How to Make a Sled Go Faster, According to Science


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.

Tribology and Capillary Drag

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


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.


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.

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 crosscountry 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


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.

Looking to Downsize? You Can Buy a 5-Room DIY Cabin on Amazon for Less Than $33,000

Five rooms of one's own.
Five rooms of one's own.

If you’ve already mastered DIY houses for birds and dogs, maybe it’s time you built one for yourself.

As Simplemost reports, there are a number of house kits that you can order on Amazon, and the Allwood Avalon Cabin Kit is one of the quaintest—and, at $32,990, most affordable—options. The 540-square-foot structure has enough space for a kitchen, a bathroom, a bedroom, and a sitting room—and there’s an additional 218-square-foot loft with the potential to be the coziest reading nook of all time.

You can opt for three larger rooms if you're willing to skip the kitchen and bathroom.Allwood/Amazon

The construction process might not be a great idea for someone who’s never picked up a hammer, but you don’t need an architectural degree to tackle it. Step-by-step instructions and all materials are included, so it’s a little like a high-level IKEA project. According to the Amazon listing, it takes two adults about a week to complete. Since the Nordic wood walls are reinforced with steel rods, the house can withstand winds up to 120 mph, and you can pay an extra $1000 to upgrade from double-glass windows and doors to triple-glass for added fortification.

Sadly, the cool ceiling lamp is not included.Allwood/Amazon

Though everything you need for the shell of the house comes in the kit, you will need to purchase whatever goes inside it: toilet, shower, sink, stove, insulation, and all other furnishings. You can also customize the blueprint to fit your own plans for the space; maybe, for example, you’re going to use the house as a small event venue, and you’d rather have two or three large, airy rooms and no kitchen or bedroom.

Intrigued? Find out more here.

[h/t Simplemost]

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

10 Facts About Real Genius On Its 35th Anniversary

Val Kilmer stars in Martha Coolidge's Real Genius (1985).
Val Kilmer stars in Martha Coolidge's Real Genius (1985).
Sony Pictures Home Entertainment

In an era where nerd is a nickname given by and to people who have pretty much any passing interest in popular culture, it’s hard to imagine the way old-school nerds—people with serious and socially-debilitating obsessions—were once ostracized. Computers, progressive rock, and role-playing games (among a handful of other 1970s- early '80s developments) created a path from which far too many of the lonely, awkward, and conventionally undateable would never return. But in the 1980s, movies transformed these oddballs into underdogs and antiheroes, pitting them against attractive, moneyed, successful adversaries for the fate of handsome boys and pretty girls, cushy jobs, and first-place trophies.

The 1985 film Real Genius ranked first among equals from that decade for its stellar cast, sensitive direction, and genuine nerd bona fides. Perhaps fittingly, it sometimes feels overshadowed, and even forgotten, next to broader, bawdier (and certainly now, more problematic) films from the era like Revenge of the Nerds and Weird Science. But director Martha Coolidge delivered a classic slobs-versus-snobs adventure that manages to view the academically gifted and socially maladjusted with a greater degree of understanding and compassion while still delivering plenty of good-natured humor.

As the movie commemorates its 35th anniversary, we're looking back at the little details and painstaking efforts that make it such an enduring portrait not just of ‘80s comedy, but of nerdom itself.

1. Producer Brian Grazer wanted Valley Girl director Martha Coolidge to direct Real Genius. She wasn’t sure she wanted to.

Following the commercial success of 1984’s Revenge of the Nerds, there was an influx of bawdy scripts that played upon the same idea, and Real Genius was one of them. In 2011, Coolidge told Kickin’ It Old School that the original script for Real Genius "had a lot of penis and scatological jokes," and she wasn't interested in directing a raunchy Nerds knock-off. So producer Brian Grazer enlisted PJ Torokvei (SCTV) and writing partners Babaloo Mandel and Lowell Ganz (Splash, City Slickers) to refine the original screenplay, and then gave Coolidge herself an opportunity to polish it before production started. “Brian's original goal, and mine, was to make a film that focused on nerds as heroes," Coolidge said. "It was ahead of its time."

