Sharrow MX-1: Tipless propeller (2020)(mby.com)
mby.com
Sharrow MX-1: Tipless propeller (2020)
https://www.mby.com/gear/sharrow-mx-1-tipless-propeller-110120
163 comments
In Europe where noise is a bigger issue you often see four blade props on small single engine planes. That, combined with mufflers make a huge difference in overall noise. It costs on the order of 3% of performance.
> In Europe where noise is a bigger issue
I think the noise is also an important issue for CPU cooling fans or electric fans for homes.
Would love to see such propeller made into everyday small fans.
I think the noise is also an important issue for CPU cooling fans or electric fans for homes.
Would love to see such propeller made into everyday small fans.
I'd love to see this tested at the Fan Showdown [1], it's a youtuber who 3d-prints user-submitted fan designs. Or given that the article is from 2020, maybe it was tested already.
[1]: https://youtube.com/@MajorHardware
[1]: https://youtube.com/@MajorHardware
I don't remember a tipless one and I think I've seen them all. There is also a subreddit to post and comment other peoples designs.
amazing YouTube rabbithole.
I don't think this design would help with a CPU cooling fan. There's a reason they went from planes to water, and I think that same reason would apply even more so for a CPU fan.
If you're going to spend the space, simply use a bigger fan at lower RPMs.
Electric fans for homes are a more interesting question. I was going to suggest that a Vorando or Dyson already has a lot of elements of this, and gives more bang for the buck, but I think the two could be combined. A Vornado-style fan really reduces vortex shedding, but probably has some turbulence internally. A modified prop design could reduce that a lot.
If you're going to spend the space, simply use a bigger fan at lower RPMs.
Electric fans for homes are a more interesting question. I was going to suggest that a Vorando or Dyson already has a lot of elements of this, and gives more bang for the buck, but I think the two could be combined. A Vornado-style fan really reduces vortex shedding, but probably has some turbulence internally. A modified prop design could reduce that a lot.
This tech requires a significantly wider propeller assembly - quite the opposite direction that consumer tech is going in for all but the most powerful machines. I suppose that gamers might accept a significantly larger case for quieter cooling, but for general purpose computing I think that larger, fanless heatsinks and smaller, more efficient CPUs are the answer.
I'm not in a European country I'm curious do you know if small aircraft are allowed to use leaded avgas 100LL?
100LL is still allowed, but like the US, there are on-going discussions about bans.
I'm guessing the stresses on the propellers at high rpms typical for planes might be an issue. The issue with plane noise is the tip of the propeller breaking the speed of sound. This is what generates a lot of the noise. Having a lot of mass there might be an issue. The prop might rip itself apart. Rpms in water are a lot lower so, it's less of an issue there.
If you change the angle of the blade, you can have lower rpm.
This increased push is a drawback on a normal propeller because more air it pushed outward (loss). This design could solve both of the problems.
So airplane propellers can have more push and lower rpm.
Some years since I last designed propellers and did run CFD-analysis on them. Could be fun to try it again. This was my last attempt: https://no.m.wikipedia.org/wiki/Sivilingeniør#Utdanning
So airplane propellers can have more push and lower rpm.
Some years since I last designed propellers and did run CFD-analysis on them. Could be fun to try it again. This was my last attempt: https://no.m.wikipedia.org/wiki/Sivilingeniør#Utdanning
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The Thunderscreech had a supersonic propeller.
https://en.m.wikipedia.org/wiki/Republic_XF-84H_Thunderscree...
Unsurprisingly it was noisy.
https://en.m.wikipedia.org/wiki/Republic_XF-84H_Thunderscree...
Unsurprisingly it was noisy.
Another 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.
Overall I don't think the FAA or insurers are keen on increasing the number of high-performance GA aircraft out there. The step licensing between ultralight - light sport - GA - complex aircraft really is designed around "the less power, the less likely you are to get yourself into trouble".
