Toroidal propellers

Interesting,… in what seems like another life, (or more accurately, a lifetime ago) earlier in my career, I had done a prototype propeller with the possibility of being used by the U.S. Navy on the premise it will reduce cavitation for our silent service.

that is an interesting design… that may be as difficult to manufacture. I like to see data on that.

What works in an incompressible fluid does not necessarily translate well to compressible fluids.

And then this guys goes on to skewer someone from MIT who posted something about toroidal propellers for aircraft, etc.

It is not possible to make a propeller (or any device, for that matter) 4 times as efficient as something that is already 60-70% efficient. Someone is being really gullible here. Also, 10x normal cost is likely a deal-breaker.

I agree, I do like to see the data on that, there is one thing that may be a possibility useful, and that is how much cavitation is created.

There are some reports of less efficiency in use on drones. It could be that the airfoil shape was not optimum. Or the toroidal propellers may have a larger moment of inertia. Acceleration and deceleration for control of the drone may take more energy.

https://oscarliang.com/toroidal-propellers/#:~:text=In%20terms%20of%20efficiency%2C%20the,of%20its%20original%20flight%20time.

10x normal COTS price is a dealbreaker?

What, have you never been involved with an equipment sale to the US military?

I don't think we will have a real break-thru on ocean propulsion until we fine and use some kind of interface, between the hull and the water. We need slicker slippage. And an adjustable/controllable interface would be great for braking and turns. Perhaps some kind of nano surface. Or micro bubble surface.

"Done right, injecting air into the boundary layer in this manner can result in sizeable reductions in the skin drag ships experience, and in turn a reduction in the power required to propel the ships forward – potentially over 20%, even accounting for the energy requirements of pumping the air."

https://www.mewburn.com/news-insights/blowing-bubbles-to-cut-drag-and-clean-up-shipping

I believe Scandinavian ice breakers has that to reduce slippage as it travels over the ice… that’s on the hull.

In a physical metallurgy class we were taking, our professor was a sailing enthusiast, he would get off track when we’d mention the America Cup or someone…

and he would talk about where some of the Australians on their win on Americas Cup Race, had develop a surface paint(?) that was a shark (skin) type surface on their hulls to help guide them through. (among other advances)

I’m looking for a link

https://www.nytimes.com/1986/10/05/magazine/racing-to-bring-home-the-come.html

Check out"Supercavitating torpedoes:

https://www.youtube.com/watch?v=o0sg_3hoagE

Work is also being performed on supercavitating projectiles to eliminate underwater mines.

Last I heard,the US had solved the steering problem on the supercavitating torpedoes.

I hope that technology was not leaked to the Chinese or other adversaries.

There is also the use of hydrophobic coatings.

https://www.youtube.com/watch?v=EQCzO4RfZAM

"Radically quieter than traditional propellers in both air and water, they're also showing some huge efficiency gains."

..."One key issue with multicopter props is their annoying noise, which is often described as "whiny," because much of it sits right in the same frequency range as a baby's cries. Humans tend to be most sensitive to sounds between around 100 Hz and 5 kHz. This makes evolutionary sense; it's where we hear vowel sounds that are key to verbal communication. But it's a key issue if multicopters are going to fulfill their potential and fill our skies with fast, cheap, clean aerial delivery services. Residents and lawmakers don't want to add more annoying noises to urban life.

A team working on a silent, ion-propelled plane at MIT's Lincoln Laboratory found itself wondering whether prop noise in multirotors could be mitigated with differently-shaped propellers."...

...""The key thing that we thought was making the propellers quieter, was the fact that you're now distributing the vortices that are being generated by the propeller across the whole shape of it, instead of just at the tip," says Sebastian. "Which then makes it effectively dissipate faster in the atmosphere. That vortex doesn't propagate as far, so you're less likely to hear it."

Propeller noise can be somewhat addressed by placing rings of acoustic treatment around the circumference of a prop's path, which can also act as prop guards from a safety perspective. But these add parasitic mass, reducing battery life, and they can also catch the wind in outdoor situations, making the drone work harder to stay stable.

The team analyzed these weird-looking toroidal props to see whether there would be a thrust efficiency penalty. Apparently not: the team's best-performing B160 design was not only quieter at a given thrust level than the best standard propeller they tested, it also produced more thrust at a given power level – pretty remarkable given that standard props have more than a century of development behind them and these toroids are at a very early stage, with plenty of optimization yet to come."...

https://twitter.com/i/status/1611438712683958306

..."It's unclear at this stage whether designs like this might be relevant at a larger scale, replacing traditional propellers on fixed-wing aircraft, or indeed on electric VTOL air taxis. The latter already appear to be significantly quieter than helicopters, but if they end up flooding the urban airspace with fast, cheap, green aerial transport, every decibel of noise will count when it comes to public and regulatory resistance. The question there, really, is what kind of frequencies these larger props will occupy in the audio spectrum, and whether the toroidal props shift the sound in a human-friendly direction."....

..."Sharrow Marine has been getting frankly spectacular results from boat propellers that use toroidal loops instead of standard blades. After several years of development, the company has now tested its props against hundreds of standard propellers, and the difference is incredible. Sharrow's props simply don't create tip vortices – a major source of energy loss and a surprisingly large component in the overall noise of an outboard engine."...

..."Vastly reducing the amount of fluid that "slips" out the sides of a propeller rather than being pushed through, the toroidal props suck more water through, and advance a boat further, per turn. They regularly double the speed a boat can achieve at lower and mid-range RPMs, radically broadening the effective rev range of the motor. And they reduce fuel consumption by somewhere around 20% – a seriously big deal given the huge energy requirements of propeller-driven boats and the scale of the industry."....