2. Martha Coolidge’s priority was getting the science in Real Genius right—or at least as right as possible.

In the film, ambitious professor Jerry Hathaway (William Atherton) recruits high-achieving students at the fictional Pacific Technical University (inspired by Caltech) to design and build a laser capable of hitting a human-sized target from space. Coolidge researched the subject thoroughly, working with academic, scientific, and military technicians to ensure that as many of the script and story's elements were correct. Moreover, she ensured that the dialogue would hold up to some scrutiny, even if building a laser of the film’s dimensions wasn’t realistic (and still isn’t today).

3. One element of Real Genius that Martha Coolidge didn’t base on real events turned out to be truer than expected.

From the beginning, the idea that students were actively being exploited by their teacher to develop government technology was always fictional. But Coolidge learned that art and life share more in common than she knew at the time. “I have had so many letters since I made Real Genius from people who said, 'Yes, I was involved in a program and I didn’t realize I was developing weapons,'" she told Uproxx in 2015. “So it was a good guess and turned out to be quite accurate.”

4. Val Kilmer walked into his Real Genius audition already in character—and it nearly cost him the role.

After playing the lead in Top Secret!, Val Kilmer was firmly on Hollywood’s radar. But when he met Grazer at his audition for Real Genius, Kilmer decided to have some fun at the expense of the guy who would decide whether or not he’d get the part. "The character wasn't polite," Kilmer recalled to Entertainment Weekly in 1995. "So when I shook Grazer's hand and he said, 'Hi, I'm the producer,' I said, 'I'm sorry. You look like you're 12 years old. I like to work with men.'"

5. The filmmakers briefly considered using an actual “real genius” to star in Real Genius.

Among the performers considered to play Mitch, the wunderkind student who sets the movie’s story in motion, was a true genius who graduated college at 14 and was starting law school. Late in the casting process, they found their Mitch in Gabriel Jarrett, who becomes the third generation of overachievers (after Kilmer’s Chris and Jon Gries’s Lazlo Hollyfeld) whose talent Hathaway uses to further his own professional goals.

6. Real Genius's female lead inadvertently created a legacy for her character that would continue in animated form.

Michelle Meyrink, Gabriel Jarret, Val Kilmer, and Mark Kamiyama in Real Genius (1985).Sony Pictures Home Entertainment

Michelle Meyrink was a staple of a number of ‘80s comedies, including Revenge of the Nerds. Playing Jordan in Real Genius, she claims to “never sleep” and offers a delightful portrait of high-functioning attention-deficit disorder with a chipper, erratic personality. Disney’s Chip 'n Dale: Rescue Rangers co-creator Tad Stones has confirmed that her character went on to inspire the character of Gadget Hackwrench.

7. A Real Genius subplot, where a computer programmer is gaming a Frito-Lay contest, was based on real events.

In the film, Jon Gries (Napoleon Dynamite) plays Lazlo Hollyfeld, a reclusive genius from before Chris and Mitch’s time who lives in a bunker beneath their dorm creating entries to a contest with no restrictions where he eventually wins more than 30 percent of the prizes. In 1969, students from Caltech tried a similar tactic with Frito-Lay to game the odds. But in 1975, three computer programmers used an IBM to generate 1.2 million entries in a contest for McDonald’s, where they received 20 percent of the prizes (and a lot of complaints from customers) for their effort.

8. One of Real Genius's cast members went on to write another tribute to nerds a decade later.

Dean Devlin, who co-wrote Stargate and Independence Day with Roland Emmerich, plays Milton, another student at Pacific Tech who experiences a memorable meltdown in the rush up to finals.

9. The popcorn gag that ends Real Genius isn’t really possible, but they used real popcorn to simulate it.

At the end of the film, Chris and Mitch build a giant Jiffy Pop pack that the laser unleashes after they redirect its targeting system. The resulting popcorn fills Professor Hathaway’s house as an act of revenge. MythBusters took pains to recreate this gag in a number of ways, but quickly discovered that it wouldn’t work; even at scale, the popcorn just burns in the heat of a laser.

To pull off the scene in the film, Coolidge said that the production had people popping corn for six weeks of filming in order to get enough for the finale. After that, they had to build a house that they could manipulate with hydraulics so that the popcorn would “explode” out of every doorway and window.

10. Real Genius was the first movie to be promoted on the internet.

A week before Real Genius opened, promoters set up a press conference at a computer store in Westwood, California. Coolidge and members of the cast appeared to field questions from press from across the country—connected via CompuServe. Though the experience was evidently marred by technical problems (this was the mid-1980s, after all), the event marked the debut of what became the online roundtable junket.