The overall wisdom of this is a little questionable and crass of course, since there are also accidents that perhaps could have been recovered with more power.
The overall wisdom of this is a little questionable and crass of course, since there are also accidents that perhaps could have been recovered with more power.
At least in (my experience of) Europe, the main objection to more powerful engines is the proportionate increase in running costs. The trend lighter, more fuel efficient GA has been entirely driven by cost-per-hour, and longer term maintenance costs.
I used to do a lot of gliding and the most powerful aircraft routinely flown was a Piper Pawnee (175 kW / 235 hp engine, in contrast to say c. 120 kW / 160 hp for a Cessna 172), used as a glider aerotow – and even then most of the time we had [electric] winch launches. The pawnee once memorably broke a cylinder head while on tow out and had a sufficient power reserve to both get the glider to a safe altitude and fly the rest of the circuit without issue. At the rest of the field, all of the GA aircraft were highly fuel optimised and mostly run by "normal people" worried about the cost per hour more than anything else. Even the aerobatic aircraft – CAP 10s – had less powerful engines than that Pawnee. I didn't see a super- or turbocharger, and the only people flying twins at nearby airfields were entirely doing it for the point of [commercial] pilot training.
I used to do a lot of gliding and the most powerful aircraft routinely flown was a Piper Pawnee (175 kW / 235 hp engine, in contrast to say c. 120 kW / 160 hp for a Cessna 172), used as a glider aerotow – and even then most of the time we had [electric] winch launches. The pawnee once memorably broke a cylinder head while on tow out and had a sufficient power reserve to both get the glider to a safe altitude and fly the rest of the circuit without issue. At the rest of the field, all of the GA aircraft were highly fuel optimised and mostly run by "normal people" worried about the cost per hour more than anything else. Even the aerobatic aircraft – CAP 10s – had less powerful engines than that Pawnee. I didn't see a super- or turbocharger, and the only people flying twins at nearby airfields were entirely doing it for the point of [commercial] pilot training.
> I used to do a lot of gliding and the most powerful aircraft routinely flown was a Piper Pawnee (175 kW / 235 hp engine, in contrast to say c. 120 kW / 160 hp for a Cessna 172), used as a glider aerotow – and even then most of the time we had [electric] winch launches.
Yeah I mean that's a good encapsulation of what I'm saying: the working aircraft have more power, but the cheap ones are mopeds in comparison. I guess maybe it is mostly the fuel economy though but it generally seems like moonies and other high-performance aircraft probably have much higher insurance/etc. It's cheap to insure your honda accord, you're not going to get yourself in trouble with 1.8L. The FAA is probably happier too.
Diesel could reduce the costs a lot, the DA42 (twin) burns 8 gal/hr, around the same as a C-172, and loiters at 3.2 GPH. Runs on Jet A too (diesel can run on kerosene). I generally think having more modern more advanced aircraft in general could help, the GA fleet is obsolescent and there's no money to replace anything, it's just 70s era engine designs and airframes because that's when the world stopped turning (apart from like, aviation schools and military).
Yeah I mean that's a good encapsulation of what I'm saying: the working aircraft have more power, but the cheap ones are mopeds in comparison. I guess maybe it is mostly the fuel economy though but it generally seems like moonies and other high-performance aircraft probably have much higher insurance/etc. It's cheap to insure your honda accord, you're not going to get yourself in trouble with 1.8L. The FAA is probably happier too.
Diesel could reduce the costs a lot, the DA42 (twin) burns 8 gal/hr, around the same as a C-172, and loiters at 3.2 GPH. Runs on Jet A too (diesel can run on kerosene). I generally think having more modern more advanced aircraft in general could help, the GA fleet is obsolescent and there's no money to replace anything, it's just 70s era engine designs and airframes because that's when the world stopped turning (apart from like, aviation schools and military).
I remember dealing with aerotow, and there was definitely a feeling that Yak-12 that we had (with 260hp) was much better towing than 100-odd hp Morane Rallye.
