Not All Ski Cores Are Created Equal—Here’s What You Need to Know
You don’t have to be a ski historian or engineer to understand why wood is important for ski construction. Here's what you need to know.
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What type of wood is best for skis? – Jonathan S.; Truckee, Calif.
Every ski in last year’s Gear Guide had a wood core. In fact, the vast majority of all modern skis for intermediate through expert skiers have solid wood cores. So it makes sense that skiers looking for high-performing, durable skis still seek out planks made with wood.
To answer that question, it’s important to understand what the wood core does in modern skis.
“The core is a span to keep things separate,” says Andy Hytjan, head of product development at Season Eqpt. and a former engineer at Armada Skis. “It’s also a filler that can achieve stiffness, dampness, and add or reduce weight.”
The “things” Hytjan refers to include metal, carbon, fiberglass, and other modern composites that have more influential performance characteristics for skiing, and are better at not falling apart compared to wood. For the most part, recent ski evolution has seen more modification and manipulation of these modern composites, while the shape and design of wood cores have remained relatively unchanged. The types of woods used, however, have changed a lot since 2000.
“What a core does is transfer shear between face sheets,” explains Jed Yeiser, the lead engineer at K2 Skis. “And different types of wood have different properties for doing so.”
Hard Wood Roots
Skis made over a decade ago used thick cores of heavier or denser woods, such as ash, birch, and fir. The purpose of these woods and their densities were to prevent skis from breaking. While the thickness of the wood has decreased as the use of other materials has become more prevalent, many race skis, high-performance carving skis, and even some frontside skis still use these types of wood.
“What we look for in wood is to make things feel quiet,” remarks Hytjan. “And these [hard woods] are solid, stable, and damp creatures.”
Related: The Best Carving Skis of the Year
Resort-specific skis made in Europe that use hard woods usually incorporate ash or beech, while skis made in North America and Asia tend to use maple. These woods provide a “precise, powerful feel,” according to Yeiser, “but a full maple core might feel harsh” to most recreational skiers.
Both Yeiser and Hytjan note that the material characteristics of bamboo, which is technically grass, match these hard woods. Unfortunately, bamboo requires a significant amount of processing using heavy chemicals, including formaldehyde, before it can be used as a ski core.
“There wasn’t enough performance enhancement to justify using bamboo considering the chemicals,” says Yeiser, explaining why bamboo has fallen out of fashion for most ski brands over the last 10 years.
Soft Wood Revolution
As the quality of glue and composites has improved over the past decade, softer woods like aspen, poplar, paulownia, caruba, and even balsa have become increasingly popular. This has coincided with consumer demand for lighter equipment for both resort and backcountry skiing.
Using softer woods presents greater risks in terms of grain orientation. There needs to be enough consistency throughout the core’s grain to provide an even flex, but enough variability to prevent the wood from falling apart. Because softer wood’s grain runs very similarly, certain steps need to be taken to prevent delamination—where the wood fractures into layers.
K2’s solution to this problem for many of its resort skis is to use an aspen veneer. These thin layers of wood provide enough variability in grain orientation to keep the ski’s flex smooth. But the veneer also requires more glue, which means the skis are heavier.
Balsa’s grain orientation is even more likely to fall apart. A ski core manufacturer in Switzerland, Bcomp, creates wood cores of balsa with customized grain orientation. This process makes Bcomp’s product prohibitively expensive for most ski makers, and the brands that do use these cores are usually more costly for consumers.
“The performance of balsa wasn’t high enough to justify the price tag compared to paulownia,” says Yeiser, referring to the wood used in K2’s backcountry-specific skis.
The most popular wood cores in most modern all-mountain skis use poplar, paulownia, and caruba. (“Paulownia and caruba are mechanically the same wood,” notes Hytjan.) These woods are slightly less dense than aspen and slightly heavier than balsa. Combined with modern composites like Titanal, carbon, ABS sidewalls, and fiberglass, they provide a high level of performance with less weight.
For Season Eqpt., a brand that makes one-ski quiver options designed to last a long time to cut down on wasteful consumption, the solution is to use one type of wood in each ski and then use other materials and unique geometries to provide specific skiing characteristics.
“Our Aero ski uses Titanal, while the Nexus and Forma skis use fiberglass,” says Hytjan. Otherwise, “all of Season’s skis use paulownia wood cores with thick sidewalls.”
Learn about Season Eqpt.: Meet the Dad Who Launched a New Ski Company While Homeschooling His Daughter During a Pandemic
Hybrid Wood Cores
Some ski makers combine soft and hard woods in their cores, and others are starting to experiment with foam/wood combos. Additionally, certain brands are playing with a vertical orientation of both wood and metal, a process that essentially cuts the foundational wood core in half to add different performance characteristics to the ski.
Hytjan points out that the most important factors in a ski’s character are the materials included that are not wood, and emphasizes that keeping things simple is the best bet for most.
“The more things you glue together creates more places for glue to fall apart,” says Hytjan.