Sweep rowing

[2] In the other rowing discipline, sculling, each rower holds two oars, one in each hand.

Sweep or single oar rowing has a long history and was the means of propulsion for Greek triremes and Viking longboats.

The hulls can be kept narrower by attaching riggers to the gunwales, so that the oarlocks can be placed farther out to carry longer oars.

This means a sweep oared racing shell has to be stiffer in order to handle the unmatched forces, and so requires more bracing, which means it has to be heavier and slower than an equivalent sculling boat.

In a sculling boat the oars and riggers apply forces symmetrically to the shell.