Jeff Morris wrote:
This certainly applies in open water, but in very protected water, such as
Boston's Charles River Basin, you won't see whitecaps until its over 15 knots.
Of course, we were able to sail dinghies in 30 knots or more there.

That's what, about 1/2 mile wide and between tall buildings? I think
that you get little popcorn whitecaps at 12 knots steady breeze even then.

I've noticed that on water with more than a mile fetch, some whitecaps
show up at 8 knots (if it's fairly consistent) because that's when the
Johnson 18 will start planing. Takes a tight spinnaker reach, but it'll
do it.

Fresh Breezes- Doug King