Any competitive sailor or foil-racer knows that the underwater surface has the least friction and best laminar flow when sanded with fine-grid sandpaper, around 1000 to 1500 grid.
It always surprised me that this was not true in air and airplane wings were supposedly best when glossy. So now it turns out that this is indeed not true, and airfoils also benefit from micro-roughness for lowest friction.
Now the surprising question to me is how is it possible that something so simple was not known in this very well-researched and well-funded field. It probably was known, just not by the paper-publishing researchers.
The core tenant of the paper is that roughness reduces drag IN the transition zone. A very small region of the total flow.
Thats the region between laminar and turbulent flow. Laminar flow is typically 5x less drag than turbulent, and will be encountered about a Reynolds number of 500K-1M (ratio of inertial flow to viscous flow).
Surfboards will have a Reynolds number of 10^7 which is entirely turbulent.
A Cessna aircraft will have a Reynolds number of 1-5x10^6.
The vertical stabilizing surface of these elements is really insignificant to the entire surface of a board. Combining drag coefficients is done with the wetted surface area.
In truth there's some contamination from the upstream flow. Stabilizing elements are behind the center of pressure, so they will see the most "diry flow"
You are thinking about a slow boat in displacement mode, or a wave-surf board with very small fins.
But I can tell you that the wetted surface area of my wing-foil board is exactly zero after takeoff, and all wet surfaces of the foil are, for a significant percentage, in laminar flow. Same for a windsurf board planing: just the last 50cm of the board is touching the water and the fin is extremely significant for drag.
I have 2 foil drives for wake thieving and a SUP for downwinding and I’m just excited that someone on HN is talking about foiling. Such an underrated sport.
Water is fairly viscous, and when you try to pull through too fast you completely change regime due to cavitation.
In comparison, from my days studying aerodynamics for RC soaring, air has a wider range of "viscosities" (represented by the Reynolds number) depending on the scale of your aeroplane and the speeds you intend to go through the atmosphere. The aerodynamic ideal or what count as useful tricks (winglets, dimples) can be fairly different for a a golf ball compared to a RC airplane compared to a commercial jet compared to a fighter jet...
Asking as a complete neophyte - how does this reconcile with modern war planes being inherently unstable as far they flight dynamics go, without their enormous thrust capabilities? I’m just curious, I know nothing about the subject, but it seems that the solution we came up with is thrust, baby.
Would you a have a link that would show case something like that? It feels like only a T-1000 would be able to make any rapid coherent decisions under such load. Thank you.
Instability just means that they don't naturally return to stable flight. Fighter jets benefit from this because when you want to make a maneuver, you're not fighting the plane's natural inclination to stay where it's pointing. You don't need particularly powerful hardware to do this kind of control, quadcopters are an even more obviously inherently unstable example, because any thrust imbalance will immediately make it roll. Quadcopter control loops only need to run at a few hundred hertz to achieve stability.
That's simple - to make quick rotation, you must apply force (torque) and beat inertia - from mathematics could know, the farther from center of mass the more energy will spend to rotate at same speed.
So, to rotate faster, you need larger control surfaces.
From other side, traditionally, self-stabilize spent at least 1% of energy (on small planes normal up to 10%). What all this mean - with 10 000kg of total weight, your control surface will constantly make 1000kg of force to just fly, but when need to turn, will need significantly more than 1000kg, that's all.
Old planes need self-stabilize, because constant corrections was very time consuming, but modern have powerful computers and could provide artificial stabilization - current 1kg computer could provide same stabilization as control surface constantly making 1000kg of force.
I am curious about humans operating machinery outside of our inherent performance envelopes. Do we have enough runway beyond switching arrow tips from flint to SS?
> It always surprised me that this was not true in air and airplane wings were supposedly best when glossy.
I was an AE major and I don’t recall ever learning that airplane wings were best when perfectly smooth, even as a simplification in undergraduate courses. We were taught that drag is reduced by maintaining an attached laminar flow.
