Mountain Experts: Boreal’s Eric Rosenwald
December 23, 2008
BOREAL MOUNTAIN RESORT “-You don’t have to be an X-Games contestant to understand the importance of speed control when taking to the air off a ski resort terrain park jump. It’s obvious that if you go too slow you’ll come up short of the landing, but if you go too fast, you could dangerously overshoot the landing.
As park jumps vary from extra-small to triple-extra-large, finding the perfect takeoff speed to float into the sweet spot of the landing is a process of trial and error for avid jumpers. But while smart riders take their first lap over an unknown jump at a reasonable yet cautious speed, then crank up the velocity as necessary on the next pass, not every high-flying guinea pig is quite that brainy.
Every winter, hundreds of skiers and snowboarders worldwide are injured, sometimes even fatally, by launching off a jump going too fast and subsequently falling out of the sky past the transitioned landing zone and on to flat ground.
Although there will never be a cure for overzealous speed demons on the slopes, designing terrain park jumps that are difficult, if not impossible, to overshoot has been one proven solution toward eliminating some of these accidents. The only difficulty is determining the proper dimensions for building such a “fool-proof” jump on a given slope.
Faced with this design problem nearly 10 years ago when building terrain parks in Maine, Boreal Mountain Resort Terrain Park and Core Marketing Manager Eric Rosenwald decided to use his college physics book and a basic knowledge of computer programming to find an answer.
In 1999 Rosenwald created a simple Flash animated computer program that allows him to input the proposed dimensions of a jump and the maximum attainable speed from the jump’s in-run to view a theoretical model of that jump design’s trajectory (the path a jumper will take once airborne).
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Though the program does not mimic every nuance of the real world, it obeys enough of the basic principals of projectile physics to make it a valuable tool for creating jumps that are unlikely to be overshot.
“My jump designer lets you plot theoretical jump trajectories in a perfect world,” said Rosenwald. “The program distills the trajectory down to the two things that are a given ” speed and angle of take off. It doesn’t take into account rider weight, air drag, the friction of the snow, or whether or not you popped off the lip, but it will tell you if you go X speed off a jump with a takeoff angle of Y you will never go farther than Z.”
As the angle of takeoff can be easily modified, the most important real world variable for the modeling program becomes rider speed. To accurately determine the maximum speed a rider could reach before they hit a takeoff at the projected jump location, Rosenwald asks a member of the park staff to mimic the scenario by straight lining the proposed jump in-run while he clocks their speed using a low-tech radar gun.
Once armed with an understanding of the speed of a given slope, Rosenwald will use the jump designer to verify the possible distances and heights of the landing from the takeoff and the ideal transition angle of the landing. The goal is to build a landing that will meet up with the jumper smoothly along the arc of their trajectory.
“There are always several different safe design possibilities within a trajectory,” said Rosenwald. “You can build a step down that has more free-fall time, a step up that catches the rider at the apex of their trajectory, or a true tabletop jump where the landing is at the same height as the takeoff.”
Leaving his computer with ideal dimensions in mind, Rosenwald takes to the seat of his snowcat and begins to build. Accurately measuring the steepness of a landing or the angle of a takeoff from inside the cat is too much to eyeball, however, so he places a digital level on the side of the machine’s cabin to take a precise reading.
As you can imagine, all of Rosenwald’s meticulous modeling and measuring adds up to a consistently top notch finished product that both riders and the ski industry take notice of. Year after year Boreal Mountain Resort’s terrain parks are rated among the best in the country and despite having massive pro-caliber jumps open to the public, insurance inspectors have no problems with them.
Using the jump designer, Rosenwald hopes to keep it that way.
“Modeling park features on the computer shows were not just cat jockeys pushing snow around. These designs aren’t by the seat of our pants,” said Rosenwald. “Our insurance carrier is very supportive of basically anything I can sleep with at night. One of the foundations of that trust is what I’ve shown with the jump designer.”