Langley to Oak Harbor - 21 miles. We don't have a report from anyone about doing this long of a
Saratoga Passage downwinder. It could get somewhat exposed in the open water between Whidbey and Camano Islands well away from shore or you can take less of a direct line staying closer to the Whidbey shore along the way which would increase the trip length by about 1 mile. But in the right conditions (SE wind for one), might be a longer than usual worthwhile downwinder.