Airplane wings are glossy because they’re metal (or CFRP) and painted for durability and corrosion and UV resistance.
as usual these things are presented as new and revolutionary but aren't actually.
the specific process and implemention however are usually newer or slightly different from before.
this is our sensationalistic based society - any iterative progress, or sometimes even copy, is explained as a revolution.
now show me a 737 using 40% less fuel - guess what - that wont happen - however, perhaps we'll get a slightly better process to create aircraft skins. keep in mind you cant re-sand a fuselage every week, it needs to work reliably with no maintenance.
Yeah I'm pretty sure I remember reading something in a pop science magazine 20 or 30 years ago when MEMS nano structures were all the rage and how they were gonna use mass arrays of them on airplane wings to somehow increase flow
Not uncommon to hear bold claims with every new and emerging technology that isn’t well understood by the media or general public. The excitement over nanobots seems to have run its course (for now?).
Blockchain managed to find its way into every market imaginable.
Battery technologies have consistently delivered bold claims on an almost yearly cycle, but we have at least seen incremental improvements.
AI is obviously the worst offender in the current timeline.
I wonder how quickly airlines will adopt sanded/rough wings. It's also interesting that the efficiency of winglets were known for quite awhile but only somewhat recently have nearly all airliners adopted them.
Also matters a bit what happens to a surface that they don't do anything to. Does a precisely rough surface get too rough or too smooth? Does a precisely smooth surface get rougher in a way that's beneficial?
Could be the case that in-practice this means they just worry less as their perfectly smooth planes get a bit rough.
I remember people could smoke on planes. On some airlines seat backs and bathrooms had cigarette ashtrays in them. Smoking was phased out between 1988 and 2000, with most airlines being smoke free in the mid-1990s.
But the ashtrays persisted well into the 2000s. Two reasons: they needed to refresh the cabins, which is on a longer maintenance cycle done every few years, and before that, they needed replacement seats and bathroom fittings without the ashtrays. That meant tests, regulatory approval, all sorts.
For ashtrays being removed.
Winglets are a similar story. They're an addition, but they needed test flying and type approval before they could be added to the maintenance cycle rotation and get added to aircraft.
This is a bigger change. Boeing and Airbus (and others), are going to need to design it, push it through CFD, build different variants, test fly them, get them through regulatory approval and then... well, existing aircraft are probably not going to get these. Too expensive, too hard.
What's going to make more sense is a new aircraft - even if it's a variant type like the 737-MAX or the A320-Neo or whatever - where they approve the type modification as a whole, but it's not a retrofit to an existing airframe, will help manufactures sell more aircraft, airlines don't need to ground existing fleet and over time the fuel efficiencies get involved.
The FAA still requires ashtrays in bathrooms interestingly. To avoid those who do smoke there using the trash and causing a fire:
Regardless of whether smoking is allowed in any other part of the airplane, lavatories must have self-contained, removable ashtrays located conspicuously on or near the entry side of each lavatory door, except that one ashtray may serve more than one lavatory door if the ashtray can be seen readily from the cabin side of each lavatory served
I don't think it's safe to generalize from this to a functional aspect of the plane. Removing the ashtrays serves no purpose, so there's no cost to letting it wait for a decade or two. Improving the aerodynamics does serve a purpose and might be done faster.
At least one total loss was caused by a waste fire in the lavatory from a cigarette-the ashtrays are mandatory safety equipment and the FAA won’t let you fly without them operable.
Modifications to an approved type design, especially for commercial passenger aircraft, are an intensely bureaucratic and thus very expensive process. This is part of the reason why product cycles are long.
The article contrasts it with a manufacturing process known as “shark skin.” I wonder if it’s entirely identical to the skin of a shark or a marketing term?
Sorry the article is paywalled and I reacted to the comment about sanded surfaces. I remember seeing documentation or other nature documentation’s about the shark skin effect. I had the chance to touch a shark and a ray in an aquarium but never felt the shark skin foil. I assume the properties would be the same though.
You know the carbon footprint concept was literally created by BP marketing, to place the blame for climate change on society, and distract from all the evil stuff they did to promote more fossil fuel consumption and sabotage climate science.
The blame is 100% on society, so BP is correct to place it there. If we wanted to reduce our CO2 output to near zero we could do that easily. But it turns out that we would rather have all of our modern conveniences, so this is 100% our fault. Blaming it on oil companies is like a murderer blaming Smith and Wesson.
