30 ms·
Sharrow MX-1: Tipless propeller (2020)
- brk 4y agoSo far in unbiased real world tests the efficiency gains have been fairly limited,and. It enough to offset the increased costs. Note that I mention unbiased tests. There are some manufacturer tests comparing a boat with essentially a wrong prop to the Sharrow, and showing impressive results.
- edrxty 4y agoI wouldn't buy one for a pleasure craft, but even a small efficiency gain in ocean freight could turn the industry on its head.
- HenriTEL 4y agoMaybe the tech just does not scale for large propellers (it breaks, becomes less efficient or is too complicated to maintain). The company has been there for a few years now so if there was a real game changer I'm sure they would have accelerated much more.
- brk 4y agoLarge container ships already use variable pitch props.
- moffkalast 4y agoDidn't the US coast guard order a few to test on their larger ships? The efficiency gains must be credible for that to happen I imagine, though I can't find a good source for that order, and I'm not sure where I heard it. I'm just waiting for someone to make an RC scale injection moulded plastic version of it :P
- MichaelZuo 4y ago"However, extensive sea trials carried out by US website boattest.com on the new Sharrow Propeller MX-1 seem to confirm all of the above and show efficiency gains of between 9-15% over comparable 3-blade propeller designs. The tests were carried out on a 20ft Bayliner VR5 sportsboat fitted with a standard Mercury 150hp outboard engine, comparing Sharrow’s new tipless MX-1 against two market leading-competitors. Not only was it the fastest of the three (41.7 knots vs 40.8 knots and 39.0 knots) and the most efficient (4.6mpg @ 32 knots vs 4.2mpg and 4.1mph), it also planed earlier and outperformed them both at every 500rpm increment from idle speed to wide open throttle." Seems like the title is incorrect? The article only claims 9-15% mileage improvements along with vibration reduction and handling improvements.
- idiotsecant 4y agoNo, it claims 9 to 15% efficiency gains. A more efficient machine, with all else being equal, is more powerful at that same engine condition.
- MichaelZuo 4y agoEfficieny gains of boat propulsion translates into mileage gains... unless boats work in some non-linear manner?
- idiotsecant 4y agoImagine you have a propeller with an efficiency of 50% at a particular differential pressure. What happens to that lost 50%? It turns into heat. Now imagine you have a fancy new propeller with an efficiency of 99% at that particular differential pressure. All that energy that you were using making heat before is not turning into thrust. Your overall engine-propeller system is now twice as powerful at that same differential pressure.
- MichaelZuo 4y agoOkay, and?
- VLM 4y agoSmall sport boats usually operate way above hull speed in the the far non-linear region so an extra ten percent thrust will result in a far non-linear increase in speed. I'd believe an extra 15% of thrust would only make it 2% faster. Really small boats with really huge engines can push quite a bit past hull speed at ultra low efficiency, and that's the only numerical stats they're providing in the article, which is interesting. I wonder if performance is just as high at low speeds, below hull speed, where most cargo ships operate and all the marketing greenwashing is occurring. Hull speed is not "supersonic" but its a similar enough to rhyme concept, where the boat has a tough time pushing up or thru its own bow wave, sort of, so the max speed of a boat is mostly related to its length. Oddly enough the hydrodynamic variables all cancel out or whatever such that mostly all that matters is wetted hull length for hull speed. You'd superficially guess something like hull depth would matter or width or shape kind of like the stall speed of an airplane wing depends on its shape, but no, ships hull speed almost entirely depends on the wetted hull length. Just a weird hydrodynamics thing. Maybe an air craft carrier with 10 times the power could go 5% faster, but it would take 100x the power to get an AC carrier up on plane like a ski boat.
- AmVess 4y agoRun it through grass or weeds and then it won't seem so innovative. Also, $4300 more than a standard prop means that a single trip over an unseen gravel bar will be the first and last time anyone uses one of these.
- jpgvm 4y agoThat price was for essentially CNC milled prototypes, I imagine if they cast them they would be a fraction of that price.