..."Sharrow is already selling its toroidal props, CNC machined to fit a wide range of common outboard motors from most major manufacturers. The drawback here is price; they cost US$4,999 a pop regardless of which model, where a regular propeller might go for closer to US$500. But again, this is a pretty small component in the overall cost of many boats, and given their voracious appetite for fuel, the outlay may well pay for itself in short order as well as making the ride a lot more comfortable for the people on board, bystanders, and for marine life under the surface."...

https://newatlas.com/aircraft/toroidal-quiet-propellers/

I don't see why these can't be cast or even stamped out in pieces and welded together...bring on the cheap Chinese copies...$5 grand, shirley you can't be serious

I can buy a lot of fuel for $4,500 even at Biden prices.

Not to mention the prop is worth double of what my '92 Wellcraft with the six-banger I/O.

How fast you think you could cut the driveshaft with a plasma cutter...? Gone in sixty seconds...

All it really takes is a screwdriver for the tabbed washer and a socket on a battery impact wrench. I'd estimate gone in twenty-five seconds.

25 -25 I now have 25-- can someone give me 20...going once,going twice,,,gone in 25 seconds.

..."When will you be able to spin a Sharrow on your own boat? Very soon. Though Sharrow has custom-milled propellers to date, the high price ($5,000 to $10,000) has prevented them from entering the recreational boating market thus far. But Sharrow had the first MX-1 built via a casting process on display at the show. Pricing has been set at $2,000 for cast stainless-steel models, which Sharrow says can be reserved now (with a $100 deposit) and will be delivered by spring 2021."..

I wonder what happened with the cast models...?

https://boattest.com/article/yamaha-cast-and-sell-sharrow-propellers

So I guess Yamaha is selling them now as an option...cast SS

https://www.boatus.com/expert-advice/expert-advice-archive/2020/august/a-breakthrough-in-propulsion

I just thought of something. Go to a jet ski racing forum. I'll bet they are in use there. They will pay the price.

Not necessarily, in a jet ski the propeller or impeller, is already encased, might not make much difference at all...

I doubt that will stop them. I don't know anything about jet ski racing. But I do know what's it like to get into something like that......when the juices flow. And when the juices flow.....the juicer will look for an edge. I'll bet they have already tried. If they are anything like hot-roders or PC gamesters. Or any juice competition. I used to get a lot of juice with hardware programming. And running propulsion reactor drills.

But my juice has long gone.

Well I think testing this new design against a double prop setup would be closer to an apples to apples comparison...

https://www.boats.com/reviews/sterndrive-show-down-volvo-penta-duoprop-vs-mercruiser-bravo-iii/

Here's a design that adds a couple more impellers...

This is just cool looking...

https://www.quora.com/Can-a-boat-be-designed-to-make-use-of-jet-propulsion

The Navy Seals Mark V Special Operations Craft (SOC), uses Hamilton Water jets for,… ah… Loitering… but when they need to be somewhere in a hurry, then they use their twin 3000 horse power German Built MTU’s engines with surface piercing propellers…

We had hired a UK company to design the craft, Cougar Limited… the speed boat of choice by of all people… drug runners…

The shipyard were I worked, we did one of the prototypes, since winter was coming we shipped our prototype to Florida and did the trials.

I was called in on a Saturday, to redo the rudder and make it 6” longer and and buy a ticked to have it flown it to Florida… actually had to buy a airplane ticket where it had its own seat so it’d get there.

the reason was when you opened her up, it literally raised so high, it started skipping like a flat stone on water.

The performance was so high, in the open cockpit, the seats for the navy seals, was actually F15 fighter jet seats. Buckle up butter cup, we’re going on a trip.

https://owlcation.com/misc/Fastest-Navy-Ships-in-the-World

Both versions the Freedom Class and the Independence Class of the LCS is what one would call a ‘Jack of all trades, and a Master of none”

that’s why they are decommissioning the LCS’s faster then they can build them.

I always thought these boats were going to be big...

I think not enough R&D was done, I would have changed a few things....maybe they'll come back around...

It is big…. For Indian Casinos on islands… that and hover crafts…

One thing, way back when like the special ops crafts gos with speed boats all together.
when we were in a meeting with the Mark V, the engineers et al… were all patting themselves on their own back. And what a great SOC they designed, and that it’s virtually flawless.

I said, like I do here, ‘rained on their parade’…

that the defense of these boats are simple and cheap… all the enemy has to do, is cut a few logs, and float them in the water, and a boat going over 60 knots, like the MKV it’ll be under water in 5 seconds after hitting it… complete silence came in the meeting.

I did start their hearts again and gave them a breath and said, they could use the Hamilton WaterJets and sneak in with out being challenged…now sneaking out that would be a challenge…

I did say that because, the Navy would same thing, and management has to prepare for questions like that.

https://www.autoevolution.com/news/futur-e-hydrofoil-electric-boat-flies-on-water-like-a-supercar-oozes-sophistication-167701.html

Great for shallow lakes… not so great with 3-4 foot swells…

The one thing that I always come back to thinking about is the efficiency of this design. In the hydrofoil boat, you have to use drive energy to generate the lift to raise the weight of the boat above the water through a combination of the foil shape and angle of attack which of course represents drag through the water.

Many hydroplanes of course usually have some sort of "tunnel" that I assume generates some lift which of course is now air resistance plus whatever wetted surfaces are still touching the water. Displacement bouyancy would seem to be more efficient, but in many types of racing, the prize is for finishing first, not burning the least amount of fuel.

https://www.fishing.net.nz/fishing-advice/general-articles/boat-propellors-101/