How to Make a Sled Go Faster, According to Science

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So you have a need for speed. Sled speed. You've already picked a steep slope and streamlined your form. Maybe you're wearing a skintight Lycra luge racing suit and have shaved your head. Maybe you've shaved everything—when you're battling air resistance, you can't leave anything to chance.

Let's assume you've scratched all that off your to-do list and now want to reduce friction between your sled and the ground. In other words, you're Clark Griswolding this sucker and need some solid toboggan lube.

Can science help you go faster? Yes, it can.

The science of friction and lubrication—what's called tribology—has focused greatly on snow and ice: The research is valued by avalanche researchers, automobile and tire manufacturers, and America's $20 billion winter sports industry. The consensus? You need to exploit the properties of "melt-water lubrication."

When sledders zoom down a hill, they're not traveling atop pure snow—they're skimming across a microscopically thin layer of meltwater. This water, created by the friction of the moving sled, is your primary lubricant. According to researchers [PDF] at the ski company Swix, the ideal meltwater layer is 50 molecules thick and occurs at around 32°F. Anything warmer will produce excess meltwater that can cling to your sled. This process, called capillary drag, decreases speeds.

Bitterly cold snow isn't better. When the mercury drops below 14°F, it's difficult to find a significant layer of lubricating meltwater. "When it's that cold, the liquid layer is not going to form without an excessive amount of friction," Kenneth Libbrecht, a Caltech physicist and snowflake specialist (who also served as snowflake consultant on Disney's Frozen), tells Mental Floss. In these conditions, the meltwater layer may be as thin as a single H20 molecule, making your sled scrape against the asperities, or rough edges, of packed snow. You might as well be attempting to ride down a sand dune [PDF].

Unless you're the Winter Warlock or the Chinese government, you probably can't control the weather—but you can control how you prepare for it. Research shows that when it's wet and warm, a rough-bottomed sled etched with a shallow front-to-back pattern may be helpful. The pattern provides a smaller surface area for water molecules to grab, decreasing capillary drag.

At colder temperatures, when snowflakes are sharper and harder, it's important to make the bottom of your sled harder so you can plow over any asperities that would otherwise "grab" at your toboggan and slow you down. So coat the bottom of your sled in a hard, smooth substance like a synthetic hydrocarbon ski wax.

But no matter the temperature, the best way to skim over the meltwater layer is to lube up the bottom of your sled with hydrophobic materials, substances such as grease, oil, and wax that are literally "afraid of water." After consulting with the experts, I tested several hydrophobic lubricants—and I found them all in my house.

ONE MAN, ONE SLED, AND SIX LUBRICANTS

Our experiment took place at the public sledding hill in Woodstock, New York, wedged below the foothills of the Catskill Mountains. The thermometer read 29°F—firmly in the not-too-hot, not-too-cold meltwater Goldilocks Zone—and my backpack was stuffed with everyday hydrophobic materials: a $0.98 wax candle from Walmart, WD-40, PAM cooking spray, a hardwood paste wax, Adobo All-Purpose Seasoning, and bacon grease.

My vehicle? An $11 plastic blue-green sled that was clearly intended to ferry small children.

The slope here was gentle, but the snow was not. It was old, crusty, and hard. I later asked Libbrecht—who has classified 35 different types of snowflakes ("most of them look like sand, just little globs")—how conducive such a surface is for good speed-sledding. He explained that the shape of snowflakes changes quickly upon hitting the ground, becoming more spherical and smooth as they're compacted by the wind, sun, and other sledders. In other words: Like people, snow gets rounder with age.

This is great news for speed, but not so great for steering. On my first dry test run—my control—my average speed was approximately 12.6 mph. On my way down, I completed three pirouettes and cried for help at least once.

Wax Candle

unlit candle in metal holder
iStock

My 12.6-mph pace was a far cry from the world record for fastest sled run (83.5 mph), so I turned to wax.

Downhill snow racers have been using wax for more than a century. Before the 1940s, people tried a wide variety of natural substances to make the sled bottom slick, including beeswax, whale oil, pine resin, and tallow. By the mid-century, tobogganers rubbed their sleds with wax paper or a handy candle. Candles contain paraffin wax, a mix of straight-chained saturated hydrocarbons that contain 20 to 40 carbon atoms.