GA to complex (and high-performance, they're technically separate) is actually a pretty small leap; you just need a flight instructor to sign off that you've done the needful; there's no actual FAA exam. It's hard to find a high performance that isn't complex and vice versa, of course.
Moving to a twin is a separate exam.
A big part of all those is the price of running the bigger plane/larger engine.
You could have a plane with constant-speed prop and fixed landing gear and it wouldn't be complex (unless it was a seaplane).
Moving to a twin is a separate exam.
A big part of all those is the price of running the bigger plane/larger engine.
You could have a plane with constant-speed prop and fixed landing gear and it wouldn't be complex (unless it was a seaplane).
Slower 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')?
Great 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-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.
E.g., turbo prop (source 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.
The Arrow also has a constant speed prop, the difference is the Arrow is direct drive from a massive 360 cubic inch engine whereas the turboprop has a gear box. It needs this displacement to produce power while at such a low speed for the prop. At almost 6 liters, yet producing only 200hp, it's wildly fuel inefficient, and it's fairly trivial to produce this much power with a modern ~2L engine. This is almost entirely due to a single bad engine design that had resonance issues from several decades ago so the industry (stupidly) considers anything but direct drive to be taboo. This is changing slowly with some newer light sport engines that have gearboxes, however.
If it had even a modest reduction drive, you could run the engine at a reasonable power setting while maintaining a more efficient tip speed but the prop and engine engineers had to meet in the middle resulting in a highly compromised solution.
If it had even a modest reduction drive, you could run the engine at a reasonable power setting while maintaining a more efficient tip speed but the prop and engine engineers had to meet in the middle resulting in a highly compromised solution.
The IO-360 is actually a fairly efficient engine when run properly. Similar to Ford’s ecoboost line per https://en.m.wikipedia.org/wiki/Brake-specific_fuel_consumpt... (The -720 is basically equivalent design to a -360 just doubled). Airplanes use a lot of fuel because air resistance varies with v^2, not because of poor engine design.
Sure there have been improvements in modern engines, but these primarily target efficiency across power outputs whereas (as sibling noted) planes tend to have stable power requirements.
Not sure what your point is about constant speed or gearing because I already said that.
Sure there have been improvements in modern engines, but these primarily target efficiency across power outputs whereas (as sibling noted) planes tend to have stable power requirements.
Not sure what your point is about constant speed or gearing because I already said that.
> At almost 6 liters, yet producing only 200hp, it's wildly fuel inefficient
Is it? I've always thought that while GA engines are in many ways stuck in the 1940'ies, they are actually quite efficient. Wikipedia seems to back that up at https://en.wikipedia.org/wiki/Brake-specific_fuel_consumptio... , with a couple of Lycoming engines producing BSFC numbers in the same ballpark as a modern car engine or Rotax.
Is it? I've always thought that while GA engines are in many ways stuck in the 1940'ies, they are actually quite efficient. Wikipedia seems to back that up at https://en.wikipedia.org/wiki/Brake-specific_fuel_consumptio... , with a couple of Lycoming engines producing BSFC numbers in the same ballpark as a modern car engine or Rotax.
Yeah, the thing people always miss is that these engines are flat-rated at whatever hp. I.e., they'll do it for most of their operating lives, vs. the occasional WOT in a car.
Right...it's 200 BHP @ 2700 RPM, which is way below the RPM range you would measure peak horsepower in a car.
Edit: A dyno graph from an late 1990's Corvette C5 engine (5.7L) shows about 170HP @ 2700 RPM. That's at the wheels, so probably close-ish to 195HP at the crank: https://cimg5.ibsrv.net/gimg/www.corvetteforum.com-vbulletin...
Edit: A dyno graph from an late 1990's Corvette C5 engine (5.7L) shows about 170HP @ 2700 RPM. That's at the wheels, so probably close-ish to 195HP at the crank: https://cimg5.ibsrv.net/gimg/www.corvetteforum.com-vbulletin...
