As I walked to the beach yesterday evening, it occurred to me that there is an easy way to shorten an unlined jacket's sleeve to 3/4 length.  Be sure the sleeve is cut straight down from the elbow so the width is even from there to the hem.  Finish the hem edge, then turn it up 4-5" and finish as you would a hem.  This gives you a 3/4 sleeve that can be shortened further by turning up a 3-4" cuff.