- serf 4y agocasting that shape would require some kind of sacrificial mold like a sand-casting process. cheaper than billet, but not by much unless you're talking big industry scale. I wonder myself if it's small enough to use a laser-sintering print process to build.
- ISL 4y agoIf the two halves of a mold have some helicity, I suspect it is possible to cast such a shape. After all, the water also needs to flow through the prop, so too can the halves of a mold.
- Oxidation 4y agoEven if the geometry doesn't quite work out, it's also possible you could cast a shape that can be "unscrewed" from the mould and then machine a relatively thin layer from the outside of the cast part (relative to how much you have to machine from a billet). It'll need some level of machining anyway. Binder-jet printing of sand cores is pretty cool too.
- pifm_guy 4y agoSacrificial sand moulding is done all the time and is pretty cheap: https://youtu.be/lnHhP_kZ43k https://youtu.be/lnHhP_kZ43k
- 4y ago
- ggm 4y agoI don't see how it can be markedly more effective than a ducted propeller
- willnonya 4y agoEven a ducted propeller has additional drag at the tips which this design could eliminate.
- andrewflnr 4y agoI'm still curious if it reduces noise on drones, though. Can 3d prints stand up well enough to be used as propellers, so someone could test it?
- snshn 4y agoYes, ABS is supposedly strong enough for that.
- WrtCdEvrydy 4y agoI wonder if we'll see a 3d printable version soon. I'm thinking of putting it on the Mini 2 and seeing what happens.
- ISL 4y agoProbably not without violating a patent.
- hsuduebc2 4y agoI'm kinda sure that if he is not going to sell it they really don't care.
- moffkalast 4y agoIf you went around looking for patent and copyright violations on thingiverse you'd probably need to remove most of what they've got.
- simne 4y agoYes, You are absolutely right. Anybody could try any shape for scientific experiments, but sell copies and distribution of 3d models prohibited.
- dhc02 4y agoIndeed. https://www.thingiverse.com/search?q=Sharrow&page=1&type=things&sort=relevant https://www.thingiverse.com/search?q=Sharrow&page=1&type=thi...
- MerelyMortal 4y agoF... I remember sitting in a class one day and hearing that there would always be wingtip vortices on planes, and wondered if that could be solved by looping the wing around (to where it almost looks like a biplane). I wonder how many other ideas are being sat on because people don't realize its significance or have the resources (such as time or desire).
- ge96 4y agoBoxed or closed-wing
- MerelyMortal 4y agoAh, thank you! https://en.wikipedia.org/wiki/Closed_wing https://en.wikipedia.org/wiki/Closed_wing
- sandworm101 4y agoThere are still tips and vorticies, just not at these speed/size/power settings. The length of the blade is the biggest issue. These are effectively short blunted tips with a hole in the blade. Whether the improvements would translate to air, with all the associated speed of sound issues, is unclear. Another old option for eliminating such issues is to put the prop in a case, like a jet ski or most modern military submarines. Or just eliminate the concept of tips and turn the entire case. https://en.wikipedia.org/wiki/Rim-driven_thruster https://en.wikipedia.org/wiki/Rim-driven_thruster
- mint2 4y agoWow These look like fish dicers. Not to say that propellers don’t already dice fish, these just look the part too.
- rtkwe 4y agoFor small fish they’re probably about the same but they seem like they’d be superior for larger fish since they wouldn’t be able to get drawn into the middle so you’d have less strikes along the backs like you often see on whales or large sea animals.
- ChrisMarshallNY 4y agoThat was two years ago. I’m wondering what’s happened, since…
- bobm 4y agohttps://www.sharrowmarine.com https://www.sharrowmarine.com They still seem to be around. Not rocking the world yet but I'm surprised that they haven't come out with a cheaper model. Might be harder to cast than expected.
- ri0t 4y agoWelp, as someone else here pointed out, just print it, then: https://www.thingiverse.com/search?q=Sharrow https://www.thingiverse.com/search?q=Sharrow Which is what i'm going to try next year - for my smol electrical harbour pusher. If you have one of these fancy inconel printers that spacex uses, you could even print a steel version. And quite big ones, too.
