Sledding gear, snow tactics and physics of fun

Arkansas Democrat-Gazette/BENJAMIN KRAIN --12/26/12--
Cole Harrison sleds down a hill Wednesday morning in Maumelle.  A historic Christmas night winter storm dropped upwards of a foot of snow on parts of Arkansas, shutting down workplaces, downing trees and power lines and turning travel treacherous. As of Wednesday afternoon more than 182,000 Entergy customers were without electricity. More than 90,000 of those were in Pulaski County.
Arkansas Democrat-Gazette/BENJAMIN KRAIN --12/26/12-- Cole Harrison sleds down a hill Wednesday morning in Maumelle. A historic Christmas night winter storm dropped upwards of a foot of snow on parts of Arkansas, shutting down workplaces, downing trees and power lines and turning travel treacherous. As of Wednesday afternoon more than 182,000 Entergy customers were without electricity. More than 90,000 of those were in Pulaski County.

Before uniform municipal garbage carts marched across the land, snow fell heavily upon the owners of round-lidded trash cans.

"Oh yeah," says Sam Cooper, remembering winters four decades ago when naughty sledders snagged lids from yards in Little Rock's Kingwood neighborhood. "As a kid, yeah, you hop on it and ride.

"And you know, we tried all kinds of things to sled on. Everything from garbage can lids to cardboard boxes, skateboards without the wheels and trucks. Some worked well, some didn't."

These days, front-yard garbage cans don't give up their lids without a fight; and inexpensive plastic discs, boards, snow seats and even classic metal-runnered Flexible Flyers are readily available ... unless the forecast calls for snow.

One minute the jocular TV weather guy pokes his tanned finger at a tie-dye map and the next minute, boxed milk, toilet paper and loaf upon loaf of squishy white bread go rolling toward checkout. Followed by sleds. That is, sleds that haven't already been bought as Christmas gifts.

Most years, sleds start sliding out the door of Kraftco in November, says John Hill, manager of the 65-year-old hardware and building supply store on Cantrell Road. "Of course with that little bit of snow or ice or whatever we had here in November, that triggered a lot more sales," he notes.

Plenty of shoppers wait until snowflakes fall. But, he adds, if the weather guy says, "'OK, we're going to get 2 to 4 or 4 to 6 inches, so we know it's coming' -- even though they may be wrong, and they really do gum it up -- then, yeah, we can sell a whole bunch and it not even be doing anything out there."

If there's ice already on the ground, good luck getting to the store to buy sleds. "It's just like anything in demand, they're gone in no time," Hill says.

Kraftco typically has a few sleds on hand any time of year, but Hill starts trying in October to acquire the modern range of models from Paricon Flexible Flyer for the Christmas rush. Store managers used to order such sliding stock earlier in the year, but the Great Recession wrought strategic changes in wholesale supply chains. "Most of your wholesalers now have gotten more just like the big box stores," Hill says.

Suppliers don't have warehouses piled up with sleds year-round. "Same way with heaters and ice melt and those kind of things. They'll wait until closer to the season and then start stocking them, and then they only order so many. Once they're gone, they're gone for the season."

The range of sleds available from stores like Kraftco and from in-state chains includes the classic Flexible Flyer, wooden slats supported by two metal runners; plastic saucers (thin discs roughly the size of the old front-yard garbage can lid); plastic torpedo-shaped trays with raised rims; and foam boards similar to wakeboards but with a hard plastic bottom.

Sometimes it's also possible to find single-fanny, shovel-shaped polyethylene discs or, for small bodies, ski-inspired raised saddles on three plastic runners with a steering wheel.

Assuming limited supply and limited money, which sort of sled would be the best investment for an Arkansan whose goal was doing as much sledding as possible on a sled that moved as fast as possible?

EXPERTS DISAGREE

Hill says, "It depends on the kind of snow and ice.

"Most times you're only going to use the plastic stuff. Certain ice events or snow events where it's more of a harder packed thing where the rails won't just sink into the snow, then you can use those regular Flexible Flyers. But it's got to be a good hard surface.

"The plastic stuff you'll have more chance of using more often."

Sam and Tracy Cooper are raising their family in the same hilly Kingwood where Sam grew up, and so their son Sean has benefited from his father's insider information on "awesome" sledding. In February 2011 when Sean was 8, Sam strapped a GoPro camera to his son's head and sent him on a 2-minute rocketing ride from the Cammack Village tennis courts on iced-over Brentwood Road down crunchy Crouchwood Road. Sean fetched up on Blackwood Road.