You’re sadly making this a simpler issue than it actually is. There are countless industries that have used immoral tactics to make more money. That includes tobacco companies (lying about health benefits & consequences to smoking), gambling companies (misleading people about how much money they can expect to make), and, of course, oil companies (lying about how harmful gas is to the environment).
Using gas is not actually necessary to have all our modern conveniences. In fact, it is fucking stupid to rely on continuous resource extraction, deleting our fuel supply to create energy, when we can get it continuously for free from the environment with a minor up-front investment.
It is not 100% our fault. This is only like blaming it on Smith & Wesson if Smith & Wesson had created “pacifist guns” that allegedly solved societal violence, or if Smith & Wesson spent huge amounts of money trying to convince people that guns are not actually dangerous objects.
> people who believe that crashing the US, including the dollar, enables them to build a US like they want
Yes, it's strange how dumb some rich/succesful people are. As I understand it, no civilization ever has done such a thing. If a civilization and its institutions crash, it remains failed/dysfunctional for a very long time. The only way to improve society is in small steps.
I hope the people who finance this all will wake up to the reality that it may well cost them everything, too.
It's not strange; they can just afford to weed out the people who say "no" from their lives. Everyone around them is either in the same situation, or depends on them for their cushy livelihood.
Not having to hear "no" for decades breaks brains.
Titanium's advantage is imo not so much its weight, as aluminium is better still in that respect. Titanium is mostly better where corrosion and temperature resistance are important. Relative to weight, high grade steel, titanium and aluminium are about equal in tensile strength.
There is a good reason: profits and management pay. And greed is good, right?
> the problems are fixable
Fixable in theory. The US would first have to fix the underlying issue, which i.m.o. is government, media and even judicial capture by financial interests. Billionaires are now openly buying "shares" in those. I don't see any sign of it changing anytime soon. It only seems to get worse.
It's not just profits and management. Administrators, nurses, and yes, definitely doctors, get paid far higher in the U.S. than in other countries. Who wants to be the one to say we need to cut staff, and cut wages for nurses and doctors, in order to bring down costs? Just cutting fat from insurance companies, or having the government step in as insurer with no other changes, wouldn't move the needle much.
I'm pretty sure healthcare costs in the US are also higher as a percentage of GDP compared to EU, so higher wages would not explain the difference. Also productivity should be higher?
I think pharmaceutical, hospital, insurance and legal companies take all the money.
Yes there’s tons of overhead and extra costs, but it isn’t mostly at the insurance company level. It’s spread all around the system, that was my point. There’s no one “quick fix” that leaves everyone with the same job and fat salary as they had before.
It's very worrying that consumer protection against poisoning in the US comes from a for-profit company that makes money by short selling companies they found to have issues and then covering their back this way against lawsuits, which any less aggressive reviewer would face.
The investigating is great, the problem is who is doing it and for what reason.
If the misdeed is done by a non-public or poor company there is no money to be made so they would never even investigate it. And not accepting a payoff that returns more than the short position would be ignoring fiduciary responsibility, so some investigations could disappear.
Most Newspapers are profit driven. The only difference is how the profit is derived. It seems to me that the choice is to have this information come to light or not have it all.
With all the anger over illegal immigrants taking US jobs, as a European it surprises me that nobody in the US seems to even mention the idea of punishing the employer for employing illegal workers.
If I want to hire someone (local or remote) as an employer here, I better make sure the worker has a valid working permit. Fines for non-compliance towards the employer are huge, even for a single day of work. All paperwork has to be complete before any work is done. Even when hiring through intermediary companies who guarantee it's all legal, liability and fines remain in place for the ultimate employer if it turns out to be not so.
In the US, there is no reliable way to verify employment eligibility. What systems do exist tend to produce many false positives and false negatives. Furthermore, you are required to accept documents the demonstrate employment eligibility at face value, even if they are likely to be fraudulent.
In industries that famously have many illegal employees, the companies have cover because the employees always have fraudulent documents. And since the company is required to accept those documents and not discriminate, the company can't be held liable for hiring them even though they are illegal.
Underlying this situation is that it is unconstitutional for the Federal government to issue mandatory ids to citizens that could be used to reliably determine employment eligibility.
I'm an employer, and this is the form that needs to be filled out when we hire someone.
