for reducing the skin friction between skis or a boat and water was to pump water through small holes in the bottom of the boat - like the boundary layer control used in aircraft wings such as the Blackburn Buccanneer.

An alternative would be to extract water from under the boat at high speed so that there is a reduction in skin friction.
The theory of a rolling water contact surface could be tested more easily, however.

The question is simply how to reduce skin friction between a boat surface and the water and will it be 'worth it'.
There must be some some boats need 400 hp to move at 35 - 70 mph when a car can do maybe 200 mph on 400 hp.

"Boundary layer suction[1] is a boundary layer control technique in which an air pump is used to extract the boundary layer at the wing[2] or the inlet of an aircraft. Improving the air flow can reduce drag. Improvements in fuel efficiency have been estimated as high as 30%."

- Wikipedia

Edit: here we go:

In February last year, Mitsubishi Heavy Industries (MHI) and transport company Nippon Yusen Kaisha (NYK) announced plans to investigate the effectiveness of a system intended to reduce the frictional resistance between a vessel's bottom and the seawater using a layer of air bubbles.

Mitsubishi reduces friction on ship hulls by blowing bubbles https://newatlas.com/mitsubishi-air-lubrication-system/21196/

 

[portacruise]

"The two little skis next to the wheels are the reason the motorcycle planes - it rides on the surface tension."

As I recall, surface tension is an extremely small static Force compared to flotation. Planing or skimming are much larger Dynamic forces which are allowing heavier than water craft to stay above water once the minimum speed is met and maintained? That's the way I understand it anyway...

 

[portacruise]

"How do you reduce friction between the water and the skis? Teflon? Water repellent substances? What if you attach rollers to the underneath of the skis- would the ski boat be able to pull the skier with less power applied? If so, that means that it works, somehow the coefficient of friction has been reduced between the skis and the water."

Somewhere in the archives, there is a discussion about these aspects. Special swimsuits used by Olympic swimmers were discussed, a vehicle with multiple rollers was evaluated, and fast sailboats with air lubricated hulls were presented. No astounding reductions in friction were discovered, as I recall, considering all of the trouble and energy draining complexity that was required. Not many practical uses except maybe the special situation passive air pressure lubricated sailboats, and super fast, hyper cavitating torpedoes?

 

[mitchgrunes]

"The two little skis next to the wheels are the reason the motorcycle planes - it rides on the surface tension."

As I recall, surface tension is an extremely small static Force compared to flotation. Planing or skimming are much larger Dynamic forces which are allowing heavier than water craft to stay above water once the minimum speed is met and maintained? That's the way I understand it anyway...

Actually, I bet you are right. And when you plane, you are typically forcing water downwards, which can create a lot of force - probably way more than surface tension.

I'm uncertain about creating bubbles under a boat to decrease friction. Whitewater boaters have drowned when they went into airy foam that was too deep. Boats and oil rigs have sunk when something released a lot of air bubbles. If a boat sinks deeper into foamy water, would that decrease friction, or increase it?

Some whitewater craft (including my EZG-50) have used a more or less circular concave indentation (sometimes called foam pile) in the middle, so they can rotate more freely, but I'm not sure if the foam plays much of a role.

But hovercraft, which create a large somewhat high pressure partially enclosed air zone under the boat, obviously exist. So do sea planes. Both can go pretty fast once they lift out of of the water.

 

[slboatdesing]

Just thought I would post. Flintstones.

This is the basic question: why does a car only need 25hp to travel at 55 mph and a boat of similar size and capacity need 250 hp to travel at the same speed? (I made those figures up, but I would be glad to be proven wrong).

Hydrofoils, tunnel hulls, also hovercraft. What about SWATH boats don't they have less resistance?

 

[portacruise]

Just thought I would post. Flintstones.

This is the basic question: why does a car only need 25hp to travel at 55 mph and a boat of similar size and capacity need 250 hp to travel at the same speed? (I made those figures up, but I would be glad to be proven wrong).

PC: all of a car is moved through air, compared to a boat which has at least part of it normally moved through water which is 784 X more dense then air- so a lot more resistance losses when in water. Also car tires normally have close to zero slippage when propelling against a road, compared to a boat prop having much larger slippage against water.

Hydrofoils, tunnel hulls, also hovercraft. What about SWATH boats don't they have less resistance?

Depending on design shape, SWATH hulls can have more resistance than a normal Hull, because they are completely submerged in water and have struts, whereas a normal boat hull is not completely submerged./QUOTE]

That's the way I understand it, anyway....

Ps. Here's a SWATH comparison presentation for those that might be interested,

SWASH SUBMERGED SINGLE HULL WITH ACTIVE SURFACE STABILIZATION https://www.bluebird-electric.net/SWASH_Submerged_Single_Hull_Active_Surface_Stabilization.htm

 

[comfisherman]

Ports cruise is being very nice...

25 hp to go 55 is flat level light weight small motorized vehicle on level hardpack. A tiny speed boat with a light weight hull will do admirable if you keep the weight down. Problem is water is rarely as smooth as tarmac. Ever run a motorcycle on sand? Put a fat paddle tire in a bike that goes 50+ miles a tank on sand.... maybe 20 miles if you find good sand less if it's soft and dry. Those 200 mph cars would do poorly in even a mild chop....

 

[mitchgrunes]

What if you take your Porsche, add a little flotation, and put a marine motor on the back.

It will rust. But if you can afford Porsches, maybe that won't matter. You can just keep replacing them.