According to the book The Physics of Skiing, by David Lind and Scott P. Sanders, straight-chained hydrocarbons are the way to go. These molecules orient themselves in parallel structures and have strong intermolecular bonds, which keeps the wax hard at cool temperatures—thus giving better gliding properties. The molecules are also non-polar and don't interact kindly with polar molecules such as water. (Chunkier hydrocarbons, however, that have short chains branching off the primary chain, are softer and "more suitable for … waxes designed to increase traction or grab," write Lind and Sanders.)

Paraffin wax is also relatively hard and should do a good job riding over snow asperities as long as the snow isn't bitterly cold. And it does: For two minutes, I rubbed the cold candle into the base of the sled using a circular motion. Once my butt hit the sled, I was cruising. I hit approximately 17.98 mph.

WD-40

According to a comprehensive list, WD-40 has more than 2000 uses: It can remove gum from school bus seats, lubricate the wheels of tuba cases, and even prevent puppies from chewing on telephone lines. Also on the list: "Lubricates sleds and toboggans" [PDF].

This is no surprise: WD stands for "water displacement." And while the formula is technically secret, the sleuths at WIRED used gas chromatography in 2009 to reveal the black magic inside. Their conclusion: alkanes. Alkanes are water-repellant hydrocarbons that refuse to bond with either hydrogen or oxygen. In other words, exactly what I need under my sled.

It worked: After a noxious 10-second spray, the WD-40 clocked the same time as candle wax. But, phew, did my trip smell ungodly. Not only that, but I later learned that some alkanes are key to the German cockroach's ability to produce pheromones meant to attract mates. So I had that to look forward to.

PAM Original No-Stick Cooking Spray

If I were a scientist, I'd be testing all of these materials with the aim of determining their coefficient of friction, a figure that quantifies the amount of friction between two surfaces. It can be expressed by the following formula, which is, fittingly, dying to spell the word fun.

mathematical formula for sledding down a hill
Lucy Quintanilla, Mental Floss

You can measure the kinetic friction of materials with an instrument called an oscillograph. Unfortunately, I work for a media company. We don't have oscillographs.

However, I wish I had one for this part of the experiment. Because while the coefficient of friction for this skin-scraping snow was certainly low, I can't speak for my sled rub-a-dub-dubbed in canola oil. It should have had a low coefficient of friction, but the "No-stick" spray lived true to its name in all the wrong ways—by failing to stick to the bottom of my sled. It disappeared almost immediately, making my PAM time just as slow as my control run.

Hardwood Paste Wax

Paste wax is the lubricant of champions. Just ask Tom Cox, a former champion of the U.S. National Toboggan Championships, held annually in Camden, Maine. Cox is also its chief toboggan inspector, ensuring that the 400 wooden sleds that race every year meet the competition's guidelines.

He's seen all sorts of substances slathered onto the bottom of sleds, from cross country wax to lemon Pledge. "Everybody does it different, and I can't tell you what the secret is," Cox tells Mental Floss. "I won the whole thing in 2003, and we used a paste wax, a hardwood floor wax, but I don't know if that's the answer, because I haven't won since."

Cox may be stuck in a competitive rut, but he's a proven champion, and I trust his methods. That said, I quickly learned that paste wax is best smeared on wood, not plastic. Using my hands, I spread the soft wax; it was lumpy and uneven, like dried-out peanut butter. I attracted quizzical glances from passersby who perhaps thought I was gobbing sandwich spread onto my sled. Oh, and it left a chunky brown trail of goop down the hill.

But who cares? My sled nearly hit 20 miles per hour.

In conditions like these, flirting with snow's melting point, a softer wax like paste wax may be ideal. The coefficient for waxed wood on dry snow is remarkably low: 0.04. (The closer the number is to zero, the slippier it is. For comparison, the coefficient for ice-against-ice is around 0.03.) I can only imagine how low the number might be for a plastic kiddie sled.

Adobo All-Purpose Seasoning

Another special ingredient that has also appeared on the bottom of sleds at the National Toboggan Championships? Onion powder.

Some sledders think that applying a fine powder is like adding tiny ball bearings to the bottom of a sled. In truth, a mildly grainy bottom may help reduce capillary drag in warm conditions, stopping any clingy meltwater from hitching a ride. You can see this happen with superhydrophobic materials such as lotus leaves, which are composed of thousands of tiny microscopic pillars. Those raised bumps decrease the points of contact between the leaf and a water droplet, ensuring that water will simply roll off. In fact, dozens of ski wax manufacturers are attempting to create waxes that mimic the nanostructure of lotus leaves. It's this principle that I hoped I could achieve with onion powder.

