Thanks everyone! Lots of good thoughts here. I think there may be something in just about all of the posts that are valid, but I do believe is may have been a combination of a sagging luff, because it was not tight enough, and the angle of the sheet on the leech, because the jib was too far forward.

Both of these suggestions make the most sense to me, in that if the luff was loose and the jib a little too far forward, there would not be a tight luff (bad laminar airflow) and not the appropriate/maximal leverage on the clew from the sheet (because the angle of the clew is l ess than ~90 degrees at the attachement point of the self-tacker. Both of those things probably led to some inefficiency of the jib. Now, to figure out the best height! Will start with getting it as low as possible to the deck, with out adversely moving the clew forward, such that maximal force can be applied to the clew from the sheet. And, BTW, it is a new sail (new boat), so the leach had better be alright!.

Thanks again