▁additional ▁lines ▁are ▁used ▁to ▁pull ▁down ▁the ▁lower ▁sp ar ▁and ▁provide ▁t ension ▁along ▁the ▁upper ▁and ▁lower ▁sp ars , ▁providing ▁greater ▁control ▁over ▁the ▁sail ▁shape . ▁ ▁Since ▁the ▁upper ▁and ▁lower ▁sp ars ▁provide ▁a ▁frame ▁for ▁the ▁sail , ▁the ▁cam ber ▁of ▁the ▁sail ▁is ▁simply ▁a ▁function ▁of ▁how ▁tight ly ▁the ▁sp ars ▁stretch ▁the ▁sail . ▁ ▁This ▁means ▁that ▁late en ▁s ails ▁are ▁often ▁cut ▁flat , ▁without ▁the ▁complex ▁cutting ▁and ▁st itch ing ▁required ▁to ▁provide ▁cam ber ▁in ▁B erm uda ▁rig ▁s ails . ▁ ▁Cur ved ▁edges , ▁when ▁m ated ▁with ▁the ▁straight ▁sp ars , ▁provide ▁all ▁or ▁nearly ▁all ▁of ▁the ▁sail ▁curv ature ▁needed . ▁ ▁See ▁also ▁▁ ▁C rab ▁cla w ▁sail ▁ ▁Tan ja ▁sail , ▁a ▁type ▁of ▁sail ▁sometimes ▁mistaken ▁as ▁late en ▁sail . ▁ ▁S ette e ▁( a ▁tri angular ▁sail ▁with ▁the ▁front ▁corner ▁cut ▁off ) ▁ ▁Notes ▁ ▁S ources ▁ ▁Further ▁reading ▁ ▁External ▁links ▁▁▁ ▁The ▁ship ' s ▁development ▁during ▁the ▁Middle ▁A ges , ▁see ▁bottom ▁of ▁page ▁for ▁English ▁translation ▁ ▁Poly S ail ▁International ▁instructions ▁for ▁building ▁a ▁Sun fish - like ▁late en ▁sail ▁ ▁I . ▁C . ▁Campbell , ▁" The ▁Late en ▁S ail ▁in ▁World ▁History ", ▁Journal ▁of ▁World ▁History ▁( Univers ity ▁of ▁Hawai i ), ▁ 6 . 1 ▁( Spring ▁ 1 9 9 5