Skateboard Design: Concave Style
Note: at the time of this article, there is not a clear industry standard for skateboard dimensions. This article presents the “SK8CAD” Standard; please note that other manufacturers and distributors may use alternative definitions than those presented here.
“Concave” refers to the curvature of the board between the kicks of the board. There are different types of concave a board can have, including radial, tub, elliptical, progressive, and “W”. Or, it can have no concave at all and simply be flat.
The concave style of a board can be seen by looking at a cross section of the board. The simplest style of concave is radial, which has the shape of a circular arc. This provides a smooth, continuous-feeling concave. Radial concave is useful for boards where a more comfortable ride is desired, as it feels a bit more mellow than the other styles. Elliptical concave is very similar to radial, but with the shape of an elliptical, instead of circular, arc (so it is flatter in the middle and steeper at the edges). Since radial and elliptical concaves don't have a flat section in the middle, your trucks won't mount perfectly flush unless you also use a soft riser/shock pad or specifically carve out a flat area. In my experience skating radial concave boards, this has had no clear impact on the performance of my board and is typically barely aesthetically noticeable, since the curvature is often very subtle.
Tub concave has a flat section in the middle and folds up on the sides. This type of concave can feel more distinctive, which may be better suited for boards where steeper concave is desired. Tub concave will help your foot feel a little more locked in than radial. Tub concave is defined by a few more specs than radial, which can give you more design freedom (but can also be a little less clear to understand - I'll cover those specs in a later article). Progressive concave is similar to tub, except the folds are continuously curved (whereas tub typically curves until it reaches a specific angle). And “W” concave is also similar, except the flat section in the middle is replaced by a convex curve.
Going with either a radial or tub concave style can serve you well, as the style doesn’t matter as much as the actual specifications that define the style. However, if you’d really like some guidance and you are designing your own board, choose a tub concave to start, since it will allow for the greatest customization.
Typical concave styles:
Street decks: Tub/progressive
Transition decks: Tub/progressive
Longboards: Tub/progressive, radial/elliptical, flat, "W"
Surf Skates: Tub/progressive
Cruisers: Tub/progressive, flat, radial/elliptical
Freestyle: Tub/progressive, flat, radial/elliptical
Recommended ranges for goals:
Maneuverability (flip tricks, pivoting, quick movements): Tub/progressive
Stability: Tub/progressive, radial/elliptical
Dancing: Tub/progressive, radial/elliptical, flat
Speed: Tub/progressive, "W", radial/elliptical
Start designing: https://sk8cad.com