- chrisdalke 4y agoAnecdotally (I'm familiar with the marine industry) they seem to be gaining popularity with the luxury center-console market, half as a fuel-saving metric but mostly because they're a talking point at the marina. In recreational marine these types of products tend to spread based on word-of-mouth and sell fairly low quantities but at higher price points. Related: Seakeeper (https://www.seakeeper.com/ https://www.seakeeper.com/), a fairly crazy gyroscopic stabilization system, wildly popular but fairly quiet in the tech world.
- alex_duf 4y agoWould you have knowledge of how well that would scale on a cargo ship and what sort of savings we could see there?
- chrisdalke 4y agoUnsure if this would scale up but as others have mentioned for large ships the operation is very sensitive to cost. Fuel efficiency is weighed against current fuel cost, cost to design a technology into a new ship or retrofit, maintenance, etc. That said, since fuel rates are high and emissions regulation is set to come into effect soon [1] you'll likely see waves of shipbuilders adopt fuel-saving technology. A few problems that might show up with this type of prop/"screw" on a large ship: - Ship propulsion uses a fairly large-diameter prop and runs at very low RPM (~100rpm vs 1000-6000rpm) compared to smaller planing vessels. The Sharrow prop advertises decreased cavitation at high speeds but this effect may be diminished at low RPM. That said, cavitation is a different beast for ships than for recreational boats: In the recreational market few boat owners are concerned about propeller efficiency loss due to cavitation -- Concern is mostly around noise and vibration. In contrast, ships are very concerned with fuel and maintenance cost, so if the Sharrow blade successfully reduces both of these it may be helpful. - Seems like they're currently machining these on a 5-axis CNC out of blocks of raw material which won't scale to larger sizes. The complicated shape may not lend itself as well to casting, and even if they casted the shape it would need to be finished and this would require expensive equipment. - Might be more difficult for third-party repair [2] which is done manually or with 3-axis machines. Generally the commercial maritime market is much slower to adopt new technology than recreational, and also much smaller by volume, so it may make sense for Sharrow to continue serving small outboard boats because margins + sale volume is much higher. [1]: Incoming maritime emissions regulations: https://hbr.org/2022/10/climate-regulations-are-about-to-disrupt-global-shipping https://hbr.org/2022/10/climate-regulations-are-about-to-dis... [2]: Example of ship propeller repair: https://www.youtube.com/watch?v=RuV3AsKTQlM https://www.youtube.com/watch?v=RuV3AsKTQlM
- robbomacrae 4y agoCan the same design be used for a small windmill? Will it show similar efficiency gains?
- willnonya 4y agoI would suspect not given the differences in how they operate. I think nit would have additional disadvantages on large turbines where the cost and weight would increase significantly.
- HybridCurve 4y agoLoopwing turbines have been around for over a decade.
- ri0t 4y agoHere, have some pics, if you wondered, too: https://duckduckgo.com/?q=loopwing+windmill&iax=images&ia=images https://duckduckgo.com/?q=loopwing+windmill&iax=images&ia=im... ("Aaaah, those ones! Yeah, sure!")
- jpgvm 4y agoIt would be really interesting to see what his attempts with aircraft amounted to. Propeller tip induced turbulence is a non-trivial portion of what makes general aviation (GA) very loud. If we could make the aircraft less loud without significantly reducing their performance perhaps GA would be more amenable (along with other changes like moving eventually to electric power plants). As it stands right now the general public isn't much of a fan of GA and there is always strong push-back to creation of GA airfields which I think is a shame. The joy of flying shouldn't be limited to commercial pilots and yet increasingly here in Australia that is the way it is. Things are very different in the US because their GA culture is older, more powerful and protected by the FAA and pilots associations.
- ericpauley 4y agoAnother factor is that lots of small GA airplanes are direct drive, and so need to run at high RPM at takeoff to produce full climb power. Geared powerplants like Rotax can reduce the overall tip speed here, and constant speed props can help to some extent. Turbine props need to be geared and tend to run lower tip speeds, so small GA is actually having an outsized negative impact here.