Notice the 2nd page of eligible documentation. A "School ID" and "birth certificate" are adequate documentation for employment. Both can be easily forged and difficult to verify.
Also notice the bottom of the 2nd page: it allows (for a temporary period) a "receipt" of the document to be considered acceptable if it is "stolen" - meaning you don't even need to have the physical document at all.
And here's the kicker: This form does not need to be submitted to any government agency. (You literally just fill it out and put it in a filing cabinet)
> A "School ID" and "birth certificate" are adequate documentation for employment
No, they're not. They're adequate to establish identity. (List B).
> form does not need to be submitted to any government agency. (You literally just fill it out and put it in a filing cabinet)
Correct. We're on the same page in respect of employers having no real requirement to verify work authorisation. This appears part of the policy choice that lets certain politicians rail against illegal immigration without threatening the economics they support.
Turning away potentially underage drinkers is encouraged (and not doing so badly punished) but denying someone legal allowable employment is subject to litigation.
"ANTI-DISCRIMINATION NOTICE: All employees can choose which acceptable documentation to present for Form I-9. Employers cannot ask
employees for documentation to verify information in Section 1, or specify which acceptable documentation employees must present for Section 2 or
Supplement B, Reverification and Rehire. Treating employees differently based on their citizenship, immigration status, or national origin may be illegal."[0]
It is against Federal law to reject any reasonable documentation that satisfies the I-9 requirements. Historically, you can bootstrap your way to meeting those requirements with not much more than affidavits and basic forgery.
There are many people who are US citizens that due to history or circumstances have no reliable documentation of such with which to bootstrap an ID -- I have people with no foundational documents in my own family. The system is designed to enable these people to bootstrap their paperwork without a reliable root document, which is of course exploitable by people that are in the US illegally.
State-issued IDs do not contain sufficient information to ensure eligibility for employment under Federal law.
There is already a Federal law that punishes employers who do not accept documents that satisfy the I-9 requirements. Illegal immigrants have documents that satisfy these requirements.
> Illegal immigrants have documents that satisfy these requirements.
This reminds me of a Beavis and Butthead scene: "At the border. -Policeman: let them through. -Other policeman: Why ?. -Policeman: Mexicans know the capital of Texas, Americans don't"
How many times does everyone who knows have to explain that it is illegal NOT to accept the documents. The more the law is enforced, the more such documents must be accepted.
There are conflicting valid problems, different problems that are both valid, but the solution to one inhibits the solution to the other, and the law as it stands favors preventing discrimination as being the higher priority over preventing illegal employment.
I doubt either you or I knows if that is even a wrong priority, because I can't say which is the bigger problem. I'll say I don't begrudge any immigrants getting jobs, whether they are technically illegal or not. They are human and until they actually commit theft or violence I don't get off on making them suffer.
Regardless, the problem is not enforcing the law. The law says you must accept the documents. There is no "diverted blame". If you find the prospect of the wrong person getting a job so outrageous, the "blame" is on the government for making it easy to fabricate their documents. The various documents that the law says you must accept, should not be so easy to fake up, and there should probably be some office that accepts these documents and vets them instead of just telling employers to file them and never looking at them.
The people who complain about illegal immigrant labor in the US also like their cheap chicken and other fruits from illegal immigrant labor.
It's a weird case where one business undercuts another by hiring cheap labor, and then the other business has to do the same thing or else risk going out of business.
Better enforcement might help, but remember, people like cheap chicken; it doesn't matter which way you vote.
People say this, but I always wonder if some rejiggering of the revenue allocation calculus might make it possible to keep chicken cheap while paying the workers a living wage. All you'd have to do is make a handful of executives very disappointed when they open the letter containing their tax bill - or when a federal law enforcement agent knocks on their door.
I think we're more likely to see AI-based automation further take humans out of the loop at chicken factories.
That being said: I personally think it makes more sense to lower the cost of plant-based proteins. It's always going to be cheaper when we eat the plants directly instead of having an animal convert the plant to protein.
For protein. That doesn't account for micronutrients. For better or worse, humans are omnivores. We might be able to live on less meat. (Collectively-speaking; this individual weightlifts and accumulates injuries like crazy if he doesn't eat enough meat, sorry.)
