Flat-bottom hulls come in two broad varieties: displacement and planing.

• Displacement hulls tend to be long and narrow, designed for water to go around the hull. These tend to be faster in flat water.
• Planing hulls tend to be short and fat, design for water to go under the hull. They often have a rocker which makes it easier to get on top of waves. These tend to be faster in downwind conditions.

SUPs are measured by length and width. For example, a SUP can be 12’ x 24”, which means it’s 12’ long and 24” at its widest point. Most SUPs races are limited in length to 14’, so this is an effective upper bound for hull length.

The theory behind planing vs. displacement hulls is that a planing hull is slower at low speeds but once it starts to plane at higher speeds, it lifts out of the water and reduces the wetted surface, lowering friction and allowing higher top speeds.