But when I couldn't find onion powder in my kitchen, I turned to Adobo seasoning, which might as well be the WD-40 of seasoning. Chicken. Steak. Chicken-fried steak. You can sprinkle this pixie dust on anything and it just works. Adobo might not contain onion powder, but if it can trick unwitting people into believing that I'm a talented cook, perhaps it could work similar magic on my sledding abilities. I wetted the bottom of my sled with a spritz of water and generously seasoned my plastic chariot.

It flopped. Whatever the reason, after three futile attempts down the hill, all the Adobo did was leave behind a glowing trail of yellow snow.

Bacon Grease

bacon frying in a pan
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Before the 2018 Super Bowl, Philadelphia police prevented rabid Eagles fans from converting local streetlights into adult-sized monkey bars by scrubbing the city's utility poles with Bio-Bottle Jack Hydraulic Fluid, an environmentally friendly lubricant. I was hungry to apply this legendary goo to my sled, but when I called local suppliers and asked to purchase it, all of them told me delivery would take weeks. I suspected the city of Philadelphia had gobbled up the east coast's stockpile.

So I turned to the NFC Championship Game, when Philly's police slathered utility poles with Crisco. Thankfully, I had a better alternative in my fridge: bacon fat. Anybody who has tried to wash their hands of rendered pig blubber knows that it hates water. Indeed, the grease spread onto my sled like melted butter. It was soft and waxy, and its smell mingled with all of the other scents on my hands—vanilla, canola oil, aerosol propellant, potential cockroach pheromone, paste wax, chicken seasoning—to create a miasma that is beyond my abilities to describe. I may or may not have licked my fingers. I may or may not have regretted it.

Around this time, a mother and a small child began walking toward the hill. I waved to them. They stopped and gaped at me, this disheveled grown man sitting alone on a hill of brown and yellow snow, surrounded by discarded bottles of WD-40 and all-purpose seasoning, vigorously scrubbing a strange grease on the bottom of a fluorescent sled built for small children. The mother grabbed her child's hand and scurried in the opposite direction.

Anyway! Bacon grease clocked in at 17 miles per hour.

Perhaps I applied the grease too thickly. According to Lind and Sanders, an application of running wax should be between 0.005 and 0.02 millimeters thick: "If these final wax layers were any thicker, they would be more likely to pick up dirt from the surface of the snow, which, as we have seen, would increase friction."

In other words, there is such a thing as too much lube. When I buffed down the bacon grease with a cloth towel, I hit 19 miles per hour.

TIPS FOR YOUR RIDE

My sledding experiments weren't exactly scientifically rigorous. They weren't properly controlled. My sled never took the same route down the hill. The number of confounding variables that could have skewed each result is, well, confounding.

But the results do echo the advice of experts: If you can, sled in temperatures around 32°F, when the meltwater is an optimal thickness. Avoid the temptation of freshly fallen snow, and wait for those sharp snowflakes to be smoothed into a polished sledding path. If you have a wooden sled, sand it. (According to Cox, "The ones that go the fastest [at the National Toboggan Championships] are sanded before you put wax on it, sanded with a very, very fine paper, maybe 1500 grit.") If you can, choose an inner tube over a plastic sled. In a 2009 Journal of Trauma study titled "Sledding: How Fast Can They Go?" researchers found that inner tubes travel an average of 2 mph faster than plastic.

If you must use plastic, opt for polyethylene. It's hydrophobic and cheap. According to the glaciologist Samuel Colbeck, polyethylene is "hard, highly elastic, can be smoothed and imprinted with different patterns, can be made porous, can be easily coated with waxes, does not readily adhere to ice, and has a [coefficient of friction] that is not greatly affected by surface contamination" [PDF]. Lastly, coat your sled in a hydrophobic wax: A fluorocarbon ski wax is optimal, but do-it-yourselfers can always keep a candle in their pocket.

Also, bring Adobo. It won't make your sled faster, but it will leave a trail of bright yellow snow, guaranteeing you will have the hill all to yourself.

 

For more on the physics of snow sports, Mental Floss recommends David Lind and Scott P. Sanders's remarkable and authoritative book The Physics of Skiing.