- jacquesm 4y agoSlower props are usually larger diameter though aren't they? That to a large extent would offset the tipspeed gains by using a lower RPM. Or do they run slower props at a steeper root angle (more 'bite')?
- ericpauley 4y agoGreat question! Turboprops spin way slower so even though they’re larger the resulting tip speed is slower. E.g., turbo prop (source https://www.quora.com/How-fast-is-the-tip-of-a-turboprop-blade-going-during-takeoff https://www.quora.com/How-fast-is-the-tip-of-a-turboprop-bla...) I double checked this math and got 474mph. Meanwhile a Piper Arrow (4-seater piston, pretty comparable numbers to most Lycoming/Continental singles) takes off at 2700 rpm and has a 74” propeller, for a tip speed of 594mph. You can use a 3-blade propeller to reduce the diameter and cut noise somewhat (among other benefits). Both of these are just the tip speed relative to the plane, I suppose you’d need to factor the airspeed too and use Pythagorean theorem but I’m no aerospace engineer. As you noted, this is possible because the constant-speed prop on the turboprop allows it to take larger bites of air. The Arrow needs that rpm to produce full takeoff power. However after takeoff it can be adjusted to a lower speed with minimal loss in power (e.g., 2500 rpm greatly reduces noise while losing 7-8% power). To reduce RPM like that in a fixed pitch you’d also need to reduce manifold pressure, causing more power loss.
- csours 4y agoIt does look really cool, but there ain't no such thing as a free lunch. More surface area means more drag. More complex shape means higher price for the prop and poor reparability. That doesn't mean it's bad, or that it won't work. It very well may have use cases that are not served by simpler propellers, and where the price is not a obstacle. For instance, I wonder about very large ships where a little bit of efficiency may pay off the purchase price.
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- alex_duf 4y agoI guess if there's more drag but the water is more efficiently propelled towards the back it might still be worth it?
- flybrand 4y agoI’m planning how to trial a smaller version on our EFoils in the spring. For battery power, that bump is huge.
- ri0t 4y agoWhich is exactly what i'm looking at, too. F** any noise improvements. With the smol angry-pixie-driven (very quiet!) harbour pusher, i'm just looking at ways to not use up too many angry pixies. This one looks promising and can be 3D printed. Original props for that one come in plastic only, anyway, which is really good! Might've accidentally killed my rudder this year, otherwise.
- kellyharsh 4y ago[flagged]
- kristiandupont 4y agoI wonder if this design would be applicable in turbines as well?
- simne 4y agoMost probably, no. - Turbine wheels noise is usually shielded by enclosure, and exists other powerful sources of noise, for example, intake. Yes, much noise of heli create intake air.
- kemitchell 4y agoReduced cavitation? Submarines?
- janalsncm 4y agoThe article says he moved from drones to boats. I wonder why. I’m very interested in drone propellers that could be quieter.
- nokeya 4y agoCould it be applied to PC fans? To reduce their noise
- knolan 4y agoCertainly but as I’ve learned the economics aren’t there. In a previous role we developed a novel heatsink and fan design and saw some licensing interest. We learned that all that matters for thermal management solutions was cost above all else. Existing designs were good enough.
- moffkalast 4y agoIdk, Noctua's clearly making bank off premium ultra quiet fans. At least from me.
- ri0t 4y agoYou're way not alone. Love those ugly-brown quiet-machines. Still, they're probably looking at this and think "Nah, our optimizations are way cheaper to manufacture and wholly sufficient" (because they are :)
- lsaferite 4y agoIs the fan shroud not mostly solving or mitigating the tip vortex issue on something like a computer fan?
- alex_duf 4y agoI'd love to know a real world figure on improved efficiency on cargo ships. If a "simple" innovation like that can move the needle juste by a few percent points on how much fuel we put into the transport industry, that's a very sizeable gain from a climate perspective.