There's also an issue of lower fat/connective tissue content in plant-based meats (again, necessary to support joint and muscle recovery). Also, IIRC, the fats and oils in meat hold up better to high-temperature cooking than the ones in meat analogues. Best I can do is go pescatarian (which has its own issues at-scale).
If it needs fixing in law, let's do that... not this weird system we have now of turning our head the other way and waving it off as necessary while ignoring any criticism of said crazy system.
> it surprises me that nobody in the US seems to even mention the idea of punishing the employer for employing illegal workers.
The anti-immigrant politicians can't punish the employers because they would be punishing their own donors.
If that sounds like a contradiction, consider that undocumented/illegal immigrants are effectively pawns who have no political power in the system, and the contradiction disappears entirely.
How does that make the contradiction disappear? It doesn't.
The resolution to the contradiction is that few candidates to Federal office are opposed to illegal immigration, and those that have opposed illegal immigration have mostly gotten away with merely saying they are opposed while not doing very much to stop illegal immigration.
Because it makes them look like they care for the people who elected them ("the imigrants make crimes/are taking jobs" narative). In reality the politicians only care about the biggest bider.
In some states it is, but state-level elected officials have only weak levers with which to influence the rate of illegal immigration.
I don't know much about the topic, but conservative commentator Ann Coulter complained that although he certain got votes by talking about it, Trump didn't do much against illegal immigration and probably doesn't really want to do much about it.
Because they never actually intend to, in any meaningful way. Trump is the wildcard; he was the first to actually do it, and the result was a lot of people complaining about rising construction costs and a shrinking labor pool. The actual goal for these donors and politicians is to keep a steady influx of exploitable labor to serve as the poorly-compensated, mistreated underclass that most Americans would riot rather than let themselves become; enough so that they always have something to run on, but not so many that they actually have to take action (e.g., when even liberals or progressives start having an issue with it). Same thing with Democrats and abortion.
The "interesting" (in Chinese proverbial terms) part is that we're living in times where a certain charlatan's actions have lead to the big red button actually being pushed on both matters. Whoever wins tonight, it certainly looks like we're about to test if each respective development has any bearing on polls, or if parties can just run on anti-immigration/pro-choice vibes ad nauseum, regardless of what's actually happened wrt each policy over the past (few) decade(s).
> it surprises me that nobody in the US seems to even mention the idea of punishing the employer for employing illegal workers
This has been my proposed solution to the immigration problem in the US. Stop attempting to corral the people coming over, and shift 100% of your resources toward punishing those who employ them. How many people will attempt to sneak into the US when no one is willing to hire them?
I also view this as a "put your money where your mouth is" stance. It changes it from a political issue into one with a practical solution, and the people benefiting from cheap labor would have to be very creative to find fault with it.
> punishing the employer for employing an illegal worker
It's already the law.
This is why employers mandate I-9 forms as part of employment.
This is part of the larger indictment against Christine Chapman by the DoJ, who found she was falsifying employment verification documents and giving access to North Koreans in return for a portion of the embezzled sums.
Stories like this are also why there has been a major push for RTO.
There is practically zero enforcement. Criminalise hiring illegal workers while stepping up enforcement and you dramatically reduce the value of illegal migration while shutting down large sections of the economy, thereby prompting supply-side inflation.
We don’t do it because this is a politically convenient middle ground that keeps illegal labor in the system while segregating it from competing with most of us. (Put another way: we have a regulated and an unregulated labor market. We like the fruits from the latter.)
This is the next key talking point for a winning candidate, and may be the ultimate solution to US immigration. It can and will gain popular support, but it will take someone sneaky enough to gain their party's support on other matters first; either after becoming the party's nominee or after being elected. Either one.
(If you propose this after being elected you might only last one term though; it's a bit of a rug pull. Better to pull the rug out from under your party rather than the voters.)
It's about investment funds and shareholders owning commercial property who push for RTO out of fear of their portfolio going down in value if people are not using the offices.
To be fair I think the only reason the conspiracy even exists is because, apparently, nobody knows what RTO is really about. IMO it's mostly just a power play and insecure executives, but they won't come out and say that of course. We're left to speculate, and naturally conspiracies thrive.
