Sidewalls
Quote from Alpine Underground on June 27, 2026, 5:10 pmWhat type of sidewall do you use in your construction and why?
When building skis or snowboards, the choice of sidewall material heavily impacts the durability, impact resistance, and torsional stiffness of the final product.
1. Traditional Sidewall Materials (Pre-fabricated)
For standard sandwich or semi-cap constructions where pre-made strips are bonded to the wood core, manufacturers typically use dense, highly durable plastics:•ABS (Acrylonitrile Butadiene Styrene): The industry standard for high-performance skis and boards. ABS is a thermoplastic known for its excellent impact resistance, ability to withstand freezing temperatures without cracking, and high torsional rigidity (which translates to better edge grip on hard snow).
•UHMW-PE (Ultra-High-Molecular-Weight Polyethylene): Tougher and more impact-resistant than ABS, UHMW-PE is often used in park, freeride, or custom skis. It absorbs heavy impacts (like hitting rocks or rails) exceptionally well without compressing, though it requires specialized surface preparation (like flame treatment or sanding) to bond properly with epoxy.
2. Liquid Poured Sidewall Materials
When companies or DIY builders use the "pour-in-channel" method—where channels are routed out of the raw wood core and filled with a liquid resin before the final core profiling and press—they shift from thermoplastics to thermosetting liquid polyurethanes.The Type of Polyurethane Used
They use Semi-Rigid Polyurethane Casting Resins (specifically, Shore D hardness formulas).Unlike rigid polyurethanes (which are too brittle and crack under the intense flexing of a ski) or flexible polyurethanes (which are too soft to support an edge), semi-rigid formulas provide the perfect balance of flexibility, dampening, and rock-hard impact resistance.
Industry Favorites & Technical Specs:
•Smooth-On Smooth-Cast 65D / 66D: This is widely considered the gold standard for both custom commercial brands and DIY builders.•Shore Hardness: They typically target a Shore 65D to 70D hardness. This provides enough density to prevent the steel edges from compressing into the core during impacts while allowing the ski to flex naturally.
•Key Characteristics: These resins have low viscosity (making them easy to pour smoothly into narrow wood channels with minimal air bubbles) and cure quickly. They also bond mechanically well to the wood grain (especially if the wood is sealed first) and seamlessly fuse with standard structural epoxy during the final heated pressing cycle.
***Pro Tip for Poured Sidewalls: Because liquid urethanes are incredibly moisture-sensitive, builders always dry and seal the wood core channels (often with a light coat of resin or epoxy) prior to pouring to prevent the moisture in the wood from causing the polyurethane to foam up and form unwanted micro-bubbles.
What type of sidewall do you use in your construction and why?
When building skis or snowboards, the choice of sidewall material heavily impacts the durability, impact resistance, and torsional stiffness of the final product.
1. Traditional Sidewall Materials (Pre-fabricated)
For standard sandwich or semi-cap constructions where pre-made strips are bonded to the wood core, manufacturers typically use dense, highly durable plastics:
•ABS (Acrylonitrile Butadiene Styrene): The industry standard for high-performance skis and boards. ABS is a thermoplastic known for its excellent impact resistance, ability to withstand freezing temperatures without cracking, and high torsional rigidity (which translates to better edge grip on hard snow).
•UHMW-PE (Ultra-High-Molecular-Weight Polyethylene): Tougher and more impact-resistant than ABS, UHMW-PE is often used in park, freeride, or custom skis. It absorbs heavy impacts (like hitting rocks or rails) exceptionally well without compressing, though it requires specialized surface preparation (like flame treatment or sanding) to bond properly with epoxy.
2. Liquid Poured Sidewall Materials
When companies or DIY builders use the "pour-in-channel" method—where channels are routed out of the raw wood core and filled with a liquid resin before the final core profiling and press—they shift from thermoplastics to thermosetting liquid polyurethanes.
The Type of Polyurethane Used
They use Semi-Rigid Polyurethane Casting Resins (specifically, Shore D hardness formulas).
Unlike rigid polyurethanes (which are too brittle and crack under the intense flexing of a ski) or flexible polyurethanes (which are too soft to support an edge), semi-rigid formulas provide the perfect balance of flexibility, dampening, and rock-hard impact resistance.
Industry Favorites & Technical Specs:
•Smooth-On Smooth-Cast 65D / 66D: This is widely considered the gold standard for both custom commercial brands and DIY builders.
•Shore Hardness: They typically target a Shore 65D to 70D hardness. This provides enough density to prevent the steel edges from compressing into the core during impacts while allowing the ski to flex naturally.
•Key Characteristics: These resins have low viscosity (making them easy to pour smoothly into narrow wood channels with minimal air bubbles) and cure quickly. They also bond mechanically well to the wood grain (especially if the wood is sealed first) and seamlessly fuse with standard structural epoxy during the final heated pressing cycle.
***Pro Tip for Poured Sidewalls: Because liquid urethanes are incredibly moisture-sensitive, builders always dry and seal the wood core channels (often with a light coat of resin or epoxy) prior to pouring to prevent the moisture in the wood from causing the polyurethane to foam up and form unwanted micro-bubbles.