- sigmoid10 4y agoNot really. The whole shipping industry accounts for 90% of the world's transportation of goods, but only 3% of greenhouse gas emissions. The problem with big ships is that they burn crude oil and create insane amounts of NOx and Sulphur pollution. Propellers won't solve that issue, only international regulations can. The industry also grows by several percent each year, so the best thing a small improvement like this could do is counter a few years of growth at best.
- alex_duf 4y agoThanks for pointing out it's only 3%. It's much less than I had pictured! (I also went to look it up after your comment). Let's imagine 3% of improved efficiency (they announce between 9 and 15%, but let's be conservative) on the 3% of the world's emission, that's still almost 0.1% of the world's emission saved by only changing the propellers on cargo ships. It's still a massive improvement: 31 million tons of CO2 saved. At this scale, anything that moves the needle a little bit should be taken. But that's by plucking a number out of thin air, so I'd love to hear about it in the real world and at scale. Regarding the rest of your message, I agree that the type of fuel that is burned is a big problem, but if changing a propeller means burning x% less of it, it's a no brainer to me!
- Gasp0de 4y agoSo 0.3% of the worlds greenhouse gas emmissions by JUST replacing a few propellers doesn't seem significant to you? Can you name another measure that would reduce emmissions in a similar scale with a comparably low effort?
- DoingIsLearning 4y ago
- operr 4y ago[1] Similar concept for Small Unmanned Aircraft Systems by Lincoln Lab [1] - https://www.ll.mit.edu/sites/default/files/other/doc/2022-09/TVO_Technology_Highlight_41_Toroidal_Propeller.pdf https://www.ll.mit.edu/sites/default/files/other/doc/2022-09...
- ubj 4y agoIt's interesting how similar this design is to a UAV propeller design that was created by MIT Lincoln Laboratory [1]. Not claiming that anything nefarious happened--it's just interesting how people often unknowingly converge on the same design. (For the record, it looks like the MIT LL patent was filed in 2017 [2]--not sure how that compares with the patents in the article.) [1]: https://news.mit.edu/2022/lincoln-laboratory-inventions-win-rd-100-awards-0921 https://news.mit.edu/2022/lincoln-laboratory-inventions-win-... [2]: https://patents.google.com/patent/US20190135410A1/en https://patents.google.com/patent/US20190135410A1/en
- flybrand 4y agoQuiet could be a big driver. I advised a drone co w a contract to inspect off shore turbines and they did testing to show how quiet their product was so as not to disturb marine mammals. Also, we’ve been eFoiling a lot and it is so calm compared to being on the water in an ICE propelled craft!
- swrobel 4y agoHere’s an efoil builders discussion of this very prop design https://foil.zone/t/prop-design-share/5849/173 https://foil.zone/t/prop-design-share/5849/173
- Cthulhu_ 4y agoI wonder if the company in the article decided to focus on marine propellers because they could secure a patent specifically for marine use.
- lyind 4y agoWhy isn't this shape used on submarines already?
- VLM 4y agoOn a small ski boat when something like weeds tangles or fouls the prop just pull the lever and tilt the engine out of the water and untangle by hand, including turning the engine on and off its likely a five minute job. Much harder with a submarine in the middle of the ocean.
- simne 4y agoWe don't really know, what used on military submarines, because real photos of their props are top secret. On civ subs, as I know, main driver of choose is just cost, so usually they use conventional cheap designs.
- pge 4y agoThirty years ago, I worked for the Navy and had some exposure to propeller design for submarines. Military propellers at that time were already employing complex shapes for efficiency (and noise reduction). While it certainly takes time for military technologies (especially classified ones, which propeller shapes were) to propagate into the civilian world, in this case, I think the issue is primarily cost. Civilian props have remained quite simple because the cost of manufacturing complex shapes is high (often requiring multi-axis milling machines). In addition, repairability and other concerns may be more important than efficiency. While I don't work in fluid dynamics anymore, it's cool to see people explore some of these ideas in the civilian world. Unfortunately, they may be solving the wrong problem for the vast majority of their users, for whom the cost doesn't justify any performance benefit.