Exactly this. Lycoming engineers weren’t stupid, and airplane engines are well-designed within the (admittedly potentially contrived) direct drive constraint.
Hello, Tu-95
Part of the issue is that a lot of propellers in GA are, well, simple.
We do have better designs available, but very fast you end up with either very complex manufacture (and thus price) for special aeroelastic propeller, somewhat less expensive automatically adjustable props, better engines (hello recertification! the big cost killer and what made G100UL so important). I do not know if scimitar prop blades require adjustable mechanism, but wouldn't surprise me. And then there's how to fit scimitar blade on some airplanes.
So unfortunately non-trivial even when everyone involved is all for change, because change costs a lot.
We do have better designs available, but very fast you end up with either very complex manufacture (and thus price) for special aeroelastic propeller, somewhat less expensive automatically adjustable props, better engines (hello recertification! the big cost killer and what made G100UL so important). I do not know if scimitar prop blades require adjustable mechanism, but wouldn't surprise me. And then there's how to fit scimitar blade on some airplanes.
So unfortunately non-trivial even when everyone involved is all for change, because change costs a lot.
This propeller push the water/air inward again, so I guess it would most logical to place it in the back of an airplane?
Or move it to the back of the wing.
Or move it to the back of the wing.
Thirty 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.
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.
Given 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.
When 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.
Cavitation 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.
I'd wager to say that on most civilian vessels, the engine noise is far louder than what the prop could generate. I'm happily using a 600W outboard electrical - while it would be different than with a combustion engine, i don't think it can get much quieter even with better prop-design. It's a blessing! Almost like sailing the boat, i.e. not much louder than a gust of wind.
Energy efficience on the other hand.. It is driven by a fairly average car battery, so every little Watt saved helps keep the drinks cooled.
Energy efficience on the other hand.. It is driven by a fairly average car battery, so every little Watt saved helps keep the drinks cooled.
600W? Is that a typo? That’s less than 1HP.
Probably not. Even large, 40'+ boats designed to operate primarily by sail can get by with 10-20HP. Motorsailers -- racing sailboats designed to go faster by leveraging both the wind and a motor -- typically aren't much more than 40HP.
What's interesting about this prop (to me, anyway) is that most of the sea-faring boats that need it the most will likely not use it because it doesn't feather or fold-away when not in use. For ocean-faring sailboats, that's critical, as the drag of trad props will cap their speeds by half a knot or so, which (over the span of a multi-week journey) might add meaningful amounts of time to a trip that you're just hoping to finish with.
What's interesting about this prop (to me, anyway) is that most of the sea-faring boats that need it the most will likely not use it because it doesn't feather or fold-away when not in use. For ocean-faring sailboats, that's critical, as the drag of trad props will cap their speeds by half a knot or so, which (over the span of a multi-week journey) might add meaningful amounts of time to a trip that you're just hoping to finish with.
I don't know anything about boats, but some boats can be rowed by a single person, which I guess would typically be much less than 600w. It fits with the car battery part too.
Most people are capable to do about 500-800W for long time (30 minutes or more), and up to few kilowatts for short time, 1-3 minutes.
Source? In cycling those numbers are elite level if not beyond. Numbers for rowing are hard to come by but lower[1], probably drag lowering efficiency (bicycle drivetrains are 90+% efficient).
To put it into perspective, 250Wh translates to 800~900 calories burned in a half hour[2]. That's not something most people around me can do.
[1] https://rowinglevel.com/rowing-times/10000m-times
250Wh = 900kJ = 215 kcal at 100% efficiency; humans are ~25% efficient at turning food into mechanical work so ~860 with error bars
To put it into perspective, 250Wh translates to 800~900 calories burned in a half hour[2]. That's not something most people around me can do.
[1] https://rowinglevel.com/rowing-times/10000m-times
250Wh = 900kJ = 215 kcal at 100% efficiency; humans are ~25% efficient at turning food into mechanical work so ~860 with error bars
Yeah, they are wrong.