Then father and son stacked themselves atop the Flexible Flyer sled and did the same run together, going farther -- they stopped on Pine Valley Road. Video evidence is at bit.ly/1vAFodI.

Besides providing a practical illustration of Newton's First Law of Motion (the one about inertia), the two trips illustrate why Sam Cooper says that, if forced to choose one sled, "my go-to is always going to be the Flexible Flyer traditional sled. Because they go faster, and you can create a lot longer of a run."

Anyone tempted to take on street sledding really needs a maneuverable sled, he says. "If you can eliminate going through intersections and stop signs, that's best. And if your route does include some intersections, then probably best to have a spotter, someone nearby an intersection who can wave you off if there's a car coming or any danger, or wave you on through if it's clear."

It makes sense that a 48-year-old would favor the tool of epic memories, but 12-year-old Sean is closer to the action, and his priority is, well, action. He has seen more powdery snow, and once the thaw starts, thin and muddy surfaces. If he could only have one sled, it would be ...

"It's like foam with a plastic bottom. Imagine a big fat surfboard but shorter, like a 4-foot surfboard that's really wide."

Ice is nice but "the powdered snows, I like them more," Sean says. "It's just more fun. I figure you go faster down one of the powdered hills and it's more fun to crash on powder. If you crash on the Flexible Flyer, it will hurt."

Note that the Coopers stay ready for various conditions. Besides the classic wooden sled, they have a plastic toboggan type with a flat bottom that can hold three small kids and the foam board Sean likes so much.

"The nice thing about some of the plastic materials is that they're light," Sam Cooper concedes. "So you're not dragging around a heavy sled. If you're marching up and down hills and dragging it all over the neighborhood, it's not too exhausting to get around with."

But with a nod toward (ahem!) safety, Sam Cooper notes that a classic wooden sled can be steered. Not so with a plastic disc: "That's a little hard to control."

THINK: ENERGY

Lack of control is the very feature that appeals to Todd Tinsley's children.

Tinsley is not an expert on sledding, merely an associate professor of physics at Hendrix College who studies how the most fundamental constituents of matter behave in electromagnetic fields. "Sledding is way more complex than the kinds of problems I look at," he says, and he's not joking.

Google: "physics of sledding." Count the websites in which giddy physics students or their teachers attempt to diagram unseen forces that propel or slow down sleds.

Some of these websites are less confusing than others, but all claim to be simplifying their explanations by ignoring certain forces to concentrate on:

• Friction

• Gravity (more than one kind) and

• "The normal force," which is a bland term for whatever natural magic keeps stationary objects from falling through solid ground.

One site even enlists Calvin and Hobbes cartoons to obfuscate what otherwise might sound like common sense. Common sense and physics do agree on a few easy-to-grasp basics, Tinsley says: "It's more advantageous a lot of times to think about where your energy is going."

Up atop the snowy hill, a sled has potential energy, waiting to be unleashed. Use some energy pushing off and there comes the equal and opposite reaction -- moving forward and downhill in obedience to gravity. So then for a fast ride, the goal is avoiding factors that drag down the unfolding flow of energy. Friction is the big one, so the best sled would minimize friction.

The Flexible Flyer style focuses the rider's weight on two thin metal runners. As with the metal blades on ice skates, these runners don't dig into the ice. "In fact," Tinsley says, "the great thing about ice skates is when the front of that skate starts to go across the ice, the friction actually causes the ice to melt a little bit and the rest of that blade travels across a layer of water, which really lowers friction.

"So you can imagine that if you want a sled that goes really fast on ice, something that takes all of your body weight and spreads it on very little, thin rails will actually do the same effect."

But when the surface isn't hard, those heavily loaded blades carve into the snow. "Then as your sled is going down the hill, it has to move snow out of its way, and that's no fun," he says. "If you're using all of the energy that you got by being up at the top of this hill to move snow out of your way, then that's less available to you to go fast.

"One of these toboggans or the big discs, they actually spread your weight over a longer or much broader area, and what that means is when you hit a little bump in the snow, it's more advantageous for your disc to travel over that bump rather than through that bump. And so you lose less energy. That actually ends up helping you go faster ..." but with less stability:

"Whether it's the Flexible Flyer or a long toboggan, things that are long like that are very stable, so they don't begin to turn very easily. But those discs lack all stability, so you'll spin around and you'll go different directions.

"And my family loves that."

They sled on a golf course with no trees to avoid. "Control is something we don't seek in our sledding," Tinsley says.

ActiveStyle on 12/15/2014

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