A sail tacked down behind the foremost mast is not a headsail.
So, every older Nacra, SuperCat, etc. with the old style overlapping jib tacked to the tramp or on a crosswire does not really have a jib at all? It's a screacher? <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />
If it's not on a sprit I've always used the historically correct sailing term "big butt jib" for those sails.
