Skateboard Design: Concave Drop
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 drop” describes how much concave a skateboard has. More specifically, concave drop is the vertical difference in height between the side of the board (called the rail) and the center of the board. Note that in SK8CAD, this is measured before the rails are rounded over; when the rails are rounded over (with a trim router and roundover bit or simply by sanding), the overall concave drop is reduced. To compensate for this, it is recommended that you add ~0.05" to 0.1" to the concave drop in SK8CAD to achieve your desired concave.
Concave drop measurement. Green shows concave drop before rounding rails of board (measurement in SK8CAD). Blue shoes concave drop after rounding rails of board.
Concave drop alone isn’t very useful of a specification until we include the width of the board as well. (Of course, many boards fall within a small range of widths, so chances are that describing a concave drop without a width will give most skaters a good idea of the feel.) For example, 0.5” of concave drop across a 7” board will feel much steeper than 0.5” of concave drop across an 11” board. Keep this in mind when you design your boards; if you make a skateboard mold with 0.5" of drop across a 7" deck, an 8" board will have more than 0.5" of drop, while, if you make a skateboard mold with 0.5" of drop across a 10" deck, an 8" board will have less than 0.5" of drop.
Comparison of same concave drop across two boards with different widths.
The more concave you have, the steeper the board will feel and more leverage you’ll have for tricks and securing your feet on the board. More concave also adds a bit of stability when in a rail stand, since it widens the points of contact your board makes with the ground. More concave also helps lessen the risk of wheel bite, which is when your wheel hits the bottom of your deck when turning, which can cause you to stop short.
Less concave provides a mellower feel, which may feel more comfortable to some skaters. Also, concave makes a board stiffer, so by reducing it, you can create a board with more flex in the middle, which provides a more comfortable ride.
Typical concave drops:
Street decks: 0.3"-0.5"
Transition decks: 0.3"-0.5"
Surf Skates: 0.1"-0.4"
Recommended ranges for goals:
Maneuverability (flip tricks, pivoting, quick movements): 0.4"-0.5"
Start designing: https://sk8cad.com