This type of vessel has two masts, each made of two spars. Both wings buckled rear to the front and failures occurred in stringers, spars and ribs. They have two outrigger floats connected to spars lashed across a single hull. The point stuck in sails, hulls or spars and set fire to the enemy ship. Most designs steer with small moving sails on the ends of the spars. The wings were built around five tubular girder spars covered with a smooth stressed skin. The strut-braced wings, likewise, are constructed of exterior skin sheets riveted to spars and ribs. The wing features aluminum tube spars and ribs. "Guys" are used to control the ends of other spars such as spinnaker poles. The stress bearing skin was riveted to spars and ribs. Wing spars and ribs are also made out of carbon composites. The carbon-fiber main wing spars possesses exceptional crashworthiness. It was simply a wood lantern with glass windows hoisted between two spars. The first truss spars were Kerr-McGee's Boomvang and Nansen. Most Citabrias were built with wooden spars.