top rigging 30 respectively the lighter than air spinnaker 10 is held aloft by inflatable bags indicated schematically at 32 in fig1 attached to the exterior surface of the spinnaker one embodiment of the lighter than air spinnaker of the present invention is illustrated in fig2 and 3 the triangular shaped spinnaker includes a piece of flexible sail fabric 34 having a top end 36 a bottom end 38 two sides 40 and exterior and interior surfaces 42 and 44 respectively in the embodiment of fig2 and 3 the inflatable bags 32 are generally tubular in construction and are attached to the exterior surface 42 so that the sides of the bags are parallel to the top end 36 and the bottom end 38 of the sail fabric 34 preferably the bags attached near the top end of the fabric are wider than those attached near the bottom end of the fabric this gives greater buoyancy to the upper part of the sail and tends to maintain the sail in an upright top up position the bags 32 may contain any suitable lighter than air gas such as hydrogen helium heated air or mixtures thereof the interiors of the bags 32 are preferably interconnected by connecting tubes 46 or the like for the purpose of equalizing the pressure in all of the bags loops 48 50 52 are provided for attachment of the sail to the top rigging 30 port rigging 28 and starboard rigging 26 respectively in an alternate embodiment of the lighter than air spinnaker shown in fig4 and 5 tubular inflatable bags 132a 132b 132c 132d and 132e are attached to the five sides 140a 140b 140c 140d 140e respectively of pentagonal sail fabric 134 as in the.