Also see “How Much Electricity Can a Human Generate?” https://www.pedalpc.com/blog/how-much-electricity-can-human-....
During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that—1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency. An adult of good fitness is more likely to average between 50 and 150 watts for an hour of vigorous exercise.[clarification needed] Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of power.
Also see “How Much Electricity Can a Human Generate?” https://www.pedalpc.com/blog/how-much-electricity-can-human-....
I guesstimate my 100k cycle place to be about 80w so that tracks. At the end I'm about ready to devour anything and everything that's put in front of me.
"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
Kilowatt is ~ 1.3 hp, so 600W = 0.8HP.
But, here important, that electric engines have much better torque on low rpm, even exist electric engines which give high torque just from zero. Also it is typical, to overdrive electric engines for short time.
And other important thing, aging - electric engines could nearly not have aging at all, but gas engines have significant drop of power/torque at hundreds of hours of work, even if properly serviced.
Overall, You will really not see gas engine claimed power, but something much less, ~ 70-90% in good cases. But in case of electric engine, it will not only give claimed power, but could make up to 100% boost for limited time.
But, here important, that electric engines have much better torque on low rpm, even exist electric engines which give high torque just from zero. Also it is typical, to overdrive electric engines for short time.
And other important thing, aging - electric engines could nearly not have aging at all, but gas engines have significant drop of power/torque at hundreds of hours of work, even if properly serviced.
Overall, You will really not see gas engine claimed power, but something much less, ~ 70-90% in good cases. But in case of electric engine, it will not only give claimed power, but could make up to 100% boost for limited time.
I don't know much about marine motors but, unlike for ground vehicles, I don't think that having a ton of starting torque helps in a marine environment. The torque required probably increases as the propeller speed increases which matches traditional ICE engines much better than DC motors.
UNLIKE for ground vehicles, marine and air.
- From tutorial for auto engineers: "more than 90% of time, auto engine working at fast switching conditions, and extremely low load, near zero", vs marine (and air), where prop does near linear load-rpm function at working diapason.
- From tutorial for auto engineers: "more than 90% of time, auto engine working at fast switching conditions, and extremely low load, near zero", vs marine (and air), where prop does near linear load-rpm function at working diapason.
BTW, because autos special requirements, there widely used turbo-compressors, but they are rarely used in marine motors and not too distributed in air.
This is because, turbine only eat power and does not give anything at low rpms, only effective on medium-high diapason.
For planes, turbine only gives an increase at significantly high altitudes, so, for example, typical light plane does not got improvement if flight on typical 1000-2000m, but got if go much higher, 5000m and more.
This is because, turbine only eat power and does not give anything at low rpms, only effective on medium-high diapason.
For planes, turbine only gives an increase at significantly high altitudes, so, for example, typical light plane does not got improvement if flight on typical 1000-2000m, but got if go much higher, 5000m and more.
What is "diapason"? I looked it up and the closest definition was "a burst of sound", the rest pertained to pipe organs.
> for whom the cost doesn't justify any performance benefit.
These are boat owners, remember.
These are boat owners, remember.
F...
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).
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).
There 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
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
Wow These look like fish dicers. Not to say that propellers don’t already dice fish, these just look the part too.
For 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.
A century ago engineer Luigi Stipa did experiments with several flying wing aircraft designs. Here is Stipa-Caproni's "intubed propeller" from the 1930s:
https://en.wikipedia.org/wiki/Stipa-Caproni
Even newer patents should cite this research:
https://en.wikipedia.org/wiki/Luigi_Stipa
https://en.wikipedia.org/wiki/Stipa-Caproni
Even newer patents should cite this research:
https://en.wikipedia.org/wiki/Luigi_Stipa
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This has already been done, for instance: https://www.reddit.com/r/WeirdWings/comments/6wch9q/narushev...