Watch a Gulper Eel Inflate Like a Terrifying Balloon

OET, NautilusLive.org
OET, NautilusLive.org

Since launching in 2008, the Ocean Exploration Trust's Nautilus research vessel has live-streamed a purple orb, a transparent squid, and a stubby octopus from the bottom of the ocean. The latest bizarre example of marine life captured by the vessel is a rare gulper eel that acts like a cross between a python and a pufferfish.

As Thrillist reports, this footage was shot by a Nautilus rover roaming the Pacific Ocean's Papahanaumokuakea Marine National Monument 4700 feet below the surface. In it, a limbless, slithery, black creature that looks like it swallowed a beach ball can be seen hovering above the sea floor. After about a minute, the eel deflates its throat, swims around for a bit, and unhinges its jaw to reveal a gaping mouth.

The reaction of the scientists onboard the ship is just as entertaining as the show the animal puts on. At first they're not sure what they're looking at ("It looks like a Muppet" someone says), and after being blown away by its shape-shifting skills, they conclude that it's a gulper eel. Gulper eels are named for their impressive jaw span, which allows them to swallow prey much larger than themselves and puff up to intimidate predators. Because they like to lurk at least 1500 feet beneath the ocean's surface, they're rarely documented.

You can watch the inflated eel and hear the researcher's response to it in the video below.

[h/t Thrillist]

10 Electrifying Facts About Michael Faraday

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iStock

This world-changing genius was born into poverty on September 22, 1791. Fortunately for us, Michael Faraday refused to let his background stand in his way.

1. HE WAS LARGELY SELF-EDUCATED.

In Faraday's boyhood home, money was always tight. His father, James, was a sickly blacksmith who struggled to support a wife and four children in one of London's poorer outskirts. At age 13, young Faraday started helping the family make ends meet. Bookseller George Ribeau (sometimes spelled Riebau) took him on as an errand boy in 1804, with the teen's primary job being the delivery and recovery of loaned-out newspapers.

Shortly after Faraday's 14th birthday, Ribeau offered him a free apprenticeship. Over the next seven years, he mastered the trade of bookbinding. After hours, Faraday remained in Ribeau's store, hungrily reading many of the same volumes he'd bound together.

Like most lower-class boys, Faraday's formal schooling was very limited. Between those bookshelves, however, he taught himself a great deal—especially about chemistry, physics, and a mysterious force called "electricity."

2. A 300-PAGE NOTEBOOK LAUNCHED HIS SCIENTIFIC CAREER.


Wikimedia Commons // CC BY 4.0 

Sir Humphry Davy (above) left a huge mark on science. In the year 1808 alone, the man discovered no less than five elements, including calcium and boron. An excellent public speaker, Davy's lectures at the Royal Institution consistently drew huge crowds. 

Twenty-year-old Faraday attended four of these presentations in 1812, having received tickets from a customer. As Davy spoke, Faraday jotted down detailed notes, which he then compiled and bound into a little book. Faraday sent his 300-page transcript to Davy. Duly impressed, the seasoned scientist eventually hired him as a lab assistant. Later in life, Davy was asked to name the greatest discovery he'd ever made. His answer: "Michael Faraday."

Tension would nevertheless erupt between mentor and protégé. As Faraday's accomplishments began to eclipse his own, Davy accused the younger man of plagiarizing another scientist's work (this rumor was swiftly discredited) and tried to block his admission to the Royal Society.

3. IF IT WEREN'T FOR FARADAY, WE MIGHT NOT HAVE ELECTRIC POWER.

On September 3, 1821, Faraday built a device that ushered technology into the modern era. One year earlier, Danish physicist Hans Christian Ørsted had demonstrated that when an electric current flows through a wire, a magnetic field is created around it. Faraday capitalized on this revelation. Inside the Royal Society basement, he began what was arguably his most groundbreaking experiment by placing a magnet in the bottom of a mercury-filled glass container. Dangling overhead was a wire, which Faraday connected to a battery. Once an electric current was conducted through the wire, it began rotating around the magnet.

Faraday had just built the world's first electric motor. How could he possibly top himself? By building the world's first electric generator. His first experiment was comprised of a simple ring of wires and cotton through which he passed a magnet. By doing so, he found that a current was generated. To this day, most electricity is made using the same principles.

