Abstract: The mainstay rig is an improved standing rig system for wind-powered vehicles that travel on water, snow, ice, land, or rail. Mainstay rig uses a mast at a rake and uses a vertical mainstay to support mainsail luff, which gives less disturbance of airflow at mainsail luff and greater driving force. Mainstay rig can use jib-furling mechanisms for mainsail furling. Mainstay rig eliminates backstay and gives a greater choice of mainsail shape which allows more efficient energy extraction from wind because sails can be shaped with larger roach or be shaped closer to an ideal elliptical shape. Additionally, mainstay rig can use one shroud, which reduces windage.