Ok so there is an entire subreddit dedicated to weird wings. I’m not surprised anymore but I’m still amazed at how online communities can be so specific.
This issue is an unending source of discussion. The thing is, you cannot eliminate wingtip or wake vortices by putting a finite barrier at the wing tip, no matter how large. This is because [begin hand-waving approximation] for a wing to produce lift, it is necessary for the airflow passing in close proximity to the wing to be deflected downwards (no acceleration, no force.) This unavoidably creates a region of shear at the boundary between this wake and the surrounding air mass, leading it to 'roll up' into two counter-rotating vortices (as this is a hand-waving approximation, I won't mention the circulation around the transverse axis of the wing...)
We can't banish them, but you can do things to reduce them, the simplest of which is to move the tips further apart (i.e. lengthen the wings.) Everything about airplane design is a compromise, however.
We can't banish them, but you can do things to reduce them, the simplest of which is to move the tips further apart (i.e. lengthen the wings.) Everything about airplane design is a compromise, however.
Good ideas are a dime a dozen. What's rare and precious is the very hard work of birthing an idea into existence with good execution. Unfortunately, even with a good idea, hard work, and excellent execution, innovation still usually ends in failure.
Yeah, I can say with some certainty that every aerospace engineer has this idea at some point then moves on to other things. A select few have pursued it but at least at aircraft scale it results in a number of other engineering challenges related to structures and resonance so it's usually abandoned. The brilliance here is applying it to an area where the aspect ratios are so low that the mechanical issues don't apply and you can just cast it out of a big chunk of solid metal.
It'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-...
[2]: https://patents.google.com/patent/US20190135410A1/en
(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-...
[2]: https://patents.google.com/patent/US20190135410A1/en
Quiet 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!
Also, we’ve been eFoiling a lot and it is so calm compared to being on the water in an ICE propelled craft!
Here’s an efoil builders discussion of this very prop design https://foil.zone/t/prop-design-share/5849/173
I wonder if the company in the article decided to focus on marine propellers because they could secure a patent specifically for marine use.
So 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.
I wouldn't buy one for a pleasure craft, but even a small efficiency gain in ocean freight could turn the industry on its head.
Maybe 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.
Large container ships already use variable pitch props.
Didn'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
I'm just waiting for someone to make an RC scale injection moulded plastic version of it :P
I'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?
Yes, ABS is supposedly strong enough for that.
I wonder if we'll see a 3d printable version soon.
I'm thinking of putting it on the Mini 2 and seeing what happens.
I'm thinking of putting it on the Mini 2 and seeing what happens.
Probably not without violating a patent.
I'm kinda sure that if he is not going to sell it they really don't care.
If you went around looking for patent and copyright violations on thingiverse you'd probably need to remove most of what they've got.
Yes, You are absolutely right. Anybody could try any shape for scientific experiments, but sell copies and distribution of 3d models prohibited.
I wondered if this design is heavier for same lift? Might be part of the reason for moving development to boat propellers
Edit, to clarify: i refer here to 3D printed boat props, not for copters.
I'm considering this as well. I have an electrical outboard engine on my 24". 600W is way less stressing on the material than even small combustion engines.
I'll maybe try a 3D printed one next year. According to thingiverse, folks already successfully use printed props and the sharrow-design is there, as well, just need to adapt the mount and make sure the printer is up to it (i.e. convert from PLA to ABS, may have to get a new nozzle)
I'm considering this as well. I have an electrical outboard engine on my 24". 600W is way less stressing on the material than even small combustion engines.
I'll maybe try a 3D printed one next year. According to thingiverse, folks already successfully use printed props and the sharrow-design is there, as well, just need to adapt the mount and make sure the printer is up to it (i.e. convert from PLA to ABS, may have to get a new nozzle)
People in Ukraine print small props. But conventional design. For small electric engines good enough.
"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.
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.
Small 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.
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.