- michaelcampbell 4y ago> for whom the cost doesn't justify any performance benefit. These are boat owners, remember.
- kibwen 4y agoGiven what we're learning about the effect of propeller noise on marine life, I can foresee certain countries outlawing the sale of noisy propellers if reduced-noise versions become broadly available, even if they are more expensive.
- rexreed 4y agoWhen I saw the word "cavitation", submarines was the first thing I thought about. Blame the Hunt for Red October for that word association. You'd think that this approach to propeller design would be adopted due to quieter running, but sounds like not.
- pge 4y agoCavitation isn't just a noise problem; it also causes damage to the blades. The forces on the blade are surprisingly strong. When a propeller has been experiencing cavitation, you can see the pitting on it, almost like you hit it with a pointy hammer. If it continues, cavitation can seriously weaken the blades.
- Neil44 4y agoFans are a big deal. Imagine if you could improve the efficienty of every fan in the world by 5%. Aircon units, air movers, cooling, yadda yadda.
- Cthulhu_ 4y agoNot to burst your bubble, but the technology is there to do so, if not much higher than 5%; it's just a matter of cost at scale.
- Neil44 4y agoYes I sat in on a meeting where one of our customers talked about the big fans in building air movers and how inefficient the cheap pressed metal fans are. But you don't want to spend shit loads of money on a big fancy shaped more efficient one either. New materials and techniquies allow this compromise to be reduced. I'm not in the industry I was just there to turn stuff off and on.
- KingLancelot 4y ago
- mhb 4y agoIn the video showing the cavitation comparison, why aren't the central parts of the propellers more hydrodynamic? Like the typical pointy shape. It seems like it would make the contrast between the two propeller designs at the blade tips more apparent if the predominant source of cavitation wasn't due to the feature they have in common.
- simne 4y agoUnfortunately, not fair comparison "Although we have every confidence in boattest.com’s findings, they were only performed on one boat, and unlike Motor Boat & Yachting’s sea trials, its tests are paid for by the manufacturer". Need big scientific research, with many other participants. For example, it is wide known, that 6-blade prop give near same power as 3-blade but at half rpm, so tip speed is also half. Curious people, could google quiet helicopter, there are few open publications. Overall, same conclusions - more blades, lower rpm, quiet tip techniques, and try to avoid turbulence from one blade by other blade.
- VLM 4y agoSomething that disappoints me about the comments to this story is no mention of engineering optimization. The marketing shows it outperforms at very high power level at very high speed. Then the message veers off into ultra low speed modest power level applications like bulk cargo hauling, and fairly generic greenwashing, we can save the earth with this one nifty techno trick. A better application would seem to be unlimited-class racing boat props or military-industrial complex torpedo propellers. They have infinite money, which makes the situation interesting. There's an old joke that an engineer and an economist see a nickel on the ground and the economist tells the engineer not to bother trying to pick it up because the efficient marketplace theory proves there can't be nickels laying around ready to pick up, therefore it can't be there, must be an illusion. However, in the context of people with large amounts of money willing to pay anything for higher performance, it seems odd that a mere propeller shape could exist that nobody is already paying for, that nobody has been paying for over the last century. My theory would be there's something about this prop that nobody is talking about. Most boats most of the time are not full throttle. WRT durability I wonder what its cavitation behavior is like.
- michaelcampbell 4y agoWhy was the video of cavitation played backwards?
- simne 4y agoPeople asked, how much power could provide human. "The Gossamer Albatross is a human-powered aircraft built by American aeronautical engineer Dr Paul B MacCready's company AeroVironment. On June 12, 1979, it completed a successful crossing of the English Channel to win the second Kremer prize worth £100,000 (equivalent to £538,000 in 2021)" ... "In still air, the required power was on the order of 300 W (0.40 hp), though even mild turbulence made this figure rise rapidly" https://en.wikipedia.org/wiki/MacCready_Gossamer_Albatross https://en.wikipedia.org/wiki/MacCready_Gossamer_Albatross