Ski manufacturers are really good at writing up high-tech product descriptions that can bewilder even the dorkiest engineers. Most deal with the construction techniques used to manufacture them, and if you understand those techniques, you’ve cracked this mysterious code. In general, there are three basic construction techniques (Sandwich, Torsion Box, and Cap) used by the masses to build skis and, though they all share some similar elements, their differences can affect a ski’s durability and performance.

To help break it down into manageable bite-sized pieces, I’ll use a mouth-watering lunch-specific analogy to explain what goes into a ski. Most any ski has a core that is typically made of wood or foam; this is the meat. The composites that add stiffness to the ski are the bread of the ski. Some skis have metal or rubber integrated into them which you can think of as the cheese of the ski. Finally you’ve got a Ptex base and some sort of plastic topsheet that you can think of as the plastic wrap that protects your tasty skis from the ravages of winter weather. All the layers are held together by epoxy (a delicious ski condiment) and get compressed and heated up in a big ski press (think massive George Foreman Grill) until the epoxy cures.

Torsion Box Construction – ¡Yo quiero un burrito!
Torsion box skis are a lot like a burrito. Their composite reinforcement comes in the form of a tasty flour tortilla that is wrapped all the way around the carne asada core. The engineering behind this is the classic principle of a closed cross section instead of an open cross section. A closed cross section, like a long rectangular box, is always going to be stronger if the box is taped closed instead of being left open because the forces always have another surface to be transmitted to.

Torsion box skis can often achieve increased stiffness at lower weights. Also, because the hard composite is wrapped all the way around the core, there are no weak points and the skis are more durable. On the downside, because the composites are handling a larger portion of the forces, torsion box skis are sometimes accused of not being damp enough and getting chattery.

Cap Construction – Open Faced Sammies
Skis with cap construction can be thought of as open-faced sandwich. Though they’re similar to torsion box skis in that the composite wraps around the top and sides of the ski, there is no composite (bread) wrapped below the core. Similar to the concept of a rolled up piece of paper being stronger than a flat sheet of paper, cap skis often have some sort of 3D shape built into the ski and that curving of the composite adds additional rigidity and often removes weight from areas where it’s not needed. Because the composite is doing most of the work, foam (bologna) cores are common in cap construction skis.

Cap skis have the benefit of being easy and cheap to manufacture and they don’t have any major weak spots which makes them fairly durable and resistant to delamination. Cap construction skis often don’t retain the same feel and liveliness of the torsion box and sandwich skis and, as a result, cap construction is often used to make entry level and beginner skis though it has been effectively implemented in some high-end skis.

Sandwich Construction – The Italian Hoagie
Sandwich constructed skis are kind of like a big Italian sub. The bread of the sandwich is akin to the topsheet and composite layers above as well as the base material and composite layers below the core of the ski. Like a sub, you can see the meat and cheese of the sandwich hanging out the sides of the ski in the form of a vertical plastic sidewall. This plastic sidewall is just an extension of the core, but unlike salami, it’s intended to withstand impact from edges and nature and protect the core from moisture.

The sharp edge formed by the junction of the sidewall and the hoagie roll is often a weak point of sandwich constructed skis and, as a result, you’ll often see chips in the topsheet and sidewall developing that can eventually lead to delamination. Sandwich skis are very popular, however, because they have superb feel and often more desirable flex characteristics. In addition, the core makes up a larger portion of the flex and that limits chattery vibrations and increases damping.

While some types of funky hybrid ski construction are used, nearly all can be likened to one or two of the three above and it is easy enough to infer performance and durability characteristics from that. Knowing the specifics of what you’re really buying will ensure that you’re satisfied when those new powder boards show up on your doorstep. Just remember to keep some snacks handy the next time you’re scoping gear deals online, because you’re bound to get hungry.

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