However engines are roughly linear in displacement vs power output. A 15% increase in thrust would mean you can reduce the displacement of the engine by 15% and maintain the same speed. This would be compounded by the weight savings, smaller fuel tank, etc.
However, I think there is a far less than 15% increase in thrust, and due to the super-linear loss of efficiency at the top end to get a 15% increase in efficiency for the same output level might only require a 3% or so increase in thrust at that output level.
However, I think there is a far less than 15% increase in thrust, and due to the super-linear loss of efficiency at the top end to get a 15% increase in efficiency for the same output level might only require a 3% or so increase in thrust at that output level.
No, it claims 9 to 15% efficiency gains. A more efficient machine, with all else being equal, is more powerful at that same engine condition.
Efficieny gains of boat propulsion translates into mileage gains... unless boats work in some non-linear manner?
Imagine 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.
Okay, and?
That was two years ago. I’m wondering what’s happened, since…
Anecdotally (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/), a fairly crazy gyroscopic stabilization system, wildly popular but fairly quiet in the tech world.
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/), a fairly crazy gyroscopic stabilization system, wildly popular but fairly quiet in the tech world.
Would you have knowledge of how well that would scale on a cargo ship and what sort of savings we could see there?
Unsure 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-dis... [2]: Example of ship propeller repair: https://www.youtube.com/watch?v=RuV3AsKTQlM
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-dis... [2]: Example of ship propeller repair: https://www.youtube.com/watch?v=RuV3AsKTQlM
For the most part, very little.
They have recently entered into an agreement with Yamaha outboards[1] to have Yamaha manufacture Sharrow propellers.
So far though there has not been much in terms of real-world validation of the props on common boats. In some cases there are modest gains seen (<10%), but that is not enough to offset the increased upfront price of the Sharrow. If they could get the manufacturing cost down to that of a typical high performance propeller it might have more demand in the market.
[1]https://boattest.com/article/yamaha-cast-and-sell-sharrow-pr...
So far though there has not been much in terms of real-world validation of the props on common boats. In some cases there are modest gains seen (<10%), but that is not enough to offset the increased upfront price of the Sharrow. If they could get the manufacturing cost down to that of a typical high performance propeller it might have more demand in the market.
[1]https://boattest.com/article/yamaha-cast-and-sell-sharrow-pr...
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.
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.
Welp, as someone else here pointed out, just print it, then:
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.
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.
Something 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.
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.
I'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.
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.
Not 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.
Thanks 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!
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!
So 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?
Commercial and residencial buildings setting their heating to 19 celsius or their cooling to 23.0 Celsius.
Haven't checked the maths but energy use in buildings is a far bigger chunk of emissions than shipping.
Haven't checked the maths but energy use in buildings is a far bigger chunk of emissions than shipping.
Do people really set their home thermostats to over 19 degrees? We set ours to 18 and often find that we're getting too warm
A lot of commercial buildings are set above 21 celsius.
This is currently done in Germany (and possibly much of Europe).
It would actually have the opposite effect. More efficiency means lower cost, which leads to higher utilisation
With large shipping, there isn’t a lot of underutilization - and what there is is not there due to fuel cost.
well, the emission of all these pollutants should go down proportionally if you can save some fuel
People 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
"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
I’m planning how to trial a smaller version on our EFoils in the spring. For battery power, that bump is huge.
Which 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.
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.
Fans 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.
Not 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.
Yes 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.
I'm not in the industry I was just there to turn stuff off and on.
[1] Similar concept for Small Unmanned Aircraft Systems by Lincoln Lab
[1] - https://www.ll.mit.edu/sites/default/files/other/doc/2022-09...
[1] - https://www.ll.mit.edu/sites/default/files/other/doc/2022-09...
Could it be applied to PC fans? To reduce their noise
Certainly 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.
Idk, Noctua's clearly making bank off premium ultra quiet fans. At least from me.
You'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 :)
Is the fan shroud not mostly solving or mitigating the tip vortex issue on something like a computer fan?
