You can paddle. On wind speed 1 in the raft and wind speed 1 and 2 in the Karve paddling is faster than tacking. Its always faster to tack than paddle in a long boat. The wind is statistically only against you 25% of the time because the foul winds section is 90 degrees and 80 % of the time in the karve (and 100% of the time in the long boat) the wind speed is going to be high enough that tacking is still going to be much faster than any other form of travel available to you except for portalling and you'll still have to sail there the first time to build a portal.

When the wind is fair and the wind speed is high you'll zip from island to island and that occurs far more often than foul, slow winds.

The devs didn't model trade winds but that makes sense since they didn't model seasons either.