Legislation is frequently proposed to do just this: require all employers to use E-Verify to ensure they don't hire illegal workers. The same people who are constantly firing up voters about immigration are opposed to this. The political issue is valuable to them, as is cheap, cowed, disposable labor. And they know if they succeeded in shipping their workers back over the border there would be economic and political mayhem.
I expect endless demagoguery about immigration and performative cruelty, but nothing that will challenge the bottom line.
The current Republican nominee ran his entire campaign on hating immigrants and has been known to hire illegal immigrants. They don't actually want to crackdown on it they just want to campaign on it.
Legislation is meaningless if it is not going to be enforced or if it will be used to destroy competition. As in law enforcement cannot deal with all cases, but they certainly can be nudged to deal with businesses that corrupt government doesn't want operating.
I don't know that they will. For example, 90% of Trump's previous platform was the wall. That's all he could talk about. No wall to be found, and he doesn't even mention it anymore. Things change from campaign to office.
It’s a playbook as old as time. “At least we’re not <the other guy>”
When slavery was a thing, white southern workers made a lot less than northern workers. Racial superiority pumped the suckers up. Johnny Reb volunteered to be slaughtered so some aristocrat could own people.
Most of the illegal immigrant hoopla has been performative bullshit to make to easier to control employees. If you’re in the chicken processing business or need casual labor, it’s a hell of alot cheaper to avoid paying for social security, worker’s compensation, etc by hiring people whom you can easily exploit by dangling the sword of ICE over their heads.
The US governance model segments immigration and work regulation - the former is a federal matter, the latter is almost exclusively regulated by the states (including enforced of federal rules).
In recent years as conservatives have veered into a more overtly racist and reactionary movement that’s shifted a bit.
Disruption at work. Ford can't make money on selling EV's, their overall margin suffers with every EV they sell. They have large existing investments in factories, processes and people that produce combustion engines. They can't lower prices and sell enough of them for economies of scale to start working.
Tesla is the new Ford. Ford (and most other car manufacturers) will have a difficult time, most manufacturers are probably doomed. After the current hesitation phase, when the economics are there (very soon), customers will almost all go electric.
What investors (and their "agents" CEOs) want is ROI, which depends on not only total profit, but also total amount invested and how long it has to stay invested. Hence the relevance when GP says that "They have large existing investments in factories, processes and people that produce combustion engines".
Margin is profit over total revenue, not profit over Capital invested
When someone buys stock on the market, they are giving money to another trader. They are not giving money to the company to invest in production capacity.
Shareholder profit tracks net corporate profit, not profit margin. It's better to hold a stock that makes a 1% margin on a billion dollars revenue, then one that has a 90% margin on $10 of revenue
>When you buy ford stock, none of that money goes to the company for capital investment
Companies regularly sell their own stock and use it for capital investment. It is an important way that large capital projects are funded in capitalistic countries.
Federal Express is a great example: as a start-up, it could not become profitable till it had a big network (planes, airport landing rights, a huge sorting facility) so the cost of the network had to be paid for by selling stock or by borrowing, and corporations at least in the US raise more money from stock sales than they do from borrowing.
Another example is training AI models: most of the tens of billions of dollars in GPUs and electricity that has been used or will soon be used to train AI models comes from the sale of stock.
You are talking about IPOs and other secondary stock offers.
During secondary stock offers, Investors will care about how much value the addition funds will create relative to cash put in.
Still, this is different than a percent profit margin on sales. Investors care about the total profit, not the percent margin.
going back to the actual situation, EV's lowering the percent profit margin doesnt matter as long as they are increating the total profit.
If you sell 1 million gas cars at 20% profit, and can sell 1 million EVs at 10% margin, you are still better off selling the EVs and taking the 15% margin on 2 million cars.
The idea that ford is dialing back production because it lowers their percent margin isnt a realistic justification. especially after the funds have been sunk in manufacturing.
It always surprised me that this was not true in air and airplane wings were supposedly best when glossy. So now it turns out that this is indeed not true, and airfoils also benefit from micro-roughness for lowest friction.
Now the surprising question to me is how is it possible that something so simple was not known in this very well-researched and well-funded field. It probably was known, just not by the paper-publishing researchers.