Unfortunately, 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.
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.
In 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.
The article says he moved from drones to boats. I wonder why. I’m very interested in drone propellers that could be quieter.
Can the same design be used for a small windmill? Will it show similar efficiency gains?
Loopwing turbines have been around for over a decade.
Here, have some pics, if you wondered, too: https://duckduckgo.com/?q=loopwing+windmill&iax=images&ia=im...
("Aaaah, those ones! Yeah, sure!")
("Aaaah, those ones! Yeah, sure!")
I 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.
It 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.
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.
[deleted]
I guess if there's more drag but the water is more efficiently propelled towards the back it might still be worth it?
[deleted]
Reduced cavitation? Submarines?
I wonder if this design would be applicable in turbines as well?
Most 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.
- 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.
Why was the video of cavitation played backwards?
Why isn't this shape used on submarines already?
On 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.
We 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.
On civ subs, as I know, main driver of choose is just cost, so usually they use conventional cheap designs.
Run 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.
That price was for essentially CNC milled prototypes, I imagine if they cast them they would be a fraction of that price.
They could offer very customized versions made in an Inconel 3d printer.. Wonder if that (economically & technologically - is inconel seawater safe??) really makes sense, though.
You can use direct metal laser sintering on most powered steels, no need to use Inconel. The reason it's often used with Inconel are the parts you want to make from Inconel are difficult shapes to cast and milling Inconel sucks, eats tools for breakfast.
casting 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.
I wonder myself if it's small enough to use a laser-sintering print process to build.
Sacrificial sand moulding is done all the time and is pretty cheap:
https://youtu.be/lnHhP_kZ43k
https://youtu.be/lnHhP_kZ43k
If 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.
Even 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.
Binder-jet printing of sand cores is pretty cool too.
Why would you cast it at all, when it's a perfect shape for forging the blades and then welding or brazing them (depending on the material) to a central hub?
4300 is within the sales price range of exotic propellers, anyway.
a feathering/folding prop for a 35 foot sail boat is about 3 grand already, and it's certainly not a single piece of billet. The real exotic race-y stuff for that size boat is ~6 grand.
Yes, it sucks to ruin a prop -- but it's almost certainly user error 90% of the time; either sucking in boat lines (which will lead to a stall and engine mount damage/ prop-shaft damage in a majority of cases, not prop damage.), or running aground.
a feathering/folding prop for a 35 foot sail boat is about 3 grand already, and it's certainly not a single piece of billet. The real exotic race-y stuff for that size boat is ~6 grand.
Yes, it sucks to ruin a prop -- but it's almost certainly user error 90% of the time; either sucking in boat lines (which will lead to a stall and engine mount damage/ prop-shaft damage in a majority of cases, not prop damage.), or running aground.
Uh, plastic props for my harbour-pusher come in at lousy 45 bucks. Sometimes, i'm so happy to own a smol boat.
Hah. Jokes on you! I'll gladly try using a 3D printed version of this on my 600W angry-pixie-harbour-pusher - which they only sell overpriced plastic props for, anyway ;D
Btw.: Worst thing: ride backwards and you'll have to tighten the mounting screw or risk loss of prop. Best thing: Rudder survived hard prop contact with just a few scratches on the outer coat \o/
Btw.: Worst thing: ride backwards and you'll have to tighten the mounting screw or risk loss of prop. Best thing: Rudder survived hard prop contact with just a few scratches on the outer coat \o/
I look forward to seeing your HN post in a month's time about it.
How Hard Can It Be...?
How Hard Can It Be...?
I think it's a pretty cool design but repairability does seem like a concern -- Normally you'd take a stainless prop to a shop and they'd just weld + grind any small damage but that seems more difficult with the geometry of this propeller.
I don't see why it would be, unless you bent the blades really badly.
Things are very different in the US because their GA culture is older, more powerful and protected by the FAA and pilots associations.