4. FARADAY INVENTED THE RUBBER BALLOON.


iStock

By today's standards, his early models would look shabby. Made via pressing two sheets of rubber together, Faraday's balloons were used to contain hydrogen during his experiments. Faraday created his first in 1824 and was quick to praise the bag's “considerable ascending power.” Toy manufacturers started distributing these the following year.

5. HE'S ALSO THE GRANDFATHER OF MODERN REFRIGERATORS.

In 1823, Faraday sealed a sample of chlorine hydrate inside a V-shaped tube. As he heated one end and cooled the other simultaneously, the scientist noticed that a peculiar yellow liquid was starting to form. Curious, he broke open the tube. Without warning, a sudden, violent explosion sent glass shards flying everywhere. Mercifully uninjured, he smelled a strong scent of chlorine in the air.

It didn't take him very long to figure out what had happened. Inside the tube, pressure was building, which liquefied the gas. Upon puncturing the glass, he'd released this pressure and, afterwards, the liquid reverted into its gaseous state. This sudden evaporation came with an interesting side-effect: it cooled down the surrounding air. Quite unintentionally, Faraday thus set the stage for the very first ice-making machines and refrigeration units.

6. HE BECAME AN ANTI-POLLUTION CRUSADER.

Britain's industrialization came at a malodorous price. As London grew more crowded during the mid-1800s, garbage and fecal matter were dumped into the River Thames with increasing regularity. Naturally, the area didn't smell like a rose. In 1855, Faraday penned an oft-reproduced open letter about the problem, imploring the authorities to take action. “If we neglect this subject,” he wrote, “we cannot expect to do so with impunity; nor ought we be surprised if, ere many years are over, a hot season give us sad proof for the folly of our carelessness.”

Just as Faraday predicted, a broiling summer forced Londoners of all stripes to hold their noses. Dubbed “the Great Stink,” the warmer months of 1858 sent the Thames' rancid odor wafting all over the city. Parliament hastily responded with a comprehensive sewage reform bill. Gradually, the putrid stench began to dissipate.

7. HE STARTED THE ROYAL SOCIETY'S CHRISTMAS LECTURE TRADITION.


Alexander Blaikley, Wikimedia Commons, Public Domain

Faraday understood the importance of making science accessible to the public. In 1825, while employed by the Royal Society, he spearheaded an annual series that's still going strong today. That holiday season, engineer John Millington delivered a set of layman-friendly lectures on “natural philosophy.” Every year thereafter (excluding 1939–1942 because of WWII), a prominent scientist has been invited to follow in his footsteps. Well-known Christmas lecturers include David Attenborough (1973), Carl Sagan (1977), and Richard Dawkins (1991). Faraday himself was the presenter on no less than 19 occasions.

8. BRILLIANT AS FARADAY WAS, HE STRUGGLED WITH MATH.

Towards the end of his life, Faraday's lack of formal education finally caught up with him. An underprivileged childhood had rendered him mathematically illiterate, a severe handicap for a professional scientist. In 1846, he hypothesized that light itself is an electromagnetic phenomenon, but because Faraday couldn't support the notion with mathematics, it wasn't taken seriously. Salvation for him came in the form of a young physicist named James Clerk Maxwell. Familial wealth had enabled Maxwell to pursue math and—in 1864—he released equations [PDF] that helped prove Faraday's hunch.

9. AS TIME WORE ON, HE STRUGGLED WITH MEMORY LOSS.

Michael Faraday
iStock

At the age of 48, Faraday's once-sharp memory started faltering. Stricken by an illness that rendered him unable to work for three years, he wrestled with vertigo, unsteadiness, and other symptoms. Following this "extended vacation" [PDF], he returned to the Royal Society, where he experimented away until his early 70s.

However, Faraday was still prone to inexplicable spurts of sudden giddiness, depression, and extreme forgetfulness. “[My] bad memory,” he wrote, “both loses recent things and sometimes suggests old ones as new.” Nobody knows what caused this affliction, though some blame it on overexposure to mercury.

10. EINSTEIN KEPT A PORTRAIT OF FARADAY IN HIS BERLIN HOME.

Fittingly, the father of modern physics regarded Faraday as a personal hero. Once, upon receiving a book about him, Einstein remarked, “This man loved mysterious Nature as a lover loves his distant beloved.”

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